1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the implementation of the scalar evolution analysis
11 // engine, which is used primarily to analyze expressions involving induction
12 // variables in loops.
14 // There are several aspects to this library. First is the representation of
15 // scalar expressions, which are represented as subclasses of the SCEV class.
16 // These classes are used to represent certain types of subexpressions that we
17 // can handle. We only create one SCEV of a particular shape, so
18 // pointer-comparisons for equality are legal.
20 // One important aspect of the SCEV objects is that they are never cyclic, even
21 // if there is a cycle in the dataflow for an expression (ie, a PHI node). If
22 // the PHI node is one of the idioms that we can represent (e.g., a polynomial
23 // recurrence) then we represent it directly as a recurrence node, otherwise we
24 // represent it as a SCEVUnknown node.
26 // In addition to being able to represent expressions of various types, we also
27 // have folders that are used to build the *canonical* representation for a
28 // particular expression. These folders are capable of using a variety of
29 // rewrite rules to simplify the expressions.
31 // Once the folders are defined, we can implement the more interesting
32 // higher-level code, such as the code that recognizes PHI nodes of various
33 // types, computes the execution count of a loop, etc.
35 // TODO: We should use these routines and value representations to implement
36 // dependence analysis!
38 //===----------------------------------------------------------------------===//
40 // There are several good references for the techniques used in this analysis.
42 // Chains of recurrences -- a method to expedite the evaluation
43 // of closed-form functions
44 // Olaf Bachmann, Paul S. Wang, Eugene V. Zima
46 // On computational properties of chains of recurrences
49 // Symbolic Evaluation of Chains of Recurrences for Loop Optimization
50 // Robert A. van Engelen
52 // Efficient Symbolic Analysis for Optimizing Compilers
53 // Robert A. van Engelen
55 // Using the chains of recurrences algebra for data dependence testing and
56 // induction variable substitution
57 // MS Thesis, Johnie Birch
59 //===----------------------------------------------------------------------===//
61 #include "llvm/Analysis/ScalarEvolution.h"
62 #include "llvm/ADT/Optional.h"
63 #include "llvm/ADT/STLExtras.h"
64 #include "llvm/ADT/SmallPtrSet.h"
65 #include "llvm/ADT/Statistic.h"
66 #include "llvm/Analysis/AssumptionCache.h"
67 #include "llvm/Analysis/ConstantFolding.h"
68 #include "llvm/Analysis/InstructionSimplify.h"
69 #include "llvm/Analysis/LoopInfo.h"
70 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
71 #include "llvm/Analysis/TargetLibraryInfo.h"
72 #include "llvm/Analysis/ValueTracking.h"
73 #include "llvm/IR/ConstantRange.h"
74 #include "llvm/IR/Constants.h"
75 #include "llvm/IR/DataLayout.h"
76 #include "llvm/IR/DerivedTypes.h"
77 #include "llvm/IR/Dominators.h"
78 #include "llvm/IR/GetElementPtrTypeIterator.h"
79 #include "llvm/IR/GlobalAlias.h"
80 #include "llvm/IR/GlobalVariable.h"
81 #include "llvm/IR/InstIterator.h"
82 #include "llvm/IR/Instructions.h"
83 #include "llvm/IR/LLVMContext.h"
84 #include "llvm/IR/Metadata.h"
85 #include "llvm/IR/Operator.h"
86 #include "llvm/IR/PatternMatch.h"
87 #include "llvm/Support/CommandLine.h"
88 #include "llvm/Support/Debug.h"
89 #include "llvm/Support/ErrorHandling.h"
90 #include "llvm/Support/MathExtras.h"
91 #include "llvm/Support/raw_ostream.h"
92 #include "llvm/Support/SaveAndRestore.h"
96 #define DEBUG_TYPE "scalar-evolution"
98 STATISTIC(NumArrayLenItCounts,
99 "Number of trip counts computed with array length");
100 STATISTIC(NumTripCountsComputed,
101 "Number of loops with predictable loop counts");
102 STATISTIC(NumTripCountsNotComputed,
103 "Number of loops without predictable loop counts");
104 STATISTIC(NumBruteForceTripCountsComputed,
105 "Number of loops with trip counts computed by force");
107 static cl::opt<unsigned>
108 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
109 cl::desc("Maximum number of iterations SCEV will "
110 "symbolically execute a constant "
114 // FIXME: Enable this with XDEBUG when the test suite is clean.
116 VerifySCEV("verify-scev",
117 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
119 //===----------------------------------------------------------------------===//
120 // SCEV class definitions
121 //===----------------------------------------------------------------------===//
123 //===----------------------------------------------------------------------===//
124 // Implementation of the SCEV class.
128 void SCEV::dump() const {
133 void SCEV::print(raw_ostream &OS) const {
134 switch (static_cast<SCEVTypes>(getSCEVType())) {
136 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
139 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
140 const SCEV *Op = Trunc->getOperand();
141 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
142 << *Trunc->getType() << ")";
146 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
147 const SCEV *Op = ZExt->getOperand();
148 OS << "(zext " << *Op->getType() << " " << *Op << " to "
149 << *ZExt->getType() << ")";
153 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
154 const SCEV *Op = SExt->getOperand();
155 OS << "(sext " << *Op->getType() << " " << *Op << " to "
156 << *SExt->getType() << ")";
160 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
161 OS << "{" << *AR->getOperand(0);
162 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
163 OS << ",+," << *AR->getOperand(i);
165 if (AR->getNoWrapFlags(FlagNUW))
167 if (AR->getNoWrapFlags(FlagNSW))
169 if (AR->getNoWrapFlags(FlagNW) &&
170 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
172 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
180 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
181 const char *OpStr = nullptr;
182 switch (NAry->getSCEVType()) {
183 case scAddExpr: OpStr = " + "; break;
184 case scMulExpr: OpStr = " * "; break;
185 case scUMaxExpr: OpStr = " umax "; break;
186 case scSMaxExpr: OpStr = " smax "; break;
189 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
192 if (std::next(I) != E)
196 switch (NAry->getSCEVType()) {
199 if (NAry->getNoWrapFlags(FlagNUW))
201 if (NAry->getNoWrapFlags(FlagNSW))
207 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
208 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
212 const SCEVUnknown *U = cast<SCEVUnknown>(this);
214 if (U->isSizeOf(AllocTy)) {
215 OS << "sizeof(" << *AllocTy << ")";
218 if (U->isAlignOf(AllocTy)) {
219 OS << "alignof(" << *AllocTy << ")";
225 if (U->isOffsetOf(CTy, FieldNo)) {
226 OS << "offsetof(" << *CTy << ", ";
227 FieldNo->printAsOperand(OS, false);
232 // Otherwise just print it normally.
233 U->getValue()->printAsOperand(OS, false);
236 case scCouldNotCompute:
237 OS << "***COULDNOTCOMPUTE***";
240 llvm_unreachable("Unknown SCEV kind!");
243 Type *SCEV::getType() const {
244 switch (static_cast<SCEVTypes>(getSCEVType())) {
246 return cast<SCEVConstant>(this)->getType();
250 return cast<SCEVCastExpr>(this)->getType();
255 return cast<SCEVNAryExpr>(this)->getType();
257 return cast<SCEVAddExpr>(this)->getType();
259 return cast<SCEVUDivExpr>(this)->getType();
261 return cast<SCEVUnknown>(this)->getType();
262 case scCouldNotCompute:
263 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
265 llvm_unreachable("Unknown SCEV kind!");
268 bool SCEV::isZero() const {
269 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
270 return SC->getValue()->isZero();
274 bool SCEV::isOne() const {
275 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
276 return SC->getValue()->isOne();
280 bool SCEV::isAllOnesValue() const {
281 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
282 return SC->getValue()->isAllOnesValue();
286 /// isNonConstantNegative - Return true if the specified scev is negated, but
288 bool SCEV::isNonConstantNegative() const {
289 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
290 if (!Mul) return false;
292 // If there is a constant factor, it will be first.
293 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
294 if (!SC) return false;
296 // Return true if the value is negative, this matches things like (-42 * V).
297 return SC->getValue()->getValue().isNegative();
300 SCEVCouldNotCompute::SCEVCouldNotCompute() :
301 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
303 bool SCEVCouldNotCompute::classof(const SCEV *S) {
304 return S->getSCEVType() == scCouldNotCompute;
307 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
309 ID.AddInteger(scConstant);
312 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
313 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
314 UniqueSCEVs.InsertNode(S, IP);
318 const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
319 return getConstant(ConstantInt::get(getContext(), Val));
323 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
324 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
325 return getConstant(ConstantInt::get(ITy, V, isSigned));
328 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
329 unsigned SCEVTy, const SCEV *op, Type *ty)
330 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
332 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
333 const SCEV *op, Type *ty)
334 : SCEVCastExpr(ID, scTruncate, op, ty) {
335 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
336 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
337 "Cannot truncate non-integer value!");
340 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
341 const SCEV *op, Type *ty)
342 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
343 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
344 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
345 "Cannot zero extend non-integer value!");
348 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
349 const SCEV *op, Type *ty)
350 : SCEVCastExpr(ID, scSignExtend, op, ty) {
351 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
352 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
353 "Cannot sign extend non-integer value!");
356 void SCEVUnknown::deleted() {
357 // Clear this SCEVUnknown from various maps.
358 SE->forgetMemoizedResults(this);
360 // Remove this SCEVUnknown from the uniquing map.
361 SE->UniqueSCEVs.RemoveNode(this);
363 // Release the value.
367 void SCEVUnknown::allUsesReplacedWith(Value *New) {
368 // Clear this SCEVUnknown from various maps.
369 SE->forgetMemoizedResults(this);
371 // Remove this SCEVUnknown from the uniquing map.
372 SE->UniqueSCEVs.RemoveNode(this);
374 // Update this SCEVUnknown to point to the new value. This is needed
375 // because there may still be outstanding SCEVs which still point to
380 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
381 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
382 if (VCE->getOpcode() == Instruction::PtrToInt)
383 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
384 if (CE->getOpcode() == Instruction::GetElementPtr &&
385 CE->getOperand(0)->isNullValue() &&
386 CE->getNumOperands() == 2)
387 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
389 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
397 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
398 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
399 if (VCE->getOpcode() == Instruction::PtrToInt)
400 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
401 if (CE->getOpcode() == Instruction::GetElementPtr &&
402 CE->getOperand(0)->isNullValue()) {
404 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
405 if (StructType *STy = dyn_cast<StructType>(Ty))
406 if (!STy->isPacked() &&
407 CE->getNumOperands() == 3 &&
408 CE->getOperand(1)->isNullValue()) {
409 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
411 STy->getNumElements() == 2 &&
412 STy->getElementType(0)->isIntegerTy(1)) {
413 AllocTy = STy->getElementType(1);
422 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
423 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
424 if (VCE->getOpcode() == Instruction::PtrToInt)
425 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
426 if (CE->getOpcode() == Instruction::GetElementPtr &&
427 CE->getNumOperands() == 3 &&
428 CE->getOperand(0)->isNullValue() &&
429 CE->getOperand(1)->isNullValue()) {
431 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
432 // Ignore vector types here so that ScalarEvolutionExpander doesn't
433 // emit getelementptrs that index into vectors.
434 if (Ty->isStructTy() || Ty->isArrayTy()) {
436 FieldNo = CE->getOperand(2);
444 //===----------------------------------------------------------------------===//
446 //===----------------------------------------------------------------------===//
449 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
450 /// than the complexity of the RHS. This comparator is used to canonicalize
452 class SCEVComplexityCompare {
453 const LoopInfo *const LI;
455 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
457 // Return true or false if LHS is less than, or at least RHS, respectively.
458 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
459 return compare(LHS, RHS) < 0;
462 // Return negative, zero, or positive, if LHS is less than, equal to, or
463 // greater than RHS, respectively. A three-way result allows recursive
464 // comparisons to be more efficient.
465 int compare(const SCEV *LHS, const SCEV *RHS) const {
466 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
470 // Primarily, sort the SCEVs by their getSCEVType().
471 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
473 return (int)LType - (int)RType;
475 // Aside from the getSCEVType() ordering, the particular ordering
476 // isn't very important except that it's beneficial to be consistent,
477 // so that (a + b) and (b + a) don't end up as different expressions.
478 switch (static_cast<SCEVTypes>(LType)) {
480 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
481 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
483 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
484 // not as complete as it could be.
485 const Value *LV = LU->getValue(), *RV = RU->getValue();
487 // Order pointer values after integer values. This helps SCEVExpander
489 bool LIsPointer = LV->getType()->isPointerTy(),
490 RIsPointer = RV->getType()->isPointerTy();
491 if (LIsPointer != RIsPointer)
492 return (int)LIsPointer - (int)RIsPointer;
494 // Compare getValueID values.
495 unsigned LID = LV->getValueID(),
496 RID = RV->getValueID();
498 return (int)LID - (int)RID;
500 // Sort arguments by their position.
501 if (const Argument *LA = dyn_cast<Argument>(LV)) {
502 const Argument *RA = cast<Argument>(RV);
503 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
504 return (int)LArgNo - (int)RArgNo;
507 // For instructions, compare their loop depth, and their operand
508 // count. This is pretty loose.
509 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
510 const Instruction *RInst = cast<Instruction>(RV);
512 // Compare loop depths.
513 const BasicBlock *LParent = LInst->getParent(),
514 *RParent = RInst->getParent();
515 if (LParent != RParent) {
516 unsigned LDepth = LI->getLoopDepth(LParent),
517 RDepth = LI->getLoopDepth(RParent);
518 if (LDepth != RDepth)
519 return (int)LDepth - (int)RDepth;
522 // Compare the number of operands.
523 unsigned LNumOps = LInst->getNumOperands(),
524 RNumOps = RInst->getNumOperands();
525 return (int)LNumOps - (int)RNumOps;
532 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
533 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
535 // Compare constant values.
536 const APInt &LA = LC->getValue()->getValue();
537 const APInt &RA = RC->getValue()->getValue();
538 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
539 if (LBitWidth != RBitWidth)
540 return (int)LBitWidth - (int)RBitWidth;
541 return LA.ult(RA) ? -1 : 1;
545 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
546 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
548 // Compare addrec loop depths.
549 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
550 if (LLoop != RLoop) {
551 unsigned LDepth = LLoop->getLoopDepth(),
552 RDepth = RLoop->getLoopDepth();
553 if (LDepth != RDepth)
554 return (int)LDepth - (int)RDepth;
557 // Addrec complexity grows with operand count.
558 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
559 if (LNumOps != RNumOps)
560 return (int)LNumOps - (int)RNumOps;
562 // Lexicographically compare.
563 for (unsigned i = 0; i != LNumOps; ++i) {
564 long X = compare(LA->getOperand(i), RA->getOperand(i));
576 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
577 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
579 // Lexicographically compare n-ary expressions.
580 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
581 if (LNumOps != RNumOps)
582 return (int)LNumOps - (int)RNumOps;
584 for (unsigned i = 0; i != LNumOps; ++i) {
587 long X = compare(LC->getOperand(i), RC->getOperand(i));
591 return (int)LNumOps - (int)RNumOps;
595 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
596 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
598 // Lexicographically compare udiv expressions.
599 long X = compare(LC->getLHS(), RC->getLHS());
602 return compare(LC->getRHS(), RC->getRHS());
608 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
609 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
611 // Compare cast expressions by operand.
612 return compare(LC->getOperand(), RC->getOperand());
615 case scCouldNotCompute:
616 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
618 llvm_unreachable("Unknown SCEV kind!");
623 /// GroupByComplexity - Given a list of SCEV objects, order them by their
624 /// complexity, and group objects of the same complexity together by value.
625 /// When this routine is finished, we know that any duplicates in the vector are
626 /// consecutive and that complexity is monotonically increasing.
628 /// Note that we go take special precautions to ensure that we get deterministic
629 /// results from this routine. In other words, we don't want the results of
630 /// this to depend on where the addresses of various SCEV objects happened to
633 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
635 if (Ops.size() < 2) return; // Noop
636 if (Ops.size() == 2) {
637 // This is the common case, which also happens to be trivially simple.
639 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
640 if (SCEVComplexityCompare(LI)(RHS, LHS))
645 // Do the rough sort by complexity.
646 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
648 // Now that we are sorted by complexity, group elements of the same
649 // complexity. Note that this is, at worst, N^2, but the vector is likely to
650 // be extremely short in practice. Note that we take this approach because we
651 // do not want to depend on the addresses of the objects we are grouping.
652 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
653 const SCEV *S = Ops[i];
654 unsigned Complexity = S->getSCEVType();
656 // If there are any objects of the same complexity and same value as this
658 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
659 if (Ops[j] == S) { // Found a duplicate.
660 // Move it to immediately after i'th element.
661 std::swap(Ops[i+1], Ops[j]);
662 ++i; // no need to rescan it.
663 if (i == e-2) return; // Done!
670 struct FindSCEVSize {
672 FindSCEVSize() : Size(0) {}
674 bool follow(const SCEV *S) {
676 // Keep looking at all operands of S.
679 bool isDone() const {
685 // Returns the size of the SCEV S.
686 static inline int sizeOfSCEV(const SCEV *S) {
688 SCEVTraversal<FindSCEVSize> ST(F);
695 struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
697 // Computes the Quotient and Remainder of the division of Numerator by
699 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
700 const SCEV *Denominator, const SCEV **Quotient,
701 const SCEV **Remainder) {
702 assert(Numerator && Denominator && "Uninitialized SCEV");
704 SCEVDivision D(SE, Numerator, Denominator);
706 // Check for the trivial case here to avoid having to check for it in the
708 if (Numerator == Denominator) {
714 if (Numerator->isZero()) {
720 // A simple case when N/1. The quotient is N.
721 if (Denominator->isOne()) {
722 *Quotient = Numerator;
727 // Split the Denominator when it is a product.
728 if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
730 *Quotient = Numerator;
731 for (const SCEV *Op : T->operands()) {
732 divide(SE, *Quotient, Op, &Q, &R);
735 // Bail out when the Numerator is not divisible by one of the terms of
739 *Remainder = Numerator;
748 *Quotient = D.Quotient;
749 *Remainder = D.Remainder;
752 // Except in the trivial case described above, we do not know how to divide
753 // Expr by Denominator for the following functions with empty implementation.
754 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
755 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
756 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
757 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
758 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
759 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
760 void visitUnknown(const SCEVUnknown *Numerator) {}
761 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
763 void visitConstant(const SCEVConstant *Numerator) {
764 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
765 APInt NumeratorVal = Numerator->getValue()->getValue();
766 APInt DenominatorVal = D->getValue()->getValue();
767 uint32_t NumeratorBW = NumeratorVal.getBitWidth();
768 uint32_t DenominatorBW = DenominatorVal.getBitWidth();
770 if (NumeratorBW > DenominatorBW)
771 DenominatorVal = DenominatorVal.sext(NumeratorBW);
772 else if (NumeratorBW < DenominatorBW)
773 NumeratorVal = NumeratorVal.sext(DenominatorBW);
775 APInt QuotientVal(NumeratorVal.getBitWidth(), 0);
776 APInt RemainderVal(NumeratorVal.getBitWidth(), 0);
777 APInt::sdivrem(NumeratorVal, DenominatorVal, QuotientVal, RemainderVal);
778 Quotient = SE.getConstant(QuotientVal);
779 Remainder = SE.getConstant(RemainderVal);
784 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
785 const SCEV *StartQ, *StartR, *StepQ, *StepR;
786 if (!Numerator->isAffine())
787 return cannotDivide(Numerator);
788 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
789 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
790 // Bail out if the types do not match.
791 Type *Ty = Denominator->getType();
792 if (Ty != StartQ->getType() || Ty != StartR->getType() ||
793 Ty != StepQ->getType() || Ty != StepR->getType())
794 return cannotDivide(Numerator);
795 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
796 Numerator->getNoWrapFlags());
797 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
798 Numerator->getNoWrapFlags());
801 void visitAddExpr(const SCEVAddExpr *Numerator) {
802 SmallVector<const SCEV *, 2> Qs, Rs;
803 Type *Ty = Denominator->getType();
805 for (const SCEV *Op : Numerator->operands()) {
807 divide(SE, Op, Denominator, &Q, &R);
809 // Bail out if types do not match.
810 if (Ty != Q->getType() || Ty != R->getType())
811 return cannotDivide(Numerator);
817 if (Qs.size() == 1) {
823 Quotient = SE.getAddExpr(Qs);
824 Remainder = SE.getAddExpr(Rs);
827 void visitMulExpr(const SCEVMulExpr *Numerator) {
828 SmallVector<const SCEV *, 2> Qs;
829 Type *Ty = Denominator->getType();
831 bool FoundDenominatorTerm = false;
832 for (const SCEV *Op : Numerator->operands()) {
833 // Bail out if types do not match.
834 if (Ty != Op->getType())
835 return cannotDivide(Numerator);
837 if (FoundDenominatorTerm) {
842 // Check whether Denominator divides one of the product operands.
844 divide(SE, Op, Denominator, &Q, &R);
850 // Bail out if types do not match.
851 if (Ty != Q->getType())
852 return cannotDivide(Numerator);
854 FoundDenominatorTerm = true;
858 if (FoundDenominatorTerm) {
863 Quotient = SE.getMulExpr(Qs);
867 if (!isa<SCEVUnknown>(Denominator))
868 return cannotDivide(Numerator);
870 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
871 ValueToValueMap RewriteMap;
872 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
873 cast<SCEVConstant>(Zero)->getValue();
874 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
876 if (Remainder->isZero()) {
877 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
878 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
879 cast<SCEVConstant>(One)->getValue();
881 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
885 // Quotient is (Numerator - Remainder) divided by Denominator.
887 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
888 // This SCEV does not seem to simplify: fail the division here.
889 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator))
890 return cannotDivide(Numerator);
891 divide(SE, Diff, Denominator, &Q, &R);
893 return cannotDivide(Numerator);
898 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator,
899 const SCEV *Denominator)
900 : SE(S), Denominator(Denominator) {
901 Zero = SE.getZero(Denominator->getType());
902 One = SE.getOne(Denominator->getType());
904 // We generally do not know how to divide Expr by Denominator. We
905 // initialize the division to a "cannot divide" state to simplify the rest
907 cannotDivide(Numerator);
910 // Convenience function for giving up on the division. We set the quotient to
911 // be equal to zero and the remainder to be equal to the numerator.
912 void cannotDivide(const SCEV *Numerator) {
914 Remainder = Numerator;
918 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
923 //===----------------------------------------------------------------------===//
924 // Simple SCEV method implementations
925 //===----------------------------------------------------------------------===//
927 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
929 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
932 // Handle the simplest case efficiently.
934 return SE.getTruncateOrZeroExtend(It, ResultTy);
936 // We are using the following formula for BC(It, K):
938 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
940 // Suppose, W is the bitwidth of the return value. We must be prepared for
941 // overflow. Hence, we must assure that the result of our computation is
942 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
943 // safe in modular arithmetic.
945 // However, this code doesn't use exactly that formula; the formula it uses
946 // is something like the following, where T is the number of factors of 2 in
947 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
950 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
952 // This formula is trivially equivalent to the previous formula. However,
953 // this formula can be implemented much more efficiently. The trick is that
954 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
955 // arithmetic. To do exact division in modular arithmetic, all we have
956 // to do is multiply by the inverse. Therefore, this step can be done at
959 // The next issue is how to safely do the division by 2^T. The way this
960 // is done is by doing the multiplication step at a width of at least W + T
961 // bits. This way, the bottom W+T bits of the product are accurate. Then,
962 // when we perform the division by 2^T (which is equivalent to a right shift
963 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
964 // truncated out after the division by 2^T.
966 // In comparison to just directly using the first formula, this technique
967 // is much more efficient; using the first formula requires W * K bits,
968 // but this formula less than W + K bits. Also, the first formula requires
969 // a division step, whereas this formula only requires multiplies and shifts.
971 // It doesn't matter whether the subtraction step is done in the calculation
972 // width or the input iteration count's width; if the subtraction overflows,
973 // the result must be zero anyway. We prefer here to do it in the width of
974 // the induction variable because it helps a lot for certain cases; CodeGen
975 // isn't smart enough to ignore the overflow, which leads to much less
976 // efficient code if the width of the subtraction is wider than the native
979 // (It's possible to not widen at all by pulling out factors of 2 before
980 // the multiplication; for example, K=2 can be calculated as
981 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
982 // extra arithmetic, so it's not an obvious win, and it gets
983 // much more complicated for K > 3.)
985 // Protection from insane SCEVs; this bound is conservative,
986 // but it probably doesn't matter.
988 return SE.getCouldNotCompute();
990 unsigned W = SE.getTypeSizeInBits(ResultTy);
992 // Calculate K! / 2^T and T; we divide out the factors of two before
993 // multiplying for calculating K! / 2^T to avoid overflow.
994 // Other overflow doesn't matter because we only care about the bottom
995 // W bits of the result.
996 APInt OddFactorial(W, 1);
998 for (unsigned i = 3; i <= K; ++i) {
1000 unsigned TwoFactors = Mult.countTrailingZeros();
1002 Mult = Mult.lshr(TwoFactors);
1003 OddFactorial *= Mult;
1006 // We need at least W + T bits for the multiplication step
1007 unsigned CalculationBits = W + T;
1009 // Calculate 2^T, at width T+W.
1010 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1012 // Calculate the multiplicative inverse of K! / 2^T;
1013 // this multiplication factor will perform the exact division by
1015 APInt Mod = APInt::getSignedMinValue(W+1);
1016 APInt MultiplyFactor = OddFactorial.zext(W+1);
1017 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1018 MultiplyFactor = MultiplyFactor.trunc(W);
1020 // Calculate the product, at width T+W
1021 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1023 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1024 for (unsigned i = 1; i != K; ++i) {
1025 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1026 Dividend = SE.getMulExpr(Dividend,
1027 SE.getTruncateOrZeroExtend(S, CalculationTy));
1031 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1033 // Truncate the result, and divide by K! / 2^T.
1035 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1036 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1039 /// evaluateAtIteration - Return the value of this chain of recurrences at
1040 /// the specified iteration number. We can evaluate this recurrence by
1041 /// multiplying each element in the chain by the binomial coefficient
1042 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
1044 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1046 /// where BC(It, k) stands for binomial coefficient.
1048 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1049 ScalarEvolution &SE) const {
1050 const SCEV *Result = getStart();
1051 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1052 // The computation is correct in the face of overflow provided that the
1053 // multiplication is performed _after_ the evaluation of the binomial
1055 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1056 if (isa<SCEVCouldNotCompute>(Coeff))
1059 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1064 //===----------------------------------------------------------------------===//
1065 // SCEV Expression folder implementations
1066 //===----------------------------------------------------------------------===//
1068 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1070 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
1071 "This is not a truncating conversion!");
1072 assert(isSCEVable(Ty) &&
1073 "This is not a conversion to a SCEVable type!");
1074 Ty = getEffectiveSCEVType(Ty);
1076 FoldingSetNodeID ID;
1077 ID.AddInteger(scTruncate);
1081 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1083 // Fold if the operand is constant.
1084 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1086 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1088 // trunc(trunc(x)) --> trunc(x)
1089 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1090 return getTruncateExpr(ST->getOperand(), Ty);
1092 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1093 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1094 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1096 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1097 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1098 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1100 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1101 // eliminate all the truncates, or we replace other casts with truncates.
1102 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1103 SmallVector<const SCEV *, 4> Operands;
1104 bool hasTrunc = false;
1105 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1106 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1107 if (!isa<SCEVCastExpr>(SA->getOperand(i)))
1108 hasTrunc = isa<SCEVTruncateExpr>(S);
1109 Operands.push_back(S);
1112 return getAddExpr(Operands);
1113 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1116 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1117 // eliminate all the truncates, or we replace other casts with truncates.
1118 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1119 SmallVector<const SCEV *, 4> Operands;
1120 bool hasTrunc = false;
1121 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1122 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1123 if (!isa<SCEVCastExpr>(SM->getOperand(i)))
1124 hasTrunc = isa<SCEVTruncateExpr>(S);
1125 Operands.push_back(S);
1128 return getMulExpr(Operands);
1129 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1132 // If the input value is a chrec scev, truncate the chrec's operands.
1133 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1134 SmallVector<const SCEV *, 4> Operands;
1135 for (const SCEV *Op : AddRec->operands())
1136 Operands.push_back(getTruncateExpr(Op, Ty));
1137 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1140 // The cast wasn't folded; create an explicit cast node. We can reuse
1141 // the existing insert position since if we get here, we won't have
1142 // made any changes which would invalidate it.
1143 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1145 UniqueSCEVs.InsertNode(S, IP);
1149 // Get the limit of a recurrence such that incrementing by Step cannot cause
1150 // signed overflow as long as the value of the recurrence within the
1151 // loop does not exceed this limit before incrementing.
1152 static const SCEV *getSignedOverflowLimitForStep(const SCEV *Step,
1153 ICmpInst::Predicate *Pred,
1154 ScalarEvolution *SE) {
1155 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1156 if (SE->isKnownPositive(Step)) {
1157 *Pred = ICmpInst::ICMP_SLT;
1158 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1159 SE->getSignedRange(Step).getSignedMax());
1161 if (SE->isKnownNegative(Step)) {
1162 *Pred = ICmpInst::ICMP_SGT;
1163 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1164 SE->getSignedRange(Step).getSignedMin());
1169 // Get the limit of a recurrence such that incrementing by Step cannot cause
1170 // unsigned overflow as long as the value of the recurrence within the loop does
1171 // not exceed this limit before incrementing.
1172 static const SCEV *getUnsignedOverflowLimitForStep(const SCEV *Step,
1173 ICmpInst::Predicate *Pred,
1174 ScalarEvolution *SE) {
1175 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1176 *Pred = ICmpInst::ICMP_ULT;
1178 return SE->getConstant(APInt::getMinValue(BitWidth) -
1179 SE->getUnsignedRange(Step).getUnsignedMax());
1184 struct ExtendOpTraitsBase {
1185 typedef const SCEV *(ScalarEvolution::*GetExtendExprTy)(const SCEV *, Type *);
1188 // Used to make code generic over signed and unsigned overflow.
1189 template <typename ExtendOp> struct ExtendOpTraits {
1192 // static const SCEV::NoWrapFlags WrapType;
1194 // static const ExtendOpTraitsBase::GetExtendExprTy GetExtendExpr;
1196 // static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1197 // ICmpInst::Predicate *Pred,
1198 // ScalarEvolution *SE);
1202 struct ExtendOpTraits<SCEVSignExtendExpr> : public ExtendOpTraitsBase {
1203 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNSW;
1205 static const GetExtendExprTy GetExtendExpr;
1207 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1208 ICmpInst::Predicate *Pred,
1209 ScalarEvolution *SE) {
1210 return getSignedOverflowLimitForStep(Step, Pred, SE);
1214 const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1215 SCEVSignExtendExpr>::GetExtendExpr = &ScalarEvolution::getSignExtendExpr;
1218 struct ExtendOpTraits<SCEVZeroExtendExpr> : public ExtendOpTraitsBase {
1219 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNUW;
1221 static const GetExtendExprTy GetExtendExpr;
1223 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1224 ICmpInst::Predicate *Pred,
1225 ScalarEvolution *SE) {
1226 return getUnsignedOverflowLimitForStep(Step, Pred, SE);
1230 const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1231 SCEVZeroExtendExpr>::GetExtendExpr = &ScalarEvolution::getZeroExtendExpr;
1234 // The recurrence AR has been shown to have no signed/unsigned wrap or something
1235 // close to it. Typically, if we can prove NSW/NUW for AR, then we can just as
1236 // easily prove NSW/NUW for its preincrement or postincrement sibling. This
1237 // allows normalizing a sign/zero extended AddRec as such: {sext/zext(Step +
1238 // Start),+,Step} => {(Step + sext/zext(Start),+,Step} As a result, the
1239 // expression "Step + sext/zext(PreIncAR)" is congruent with
1240 // "sext/zext(PostIncAR)"
1241 template <typename ExtendOpTy>
1242 static const SCEV *getPreStartForExtend(const SCEVAddRecExpr *AR, Type *Ty,
1243 ScalarEvolution *SE) {
1244 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1245 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1247 const Loop *L = AR->getLoop();
1248 const SCEV *Start = AR->getStart();
1249 const SCEV *Step = AR->getStepRecurrence(*SE);
1251 // Check for a simple looking step prior to loop entry.
1252 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1256 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1257 // subtraction is expensive. For this purpose, perform a quick and dirty
1258 // difference, by checking for Step in the operand list.
1259 SmallVector<const SCEV *, 4> DiffOps;
1260 for (const SCEV *Op : SA->operands())
1262 DiffOps.push_back(Op);
1264 if (DiffOps.size() == SA->getNumOperands())
1267 // Try to prove `WrapType` (SCEV::FlagNSW or SCEV::FlagNUW) on `PreStart` +
1270 // 1. NSW/NUW flags on the step increment.
1271 auto PreStartFlags =
1272 ScalarEvolution::maskFlags(SA->getNoWrapFlags(), SCEV::FlagNUW);
1273 const SCEV *PreStart = SE->getAddExpr(DiffOps, PreStartFlags);
1274 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1275 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1277 // "{S,+,X} is <nsw>/<nuw>" and "the backedge is taken at least once" implies
1278 // "S+X does not sign/unsign-overflow".
1281 const SCEV *BECount = SE->getBackedgeTakenCount(L);
1282 if (PreAR && PreAR->getNoWrapFlags(WrapType) &&
1283 !isa<SCEVCouldNotCompute>(BECount) && SE->isKnownPositive(BECount))
1286 // 2. Direct overflow check on the step operation's expression.
1287 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1288 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1289 const SCEV *OperandExtendedStart =
1290 SE->getAddExpr((SE->*GetExtendExpr)(PreStart, WideTy),
1291 (SE->*GetExtendExpr)(Step, WideTy));
1292 if ((SE->*GetExtendExpr)(Start, WideTy) == OperandExtendedStart) {
1293 if (PreAR && AR->getNoWrapFlags(WrapType)) {
1294 // If we know `AR` == {`PreStart`+`Step`,+,`Step`} is `WrapType` (FlagNSW
1295 // or FlagNUW) and that `PreStart` + `Step` is `WrapType` too, then
1296 // `PreAR` == {`PreStart`,+,`Step`} is also `WrapType`. Cache this fact.
1297 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(WrapType);
1302 // 3. Loop precondition.
1303 ICmpInst::Predicate Pred;
1304 const SCEV *OverflowLimit =
1305 ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(Step, &Pred, SE);
1307 if (OverflowLimit &&
1308 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit))
1314 // Get the normalized zero or sign extended expression for this AddRec's Start.
1315 template <typename ExtendOpTy>
1316 static const SCEV *getExtendAddRecStart(const SCEVAddRecExpr *AR, Type *Ty,
1317 ScalarEvolution *SE) {
1318 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1320 const SCEV *PreStart = getPreStartForExtend<ExtendOpTy>(AR, Ty, SE);
1322 return (SE->*GetExtendExpr)(AR->getStart(), Ty);
1324 return SE->getAddExpr((SE->*GetExtendExpr)(AR->getStepRecurrence(*SE), Ty),
1325 (SE->*GetExtendExpr)(PreStart, Ty));
1328 // Try to prove away overflow by looking at "nearby" add recurrences. A
1329 // motivating example for this rule: if we know `{0,+,4}` is `ult` `-1` and it
1330 // does not itself wrap then we can conclude that `{1,+,4}` is `nuw`.
1334 // {S,+,X} == {S-T,+,X} + T
1335 // => Ext({S,+,X}) == Ext({S-T,+,X} + T)
1337 // If ({S-T,+,X} + T) does not overflow ... (1)
1339 // RHS == Ext({S-T,+,X} + T) == Ext({S-T,+,X}) + Ext(T)
1341 // If {S-T,+,X} does not overflow ... (2)
1343 // RHS == Ext({S-T,+,X}) + Ext(T) == {Ext(S-T),+,Ext(X)} + Ext(T)
1344 // == {Ext(S-T)+Ext(T),+,Ext(X)}
1346 // If (S-T)+T does not overflow ... (3)
1348 // RHS == {Ext(S-T)+Ext(T),+,Ext(X)} == {Ext(S-T+T),+,Ext(X)}
1349 // == {Ext(S),+,Ext(X)} == LHS
1351 // Thus, if (1), (2) and (3) are true for some T, then
1352 // Ext({S,+,X}) == {Ext(S),+,Ext(X)}
1354 // (3) is implied by (1) -- "(S-T)+T does not overflow" is simply "({S-T,+,X}+T)
1355 // does not overflow" restricted to the 0th iteration. Therefore we only need
1356 // to check for (1) and (2).
1358 // In the current context, S is `Start`, X is `Step`, Ext is `ExtendOpTy` and T
1359 // is `Delta` (defined below).
1361 template <typename ExtendOpTy>
1362 bool ScalarEvolution::proveNoWrapByVaryingStart(const SCEV *Start,
1365 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1367 // We restrict `Start` to a constant to prevent SCEV from spending too much
1368 // time here. It is correct (but more expensive) to continue with a
1369 // non-constant `Start` and do a general SCEV subtraction to compute
1370 // `PreStart` below.
1372 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start);
1376 APInt StartAI = StartC->getValue()->getValue();
1378 for (unsigned Delta : {-2, -1, 1, 2}) {
1379 const SCEV *PreStart = getConstant(StartAI - Delta);
1381 FoldingSetNodeID ID;
1382 ID.AddInteger(scAddRecExpr);
1383 ID.AddPointer(PreStart);
1384 ID.AddPointer(Step);
1388 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1390 // Give up if we don't already have the add recurrence we need because
1391 // actually constructing an add recurrence is relatively expensive.
1392 if (PreAR && PreAR->getNoWrapFlags(WrapType)) { // proves (2)
1393 const SCEV *DeltaS = getConstant(StartC->getType(), Delta);
1394 ICmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1395 const SCEV *Limit = ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(
1396 DeltaS, &Pred, this);
1397 if (Limit && isKnownPredicate(Pred, PreAR, Limit)) // proves (1)
1405 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
1407 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1408 "This is not an extending conversion!");
1409 assert(isSCEVable(Ty) &&
1410 "This is not a conversion to a SCEVable type!");
1411 Ty = getEffectiveSCEVType(Ty);
1413 // Fold if the operand is constant.
1414 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1416 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1418 // zext(zext(x)) --> zext(x)
1419 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1420 return getZeroExtendExpr(SZ->getOperand(), Ty);
1422 // Before doing any expensive analysis, check to see if we've already
1423 // computed a SCEV for this Op and Ty.
1424 FoldingSetNodeID ID;
1425 ID.AddInteger(scZeroExtend);
1429 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1431 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1432 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1433 // It's possible the bits taken off by the truncate were all zero bits. If
1434 // so, we should be able to simplify this further.
1435 const SCEV *X = ST->getOperand();
1436 ConstantRange CR = getUnsignedRange(X);
1437 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1438 unsigned NewBits = getTypeSizeInBits(Ty);
1439 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1440 CR.zextOrTrunc(NewBits)))
1441 return getTruncateOrZeroExtend(X, Ty);
1444 // If the input value is a chrec scev, and we can prove that the value
1445 // did not overflow the old, smaller, value, we can zero extend all of the
1446 // operands (often constants). This allows analysis of something like
1447 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1448 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1449 if (AR->isAffine()) {
1450 const SCEV *Start = AR->getStart();
1451 const SCEV *Step = AR->getStepRecurrence(*this);
1452 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1453 const Loop *L = AR->getLoop();
1455 // If we have special knowledge that this addrec won't overflow,
1456 // we don't need to do any further analysis.
1457 if (AR->getNoWrapFlags(SCEV::FlagNUW))
1458 return getAddRecExpr(
1459 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1460 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1462 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1463 // Note that this serves two purposes: It filters out loops that are
1464 // simply not analyzable, and it covers the case where this code is
1465 // being called from within backedge-taken count analysis, such that
1466 // attempting to ask for the backedge-taken count would likely result
1467 // in infinite recursion. In the later case, the analysis code will
1468 // cope with a conservative value, and it will take care to purge
1469 // that value once it has finished.
1470 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1471 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1472 // Manually compute the final value for AR, checking for
1475 // Check whether the backedge-taken count can be losslessly casted to
1476 // the addrec's type. The count is always unsigned.
1477 const SCEV *CastedMaxBECount =
1478 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1479 const SCEV *RecastedMaxBECount =
1480 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1481 if (MaxBECount == RecastedMaxBECount) {
1482 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1483 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1484 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1485 const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul), WideTy);
1486 const SCEV *WideStart = getZeroExtendExpr(Start, WideTy);
1487 const SCEV *WideMaxBECount =
1488 getZeroExtendExpr(CastedMaxBECount, WideTy);
1489 const SCEV *OperandExtendedAdd =
1490 getAddExpr(WideStart,
1491 getMulExpr(WideMaxBECount,
1492 getZeroExtendExpr(Step, WideTy)));
1493 if (ZAdd == OperandExtendedAdd) {
1494 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1495 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1496 // Return the expression with the addrec on the outside.
1497 return getAddRecExpr(
1498 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1499 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1501 // Similar to above, only this time treat the step value as signed.
1502 // This covers loops that count down.
1503 OperandExtendedAdd =
1504 getAddExpr(WideStart,
1505 getMulExpr(WideMaxBECount,
1506 getSignExtendExpr(Step, WideTy)));
1507 if (ZAdd == OperandExtendedAdd) {
1508 // Cache knowledge of AR NW, which is propagated to this AddRec.
1509 // Negative step causes unsigned wrap, but it still can't self-wrap.
1510 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1511 // Return the expression with the addrec on the outside.
1512 return getAddRecExpr(
1513 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1514 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1518 // If the backedge is guarded by a comparison with the pre-inc value
1519 // the addrec is safe. Also, if the entry is guarded by a comparison
1520 // with the start value and the backedge is guarded by a comparison
1521 // with the post-inc value, the addrec is safe.
1522 if (isKnownPositive(Step)) {
1523 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1524 getUnsignedRange(Step).getUnsignedMax());
1525 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1526 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1527 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1528 AR->getPostIncExpr(*this), N))) {
1529 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1530 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1531 // Return the expression with the addrec on the outside.
1532 return getAddRecExpr(
1533 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1534 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1536 } else if (isKnownNegative(Step)) {
1537 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1538 getSignedRange(Step).getSignedMin());
1539 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1540 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1541 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1542 AR->getPostIncExpr(*this), N))) {
1543 // Cache knowledge of AR NW, which is propagated to this AddRec.
1544 // Negative step causes unsigned wrap, but it still can't self-wrap.
1545 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1546 // Return the expression with the addrec on the outside.
1547 return getAddRecExpr(
1548 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1549 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1554 if (proveNoWrapByVaryingStart<SCEVZeroExtendExpr>(Start, Step, L)) {
1555 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1556 return getAddRecExpr(
1557 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1558 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1562 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1563 // zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw>
1564 if (SA->getNoWrapFlags(SCEV::FlagNUW)) {
1565 // If the addition does not unsign overflow then we can, by definition,
1566 // commute the zero extension with the addition operation.
1567 SmallVector<const SCEV *, 4> Ops;
1568 for (const auto *Op : SA->operands())
1569 Ops.push_back(getZeroExtendExpr(Op, Ty));
1570 return getAddExpr(Ops, SCEV::FlagNUW);
1574 // The cast wasn't folded; create an explicit cast node.
1575 // Recompute the insert position, as it may have been invalidated.
1576 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1577 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1579 UniqueSCEVs.InsertNode(S, IP);
1583 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1585 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1586 "This is not an extending conversion!");
1587 assert(isSCEVable(Ty) &&
1588 "This is not a conversion to a SCEVable type!");
1589 Ty = getEffectiveSCEVType(Ty);
1591 // Fold if the operand is constant.
1592 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1594 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1596 // sext(sext(x)) --> sext(x)
1597 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1598 return getSignExtendExpr(SS->getOperand(), Ty);
1600 // sext(zext(x)) --> zext(x)
1601 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1602 return getZeroExtendExpr(SZ->getOperand(), Ty);
1604 // Before doing any expensive analysis, check to see if we've already
1605 // computed a SCEV for this Op and Ty.
1606 FoldingSetNodeID ID;
1607 ID.AddInteger(scSignExtend);
1611 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1613 // If the input value is provably positive, build a zext instead.
1614 if (isKnownNonNegative(Op))
1615 return getZeroExtendExpr(Op, Ty);
1617 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1618 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1619 // It's possible the bits taken off by the truncate were all sign bits. If
1620 // so, we should be able to simplify this further.
1621 const SCEV *X = ST->getOperand();
1622 ConstantRange CR = getSignedRange(X);
1623 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1624 unsigned NewBits = getTypeSizeInBits(Ty);
1625 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1626 CR.sextOrTrunc(NewBits)))
1627 return getTruncateOrSignExtend(X, Ty);
1630 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1631 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1632 if (SA->getNumOperands() == 2) {
1633 auto *SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1634 auto *SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1636 if (auto *SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1637 const APInt &C1 = SC1->getValue()->getValue();
1638 const APInt &C2 = SC2->getValue()->getValue();
1639 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1640 C2.ugt(C1) && C2.isPowerOf2())
1641 return getAddExpr(getSignExtendExpr(SC1, Ty),
1642 getSignExtendExpr(SMul, Ty));
1647 // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw>
1648 if (SA->getNoWrapFlags(SCEV::FlagNSW)) {
1649 // If the addition does not sign overflow then we can, by definition,
1650 // commute the sign extension with the addition operation.
1651 SmallVector<const SCEV *, 4> Ops;
1652 for (const auto *Op : SA->operands())
1653 Ops.push_back(getSignExtendExpr(Op, Ty));
1654 return getAddExpr(Ops, SCEV::FlagNSW);
1657 // If the input value is a chrec scev, and we can prove that the value
1658 // did not overflow the old, smaller, value, we can sign extend all of the
1659 // operands (often constants). This allows analysis of something like
1660 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1661 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1662 if (AR->isAffine()) {
1663 const SCEV *Start = AR->getStart();
1664 const SCEV *Step = AR->getStepRecurrence(*this);
1665 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1666 const Loop *L = AR->getLoop();
1668 // If we have special knowledge that this addrec won't overflow,
1669 // we don't need to do any further analysis.
1670 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1671 return getAddRecExpr(
1672 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1673 getSignExtendExpr(Step, Ty), L, SCEV::FlagNSW);
1675 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1676 // Note that this serves two purposes: It filters out loops that are
1677 // simply not analyzable, and it covers the case where this code is
1678 // being called from within backedge-taken count analysis, such that
1679 // attempting to ask for the backedge-taken count would likely result
1680 // in infinite recursion. In the later case, the analysis code will
1681 // cope with a conservative value, and it will take care to purge
1682 // that value once it has finished.
1683 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1684 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1685 // Manually compute the final value for AR, checking for
1688 // Check whether the backedge-taken count can be losslessly casted to
1689 // the addrec's type. The count is always unsigned.
1690 const SCEV *CastedMaxBECount =
1691 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1692 const SCEV *RecastedMaxBECount =
1693 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1694 if (MaxBECount == RecastedMaxBECount) {
1695 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1696 // Check whether Start+Step*MaxBECount has no signed overflow.
1697 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1698 const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul), WideTy);
1699 const SCEV *WideStart = getSignExtendExpr(Start, WideTy);
1700 const SCEV *WideMaxBECount =
1701 getZeroExtendExpr(CastedMaxBECount, WideTy);
1702 const SCEV *OperandExtendedAdd =
1703 getAddExpr(WideStart,
1704 getMulExpr(WideMaxBECount,
1705 getSignExtendExpr(Step, WideTy)));
1706 if (SAdd == OperandExtendedAdd) {
1707 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1708 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1709 // Return the expression with the addrec on the outside.
1710 return getAddRecExpr(
1711 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1712 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1714 // Similar to above, only this time treat the step value as unsigned.
1715 // This covers loops that count up with an unsigned step.
1716 OperandExtendedAdd =
1717 getAddExpr(WideStart,
1718 getMulExpr(WideMaxBECount,
1719 getZeroExtendExpr(Step, WideTy)));
1720 if (SAdd == OperandExtendedAdd) {
1721 // If AR wraps around then
1723 // abs(Step) * MaxBECount > unsigned-max(AR->getType())
1724 // => SAdd != OperandExtendedAdd
1726 // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=>
1727 // (SAdd == OperandExtendedAdd => AR is NW)
1729 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1731 // Return the expression with the addrec on the outside.
1732 return getAddRecExpr(
1733 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1734 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1738 // If the backedge is guarded by a comparison with the pre-inc value
1739 // the addrec is safe. Also, if the entry is guarded by a comparison
1740 // with the start value and the backedge is guarded by a comparison
1741 // with the post-inc value, the addrec is safe.
1742 ICmpInst::Predicate Pred;
1743 const SCEV *OverflowLimit =
1744 getSignedOverflowLimitForStep(Step, &Pred, this);
1745 if (OverflowLimit &&
1746 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1747 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1748 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1750 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1751 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1752 return getAddRecExpr(
1753 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1754 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1757 // If Start and Step are constants, check if we can apply this
1759 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1760 auto *SC1 = dyn_cast<SCEVConstant>(Start);
1761 auto *SC2 = dyn_cast<SCEVConstant>(Step);
1763 const APInt &C1 = SC1->getValue()->getValue();
1764 const APInt &C2 = SC2->getValue()->getValue();
1765 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1767 Start = getSignExtendExpr(Start, Ty);
1768 const SCEV *NewAR = getAddRecExpr(getZero(AR->getType()), Step, L,
1769 AR->getNoWrapFlags());
1770 return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
1774 if (proveNoWrapByVaryingStart<SCEVSignExtendExpr>(Start, Step, L)) {
1775 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1776 return getAddRecExpr(
1777 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1778 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1782 // The cast wasn't folded; create an explicit cast node.
1783 // Recompute the insert position, as it may have been invalidated.
1784 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1785 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1787 UniqueSCEVs.InsertNode(S, IP);
1791 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1792 /// unspecified bits out to the given type.
1794 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1796 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1797 "This is not an extending conversion!");
1798 assert(isSCEVable(Ty) &&
1799 "This is not a conversion to a SCEVable type!");
1800 Ty = getEffectiveSCEVType(Ty);
1802 // Sign-extend negative constants.
1803 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1804 if (SC->getValue()->getValue().isNegative())
1805 return getSignExtendExpr(Op, Ty);
1807 // Peel off a truncate cast.
1808 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1809 const SCEV *NewOp = T->getOperand();
1810 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1811 return getAnyExtendExpr(NewOp, Ty);
1812 return getTruncateOrNoop(NewOp, Ty);
1815 // Next try a zext cast. If the cast is folded, use it.
1816 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1817 if (!isa<SCEVZeroExtendExpr>(ZExt))
1820 // Next try a sext cast. If the cast is folded, use it.
1821 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1822 if (!isa<SCEVSignExtendExpr>(SExt))
1825 // Force the cast to be folded into the operands of an addrec.
1826 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1827 SmallVector<const SCEV *, 4> Ops;
1828 for (const SCEV *Op : AR->operands())
1829 Ops.push_back(getAnyExtendExpr(Op, Ty));
1830 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1833 // If the expression is obviously signed, use the sext cast value.
1834 if (isa<SCEVSMaxExpr>(Op))
1837 // Absent any other information, use the zext cast value.
1841 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1842 /// a list of operands to be added under the given scale, update the given
1843 /// map. This is a helper function for getAddRecExpr. As an example of
1844 /// what it does, given a sequence of operands that would form an add
1845 /// expression like this:
1847 /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
1849 /// where A and B are constants, update the map with these values:
1851 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1853 /// and add 13 + A*B*29 to AccumulatedConstant.
1854 /// This will allow getAddRecExpr to produce this:
1856 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1858 /// This form often exposes folding opportunities that are hidden in
1859 /// the original operand list.
1861 /// Return true iff it appears that any interesting folding opportunities
1862 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1863 /// the common case where no interesting opportunities are present, and
1864 /// is also used as a check to avoid infinite recursion.
1867 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1868 SmallVectorImpl<const SCEV *> &NewOps,
1869 APInt &AccumulatedConstant,
1870 const SCEV *const *Ops, size_t NumOperands,
1872 ScalarEvolution &SE) {
1873 bool Interesting = false;
1875 // Iterate over the add operands. They are sorted, with constants first.
1877 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1879 // Pull a buried constant out to the outside.
1880 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1882 AccumulatedConstant += Scale * C->getValue()->getValue();
1885 // Next comes everything else. We're especially interested in multiplies
1886 // here, but they're in the middle, so just visit the rest with one loop.
1887 for (; i != NumOperands; ++i) {
1888 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1889 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1891 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1892 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1893 // A multiplication of a constant with another add; recurse.
1894 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1896 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1897 Add->op_begin(), Add->getNumOperands(),
1900 // A multiplication of a constant with some other value. Update
1902 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1903 const SCEV *Key = SE.getMulExpr(MulOps);
1904 auto Pair = M.insert(std::make_pair(Key, NewScale));
1906 NewOps.push_back(Pair.first->first);
1908 Pair.first->second += NewScale;
1909 // The map already had an entry for this value, which may indicate
1910 // a folding opportunity.
1915 // An ordinary operand. Update the map.
1916 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1917 M.insert(std::make_pair(Ops[i], Scale));
1919 NewOps.push_back(Pair.first->first);
1921 Pair.first->second += Scale;
1922 // The map already had an entry for this value, which may indicate
1923 // a folding opportunity.
1933 struct APIntCompare {
1934 bool operator()(const APInt &LHS, const APInt &RHS) const {
1935 return LHS.ult(RHS);
1940 // We're trying to construct a SCEV of type `Type' with `Ops' as operands and
1941 // `OldFlags' as can't-wrap behavior. Infer a more aggressive set of
1942 // can't-overflow flags for the operation if possible.
1943 static SCEV::NoWrapFlags
1944 StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
1945 const SmallVectorImpl<const SCEV *> &Ops,
1946 SCEV::NoWrapFlags Flags) {
1947 using namespace std::placeholders;
1948 typedef OverflowingBinaryOperator OBO;
1951 Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr;
1953 assert(CanAnalyze && "don't call from other places!");
1955 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1956 SCEV::NoWrapFlags SignOrUnsignWrap =
1957 ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
1959 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1960 auto IsKnownNonNegative =
1961 std::bind(std::mem_fn(&ScalarEvolution::isKnownNonNegative), SE, _1);
1963 if (SignOrUnsignWrap == SCEV::FlagNSW &&
1964 std::all_of(Ops.begin(), Ops.end(), IsKnownNonNegative))
1966 ScalarEvolution::setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1968 SignOrUnsignWrap = ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
1970 if (SignOrUnsignWrap != SignOrUnsignMask && Type == scAddExpr &&
1971 Ops.size() == 2 && isa<SCEVConstant>(Ops[0])) {
1973 // (A + C) --> (A + C)<nsw> if the addition does not sign overflow
1974 // (A + C) --> (A + C)<nuw> if the addition does not unsign overflow
1976 const APInt &C = cast<SCEVConstant>(Ops[0])->getValue()->getValue();
1977 if (!(SignOrUnsignWrap & SCEV::FlagNSW)) {
1979 ConstantRange::makeNoWrapRegion(Instruction::Add, C, OBO::NoSignedWrap);
1980 if (NSWRegion.contains(SE->getSignedRange(Ops[1])))
1981 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
1983 if (!(SignOrUnsignWrap & SCEV::FlagNUW)) {
1985 ConstantRange::makeNoWrapRegion(Instruction::Add, C,
1986 OBO::NoUnsignedWrap);
1987 if (NUWRegion.contains(SE->getUnsignedRange(Ops[1])))
1988 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
1995 /// getAddExpr - Get a canonical add expression, or something simpler if
1997 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1998 SCEV::NoWrapFlags Flags) {
1999 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
2000 "only nuw or nsw allowed");
2001 assert(!Ops.empty() && "Cannot get empty add!");
2002 if (Ops.size() == 1) return Ops[0];
2004 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2005 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2006 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2007 "SCEVAddExpr operand types don't match!");
2010 // Sort by complexity, this groups all similar expression types together.
2011 GroupByComplexity(Ops, &LI);
2013 Flags = StrengthenNoWrapFlags(this, scAddExpr, Ops, Flags);
2015 // If there are any constants, fold them together.
2017 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2019 assert(Idx < Ops.size());
2020 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2021 // We found two constants, fold them together!
2022 Ops[0] = getConstant(LHSC->getValue()->getValue() +
2023 RHSC->getValue()->getValue());
2024 if (Ops.size() == 2) return Ops[0];
2025 Ops.erase(Ops.begin()+1); // Erase the folded element
2026 LHSC = cast<SCEVConstant>(Ops[0]);
2029 // If we are left with a constant zero being added, strip it off.
2030 if (LHSC->getValue()->isZero()) {
2031 Ops.erase(Ops.begin());
2035 if (Ops.size() == 1) return Ops[0];
2038 // Okay, check to see if the same value occurs in the operand list more than
2039 // once. If so, merge them together into an multiply expression. Since we
2040 // sorted the list, these values are required to be adjacent.
2041 Type *Ty = Ops[0]->getType();
2042 bool FoundMatch = false;
2043 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
2044 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
2045 // Scan ahead to count how many equal operands there are.
2047 while (i+Count != e && Ops[i+Count] == Ops[i])
2049 // Merge the values into a multiply.
2050 const SCEV *Scale = getConstant(Ty, Count);
2051 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
2052 if (Ops.size() == Count)
2055 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
2056 --i; e -= Count - 1;
2060 return getAddExpr(Ops, Flags);
2062 // Check for truncates. If all the operands are truncated from the same
2063 // type, see if factoring out the truncate would permit the result to be
2064 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
2065 // if the contents of the resulting outer trunc fold to something simple.
2066 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
2067 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
2068 Type *DstType = Trunc->getType();
2069 Type *SrcType = Trunc->getOperand()->getType();
2070 SmallVector<const SCEV *, 8> LargeOps;
2072 // Check all the operands to see if they can be represented in the
2073 // source type of the truncate.
2074 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
2075 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
2076 if (T->getOperand()->getType() != SrcType) {
2080 LargeOps.push_back(T->getOperand());
2081 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2082 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
2083 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
2084 SmallVector<const SCEV *, 8> LargeMulOps;
2085 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
2086 if (const SCEVTruncateExpr *T =
2087 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
2088 if (T->getOperand()->getType() != SrcType) {
2092 LargeMulOps.push_back(T->getOperand());
2093 } else if (const auto *C = dyn_cast<SCEVConstant>(M->getOperand(j))) {
2094 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
2101 LargeOps.push_back(getMulExpr(LargeMulOps));
2108 // Evaluate the expression in the larger type.
2109 const SCEV *Fold = getAddExpr(LargeOps, Flags);
2110 // If it folds to something simple, use it. Otherwise, don't.
2111 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
2112 return getTruncateExpr(Fold, DstType);
2116 // Skip past any other cast SCEVs.
2117 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
2120 // If there are add operands they would be next.
2121 if (Idx < Ops.size()) {
2122 bool DeletedAdd = false;
2123 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
2124 // If we have an add, expand the add operands onto the end of the operands
2126 Ops.erase(Ops.begin()+Idx);
2127 Ops.append(Add->op_begin(), Add->op_end());
2131 // If we deleted at least one add, we added operands to the end of the list,
2132 // and they are not necessarily sorted. Recurse to resort and resimplify
2133 // any operands we just acquired.
2135 return getAddExpr(Ops);
2138 // Skip over the add expression until we get to a multiply.
2139 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2142 // Check to see if there are any folding opportunities present with
2143 // operands multiplied by constant values.
2144 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
2145 uint64_t BitWidth = getTypeSizeInBits(Ty);
2146 DenseMap<const SCEV *, APInt> M;
2147 SmallVector<const SCEV *, 8> NewOps;
2148 APInt AccumulatedConstant(BitWidth, 0);
2149 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2150 Ops.data(), Ops.size(),
2151 APInt(BitWidth, 1), *this)) {
2152 // Some interesting folding opportunity is present, so its worthwhile to
2153 // re-generate the operands list. Group the operands by constant scale,
2154 // to avoid multiplying by the same constant scale multiple times.
2155 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
2156 for (SmallVectorImpl<const SCEV *>::const_iterator I = NewOps.begin(),
2157 E = NewOps.end(); I != E; ++I)
2158 MulOpLists[M.find(*I)->second].push_back(*I);
2159 // Re-generate the operands list.
2161 if (AccumulatedConstant != 0)
2162 Ops.push_back(getConstant(AccumulatedConstant));
2163 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
2164 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
2166 Ops.push_back(getMulExpr(getConstant(I->first),
2167 getAddExpr(I->second)));
2170 if (Ops.size() == 1)
2172 return getAddExpr(Ops);
2176 // If we are adding something to a multiply expression, make sure the
2177 // something is not already an operand of the multiply. If so, merge it into
2179 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
2180 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
2181 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
2182 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
2183 if (isa<SCEVConstant>(MulOpSCEV))
2185 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
2186 if (MulOpSCEV == Ops[AddOp]) {
2187 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
2188 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
2189 if (Mul->getNumOperands() != 2) {
2190 // If the multiply has more than two operands, we must get the
2192 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2193 Mul->op_begin()+MulOp);
2194 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2195 InnerMul = getMulExpr(MulOps);
2197 const SCEV *One = getOne(Ty);
2198 const SCEV *AddOne = getAddExpr(One, InnerMul);
2199 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
2200 if (Ops.size() == 2) return OuterMul;
2202 Ops.erase(Ops.begin()+AddOp);
2203 Ops.erase(Ops.begin()+Idx-1);
2205 Ops.erase(Ops.begin()+Idx);
2206 Ops.erase(Ops.begin()+AddOp-1);
2208 Ops.push_back(OuterMul);
2209 return getAddExpr(Ops);
2212 // Check this multiply against other multiplies being added together.
2213 for (unsigned OtherMulIdx = Idx+1;
2214 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
2216 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
2217 // If MulOp occurs in OtherMul, we can fold the two multiplies
2219 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
2220 OMulOp != e; ++OMulOp)
2221 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
2222 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
2223 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
2224 if (Mul->getNumOperands() != 2) {
2225 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2226 Mul->op_begin()+MulOp);
2227 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2228 InnerMul1 = getMulExpr(MulOps);
2230 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2231 if (OtherMul->getNumOperands() != 2) {
2232 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2233 OtherMul->op_begin()+OMulOp);
2234 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2235 InnerMul2 = getMulExpr(MulOps);
2237 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
2238 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2239 if (Ops.size() == 2) return OuterMul;
2240 Ops.erase(Ops.begin()+Idx);
2241 Ops.erase(Ops.begin()+OtherMulIdx-1);
2242 Ops.push_back(OuterMul);
2243 return getAddExpr(Ops);
2249 // If there are any add recurrences in the operands list, see if any other
2250 // added values are loop invariant. If so, we can fold them into the
2252 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2255 // Scan over all recurrences, trying to fold loop invariants into them.
2256 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2257 // Scan all of the other operands to this add and add them to the vector if
2258 // they are loop invariant w.r.t. the recurrence.
2259 SmallVector<const SCEV *, 8> LIOps;
2260 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2261 const Loop *AddRecLoop = AddRec->getLoop();
2262 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2263 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2264 LIOps.push_back(Ops[i]);
2265 Ops.erase(Ops.begin()+i);
2269 // If we found some loop invariants, fold them into the recurrence.
2270 if (!LIOps.empty()) {
2271 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2272 LIOps.push_back(AddRec->getStart());
2274 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2276 AddRecOps[0] = getAddExpr(LIOps);
2278 // Build the new addrec. Propagate the NUW and NSW flags if both the
2279 // outer add and the inner addrec are guaranteed to have no overflow.
2280 // Always propagate NW.
2281 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2282 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2284 // If all of the other operands were loop invariant, we are done.
2285 if (Ops.size() == 1) return NewRec;
2287 // Otherwise, add the folded AddRec by the non-invariant parts.
2288 for (unsigned i = 0;; ++i)
2289 if (Ops[i] == AddRec) {
2293 return getAddExpr(Ops);
2296 // Okay, if there weren't any loop invariants to be folded, check to see if
2297 // there are multiple AddRec's with the same loop induction variable being
2298 // added together. If so, we can fold them.
2299 for (unsigned OtherIdx = Idx+1;
2300 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2302 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2303 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2304 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2306 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2308 if (const SCEVAddRecExpr *OtherAddRec =
2309 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2310 if (OtherAddRec->getLoop() == AddRecLoop) {
2311 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2313 if (i >= AddRecOps.size()) {
2314 AddRecOps.append(OtherAddRec->op_begin()+i,
2315 OtherAddRec->op_end());
2318 AddRecOps[i] = getAddExpr(AddRecOps[i],
2319 OtherAddRec->getOperand(i));
2321 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2323 // Step size has changed, so we cannot guarantee no self-wraparound.
2324 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2325 return getAddExpr(Ops);
2328 // Otherwise couldn't fold anything into this recurrence. Move onto the
2332 // Okay, it looks like we really DO need an add expr. Check to see if we
2333 // already have one, otherwise create a new one.
2334 FoldingSetNodeID ID;
2335 ID.AddInteger(scAddExpr);
2336 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2337 ID.AddPointer(Ops[i]);
2340 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2342 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2343 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2344 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
2346 UniqueSCEVs.InsertNode(S, IP);
2348 S->setNoWrapFlags(Flags);
2352 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2354 if (j > 1 && k / j != i) Overflow = true;
2358 /// Compute the result of "n choose k", the binomial coefficient. If an
2359 /// intermediate computation overflows, Overflow will be set and the return will
2360 /// be garbage. Overflow is not cleared on absence of overflow.
2361 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2362 // We use the multiplicative formula:
2363 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2364 // At each iteration, we take the n-th term of the numeral and divide by the
2365 // (k-n)th term of the denominator. This division will always produce an
2366 // integral result, and helps reduce the chance of overflow in the
2367 // intermediate computations. However, we can still overflow even when the
2368 // final result would fit.
2370 if (n == 0 || n == k) return 1;
2371 if (k > n) return 0;
2377 for (uint64_t i = 1; i <= k; ++i) {
2378 r = umul_ov(r, n-(i-1), Overflow);
2384 /// Determine if any of the operands in this SCEV are a constant or if
2385 /// any of the add or multiply expressions in this SCEV contain a constant.
2386 static bool containsConstantSomewhere(const SCEV *StartExpr) {
2387 SmallVector<const SCEV *, 4> Ops;
2388 Ops.push_back(StartExpr);
2389 while (!Ops.empty()) {
2390 const SCEV *CurrentExpr = Ops.pop_back_val();
2391 if (isa<SCEVConstant>(*CurrentExpr))
2394 if (isa<SCEVAddExpr>(*CurrentExpr) || isa<SCEVMulExpr>(*CurrentExpr)) {
2395 const auto *CurrentNAry = cast<SCEVNAryExpr>(CurrentExpr);
2396 Ops.append(CurrentNAry->op_begin(), CurrentNAry->op_end());
2402 /// getMulExpr - Get a canonical multiply expression, or something simpler if
2404 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2405 SCEV::NoWrapFlags Flags) {
2406 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
2407 "only nuw or nsw allowed");
2408 assert(!Ops.empty() && "Cannot get empty mul!");
2409 if (Ops.size() == 1) return Ops[0];
2411 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2412 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2413 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2414 "SCEVMulExpr operand types don't match!");
2417 // Sort by complexity, this groups all similar expression types together.
2418 GroupByComplexity(Ops, &LI);
2420 Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
2422 // If there are any constants, fold them together.
2424 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2426 // C1*(C2+V) -> C1*C2 + C1*V
2427 if (Ops.size() == 2)
2428 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2429 // If any of Add's ops are Adds or Muls with a constant,
2430 // apply this transformation as well.
2431 if (Add->getNumOperands() == 2)
2432 if (containsConstantSomewhere(Add))
2433 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2434 getMulExpr(LHSC, Add->getOperand(1)));
2437 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2438 // We found two constants, fold them together!
2439 ConstantInt *Fold = ConstantInt::get(getContext(),
2440 LHSC->getValue()->getValue() *
2441 RHSC->getValue()->getValue());
2442 Ops[0] = getConstant(Fold);
2443 Ops.erase(Ops.begin()+1); // Erase the folded element
2444 if (Ops.size() == 1) return Ops[0];
2445 LHSC = cast<SCEVConstant>(Ops[0]);
2448 // If we are left with a constant one being multiplied, strip it off.
2449 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2450 Ops.erase(Ops.begin());
2452 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2453 // If we have a multiply of zero, it will always be zero.
2455 } else if (Ops[0]->isAllOnesValue()) {
2456 // If we have a mul by -1 of an add, try distributing the -1 among the
2458 if (Ops.size() == 2) {
2459 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2460 SmallVector<const SCEV *, 4> NewOps;
2461 bool AnyFolded = false;
2462 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
2463 E = Add->op_end(); I != E; ++I) {
2464 const SCEV *Mul = getMulExpr(Ops[0], *I);
2465 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2466 NewOps.push_back(Mul);
2469 return getAddExpr(NewOps);
2470 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2471 // Negation preserves a recurrence's no self-wrap property.
2472 SmallVector<const SCEV *, 4> Operands;
2473 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
2474 E = AddRec->op_end(); I != E; ++I) {
2475 Operands.push_back(getMulExpr(Ops[0], *I));
2477 return getAddRecExpr(Operands, AddRec->getLoop(),
2478 AddRec->getNoWrapFlags(SCEV::FlagNW));
2483 if (Ops.size() == 1)
2487 // Skip over the add expression until we get to a multiply.
2488 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2491 // If there are mul operands inline them all into this expression.
2492 if (Idx < Ops.size()) {
2493 bool DeletedMul = false;
2494 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2495 // If we have an mul, expand the mul operands onto the end of the operands
2497 Ops.erase(Ops.begin()+Idx);
2498 Ops.append(Mul->op_begin(), Mul->op_end());
2502 // If we deleted at least one mul, we added operands to the end of the list,
2503 // and they are not necessarily sorted. Recurse to resort and resimplify
2504 // any operands we just acquired.
2506 return getMulExpr(Ops);
2509 // If there are any add recurrences in the operands list, see if any other
2510 // added values are loop invariant. If so, we can fold them into the
2512 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2515 // Scan over all recurrences, trying to fold loop invariants into them.
2516 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2517 // Scan all of the other operands to this mul and add them to the vector if
2518 // they are loop invariant w.r.t. the recurrence.
2519 SmallVector<const SCEV *, 8> LIOps;
2520 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2521 const Loop *AddRecLoop = AddRec->getLoop();
2522 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2523 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2524 LIOps.push_back(Ops[i]);
2525 Ops.erase(Ops.begin()+i);
2529 // If we found some loop invariants, fold them into the recurrence.
2530 if (!LIOps.empty()) {
2531 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2532 SmallVector<const SCEV *, 4> NewOps;
2533 NewOps.reserve(AddRec->getNumOperands());
2534 const SCEV *Scale = getMulExpr(LIOps);
2535 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2536 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2538 // Build the new addrec. Propagate the NUW and NSW flags if both the
2539 // outer mul and the inner addrec are guaranteed to have no overflow.
2541 // No self-wrap cannot be guaranteed after changing the step size, but
2542 // will be inferred if either NUW or NSW is true.
2543 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2544 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2546 // If all of the other operands were loop invariant, we are done.
2547 if (Ops.size() == 1) return NewRec;
2549 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2550 for (unsigned i = 0;; ++i)
2551 if (Ops[i] == AddRec) {
2555 return getMulExpr(Ops);
2558 // Okay, if there weren't any loop invariants to be folded, check to see if
2559 // there are multiple AddRec's with the same loop induction variable being
2560 // multiplied together. If so, we can fold them.
2562 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2563 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2564 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2565 // ]]],+,...up to x=2n}.
2566 // Note that the arguments to choose() are always integers with values
2567 // known at compile time, never SCEV objects.
2569 // The implementation avoids pointless extra computations when the two
2570 // addrec's are of different length (mathematically, it's equivalent to
2571 // an infinite stream of zeros on the right).
2572 bool OpsModified = false;
2573 for (unsigned OtherIdx = Idx+1;
2574 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2576 const SCEVAddRecExpr *OtherAddRec =
2577 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2578 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2581 bool Overflow = false;
2582 Type *Ty = AddRec->getType();
2583 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2584 SmallVector<const SCEV*, 7> AddRecOps;
2585 for (int x = 0, xe = AddRec->getNumOperands() +
2586 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2587 const SCEV *Term = getZero(Ty);
2588 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2589 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2590 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2591 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2592 z < ze && !Overflow; ++z) {
2593 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2595 if (LargerThan64Bits)
2596 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2598 Coeff = Coeff1*Coeff2;
2599 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2600 const SCEV *Term1 = AddRec->getOperand(y-z);
2601 const SCEV *Term2 = OtherAddRec->getOperand(z);
2602 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2605 AddRecOps.push_back(Term);
2608 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2610 if (Ops.size() == 2) return NewAddRec;
2611 Ops[Idx] = NewAddRec;
2612 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2614 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2620 return getMulExpr(Ops);
2622 // Otherwise couldn't fold anything into this recurrence. Move onto the
2626 // Okay, it looks like we really DO need an mul expr. Check to see if we
2627 // already have one, otherwise create a new one.
2628 FoldingSetNodeID ID;
2629 ID.AddInteger(scMulExpr);
2630 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2631 ID.AddPointer(Ops[i]);
2634 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2636 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2637 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2638 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2640 UniqueSCEVs.InsertNode(S, IP);
2642 S->setNoWrapFlags(Flags);
2646 /// getUDivExpr - Get a canonical unsigned division expression, or something
2647 /// simpler if possible.
2648 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2650 assert(getEffectiveSCEVType(LHS->getType()) ==
2651 getEffectiveSCEVType(RHS->getType()) &&
2652 "SCEVUDivExpr operand types don't match!");
2654 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2655 if (RHSC->getValue()->equalsInt(1))
2656 return LHS; // X udiv 1 --> x
2657 // If the denominator is zero, the result of the udiv is undefined. Don't
2658 // try to analyze it, because the resolution chosen here may differ from
2659 // the resolution chosen in other parts of the compiler.
2660 if (!RHSC->getValue()->isZero()) {
2661 // Determine if the division can be folded into the operands of
2663 // TODO: Generalize this to non-constants by using known-bits information.
2664 Type *Ty = LHS->getType();
2665 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2666 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2667 // For non-power-of-two values, effectively round the value up to the
2668 // nearest power of two.
2669 if (!RHSC->getValue()->getValue().isPowerOf2())
2671 IntegerType *ExtTy =
2672 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2673 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2674 if (const SCEVConstant *Step =
2675 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2676 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2677 const APInt &StepInt = Step->getValue()->getValue();
2678 const APInt &DivInt = RHSC->getValue()->getValue();
2679 if (!StepInt.urem(DivInt) &&
2680 getZeroExtendExpr(AR, ExtTy) ==
2681 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2682 getZeroExtendExpr(Step, ExtTy),
2683 AR->getLoop(), SCEV::FlagAnyWrap)) {
2684 SmallVector<const SCEV *, 4> Operands;
2685 for (const SCEV *Op : AR->operands())
2686 Operands.push_back(getUDivExpr(Op, RHS));
2687 return getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagNW);
2689 /// Get a canonical UDivExpr for a recurrence.
2690 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2691 // We can currently only fold X%N if X is constant.
2692 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2693 if (StartC && !DivInt.urem(StepInt) &&
2694 getZeroExtendExpr(AR, ExtTy) ==
2695 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2696 getZeroExtendExpr(Step, ExtTy),
2697 AR->getLoop(), SCEV::FlagAnyWrap)) {
2698 const APInt &StartInt = StartC->getValue()->getValue();
2699 const APInt &StartRem = StartInt.urem(StepInt);
2701 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2702 AR->getLoop(), SCEV::FlagNW);
2705 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2706 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2707 SmallVector<const SCEV *, 4> Operands;
2708 for (const SCEV *Op : M->operands())
2709 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2710 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2711 // Find an operand that's safely divisible.
2712 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2713 const SCEV *Op = M->getOperand(i);
2714 const SCEV *Div = getUDivExpr(Op, RHSC);
2715 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2716 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2719 return getMulExpr(Operands);
2723 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2724 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2725 SmallVector<const SCEV *, 4> Operands;
2726 for (const SCEV *Op : A->operands())
2727 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2728 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2730 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2731 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2732 if (isa<SCEVUDivExpr>(Op) ||
2733 getMulExpr(Op, RHS) != A->getOperand(i))
2735 Operands.push_back(Op);
2737 if (Operands.size() == A->getNumOperands())
2738 return getAddExpr(Operands);
2742 // Fold if both operands are constant.
2743 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2744 Constant *LHSCV = LHSC->getValue();
2745 Constant *RHSCV = RHSC->getValue();
2746 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2752 FoldingSetNodeID ID;
2753 ID.AddInteger(scUDivExpr);
2757 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2758 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2760 UniqueSCEVs.InsertNode(S, IP);
2764 static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2765 APInt A = C1->getValue()->getValue().abs();
2766 APInt B = C2->getValue()->getValue().abs();
2767 uint32_t ABW = A.getBitWidth();
2768 uint32_t BBW = B.getBitWidth();
2775 return APIntOps::GreatestCommonDivisor(A, B);
2778 /// getUDivExactExpr - Get a canonical unsigned division expression, or
2779 /// something simpler if possible. There is no representation for an exact udiv
2780 /// in SCEV IR, but we can attempt to remove factors from the LHS and RHS.
2781 /// We can't do this when it's not exact because the udiv may be clearing bits.
2782 const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2784 // TODO: we could try to find factors in all sorts of things, but for now we
2785 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2786 // end of this file for inspiration.
2788 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2790 return getUDivExpr(LHS, RHS);
2792 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2793 // If the mulexpr multiplies by a constant, then that constant must be the
2794 // first element of the mulexpr.
2795 if (const auto *LHSCst = dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2796 if (LHSCst == RHSCst) {
2797 SmallVector<const SCEV *, 2> Operands;
2798 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2799 return getMulExpr(Operands);
2802 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
2803 // that there's a factor provided by one of the other terms. We need to
2805 APInt Factor = gcd(LHSCst, RHSCst);
2806 if (!Factor.isIntN(1)) {
2807 LHSCst = cast<SCEVConstant>(
2808 getConstant(LHSCst->getValue()->getValue().udiv(Factor)));
2809 RHSCst = cast<SCEVConstant>(
2810 getConstant(RHSCst->getValue()->getValue().udiv(Factor)));
2811 SmallVector<const SCEV *, 2> Operands;
2812 Operands.push_back(LHSCst);
2813 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2814 LHS = getMulExpr(Operands);
2816 Mul = dyn_cast<SCEVMulExpr>(LHS);
2818 return getUDivExactExpr(LHS, RHS);
2823 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
2824 if (Mul->getOperand(i) == RHS) {
2825 SmallVector<const SCEV *, 2> Operands;
2826 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
2827 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
2828 return getMulExpr(Operands);
2832 return getUDivExpr(LHS, RHS);
2835 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2836 /// Simplify the expression as much as possible.
2837 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2839 SCEV::NoWrapFlags Flags) {
2840 SmallVector<const SCEV *, 4> Operands;
2841 Operands.push_back(Start);
2842 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2843 if (StepChrec->getLoop() == L) {
2844 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2845 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2848 Operands.push_back(Step);
2849 return getAddRecExpr(Operands, L, Flags);
2852 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2853 /// Simplify the expression as much as possible.
2855 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2856 const Loop *L, SCEV::NoWrapFlags Flags) {
2857 if (Operands.size() == 1) return Operands[0];
2859 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2860 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2861 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2862 "SCEVAddRecExpr operand types don't match!");
2863 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2864 assert(isLoopInvariant(Operands[i], L) &&
2865 "SCEVAddRecExpr operand is not loop-invariant!");
2868 if (Operands.back()->isZero()) {
2869 Operands.pop_back();
2870 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2873 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2874 // use that information to infer NUW and NSW flags. However, computing a
2875 // BE count requires calling getAddRecExpr, so we may not yet have a
2876 // meaningful BE count at this point (and if we don't, we'd be stuck
2877 // with a SCEVCouldNotCompute as the cached BE count).
2879 Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags);
2881 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2882 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2883 const Loop *NestedLoop = NestedAR->getLoop();
2884 if (L->contains(NestedLoop)
2885 ? (L->getLoopDepth() < NestedLoop->getLoopDepth())
2886 : (!NestedLoop->contains(L) &&
2887 DT.dominates(L->getHeader(), NestedLoop->getHeader()))) {
2888 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2889 NestedAR->op_end());
2890 Operands[0] = NestedAR->getStart();
2891 // AddRecs require their operands be loop-invariant with respect to their
2892 // loops. Don't perform this transformation if it would break this
2895 std::all_of(Operands.begin(), Operands.end(),
2896 [&](const SCEV *Op) { return isLoopInvariant(Op, L); });
2899 // Create a recurrence for the outer loop with the same step size.
2901 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2902 // inner recurrence has the same property.
2903 SCEV::NoWrapFlags OuterFlags =
2904 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2906 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2907 AllInvariant = std::all_of(
2908 NestedOperands.begin(), NestedOperands.end(),
2909 [&](const SCEV *Op) { return isLoopInvariant(Op, NestedLoop); });
2912 // Ok, both add recurrences are valid after the transformation.
2914 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2915 // the outer recurrence has the same property.
2916 SCEV::NoWrapFlags InnerFlags =
2917 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2918 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2921 // Reset Operands to its original state.
2922 Operands[0] = NestedAR;
2926 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2927 // already have one, otherwise create a new one.
2928 FoldingSetNodeID ID;
2929 ID.AddInteger(scAddRecExpr);
2930 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2931 ID.AddPointer(Operands[i]);
2935 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2937 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2938 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2939 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2940 O, Operands.size(), L);
2941 UniqueSCEVs.InsertNode(S, IP);
2943 S->setNoWrapFlags(Flags);
2948 ScalarEvolution::getGEPExpr(Type *PointeeType, const SCEV *BaseExpr,
2949 const SmallVectorImpl<const SCEV *> &IndexExprs,
2951 // getSCEV(Base)->getType() has the same address space as Base->getType()
2952 // because SCEV::getType() preserves the address space.
2953 Type *IntPtrTy = getEffectiveSCEVType(BaseExpr->getType());
2954 // FIXME(PR23527): Don't blindly transfer the inbounds flag from the GEP
2955 // instruction to its SCEV, because the Instruction may be guarded by control
2956 // flow and the no-overflow bits may not be valid for the expression in any
2957 // context. This can be fixed similarly to how these flags are handled for
2959 SCEV::NoWrapFlags Wrap = InBounds ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
2961 const SCEV *TotalOffset = getZero(IntPtrTy);
2962 // The address space is unimportant. The first thing we do on CurTy is getting
2963 // its element type.
2964 Type *CurTy = PointerType::getUnqual(PointeeType);
2965 for (const SCEV *IndexExpr : IndexExprs) {
2966 // Compute the (potentially symbolic) offset in bytes for this index.
2967 if (StructType *STy = dyn_cast<StructType>(CurTy)) {
2968 // For a struct, add the member offset.
2969 ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue();
2970 unsigned FieldNo = Index->getZExtValue();
2971 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
2973 // Add the field offset to the running total offset.
2974 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
2976 // Update CurTy to the type of the field at Index.
2977 CurTy = STy->getTypeAtIndex(Index);
2979 // Update CurTy to its element type.
2980 CurTy = cast<SequentialType>(CurTy)->getElementType();
2981 // For an array, add the element offset, explicitly scaled.
2982 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, CurTy);
2983 // Getelementptr indices are signed.
2984 IndexExpr = getTruncateOrSignExtend(IndexExpr, IntPtrTy);
2986 // Multiply the index by the element size to compute the element offset.
2987 const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, Wrap);
2989 // Add the element offset to the running total offset.
2990 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
2994 // Add the total offset from all the GEP indices to the base.
2995 return getAddExpr(BaseExpr, TotalOffset, Wrap);
2998 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
3000 SmallVector<const SCEV *, 2> Ops;
3003 return getSMaxExpr(Ops);
3007 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3008 assert(!Ops.empty() && "Cannot get empty smax!");
3009 if (Ops.size() == 1) return Ops[0];
3011 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3012 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3013 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3014 "SCEVSMaxExpr operand types don't match!");
3017 // Sort by complexity, this groups all similar expression types together.
3018 GroupByComplexity(Ops, &LI);
3020 // If there are any constants, fold them together.
3022 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3024 assert(Idx < Ops.size());
3025 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3026 // We found two constants, fold them together!
3027 ConstantInt *Fold = ConstantInt::get(getContext(),
3028 APIntOps::smax(LHSC->getValue()->getValue(),
3029 RHSC->getValue()->getValue()));
3030 Ops[0] = getConstant(Fold);
3031 Ops.erase(Ops.begin()+1); // Erase the folded element
3032 if (Ops.size() == 1) return Ops[0];
3033 LHSC = cast<SCEVConstant>(Ops[0]);
3036 // If we are left with a constant minimum-int, strip it off.
3037 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
3038 Ops.erase(Ops.begin());
3040 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
3041 // If we have an smax with a constant maximum-int, it will always be
3046 if (Ops.size() == 1) return Ops[0];
3049 // Find the first SMax
3050 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
3053 // Check to see if one of the operands is an SMax. If so, expand its operands
3054 // onto our operand list, and recurse to simplify.
3055 if (Idx < Ops.size()) {
3056 bool DeletedSMax = false;
3057 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
3058 Ops.erase(Ops.begin()+Idx);
3059 Ops.append(SMax->op_begin(), SMax->op_end());
3064 return getSMaxExpr(Ops);
3067 // Okay, check to see if the same value occurs in the operand list twice. If
3068 // so, delete one. Since we sorted the list, these values are required to
3070 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3071 // X smax Y smax Y --> X smax Y
3072 // X smax Y --> X, if X is always greater than Y
3073 if (Ops[i] == Ops[i+1] ||
3074 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
3075 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3077 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
3078 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3082 if (Ops.size() == 1) return Ops[0];
3084 assert(!Ops.empty() && "Reduced smax down to nothing!");
3086 // Okay, it looks like we really DO need an smax expr. Check to see if we
3087 // already have one, otherwise create a new one.
3088 FoldingSetNodeID ID;
3089 ID.AddInteger(scSMaxExpr);
3090 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3091 ID.AddPointer(Ops[i]);
3093 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3094 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3095 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3096 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
3098 UniqueSCEVs.InsertNode(S, IP);
3102 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
3104 SmallVector<const SCEV *, 2> Ops;
3107 return getUMaxExpr(Ops);
3111 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3112 assert(!Ops.empty() && "Cannot get empty umax!");
3113 if (Ops.size() == 1) return Ops[0];
3115 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3116 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3117 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3118 "SCEVUMaxExpr operand types don't match!");
3121 // Sort by complexity, this groups all similar expression types together.
3122 GroupByComplexity(Ops, &LI);
3124 // If there are any constants, fold them together.
3126 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3128 assert(Idx < Ops.size());
3129 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3130 // We found two constants, fold them together!
3131 ConstantInt *Fold = ConstantInt::get(getContext(),
3132 APIntOps::umax(LHSC->getValue()->getValue(),
3133 RHSC->getValue()->getValue()));
3134 Ops[0] = getConstant(Fold);
3135 Ops.erase(Ops.begin()+1); // Erase the folded element
3136 if (Ops.size() == 1) return Ops[0];
3137 LHSC = cast<SCEVConstant>(Ops[0]);
3140 // If we are left with a constant minimum-int, strip it off.
3141 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
3142 Ops.erase(Ops.begin());
3144 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
3145 // If we have an umax with a constant maximum-int, it will always be
3150 if (Ops.size() == 1) return Ops[0];
3153 // Find the first UMax
3154 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
3157 // Check to see if one of the operands is a UMax. If so, expand its operands
3158 // onto our operand list, and recurse to simplify.
3159 if (Idx < Ops.size()) {
3160 bool DeletedUMax = false;
3161 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
3162 Ops.erase(Ops.begin()+Idx);
3163 Ops.append(UMax->op_begin(), UMax->op_end());
3168 return getUMaxExpr(Ops);
3171 // Okay, check to see if the same value occurs in the operand list twice. If
3172 // so, delete one. Since we sorted the list, these values are required to
3174 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3175 // X umax Y umax Y --> X umax Y
3176 // X umax Y --> X, if X is always greater than Y
3177 if (Ops[i] == Ops[i+1] ||
3178 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
3179 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3181 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
3182 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3186 if (Ops.size() == 1) return Ops[0];
3188 assert(!Ops.empty() && "Reduced umax down to nothing!");
3190 // Okay, it looks like we really DO need a umax expr. Check to see if we
3191 // already have one, otherwise create a new one.
3192 FoldingSetNodeID ID;
3193 ID.AddInteger(scUMaxExpr);
3194 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3195 ID.AddPointer(Ops[i]);
3197 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3198 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3199 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3200 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
3202 UniqueSCEVs.InsertNode(S, IP);
3206 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
3208 // ~smax(~x, ~y) == smin(x, y).
3209 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3212 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
3214 // ~umax(~x, ~y) == umin(x, y)
3215 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3218 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
3219 // We can bypass creating a target-independent
3220 // constant expression and then folding it back into a ConstantInt.
3221 // This is just a compile-time optimization.
3222 return getConstant(IntTy, getDataLayout().getTypeAllocSize(AllocTy));
3225 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
3228 // We can bypass creating a target-independent
3229 // constant expression and then folding it back into a ConstantInt.
3230 // This is just a compile-time optimization.
3232 IntTy, getDataLayout().getStructLayout(STy)->getElementOffset(FieldNo));
3235 const SCEV *ScalarEvolution::getUnknown(Value *V) {
3236 // Don't attempt to do anything other than create a SCEVUnknown object
3237 // here. createSCEV only calls getUnknown after checking for all other
3238 // interesting possibilities, and any other code that calls getUnknown
3239 // is doing so in order to hide a value from SCEV canonicalization.
3241 FoldingSetNodeID ID;
3242 ID.AddInteger(scUnknown);
3245 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3246 assert(cast<SCEVUnknown>(S)->getValue() == V &&
3247 "Stale SCEVUnknown in uniquing map!");
3250 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3252 FirstUnknown = cast<SCEVUnknown>(S);
3253 UniqueSCEVs.InsertNode(S, IP);
3257 //===----------------------------------------------------------------------===//
3258 // Basic SCEV Analysis and PHI Idiom Recognition Code
3261 /// isSCEVable - Test if values of the given type are analyzable within
3262 /// the SCEV framework. This primarily includes integer types, and it
3263 /// can optionally include pointer types if the ScalarEvolution class
3264 /// has access to target-specific information.
3265 bool ScalarEvolution::isSCEVable(Type *Ty) const {
3266 // Integers and pointers are always SCEVable.
3267 return Ty->isIntegerTy() || Ty->isPointerTy();
3270 /// getTypeSizeInBits - Return the size in bits of the specified type,
3271 /// for which isSCEVable must return true.
3272 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3273 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3274 return getDataLayout().getTypeSizeInBits(Ty);
3277 /// getEffectiveSCEVType - Return a type with the same bitwidth as
3278 /// the given type and which represents how SCEV will treat the given
3279 /// type, for which isSCEVable must return true. For pointer types,
3280 /// this is the pointer-sized integer type.
3281 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3282 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3284 if (Ty->isIntegerTy())
3287 // The only other support type is pointer.
3288 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
3289 return getDataLayout().getIntPtrType(Ty);
3292 const SCEV *ScalarEvolution::getCouldNotCompute() {
3293 return CouldNotCompute.get();
3297 // Helper class working with SCEVTraversal to figure out if a SCEV contains
3298 // a SCEVUnknown with null value-pointer. FindInvalidSCEVUnknown::FindOne
3299 // is set iff if find such SCEVUnknown.
3301 struct FindInvalidSCEVUnknown {
3303 FindInvalidSCEVUnknown() { FindOne = false; }
3304 bool follow(const SCEV *S) {
3305 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
3309 if (!cast<SCEVUnknown>(S)->getValue())
3316 bool isDone() const { return FindOne; }
3320 bool ScalarEvolution::checkValidity(const SCEV *S) const {
3321 FindInvalidSCEVUnknown F;
3322 SCEVTraversal<FindInvalidSCEVUnknown> ST(F);
3328 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
3329 /// expression and create a new one.
3330 const SCEV *ScalarEvolution::getSCEV(Value *V) {
3331 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3333 const SCEV *S = getExistingSCEV(V);
3336 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
3341 const SCEV *ScalarEvolution::getExistingSCEV(Value *V) {
3342 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3344 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3345 if (I != ValueExprMap.end()) {
3346 const SCEV *S = I->second;
3347 if (checkValidity(S))
3349 ValueExprMap.erase(I);
3354 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
3356 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V,
3357 SCEV::NoWrapFlags Flags) {
3358 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3360 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3362 Type *Ty = V->getType();
3363 Ty = getEffectiveSCEVType(Ty);
3365 V, getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))), Flags);
3368 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
3369 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3370 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3372 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3374 Type *Ty = V->getType();
3375 Ty = getEffectiveSCEVType(Ty);
3376 const SCEV *AllOnes =
3377 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3378 return getMinusSCEV(AllOnes, V);
3381 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
3382 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3383 SCEV::NoWrapFlags Flags) {
3384 // Fast path: X - X --> 0.
3386 return getZero(LHS->getType());
3388 // We represent LHS - RHS as LHS + (-1)*RHS. This transformation
3389 // makes it so that we cannot make much use of NUW.
3390 auto AddFlags = SCEV::FlagAnyWrap;
3391 const bool RHSIsNotMinSigned =
3392 !getSignedRange(RHS).getSignedMin().isMinSignedValue();
3393 if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) {
3394 // Let M be the minimum representable signed value. Then (-1)*RHS
3395 // signed-wraps if and only if RHS is M. That can happen even for
3396 // a NSW subtraction because e.g. (-1)*M signed-wraps even though
3397 // -1 - M does not. So to transfer NSW from LHS - RHS to LHS +
3398 // (-1)*RHS, we need to prove that RHS != M.
3400 // If LHS is non-negative and we know that LHS - RHS does not
3401 // signed-wrap, then RHS cannot be M. So we can rule out signed-wrap
3402 // either by proving that RHS > M or that LHS >= 0.
3403 if (RHSIsNotMinSigned || isKnownNonNegative(LHS)) {
3404 AddFlags = SCEV::FlagNSW;
3408 // FIXME: Find a correct way to transfer NSW to (-1)*M when LHS -
3409 // RHS is NSW and LHS >= 0.
3411 // The difficulty here is that the NSW flag may have been proven
3412 // relative to a loop that is to be found in a recurrence in LHS and
3413 // not in RHS. Applying NSW to (-1)*M may then let the NSW have a
3414 // larger scope than intended.
3415 auto NegFlags = RHSIsNotMinSigned ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3417 return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags);
3420 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
3421 /// input value to the specified type. If the type must be extended, it is zero
3424 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3425 Type *SrcTy = V->getType();
3426 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3427 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3428 "Cannot truncate or zero extend with non-integer arguments!");
3429 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3430 return V; // No conversion
3431 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3432 return getTruncateExpr(V, Ty);
3433 return getZeroExtendExpr(V, Ty);
3436 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
3437 /// input value to the specified type. If the type must be extended, it is sign
3440 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3442 Type *SrcTy = V->getType();
3443 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3444 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3445 "Cannot truncate or zero extend with non-integer arguments!");
3446 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3447 return V; // No conversion
3448 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3449 return getTruncateExpr(V, Ty);
3450 return getSignExtendExpr(V, Ty);
3453 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
3454 /// input value to the specified type. If the type must be extended, it is zero
3455 /// extended. The conversion must not be narrowing.
3457 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3458 Type *SrcTy = V->getType();
3459 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3460 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3461 "Cannot noop or zero extend with non-integer arguments!");
3462 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3463 "getNoopOrZeroExtend cannot truncate!");
3464 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3465 return V; // No conversion
3466 return getZeroExtendExpr(V, Ty);
3469 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
3470 /// input value to the specified type. If the type must be extended, it is sign
3471 /// extended. The conversion must not be narrowing.
3473 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3474 Type *SrcTy = V->getType();
3475 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3476 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3477 "Cannot noop or sign extend with non-integer arguments!");
3478 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3479 "getNoopOrSignExtend cannot truncate!");
3480 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3481 return V; // No conversion
3482 return getSignExtendExpr(V, Ty);
3485 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
3486 /// the input value to the specified type. If the type must be extended,
3487 /// it is extended with unspecified bits. The conversion must not be
3490 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3491 Type *SrcTy = V->getType();
3492 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3493 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3494 "Cannot noop or any extend with non-integer arguments!");
3495 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3496 "getNoopOrAnyExtend cannot truncate!");
3497 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3498 return V; // No conversion
3499 return getAnyExtendExpr(V, Ty);
3502 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
3503 /// input value to the specified type. The conversion must not be widening.
3505 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3506 Type *SrcTy = V->getType();
3507 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3508 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3509 "Cannot truncate or noop with non-integer arguments!");
3510 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
3511 "getTruncateOrNoop cannot extend!");
3512 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3513 return V; // No conversion
3514 return getTruncateExpr(V, Ty);
3517 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
3518 /// the types using zero-extension, and then perform a umax operation
3520 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3522 const SCEV *PromotedLHS = LHS;
3523 const SCEV *PromotedRHS = RHS;
3525 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3526 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3528 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3530 return getUMaxExpr(PromotedLHS, PromotedRHS);
3533 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
3534 /// the types using zero-extension, and then perform a umin operation
3536 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3538 const SCEV *PromotedLHS = LHS;
3539 const SCEV *PromotedRHS = RHS;
3541 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3542 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3544 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3546 return getUMinExpr(PromotedLHS, PromotedRHS);
3549 /// getPointerBase - Transitively follow the chain of pointer-type operands
3550 /// until reaching a SCEV that does not have a single pointer operand. This
3551 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
3552 /// but corner cases do exist.
3553 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3554 // A pointer operand may evaluate to a nonpointer expression, such as null.
3555 if (!V->getType()->isPointerTy())
3558 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3559 return getPointerBase(Cast->getOperand());
3560 } else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3561 const SCEV *PtrOp = nullptr;
3562 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
3564 if ((*I)->getType()->isPointerTy()) {
3565 // Cannot find the base of an expression with multiple pointer operands.
3573 return getPointerBase(PtrOp);
3578 /// PushDefUseChildren - Push users of the given Instruction
3579 /// onto the given Worklist.
3581 PushDefUseChildren(Instruction *I,
3582 SmallVectorImpl<Instruction *> &Worklist) {
3583 // Push the def-use children onto the Worklist stack.
3584 for (User *U : I->users())
3585 Worklist.push_back(cast<Instruction>(U));
3588 /// ForgetSymbolicValue - This looks up computed SCEV values for all
3589 /// instructions that depend on the given instruction and removes them from
3590 /// the ValueExprMapType map if they reference SymName. This is used during PHI
3593 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3594 SmallVector<Instruction *, 16> Worklist;
3595 PushDefUseChildren(PN, Worklist);
3597 SmallPtrSet<Instruction *, 8> Visited;
3599 while (!Worklist.empty()) {
3600 Instruction *I = Worklist.pop_back_val();
3601 if (!Visited.insert(I).second)
3604 auto It = ValueExprMap.find_as(static_cast<Value *>(I));
3605 if (It != ValueExprMap.end()) {
3606 const SCEV *Old = It->second;
3608 // Short-circuit the def-use traversal if the symbolic name
3609 // ceases to appear in expressions.
3610 if (Old != SymName && !hasOperand(Old, SymName))
3613 // SCEVUnknown for a PHI either means that it has an unrecognized
3614 // structure, it's a PHI that's in the progress of being computed
3615 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3616 // additional loop trip count information isn't going to change anything.
3617 // In the second case, createNodeForPHI will perform the necessary
3618 // updates on its own when it gets to that point. In the third, we do
3619 // want to forget the SCEVUnknown.
3620 if (!isa<PHINode>(I) ||
3621 !isa<SCEVUnknown>(Old) ||
3622 (I != PN && Old == SymName)) {
3623 forgetMemoizedResults(Old);
3624 ValueExprMap.erase(It);
3628 PushDefUseChildren(I, Worklist);
3632 const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
3633 const Loop *L = LI.getLoopFor(PN->getParent());
3634 if (!L || L->getHeader() != PN->getParent())
3637 // The loop may have multiple entrances or multiple exits; we can analyze
3638 // this phi as an addrec if it has a unique entry value and a unique
3640 Value *BEValueV = nullptr, *StartValueV = nullptr;
3641 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
3642 Value *V = PN->getIncomingValue(i);
3643 if (L->contains(PN->getIncomingBlock(i))) {
3646 } else if (BEValueV != V) {
3650 } else if (!StartValueV) {
3652 } else if (StartValueV != V) {
3653 StartValueV = nullptr;
3657 if (BEValueV && StartValueV) {
3658 // While we are analyzing this PHI node, handle its value symbolically.
3659 const SCEV *SymbolicName = getUnknown(PN);
3660 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&
3661 "PHI node already processed?");
3662 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
3664 // Using this symbolic name for the PHI, analyze the value coming around
3666 const SCEV *BEValue = getSCEV(BEValueV);
3668 // NOTE: If BEValue is loop invariant, we know that the PHI node just
3669 // has a special value for the first iteration of the loop.
3671 // If the value coming around the backedge is an add with the symbolic
3672 // value we just inserted, then we found a simple induction variable!
3673 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
3674 // If there is a single occurrence of the symbolic value, replace it
3675 // with a recurrence.
3676 unsigned FoundIndex = Add->getNumOperands();
3677 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3678 if (Add->getOperand(i) == SymbolicName)
3679 if (FoundIndex == e) {
3684 if (FoundIndex != Add->getNumOperands()) {
3685 // Create an add with everything but the specified operand.
3686 SmallVector<const SCEV *, 8> Ops;
3687 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3688 if (i != FoundIndex)
3689 Ops.push_back(Add->getOperand(i));
3690 const SCEV *Accum = getAddExpr(Ops);
3692 // This is not a valid addrec if the step amount is varying each
3693 // loop iteration, but is not itself an addrec in this loop.
3694 if (isLoopInvariant(Accum, L) ||
3695 (isa<SCEVAddRecExpr>(Accum) &&
3696 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
3697 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3699 // If the increment doesn't overflow, then neither the addrec nor
3700 // the post-increment will overflow.
3701 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
3702 if (OBO->getOperand(0) == PN) {
3703 if (OBO->hasNoUnsignedWrap())
3704 Flags = setFlags(Flags, SCEV::FlagNUW);
3705 if (OBO->hasNoSignedWrap())
3706 Flags = setFlags(Flags, SCEV::FlagNSW);
3708 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
3709 // If the increment is an inbounds GEP, then we know the address
3710 // space cannot be wrapped around. We cannot make any guarantee
3711 // about signed or unsigned overflow because pointers are
3712 // unsigned but we may have a negative index from the base
3713 // pointer. We can guarantee that no unsigned wrap occurs if the
3714 // indices form a positive value.
3715 if (GEP->isInBounds() && GEP->getOperand(0) == PN) {
3716 Flags = setFlags(Flags, SCEV::FlagNW);
3718 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
3719 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
3720 Flags = setFlags(Flags, SCEV::FlagNUW);
3723 // We cannot transfer nuw and nsw flags from subtraction
3724 // operations -- sub nuw X, Y is not the same as add nuw X, -Y
3728 const SCEV *StartVal = getSCEV(StartValueV);
3729 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
3731 // Since the no-wrap flags are on the increment, they apply to the
3732 // post-incremented value as well.
3733 if (isLoopInvariant(Accum, L))
3734 (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
3736 // Okay, for the entire analysis of this edge we assumed the PHI
3737 // to be symbolic. We now need to go back and purge all of the
3738 // entries for the scalars that use the symbolic expression.
3739 ForgetSymbolicName(PN, SymbolicName);
3740 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3744 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(BEValue)) {
3745 // Otherwise, this could be a loop like this:
3746 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
3747 // In this case, j = {1,+,1} and BEValue is j.
3748 // Because the other in-value of i (0) fits the evolution of BEValue
3749 // i really is an addrec evolution.
3750 if (AddRec->getLoop() == L && AddRec->isAffine()) {
3751 const SCEV *StartVal = getSCEV(StartValueV);
3753 // If StartVal = j.start - j.stride, we can use StartVal as the
3754 // initial step of the addrec evolution.
3756 getMinusSCEV(AddRec->getOperand(0), AddRec->getOperand(1))) {
3757 // FIXME: For constant StartVal, we should be able to infer
3759 const SCEV *PHISCEV = getAddRecExpr(StartVal, AddRec->getOperand(1),
3760 L, SCEV::FlagAnyWrap);
3762 // Okay, for the entire analysis of this edge we assumed the PHI
3763 // to be symbolic. We now need to go back and purge all of the
3764 // entries for the scalars that use the symbolic expression.
3765 ForgetSymbolicName(PN, SymbolicName);
3766 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3776 // Checks if the SCEV S is available at BB. S is considered available at BB
3777 // if S can be materialized at BB without introducing a fault.
3778 static bool IsAvailableOnEntry(const Loop *L, DominatorTree &DT, const SCEV *S,
3780 struct CheckAvailable {
3781 bool TraversalDone = false;
3782 bool Available = true;
3784 const Loop *L = nullptr; // The loop BB is in (can be nullptr)
3785 BasicBlock *BB = nullptr;
3788 CheckAvailable(const Loop *L, BasicBlock *BB, DominatorTree &DT)
3789 : L(L), BB(BB), DT(DT) {}
3791 bool setUnavailable() {
3792 TraversalDone = true;
3797 bool follow(const SCEV *S) {
3798 switch (S->getSCEVType()) {
3799 case scConstant: case scTruncate: case scZeroExtend: case scSignExtend:
3800 case scAddExpr: case scMulExpr: case scUMaxExpr: case scSMaxExpr:
3801 // These expressions are available if their operand(s) is/are.
3804 case scAddRecExpr: {
3805 // We allow add recurrences that are on the loop BB is in, or some
3806 // outer loop. This guarantees availability because the value of the
3807 // add recurrence at BB is simply the "current" value of the induction
3808 // variable. We can relax this in the future; for instance an add
3809 // recurrence on a sibling dominating loop is also available at BB.
3810 const auto *ARLoop = cast<SCEVAddRecExpr>(S)->getLoop();
3811 if (L && (ARLoop == L || ARLoop->contains(L)))
3814 return setUnavailable();
3818 // For SCEVUnknown, we check for simple dominance.
3819 const auto *SU = cast<SCEVUnknown>(S);
3820 Value *V = SU->getValue();
3822 if (isa<Argument>(V))
3825 if (isa<Instruction>(V) && DT.dominates(cast<Instruction>(V), BB))
3828 return setUnavailable();
3832 case scCouldNotCompute:
3833 // We do not try to smart about these at all.
3834 return setUnavailable();
3836 llvm_unreachable("switch should be fully covered!");
3839 bool isDone() { return TraversalDone; }
3842 CheckAvailable CA(L, BB, DT);
3843 SCEVTraversal<CheckAvailable> ST(CA);
3846 return CA.Available;
3849 // Try to match a control flow sequence that branches out at BI and merges back
3850 // at Merge into a "C ? LHS : RHS" select pattern. Return true on a successful
3852 static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge,
3853 Value *&C, Value *&LHS, Value *&RHS) {
3854 C = BI->getCondition();
3856 BasicBlockEdge LeftEdge(BI->getParent(), BI->getSuccessor(0));
3857 BasicBlockEdge RightEdge(BI->getParent(), BI->getSuccessor(1));
3859 if (!LeftEdge.isSingleEdge())
3862 assert(RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()");
3864 Use &LeftUse = Merge->getOperandUse(0);
3865 Use &RightUse = Merge->getOperandUse(1);
3867 if (DT.dominates(LeftEdge, LeftUse) && DT.dominates(RightEdge, RightUse)) {
3873 if (DT.dominates(LeftEdge, RightUse) && DT.dominates(RightEdge, LeftUse)) {
3882 const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
3883 if (PN->getNumIncomingValues() == 2) {
3884 const Loop *L = LI.getLoopFor(PN->getParent());
3888 // br %cond, label %left, label %right
3894 // V = phi [ %x, %left ], [ %y, %right ]
3896 // as "select %cond, %x, %y"
3898 BasicBlock *IDom = DT[PN->getParent()]->getIDom()->getBlock();
3899 assert(IDom && "At least the entry block should dominate PN");
3901 auto *BI = dyn_cast<BranchInst>(IDom->getTerminator());
3902 Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr;
3904 if (BI && BI->isConditional() &&
3905 BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
3906 IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
3907 IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent()))
3908 return createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
3914 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
3915 if (const SCEV *S = createAddRecFromPHI(PN))
3918 if (const SCEV *S = createNodeFromSelectLikePHI(PN))
3921 // If the PHI has a single incoming value, follow that value, unless the
3922 // PHI's incoming blocks are in a different loop, in which case doing so
3923 // risks breaking LCSSA form. Instcombine would normally zap these, but
3924 // it doesn't have DominatorTree information, so it may miss cases.
3925 if (Value *V = SimplifyInstruction(PN, getDataLayout(), &TLI, &DT, &AC))
3926 if (LI.replacementPreservesLCSSAForm(PN, V))
3929 // If it's not a loop phi, we can't handle it yet.
3930 return getUnknown(PN);
3933 const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
3937 // Handle "constant" branch or select. This can occur for instance when a
3938 // loop pass transforms an inner loop and moves on to process the outer loop.
3939 if (auto *CI = dyn_cast<ConstantInt>(Cond))
3940 return getSCEV(CI->isOne() ? TrueVal : FalseVal);
3942 // Try to match some simple smax or umax patterns.
3943 auto *ICI = dyn_cast<ICmpInst>(Cond);
3945 return getUnknown(I);
3947 Value *LHS = ICI->getOperand(0);
3948 Value *RHS = ICI->getOperand(1);
3950 switch (ICI->getPredicate()) {
3951 case ICmpInst::ICMP_SLT:
3952 case ICmpInst::ICMP_SLE:
3953 std::swap(LHS, RHS);
3955 case ICmpInst::ICMP_SGT:
3956 case ICmpInst::ICMP_SGE:
3957 // a >s b ? a+x : b+x -> smax(a, b)+x
3958 // a >s b ? b+x : a+x -> smin(a, b)+x
3959 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
3960 const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), I->getType());
3961 const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), I->getType());
3962 const SCEV *LA = getSCEV(TrueVal);
3963 const SCEV *RA = getSCEV(FalseVal);
3964 const SCEV *LDiff = getMinusSCEV(LA, LS);
3965 const SCEV *RDiff = getMinusSCEV(RA, RS);
3967 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3968 LDiff = getMinusSCEV(LA, RS);
3969 RDiff = getMinusSCEV(RA, LS);
3971 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3974 case ICmpInst::ICMP_ULT:
3975 case ICmpInst::ICMP_ULE:
3976 std::swap(LHS, RHS);
3978 case ICmpInst::ICMP_UGT:
3979 case ICmpInst::ICMP_UGE:
3980 // a >u b ? a+x : b+x -> umax(a, b)+x
3981 // a >u b ? b+x : a+x -> umin(a, b)+x
3982 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
3983 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
3984 const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), I->getType());
3985 const SCEV *LA = getSCEV(TrueVal);
3986 const SCEV *RA = getSCEV(FalseVal);
3987 const SCEV *LDiff = getMinusSCEV(LA, LS);
3988 const SCEV *RDiff = getMinusSCEV(RA, RS);
3990 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3991 LDiff = getMinusSCEV(LA, RS);
3992 RDiff = getMinusSCEV(RA, LS);
3994 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3997 case ICmpInst::ICMP_NE:
3998 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3999 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4000 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4001 const SCEV *One = getOne(I->getType());
4002 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4003 const SCEV *LA = getSCEV(TrueVal);
4004 const SCEV *RA = getSCEV(FalseVal);
4005 const SCEV *LDiff = getMinusSCEV(LA, LS);
4006 const SCEV *RDiff = getMinusSCEV(RA, One);
4008 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4011 case ICmpInst::ICMP_EQ:
4012 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4013 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4014 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4015 const SCEV *One = getOne(I->getType());
4016 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4017 const SCEV *LA = getSCEV(TrueVal);
4018 const SCEV *RA = getSCEV(FalseVal);
4019 const SCEV *LDiff = getMinusSCEV(LA, One);
4020 const SCEV *RDiff = getMinusSCEV(RA, LS);
4022 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4029 return getUnknown(I);
4032 /// createNodeForGEP - Expand GEP instructions into add and multiply
4033 /// operations. This allows them to be analyzed by regular SCEV code.
4035 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
4036 Value *Base = GEP->getOperand(0);
4037 // Don't attempt to analyze GEPs over unsized objects.
4038 if (!Base->getType()->getPointerElementType()->isSized())
4039 return getUnknown(GEP);
4041 SmallVector<const SCEV *, 4> IndexExprs;
4042 for (auto Index = GEP->idx_begin(); Index != GEP->idx_end(); ++Index)
4043 IndexExprs.push_back(getSCEV(*Index));
4044 return getGEPExpr(GEP->getSourceElementType(), getSCEV(Base), IndexExprs,
4048 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
4049 /// guaranteed to end in (at every loop iteration). It is, at the same time,
4050 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
4051 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
4053 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
4054 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4055 return C->getValue()->getValue().countTrailingZeros();
4057 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
4058 return std::min(GetMinTrailingZeros(T->getOperand()),
4059 (uint32_t)getTypeSizeInBits(T->getType()));
4061 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
4062 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4063 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
4064 getTypeSizeInBits(E->getType()) : OpRes;
4067 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
4068 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4069 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
4070 getTypeSizeInBits(E->getType()) : OpRes;
4073 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
4074 // The result is the min of all operands results.
4075 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4076 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4077 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4081 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
4082 // The result is the sum of all operands results.
4083 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
4084 uint32_t BitWidth = getTypeSizeInBits(M->getType());
4085 for (unsigned i = 1, e = M->getNumOperands();
4086 SumOpRes != BitWidth && i != e; ++i)
4087 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
4092 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
4093 // The result is the min of all operands results.
4094 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4095 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4096 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4100 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
4101 // The result is the min of all operands results.
4102 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4103 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4104 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4108 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
4109 // The result is the min of all operands results.
4110 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4111 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4112 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4116 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4117 // For a SCEVUnknown, ask ValueTracking.
4118 unsigned BitWidth = getTypeSizeInBits(U->getType());
4119 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4120 computeKnownBits(U->getValue(), Zeros, Ones, getDataLayout(), 0, &AC,
4122 return Zeros.countTrailingOnes();
4129 /// GetRangeFromMetadata - Helper method to assign a range to V from
4130 /// metadata present in the IR.
4131 static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
4132 if (Instruction *I = dyn_cast<Instruction>(V))
4133 if (MDNode *MD = I->getMetadata(LLVMContext::MD_range))
4134 return getConstantRangeFromMetadata(*MD);
4139 /// getRange - Determine the range for a particular SCEV. If SignHint is
4140 /// HINT_RANGE_UNSIGNED (resp. HINT_RANGE_SIGNED) then getRange prefers ranges
4141 /// with a "cleaner" unsigned (resp. signed) representation.
4144 ScalarEvolution::getRange(const SCEV *S,
4145 ScalarEvolution::RangeSignHint SignHint) {
4146 DenseMap<const SCEV *, ConstantRange> &Cache =
4147 SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED ? UnsignedRanges
4150 // See if we've computed this range already.
4151 DenseMap<const SCEV *, ConstantRange>::iterator I = Cache.find(S);
4152 if (I != Cache.end())
4155 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4156 return setRange(C, SignHint, ConstantRange(C->getValue()->getValue()));
4158 unsigned BitWidth = getTypeSizeInBits(S->getType());
4159 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
4161 // If the value has known zeros, the maximum value will have those known zeros
4163 uint32_t TZ = GetMinTrailingZeros(S);
4165 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED)
4166 ConservativeResult =
4167 ConstantRange(APInt::getMinValue(BitWidth),
4168 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
4170 ConservativeResult = ConstantRange(
4171 APInt::getSignedMinValue(BitWidth),
4172 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
4175 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
4176 ConstantRange X = getRange(Add->getOperand(0), SignHint);
4177 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
4178 X = X.add(getRange(Add->getOperand(i), SignHint));
4179 return setRange(Add, SignHint, ConservativeResult.intersectWith(X));
4182 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
4183 ConstantRange X = getRange(Mul->getOperand(0), SignHint);
4184 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
4185 X = X.multiply(getRange(Mul->getOperand(i), SignHint));
4186 return setRange(Mul, SignHint, ConservativeResult.intersectWith(X));
4189 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
4190 ConstantRange X = getRange(SMax->getOperand(0), SignHint);
4191 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
4192 X = X.smax(getRange(SMax->getOperand(i), SignHint));
4193 return setRange(SMax, SignHint, ConservativeResult.intersectWith(X));
4196 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
4197 ConstantRange X = getRange(UMax->getOperand(0), SignHint);
4198 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
4199 X = X.umax(getRange(UMax->getOperand(i), SignHint));
4200 return setRange(UMax, SignHint, ConservativeResult.intersectWith(X));
4203 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
4204 ConstantRange X = getRange(UDiv->getLHS(), SignHint);
4205 ConstantRange Y = getRange(UDiv->getRHS(), SignHint);
4206 return setRange(UDiv, SignHint,
4207 ConservativeResult.intersectWith(X.udiv(Y)));
4210 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
4211 ConstantRange X = getRange(ZExt->getOperand(), SignHint);
4212 return setRange(ZExt, SignHint,
4213 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
4216 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
4217 ConstantRange X = getRange(SExt->getOperand(), SignHint);
4218 return setRange(SExt, SignHint,
4219 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
4222 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
4223 ConstantRange X = getRange(Trunc->getOperand(), SignHint);
4224 return setRange(Trunc, SignHint,
4225 ConservativeResult.intersectWith(X.truncate(BitWidth)));
4228 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
4229 // If there's no unsigned wrap, the value will never be less than its
4231 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
4232 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
4233 if (!C->getValue()->isZero())
4234 ConservativeResult =
4235 ConservativeResult.intersectWith(
4236 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
4238 // If there's no signed wrap, and all the operands have the same sign or
4239 // zero, the value won't ever change sign.
4240 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
4241 bool AllNonNeg = true;
4242 bool AllNonPos = true;
4243 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4244 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
4245 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
4248 ConservativeResult = ConservativeResult.intersectWith(
4249 ConstantRange(APInt(BitWidth, 0),
4250 APInt::getSignedMinValue(BitWidth)));
4252 ConservativeResult = ConservativeResult.intersectWith(
4253 ConstantRange(APInt::getSignedMinValue(BitWidth),
4254 APInt(BitWidth, 1)));
4257 // TODO: non-affine addrec
4258 if (AddRec->isAffine()) {
4259 Type *Ty = AddRec->getType();
4260 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
4261 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
4262 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
4264 // Check for overflow. This must be done with ConstantRange arithmetic
4265 // because we could be called from within the ScalarEvolution overflow
4268 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
4269 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
4270 ConstantRange ZExtMaxBECountRange =
4271 MaxBECountRange.zextOrTrunc(BitWidth * 2 + 1);
4273 const SCEV *Start = AddRec->getStart();
4274 const SCEV *Step = AddRec->getStepRecurrence(*this);
4275 ConstantRange StepSRange = getSignedRange(Step);
4276 ConstantRange SExtStepSRange = StepSRange.sextOrTrunc(BitWidth * 2 + 1);
4278 ConstantRange StartURange = getUnsignedRange(Start);
4279 ConstantRange EndURange =
4280 StartURange.add(MaxBECountRange.multiply(StepSRange));
4282 // Check for unsigned overflow.
4283 ConstantRange ZExtStartURange =
4284 StartURange.zextOrTrunc(BitWidth * 2 + 1);
4285 ConstantRange ZExtEndURange = EndURange.zextOrTrunc(BitWidth * 2 + 1);
4286 if (ZExtStartURange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
4288 APInt Min = APIntOps::umin(StartURange.getUnsignedMin(),
4289 EndURange.getUnsignedMin());
4290 APInt Max = APIntOps::umax(StartURange.getUnsignedMax(),
4291 EndURange.getUnsignedMax());
4292 bool IsFullRange = Min.isMinValue() && Max.isMaxValue();
4294 ConservativeResult =
4295 ConservativeResult.intersectWith(ConstantRange(Min, Max + 1));
4298 ConstantRange StartSRange = getSignedRange(Start);
4299 ConstantRange EndSRange =
4300 StartSRange.add(MaxBECountRange.multiply(StepSRange));
4302 // Check for signed overflow. This must be done with ConstantRange
4303 // arithmetic because we could be called from within the ScalarEvolution
4304 // overflow checking code.
4305 ConstantRange SExtStartSRange =
4306 StartSRange.sextOrTrunc(BitWidth * 2 + 1);
4307 ConstantRange SExtEndSRange = EndSRange.sextOrTrunc(BitWidth * 2 + 1);
4308 if (SExtStartSRange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
4310 APInt Min = APIntOps::smin(StartSRange.getSignedMin(),
4311 EndSRange.getSignedMin());
4312 APInt Max = APIntOps::smax(StartSRange.getSignedMax(),
4313 EndSRange.getSignedMax());
4314 bool IsFullRange = Min.isMinSignedValue() && Max.isMaxSignedValue();
4316 ConservativeResult =
4317 ConservativeResult.intersectWith(ConstantRange(Min, Max + 1));
4322 return setRange(AddRec, SignHint, ConservativeResult);
4325 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4326 // Check if the IR explicitly contains !range metadata.
4327 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
4328 if (MDRange.hasValue())
4329 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
4331 // Split here to avoid paying the compile-time cost of calling both
4332 // computeKnownBits and ComputeNumSignBits. This restriction can be lifted
4334 const DataLayout &DL = getDataLayout();
4335 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) {
4336 // For a SCEVUnknown, ask ValueTracking.
4337 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4338 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, &AC, nullptr, &DT);
4339 if (Ones != ~Zeros + 1)
4340 ConservativeResult =
4341 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
4343 assert(SignHint == ScalarEvolution::HINT_RANGE_SIGNED &&
4344 "generalize as needed!");
4345 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
4347 ConservativeResult = ConservativeResult.intersectWith(
4348 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
4349 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1) + 1));
4352 return setRange(U, SignHint, ConservativeResult);
4355 return setRange(S, SignHint, ConservativeResult);
4358 SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) {
4359 if (isa<ConstantExpr>(V)) return SCEV::FlagAnyWrap;
4360 const BinaryOperator *BinOp = cast<BinaryOperator>(V);
4362 // Return early if there are no flags to propagate to the SCEV.
4363 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
4364 if (BinOp->hasNoUnsignedWrap())
4365 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
4366 if (BinOp->hasNoSignedWrap())
4367 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
4368 if (Flags == SCEV::FlagAnyWrap) {
4369 return SCEV::FlagAnyWrap;
4372 // Here we check that BinOp is in the header of the innermost loop
4373 // containing BinOp, since we only deal with instructions in the loop
4374 // header. The actual loop we need to check later will come from an add
4375 // recurrence, but getting that requires computing the SCEV of the operands,
4376 // which can be expensive. This check we can do cheaply to rule out some
4378 Loop *innermostContainingLoop = LI.getLoopFor(BinOp->getParent());
4379 if (innermostContainingLoop == nullptr ||
4380 innermostContainingLoop->getHeader() != BinOp->getParent())
4381 return SCEV::FlagAnyWrap;
4383 // Only proceed if we can prove that BinOp does not yield poison.
4384 if (!isKnownNotFullPoison(BinOp)) return SCEV::FlagAnyWrap;
4386 // At this point we know that if V is executed, then it does not wrap
4387 // according to at least one of NSW or NUW. If V is not executed, then we do
4388 // not know if the calculation that V represents would wrap. Multiple
4389 // instructions can map to the same SCEV. If we apply NSW or NUW from V to
4390 // the SCEV, we must guarantee no wrapping for that SCEV also when it is
4391 // derived from other instructions that map to the same SCEV. We cannot make
4392 // that guarantee for cases where V is not executed. So we need to find the
4393 // loop that V is considered in relation to and prove that V is executed for
4394 // every iteration of that loop. That implies that the value that V
4395 // calculates does not wrap anywhere in the loop, so then we can apply the
4396 // flags to the SCEV.
4398 // We check isLoopInvariant to disambiguate in case we are adding two
4399 // recurrences from different loops, so that we know which loop to prove
4400 // that V is executed in.
4401 for (int OpIndex = 0; OpIndex < 2; ++OpIndex) {
4402 const SCEV *Op = getSCEV(BinOp->getOperand(OpIndex));
4403 if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
4404 const int OtherOpIndex = 1 - OpIndex;
4405 const SCEV *OtherOp = getSCEV(BinOp->getOperand(OtherOpIndex));
4406 if (isLoopInvariant(OtherOp, AddRec->getLoop()) &&
4407 isGuaranteedToExecuteForEveryIteration(BinOp, AddRec->getLoop()))
4411 return SCEV::FlagAnyWrap;
4414 /// createSCEV - We know that there is no SCEV for the specified value. Analyze
4417 const SCEV *ScalarEvolution::createSCEV(Value *V) {
4418 if (!isSCEVable(V->getType()))
4419 return getUnknown(V);
4421 unsigned Opcode = Instruction::UserOp1;
4422 if (Instruction *I = dyn_cast<Instruction>(V)) {
4423 Opcode = I->getOpcode();
4425 // Don't attempt to analyze instructions in blocks that aren't
4426 // reachable. Such instructions don't matter, and they aren't required
4427 // to obey basic rules for definitions dominating uses which this
4428 // analysis depends on.
4429 if (!DT.isReachableFromEntry(I->getParent()))
4430 return getUnknown(V);
4431 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
4432 Opcode = CE->getOpcode();
4433 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
4434 return getConstant(CI);
4435 else if (isa<ConstantPointerNull>(V))
4436 return getZero(V->getType());
4437 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
4438 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
4440 return getUnknown(V);
4442 Operator *U = cast<Operator>(V);
4444 case Instruction::Add: {
4445 // The simple thing to do would be to just call getSCEV on both operands
4446 // and call getAddExpr with the result. However if we're looking at a
4447 // bunch of things all added together, this can be quite inefficient,
4448 // because it leads to N-1 getAddExpr calls for N ultimate operands.
4449 // Instead, gather up all the operands and make a single getAddExpr call.
4450 // LLVM IR canonical form means we need only traverse the left operands.
4451 SmallVector<const SCEV *, 4> AddOps;
4452 for (Value *Op = U;; Op = U->getOperand(0)) {
4453 U = dyn_cast<Operator>(Op);
4454 unsigned Opcode = U ? U->getOpcode() : 0;
4455 if (!U || (Opcode != Instruction::Add && Opcode != Instruction::Sub)) {
4456 assert(Op != V && "V should be an add");
4457 AddOps.push_back(getSCEV(Op));
4461 if (auto *OpSCEV = getExistingSCEV(U)) {
4462 AddOps.push_back(OpSCEV);
4466 // If a NUW or NSW flag can be applied to the SCEV for this
4467 // addition, then compute the SCEV for this addition by itself
4468 // with a separate call to getAddExpr. We need to do that
4469 // instead of pushing the operands of the addition onto AddOps,
4470 // since the flags are only known to apply to this particular
4471 // addition - they may not apply to other additions that can be
4472 // formed with operands from AddOps.
4473 const SCEV *RHS = getSCEV(U->getOperand(1));
4474 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(U);
4475 if (Flags != SCEV::FlagAnyWrap) {
4476 const SCEV *LHS = getSCEV(U->getOperand(0));
4477 if (Opcode == Instruction::Sub)
4478 AddOps.push_back(getMinusSCEV(LHS, RHS, Flags));
4480 AddOps.push_back(getAddExpr(LHS, RHS, Flags));
4484 if (Opcode == Instruction::Sub)
4485 AddOps.push_back(getNegativeSCEV(RHS));
4487 AddOps.push_back(RHS);
4489 return getAddExpr(AddOps);
4492 case Instruction::Mul: {
4493 SmallVector<const SCEV *, 4> MulOps;
4494 for (Value *Op = U;; Op = U->getOperand(0)) {
4495 U = dyn_cast<Operator>(Op);
4496 if (!U || U->getOpcode() != Instruction::Mul) {
4497 assert(Op != V && "V should be a mul");
4498 MulOps.push_back(getSCEV(Op));
4502 if (auto *OpSCEV = getExistingSCEV(U)) {
4503 MulOps.push_back(OpSCEV);
4507 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(U);
4508 if (Flags != SCEV::FlagAnyWrap) {
4509 MulOps.push_back(getMulExpr(getSCEV(U->getOperand(0)),
4510 getSCEV(U->getOperand(1)), Flags));
4514 MulOps.push_back(getSCEV(U->getOperand(1)));
4516 return getMulExpr(MulOps);
4518 case Instruction::UDiv:
4519 return getUDivExpr(getSCEV(U->getOperand(0)),
4520 getSCEV(U->getOperand(1)));
4521 case Instruction::Sub:
4522 return getMinusSCEV(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)),
4523 getNoWrapFlagsFromUB(U));
4524 case Instruction::And:
4525 // For an expression like x&255 that merely masks off the high bits,
4526 // use zext(trunc(x)) as the SCEV expression.
4527 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4528 if (CI->isNullValue())
4529 return getSCEV(U->getOperand(1));
4530 if (CI->isAllOnesValue())
4531 return getSCEV(U->getOperand(0));
4532 const APInt &A = CI->getValue();
4534 // Instcombine's ShrinkDemandedConstant may strip bits out of
4535 // constants, obscuring what would otherwise be a low-bits mask.
4536 // Use computeKnownBits to compute what ShrinkDemandedConstant
4537 // knew about to reconstruct a low-bits mask value.
4538 unsigned LZ = A.countLeadingZeros();
4539 unsigned TZ = A.countTrailingZeros();
4540 unsigned BitWidth = A.getBitWidth();
4541 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4542 computeKnownBits(U->getOperand(0), KnownZero, KnownOne, getDataLayout(),
4543 0, &AC, nullptr, &DT);
4545 APInt EffectiveMask =
4546 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
4547 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
4548 const SCEV *MulCount = getConstant(
4549 ConstantInt::get(getContext(), APInt::getOneBitSet(BitWidth, TZ)));
4553 getUDivExactExpr(getSCEV(U->getOperand(0)), MulCount),
4554 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
4561 case Instruction::Or:
4562 // If the RHS of the Or is a constant, we may have something like:
4563 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
4564 // optimizations will transparently handle this case.
4566 // In order for this transformation to be safe, the LHS must be of the
4567 // form X*(2^n) and the Or constant must be less than 2^n.
4568 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4569 const SCEV *LHS = getSCEV(U->getOperand(0));
4570 const APInt &CIVal = CI->getValue();
4571 if (GetMinTrailingZeros(LHS) >=
4572 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
4573 // Build a plain add SCEV.
4574 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
4575 // If the LHS of the add was an addrec and it has no-wrap flags,
4576 // transfer the no-wrap flags, since an or won't introduce a wrap.
4577 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
4578 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
4579 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
4580 OldAR->getNoWrapFlags());
4586 case Instruction::Xor:
4587 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4588 // If the RHS of the xor is a signbit, then this is just an add.
4589 // Instcombine turns add of signbit into xor as a strength reduction step.
4590 if (CI->getValue().isSignBit())
4591 return getAddExpr(getSCEV(U->getOperand(0)),
4592 getSCEV(U->getOperand(1)));
4594 // If the RHS of xor is -1, then this is a not operation.
4595 if (CI->isAllOnesValue())
4596 return getNotSCEV(getSCEV(U->getOperand(0)));
4598 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
4599 // This is a variant of the check for xor with -1, and it handles
4600 // the case where instcombine has trimmed non-demanded bits out
4601 // of an xor with -1.
4602 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
4603 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
4604 if (BO->getOpcode() == Instruction::And &&
4605 LCI->getValue() == CI->getValue())
4606 if (const SCEVZeroExtendExpr *Z =
4607 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
4608 Type *UTy = U->getType();
4609 const SCEV *Z0 = Z->getOperand();
4610 Type *Z0Ty = Z0->getType();
4611 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
4613 // If C is a low-bits mask, the zero extend is serving to
4614 // mask off the high bits. Complement the operand and
4615 // re-apply the zext.
4616 if (APIntOps::isMask(Z0TySize, CI->getValue()))
4617 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
4619 // If C is a single bit, it may be in the sign-bit position
4620 // before the zero-extend. In this case, represent the xor
4621 // using an add, which is equivalent, and re-apply the zext.
4622 APInt Trunc = CI->getValue().trunc(Z0TySize);
4623 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
4625 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
4631 case Instruction::Shl:
4632 // Turn shift left of a constant amount into a multiply.
4633 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4634 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4636 // If the shift count is not less than the bitwidth, the result of
4637 // the shift is undefined. Don't try to analyze it, because the
4638 // resolution chosen here may differ from the resolution chosen in
4639 // other parts of the compiler.
4640 if (SA->getValue().uge(BitWidth))
4643 // It is currently not resolved how to interpret NSW for left
4644 // shift by BitWidth - 1, so we avoid applying flags in that
4645 // case. Remove this check (or this comment) once the situation
4647 // http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html
4648 // and http://reviews.llvm.org/D8890 .
4649 auto Flags = SCEV::FlagAnyWrap;
4650 if (SA->getValue().ult(BitWidth - 1)) Flags = getNoWrapFlagsFromUB(U);
4652 Constant *X = ConstantInt::get(getContext(),
4653 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4654 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X), Flags);
4658 case Instruction::LShr:
4659 // Turn logical shift right of a constant into a unsigned divide.
4660 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4661 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4663 // If the shift count is not less than the bitwidth, the result of
4664 // the shift is undefined. Don't try to analyze it, because the
4665 // resolution chosen here may differ from the resolution chosen in
4666 // other parts of the compiler.
4667 if (SA->getValue().uge(BitWidth))
4670 Constant *X = ConstantInt::get(getContext(),
4671 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4672 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4676 case Instruction::AShr:
4677 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
4678 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
4679 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
4680 if (L->getOpcode() == Instruction::Shl &&
4681 L->getOperand(1) == U->getOperand(1)) {
4682 uint64_t BitWidth = getTypeSizeInBits(U->getType());
4684 // If the shift count is not less than the bitwidth, the result of
4685 // the shift is undefined. Don't try to analyze it, because the
4686 // resolution chosen here may differ from the resolution chosen in
4687 // other parts of the compiler.
4688 if (CI->getValue().uge(BitWidth))
4691 uint64_t Amt = BitWidth - CI->getZExtValue();
4692 if (Amt == BitWidth)
4693 return getSCEV(L->getOperand(0)); // shift by zero --> noop
4695 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
4696 IntegerType::get(getContext(),
4702 case Instruction::Trunc:
4703 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
4705 case Instruction::ZExt:
4706 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4708 case Instruction::SExt:
4709 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4711 case Instruction::BitCast:
4712 // BitCasts are no-op casts so we just eliminate the cast.
4713 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
4714 return getSCEV(U->getOperand(0));
4717 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
4718 // lead to pointer expressions which cannot safely be expanded to GEPs,
4719 // because ScalarEvolution doesn't respect the GEP aliasing rules when
4720 // simplifying integer expressions.
4722 case Instruction::GetElementPtr:
4723 return createNodeForGEP(cast<GEPOperator>(U));
4725 case Instruction::PHI:
4726 return createNodeForPHI(cast<PHINode>(U));
4728 case Instruction::Select:
4729 // U can also be a select constant expr, which let fall through. Since
4730 // createNodeForSelect only works for a condition that is an `ICmpInst`, and
4731 // constant expressions cannot have instructions as operands, we'd have
4732 // returned getUnknown for a select constant expressions anyway.
4733 if (isa<Instruction>(U))
4734 return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0),
4735 U->getOperand(1), U->getOperand(2));
4737 default: // We cannot analyze this expression.
4741 return getUnknown(V);
4746 //===----------------------------------------------------------------------===//
4747 // Iteration Count Computation Code
4750 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
4751 if (BasicBlock *ExitingBB = L->getExitingBlock())
4752 return getSmallConstantTripCount(L, ExitingBB);
4754 // No trip count information for multiple exits.
4758 /// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
4759 /// normal unsigned value. Returns 0 if the trip count is unknown or not
4760 /// constant. Will also return 0 if the maximum trip count is very large (>=
4763 /// This "trip count" assumes that control exits via ExitingBlock. More
4764 /// precisely, it is the number of times that control may reach ExitingBlock
4765 /// before taking the branch. For loops with multiple exits, it may not be the
4766 /// number times that the loop header executes because the loop may exit
4767 /// prematurely via another branch.
4768 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
4769 BasicBlock *ExitingBlock) {
4770 assert(ExitingBlock && "Must pass a non-null exiting block!");
4771 assert(L->isLoopExiting(ExitingBlock) &&
4772 "Exiting block must actually branch out of the loop!");
4773 const SCEVConstant *ExitCount =
4774 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
4778 ConstantInt *ExitConst = ExitCount->getValue();
4780 // Guard against huge trip counts.
4781 if (ExitConst->getValue().getActiveBits() > 32)
4784 // In case of integer overflow, this returns 0, which is correct.
4785 return ((unsigned)ExitConst->getZExtValue()) + 1;
4788 unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
4789 if (BasicBlock *ExitingBB = L->getExitingBlock())
4790 return getSmallConstantTripMultiple(L, ExitingBB);
4792 // No trip multiple information for multiple exits.
4796 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
4797 /// trip count of this loop as a normal unsigned value, if possible. This
4798 /// means that the actual trip count is always a multiple of the returned
4799 /// value (don't forget the trip count could very well be zero as well!).
4801 /// Returns 1 if the trip count is unknown or not guaranteed to be the
4802 /// multiple of a constant (which is also the case if the trip count is simply
4803 /// constant, use getSmallConstantTripCount for that case), Will also return 1
4804 /// if the trip count is very large (>= 2^32).
4806 /// As explained in the comments for getSmallConstantTripCount, this assumes
4807 /// that control exits the loop via ExitingBlock.
4809 ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
4810 BasicBlock *ExitingBlock) {
4811 assert(ExitingBlock && "Must pass a non-null exiting block!");
4812 assert(L->isLoopExiting(ExitingBlock) &&
4813 "Exiting block must actually branch out of the loop!");
4814 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
4815 if (ExitCount == getCouldNotCompute())
4818 // Get the trip count from the BE count by adding 1.
4819 const SCEV *TCMul = getAddExpr(ExitCount, getOne(ExitCount->getType()));
4820 // FIXME: SCEV distributes multiplication as V1*C1 + V2*C1. We could attempt
4821 // to factor simple cases.
4822 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(TCMul))
4823 TCMul = Mul->getOperand(0);
4825 const SCEVConstant *MulC = dyn_cast<SCEVConstant>(TCMul);
4829 ConstantInt *Result = MulC->getValue();
4831 // Guard against huge trip counts (this requires checking
4832 // for zero to handle the case where the trip count == -1 and the
4834 if (!Result || Result->getValue().getActiveBits() > 32 ||
4835 Result->getValue().getActiveBits() == 0)
4838 return (unsigned)Result->getZExtValue();
4841 // getExitCount - Get the expression for the number of loop iterations for which
4842 // this loop is guaranteed not to exit via ExitingBlock. Otherwise return
4843 // SCEVCouldNotCompute.
4844 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
4845 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
4848 /// getBackedgeTakenCount - If the specified loop has a predictable
4849 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
4850 /// object. The backedge-taken count is the number of times the loop header
4851 /// will be branched to from within the loop. This is one less than the
4852 /// trip count of the loop, since it doesn't count the first iteration,
4853 /// when the header is branched to from outside the loop.
4855 /// Note that it is not valid to call this method on a loop without a
4856 /// loop-invariant backedge-taken count (see
4857 /// hasLoopInvariantBackedgeTakenCount).
4859 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
4860 return getBackedgeTakenInfo(L).getExact(this);
4863 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
4864 /// return the least SCEV value that is known never to be less than the
4865 /// actual backedge taken count.
4866 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
4867 return getBackedgeTakenInfo(L).getMax(this);
4870 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
4871 /// onto the given Worklist.
4873 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
4874 BasicBlock *Header = L->getHeader();
4876 // Push all Loop-header PHIs onto the Worklist stack.
4877 for (BasicBlock::iterator I = Header->begin();
4878 PHINode *PN = dyn_cast<PHINode>(I); ++I)
4879 Worklist.push_back(PN);
4882 const ScalarEvolution::BackedgeTakenInfo &
4883 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
4884 // Initially insert an invalid entry for this loop. If the insertion
4885 // succeeds, proceed to actually compute a backedge-taken count and
4886 // update the value. The temporary CouldNotCompute value tells SCEV
4887 // code elsewhere that it shouldn't attempt to request a new
4888 // backedge-taken count, which could result in infinite recursion.
4889 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
4890 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
4892 return Pair.first->second;
4894 // computeBackedgeTakenCount may allocate memory for its result. Inserting it
4895 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
4896 // must be cleared in this scope.
4897 BackedgeTakenInfo Result = computeBackedgeTakenCount(L);
4899 if (Result.getExact(this) != getCouldNotCompute()) {
4900 assert(isLoopInvariant(Result.getExact(this), L) &&
4901 isLoopInvariant(Result.getMax(this), L) &&
4902 "Computed backedge-taken count isn't loop invariant for loop!");
4903 ++NumTripCountsComputed;
4905 else if (Result.getMax(this) == getCouldNotCompute() &&
4906 isa<PHINode>(L->getHeader()->begin())) {
4907 // Only count loops that have phi nodes as not being computable.
4908 ++NumTripCountsNotComputed;
4911 // Now that we know more about the trip count for this loop, forget any
4912 // existing SCEV values for PHI nodes in this loop since they are only
4913 // conservative estimates made without the benefit of trip count
4914 // information. This is similar to the code in forgetLoop, except that
4915 // it handles SCEVUnknown PHI nodes specially.
4916 if (Result.hasAnyInfo()) {
4917 SmallVector<Instruction *, 16> Worklist;
4918 PushLoopPHIs(L, Worklist);
4920 SmallPtrSet<Instruction *, 8> Visited;
4921 while (!Worklist.empty()) {
4922 Instruction *I = Worklist.pop_back_val();
4923 if (!Visited.insert(I).second)
4926 ValueExprMapType::iterator It =
4927 ValueExprMap.find_as(static_cast<Value *>(I));
4928 if (It != ValueExprMap.end()) {
4929 const SCEV *Old = It->second;
4931 // SCEVUnknown for a PHI either means that it has an unrecognized
4932 // structure, or it's a PHI that's in the progress of being computed
4933 // by createNodeForPHI. In the former case, additional loop trip
4934 // count information isn't going to change anything. In the later
4935 // case, createNodeForPHI will perform the necessary updates on its
4936 // own when it gets to that point.
4937 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
4938 forgetMemoizedResults(Old);
4939 ValueExprMap.erase(It);
4941 if (PHINode *PN = dyn_cast<PHINode>(I))
4942 ConstantEvolutionLoopExitValue.erase(PN);
4945 PushDefUseChildren(I, Worklist);
4949 // Re-lookup the insert position, since the call to
4950 // computeBackedgeTakenCount above could result in a
4951 // recusive call to getBackedgeTakenInfo (on a different
4952 // loop), which would invalidate the iterator computed
4954 return BackedgeTakenCounts.find(L)->second = Result;
4957 /// forgetLoop - This method should be called by the client when it has
4958 /// changed a loop in a way that may effect ScalarEvolution's ability to
4959 /// compute a trip count, or if the loop is deleted.
4960 void ScalarEvolution::forgetLoop(const Loop *L) {
4961 // Drop any stored trip count value.
4962 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
4963 BackedgeTakenCounts.find(L);
4964 if (BTCPos != BackedgeTakenCounts.end()) {
4965 BTCPos->second.clear();
4966 BackedgeTakenCounts.erase(BTCPos);
4969 // Drop information about expressions based on loop-header PHIs.
4970 SmallVector<Instruction *, 16> Worklist;
4971 PushLoopPHIs(L, Worklist);
4973 SmallPtrSet<Instruction *, 8> Visited;
4974 while (!Worklist.empty()) {
4975 Instruction *I = Worklist.pop_back_val();
4976 if (!Visited.insert(I).second)
4979 ValueExprMapType::iterator It =
4980 ValueExprMap.find_as(static_cast<Value *>(I));
4981 if (It != ValueExprMap.end()) {
4982 forgetMemoizedResults(It->second);
4983 ValueExprMap.erase(It);
4984 if (PHINode *PN = dyn_cast<PHINode>(I))
4985 ConstantEvolutionLoopExitValue.erase(PN);
4988 PushDefUseChildren(I, Worklist);
4991 // Forget all contained loops too, to avoid dangling entries in the
4992 // ValuesAtScopes map.
4993 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
4997 /// forgetValue - This method should be called by the client when it has
4998 /// changed a value in a way that may effect its value, or which may
4999 /// disconnect it from a def-use chain linking it to a loop.
5000 void ScalarEvolution::forgetValue(Value *V) {
5001 Instruction *I = dyn_cast<Instruction>(V);
5004 // Drop information about expressions based on loop-header PHIs.
5005 SmallVector<Instruction *, 16> Worklist;
5006 Worklist.push_back(I);
5008 SmallPtrSet<Instruction *, 8> Visited;
5009 while (!Worklist.empty()) {
5010 I = Worklist.pop_back_val();
5011 if (!Visited.insert(I).second)
5014 ValueExprMapType::iterator It =
5015 ValueExprMap.find_as(static_cast<Value *>(I));
5016 if (It != ValueExprMap.end()) {
5017 forgetMemoizedResults(It->second);
5018 ValueExprMap.erase(It);
5019 if (PHINode *PN = dyn_cast<PHINode>(I))
5020 ConstantEvolutionLoopExitValue.erase(PN);
5023 PushDefUseChildren(I, Worklist);
5027 /// getExact - Get the exact loop backedge taken count considering all loop
5028 /// exits. A computable result can only be returned for loops with a single
5029 /// exit. Returning the minimum taken count among all exits is incorrect
5030 /// because one of the loop's exit limit's may have been skipped. HowFarToZero
5031 /// assumes that the limit of each loop test is never skipped. This is a valid
5032 /// assumption as long as the loop exits via that test. For precise results, it
5033 /// is the caller's responsibility to specify the relevant loop exit using
5034 /// getExact(ExitingBlock, SE).
5036 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
5037 // If any exits were not computable, the loop is not computable.
5038 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
5040 // We need exactly one computable exit.
5041 if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
5042 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
5044 const SCEV *BECount = nullptr;
5045 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5046 ENT != nullptr; ENT = ENT->getNextExit()) {
5048 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
5051 BECount = ENT->ExactNotTaken;
5052 else if (BECount != ENT->ExactNotTaken)
5053 return SE->getCouldNotCompute();
5055 assert(BECount && "Invalid not taken count for loop exit");
5059 /// getExact - Get the exact not taken count for this loop exit.
5061 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
5062 ScalarEvolution *SE) const {
5063 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5064 ENT != nullptr; ENT = ENT->getNextExit()) {
5066 if (ENT->ExitingBlock == ExitingBlock)
5067 return ENT->ExactNotTaken;
5069 return SE->getCouldNotCompute();
5072 /// getMax - Get the max backedge taken count for the loop.
5074 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
5075 return Max ? Max : SE->getCouldNotCompute();
5078 bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
5079 ScalarEvolution *SE) const {
5080 if (Max && Max != SE->getCouldNotCompute() && SE->hasOperand(Max, S))
5083 if (!ExitNotTaken.ExitingBlock)
5086 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5087 ENT != nullptr; ENT = ENT->getNextExit()) {
5089 if (ENT->ExactNotTaken != SE->getCouldNotCompute()
5090 && SE->hasOperand(ENT->ExactNotTaken, S)) {
5097 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
5098 /// computable exit into a persistent ExitNotTakenInfo array.
5099 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
5100 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
5101 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
5104 ExitNotTaken.setIncomplete();
5106 unsigned NumExits = ExitCounts.size();
5107 if (NumExits == 0) return;
5109 ExitNotTaken.ExitingBlock = ExitCounts[0].first;
5110 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
5111 if (NumExits == 1) return;
5113 // Handle the rare case of multiple computable exits.
5114 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
5116 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
5117 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
5118 PrevENT->setNextExit(ENT);
5119 ENT->ExitingBlock = ExitCounts[i].first;
5120 ENT->ExactNotTaken = ExitCounts[i].second;
5124 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
5125 void ScalarEvolution::BackedgeTakenInfo::clear() {
5126 ExitNotTaken.ExitingBlock = nullptr;
5127 ExitNotTaken.ExactNotTaken = nullptr;
5128 delete[] ExitNotTaken.getNextExit();
5131 /// computeBackedgeTakenCount - Compute the number of times the backedge
5132 /// of the specified loop will execute.
5133 ScalarEvolution::BackedgeTakenInfo
5134 ScalarEvolution::computeBackedgeTakenCount(const Loop *L) {
5135 SmallVector<BasicBlock *, 8> ExitingBlocks;
5136 L->getExitingBlocks(ExitingBlocks);
5138 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
5139 bool CouldComputeBECount = true;
5140 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
5141 const SCEV *MustExitMaxBECount = nullptr;
5142 const SCEV *MayExitMaxBECount = nullptr;
5144 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
5145 // and compute maxBECount.
5146 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
5147 BasicBlock *ExitBB = ExitingBlocks[i];
5148 ExitLimit EL = computeExitLimit(L, ExitBB);
5150 // 1. For each exit that can be computed, add an entry to ExitCounts.
5151 // CouldComputeBECount is true only if all exits can be computed.
5152 if (EL.Exact == getCouldNotCompute())
5153 // We couldn't compute an exact value for this exit, so
5154 // we won't be able to compute an exact value for the loop.
5155 CouldComputeBECount = false;
5157 ExitCounts.push_back(std::make_pair(ExitBB, EL.Exact));
5159 // 2. Derive the loop's MaxBECount from each exit's max number of
5160 // non-exiting iterations. Partition the loop exits into two kinds:
5161 // LoopMustExits and LoopMayExits.
5163 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
5164 // is a LoopMayExit. If any computable LoopMustExit is found, then
5165 // MaxBECount is the minimum EL.Max of computable LoopMustExits. Otherwise,
5166 // MaxBECount is conservatively the maximum EL.Max, where CouldNotCompute is
5167 // considered greater than any computable EL.Max.
5168 if (EL.Max != getCouldNotCompute() && Latch &&
5169 DT.dominates(ExitBB, Latch)) {
5170 if (!MustExitMaxBECount)
5171 MustExitMaxBECount = EL.Max;
5173 MustExitMaxBECount =
5174 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.Max);
5176 } else if (MayExitMaxBECount != getCouldNotCompute()) {
5177 if (!MayExitMaxBECount || EL.Max == getCouldNotCompute())
5178 MayExitMaxBECount = EL.Max;
5181 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.Max);
5185 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
5186 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
5187 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
5190 ScalarEvolution::ExitLimit
5191 ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
5193 // Okay, we've chosen an exiting block. See what condition causes us to exit
5194 // at this block and remember the exit block and whether all other targets
5195 // lead to the loop header.
5196 bool MustExecuteLoopHeader = true;
5197 BasicBlock *Exit = nullptr;
5198 for (succ_iterator SI = succ_begin(ExitingBlock), SE = succ_end(ExitingBlock);
5200 if (!L->contains(*SI)) {
5201 if (Exit) // Multiple exit successors.
5202 return getCouldNotCompute();
5204 } else if (*SI != L->getHeader()) {
5205 MustExecuteLoopHeader = false;
5208 // At this point, we know we have a conditional branch that determines whether
5209 // the loop is exited. However, we don't know if the branch is executed each
5210 // time through the loop. If not, then the execution count of the branch will
5211 // not be equal to the trip count of the loop.
5213 // Currently we check for this by checking to see if the Exit branch goes to
5214 // the loop header. If so, we know it will always execute the same number of
5215 // times as the loop. We also handle the case where the exit block *is* the
5216 // loop header. This is common for un-rotated loops.
5218 // If both of those tests fail, walk up the unique predecessor chain to the
5219 // header, stopping if there is an edge that doesn't exit the loop. If the
5220 // header is reached, the execution count of the branch will be equal to the
5221 // trip count of the loop.
5223 // More extensive analysis could be done to handle more cases here.
5225 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
5226 // The simple checks failed, try climbing the unique predecessor chain
5227 // up to the header.
5229 for (BasicBlock *BB = ExitingBlock; BB; ) {
5230 BasicBlock *Pred = BB->getUniquePredecessor();
5232 return getCouldNotCompute();
5233 TerminatorInst *PredTerm = Pred->getTerminator();
5234 for (const BasicBlock *PredSucc : PredTerm->successors()) {
5237 // If the predecessor has a successor that isn't BB and isn't
5238 // outside the loop, assume the worst.
5239 if (L->contains(PredSucc))
5240 return getCouldNotCompute();
5242 if (Pred == L->getHeader()) {
5249 return getCouldNotCompute();
5252 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
5253 TerminatorInst *Term = ExitingBlock->getTerminator();
5254 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
5255 assert(BI->isConditional() && "If unconditional, it can't be in loop!");
5256 // Proceed to the next level to examine the exit condition expression.
5257 return computeExitLimitFromCond(L, BI->getCondition(), BI->getSuccessor(0),
5258 BI->getSuccessor(1),
5259 /*ControlsExit=*/IsOnlyExit);
5262 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
5263 return computeExitLimitFromSingleExitSwitch(L, SI, Exit,
5264 /*ControlsExit=*/IsOnlyExit);
5266 return getCouldNotCompute();
5269 /// computeExitLimitFromCond - Compute the number of times the
5270 /// backedge of the specified loop will execute if its exit condition
5271 /// were a conditional branch of ExitCond, TBB, and FBB.
5273 /// @param ControlsExit is true if ExitCond directly controls the exit
5274 /// branch. In this case, we can assume that the loop exits only if the
5275 /// condition is true and can infer that failing to meet the condition prior to
5276 /// integer wraparound results in undefined behavior.
5277 ScalarEvolution::ExitLimit
5278 ScalarEvolution::computeExitLimitFromCond(const Loop *L,
5282 bool ControlsExit) {
5283 // Check if the controlling expression for this loop is an And or Or.
5284 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
5285 if (BO->getOpcode() == Instruction::And) {
5286 // Recurse on the operands of the and.
5287 bool EitherMayExit = L->contains(TBB);
5288 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
5289 ControlsExit && !EitherMayExit);
5290 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
5291 ControlsExit && !EitherMayExit);
5292 const SCEV *BECount = getCouldNotCompute();
5293 const SCEV *MaxBECount = getCouldNotCompute();
5294 if (EitherMayExit) {
5295 // Both conditions must be true for the loop to continue executing.
5296 // Choose the less conservative count.
5297 if (EL0.Exact == getCouldNotCompute() ||
5298 EL1.Exact == getCouldNotCompute())
5299 BECount = getCouldNotCompute();
5301 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
5302 if (EL0.Max == getCouldNotCompute())
5303 MaxBECount = EL1.Max;
5304 else if (EL1.Max == getCouldNotCompute())
5305 MaxBECount = EL0.Max;
5307 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
5309 // Both conditions must be true at the same time for the loop to exit.
5310 // For now, be conservative.
5311 assert(L->contains(FBB) && "Loop block has no successor in loop!");
5312 if (EL0.Max == EL1.Max)
5313 MaxBECount = EL0.Max;
5314 if (EL0.Exact == EL1.Exact)
5315 BECount = EL0.Exact;
5318 return ExitLimit(BECount, MaxBECount);
5320 if (BO->getOpcode() == Instruction::Or) {
5321 // Recurse on the operands of the or.
5322 bool EitherMayExit = L->contains(FBB);
5323 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
5324 ControlsExit && !EitherMayExit);
5325 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
5326 ControlsExit && !EitherMayExit);
5327 const SCEV *BECount = getCouldNotCompute();
5328 const SCEV *MaxBECount = getCouldNotCompute();
5329 if (EitherMayExit) {
5330 // Both conditions must be false for the loop to continue executing.
5331 // Choose the less conservative count.
5332 if (EL0.Exact == getCouldNotCompute() ||
5333 EL1.Exact == getCouldNotCompute())
5334 BECount = getCouldNotCompute();
5336 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
5337 if (EL0.Max == getCouldNotCompute())
5338 MaxBECount = EL1.Max;
5339 else if (EL1.Max == getCouldNotCompute())
5340 MaxBECount = EL0.Max;
5342 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
5344 // Both conditions must be false at the same time for the loop to exit.
5345 // For now, be conservative.
5346 assert(L->contains(TBB) && "Loop block has no successor in loop!");
5347 if (EL0.Max == EL1.Max)
5348 MaxBECount = EL0.Max;
5349 if (EL0.Exact == EL1.Exact)
5350 BECount = EL0.Exact;
5353 return ExitLimit(BECount, MaxBECount);
5357 // With an icmp, it may be feasible to compute an exact backedge-taken count.
5358 // Proceed to the next level to examine the icmp.
5359 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
5360 return computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
5362 // Check for a constant condition. These are normally stripped out by
5363 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
5364 // preserve the CFG and is temporarily leaving constant conditions
5366 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
5367 if (L->contains(FBB) == !CI->getZExtValue())
5368 // The backedge is always taken.
5369 return getCouldNotCompute();
5371 // The backedge is never taken.
5372 return getZero(CI->getType());
5375 // If it's not an integer or pointer comparison then compute it the hard way.
5376 return computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5379 ScalarEvolution::ExitLimit
5380 ScalarEvolution::computeExitLimitFromICmp(const Loop *L,
5384 bool ControlsExit) {
5386 // If the condition was exit on true, convert the condition to exit on false
5387 ICmpInst::Predicate Cond;
5388 if (!L->contains(FBB))
5389 Cond = ExitCond->getPredicate();
5391 Cond = ExitCond->getInversePredicate();
5393 // Handle common loops like: for (X = "string"; *X; ++X)
5394 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
5395 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
5397 computeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
5398 if (ItCnt.hasAnyInfo())
5402 ExitLimit ShiftEL = computeShiftCompareExitLimit(
5403 ExitCond->getOperand(0), ExitCond->getOperand(1), L, Cond);
5404 if (ShiftEL.hasAnyInfo())
5407 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
5408 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
5410 // Try to evaluate any dependencies out of the loop.
5411 LHS = getSCEVAtScope(LHS, L);
5412 RHS = getSCEVAtScope(RHS, L);
5414 // At this point, we would like to compute how many iterations of the
5415 // loop the predicate will return true for these inputs.
5416 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
5417 // If there is a loop-invariant, force it into the RHS.
5418 std::swap(LHS, RHS);
5419 Cond = ICmpInst::getSwappedPredicate(Cond);
5422 // Simplify the operands before analyzing them.
5423 (void)SimplifyICmpOperands(Cond, LHS, RHS);
5425 // If we have a comparison of a chrec against a constant, try to use value
5426 // ranges to answer this query.
5427 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
5428 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
5429 if (AddRec->getLoop() == L) {
5430 // Form the constant range.
5431 ConstantRange CompRange(
5432 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
5434 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
5435 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
5439 case ICmpInst::ICMP_NE: { // while (X != Y)
5440 // Convert to: while (X-Y != 0)
5441 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5442 if (EL.hasAnyInfo()) return EL;
5445 case ICmpInst::ICMP_EQ: { // while (X == Y)
5446 // Convert to: while (X-Y == 0)
5447 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
5448 if (EL.hasAnyInfo()) return EL;
5451 case ICmpInst::ICMP_SLT:
5452 case ICmpInst::ICMP_ULT: { // while (X < Y)
5453 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
5454 ExitLimit EL = HowManyLessThans(LHS, RHS, L, IsSigned, ControlsExit);
5455 if (EL.hasAnyInfo()) return EL;
5458 case ICmpInst::ICMP_SGT:
5459 case ICmpInst::ICMP_UGT: { // while (X > Y)
5460 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
5461 ExitLimit EL = HowManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit);
5462 if (EL.hasAnyInfo()) return EL;
5468 return computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5471 ScalarEvolution::ExitLimit
5472 ScalarEvolution::computeExitLimitFromSingleExitSwitch(const Loop *L,
5474 BasicBlock *ExitingBlock,
5475 bool ControlsExit) {
5476 assert(!L->contains(ExitingBlock) && "Not an exiting block!");
5478 // Give up if the exit is the default dest of a switch.
5479 if (Switch->getDefaultDest() == ExitingBlock)
5480 return getCouldNotCompute();
5482 assert(L->contains(Switch->getDefaultDest()) &&
5483 "Default case must not exit the loop!");
5484 const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
5485 const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
5487 // while (X != Y) --> while (X-Y != 0)
5488 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5489 if (EL.hasAnyInfo())
5492 return getCouldNotCompute();
5495 static ConstantInt *
5496 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
5497 ScalarEvolution &SE) {
5498 const SCEV *InVal = SE.getConstant(C);
5499 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
5500 assert(isa<SCEVConstant>(Val) &&
5501 "Evaluation of SCEV at constant didn't fold correctly?");
5502 return cast<SCEVConstant>(Val)->getValue();
5505 /// computeLoadConstantCompareExitLimit - Given an exit condition of
5506 /// 'icmp op load X, cst', try to see if we can compute the backedge
5507 /// execution count.
5508 ScalarEvolution::ExitLimit
5509 ScalarEvolution::computeLoadConstantCompareExitLimit(
5513 ICmpInst::Predicate predicate) {
5515 if (LI->isVolatile()) return getCouldNotCompute();
5517 // Check to see if the loaded pointer is a getelementptr of a global.
5518 // TODO: Use SCEV instead of manually grubbing with GEPs.
5519 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
5520 if (!GEP) return getCouldNotCompute();
5522 // Make sure that it is really a constant global we are gepping, with an
5523 // initializer, and make sure the first IDX is really 0.
5524 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
5525 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
5526 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
5527 !cast<Constant>(GEP->getOperand(1))->isNullValue())
5528 return getCouldNotCompute();
5530 // Okay, we allow one non-constant index into the GEP instruction.
5531 Value *VarIdx = nullptr;
5532 std::vector<Constant*> Indexes;
5533 unsigned VarIdxNum = 0;
5534 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
5535 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
5536 Indexes.push_back(CI);
5537 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
5538 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
5539 VarIdx = GEP->getOperand(i);
5541 Indexes.push_back(nullptr);
5544 // Loop-invariant loads may be a byproduct of loop optimization. Skip them.
5546 return getCouldNotCompute();
5548 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
5549 // Check to see if X is a loop variant variable value now.
5550 const SCEV *Idx = getSCEV(VarIdx);
5551 Idx = getSCEVAtScope(Idx, L);
5553 // We can only recognize very limited forms of loop index expressions, in
5554 // particular, only affine AddRec's like {C1,+,C2}.
5555 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
5556 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
5557 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
5558 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
5559 return getCouldNotCompute();
5561 unsigned MaxSteps = MaxBruteForceIterations;
5562 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
5563 ConstantInt *ItCst = ConstantInt::get(
5564 cast<IntegerType>(IdxExpr->getType()), IterationNum);
5565 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
5567 // Form the GEP offset.
5568 Indexes[VarIdxNum] = Val;
5570 Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
5572 if (!Result) break; // Cannot compute!
5574 // Evaluate the condition for this iteration.
5575 Result = ConstantExpr::getICmp(predicate, Result, RHS);
5576 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
5577 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
5578 ++NumArrayLenItCounts;
5579 return getConstant(ItCst); // Found terminating iteration!
5582 return getCouldNotCompute();
5585 ScalarEvolution::ExitLimit ScalarEvolution::computeShiftCompareExitLimit(
5586 Value *LHS, Value *RHSV, const Loop *L, ICmpInst::Predicate Pred) {
5587 ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV);
5589 return getCouldNotCompute();
5591 const BasicBlock *Latch = L->getLoopLatch();
5593 return getCouldNotCompute();
5595 const BasicBlock *Predecessor = L->getLoopPredecessor();
5597 return getCouldNotCompute();
5599 // Return true if V is of the form "LHS `shift_op` <positive constant>".
5600 // Return LHS in OutLHS and shift_opt in OutOpCode.
5601 auto MatchPositiveShift =
5602 [](Value *V, Value *&OutLHS, Instruction::BinaryOps &OutOpCode) {
5604 using namespace PatternMatch;
5606 ConstantInt *ShiftAmt;
5607 if (match(V, m_LShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
5608 OutOpCode = Instruction::LShr;
5609 else if (match(V, m_AShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
5610 OutOpCode = Instruction::AShr;
5611 else if (match(V, m_Shl(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
5612 OutOpCode = Instruction::Shl;
5616 return ShiftAmt->getValue().isStrictlyPositive();
5619 // Recognize a "shift recurrence" either of the form %iv or of %iv.shifted in
5622 // %iv = phi i32 [ %iv.shifted, %loop ], [ %val, %preheader ]
5623 // %iv.shifted = lshr i32 %iv, <positive constant>
5625 // Return true on a succesful match. Return the corresponding PHI node (%iv
5626 // above) in PNOut and the opcode of the shift operation in OpCodeOut.
5627 auto MatchShiftRecurrence =
5628 [&](Value *V, PHINode *&PNOut, Instruction::BinaryOps &OpCodeOut) {
5629 Optional<Instruction::BinaryOps> PostShiftOpCode;
5632 Instruction::BinaryOps OpC;
5635 // If we encounter a shift instruction, "peel off" the shift operation,
5636 // and remember that we did so. Later when we inspect %iv's backedge
5637 // value, we will make sure that the backedge value uses the same
5640 // Note: the peeled shift operation does not have to be the same
5641 // instruction as the one feeding into the PHI's backedge value. We only
5642 // really care about it being the same *kind* of shift instruction --
5643 // that's all that is required for our later inferences to hold.
5644 if (MatchPositiveShift(LHS, V, OpC)) {
5645 PostShiftOpCode = OpC;
5650 PNOut = dyn_cast<PHINode>(LHS);
5651 if (!PNOut || PNOut->getParent() != L->getHeader())
5654 Value *BEValue = PNOut->getIncomingValueForBlock(Latch);
5658 // The backedge value for the PHI node must be a shift by a positive
5660 MatchPositiveShift(BEValue, OpLHS, OpCodeOut) &&
5662 // of the PHI node itself
5665 // and the kind of shift should be match the kind of shift we peeled
5667 (!PostShiftOpCode.hasValue() || *PostShiftOpCode == OpCodeOut);
5671 Instruction::BinaryOps OpCode;
5672 if (!MatchShiftRecurrence(LHS, PN, OpCode))
5673 return getCouldNotCompute();
5675 const DataLayout &DL = getDataLayout();
5677 // The key rationale for this optimization is that for some kinds of shift
5678 // recurrences, the value of the recurrence "stabilizes" to either 0 or -1
5679 // within a finite number of iterations. If the condition guarding the
5680 // backedge (in the sense that the backedge is taken if the condition is true)
5681 // is false for the value the shift recurrence stabilizes to, then we know
5682 // that the backedge is taken only a finite number of times.
5684 ConstantInt *StableValue = nullptr;
5687 llvm_unreachable("Impossible case!");
5689 case Instruction::AShr: {
5690 // {K,ashr,<positive-constant>} stabilizes to signum(K) in at most
5691 // bitwidth(K) iterations.
5692 Value *FirstValue = PN->getIncomingValueForBlock(Predecessor);
5693 bool KnownZero, KnownOne;
5694 ComputeSignBit(FirstValue, KnownZero, KnownOne, DL, 0, nullptr,
5695 Predecessor->getTerminator(), &DT);
5696 auto *Ty = cast<IntegerType>(RHS->getType());
5698 StableValue = ConstantInt::get(Ty, 0);
5700 StableValue = ConstantInt::get(Ty, -1, true);
5702 return getCouldNotCompute();
5706 case Instruction::LShr:
5707 case Instruction::Shl:
5708 // Both {K,lshr,<positive-constant>} and {K,shl,<positive-constant>}
5709 // stabilize to 0 in at most bitwidth(K) iterations.
5710 StableValue = ConstantInt::get(cast<IntegerType>(RHS->getType()), 0);
5715 ConstantFoldCompareInstOperands(Pred, StableValue, RHS, DL, &TLI);
5716 assert(Result->getType()->isIntegerTy(1) &&
5717 "Otherwise cannot be an operand to a branch instruction");
5719 if (Result->isZeroValue()) {
5720 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
5721 const SCEV *UpperBound =
5722 getConstant(getEffectiveSCEVType(RHS->getType()), BitWidth);
5723 return ExitLimit(getCouldNotCompute(), UpperBound);
5726 return getCouldNotCompute();
5729 /// CanConstantFold - Return true if we can constant fold an instruction of the
5730 /// specified type, assuming that all operands were constants.
5731 static bool CanConstantFold(const Instruction *I) {
5732 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
5733 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
5737 if (const CallInst *CI = dyn_cast<CallInst>(I))
5738 if (const Function *F = CI->getCalledFunction())
5739 return canConstantFoldCallTo(F);
5743 /// Determine whether this instruction can constant evolve within this loop
5744 /// assuming its operands can all constant evolve.
5745 static bool canConstantEvolve(Instruction *I, const Loop *L) {
5746 // An instruction outside of the loop can't be derived from a loop PHI.
5747 if (!L->contains(I)) return false;
5749 if (isa<PHINode>(I)) {
5750 // We don't currently keep track of the control flow needed to evaluate
5751 // PHIs, so we cannot handle PHIs inside of loops.
5752 return L->getHeader() == I->getParent();
5755 // If we won't be able to constant fold this expression even if the operands
5756 // are constants, bail early.
5757 return CanConstantFold(I);
5760 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
5761 /// recursing through each instruction operand until reaching a loop header phi.
5763 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
5764 DenseMap<Instruction *, PHINode *> &PHIMap) {
5766 // Otherwise, we can evaluate this instruction if all of its operands are
5767 // constant or derived from a PHI node themselves.
5768 PHINode *PHI = nullptr;
5769 for (Instruction::op_iterator OpI = UseInst->op_begin(),
5770 OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
5772 if (isa<Constant>(*OpI)) continue;
5774 Instruction *OpInst = dyn_cast<Instruction>(*OpI);
5775 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
5777 PHINode *P = dyn_cast<PHINode>(OpInst);
5779 // If this operand is already visited, reuse the prior result.
5780 // We may have P != PHI if this is the deepest point at which the
5781 // inconsistent paths meet.
5782 P = PHIMap.lookup(OpInst);
5784 // Recurse and memoize the results, whether a phi is found or not.
5785 // This recursive call invalidates pointers into PHIMap.
5786 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
5790 return nullptr; // Not evolving from PHI
5791 if (PHI && PHI != P)
5792 return nullptr; // Evolving from multiple different PHIs.
5795 // This is a expression evolving from a constant PHI!
5799 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
5800 /// in the loop that V is derived from. We allow arbitrary operations along the
5801 /// way, but the operands of an operation must either be constants or a value
5802 /// derived from a constant PHI. If this expression does not fit with these
5803 /// constraints, return null.
5804 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
5805 Instruction *I = dyn_cast<Instruction>(V);
5806 if (!I || !canConstantEvolve(I, L)) return nullptr;
5808 if (PHINode *PN = dyn_cast<PHINode>(I))
5811 // Record non-constant instructions contained by the loop.
5812 DenseMap<Instruction *, PHINode *> PHIMap;
5813 return getConstantEvolvingPHIOperands(I, L, PHIMap);
5816 /// EvaluateExpression - Given an expression that passes the
5817 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
5818 /// in the loop has the value PHIVal. If we can't fold this expression for some
5819 /// reason, return null.
5820 static Constant *EvaluateExpression(Value *V, const Loop *L,
5821 DenseMap<Instruction *, Constant *> &Vals,
5822 const DataLayout &DL,
5823 const TargetLibraryInfo *TLI) {
5824 // Convenient constant check, but redundant for recursive calls.
5825 if (Constant *C = dyn_cast<Constant>(V)) return C;
5826 Instruction *I = dyn_cast<Instruction>(V);
5827 if (!I) return nullptr;
5829 if (Constant *C = Vals.lookup(I)) return C;
5831 // An instruction inside the loop depends on a value outside the loop that we
5832 // weren't given a mapping for, or a value such as a call inside the loop.
5833 if (!canConstantEvolve(I, L)) return nullptr;
5835 // An unmapped PHI can be due to a branch or another loop inside this loop,
5836 // or due to this not being the initial iteration through a loop where we
5837 // couldn't compute the evolution of this particular PHI last time.
5838 if (isa<PHINode>(I)) return nullptr;
5840 std::vector<Constant*> Operands(I->getNumOperands());
5842 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5843 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
5845 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
5846 if (!Operands[i]) return nullptr;
5849 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
5851 if (!C) return nullptr;
5855 if (CmpInst *CI = dyn_cast<CmpInst>(I))
5856 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
5857 Operands[1], DL, TLI);
5858 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
5859 if (!LI->isVolatile())
5860 return ConstantFoldLoadFromConstPtr(Operands[0], DL);
5862 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, DL,
5866 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
5867 /// in the header of its containing loop, we know the loop executes a
5868 /// constant number of times, and the PHI node is just a recurrence
5869 /// involving constants, fold it.
5871 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
5874 auto I = ConstantEvolutionLoopExitValue.find(PN);
5875 if (I != ConstantEvolutionLoopExitValue.end())
5878 if (BEs.ugt(MaxBruteForceIterations))
5879 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
5881 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
5883 DenseMap<Instruction *, Constant *> CurrentIterVals;
5884 BasicBlock *Header = L->getHeader();
5885 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5887 BasicBlock *Latch = L->getLoopLatch();
5891 // Since the loop has one latch, the PHI node must have two entries. One
5892 // entry must be a constant (coming in from outside of the loop), and the
5893 // second must be derived from the same PHI.
5895 BasicBlock *NonLatch = Latch == PN->getIncomingBlock(0)
5896 ? PN->getIncomingBlock(1)
5897 : PN->getIncomingBlock(0);
5899 assert(PN->getNumIncomingValues() == 2 && "Follows from having one latch!");
5901 // Note: not all PHI nodes in the same block have to have their incoming
5902 // values in the same order, so we use the basic block to look up the incoming
5903 // value, not an index.
5905 for (auto &I : *Header) {
5906 PHINode *PHI = dyn_cast<PHINode>(&I);
5909 dyn_cast<Constant>(PHI->getIncomingValueForBlock(NonLatch));
5910 if (!StartCST) continue;
5911 CurrentIterVals[PHI] = StartCST;
5913 if (!CurrentIterVals.count(PN))
5914 return RetVal = nullptr;
5916 Value *BEValue = PN->getIncomingValueForBlock(Latch);
5918 // Execute the loop symbolically to determine the exit value.
5919 if (BEs.getActiveBits() >= 32)
5920 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
5922 unsigned NumIterations = BEs.getZExtValue(); // must be in range
5923 unsigned IterationNum = 0;
5924 const DataLayout &DL = getDataLayout();
5925 for (; ; ++IterationNum) {
5926 if (IterationNum == NumIterations)
5927 return RetVal = CurrentIterVals[PN]; // Got exit value!
5929 // Compute the value of the PHIs for the next iteration.
5930 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
5931 DenseMap<Instruction *, Constant *> NextIterVals;
5933 EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
5935 return nullptr; // Couldn't evaluate!
5936 NextIterVals[PN] = NextPHI;
5938 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
5940 // Also evaluate the other PHI nodes. However, we don't get to stop if we
5941 // cease to be able to evaluate one of them or if they stop evolving,
5942 // because that doesn't necessarily prevent us from computing PN.
5943 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
5944 for (const auto &I : CurrentIterVals) {
5945 PHINode *PHI = dyn_cast<PHINode>(I.first);
5946 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
5947 PHIsToCompute.emplace_back(PHI, I.second);
5949 // We use two distinct loops because EvaluateExpression may invalidate any
5950 // iterators into CurrentIterVals.
5951 for (const auto &I : PHIsToCompute) {
5952 PHINode *PHI = I.first;
5953 Constant *&NextPHI = NextIterVals[PHI];
5954 if (!NextPHI) { // Not already computed.
5955 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
5956 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
5958 if (NextPHI != I.second)
5959 StoppedEvolving = false;
5962 // If all entries in CurrentIterVals == NextIterVals then we can stop
5963 // iterating, the loop can't continue to change.
5964 if (StoppedEvolving)
5965 return RetVal = CurrentIterVals[PN];
5967 CurrentIterVals.swap(NextIterVals);
5971 const SCEV *ScalarEvolution::computeExitCountExhaustively(const Loop *L,
5974 PHINode *PN = getConstantEvolvingPHI(Cond, L);
5975 if (!PN) return getCouldNotCompute();
5977 // If the loop is canonicalized, the PHI will have exactly two entries.
5978 // That's the only form we support here.
5979 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
5981 DenseMap<Instruction *, Constant *> CurrentIterVals;
5982 BasicBlock *Header = L->getHeader();
5983 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5985 BasicBlock *Latch = L->getLoopLatch();
5986 assert(Latch && "Should follow from NumIncomingValues == 2!");
5988 // NonLatch is the preheader, or something equivalent.
5989 BasicBlock *NonLatch = Latch == PN->getIncomingBlock(0)
5990 ? PN->getIncomingBlock(1)
5991 : PN->getIncomingBlock(0);
5993 // Note: not all PHI nodes in the same block have to have their incoming
5994 // values in the same order, so we use the basic block to look up the incoming
5995 // value, not an index.
5997 for (auto &I : *Header) {
5998 PHINode *PHI = dyn_cast<PHINode>(&I);
6002 dyn_cast<Constant>(PHI->getIncomingValueForBlock(NonLatch));
6003 if (!StartCST) continue;
6004 CurrentIterVals[PHI] = StartCST;
6006 if (!CurrentIterVals.count(PN))
6007 return getCouldNotCompute();
6009 // Okay, we find a PHI node that defines the trip count of this loop. Execute
6010 // the loop symbolically to determine when the condition gets a value of
6012 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
6013 const DataLayout &DL = getDataLayout();
6014 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
6015 auto *CondVal = dyn_cast_or_null<ConstantInt>(
6016 EvaluateExpression(Cond, L, CurrentIterVals, DL, &TLI));
6018 // Couldn't symbolically evaluate.
6019 if (!CondVal) return getCouldNotCompute();
6021 if (CondVal->getValue() == uint64_t(ExitWhen)) {
6022 ++NumBruteForceTripCountsComputed;
6023 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
6026 // Update all the PHI nodes for the next iteration.
6027 DenseMap<Instruction *, Constant *> NextIterVals;
6029 // Create a list of which PHIs we need to compute. We want to do this before
6030 // calling EvaluateExpression on them because that may invalidate iterators
6031 // into CurrentIterVals.
6032 SmallVector<PHINode *, 8> PHIsToCompute;
6033 for (const auto &I : CurrentIterVals) {
6034 PHINode *PHI = dyn_cast<PHINode>(I.first);
6035 if (!PHI || PHI->getParent() != Header) continue;
6036 PHIsToCompute.push_back(PHI);
6038 for (PHINode *PHI : PHIsToCompute) {
6039 Constant *&NextPHI = NextIterVals[PHI];
6040 if (NextPHI) continue; // Already computed!
6042 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
6043 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6045 CurrentIterVals.swap(NextIterVals);
6048 // Too many iterations were needed to evaluate.
6049 return getCouldNotCompute();
6052 /// getSCEVAtScope - Return a SCEV expression for the specified value
6053 /// at the specified scope in the program. The L value specifies a loop
6054 /// nest to evaluate the expression at, where null is the top-level or a
6055 /// specified loop is immediately inside of the loop.
6057 /// This method can be used to compute the exit value for a variable defined
6058 /// in a loop by querying what the value will hold in the parent loop.
6060 /// In the case that a relevant loop exit value cannot be computed, the
6061 /// original value V is returned.
6062 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
6063 // Check to see if we've folded this expression at this loop before.
6064 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = ValuesAtScopes[V];
6065 for (unsigned u = 0; u < Values.size(); u++) {
6066 if (Values[u].first == L)
6067 return Values[u].second ? Values[u].second : V;
6069 Values.push_back(std::make_pair(L, static_cast<const SCEV *>(nullptr)));
6070 // Otherwise compute it.
6071 const SCEV *C = computeSCEVAtScope(V, L);
6072 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values2 = ValuesAtScopes[V];
6073 for (unsigned u = Values2.size(); u > 0; u--) {
6074 if (Values2[u - 1].first == L) {
6075 Values2[u - 1].second = C;
6082 /// This builds up a Constant using the ConstantExpr interface. That way, we
6083 /// will return Constants for objects which aren't represented by a
6084 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
6085 /// Returns NULL if the SCEV isn't representable as a Constant.
6086 static Constant *BuildConstantFromSCEV(const SCEV *V) {
6087 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
6088 case scCouldNotCompute:
6092 return cast<SCEVConstant>(V)->getValue();
6094 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
6095 case scSignExtend: {
6096 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
6097 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
6098 return ConstantExpr::getSExt(CastOp, SS->getType());
6101 case scZeroExtend: {
6102 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
6103 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
6104 return ConstantExpr::getZExt(CastOp, SZ->getType());
6108 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
6109 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
6110 return ConstantExpr::getTrunc(CastOp, ST->getType());
6114 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
6115 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
6116 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6117 unsigned AS = PTy->getAddressSpace();
6118 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6119 C = ConstantExpr::getBitCast(C, DestPtrTy);
6121 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
6122 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
6123 if (!C2) return nullptr;
6126 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
6127 unsigned AS = C2->getType()->getPointerAddressSpace();
6129 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6130 // The offsets have been converted to bytes. We can add bytes to an
6131 // i8* by GEP with the byte count in the first index.
6132 C = ConstantExpr::getBitCast(C, DestPtrTy);
6135 // Don't bother trying to sum two pointers. We probably can't
6136 // statically compute a load that results from it anyway.
6137 if (C2->getType()->isPointerTy())
6140 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6141 if (PTy->getElementType()->isStructTy())
6142 C2 = ConstantExpr::getIntegerCast(
6143 C2, Type::getInt32Ty(C->getContext()), true);
6144 C = ConstantExpr::getGetElementPtr(PTy->getElementType(), C, C2);
6146 C = ConstantExpr::getAdd(C, C2);
6153 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
6154 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
6155 // Don't bother with pointers at all.
6156 if (C->getType()->isPointerTy()) return nullptr;
6157 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
6158 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
6159 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
6160 C = ConstantExpr::getMul(C, C2);
6167 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
6168 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
6169 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
6170 if (LHS->getType() == RHS->getType())
6171 return ConstantExpr::getUDiv(LHS, RHS);
6176 break; // TODO: smax, umax.
6181 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
6182 if (isa<SCEVConstant>(V)) return V;
6184 // If this instruction is evolved from a constant-evolving PHI, compute the
6185 // exit value from the loop without using SCEVs.
6186 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
6187 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
6188 const Loop *LI = this->LI[I->getParent()];
6189 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
6190 if (PHINode *PN = dyn_cast<PHINode>(I))
6191 if (PN->getParent() == LI->getHeader()) {
6192 // Okay, there is no closed form solution for the PHI node. Check
6193 // to see if the loop that contains it has a known backedge-taken
6194 // count. If so, we may be able to force computation of the exit
6196 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
6197 if (const SCEVConstant *BTCC =
6198 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
6199 // Okay, we know how many times the containing loop executes. If
6200 // this is a constant evolving PHI node, get the final value at
6201 // the specified iteration number.
6202 Constant *RV = getConstantEvolutionLoopExitValue(PN,
6203 BTCC->getValue()->getValue(),
6205 if (RV) return getSCEV(RV);
6209 // Okay, this is an expression that we cannot symbolically evaluate
6210 // into a SCEV. Check to see if it's possible to symbolically evaluate
6211 // the arguments into constants, and if so, try to constant propagate the
6212 // result. This is particularly useful for computing loop exit values.
6213 if (CanConstantFold(I)) {
6214 SmallVector<Constant *, 4> Operands;
6215 bool MadeImprovement = false;
6216 for (Value *Op : I->operands()) {
6217 if (Constant *C = dyn_cast<Constant>(Op)) {
6218 Operands.push_back(C);
6222 // If any of the operands is non-constant and if they are
6223 // non-integer and non-pointer, don't even try to analyze them
6224 // with scev techniques.
6225 if (!isSCEVable(Op->getType()))
6228 const SCEV *OrigV = getSCEV(Op);
6229 const SCEV *OpV = getSCEVAtScope(OrigV, L);
6230 MadeImprovement |= OrigV != OpV;
6232 Constant *C = BuildConstantFromSCEV(OpV);
6234 if (C->getType() != Op->getType())
6235 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
6239 Operands.push_back(C);
6242 // Check to see if getSCEVAtScope actually made an improvement.
6243 if (MadeImprovement) {
6244 Constant *C = nullptr;
6245 const DataLayout &DL = getDataLayout();
6246 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
6247 C = ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
6248 Operands[1], DL, &TLI);
6249 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
6250 if (!LI->isVolatile())
6251 C = ConstantFoldLoadFromConstPtr(Operands[0], DL);
6253 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands,
6261 // This is some other type of SCEVUnknown, just return it.
6265 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
6266 // Avoid performing the look-up in the common case where the specified
6267 // expression has no loop-variant portions.
6268 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
6269 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
6270 if (OpAtScope != Comm->getOperand(i)) {
6271 // Okay, at least one of these operands is loop variant but might be
6272 // foldable. Build a new instance of the folded commutative expression.
6273 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
6274 Comm->op_begin()+i);
6275 NewOps.push_back(OpAtScope);
6277 for (++i; i != e; ++i) {
6278 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
6279 NewOps.push_back(OpAtScope);
6281 if (isa<SCEVAddExpr>(Comm))
6282 return getAddExpr(NewOps);
6283 if (isa<SCEVMulExpr>(Comm))
6284 return getMulExpr(NewOps);
6285 if (isa<SCEVSMaxExpr>(Comm))
6286 return getSMaxExpr(NewOps);
6287 if (isa<SCEVUMaxExpr>(Comm))
6288 return getUMaxExpr(NewOps);
6289 llvm_unreachable("Unknown commutative SCEV type!");
6292 // If we got here, all operands are loop invariant.
6296 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
6297 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
6298 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
6299 if (LHS == Div->getLHS() && RHS == Div->getRHS())
6300 return Div; // must be loop invariant
6301 return getUDivExpr(LHS, RHS);
6304 // If this is a loop recurrence for a loop that does not contain L, then we
6305 // are dealing with the final value computed by the loop.
6306 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
6307 // First, attempt to evaluate each operand.
6308 // Avoid performing the look-up in the common case where the specified
6309 // expression has no loop-variant portions.
6310 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
6311 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
6312 if (OpAtScope == AddRec->getOperand(i))
6315 // Okay, at least one of these operands is loop variant but might be
6316 // foldable. Build a new instance of the folded commutative expression.
6317 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
6318 AddRec->op_begin()+i);
6319 NewOps.push_back(OpAtScope);
6320 for (++i; i != e; ++i)
6321 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
6323 const SCEV *FoldedRec =
6324 getAddRecExpr(NewOps, AddRec->getLoop(),
6325 AddRec->getNoWrapFlags(SCEV::FlagNW));
6326 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
6327 // The addrec may be folded to a nonrecurrence, for example, if the
6328 // induction variable is multiplied by zero after constant folding. Go
6329 // ahead and return the folded value.
6335 // If the scope is outside the addrec's loop, evaluate it by using the
6336 // loop exit value of the addrec.
6337 if (!AddRec->getLoop()->contains(L)) {
6338 // To evaluate this recurrence, we need to know how many times the AddRec
6339 // loop iterates. Compute this now.
6340 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
6341 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
6343 // Then, evaluate the AddRec.
6344 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
6350 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
6351 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6352 if (Op == Cast->getOperand())
6353 return Cast; // must be loop invariant
6354 return getZeroExtendExpr(Op, Cast->getType());
6357 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
6358 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6359 if (Op == Cast->getOperand())
6360 return Cast; // must be loop invariant
6361 return getSignExtendExpr(Op, Cast->getType());
6364 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
6365 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6366 if (Op == Cast->getOperand())
6367 return Cast; // must be loop invariant
6368 return getTruncateExpr(Op, Cast->getType());
6371 llvm_unreachable("Unknown SCEV type!");
6374 /// getSCEVAtScope - This is a convenience function which does
6375 /// getSCEVAtScope(getSCEV(V), L).
6376 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
6377 return getSCEVAtScope(getSCEV(V), L);
6380 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
6381 /// following equation:
6383 /// A * X = B (mod N)
6385 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
6386 /// A and B isn't important.
6388 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
6389 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
6390 ScalarEvolution &SE) {
6391 uint32_t BW = A.getBitWidth();
6392 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
6393 assert(A != 0 && "A must be non-zero.");
6397 // The gcd of A and N may have only one prime factor: 2. The number of
6398 // trailing zeros in A is its multiplicity
6399 uint32_t Mult2 = A.countTrailingZeros();
6402 // 2. Check if B is divisible by D.
6404 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
6405 // is not less than multiplicity of this prime factor for D.
6406 if (B.countTrailingZeros() < Mult2)
6407 return SE.getCouldNotCompute();
6409 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
6412 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
6413 // bit width during computations.
6414 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
6415 APInt Mod(BW + 1, 0);
6416 Mod.setBit(BW - Mult2); // Mod = N / D
6417 APInt I = AD.multiplicativeInverse(Mod);
6419 // 4. Compute the minimum unsigned root of the equation:
6420 // I * (B / D) mod (N / D)
6421 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
6423 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
6425 return SE.getConstant(Result.trunc(BW));
6428 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
6429 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
6430 /// might be the same) or two SCEVCouldNotCompute objects.
6432 static std::pair<const SCEV *,const SCEV *>
6433 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
6434 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
6435 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
6436 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
6437 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
6439 // We currently can only solve this if the coefficients are constants.
6440 if (!LC || !MC || !NC) {
6441 const SCEV *CNC = SE.getCouldNotCompute();
6442 return std::make_pair(CNC, CNC);
6445 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
6446 const APInt &L = LC->getValue()->getValue();
6447 const APInt &M = MC->getValue()->getValue();
6448 const APInt &N = NC->getValue()->getValue();
6449 APInt Two(BitWidth, 2);
6450 APInt Four(BitWidth, 4);
6453 using namespace APIntOps;
6455 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
6456 // The B coefficient is M-N/2
6460 // The A coefficient is N/2
6461 APInt A(N.sdiv(Two));
6463 // Compute the B^2-4ac term.
6466 SqrtTerm -= Four * (A * C);
6468 if (SqrtTerm.isNegative()) {
6469 // The loop is provably infinite.
6470 const SCEV *CNC = SE.getCouldNotCompute();
6471 return std::make_pair(CNC, CNC);
6474 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
6475 // integer value or else APInt::sqrt() will assert.
6476 APInt SqrtVal(SqrtTerm.sqrt());
6478 // Compute the two solutions for the quadratic formula.
6479 // The divisions must be performed as signed divisions.
6482 if (TwoA.isMinValue()) {
6483 const SCEV *CNC = SE.getCouldNotCompute();
6484 return std::make_pair(CNC, CNC);
6487 LLVMContext &Context = SE.getContext();
6489 ConstantInt *Solution1 =
6490 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
6491 ConstantInt *Solution2 =
6492 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
6494 return std::make_pair(SE.getConstant(Solution1),
6495 SE.getConstant(Solution2));
6496 } // end APIntOps namespace
6499 /// HowFarToZero - Return the number of times a backedge comparing the specified
6500 /// value to zero will execute. If not computable, return CouldNotCompute.
6502 /// This is only used for loops with a "x != y" exit test. The exit condition is
6503 /// now expressed as a single expression, V = x-y. So the exit test is
6504 /// effectively V != 0. We know and take advantage of the fact that this
6505 /// expression only being used in a comparison by zero context.
6506 ScalarEvolution::ExitLimit
6507 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool ControlsExit) {
6508 // If the value is a constant
6509 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6510 // If the value is already zero, the branch will execute zero times.
6511 if (C->getValue()->isZero()) return C;
6512 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6515 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
6516 if (!AddRec || AddRec->getLoop() != L)
6517 return getCouldNotCompute();
6519 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
6520 // the quadratic equation to solve it.
6521 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
6522 std::pair<const SCEV *,const SCEV *> Roots =
6523 SolveQuadraticEquation(AddRec, *this);
6524 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
6525 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
6527 // Pick the smallest positive root value.
6528 if (ConstantInt *CB =
6529 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
6532 if (!CB->getZExtValue())
6533 std::swap(R1, R2); // R1 is the minimum root now.
6535 // We can only use this value if the chrec ends up with an exact zero
6536 // value at this index. When solving for "X*X != 5", for example, we
6537 // should not accept a root of 2.
6538 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
6540 return R1; // We found a quadratic root!
6543 return getCouldNotCompute();
6546 // Otherwise we can only handle this if it is affine.
6547 if (!AddRec->isAffine())
6548 return getCouldNotCompute();
6550 // If this is an affine expression, the execution count of this branch is
6551 // the minimum unsigned root of the following equation:
6553 // Start + Step*N = 0 (mod 2^BW)
6557 // Step*N = -Start (mod 2^BW)
6559 // where BW is the common bit width of Start and Step.
6561 // Get the initial value for the loop.
6562 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
6563 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
6565 // For now we handle only constant steps.
6567 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
6568 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
6569 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
6570 // We have not yet seen any such cases.
6571 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
6572 if (!StepC || StepC->getValue()->equalsInt(0))
6573 return getCouldNotCompute();
6575 // For positive steps (counting up until unsigned overflow):
6576 // N = -Start/Step (as unsigned)
6577 // For negative steps (counting down to zero):
6579 // First compute the unsigned distance from zero in the direction of Step.
6580 bool CountDown = StepC->getValue()->getValue().isNegative();
6581 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
6583 // Handle unitary steps, which cannot wraparound.
6584 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
6585 // N = Distance (as unsigned)
6586 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
6587 ConstantRange CR = getUnsignedRange(Start);
6588 const SCEV *MaxBECount;
6589 if (!CountDown && CR.getUnsignedMin().isMinValue())
6590 // When counting up, the worst starting value is 1, not 0.
6591 MaxBECount = CR.getUnsignedMax().isMinValue()
6592 ? getConstant(APInt::getMinValue(CR.getBitWidth()))
6593 : getConstant(APInt::getMaxValue(CR.getBitWidth()));
6595 MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
6596 : -CR.getUnsignedMin());
6597 return ExitLimit(Distance, MaxBECount);
6600 // As a special case, handle the instance where Step is a positive power of
6601 // two. In this case, determining whether Step divides Distance evenly can be
6602 // done by counting and comparing the number of trailing zeros of Step and
6605 const APInt &StepV = StepC->getValue()->getValue();
6606 // StepV.isPowerOf2() returns true if StepV is an positive power of two. It
6607 // also returns true if StepV is maximally negative (eg, INT_MIN), but that
6608 // case is not handled as this code is guarded by !CountDown.
6609 if (StepV.isPowerOf2() &&
6610 GetMinTrailingZeros(Distance) >= StepV.countTrailingZeros()) {
6611 // Here we've constrained the equation to be of the form
6613 // 2^(N + k) * Distance' = (StepV == 2^N) * X (mod 2^W) ... (0)
6615 // where we're operating on a W bit wide integer domain and k is
6616 // non-negative. The smallest unsigned solution for X is the trip count.
6618 // (0) is equivalent to:
6620 // 2^(N + k) * Distance' - 2^N * X = L * 2^W
6621 // <=> 2^N(2^k * Distance' - X) = L * 2^(W - N) * 2^N
6622 // <=> 2^k * Distance' - X = L * 2^(W - N)
6623 // <=> 2^k * Distance' = L * 2^(W - N) + X ... (1)
6625 // The smallest X satisfying (1) is unsigned remainder of dividing the LHS
6628 // <=> X = 2^k * Distance' URem 2^(W - N) ... (2)
6630 // E.g. say we're solving
6632 // 2 * Val = 2 * X (in i8) ... (3)
6634 // then from (2), we get X = Val URem i8 128 (k = 0 in this case).
6636 // Note: It is tempting to solve (3) by setting X = Val, but Val is not
6637 // necessarily the smallest unsigned value of X that satisfies (3).
6638 // E.g. if Val is i8 -127 then the smallest value of X that satisfies (3)
6639 // is i8 1, not i8 -127
6641 const auto *ModuloResult = getUDivExactExpr(Distance, Step);
6643 // Since SCEV does not have a URem node, we construct one using a truncate
6644 // and a zero extend.
6646 unsigned NarrowWidth = StepV.getBitWidth() - StepV.countTrailingZeros();
6647 auto *NarrowTy = IntegerType::get(getContext(), NarrowWidth);
6648 auto *WideTy = Distance->getType();
6650 return getZeroExtendExpr(getTruncateExpr(ModuloResult, NarrowTy), WideTy);
6654 // If the condition controls loop exit (the loop exits only if the expression
6655 // is true) and the addition is no-wrap we can use unsigned divide to
6656 // compute the backedge count. In this case, the step may not divide the
6657 // distance, but we don't care because if the condition is "missed" the loop
6658 // will have undefined behavior due to wrapping.
6659 if (ControlsExit && AddRec->getNoWrapFlags(SCEV::FlagNW)) {
6661 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6662 return ExitLimit(Exact, Exact);
6665 // Then, try to solve the above equation provided that Start is constant.
6666 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
6667 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
6668 -StartC->getValue()->getValue(),
6670 return getCouldNotCompute();
6673 /// HowFarToNonZero - Return the number of times a backedge checking the
6674 /// specified value for nonzero will execute. If not computable, return
6676 ScalarEvolution::ExitLimit
6677 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
6678 // Loops that look like: while (X == 0) are very strange indeed. We don't
6679 // handle them yet except for the trivial case. This could be expanded in the
6680 // future as needed.
6682 // If the value is a constant, check to see if it is known to be non-zero
6683 // already. If so, the backedge will execute zero times.
6684 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6685 if (!C->getValue()->isNullValue())
6686 return getZero(C->getType());
6687 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6690 // We could implement others, but I really doubt anyone writes loops like
6691 // this, and if they did, they would already be constant folded.
6692 return getCouldNotCompute();
6695 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
6696 /// (which may not be an immediate predecessor) which has exactly one
6697 /// successor from which BB is reachable, or null if no such block is
6700 std::pair<BasicBlock *, BasicBlock *>
6701 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
6702 // If the block has a unique predecessor, then there is no path from the
6703 // predecessor to the block that does not go through the direct edge
6704 // from the predecessor to the block.
6705 if (BasicBlock *Pred = BB->getSinglePredecessor())
6706 return std::make_pair(Pred, BB);
6708 // A loop's header is defined to be a block that dominates the loop.
6709 // If the header has a unique predecessor outside the loop, it must be
6710 // a block that has exactly one successor that can reach the loop.
6711 if (Loop *L = LI.getLoopFor(BB))
6712 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
6714 return std::pair<BasicBlock *, BasicBlock *>();
6717 /// HasSameValue - SCEV structural equivalence is usually sufficient for
6718 /// testing whether two expressions are equal, however for the purposes of
6719 /// looking for a condition guarding a loop, it can be useful to be a little
6720 /// more general, since a front-end may have replicated the controlling
6723 static bool HasSameValue(const SCEV *A, const SCEV *B) {
6724 // Quick check to see if they are the same SCEV.
6725 if (A == B) return true;
6727 auto ComputesEqualValues = [](const Instruction *A, const Instruction *B) {
6728 // Not all instructions that are "identical" compute the same value. For
6729 // instance, two distinct alloca instructions allocating the same type are
6730 // identical and do not read memory; but compute distinct values.
6731 return A->isIdenticalTo(B) && (isa<BinaryOperator>(A) || isa<GetElementPtrInst>(A));
6734 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
6735 // two different instructions with the same value. Check for this case.
6736 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
6737 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
6738 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
6739 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
6740 if (ComputesEqualValues(AI, BI))
6743 // Otherwise assume they may have a different value.
6747 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
6748 /// predicate Pred. Return true iff any changes were made.
6750 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
6751 const SCEV *&LHS, const SCEV *&RHS,
6753 bool Changed = false;
6755 // If we hit the max recursion limit bail out.
6759 // Canonicalize a constant to the right side.
6760 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
6761 // Check for both operands constant.
6762 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
6763 if (ConstantExpr::getICmp(Pred,
6765 RHSC->getValue())->isNullValue())
6766 goto trivially_false;
6768 goto trivially_true;
6770 // Otherwise swap the operands to put the constant on the right.
6771 std::swap(LHS, RHS);
6772 Pred = ICmpInst::getSwappedPredicate(Pred);
6776 // If we're comparing an addrec with a value which is loop-invariant in the
6777 // addrec's loop, put the addrec on the left. Also make a dominance check,
6778 // as both operands could be addrecs loop-invariant in each other's loop.
6779 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
6780 const Loop *L = AR->getLoop();
6781 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
6782 std::swap(LHS, RHS);
6783 Pred = ICmpInst::getSwappedPredicate(Pred);
6788 // If there's a constant operand, canonicalize comparisons with boundary
6789 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
6790 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
6791 const APInt &RA = RC->getValue()->getValue();
6793 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6794 case ICmpInst::ICMP_EQ:
6795 case ICmpInst::ICMP_NE:
6796 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
6798 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
6799 if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
6800 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
6801 ME->getOperand(0)->isAllOnesValue()) {
6802 RHS = AE->getOperand(1);
6803 LHS = ME->getOperand(1);
6807 case ICmpInst::ICMP_UGE:
6808 if ((RA - 1).isMinValue()) {
6809 Pred = ICmpInst::ICMP_NE;
6810 RHS = getConstant(RA - 1);
6814 if (RA.isMaxValue()) {
6815 Pred = ICmpInst::ICMP_EQ;
6819 if (RA.isMinValue()) goto trivially_true;
6821 Pred = ICmpInst::ICMP_UGT;
6822 RHS = getConstant(RA - 1);
6825 case ICmpInst::ICMP_ULE:
6826 if ((RA + 1).isMaxValue()) {
6827 Pred = ICmpInst::ICMP_NE;
6828 RHS = getConstant(RA + 1);
6832 if (RA.isMinValue()) {
6833 Pred = ICmpInst::ICMP_EQ;
6837 if (RA.isMaxValue()) goto trivially_true;
6839 Pred = ICmpInst::ICMP_ULT;
6840 RHS = getConstant(RA + 1);
6843 case ICmpInst::ICMP_SGE:
6844 if ((RA - 1).isMinSignedValue()) {
6845 Pred = ICmpInst::ICMP_NE;
6846 RHS = getConstant(RA - 1);
6850 if (RA.isMaxSignedValue()) {
6851 Pred = ICmpInst::ICMP_EQ;
6855 if (RA.isMinSignedValue()) goto trivially_true;
6857 Pred = ICmpInst::ICMP_SGT;
6858 RHS = getConstant(RA - 1);
6861 case ICmpInst::ICMP_SLE:
6862 if ((RA + 1).isMaxSignedValue()) {
6863 Pred = ICmpInst::ICMP_NE;
6864 RHS = getConstant(RA + 1);
6868 if (RA.isMinSignedValue()) {
6869 Pred = ICmpInst::ICMP_EQ;
6873 if (RA.isMaxSignedValue()) goto trivially_true;
6875 Pred = ICmpInst::ICMP_SLT;
6876 RHS = getConstant(RA + 1);
6879 case ICmpInst::ICMP_UGT:
6880 if (RA.isMinValue()) {
6881 Pred = ICmpInst::ICMP_NE;
6885 if ((RA + 1).isMaxValue()) {
6886 Pred = ICmpInst::ICMP_EQ;
6887 RHS = getConstant(RA + 1);
6891 if (RA.isMaxValue()) goto trivially_false;
6893 case ICmpInst::ICMP_ULT:
6894 if (RA.isMaxValue()) {
6895 Pred = ICmpInst::ICMP_NE;
6899 if ((RA - 1).isMinValue()) {
6900 Pred = ICmpInst::ICMP_EQ;
6901 RHS = getConstant(RA - 1);
6905 if (RA.isMinValue()) goto trivially_false;
6907 case ICmpInst::ICMP_SGT:
6908 if (RA.isMinSignedValue()) {
6909 Pred = ICmpInst::ICMP_NE;
6913 if ((RA + 1).isMaxSignedValue()) {
6914 Pred = ICmpInst::ICMP_EQ;
6915 RHS = getConstant(RA + 1);
6919 if (RA.isMaxSignedValue()) goto trivially_false;
6921 case ICmpInst::ICMP_SLT:
6922 if (RA.isMaxSignedValue()) {
6923 Pred = ICmpInst::ICMP_NE;
6927 if ((RA - 1).isMinSignedValue()) {
6928 Pred = ICmpInst::ICMP_EQ;
6929 RHS = getConstant(RA - 1);
6933 if (RA.isMinSignedValue()) goto trivially_false;
6938 // Check for obvious equality.
6939 if (HasSameValue(LHS, RHS)) {
6940 if (ICmpInst::isTrueWhenEqual(Pred))
6941 goto trivially_true;
6942 if (ICmpInst::isFalseWhenEqual(Pred))
6943 goto trivially_false;
6946 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
6947 // adding or subtracting 1 from one of the operands.
6949 case ICmpInst::ICMP_SLE:
6950 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
6951 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6953 Pred = ICmpInst::ICMP_SLT;
6955 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
6956 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6958 Pred = ICmpInst::ICMP_SLT;
6962 case ICmpInst::ICMP_SGE:
6963 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
6964 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6966 Pred = ICmpInst::ICMP_SGT;
6968 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
6969 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6971 Pred = ICmpInst::ICMP_SGT;
6975 case ICmpInst::ICMP_ULE:
6976 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
6977 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6979 Pred = ICmpInst::ICMP_ULT;
6981 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
6982 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6984 Pred = ICmpInst::ICMP_ULT;
6988 case ICmpInst::ICMP_UGE:
6989 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
6990 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6992 Pred = ICmpInst::ICMP_UGT;
6994 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
6995 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6997 Pred = ICmpInst::ICMP_UGT;
7005 // TODO: More simplifications are possible here.
7007 // Recursively simplify until we either hit a recursion limit or nothing
7010 return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1);
7016 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
7017 Pred = ICmpInst::ICMP_EQ;
7022 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
7023 Pred = ICmpInst::ICMP_NE;
7027 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
7028 return getSignedRange(S).getSignedMax().isNegative();
7031 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
7032 return getSignedRange(S).getSignedMin().isStrictlyPositive();
7035 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
7036 return !getSignedRange(S).getSignedMin().isNegative();
7039 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
7040 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
7043 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
7044 return isKnownNegative(S) || isKnownPositive(S);
7047 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
7048 const SCEV *LHS, const SCEV *RHS) {
7049 // Canonicalize the inputs first.
7050 (void)SimplifyICmpOperands(Pred, LHS, RHS);
7052 // If LHS or RHS is an addrec, check to see if the condition is true in
7053 // every iteration of the loop.
7054 // If LHS and RHS are both addrec, both conditions must be true in
7055 // every iteration of the loop.
7056 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
7057 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
7058 bool LeftGuarded = false;
7059 bool RightGuarded = false;
7061 const Loop *L = LAR->getLoop();
7062 if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
7063 isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
7064 if (!RAR) return true;
7069 const Loop *L = RAR->getLoop();
7070 if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
7071 isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
7072 if (!LAR) return true;
7073 RightGuarded = true;
7076 if (LeftGuarded && RightGuarded)
7079 if (isKnownPredicateViaSplitting(Pred, LHS, RHS))
7082 // Otherwise see what can be done with known constant ranges.
7083 return isKnownPredicateWithRanges(Pred, LHS, RHS);
7086 bool ScalarEvolution::isMonotonicPredicate(const SCEVAddRecExpr *LHS,
7087 ICmpInst::Predicate Pred,
7089 bool Result = isMonotonicPredicateImpl(LHS, Pred, Increasing);
7092 // Verify an invariant: inverting the predicate should turn a monotonically
7093 // increasing change to a monotonically decreasing one, and vice versa.
7094 bool IncreasingSwapped;
7095 bool ResultSwapped = isMonotonicPredicateImpl(
7096 LHS, ICmpInst::getSwappedPredicate(Pred), IncreasingSwapped);
7098 assert(Result == ResultSwapped && "should be able to analyze both!");
7100 assert(Increasing == !IncreasingSwapped &&
7101 "monotonicity should flip as we flip the predicate");
7107 bool ScalarEvolution::isMonotonicPredicateImpl(const SCEVAddRecExpr *LHS,
7108 ICmpInst::Predicate Pred,
7111 // A zero step value for LHS means the induction variable is essentially a
7112 // loop invariant value. We don't really depend on the predicate actually
7113 // flipping from false to true (for increasing predicates, and the other way
7114 // around for decreasing predicates), all we care about is that *if* the
7115 // predicate changes then it only changes from false to true.
7117 // A zero step value in itself is not very useful, but there may be places
7118 // where SCEV can prove X >= 0 but not prove X > 0, so it is helpful to be
7119 // as general as possible.
7123 return false; // Conservative answer
7125 case ICmpInst::ICMP_UGT:
7126 case ICmpInst::ICMP_UGE:
7127 case ICmpInst::ICMP_ULT:
7128 case ICmpInst::ICMP_ULE:
7129 if (!LHS->getNoWrapFlags(SCEV::FlagNUW))
7132 Increasing = Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE;
7135 case ICmpInst::ICMP_SGT:
7136 case ICmpInst::ICMP_SGE:
7137 case ICmpInst::ICMP_SLT:
7138 case ICmpInst::ICMP_SLE: {
7139 if (!LHS->getNoWrapFlags(SCEV::FlagNSW))
7142 const SCEV *Step = LHS->getStepRecurrence(*this);
7144 if (isKnownNonNegative(Step)) {
7145 Increasing = Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE;
7149 if (isKnownNonPositive(Step)) {
7150 Increasing = Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE;
7159 llvm_unreachable("switch has default clause!");
7162 bool ScalarEvolution::isLoopInvariantPredicate(
7163 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, const Loop *L,
7164 ICmpInst::Predicate &InvariantPred, const SCEV *&InvariantLHS,
7165 const SCEV *&InvariantRHS) {
7167 // If there is a loop-invariant, force it into the RHS, otherwise bail out.
7168 if (!isLoopInvariant(RHS, L)) {
7169 if (!isLoopInvariant(LHS, L))
7172 std::swap(LHS, RHS);
7173 Pred = ICmpInst::getSwappedPredicate(Pred);
7176 const SCEVAddRecExpr *ArLHS = dyn_cast<SCEVAddRecExpr>(LHS);
7177 if (!ArLHS || ArLHS->getLoop() != L)
7181 if (!isMonotonicPredicate(ArLHS, Pred, Increasing))
7184 // If the predicate "ArLHS `Pred` RHS" monotonically increases from false to
7185 // true as the loop iterates, and the backedge is control dependent on
7186 // "ArLHS `Pred` RHS" == true then we can reason as follows:
7188 // * if the predicate was false in the first iteration then the predicate
7189 // is never evaluated again, since the loop exits without taking the
7191 // * if the predicate was true in the first iteration then it will
7192 // continue to be true for all future iterations since it is
7193 // monotonically increasing.
7195 // For both the above possibilities, we can replace the loop varying
7196 // predicate with its value on the first iteration of the loop (which is
7199 // A similar reasoning applies for a monotonically decreasing predicate, by
7200 // replacing true with false and false with true in the above two bullets.
7202 auto P = Increasing ? Pred : ICmpInst::getInversePredicate(Pred);
7204 if (!isLoopBackedgeGuardedByCond(L, P, LHS, RHS))
7207 InvariantPred = Pred;
7208 InvariantLHS = ArLHS->getStart();
7214 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
7215 const SCEV *LHS, const SCEV *RHS) {
7216 if (HasSameValue(LHS, RHS))
7217 return ICmpInst::isTrueWhenEqual(Pred);
7219 // This code is split out from isKnownPredicate because it is called from
7220 // within isLoopEntryGuardedByCond.
7223 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
7224 case ICmpInst::ICMP_SGT:
7225 std::swap(LHS, RHS);
7226 case ICmpInst::ICMP_SLT: {
7227 ConstantRange LHSRange = getSignedRange(LHS);
7228 ConstantRange RHSRange = getSignedRange(RHS);
7229 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
7231 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
7235 case ICmpInst::ICMP_SGE:
7236 std::swap(LHS, RHS);
7237 case ICmpInst::ICMP_SLE: {
7238 ConstantRange LHSRange = getSignedRange(LHS);
7239 ConstantRange RHSRange = getSignedRange(RHS);
7240 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
7242 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
7246 case ICmpInst::ICMP_UGT:
7247 std::swap(LHS, RHS);
7248 case ICmpInst::ICMP_ULT: {
7249 ConstantRange LHSRange = getUnsignedRange(LHS);
7250 ConstantRange RHSRange = getUnsignedRange(RHS);
7251 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
7253 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
7257 case ICmpInst::ICMP_UGE:
7258 std::swap(LHS, RHS);
7259 case ICmpInst::ICMP_ULE: {
7260 ConstantRange LHSRange = getUnsignedRange(LHS);
7261 ConstantRange RHSRange = getUnsignedRange(RHS);
7262 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
7264 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
7268 case ICmpInst::ICMP_NE: {
7269 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
7271 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
7274 const SCEV *Diff = getMinusSCEV(LHS, RHS);
7275 if (isKnownNonZero(Diff))
7279 case ICmpInst::ICMP_EQ:
7280 // The check at the top of the function catches the case where
7281 // the values are known to be equal.
7287 bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
7291 // Match Result to (X + Y)<ExpectedFlags> where Y is a constant integer.
7292 // Return Y via OutY.
7293 auto MatchBinaryAddToConst =
7294 [this](const SCEV *Result, const SCEV *X, APInt &OutY,
7295 SCEV::NoWrapFlags ExpectedFlags) {
7296 const SCEV *NonConstOp, *ConstOp;
7297 SCEV::NoWrapFlags FlagsPresent;
7299 if (!splitBinaryAdd(Result, ConstOp, NonConstOp, FlagsPresent) ||
7300 !isa<SCEVConstant>(ConstOp) || NonConstOp != X)
7303 OutY = cast<SCEVConstant>(ConstOp)->getValue()->getValue();
7304 return (FlagsPresent & ExpectedFlags) == ExpectedFlags;
7313 case ICmpInst::ICMP_SGE:
7314 std::swap(LHS, RHS);
7315 case ICmpInst::ICMP_SLE:
7316 // X s<= (X + C)<nsw> if C >= 0
7317 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
7320 // (X + C)<nsw> s<= X if C <= 0
7321 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) &&
7322 !C.isStrictlyPositive())
7325 case ICmpInst::ICMP_SGT:
7326 std::swap(LHS, RHS);
7327 case ICmpInst::ICMP_SLT:
7328 // X s< (X + C)<nsw> if C > 0
7329 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) &&
7330 C.isStrictlyPositive())
7333 // (X + C)<nsw> s< X if C < 0
7334 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
7341 bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
7344 if (Pred != ICmpInst::ICMP_ULT || ProvingSplitPredicate)
7347 // Allowing arbitrary number of activations of isKnownPredicateViaSplitting on
7348 // the stack can result in exponential time complexity.
7349 SaveAndRestore<bool> Restore(ProvingSplitPredicate, true);
7351 // If L >= 0 then I `ult` L <=> I >= 0 && I `slt` L
7353 // To prove L >= 0 we use isKnownNonNegative whereas to prove I >= 0 we use
7354 // isKnownPredicate. isKnownPredicate is more powerful, but also more
7355 // expensive; and using isKnownNonNegative(RHS) is sufficient for most of the
7356 // interesting cases seen in practice. We can consider "upgrading" L >= 0 to
7357 // use isKnownPredicate later if needed.
7358 if (isKnownNonNegative(RHS) &&
7359 isKnownPredicate(CmpInst::ICMP_SGE, LHS, getZero(LHS->getType())) &&
7360 isKnownPredicate(CmpInst::ICMP_SLT, LHS, RHS))
7366 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
7367 /// protected by a conditional between LHS and RHS. This is used to
7368 /// to eliminate casts.
7370 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
7371 ICmpInst::Predicate Pred,
7372 const SCEV *LHS, const SCEV *RHS) {
7373 // Interpret a null as meaning no loop, where there is obviously no guard
7374 // (interprocedural conditions notwithstanding).
7375 if (!L) return true;
7377 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
7379 BasicBlock *Latch = L->getLoopLatch();
7383 BranchInst *LoopContinuePredicate =
7384 dyn_cast<BranchInst>(Latch->getTerminator());
7385 if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
7386 isImpliedCond(Pred, LHS, RHS,
7387 LoopContinuePredicate->getCondition(),
7388 LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
7391 // We don't want more than one activation of the following loops on the stack
7392 // -- that can lead to O(n!) time complexity.
7393 if (WalkingBEDominatingConds)
7396 SaveAndRestore<bool> ClearOnExit(WalkingBEDominatingConds, true);
7398 // See if we can exploit a trip count to prove the predicate.
7399 const auto &BETakenInfo = getBackedgeTakenInfo(L);
7400 const SCEV *LatchBECount = BETakenInfo.getExact(Latch, this);
7401 if (LatchBECount != getCouldNotCompute()) {
7402 // We know that Latch branches back to the loop header exactly
7403 // LatchBECount times. This means the backdege condition at Latch is
7404 // equivalent to "{0,+,1} u< LatchBECount".
7405 Type *Ty = LatchBECount->getType();
7406 auto NoWrapFlags = SCEV::NoWrapFlags(SCEV::FlagNUW | SCEV::FlagNW);
7407 const SCEV *LoopCounter =
7408 getAddRecExpr(getZero(Ty), getOne(Ty), L, NoWrapFlags);
7409 if (isImpliedCond(Pred, LHS, RHS, ICmpInst::ICMP_ULT, LoopCounter,
7414 // Check conditions due to any @llvm.assume intrinsics.
7415 for (auto &AssumeVH : AC.assumptions()) {
7418 auto *CI = cast<CallInst>(AssumeVH);
7419 if (!DT.dominates(CI, Latch->getTerminator()))
7422 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
7426 // If the loop is not reachable from the entry block, we risk running into an
7427 // infinite loop as we walk up into the dom tree. These loops do not matter
7428 // anyway, so we just return a conservative answer when we see them.
7429 if (!DT.isReachableFromEntry(L->getHeader()))
7432 for (DomTreeNode *DTN = DT[Latch], *HeaderDTN = DT[L->getHeader()];
7433 DTN != HeaderDTN; DTN = DTN->getIDom()) {
7435 assert(DTN && "should reach the loop header before reaching the root!");
7437 BasicBlock *BB = DTN->getBlock();
7438 BasicBlock *PBB = BB->getSinglePredecessor();
7442 BranchInst *ContinuePredicate = dyn_cast<BranchInst>(PBB->getTerminator());
7443 if (!ContinuePredicate || !ContinuePredicate->isConditional())
7446 Value *Condition = ContinuePredicate->getCondition();
7448 // If we have an edge `E` within the loop body that dominates the only
7449 // latch, the condition guarding `E` also guards the backedge. This
7450 // reasoning works only for loops with a single latch.
7452 BasicBlockEdge DominatingEdge(PBB, BB);
7453 if (DominatingEdge.isSingleEdge()) {
7454 // We're constructively (and conservatively) enumerating edges within the
7455 // loop body that dominate the latch. The dominator tree better agree
7457 assert(DT.dominates(DominatingEdge, Latch) && "should be!");
7459 if (isImpliedCond(Pred, LHS, RHS, Condition,
7460 BB != ContinuePredicate->getSuccessor(0)))
7468 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
7469 /// by a conditional between LHS and RHS. This is used to help avoid max
7470 /// expressions in loop trip counts, and to eliminate casts.
7472 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
7473 ICmpInst::Predicate Pred,
7474 const SCEV *LHS, const SCEV *RHS) {
7475 // Interpret a null as meaning no loop, where there is obviously no guard
7476 // (interprocedural conditions notwithstanding).
7477 if (!L) return false;
7479 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
7481 // Starting at the loop predecessor, climb up the predecessor chain, as long
7482 // as there are predecessors that can be found that have unique successors
7483 // leading to the original header.
7484 for (std::pair<BasicBlock *, BasicBlock *>
7485 Pair(L->getLoopPredecessor(), L->getHeader());
7487 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
7489 BranchInst *LoopEntryPredicate =
7490 dyn_cast<BranchInst>(Pair.first->getTerminator());
7491 if (!LoopEntryPredicate ||
7492 LoopEntryPredicate->isUnconditional())
7495 if (isImpliedCond(Pred, LHS, RHS,
7496 LoopEntryPredicate->getCondition(),
7497 LoopEntryPredicate->getSuccessor(0) != Pair.second))
7501 // Check conditions due to any @llvm.assume intrinsics.
7502 for (auto &AssumeVH : AC.assumptions()) {
7505 auto *CI = cast<CallInst>(AssumeVH);
7506 if (!DT.dominates(CI, L->getHeader()))
7509 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
7517 /// RAII wrapper to prevent recursive application of isImpliedCond.
7518 /// ScalarEvolution's PendingLoopPredicates set must be empty unless we are
7519 /// currently evaluating isImpliedCond.
7520 struct MarkPendingLoopPredicate {
7522 DenseSet<Value*> &LoopPreds;
7525 MarkPendingLoopPredicate(Value *C, DenseSet<Value*> &LP)
7526 : Cond(C), LoopPreds(LP) {
7527 Pending = !LoopPreds.insert(Cond).second;
7529 ~MarkPendingLoopPredicate() {
7531 LoopPreds.erase(Cond);
7534 } // end anonymous namespace
7536 /// isImpliedCond - Test whether the condition described by Pred, LHS,
7537 /// and RHS is true whenever the given Cond value evaluates to true.
7538 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
7539 const SCEV *LHS, const SCEV *RHS,
7540 Value *FoundCondValue,
7542 MarkPendingLoopPredicate Mark(FoundCondValue, PendingLoopPredicates);
7546 // Recursively handle And and Or conditions.
7547 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
7548 if (BO->getOpcode() == Instruction::And) {
7550 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
7551 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
7552 } else if (BO->getOpcode() == Instruction::Or) {
7554 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
7555 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
7559 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
7560 if (!ICI) return false;
7562 // Now that we found a conditional branch that dominates the loop or controls
7563 // the loop latch. Check to see if it is the comparison we are looking for.
7564 ICmpInst::Predicate FoundPred;
7566 FoundPred = ICI->getInversePredicate();
7568 FoundPred = ICI->getPredicate();
7570 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
7571 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
7573 return isImpliedCond(Pred, LHS, RHS, FoundPred, FoundLHS, FoundRHS);
7576 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS,
7578 ICmpInst::Predicate FoundPred,
7579 const SCEV *FoundLHS,
7580 const SCEV *FoundRHS) {
7581 // Balance the types.
7582 if (getTypeSizeInBits(LHS->getType()) <
7583 getTypeSizeInBits(FoundLHS->getType())) {
7584 if (CmpInst::isSigned(Pred)) {
7585 LHS = getSignExtendExpr(LHS, FoundLHS->getType());
7586 RHS = getSignExtendExpr(RHS, FoundLHS->getType());
7588 LHS = getZeroExtendExpr(LHS, FoundLHS->getType());
7589 RHS = getZeroExtendExpr(RHS, FoundLHS->getType());
7591 } else if (getTypeSizeInBits(LHS->getType()) >
7592 getTypeSizeInBits(FoundLHS->getType())) {
7593 if (CmpInst::isSigned(FoundPred)) {
7594 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
7595 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
7597 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
7598 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
7602 // Canonicalize the query to match the way instcombine will have
7603 // canonicalized the comparison.
7604 if (SimplifyICmpOperands(Pred, LHS, RHS))
7606 return CmpInst::isTrueWhenEqual(Pred);
7607 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
7608 if (FoundLHS == FoundRHS)
7609 return CmpInst::isFalseWhenEqual(FoundPred);
7611 // Check to see if we can make the LHS or RHS match.
7612 if (LHS == FoundRHS || RHS == FoundLHS) {
7613 if (isa<SCEVConstant>(RHS)) {
7614 std::swap(FoundLHS, FoundRHS);
7615 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
7617 std::swap(LHS, RHS);
7618 Pred = ICmpInst::getSwappedPredicate(Pred);
7622 // Check whether the found predicate is the same as the desired predicate.
7623 if (FoundPred == Pred)
7624 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
7626 // Check whether swapping the found predicate makes it the same as the
7627 // desired predicate.
7628 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
7629 if (isa<SCEVConstant>(RHS))
7630 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
7632 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
7633 RHS, LHS, FoundLHS, FoundRHS);
7636 // Unsigned comparison is the same as signed comparison when both the operands
7637 // are non-negative.
7638 if (CmpInst::isUnsigned(FoundPred) &&
7639 CmpInst::getSignedPredicate(FoundPred) == Pred &&
7640 isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS))
7641 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
7643 // Check if we can make progress by sharpening ranges.
7644 if (FoundPred == ICmpInst::ICMP_NE &&
7645 (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
7647 const SCEVConstant *C = nullptr;
7648 const SCEV *V = nullptr;
7650 if (isa<SCEVConstant>(FoundLHS)) {
7651 C = cast<SCEVConstant>(FoundLHS);
7654 C = cast<SCEVConstant>(FoundRHS);
7658 // The guarding predicate tells us that C != V. If the known range
7659 // of V is [C, t), we can sharpen the range to [C + 1, t). The
7660 // range we consider has to correspond to same signedness as the
7661 // predicate we're interested in folding.
7663 APInt Min = ICmpInst::isSigned(Pred) ?
7664 getSignedRange(V).getSignedMin() : getUnsignedRange(V).getUnsignedMin();
7666 if (Min == C->getValue()->getValue()) {
7667 // Given (V >= Min && V != Min) we conclude V >= (Min + 1).
7668 // This is true even if (Min + 1) wraps around -- in case of
7669 // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)).
7671 APInt SharperMin = Min + 1;
7674 case ICmpInst::ICMP_SGE:
7675 case ICmpInst::ICMP_UGE:
7676 // We know V `Pred` SharperMin. If this implies LHS `Pred`
7678 if (isImpliedCondOperands(Pred, LHS, RHS, V,
7679 getConstant(SharperMin)))
7682 case ICmpInst::ICMP_SGT:
7683 case ICmpInst::ICMP_UGT:
7684 // We know from the range information that (V `Pred` Min ||
7685 // V == Min). We know from the guarding condition that !(V
7686 // == Min). This gives us
7688 // V `Pred` Min || V == Min && !(V == Min)
7691 // If V `Pred` Min implies LHS `Pred` RHS, we're done.
7693 if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
7703 // Check whether the actual condition is beyond sufficient.
7704 if (FoundPred == ICmpInst::ICMP_EQ)
7705 if (ICmpInst::isTrueWhenEqual(Pred))
7706 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
7708 if (Pred == ICmpInst::ICMP_NE)
7709 if (!ICmpInst::isTrueWhenEqual(FoundPred))
7710 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
7713 // Otherwise assume the worst.
7717 bool ScalarEvolution::splitBinaryAdd(const SCEV *Expr,
7718 const SCEV *&L, const SCEV *&R,
7719 SCEV::NoWrapFlags &Flags) {
7720 const auto *AE = dyn_cast<SCEVAddExpr>(Expr);
7721 if (!AE || AE->getNumOperands() != 2)
7724 L = AE->getOperand(0);
7725 R = AE->getOperand(1);
7726 Flags = AE->getNoWrapFlags();
7730 bool ScalarEvolution::computeConstantDifference(const SCEV *Less,
7733 // We avoid subtracting expressions here because this function is usually
7734 // fairly deep in the call stack (i.e. is called many times).
7736 if (isa<SCEVAddRecExpr>(Less) && isa<SCEVAddRecExpr>(More)) {
7737 const auto *LAR = cast<SCEVAddRecExpr>(Less);
7738 const auto *MAR = cast<SCEVAddRecExpr>(More);
7740 if (LAR->getLoop() != MAR->getLoop())
7743 // We look at affine expressions only; not for correctness but to keep
7744 // getStepRecurrence cheap.
7745 if (!LAR->isAffine() || !MAR->isAffine())
7748 if (LAR->getStepRecurrence(*this) != MAR->getStepRecurrence(*this))
7751 Less = LAR->getStart();
7752 More = MAR->getStart();
7757 if (isa<SCEVConstant>(Less) && isa<SCEVConstant>(More)) {
7758 const auto &M = cast<SCEVConstant>(More)->getValue()->getValue();
7759 const auto &L = cast<SCEVConstant>(Less)->getValue()->getValue();
7765 SCEV::NoWrapFlags Flags;
7766 if (splitBinaryAdd(Less, L, R, Flags))
7767 if (const auto *LC = dyn_cast<SCEVConstant>(L))
7769 C = -(LC->getValue()->getValue());
7773 if (splitBinaryAdd(More, L, R, Flags))
7774 if (const auto *LC = dyn_cast<SCEVConstant>(L))
7776 C = LC->getValue()->getValue();
7783 bool ScalarEvolution::isImpliedCondOperandsViaNoOverflow(
7784 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS,
7785 const SCEV *FoundLHS, const SCEV *FoundRHS) {
7786 if (Pred != CmpInst::ICMP_SLT && Pred != CmpInst::ICMP_ULT)
7789 const auto *AddRecLHS = dyn_cast<SCEVAddRecExpr>(LHS);
7793 const auto *AddRecFoundLHS = dyn_cast<SCEVAddRecExpr>(FoundLHS);
7794 if (!AddRecFoundLHS)
7797 // We'd like to let SCEV reason about control dependencies, so we constrain
7798 // both the inequalities to be about add recurrences on the same loop. This
7799 // way we can use isLoopEntryGuardedByCond later.
7801 const Loop *L = AddRecFoundLHS->getLoop();
7802 if (L != AddRecLHS->getLoop())
7805 // FoundLHS u< FoundRHS u< -C => (FoundLHS + C) u< (FoundRHS + C) ... (1)
7807 // FoundLHS s< FoundRHS s< INT_MIN - C => (FoundLHS + C) s< (FoundRHS + C)
7810 // Informal proof for (2), assuming (1) [*]:
7812 // We'll also assume (A s< B) <=> ((A + INT_MIN) u< (B + INT_MIN)) ... (3)[**]
7816 // FoundLHS s< FoundRHS s< INT_MIN - C
7817 // <=> (FoundLHS + INT_MIN) u< (FoundRHS + INT_MIN) u< -C [ using (3) ]
7818 // <=> (FoundLHS + INT_MIN + C) u< (FoundRHS + INT_MIN + C) [ using (1) ]
7819 // <=> (FoundLHS + INT_MIN + C + INT_MIN) s<
7820 // (FoundRHS + INT_MIN + C + INT_MIN) [ using (3) ]
7821 // <=> FoundLHS + C s< FoundRHS + C
7823 // [*]: (1) can be proved by ruling out overflow.
7825 // [**]: This can be proved by analyzing all the four possibilities:
7826 // (A s< 0, B s< 0), (A s< 0, B s>= 0), (A s>= 0, B s< 0) and
7827 // (A s>= 0, B s>= 0).
7830 // Despite (2), "FoundRHS s< INT_MIN - C" does not mean that "FoundRHS + C"
7831 // will not sign underflow. For instance, say FoundLHS = (i8 -128), FoundRHS
7832 // = (i8 -127) and C = (i8 -100). Then INT_MIN - C = (i8 -28), and FoundRHS
7833 // s< (INT_MIN - C). Lack of sign overflow / underflow in "FoundRHS + C" is
7834 // neither necessary nor sufficient to prove "(FoundLHS + C) s< (FoundRHS +
7838 if (!computeConstantDifference(FoundLHS, LHS, LDiff) ||
7839 !computeConstantDifference(FoundRHS, RHS, RDiff) ||
7846 APInt FoundRHSLimit;
7848 if (Pred == CmpInst::ICMP_ULT) {
7849 FoundRHSLimit = -RDiff;
7851 assert(Pred == CmpInst::ICMP_SLT && "Checked above!");
7852 FoundRHSLimit = APInt::getSignedMinValue(getTypeSizeInBits(RHS->getType())) - RDiff;
7855 // Try to prove (1) or (2), as needed.
7856 return isLoopEntryGuardedByCond(L, Pred, FoundRHS,
7857 getConstant(FoundRHSLimit));
7860 /// isImpliedCondOperands - Test whether the condition described by Pred,
7861 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
7862 /// and FoundRHS is true.
7863 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
7864 const SCEV *LHS, const SCEV *RHS,
7865 const SCEV *FoundLHS,
7866 const SCEV *FoundRHS) {
7867 if (isImpliedCondOperandsViaRanges(Pred, LHS, RHS, FoundLHS, FoundRHS))
7870 if (isImpliedCondOperandsViaNoOverflow(Pred, LHS, RHS, FoundLHS, FoundRHS))
7873 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
7874 FoundLHS, FoundRHS) ||
7875 // ~x < ~y --> x > y
7876 isImpliedCondOperandsHelper(Pred, LHS, RHS,
7877 getNotSCEV(FoundRHS),
7878 getNotSCEV(FoundLHS));
7882 /// If Expr computes ~A, return A else return nullptr
7883 static const SCEV *MatchNotExpr(const SCEV *Expr) {
7884 const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Expr);
7885 if (!Add || Add->getNumOperands() != 2 ||
7886 !Add->getOperand(0)->isAllOnesValue())
7889 const SCEVMulExpr *AddRHS = dyn_cast<SCEVMulExpr>(Add->getOperand(1));
7890 if (!AddRHS || AddRHS->getNumOperands() != 2 ||
7891 !AddRHS->getOperand(0)->isAllOnesValue())
7894 return AddRHS->getOperand(1);
7898 /// Is MaybeMaxExpr an SMax or UMax of Candidate and some other values?
7899 template<typename MaxExprType>
7900 static bool IsMaxConsistingOf(const SCEV *MaybeMaxExpr,
7901 const SCEV *Candidate) {
7902 const MaxExprType *MaxExpr = dyn_cast<MaxExprType>(MaybeMaxExpr);
7903 if (!MaxExpr) return false;
7905 auto It = std::find(MaxExpr->op_begin(), MaxExpr->op_end(), Candidate);
7906 return It != MaxExpr->op_end();
7910 /// Is MaybeMinExpr an SMin or UMin of Candidate and some other values?
7911 template<typename MaxExprType>
7912 static bool IsMinConsistingOf(ScalarEvolution &SE,
7913 const SCEV *MaybeMinExpr,
7914 const SCEV *Candidate) {
7915 const SCEV *MaybeMaxExpr = MatchNotExpr(MaybeMinExpr);
7919 return IsMaxConsistingOf<MaxExprType>(MaybeMaxExpr, SE.getNotSCEV(Candidate));
7922 static bool IsKnownPredicateViaAddRecStart(ScalarEvolution &SE,
7923 ICmpInst::Predicate Pred,
7924 const SCEV *LHS, const SCEV *RHS) {
7926 // If both sides are affine addrecs for the same loop, with equal
7927 // steps, and we know the recurrences don't wrap, then we only
7928 // need to check the predicate on the starting values.
7930 if (!ICmpInst::isRelational(Pred))
7933 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
7936 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
7939 if (LAR->getLoop() != RAR->getLoop())
7941 if (!LAR->isAffine() || !RAR->isAffine())
7944 if (LAR->getStepRecurrence(SE) != RAR->getStepRecurrence(SE))
7947 SCEV::NoWrapFlags NW = ICmpInst::isSigned(Pred) ?
7948 SCEV::FlagNSW : SCEV::FlagNUW;
7949 if (!LAR->getNoWrapFlags(NW) || !RAR->getNoWrapFlags(NW))
7952 return SE.isKnownPredicate(Pred, LAR->getStart(), RAR->getStart());
7955 /// Is LHS `Pred` RHS true on the virtue of LHS or RHS being a Min or Max
7957 static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE,
7958 ICmpInst::Predicate Pred,
7959 const SCEV *LHS, const SCEV *RHS) {
7964 case ICmpInst::ICMP_SGE:
7965 std::swap(LHS, RHS);
7967 case ICmpInst::ICMP_SLE:
7970 IsMinConsistingOf<SCEVSMaxExpr>(SE, LHS, RHS) ||
7972 IsMaxConsistingOf<SCEVSMaxExpr>(RHS, LHS);
7974 case ICmpInst::ICMP_UGE:
7975 std::swap(LHS, RHS);
7977 case ICmpInst::ICMP_ULE:
7980 IsMinConsistingOf<SCEVUMaxExpr>(SE, LHS, RHS) ||
7982 IsMaxConsistingOf<SCEVUMaxExpr>(RHS, LHS);
7985 llvm_unreachable("covered switch fell through?!");
7988 /// isImpliedCondOperandsHelper - Test whether the condition described by
7989 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
7990 /// FoundLHS, and FoundRHS is true.
7992 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
7993 const SCEV *LHS, const SCEV *RHS,
7994 const SCEV *FoundLHS,
7995 const SCEV *FoundRHS) {
7996 auto IsKnownPredicateFull =
7997 [this](ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) {
7998 return isKnownPredicateWithRanges(Pred, LHS, RHS) ||
7999 IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) ||
8000 IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) ||
8001 isKnownPredicateViaNoOverflow(Pred, LHS, RHS);
8005 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
8006 case ICmpInst::ICMP_EQ:
8007 case ICmpInst::ICMP_NE:
8008 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
8011 case ICmpInst::ICMP_SLT:
8012 case ICmpInst::ICMP_SLE:
8013 if (IsKnownPredicateFull(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
8014 IsKnownPredicateFull(ICmpInst::ICMP_SGE, RHS, FoundRHS))
8017 case ICmpInst::ICMP_SGT:
8018 case ICmpInst::ICMP_SGE:
8019 if (IsKnownPredicateFull(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
8020 IsKnownPredicateFull(ICmpInst::ICMP_SLE, RHS, FoundRHS))
8023 case ICmpInst::ICMP_ULT:
8024 case ICmpInst::ICMP_ULE:
8025 if (IsKnownPredicateFull(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
8026 IsKnownPredicateFull(ICmpInst::ICMP_UGE, RHS, FoundRHS))
8029 case ICmpInst::ICMP_UGT:
8030 case ICmpInst::ICMP_UGE:
8031 if (IsKnownPredicateFull(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
8032 IsKnownPredicateFull(ICmpInst::ICMP_ULE, RHS, FoundRHS))
8040 /// isImpliedCondOperandsViaRanges - helper function for isImpliedCondOperands.
8041 /// Tries to get cases like "X `sgt` 0 => X - 1 `sgt` -1".
8042 bool ScalarEvolution::isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred,
8045 const SCEV *FoundLHS,
8046 const SCEV *FoundRHS) {
8047 if (!isa<SCEVConstant>(RHS) || !isa<SCEVConstant>(FoundRHS))
8048 // The restriction on `FoundRHS` be lifted easily -- it exists only to
8049 // reduce the compile time impact of this optimization.
8052 const SCEVAddExpr *AddLHS = dyn_cast<SCEVAddExpr>(LHS);
8053 if (!AddLHS || AddLHS->getOperand(1) != FoundLHS ||
8054 !isa<SCEVConstant>(AddLHS->getOperand(0)))
8057 APInt ConstFoundRHS = cast<SCEVConstant>(FoundRHS)->getValue()->getValue();
8059 // `FoundLHSRange` is the range we know `FoundLHS` to be in by virtue of the
8060 // antecedent "`FoundLHS` `Pred` `FoundRHS`".
8061 ConstantRange FoundLHSRange =
8062 ConstantRange::makeAllowedICmpRegion(Pred, ConstFoundRHS);
8064 // Since `LHS` is `FoundLHS` + `AddLHS->getOperand(0)`, we can compute a range
8067 cast<SCEVConstant>(AddLHS->getOperand(0))->getValue()->getValue();
8068 ConstantRange LHSRange = FoundLHSRange.add(ConstantRange(Addend));
8070 // We can also compute the range of values for `LHS` that satisfy the
8071 // consequent, "`LHS` `Pred` `RHS`":
8072 APInt ConstRHS = cast<SCEVConstant>(RHS)->getValue()->getValue();
8073 ConstantRange SatisfyingLHSRange =
8074 ConstantRange::makeSatisfyingICmpRegion(Pred, ConstRHS);
8076 // The antecedent implies the consequent if every value of `LHS` that
8077 // satisfies the antecedent also satisfies the consequent.
8078 return SatisfyingLHSRange.contains(LHSRange);
8081 // Verify if an linear IV with positive stride can overflow when in a
8082 // less-than comparison, knowing the invariant term of the comparison, the
8083 // stride and the knowledge of NSW/NUW flags on the recurrence.
8084 bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
8085 bool IsSigned, bool NoWrap) {
8086 if (NoWrap) return false;
8088 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
8089 const SCEV *One = getOne(Stride->getType());
8092 APInt MaxRHS = getSignedRange(RHS).getSignedMax();
8093 APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
8094 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
8097 // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
8098 return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
8101 APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
8102 APInt MaxValue = APInt::getMaxValue(BitWidth);
8103 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
8106 // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
8107 return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
8110 // Verify if an linear IV with negative stride can overflow when in a
8111 // greater-than comparison, knowing the invariant term of the comparison,
8112 // the stride and the knowledge of NSW/NUW flags on the recurrence.
8113 bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
8114 bool IsSigned, bool NoWrap) {
8115 if (NoWrap) return false;
8117 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
8118 const SCEV *One = getOne(Stride->getType());
8121 APInt MinRHS = getSignedRange(RHS).getSignedMin();
8122 APInt MinValue = APInt::getSignedMinValue(BitWidth);
8123 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
8126 // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
8127 return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
8130 APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
8131 APInt MinValue = APInt::getMinValue(BitWidth);
8132 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
8135 // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
8136 return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
8139 // Compute the backedge taken count knowing the interval difference, the
8140 // stride and presence of the equality in the comparison.
8141 const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
8143 const SCEV *One = getOne(Step->getType());
8144 Delta = Equality ? getAddExpr(Delta, Step)
8145 : getAddExpr(Delta, getMinusSCEV(Step, One));
8146 return getUDivExpr(Delta, Step);
8149 /// HowManyLessThans - Return the number of times a backedge containing the
8150 /// specified less-than comparison will execute. If not computable, return
8151 /// CouldNotCompute.
8153 /// @param ControlsExit is true when the LHS < RHS condition directly controls
8154 /// the branch (loops exits only if condition is true). In this case, we can use
8155 /// NoWrapFlags to skip overflow checks.
8156 ScalarEvolution::ExitLimit
8157 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
8158 const Loop *L, bool IsSigned,
8159 bool ControlsExit) {
8160 // We handle only IV < Invariant
8161 if (!isLoopInvariant(RHS, L))
8162 return getCouldNotCompute();
8164 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
8166 // Avoid weird loops
8167 if (!IV || IV->getLoop() != L || !IV->isAffine())
8168 return getCouldNotCompute();
8170 bool NoWrap = ControlsExit &&
8171 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
8173 const SCEV *Stride = IV->getStepRecurrence(*this);
8175 // Avoid negative or zero stride values
8176 if (!isKnownPositive(Stride))
8177 return getCouldNotCompute();
8179 // Avoid proven overflow cases: this will ensure that the backedge taken count
8180 // will not generate any unsigned overflow. Relaxed no-overflow conditions
8181 // exploit NoWrapFlags, allowing to optimize in presence of undefined
8182 // behaviors like the case of C language.
8183 if (!Stride->isOne() && doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
8184 return getCouldNotCompute();
8186 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
8187 : ICmpInst::ICMP_ULT;
8188 const SCEV *Start = IV->getStart();
8189 const SCEV *End = RHS;
8190 if (!isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS)) {
8191 const SCEV *Diff = getMinusSCEV(RHS, Start);
8192 // If we have NoWrap set, then we can assume that the increment won't
8193 // overflow, in which case if RHS - Start is a constant, we don't need to
8194 // do a max operation since we can just figure it out statically
8195 if (NoWrap && isa<SCEVConstant>(Diff)) {
8196 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
8200 End = IsSigned ? getSMaxExpr(RHS, Start)
8201 : getUMaxExpr(RHS, Start);
8204 const SCEV *BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
8206 APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
8207 : getUnsignedRange(Start).getUnsignedMin();
8209 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
8210 : getUnsignedRange(Stride).getUnsignedMin();
8212 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
8213 APInt Limit = IsSigned ? APInt::getSignedMaxValue(BitWidth) - (MinStride - 1)
8214 : APInt::getMaxValue(BitWidth) - (MinStride - 1);
8216 // Although End can be a MAX expression we estimate MaxEnd considering only
8217 // the case End = RHS. This is safe because in the other case (End - Start)
8218 // is zero, leading to a zero maximum backedge taken count.
8220 IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
8221 : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
8223 const SCEV *MaxBECount;
8224 if (isa<SCEVConstant>(BECount))
8225 MaxBECount = BECount;
8227 MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
8228 getConstant(MinStride), false);
8230 if (isa<SCEVCouldNotCompute>(MaxBECount))
8231 MaxBECount = BECount;
8233 return ExitLimit(BECount, MaxBECount);
8236 ScalarEvolution::ExitLimit
8237 ScalarEvolution::HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
8238 const Loop *L, bool IsSigned,
8239 bool ControlsExit) {
8240 // We handle only IV > Invariant
8241 if (!isLoopInvariant(RHS, L))
8242 return getCouldNotCompute();
8244 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
8246 // Avoid weird loops
8247 if (!IV || IV->getLoop() != L || !IV->isAffine())
8248 return getCouldNotCompute();
8250 bool NoWrap = ControlsExit &&
8251 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
8253 const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
8255 // Avoid negative or zero stride values
8256 if (!isKnownPositive(Stride))
8257 return getCouldNotCompute();
8259 // Avoid proven overflow cases: this will ensure that the backedge taken count
8260 // will not generate any unsigned overflow. Relaxed no-overflow conditions
8261 // exploit NoWrapFlags, allowing to optimize in presence of undefined
8262 // behaviors like the case of C language.
8263 if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
8264 return getCouldNotCompute();
8266 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
8267 : ICmpInst::ICMP_UGT;
8269 const SCEV *Start = IV->getStart();
8270 const SCEV *End = RHS;
8271 if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS)) {
8272 const SCEV *Diff = getMinusSCEV(RHS, Start);
8273 // If we have NoWrap set, then we can assume that the increment won't
8274 // overflow, in which case if RHS - Start is a constant, we don't need to
8275 // do a max operation since we can just figure it out statically
8276 if (NoWrap && isa<SCEVConstant>(Diff)) {
8277 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
8278 if (!D.isNegative())
8281 End = IsSigned ? getSMinExpr(RHS, Start)
8282 : getUMinExpr(RHS, Start);
8285 const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
8287 APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
8288 : getUnsignedRange(Start).getUnsignedMax();
8290 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
8291 : getUnsignedRange(Stride).getUnsignedMin();
8293 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
8294 APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
8295 : APInt::getMinValue(BitWidth) + (MinStride - 1);
8297 // Although End can be a MIN expression we estimate MinEnd considering only
8298 // the case End = RHS. This is safe because in the other case (Start - End)
8299 // is zero, leading to a zero maximum backedge taken count.
8301 IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
8302 : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
8305 const SCEV *MaxBECount = getCouldNotCompute();
8306 if (isa<SCEVConstant>(BECount))
8307 MaxBECount = BECount;
8309 MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
8310 getConstant(MinStride), false);
8312 if (isa<SCEVCouldNotCompute>(MaxBECount))
8313 MaxBECount = BECount;
8315 return ExitLimit(BECount, MaxBECount);
8318 /// getNumIterationsInRange - Return the number of iterations of this loop that
8319 /// produce values in the specified constant range. Another way of looking at
8320 /// this is that it returns the first iteration number where the value is not in
8321 /// the condition, thus computing the exit count. If the iteration count can't
8322 /// be computed, an instance of SCEVCouldNotCompute is returned.
8323 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
8324 ScalarEvolution &SE) const {
8325 if (Range.isFullSet()) // Infinite loop.
8326 return SE.getCouldNotCompute();
8328 // If the start is a non-zero constant, shift the range to simplify things.
8329 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
8330 if (!SC->getValue()->isZero()) {
8331 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
8332 Operands[0] = SE.getZero(SC->getType());
8333 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
8334 getNoWrapFlags(FlagNW));
8335 if (const auto *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
8336 return ShiftedAddRec->getNumIterationsInRange(
8337 Range.subtract(SC->getValue()->getValue()), SE);
8338 // This is strange and shouldn't happen.
8339 return SE.getCouldNotCompute();
8342 // The only time we can solve this is when we have all constant indices.
8343 // Otherwise, we cannot determine the overflow conditions.
8344 if (std::any_of(op_begin(), op_end(),
8345 [](const SCEV *Op) { return !isa<SCEVConstant>(Op);}))
8346 return SE.getCouldNotCompute();
8348 // Okay at this point we know that all elements of the chrec are constants and
8349 // that the start element is zero.
8351 // First check to see if the range contains zero. If not, the first
8353 unsigned BitWidth = SE.getTypeSizeInBits(getType());
8354 if (!Range.contains(APInt(BitWidth, 0)))
8355 return SE.getZero(getType());
8358 // If this is an affine expression then we have this situation:
8359 // Solve {0,+,A} in Range === Ax in Range
8361 // We know that zero is in the range. If A is positive then we know that
8362 // the upper value of the range must be the first possible exit value.
8363 // If A is negative then the lower of the range is the last possible loop
8364 // value. Also note that we already checked for a full range.
8365 APInt One(BitWidth,1);
8366 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
8367 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
8369 // The exit value should be (End+A)/A.
8370 APInt ExitVal = (End + A).udiv(A);
8371 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
8373 // Evaluate at the exit value. If we really did fall out of the valid
8374 // range, then we computed our trip count, otherwise wrap around or other
8375 // things must have happened.
8376 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
8377 if (Range.contains(Val->getValue()))
8378 return SE.getCouldNotCompute(); // Something strange happened
8380 // Ensure that the previous value is in the range. This is a sanity check.
8381 assert(Range.contains(
8382 EvaluateConstantChrecAtConstant(this,
8383 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
8384 "Linear scev computation is off in a bad way!");
8385 return SE.getConstant(ExitValue);
8386 } else if (isQuadratic()) {
8387 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
8388 // quadratic equation to solve it. To do this, we must frame our problem in
8389 // terms of figuring out when zero is crossed, instead of when
8390 // Range.getUpper() is crossed.
8391 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
8392 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
8393 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
8394 // getNoWrapFlags(FlagNW)
8397 // Next, solve the constructed addrec
8398 std::pair<const SCEV *,const SCEV *> Roots =
8399 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
8400 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
8401 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
8403 // Pick the smallest positive root value.
8404 if (ConstantInt *CB =
8405 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
8406 R1->getValue(), R2->getValue()))) {
8407 if (!CB->getZExtValue())
8408 std::swap(R1, R2); // R1 is the minimum root now.
8410 // Make sure the root is not off by one. The returned iteration should
8411 // not be in the range, but the previous one should be. When solving
8412 // for "X*X < 5", for example, we should not return a root of 2.
8413 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
8416 if (Range.contains(R1Val->getValue())) {
8417 // The next iteration must be out of the range...
8418 ConstantInt *NextVal =
8419 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
8421 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
8422 if (!Range.contains(R1Val->getValue()))
8423 return SE.getConstant(NextVal);
8424 return SE.getCouldNotCompute(); // Something strange happened
8427 // If R1 was not in the range, then it is a good return value. Make
8428 // sure that R1-1 WAS in the range though, just in case.
8429 ConstantInt *NextVal =
8430 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
8431 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
8432 if (Range.contains(R1Val->getValue()))
8434 return SE.getCouldNotCompute(); // Something strange happened
8439 return SE.getCouldNotCompute();
8445 FindUndefs() : Found(false) {}
8447 bool follow(const SCEV *S) {
8448 if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
8449 if (isa<UndefValue>(C->getValue()))
8451 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
8452 if (isa<UndefValue>(C->getValue()))
8456 // Keep looking if we haven't found it yet.
8459 bool isDone() const {
8460 // Stop recursion if we have found an undef.
8466 // Return true when S contains at least an undef value.
8468 containsUndefs(const SCEV *S) {
8470 SCEVTraversal<FindUndefs> ST(F);
8477 // Collect all steps of SCEV expressions.
8478 struct SCEVCollectStrides {
8479 ScalarEvolution &SE;
8480 SmallVectorImpl<const SCEV *> &Strides;
8482 SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
8483 : SE(SE), Strides(S) {}
8485 bool follow(const SCEV *S) {
8486 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
8487 Strides.push_back(AR->getStepRecurrence(SE));
8490 bool isDone() const { return false; }
8493 // Collect all SCEVUnknown and SCEVMulExpr expressions.
8494 struct SCEVCollectTerms {
8495 SmallVectorImpl<const SCEV *> &Terms;
8497 SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
8500 bool follow(const SCEV *S) {
8501 if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S)) {
8502 if (!containsUndefs(S))
8505 // Stop recursion: once we collected a term, do not walk its operands.
8512 bool isDone() const { return false; }
8515 // Check if a SCEV contains an AddRecExpr.
8516 struct SCEVHasAddRec {
8517 bool &ContainsAddRec;
8519 SCEVHasAddRec(bool &ContainsAddRec) : ContainsAddRec(ContainsAddRec) {
8520 ContainsAddRec = false;
8523 bool follow(const SCEV *S) {
8524 if (isa<SCEVAddRecExpr>(S)) {
8525 ContainsAddRec = true;
8527 // Stop recursion: once we collected a term, do not walk its operands.
8534 bool isDone() const { return false; }
8537 // Find factors that are multiplied with an expression that (possibly as a
8538 // subexpression) contains an AddRecExpr. In the expression:
8540 // 8 * (100 + %p * %q * (%a + {0, +, 1}_loop))
8542 // "%p * %q" are factors multiplied by the expression "(%a + {0, +, 1}_loop)"
8543 // that contains the AddRec {0, +, 1}_loop. %p * %q are likely to be array size
8544 // parameters as they form a product with an induction variable.
8546 // This collector expects all array size parameters to be in the same MulExpr.
8547 // It might be necessary to later add support for collecting parameters that are
8548 // spread over different nested MulExpr.
8549 struct SCEVCollectAddRecMultiplies {
8550 SmallVectorImpl<const SCEV *> &Terms;
8551 ScalarEvolution &SE;
8553 SCEVCollectAddRecMultiplies(SmallVectorImpl<const SCEV *> &T, ScalarEvolution &SE)
8554 : Terms(T), SE(SE) {}
8556 bool follow(const SCEV *S) {
8557 if (auto *Mul = dyn_cast<SCEVMulExpr>(S)) {
8558 bool HasAddRec = false;
8559 SmallVector<const SCEV *, 0> Operands;
8560 for (auto Op : Mul->operands()) {
8561 if (isa<SCEVUnknown>(Op)) {
8562 Operands.push_back(Op);
8564 bool ContainsAddRec;
8565 SCEVHasAddRec ContiansAddRec(ContainsAddRec);
8566 visitAll(Op, ContiansAddRec);
8567 HasAddRec |= ContainsAddRec;
8570 if (Operands.size() == 0)
8576 Terms.push_back(SE.getMulExpr(Operands));
8577 // Stop recursion: once we collected a term, do not walk its operands.
8584 bool isDone() const { return false; }
8588 /// Find parametric terms in this SCEVAddRecExpr. We first for parameters in
8590 /// 1) The strides of AddRec expressions.
8591 /// 2) Unknowns that are multiplied with AddRec expressions.
8592 void ScalarEvolution::collectParametricTerms(const SCEV *Expr,
8593 SmallVectorImpl<const SCEV *> &Terms) {
8594 SmallVector<const SCEV *, 4> Strides;
8595 SCEVCollectStrides StrideCollector(*this, Strides);
8596 visitAll(Expr, StrideCollector);
8599 dbgs() << "Strides:\n";
8600 for (const SCEV *S : Strides)
8601 dbgs() << *S << "\n";
8604 for (const SCEV *S : Strides) {
8605 SCEVCollectTerms TermCollector(Terms);
8606 visitAll(S, TermCollector);
8610 dbgs() << "Terms:\n";
8611 for (const SCEV *T : Terms)
8612 dbgs() << *T << "\n";
8615 SCEVCollectAddRecMultiplies MulCollector(Terms, *this);
8616 visitAll(Expr, MulCollector);
8619 static bool findArrayDimensionsRec(ScalarEvolution &SE,
8620 SmallVectorImpl<const SCEV *> &Terms,
8621 SmallVectorImpl<const SCEV *> &Sizes) {
8622 int Last = Terms.size() - 1;
8623 const SCEV *Step = Terms[Last];
8625 // End of recursion.
8627 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
8628 SmallVector<const SCEV *, 2> Qs;
8629 for (const SCEV *Op : M->operands())
8630 if (!isa<SCEVConstant>(Op))
8633 Step = SE.getMulExpr(Qs);
8636 Sizes.push_back(Step);
8640 for (const SCEV *&Term : Terms) {
8641 // Normalize the terms before the next call to findArrayDimensionsRec.
8643 SCEVDivision::divide(SE, Term, Step, &Q, &R);
8645 // Bail out when GCD does not evenly divide one of the terms.
8652 // Remove all SCEVConstants.
8653 Terms.erase(std::remove_if(Terms.begin(), Terms.end(), [](const SCEV *E) {
8654 return isa<SCEVConstant>(E);
8658 if (Terms.size() > 0)
8659 if (!findArrayDimensionsRec(SE, Terms, Sizes))
8662 Sizes.push_back(Step);
8667 struct FindParameter {
8668 bool FoundParameter;
8669 FindParameter() : FoundParameter(false) {}
8671 bool follow(const SCEV *S) {
8672 if (isa<SCEVUnknown>(S)) {
8673 FoundParameter = true;
8674 // Stop recursion: we found a parameter.
8680 bool isDone() const {
8681 // Stop recursion if we have found a parameter.
8682 return FoundParameter;
8687 // Returns true when S contains at least a SCEVUnknown parameter.
8689 containsParameters(const SCEV *S) {
8691 SCEVTraversal<FindParameter> ST(F);
8694 return F.FoundParameter;
8697 // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
8699 containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
8700 for (const SCEV *T : Terms)
8701 if (containsParameters(T))
8706 // Return the number of product terms in S.
8707 static inline int numberOfTerms(const SCEV *S) {
8708 if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
8709 return Expr->getNumOperands();
8713 static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
8714 if (isa<SCEVConstant>(T))
8717 if (isa<SCEVUnknown>(T))
8720 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
8721 SmallVector<const SCEV *, 2> Factors;
8722 for (const SCEV *Op : M->operands())
8723 if (!isa<SCEVConstant>(Op))
8724 Factors.push_back(Op);
8726 return SE.getMulExpr(Factors);
8732 /// Return the size of an element read or written by Inst.
8733 const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
8735 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
8736 Ty = Store->getValueOperand()->getType();
8737 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
8738 Ty = Load->getType();
8742 Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
8743 return getSizeOfExpr(ETy, Ty);
8746 /// Second step of delinearization: compute the array dimensions Sizes from the
8747 /// set of Terms extracted from the memory access function of this SCEVAddRec.
8748 void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
8749 SmallVectorImpl<const SCEV *> &Sizes,
8750 const SCEV *ElementSize) const {
8752 if (Terms.size() < 1 || !ElementSize)
8755 // Early return when Terms do not contain parameters: we do not delinearize
8756 // non parametric SCEVs.
8757 if (!containsParameters(Terms))
8761 dbgs() << "Terms:\n";
8762 for (const SCEV *T : Terms)
8763 dbgs() << *T << "\n";
8766 // Remove duplicates.
8767 std::sort(Terms.begin(), Terms.end());
8768 Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
8770 // Put larger terms first.
8771 std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
8772 return numberOfTerms(LHS) > numberOfTerms(RHS);
8775 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
8777 // Try to divide all terms by the element size. If term is not divisible by
8778 // element size, proceed with the original term.
8779 for (const SCEV *&Term : Terms) {
8781 SCEVDivision::divide(SE, Term, ElementSize, &Q, &R);
8786 SmallVector<const SCEV *, 4> NewTerms;
8788 // Remove constant factors.
8789 for (const SCEV *T : Terms)
8790 if (const SCEV *NewT = removeConstantFactors(SE, T))
8791 NewTerms.push_back(NewT);
8794 dbgs() << "Terms after sorting:\n";
8795 for (const SCEV *T : NewTerms)
8796 dbgs() << *T << "\n";
8799 if (NewTerms.empty() ||
8800 !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
8805 // The last element to be pushed into Sizes is the size of an element.
8806 Sizes.push_back(ElementSize);
8809 dbgs() << "Sizes:\n";
8810 for (const SCEV *S : Sizes)
8811 dbgs() << *S << "\n";
8815 /// Third step of delinearization: compute the access functions for the
8816 /// Subscripts based on the dimensions in Sizes.
8817 void ScalarEvolution::computeAccessFunctions(
8818 const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts,
8819 SmallVectorImpl<const SCEV *> &Sizes) {
8821 // Early exit in case this SCEV is not an affine multivariate function.
8825 if (auto *AR = dyn_cast<SCEVAddRecExpr>(Expr))
8826 if (!AR->isAffine())
8829 const SCEV *Res = Expr;
8830 int Last = Sizes.size() - 1;
8831 for (int i = Last; i >= 0; i--) {
8833 SCEVDivision::divide(*this, Res, Sizes[i], &Q, &R);
8836 dbgs() << "Res: " << *Res << "\n";
8837 dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
8838 dbgs() << "Res divided by Sizes[i]:\n";
8839 dbgs() << "Quotient: " << *Q << "\n";
8840 dbgs() << "Remainder: " << *R << "\n";
8845 // Do not record the last subscript corresponding to the size of elements in
8849 // Bail out if the remainder is too complex.
8850 if (isa<SCEVAddRecExpr>(R)) {
8859 // Record the access function for the current subscript.
8860 Subscripts.push_back(R);
8863 // Also push in last position the remainder of the last division: it will be
8864 // the access function of the innermost dimension.
8865 Subscripts.push_back(Res);
8867 std::reverse(Subscripts.begin(), Subscripts.end());
8870 dbgs() << "Subscripts:\n";
8871 for (const SCEV *S : Subscripts)
8872 dbgs() << *S << "\n";
8876 /// Splits the SCEV into two vectors of SCEVs representing the subscripts and
8877 /// sizes of an array access. Returns the remainder of the delinearization that
8878 /// is the offset start of the array. The SCEV->delinearize algorithm computes
8879 /// the multiples of SCEV coefficients: that is a pattern matching of sub
8880 /// expressions in the stride and base of a SCEV corresponding to the
8881 /// computation of a GCD (greatest common divisor) of base and stride. When
8882 /// SCEV->delinearize fails, it returns the SCEV unchanged.
8884 /// For example: when analyzing the memory access A[i][j][k] in this loop nest
8886 /// void foo(long n, long m, long o, double A[n][m][o]) {
8888 /// for (long i = 0; i < n; i++)
8889 /// for (long j = 0; j < m; j++)
8890 /// for (long k = 0; k < o; k++)
8891 /// A[i][j][k] = 1.0;
8894 /// the delinearization input is the following AddRec SCEV:
8896 /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
8898 /// From this SCEV, we are able to say that the base offset of the access is %A
8899 /// because it appears as an offset that does not divide any of the strides in
8902 /// CHECK: Base offset: %A
8904 /// and then SCEV->delinearize determines the size of some of the dimensions of
8905 /// the array as these are the multiples by which the strides are happening:
8907 /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
8909 /// Note that the outermost dimension remains of UnknownSize because there are
8910 /// no strides that would help identifying the size of the last dimension: when
8911 /// the array has been statically allocated, one could compute the size of that
8912 /// dimension by dividing the overall size of the array by the size of the known
8913 /// dimensions: %m * %o * 8.
8915 /// Finally delinearize provides the access functions for the array reference
8916 /// that does correspond to A[i][j][k] of the above C testcase:
8918 /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
8920 /// The testcases are checking the output of a function pass:
8921 /// DelinearizationPass that walks through all loads and stores of a function
8922 /// asking for the SCEV of the memory access with respect to all enclosing
8923 /// loops, calling SCEV->delinearize on that and printing the results.
8925 void ScalarEvolution::delinearize(const SCEV *Expr,
8926 SmallVectorImpl<const SCEV *> &Subscripts,
8927 SmallVectorImpl<const SCEV *> &Sizes,
8928 const SCEV *ElementSize) {
8929 // First step: collect parametric terms.
8930 SmallVector<const SCEV *, 4> Terms;
8931 collectParametricTerms(Expr, Terms);
8936 // Second step: find subscript sizes.
8937 findArrayDimensions(Terms, Sizes, ElementSize);
8942 // Third step: compute the access functions for each subscript.
8943 computeAccessFunctions(Expr, Subscripts, Sizes);
8945 if (Subscripts.empty())
8949 dbgs() << "succeeded to delinearize " << *Expr << "\n";
8950 dbgs() << "ArrayDecl[UnknownSize]";
8951 for (const SCEV *S : Sizes)
8952 dbgs() << "[" << *S << "]";
8954 dbgs() << "\nArrayRef";
8955 for (const SCEV *S : Subscripts)
8956 dbgs() << "[" << *S << "]";
8961 //===----------------------------------------------------------------------===//
8962 // SCEVCallbackVH Class Implementation
8963 //===----------------------------------------------------------------------===//
8965 void ScalarEvolution::SCEVCallbackVH::deleted() {
8966 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
8967 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
8968 SE->ConstantEvolutionLoopExitValue.erase(PN);
8969 SE->ValueExprMap.erase(getValPtr());
8970 // this now dangles!
8973 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
8974 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
8976 // Forget all the expressions associated with users of the old value,
8977 // so that future queries will recompute the expressions using the new
8979 Value *Old = getValPtr();
8980 SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
8981 SmallPtrSet<User *, 8> Visited;
8982 while (!Worklist.empty()) {
8983 User *U = Worklist.pop_back_val();
8984 // Deleting the Old value will cause this to dangle. Postpone
8985 // that until everything else is done.
8988 if (!Visited.insert(U).second)
8990 if (PHINode *PN = dyn_cast<PHINode>(U))
8991 SE->ConstantEvolutionLoopExitValue.erase(PN);
8992 SE->ValueExprMap.erase(U);
8993 Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
8995 // Delete the Old value.
8996 if (PHINode *PN = dyn_cast<PHINode>(Old))
8997 SE->ConstantEvolutionLoopExitValue.erase(PN);
8998 SE->ValueExprMap.erase(Old);
8999 // this now dangles!
9002 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
9003 : CallbackVH(V), SE(se) {}
9005 //===----------------------------------------------------------------------===//
9006 // ScalarEvolution Class Implementation
9007 //===----------------------------------------------------------------------===//
9009 ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI,
9010 AssumptionCache &AC, DominatorTree &DT,
9012 : F(F), TLI(TLI), AC(AC), DT(DT), LI(LI),
9013 CouldNotCompute(new SCEVCouldNotCompute()),
9014 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
9015 ValuesAtScopes(64), LoopDispositions(64), BlockDispositions(64),
9016 FirstUnknown(nullptr) {}
9018 ScalarEvolution::ScalarEvolution(ScalarEvolution &&Arg)
9019 : F(Arg.F), TLI(Arg.TLI), AC(Arg.AC), DT(Arg.DT), LI(Arg.LI),
9020 CouldNotCompute(std::move(Arg.CouldNotCompute)),
9021 ValueExprMap(std::move(Arg.ValueExprMap)),
9022 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
9023 BackedgeTakenCounts(std::move(Arg.BackedgeTakenCounts)),
9024 ConstantEvolutionLoopExitValue(
9025 std::move(Arg.ConstantEvolutionLoopExitValue)),
9026 ValuesAtScopes(std::move(Arg.ValuesAtScopes)),
9027 LoopDispositions(std::move(Arg.LoopDispositions)),
9028 BlockDispositions(std::move(Arg.BlockDispositions)),
9029 UnsignedRanges(std::move(Arg.UnsignedRanges)),
9030 SignedRanges(std::move(Arg.SignedRanges)),
9031 UniqueSCEVs(std::move(Arg.UniqueSCEVs)),
9032 SCEVAllocator(std::move(Arg.SCEVAllocator)),
9033 FirstUnknown(Arg.FirstUnknown) {
9034 Arg.FirstUnknown = nullptr;
9037 ScalarEvolution::~ScalarEvolution() {
9038 // Iterate through all the SCEVUnknown instances and call their
9039 // destructors, so that they release their references to their values.
9040 for (SCEVUnknown *U = FirstUnknown; U;) {
9041 SCEVUnknown *Tmp = U;
9043 Tmp->~SCEVUnknown();
9045 FirstUnknown = nullptr;
9047 ValueExprMap.clear();
9049 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
9050 // that a loop had multiple computable exits.
9051 for (auto &BTCI : BackedgeTakenCounts)
9052 BTCI.second.clear();
9054 assert(PendingLoopPredicates.empty() && "isImpliedCond garbage");
9055 assert(!WalkingBEDominatingConds && "isLoopBackedgeGuardedByCond garbage!");
9056 assert(!ProvingSplitPredicate && "ProvingSplitPredicate garbage!");
9059 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
9060 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
9063 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
9065 // Print all inner loops first
9066 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
9067 PrintLoopInfo(OS, SE, *I);
9070 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9073 SmallVector<BasicBlock *, 8> ExitBlocks;
9074 L->getExitBlocks(ExitBlocks);
9075 if (ExitBlocks.size() != 1)
9076 OS << "<multiple exits> ";
9078 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
9079 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
9081 OS << "Unpredictable backedge-taken count. ";
9086 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
9089 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
9090 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
9092 OS << "Unpredictable max backedge-taken count. ";
9098 void ScalarEvolution::print(raw_ostream &OS) const {
9099 // ScalarEvolution's implementation of the print method is to print
9100 // out SCEV values of all instructions that are interesting. Doing
9101 // this potentially causes it to create new SCEV objects though,
9102 // which technically conflicts with the const qualifier. This isn't
9103 // observable from outside the class though, so casting away the
9104 // const isn't dangerous.
9105 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
9107 OS << "Classifying expressions for: ";
9108 F.printAsOperand(OS, /*PrintType=*/false);
9110 for (Instruction &I : instructions(F))
9111 if (isSCEVable(I.getType()) && !isa<CmpInst>(I)) {
9114 const SCEV *SV = SE.getSCEV(&I);
9116 if (!isa<SCEVCouldNotCompute>(SV)) {
9118 SE.getUnsignedRange(SV).print(OS);
9120 SE.getSignedRange(SV).print(OS);
9123 const Loop *L = LI.getLoopFor(I.getParent());
9125 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
9129 if (!isa<SCEVCouldNotCompute>(AtUse)) {
9131 SE.getUnsignedRange(AtUse).print(OS);
9133 SE.getSignedRange(AtUse).print(OS);
9138 OS << "\t\t" "Exits: ";
9139 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
9140 if (!SE.isLoopInvariant(ExitValue, L)) {
9141 OS << "<<Unknown>>";
9150 OS << "Determining loop execution counts for: ";
9151 F.printAsOperand(OS, /*PrintType=*/false);
9153 for (LoopInfo::iterator I = LI.begin(), E = LI.end(); I != E; ++I)
9154 PrintLoopInfo(OS, &SE, *I);
9157 ScalarEvolution::LoopDisposition
9158 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
9159 auto &Values = LoopDispositions[S];
9160 for (auto &V : Values) {
9161 if (V.getPointer() == L)
9164 Values.emplace_back(L, LoopVariant);
9165 LoopDisposition D = computeLoopDisposition(S, L);
9166 auto &Values2 = LoopDispositions[S];
9167 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
9168 if (V.getPointer() == L) {
9176 ScalarEvolution::LoopDisposition
9177 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
9178 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
9180 return LoopInvariant;
9184 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
9185 case scAddRecExpr: {
9186 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
9188 // If L is the addrec's loop, it's computable.
9189 if (AR->getLoop() == L)
9190 return LoopComputable;
9192 // Add recurrences are never invariant in the function-body (null loop).
9196 // This recurrence is variant w.r.t. L if L contains AR's loop.
9197 if (L->contains(AR->getLoop()))
9200 // This recurrence is invariant w.r.t. L if AR's loop contains L.
9201 if (AR->getLoop()->contains(L))
9202 return LoopInvariant;
9204 // This recurrence is variant w.r.t. L if any of its operands
9206 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
9208 if (!isLoopInvariant(*I, L))
9211 // Otherwise it's loop-invariant.
9212 return LoopInvariant;
9218 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
9219 bool HasVarying = false;
9220 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
9222 LoopDisposition D = getLoopDisposition(*I, L);
9223 if (D == LoopVariant)
9225 if (D == LoopComputable)
9228 return HasVarying ? LoopComputable : LoopInvariant;
9231 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
9232 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
9233 if (LD == LoopVariant)
9235 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
9236 if (RD == LoopVariant)
9238 return (LD == LoopInvariant && RD == LoopInvariant) ?
9239 LoopInvariant : LoopComputable;
9242 // All non-instruction values are loop invariant. All instructions are loop
9243 // invariant if they are not contained in the specified loop.
9244 // Instructions are never considered invariant in the function body
9245 // (null loop) because they are defined within the "loop".
9246 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
9247 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
9248 return LoopInvariant;
9249 case scCouldNotCompute:
9250 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
9252 llvm_unreachable("Unknown SCEV kind!");
9255 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
9256 return getLoopDisposition(S, L) == LoopInvariant;
9259 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
9260 return getLoopDisposition(S, L) == LoopComputable;
9263 ScalarEvolution::BlockDisposition
9264 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
9265 auto &Values = BlockDispositions[S];
9266 for (auto &V : Values) {
9267 if (V.getPointer() == BB)
9270 Values.emplace_back(BB, DoesNotDominateBlock);
9271 BlockDisposition D = computeBlockDisposition(S, BB);
9272 auto &Values2 = BlockDispositions[S];
9273 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
9274 if (V.getPointer() == BB) {
9282 ScalarEvolution::BlockDisposition
9283 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
9284 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
9286 return ProperlyDominatesBlock;
9290 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
9291 case scAddRecExpr: {
9292 // This uses a "dominates" query instead of "properly dominates" query
9293 // to test for proper dominance too, because the instruction which
9294 // produces the addrec's value is a PHI, and a PHI effectively properly
9295 // dominates its entire containing block.
9296 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
9297 if (!DT.dominates(AR->getLoop()->getHeader(), BB))
9298 return DoesNotDominateBlock;
9300 // FALL THROUGH into SCEVNAryExpr handling.
9305 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
9307 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
9309 BlockDisposition D = getBlockDisposition(*I, BB);
9310 if (D == DoesNotDominateBlock)
9311 return DoesNotDominateBlock;
9312 if (D == DominatesBlock)
9315 return Proper ? ProperlyDominatesBlock : DominatesBlock;
9318 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
9319 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
9320 BlockDisposition LD = getBlockDisposition(LHS, BB);
9321 if (LD == DoesNotDominateBlock)
9322 return DoesNotDominateBlock;
9323 BlockDisposition RD = getBlockDisposition(RHS, BB);
9324 if (RD == DoesNotDominateBlock)
9325 return DoesNotDominateBlock;
9326 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
9327 ProperlyDominatesBlock : DominatesBlock;
9330 if (Instruction *I =
9331 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
9332 if (I->getParent() == BB)
9333 return DominatesBlock;
9334 if (DT.properlyDominates(I->getParent(), BB))
9335 return ProperlyDominatesBlock;
9336 return DoesNotDominateBlock;
9338 return ProperlyDominatesBlock;
9339 case scCouldNotCompute:
9340 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
9342 llvm_unreachable("Unknown SCEV kind!");
9345 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
9346 return getBlockDisposition(S, BB) >= DominatesBlock;
9349 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
9350 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
9354 // Search for a SCEV expression node within an expression tree.
9355 // Implements SCEVTraversal::Visitor.
9360 SCEVSearch(const SCEV *N): Node(N), IsFound(false) {}
9362 bool follow(const SCEV *S) {
9363 IsFound |= (S == Node);
9366 bool isDone() const { return IsFound; }
9370 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
9371 SCEVSearch Search(Op);
9372 visitAll(S, Search);
9373 return Search.IsFound;
9376 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
9377 ValuesAtScopes.erase(S);
9378 LoopDispositions.erase(S);
9379 BlockDispositions.erase(S);
9380 UnsignedRanges.erase(S);
9381 SignedRanges.erase(S);
9383 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
9384 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end(); I != E; ) {
9385 BackedgeTakenInfo &BEInfo = I->second;
9386 if (BEInfo.hasOperand(S, this)) {
9388 BackedgeTakenCounts.erase(I++);
9395 typedef DenseMap<const Loop *, std::string> VerifyMap;
9397 /// replaceSubString - Replaces all occurrences of From in Str with To.
9398 static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
9400 while ((Pos = Str.find(From, Pos)) != std::string::npos) {
9401 Str.replace(Pos, From.size(), To.data(), To.size());
9406 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
9408 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
9409 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) {
9410 getLoopBackedgeTakenCounts(*I, Map, SE); // recurse.
9412 std::string &S = Map[L];
9414 raw_string_ostream OS(S);
9415 SE.getBackedgeTakenCount(L)->print(OS);
9417 // false and 0 are semantically equivalent. This can happen in dead loops.
9418 replaceSubString(OS.str(), "false", "0");
9419 // Remove wrap flags, their use in SCEV is highly fragile.
9420 // FIXME: Remove this when SCEV gets smarter about them.
9421 replaceSubString(OS.str(), "<nw>", "");
9422 replaceSubString(OS.str(), "<nsw>", "");
9423 replaceSubString(OS.str(), "<nuw>", "");
9428 void ScalarEvolution::verify() const {
9429 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
9431 // Gather stringified backedge taken counts for all loops using SCEV's caches.
9432 // FIXME: It would be much better to store actual values instead of strings,
9433 // but SCEV pointers will change if we drop the caches.
9434 VerifyMap BackedgeDumpsOld, BackedgeDumpsNew;
9435 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
9436 getLoopBackedgeTakenCounts(*I, BackedgeDumpsOld, SE);
9438 // Gather stringified backedge taken counts for all loops using a fresh
9439 // ScalarEvolution object.
9440 ScalarEvolution SE2(F, TLI, AC, DT, LI);
9441 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
9442 getLoopBackedgeTakenCounts(*I, BackedgeDumpsNew, SE2);
9444 // Now compare whether they're the same with and without caches. This allows
9445 // verifying that no pass changed the cache.
9446 assert(BackedgeDumpsOld.size() == BackedgeDumpsNew.size() &&
9447 "New loops suddenly appeared!");
9449 for (VerifyMap::iterator OldI = BackedgeDumpsOld.begin(),
9450 OldE = BackedgeDumpsOld.end(),
9451 NewI = BackedgeDumpsNew.begin();
9452 OldI != OldE; ++OldI, ++NewI) {
9453 assert(OldI->first == NewI->first && "Loop order changed!");
9455 // Compare the stringified SCEVs. We don't care if undef backedgetaken count
9457 // FIXME: We currently ignore SCEV changes from/to CouldNotCompute. This
9458 // means that a pass is buggy or SCEV has to learn a new pattern but is
9459 // usually not harmful.
9460 if (OldI->second != NewI->second &&
9461 OldI->second.find("undef") == std::string::npos &&
9462 NewI->second.find("undef") == std::string::npos &&
9463 OldI->second != "***COULDNOTCOMPUTE***" &&
9464 NewI->second != "***COULDNOTCOMPUTE***") {
9465 dbgs() << "SCEVValidator: SCEV for loop '"
9466 << OldI->first->getHeader()->getName()
9467 << "' changed from '" << OldI->second
9468 << "' to '" << NewI->second << "'!\n";
9473 // TODO: Verify more things.
9476 char ScalarEvolutionAnalysis::PassID;
9478 ScalarEvolution ScalarEvolutionAnalysis::run(Function &F,
9479 AnalysisManager<Function> *AM) {
9480 return ScalarEvolution(F, AM->getResult<TargetLibraryAnalysis>(F),
9481 AM->getResult<AssumptionAnalysis>(F),
9482 AM->getResult<DominatorTreeAnalysis>(F),
9483 AM->getResult<LoopAnalysis>(F));
9487 ScalarEvolutionPrinterPass::run(Function &F, AnalysisManager<Function> *AM) {
9488 AM->getResult<ScalarEvolutionAnalysis>(F).print(OS);
9489 return PreservedAnalyses::all();
9492 INITIALIZE_PASS_BEGIN(ScalarEvolutionWrapperPass, "scalar-evolution",
9493 "Scalar Evolution Analysis", false, true)
9494 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
9495 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
9496 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
9497 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
9498 INITIALIZE_PASS_END(ScalarEvolutionWrapperPass, "scalar-evolution",
9499 "Scalar Evolution Analysis", false, true)
9500 char ScalarEvolutionWrapperPass::ID = 0;
9502 ScalarEvolutionWrapperPass::ScalarEvolutionWrapperPass() : FunctionPass(ID) {
9503 initializeScalarEvolutionWrapperPassPass(*PassRegistry::getPassRegistry());
9506 bool ScalarEvolutionWrapperPass::runOnFunction(Function &F) {
9507 SE.reset(new ScalarEvolution(
9508 F, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
9509 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
9510 getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
9511 getAnalysis<LoopInfoWrapperPass>().getLoopInfo()));
9515 void ScalarEvolutionWrapperPass::releaseMemory() { SE.reset(); }
9517 void ScalarEvolutionWrapperPass::print(raw_ostream &OS, const Module *) const {
9521 void ScalarEvolutionWrapperPass::verifyAnalysis() const {
9528 void ScalarEvolutionWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
9529 AU.setPreservesAll();
9530 AU.addRequiredTransitive<AssumptionCacheTracker>();
9531 AU.addRequiredTransitive<LoopInfoWrapperPass>();
9532 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
9533 AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();