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/Support/CommandLine.h"
87 #include "llvm/Support/Debug.h"
88 #include "llvm/Support/ErrorHandling.h"
89 #include "llvm/Support/MathExtras.h"
90 #include "llvm/Support/raw_ostream.h"
91 #include "llvm/Support/SaveAndRestore.h"
95 #define DEBUG_TYPE "scalar-evolution"
97 STATISTIC(NumArrayLenItCounts,
98 "Number of trip counts computed with array length");
99 STATISTIC(NumTripCountsComputed,
100 "Number of loops with predictable loop counts");
101 STATISTIC(NumTripCountsNotComputed,
102 "Number of loops without predictable loop counts");
103 STATISTIC(NumBruteForceTripCountsComputed,
104 "Number of loops with trip counts computed by force");
106 static cl::opt<unsigned>
107 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
108 cl::desc("Maximum number of iterations SCEV will "
109 "symbolically execute a constant "
113 // FIXME: Enable this with XDEBUG when the test suite is clean.
115 VerifySCEV("verify-scev",
116 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
118 //===----------------------------------------------------------------------===//
119 // SCEV class definitions
120 //===----------------------------------------------------------------------===//
122 //===----------------------------------------------------------------------===//
123 // Implementation of the SCEV class.
126 void SCEV::print(raw_ostream &OS) const {
127 switch (static_cast<SCEVTypes>(getSCEVType())) {
129 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
132 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
133 const SCEV *Op = Trunc->getOperand();
134 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
135 << *Trunc->getType() << ")";
139 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
140 const SCEV *Op = ZExt->getOperand();
141 OS << "(zext " << *Op->getType() << " " << *Op << " to "
142 << *ZExt->getType() << ")";
146 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
147 const SCEV *Op = SExt->getOperand();
148 OS << "(sext " << *Op->getType() << " " << *Op << " to "
149 << *SExt->getType() << ")";
153 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
154 OS << "{" << *AR->getOperand(0);
155 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
156 OS << ",+," << *AR->getOperand(i);
158 if (AR->getNoWrapFlags(FlagNUW))
160 if (AR->getNoWrapFlags(FlagNSW))
162 if (AR->getNoWrapFlags(FlagNW) &&
163 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
165 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
173 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
174 const char *OpStr = nullptr;
175 switch (NAry->getSCEVType()) {
176 case scAddExpr: OpStr = " + "; break;
177 case scMulExpr: OpStr = " * "; break;
178 case scUMaxExpr: OpStr = " umax "; break;
179 case scSMaxExpr: OpStr = " smax "; break;
182 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
185 if (std::next(I) != E)
189 switch (NAry->getSCEVType()) {
192 if (NAry->getNoWrapFlags(FlagNUW))
194 if (NAry->getNoWrapFlags(FlagNSW))
200 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
201 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
205 const SCEVUnknown *U = cast<SCEVUnknown>(this);
207 if (U->isSizeOf(AllocTy)) {
208 OS << "sizeof(" << *AllocTy << ")";
211 if (U->isAlignOf(AllocTy)) {
212 OS << "alignof(" << *AllocTy << ")";
218 if (U->isOffsetOf(CTy, FieldNo)) {
219 OS << "offsetof(" << *CTy << ", ";
220 FieldNo->printAsOperand(OS, false);
225 // Otherwise just print it normally.
226 U->getValue()->printAsOperand(OS, false);
229 case scCouldNotCompute:
230 OS << "***COULDNOTCOMPUTE***";
233 llvm_unreachable("Unknown SCEV kind!");
236 Type *SCEV::getType() const {
237 switch (static_cast<SCEVTypes>(getSCEVType())) {
239 return cast<SCEVConstant>(this)->getType();
243 return cast<SCEVCastExpr>(this)->getType();
248 return cast<SCEVNAryExpr>(this)->getType();
250 return cast<SCEVAddExpr>(this)->getType();
252 return cast<SCEVUDivExpr>(this)->getType();
254 return cast<SCEVUnknown>(this)->getType();
255 case scCouldNotCompute:
256 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
258 llvm_unreachable("Unknown SCEV kind!");
261 bool SCEV::isZero() const {
262 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
263 return SC->getValue()->isZero();
267 bool SCEV::isOne() const {
268 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
269 return SC->getValue()->isOne();
273 bool SCEV::isAllOnesValue() const {
274 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
275 return SC->getValue()->isAllOnesValue();
279 /// isNonConstantNegative - Return true if the specified scev is negated, but
281 bool SCEV::isNonConstantNegative() const {
282 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
283 if (!Mul) return false;
285 // If there is a constant factor, it will be first.
286 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
287 if (!SC) return false;
289 // Return true if the value is negative, this matches things like (-42 * V).
290 return SC->getValue()->getValue().isNegative();
293 SCEVCouldNotCompute::SCEVCouldNotCompute() :
294 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
296 bool SCEVCouldNotCompute::classof(const SCEV *S) {
297 return S->getSCEVType() == scCouldNotCompute;
300 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
302 ID.AddInteger(scConstant);
305 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
306 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
307 UniqueSCEVs.InsertNode(S, IP);
311 const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
312 return getConstant(ConstantInt::get(getContext(), Val));
316 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
317 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
318 return getConstant(ConstantInt::get(ITy, V, isSigned));
321 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
322 unsigned SCEVTy, const SCEV *op, Type *ty)
323 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
325 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
326 const SCEV *op, Type *ty)
327 : SCEVCastExpr(ID, scTruncate, op, ty) {
328 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
329 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
330 "Cannot truncate non-integer value!");
333 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
334 const SCEV *op, Type *ty)
335 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
336 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
337 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
338 "Cannot zero extend non-integer value!");
341 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
342 const SCEV *op, Type *ty)
343 : SCEVCastExpr(ID, scSignExtend, op, ty) {
344 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
345 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
346 "Cannot sign extend non-integer value!");
349 void SCEVUnknown::deleted() {
350 // Clear this SCEVUnknown from various maps.
351 SE->forgetMemoizedResults(this);
353 // Remove this SCEVUnknown from the uniquing map.
354 SE->UniqueSCEVs.RemoveNode(this);
356 // Release the value.
360 void SCEVUnknown::allUsesReplacedWith(Value *New) {
361 // Clear this SCEVUnknown from various maps.
362 SE->forgetMemoizedResults(this);
364 // Remove this SCEVUnknown from the uniquing map.
365 SE->UniqueSCEVs.RemoveNode(this);
367 // Update this SCEVUnknown to point to the new value. This is needed
368 // because there may still be outstanding SCEVs which still point to
373 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
374 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
375 if (VCE->getOpcode() == Instruction::PtrToInt)
376 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
377 if (CE->getOpcode() == Instruction::GetElementPtr &&
378 CE->getOperand(0)->isNullValue() &&
379 CE->getNumOperands() == 2)
380 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
382 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
390 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
391 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
392 if (VCE->getOpcode() == Instruction::PtrToInt)
393 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
394 if (CE->getOpcode() == Instruction::GetElementPtr &&
395 CE->getOperand(0)->isNullValue()) {
397 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
398 if (StructType *STy = dyn_cast<StructType>(Ty))
399 if (!STy->isPacked() &&
400 CE->getNumOperands() == 3 &&
401 CE->getOperand(1)->isNullValue()) {
402 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
404 STy->getNumElements() == 2 &&
405 STy->getElementType(0)->isIntegerTy(1)) {
406 AllocTy = STy->getElementType(1);
415 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
416 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
417 if (VCE->getOpcode() == Instruction::PtrToInt)
418 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
419 if (CE->getOpcode() == Instruction::GetElementPtr &&
420 CE->getNumOperands() == 3 &&
421 CE->getOperand(0)->isNullValue() &&
422 CE->getOperand(1)->isNullValue()) {
424 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
425 // Ignore vector types here so that ScalarEvolutionExpander doesn't
426 // emit getelementptrs that index into vectors.
427 if (Ty->isStructTy() || Ty->isArrayTy()) {
429 FieldNo = CE->getOperand(2);
437 //===----------------------------------------------------------------------===//
439 //===----------------------------------------------------------------------===//
442 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
443 /// than the complexity of the RHS. This comparator is used to canonicalize
445 class SCEVComplexityCompare {
446 const LoopInfo *const LI;
448 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
450 // Return true or false if LHS is less than, or at least RHS, respectively.
451 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
452 return compare(LHS, RHS) < 0;
455 // Return negative, zero, or positive, if LHS is less than, equal to, or
456 // greater than RHS, respectively. A three-way result allows recursive
457 // comparisons to be more efficient.
458 int compare(const SCEV *LHS, const SCEV *RHS) const {
459 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
463 // Primarily, sort the SCEVs by their getSCEVType().
464 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
466 return (int)LType - (int)RType;
468 // Aside from the getSCEVType() ordering, the particular ordering
469 // isn't very important except that it's beneficial to be consistent,
470 // so that (a + b) and (b + a) don't end up as different expressions.
471 switch (static_cast<SCEVTypes>(LType)) {
473 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
474 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
476 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
477 // not as complete as it could be.
478 const Value *LV = LU->getValue(), *RV = RU->getValue();
480 // Order pointer values after integer values. This helps SCEVExpander
482 bool LIsPointer = LV->getType()->isPointerTy(),
483 RIsPointer = RV->getType()->isPointerTy();
484 if (LIsPointer != RIsPointer)
485 return (int)LIsPointer - (int)RIsPointer;
487 // Compare getValueID values.
488 unsigned LID = LV->getValueID(),
489 RID = RV->getValueID();
491 return (int)LID - (int)RID;
493 // Sort arguments by their position.
494 if (const Argument *LA = dyn_cast<Argument>(LV)) {
495 const Argument *RA = cast<Argument>(RV);
496 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
497 return (int)LArgNo - (int)RArgNo;
500 // For instructions, compare their loop depth, and their operand
501 // count. This is pretty loose.
502 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
503 const Instruction *RInst = cast<Instruction>(RV);
505 // Compare loop depths.
506 const BasicBlock *LParent = LInst->getParent(),
507 *RParent = RInst->getParent();
508 if (LParent != RParent) {
509 unsigned LDepth = LI->getLoopDepth(LParent),
510 RDepth = LI->getLoopDepth(RParent);
511 if (LDepth != RDepth)
512 return (int)LDepth - (int)RDepth;
515 // Compare the number of operands.
516 unsigned LNumOps = LInst->getNumOperands(),
517 RNumOps = RInst->getNumOperands();
518 return (int)LNumOps - (int)RNumOps;
525 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
526 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
528 // Compare constant values.
529 const APInt &LA = LC->getValue()->getValue();
530 const APInt &RA = RC->getValue()->getValue();
531 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
532 if (LBitWidth != RBitWidth)
533 return (int)LBitWidth - (int)RBitWidth;
534 return LA.ult(RA) ? -1 : 1;
538 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
539 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
541 // Compare addrec loop depths.
542 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
543 if (LLoop != RLoop) {
544 unsigned LDepth = LLoop->getLoopDepth(),
545 RDepth = RLoop->getLoopDepth();
546 if (LDepth != RDepth)
547 return (int)LDepth - (int)RDepth;
550 // Addrec complexity grows with operand count.
551 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
552 if (LNumOps != RNumOps)
553 return (int)LNumOps - (int)RNumOps;
555 // Lexicographically compare.
556 for (unsigned i = 0; i != LNumOps; ++i) {
557 long X = compare(LA->getOperand(i), RA->getOperand(i));
569 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
570 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
572 // Lexicographically compare n-ary expressions.
573 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
574 if (LNumOps != RNumOps)
575 return (int)LNumOps - (int)RNumOps;
577 for (unsigned i = 0; i != LNumOps; ++i) {
580 long X = compare(LC->getOperand(i), RC->getOperand(i));
584 return (int)LNumOps - (int)RNumOps;
588 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
589 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
591 // Lexicographically compare udiv expressions.
592 long X = compare(LC->getLHS(), RC->getLHS());
595 return compare(LC->getRHS(), RC->getRHS());
601 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
602 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
604 // Compare cast expressions by operand.
605 return compare(LC->getOperand(), RC->getOperand());
608 case scCouldNotCompute:
609 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
611 llvm_unreachable("Unknown SCEV kind!");
616 /// GroupByComplexity - Given a list of SCEV objects, order them by their
617 /// complexity, and group objects of the same complexity together by value.
618 /// When this routine is finished, we know that any duplicates in the vector are
619 /// consecutive and that complexity is monotonically increasing.
621 /// Note that we go take special precautions to ensure that we get deterministic
622 /// results from this routine. In other words, we don't want the results of
623 /// this to depend on where the addresses of various SCEV objects happened to
626 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
628 if (Ops.size() < 2) return; // Noop
629 if (Ops.size() == 2) {
630 // This is the common case, which also happens to be trivially simple.
632 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
633 if (SCEVComplexityCompare(LI)(RHS, LHS))
638 // Do the rough sort by complexity.
639 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
641 // Now that we are sorted by complexity, group elements of the same
642 // complexity. Note that this is, at worst, N^2, but the vector is likely to
643 // be extremely short in practice. Note that we take this approach because we
644 // do not want to depend on the addresses of the objects we are grouping.
645 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
646 const SCEV *S = Ops[i];
647 unsigned Complexity = S->getSCEVType();
649 // If there are any objects of the same complexity and same value as this
651 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
652 if (Ops[j] == S) { // Found a duplicate.
653 // Move it to immediately after i'th element.
654 std::swap(Ops[i+1], Ops[j]);
655 ++i; // no need to rescan it.
656 if (i == e-2) return; // Done!
663 struct FindSCEVSize {
665 FindSCEVSize() : Size(0) {}
667 bool follow(const SCEV *S) {
669 // Keep looking at all operands of S.
672 bool isDone() const {
678 // Returns the size of the SCEV S.
679 static inline int sizeOfSCEV(const SCEV *S) {
681 SCEVTraversal<FindSCEVSize> ST(F);
688 struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
690 // Computes the Quotient and Remainder of the division of Numerator by
692 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
693 const SCEV *Denominator, const SCEV **Quotient,
694 const SCEV **Remainder) {
695 assert(Numerator && Denominator && "Uninitialized SCEV");
697 SCEVDivision D(SE, Numerator, Denominator);
699 // Check for the trivial case here to avoid having to check for it in the
701 if (Numerator == Denominator) {
707 if (Numerator->isZero()) {
713 // A simple case when N/1. The quotient is N.
714 if (Denominator->isOne()) {
715 *Quotient = Numerator;
720 // Split the Denominator when it is a product.
721 if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
723 *Quotient = Numerator;
724 for (const SCEV *Op : T->operands()) {
725 divide(SE, *Quotient, Op, &Q, &R);
728 // Bail out when the Numerator is not divisible by one of the terms of
732 *Remainder = Numerator;
741 *Quotient = D.Quotient;
742 *Remainder = D.Remainder;
745 // Except in the trivial case described above, we do not know how to divide
746 // Expr by Denominator for the following functions with empty implementation.
747 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
748 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
749 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
750 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
751 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
752 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
753 void visitUnknown(const SCEVUnknown *Numerator) {}
754 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
756 void visitConstant(const SCEVConstant *Numerator) {
757 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
758 APInt NumeratorVal = Numerator->getValue()->getValue();
759 APInt DenominatorVal = D->getValue()->getValue();
760 uint32_t NumeratorBW = NumeratorVal.getBitWidth();
761 uint32_t DenominatorBW = DenominatorVal.getBitWidth();
763 if (NumeratorBW > DenominatorBW)
764 DenominatorVal = DenominatorVal.sext(NumeratorBW);
765 else if (NumeratorBW < DenominatorBW)
766 NumeratorVal = NumeratorVal.sext(DenominatorBW);
768 APInt QuotientVal(NumeratorVal.getBitWidth(), 0);
769 APInt RemainderVal(NumeratorVal.getBitWidth(), 0);
770 APInt::sdivrem(NumeratorVal, DenominatorVal, QuotientVal, RemainderVal);
771 Quotient = SE.getConstant(QuotientVal);
772 Remainder = SE.getConstant(RemainderVal);
777 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
778 const SCEV *StartQ, *StartR, *StepQ, *StepR;
779 if (!Numerator->isAffine())
780 return cannotDivide(Numerator);
781 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
782 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
783 // Bail out if the types do not match.
784 Type *Ty = Denominator->getType();
785 if (Ty != StartQ->getType() || Ty != StartR->getType() ||
786 Ty != StepQ->getType() || Ty != StepR->getType())
787 return cannotDivide(Numerator);
788 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
789 Numerator->getNoWrapFlags());
790 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
791 Numerator->getNoWrapFlags());
794 void visitAddExpr(const SCEVAddExpr *Numerator) {
795 SmallVector<const SCEV *, 2> Qs, Rs;
796 Type *Ty = Denominator->getType();
798 for (const SCEV *Op : Numerator->operands()) {
800 divide(SE, Op, Denominator, &Q, &R);
802 // Bail out if types do not match.
803 if (Ty != Q->getType() || Ty != R->getType())
804 return cannotDivide(Numerator);
810 if (Qs.size() == 1) {
816 Quotient = SE.getAddExpr(Qs);
817 Remainder = SE.getAddExpr(Rs);
820 void visitMulExpr(const SCEVMulExpr *Numerator) {
821 SmallVector<const SCEV *, 2> Qs;
822 Type *Ty = Denominator->getType();
824 bool FoundDenominatorTerm = false;
825 for (const SCEV *Op : Numerator->operands()) {
826 // Bail out if types do not match.
827 if (Ty != Op->getType())
828 return cannotDivide(Numerator);
830 if (FoundDenominatorTerm) {
835 // Check whether Denominator divides one of the product operands.
837 divide(SE, Op, Denominator, &Q, &R);
843 // Bail out if types do not match.
844 if (Ty != Q->getType())
845 return cannotDivide(Numerator);
847 FoundDenominatorTerm = true;
851 if (FoundDenominatorTerm) {
856 Quotient = SE.getMulExpr(Qs);
860 if (!isa<SCEVUnknown>(Denominator))
861 return cannotDivide(Numerator);
863 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
864 ValueToValueMap RewriteMap;
865 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
866 cast<SCEVConstant>(Zero)->getValue();
867 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
869 if (Remainder->isZero()) {
870 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
871 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
872 cast<SCEVConstant>(One)->getValue();
874 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
878 // Quotient is (Numerator - Remainder) divided by Denominator.
880 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
881 // This SCEV does not seem to simplify: fail the division here.
882 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator))
883 return cannotDivide(Numerator);
884 divide(SE, Diff, Denominator, &Q, &R);
886 return cannotDivide(Numerator);
891 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator,
892 const SCEV *Denominator)
893 : SE(S), Denominator(Denominator) {
894 Zero = SE.getZero(Denominator->getType());
895 One = SE.getOne(Denominator->getType());
897 // We generally do not know how to divide Expr by Denominator. We
898 // initialize the division to a "cannot divide" state to simplify the rest
900 cannotDivide(Numerator);
903 // Convenience function for giving up on the division. We set the quotient to
904 // be equal to zero and the remainder to be equal to the numerator.
905 void cannotDivide(const SCEV *Numerator) {
907 Remainder = Numerator;
911 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
916 //===----------------------------------------------------------------------===//
917 // Simple SCEV method implementations
918 //===----------------------------------------------------------------------===//
920 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
922 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
925 // Handle the simplest case efficiently.
927 return SE.getTruncateOrZeroExtend(It, ResultTy);
929 // We are using the following formula for BC(It, K):
931 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
933 // Suppose, W is the bitwidth of the return value. We must be prepared for
934 // overflow. Hence, we must assure that the result of our computation is
935 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
936 // safe in modular arithmetic.
938 // However, this code doesn't use exactly that formula; the formula it uses
939 // is something like the following, where T is the number of factors of 2 in
940 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
943 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
945 // This formula is trivially equivalent to the previous formula. However,
946 // this formula can be implemented much more efficiently. The trick is that
947 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
948 // arithmetic. To do exact division in modular arithmetic, all we have
949 // to do is multiply by the inverse. Therefore, this step can be done at
952 // The next issue is how to safely do the division by 2^T. The way this
953 // is done is by doing the multiplication step at a width of at least W + T
954 // bits. This way, the bottom W+T bits of the product are accurate. Then,
955 // when we perform the division by 2^T (which is equivalent to a right shift
956 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
957 // truncated out after the division by 2^T.
959 // In comparison to just directly using the first formula, this technique
960 // is much more efficient; using the first formula requires W * K bits,
961 // but this formula less than W + K bits. Also, the first formula requires
962 // a division step, whereas this formula only requires multiplies and shifts.
964 // It doesn't matter whether the subtraction step is done in the calculation
965 // width or the input iteration count's width; if the subtraction overflows,
966 // the result must be zero anyway. We prefer here to do it in the width of
967 // the induction variable because it helps a lot for certain cases; CodeGen
968 // isn't smart enough to ignore the overflow, which leads to much less
969 // efficient code if the width of the subtraction is wider than the native
972 // (It's possible to not widen at all by pulling out factors of 2 before
973 // the multiplication; for example, K=2 can be calculated as
974 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
975 // extra arithmetic, so it's not an obvious win, and it gets
976 // much more complicated for K > 3.)
978 // Protection from insane SCEVs; this bound is conservative,
979 // but it probably doesn't matter.
981 return SE.getCouldNotCompute();
983 unsigned W = SE.getTypeSizeInBits(ResultTy);
985 // Calculate K! / 2^T and T; we divide out the factors of two before
986 // multiplying for calculating K! / 2^T to avoid overflow.
987 // Other overflow doesn't matter because we only care about the bottom
988 // W bits of the result.
989 APInt OddFactorial(W, 1);
991 for (unsigned i = 3; i <= K; ++i) {
993 unsigned TwoFactors = Mult.countTrailingZeros();
995 Mult = Mult.lshr(TwoFactors);
996 OddFactorial *= Mult;
999 // We need at least W + T bits for the multiplication step
1000 unsigned CalculationBits = W + T;
1002 // Calculate 2^T, at width T+W.
1003 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1005 // Calculate the multiplicative inverse of K! / 2^T;
1006 // this multiplication factor will perform the exact division by
1008 APInt Mod = APInt::getSignedMinValue(W+1);
1009 APInt MultiplyFactor = OddFactorial.zext(W+1);
1010 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1011 MultiplyFactor = MultiplyFactor.trunc(W);
1013 // Calculate the product, at width T+W
1014 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1016 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1017 for (unsigned i = 1; i != K; ++i) {
1018 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1019 Dividend = SE.getMulExpr(Dividend,
1020 SE.getTruncateOrZeroExtend(S, CalculationTy));
1024 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1026 // Truncate the result, and divide by K! / 2^T.
1028 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1029 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1032 /// evaluateAtIteration - Return the value of this chain of recurrences at
1033 /// the specified iteration number. We can evaluate this recurrence by
1034 /// multiplying each element in the chain by the binomial coefficient
1035 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
1037 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1039 /// where BC(It, k) stands for binomial coefficient.
1041 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1042 ScalarEvolution &SE) const {
1043 const SCEV *Result = getStart();
1044 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1045 // The computation is correct in the face of overflow provided that the
1046 // multiplication is performed _after_ the evaluation of the binomial
1048 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1049 if (isa<SCEVCouldNotCompute>(Coeff))
1052 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1057 //===----------------------------------------------------------------------===//
1058 // SCEV Expression folder implementations
1059 //===----------------------------------------------------------------------===//
1061 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1063 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
1064 "This is not a truncating conversion!");
1065 assert(isSCEVable(Ty) &&
1066 "This is not a conversion to a SCEVable type!");
1067 Ty = getEffectiveSCEVType(Ty);
1069 FoldingSetNodeID ID;
1070 ID.AddInteger(scTruncate);
1074 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1076 // Fold if the operand is constant.
1077 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1079 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1081 // trunc(trunc(x)) --> trunc(x)
1082 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1083 return getTruncateExpr(ST->getOperand(), Ty);
1085 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1086 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1087 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1089 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1090 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1091 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1093 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1094 // eliminate all the truncates, or we replace other casts with truncates.
1095 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1096 SmallVector<const SCEV *, 4> Operands;
1097 bool hasTrunc = false;
1098 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1099 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1100 if (!isa<SCEVCastExpr>(SA->getOperand(i)))
1101 hasTrunc = isa<SCEVTruncateExpr>(S);
1102 Operands.push_back(S);
1105 return getAddExpr(Operands);
1106 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1109 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1110 // eliminate all the truncates, or we replace other casts with truncates.
1111 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1112 SmallVector<const SCEV *, 4> Operands;
1113 bool hasTrunc = false;
1114 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1115 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1116 if (!isa<SCEVCastExpr>(SM->getOperand(i)))
1117 hasTrunc = isa<SCEVTruncateExpr>(S);
1118 Operands.push_back(S);
1121 return getMulExpr(Operands);
1122 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1125 // If the input value is a chrec scev, truncate the chrec's operands.
1126 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1127 SmallVector<const SCEV *, 4> Operands;
1128 for (const SCEV *Op : AddRec->operands())
1129 Operands.push_back(getTruncateExpr(Op, Ty));
1130 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1133 // The cast wasn't folded; create an explicit cast node. We can reuse
1134 // the existing insert position since if we get here, we won't have
1135 // made any changes which would invalidate it.
1136 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1138 UniqueSCEVs.InsertNode(S, IP);
1142 // Get the limit of a recurrence such that incrementing by Step cannot cause
1143 // signed overflow as long as the value of the recurrence within the
1144 // loop does not exceed this limit before incrementing.
1145 static const SCEV *getSignedOverflowLimitForStep(const SCEV *Step,
1146 ICmpInst::Predicate *Pred,
1147 ScalarEvolution *SE) {
1148 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1149 if (SE->isKnownPositive(Step)) {
1150 *Pred = ICmpInst::ICMP_SLT;
1151 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1152 SE->getSignedRange(Step).getSignedMax());
1154 if (SE->isKnownNegative(Step)) {
1155 *Pred = ICmpInst::ICMP_SGT;
1156 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1157 SE->getSignedRange(Step).getSignedMin());
1162 // Get the limit of a recurrence such that incrementing by Step cannot cause
1163 // unsigned overflow as long as the value of the recurrence within the loop does
1164 // not exceed this limit before incrementing.
1165 static const SCEV *getUnsignedOverflowLimitForStep(const SCEV *Step,
1166 ICmpInst::Predicate *Pred,
1167 ScalarEvolution *SE) {
1168 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1169 *Pred = ICmpInst::ICMP_ULT;
1171 return SE->getConstant(APInt::getMinValue(BitWidth) -
1172 SE->getUnsignedRange(Step).getUnsignedMax());
1177 struct ExtendOpTraitsBase {
1178 typedef const SCEV *(ScalarEvolution::*GetExtendExprTy)(const SCEV *, Type *);
1181 // Used to make code generic over signed and unsigned overflow.
1182 template <typename ExtendOp> struct ExtendOpTraits {
1185 // static const SCEV::NoWrapFlags WrapType;
1187 // static const ExtendOpTraitsBase::GetExtendExprTy GetExtendExpr;
1189 // static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1190 // ICmpInst::Predicate *Pred,
1191 // ScalarEvolution *SE);
1195 struct ExtendOpTraits<SCEVSignExtendExpr> : public ExtendOpTraitsBase {
1196 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNSW;
1198 static const GetExtendExprTy GetExtendExpr;
1200 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1201 ICmpInst::Predicate *Pred,
1202 ScalarEvolution *SE) {
1203 return getSignedOverflowLimitForStep(Step, Pred, SE);
1207 const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1208 SCEVSignExtendExpr>::GetExtendExpr = &ScalarEvolution::getSignExtendExpr;
1211 struct ExtendOpTraits<SCEVZeroExtendExpr> : public ExtendOpTraitsBase {
1212 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNUW;
1214 static const GetExtendExprTy GetExtendExpr;
1216 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1217 ICmpInst::Predicate *Pred,
1218 ScalarEvolution *SE) {
1219 return getUnsignedOverflowLimitForStep(Step, Pred, SE);
1223 const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1224 SCEVZeroExtendExpr>::GetExtendExpr = &ScalarEvolution::getZeroExtendExpr;
1227 // The recurrence AR has been shown to have no signed/unsigned wrap or something
1228 // close to it. Typically, if we can prove NSW/NUW for AR, then we can just as
1229 // easily prove NSW/NUW for its preincrement or postincrement sibling. This
1230 // allows normalizing a sign/zero extended AddRec as such: {sext/zext(Step +
1231 // Start),+,Step} => {(Step + sext/zext(Start),+,Step} As a result, the
1232 // expression "Step + sext/zext(PreIncAR)" is congruent with
1233 // "sext/zext(PostIncAR)"
1234 template <typename ExtendOpTy>
1235 static const SCEV *getPreStartForExtend(const SCEVAddRecExpr *AR, Type *Ty,
1236 ScalarEvolution *SE) {
1237 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1238 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1240 const Loop *L = AR->getLoop();
1241 const SCEV *Start = AR->getStart();
1242 const SCEV *Step = AR->getStepRecurrence(*SE);
1244 // Check for a simple looking step prior to loop entry.
1245 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1249 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1250 // subtraction is expensive. For this purpose, perform a quick and dirty
1251 // difference, by checking for Step in the operand list.
1252 SmallVector<const SCEV *, 4> DiffOps;
1253 for (const SCEV *Op : SA->operands())
1255 DiffOps.push_back(Op);
1257 if (DiffOps.size() == SA->getNumOperands())
1260 // Try to prove `WrapType` (SCEV::FlagNSW or SCEV::FlagNUW) on `PreStart` +
1263 // 1. NSW/NUW flags on the step increment.
1264 auto PreStartFlags =
1265 ScalarEvolution::maskFlags(SA->getNoWrapFlags(), SCEV::FlagNUW);
1266 const SCEV *PreStart = SE->getAddExpr(DiffOps, PreStartFlags);
1267 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1268 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1270 // "{S,+,X} is <nsw>/<nuw>" and "the backedge is taken at least once" implies
1271 // "S+X does not sign/unsign-overflow".
1274 const SCEV *BECount = SE->getBackedgeTakenCount(L);
1275 if (PreAR && PreAR->getNoWrapFlags(WrapType) &&
1276 !isa<SCEVCouldNotCompute>(BECount) && SE->isKnownPositive(BECount))
1279 // 2. Direct overflow check on the step operation's expression.
1280 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1281 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1282 const SCEV *OperandExtendedStart =
1283 SE->getAddExpr((SE->*GetExtendExpr)(PreStart, WideTy),
1284 (SE->*GetExtendExpr)(Step, WideTy));
1285 if ((SE->*GetExtendExpr)(Start, WideTy) == OperandExtendedStart) {
1286 if (PreAR && AR->getNoWrapFlags(WrapType)) {
1287 // If we know `AR` == {`PreStart`+`Step`,+,`Step`} is `WrapType` (FlagNSW
1288 // or FlagNUW) and that `PreStart` + `Step` is `WrapType` too, then
1289 // `PreAR` == {`PreStart`,+,`Step`} is also `WrapType`. Cache this fact.
1290 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(WrapType);
1295 // 3. Loop precondition.
1296 ICmpInst::Predicate Pred;
1297 const SCEV *OverflowLimit =
1298 ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(Step, &Pred, SE);
1300 if (OverflowLimit &&
1301 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit))
1307 // Get the normalized zero or sign extended expression for this AddRec's Start.
1308 template <typename ExtendOpTy>
1309 static const SCEV *getExtendAddRecStart(const SCEVAddRecExpr *AR, Type *Ty,
1310 ScalarEvolution *SE) {
1311 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1313 const SCEV *PreStart = getPreStartForExtend<ExtendOpTy>(AR, Ty, SE);
1315 return (SE->*GetExtendExpr)(AR->getStart(), Ty);
1317 return SE->getAddExpr((SE->*GetExtendExpr)(AR->getStepRecurrence(*SE), Ty),
1318 (SE->*GetExtendExpr)(PreStart, Ty));
1321 // Try to prove away overflow by looking at "nearby" add recurrences. A
1322 // motivating example for this rule: if we know `{0,+,4}` is `ult` `-1` and it
1323 // does not itself wrap then we can conclude that `{1,+,4}` is `nuw`.
1327 // {S,+,X} == {S-T,+,X} + T
1328 // => Ext({S,+,X}) == Ext({S-T,+,X} + T)
1330 // If ({S-T,+,X} + T) does not overflow ... (1)
1332 // RHS == Ext({S-T,+,X} + T) == Ext({S-T,+,X}) + Ext(T)
1334 // If {S-T,+,X} does not overflow ... (2)
1336 // RHS == Ext({S-T,+,X}) + Ext(T) == {Ext(S-T),+,Ext(X)} + Ext(T)
1337 // == {Ext(S-T)+Ext(T),+,Ext(X)}
1339 // If (S-T)+T does not overflow ... (3)
1341 // RHS == {Ext(S-T)+Ext(T),+,Ext(X)} == {Ext(S-T+T),+,Ext(X)}
1342 // == {Ext(S),+,Ext(X)} == LHS
1344 // Thus, if (1), (2) and (3) are true for some T, then
1345 // Ext({S,+,X}) == {Ext(S),+,Ext(X)}
1347 // (3) is implied by (1) -- "(S-T)+T does not overflow" is simply "({S-T,+,X}+T)
1348 // does not overflow" restricted to the 0th iteration. Therefore we only need
1349 // to check for (1) and (2).
1351 // In the current context, S is `Start`, X is `Step`, Ext is `ExtendOpTy` and T
1352 // is `Delta` (defined below).
1354 template <typename ExtendOpTy>
1355 bool ScalarEvolution::proveNoWrapByVaryingStart(const SCEV *Start,
1358 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1360 // We restrict `Start` to a constant to prevent SCEV from spending too much
1361 // time here. It is correct (but more expensive) to continue with a
1362 // non-constant `Start` and do a general SCEV subtraction to compute
1363 // `PreStart` below.
1365 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start);
1369 APInt StartAI = StartC->getValue()->getValue();
1371 for (unsigned Delta : {-2, -1, 1, 2}) {
1372 const SCEV *PreStart = getConstant(StartAI - Delta);
1374 FoldingSetNodeID ID;
1375 ID.AddInteger(scAddRecExpr);
1376 ID.AddPointer(PreStart);
1377 ID.AddPointer(Step);
1381 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1383 // Give up if we don't already have the add recurrence we need because
1384 // actually constructing an add recurrence is relatively expensive.
1385 if (PreAR && PreAR->getNoWrapFlags(WrapType)) { // proves (2)
1386 const SCEV *DeltaS = getConstant(StartC->getType(), Delta);
1387 ICmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1388 const SCEV *Limit = ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(
1389 DeltaS, &Pred, this);
1390 if (Limit && isKnownPredicate(Pred, PreAR, Limit)) // proves (1)
1398 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
1400 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1401 "This is not an extending conversion!");
1402 assert(isSCEVable(Ty) &&
1403 "This is not a conversion to a SCEVable type!");
1404 Ty = getEffectiveSCEVType(Ty);
1406 // Fold if the operand is constant.
1407 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1409 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1411 // zext(zext(x)) --> zext(x)
1412 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1413 return getZeroExtendExpr(SZ->getOperand(), Ty);
1415 // Before doing any expensive analysis, check to see if we've already
1416 // computed a SCEV for this Op and Ty.
1417 FoldingSetNodeID ID;
1418 ID.AddInteger(scZeroExtend);
1422 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1424 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1425 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1426 // It's possible the bits taken off by the truncate were all zero bits. If
1427 // so, we should be able to simplify this further.
1428 const SCEV *X = ST->getOperand();
1429 ConstantRange CR = getUnsignedRange(X);
1430 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1431 unsigned NewBits = getTypeSizeInBits(Ty);
1432 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1433 CR.zextOrTrunc(NewBits)))
1434 return getTruncateOrZeroExtend(X, Ty);
1437 // If the input value is a chrec scev, and we can prove that the value
1438 // did not overflow the old, smaller, value, we can zero extend all of the
1439 // operands (often constants). This allows analysis of something like
1440 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1441 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1442 if (AR->isAffine()) {
1443 const SCEV *Start = AR->getStart();
1444 const SCEV *Step = AR->getStepRecurrence(*this);
1445 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1446 const Loop *L = AR->getLoop();
1448 // If we have special knowledge that this addrec won't overflow,
1449 // we don't need to do any further analysis.
1450 if (AR->getNoWrapFlags(SCEV::FlagNUW))
1451 return getAddRecExpr(
1452 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1453 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1455 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1456 // Note that this serves two purposes: It filters out loops that are
1457 // simply not analyzable, and it covers the case where this code is
1458 // being called from within backedge-taken count analysis, such that
1459 // attempting to ask for the backedge-taken count would likely result
1460 // in infinite recursion. In the later case, the analysis code will
1461 // cope with a conservative value, and it will take care to purge
1462 // that value once it has finished.
1463 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1464 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1465 // Manually compute the final value for AR, checking for
1468 // Check whether the backedge-taken count can be losslessly casted to
1469 // the addrec's type. The count is always unsigned.
1470 const SCEV *CastedMaxBECount =
1471 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1472 const SCEV *RecastedMaxBECount =
1473 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1474 if (MaxBECount == RecastedMaxBECount) {
1475 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1476 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1477 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1478 const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul), WideTy);
1479 const SCEV *WideStart = getZeroExtendExpr(Start, WideTy);
1480 const SCEV *WideMaxBECount =
1481 getZeroExtendExpr(CastedMaxBECount, WideTy);
1482 const SCEV *OperandExtendedAdd =
1483 getAddExpr(WideStart,
1484 getMulExpr(WideMaxBECount,
1485 getZeroExtendExpr(Step, WideTy)));
1486 if (ZAdd == OperandExtendedAdd) {
1487 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1488 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1489 // Return the expression with the addrec on the outside.
1490 return getAddRecExpr(
1491 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1492 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1494 // Similar to above, only this time treat the step value as signed.
1495 // This covers loops that count down.
1496 OperandExtendedAdd =
1497 getAddExpr(WideStart,
1498 getMulExpr(WideMaxBECount,
1499 getSignExtendExpr(Step, WideTy)));
1500 if (ZAdd == OperandExtendedAdd) {
1501 // Cache knowledge of AR NW, which is propagated to this AddRec.
1502 // Negative step causes unsigned wrap, but it still can't self-wrap.
1503 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1504 // Return the expression with the addrec on the outside.
1505 return getAddRecExpr(
1506 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1507 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1511 // If the backedge is guarded by a comparison with the pre-inc value
1512 // the addrec is safe. Also, if the entry is guarded by a comparison
1513 // with the start value and the backedge is guarded by a comparison
1514 // with the post-inc value, the addrec is safe.
1515 if (isKnownPositive(Step)) {
1516 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1517 getUnsignedRange(Step).getUnsignedMax());
1518 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1519 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1520 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1521 AR->getPostIncExpr(*this), N))) {
1522 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1523 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1524 // Return the expression with the addrec on the outside.
1525 return getAddRecExpr(
1526 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1527 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1529 } else if (isKnownNegative(Step)) {
1530 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1531 getSignedRange(Step).getSignedMin());
1532 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1533 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1534 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1535 AR->getPostIncExpr(*this), N))) {
1536 // Cache knowledge of AR NW, which is propagated to this AddRec.
1537 // Negative step causes unsigned wrap, but it still can't self-wrap.
1538 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1539 // Return the expression with the addrec on the outside.
1540 return getAddRecExpr(
1541 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1542 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1547 if (proveNoWrapByVaryingStart<SCEVZeroExtendExpr>(Start, Step, L)) {
1548 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1549 return getAddRecExpr(
1550 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1551 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1555 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1556 // zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw>
1557 if (SA->getNoWrapFlags(SCEV::FlagNUW)) {
1558 // If the addition does not unsign overflow then we can, by definition,
1559 // commute the zero extension with the addition operation.
1560 SmallVector<const SCEV *, 4> Ops;
1561 for (const auto *Op : SA->operands())
1562 Ops.push_back(getZeroExtendExpr(Op, Ty));
1563 return getAddExpr(Ops, SCEV::FlagNUW);
1567 // The cast wasn't folded; create an explicit cast node.
1568 // Recompute the insert position, as it may have been invalidated.
1569 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1570 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1572 UniqueSCEVs.InsertNode(S, IP);
1576 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1578 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1579 "This is not an extending conversion!");
1580 assert(isSCEVable(Ty) &&
1581 "This is not a conversion to a SCEVable type!");
1582 Ty = getEffectiveSCEVType(Ty);
1584 // Fold if the operand is constant.
1585 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1587 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1589 // sext(sext(x)) --> sext(x)
1590 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1591 return getSignExtendExpr(SS->getOperand(), Ty);
1593 // sext(zext(x)) --> zext(x)
1594 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1595 return getZeroExtendExpr(SZ->getOperand(), Ty);
1597 // Before doing any expensive analysis, check to see if we've already
1598 // computed a SCEV for this Op and Ty.
1599 FoldingSetNodeID ID;
1600 ID.AddInteger(scSignExtend);
1604 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1606 // If the input value is provably positive, build a zext instead.
1607 if (isKnownNonNegative(Op))
1608 return getZeroExtendExpr(Op, Ty);
1610 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1611 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1612 // It's possible the bits taken off by the truncate were all sign bits. If
1613 // so, we should be able to simplify this further.
1614 const SCEV *X = ST->getOperand();
1615 ConstantRange CR = getSignedRange(X);
1616 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1617 unsigned NewBits = getTypeSizeInBits(Ty);
1618 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1619 CR.sextOrTrunc(NewBits)))
1620 return getTruncateOrSignExtend(X, Ty);
1623 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1624 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1625 if (SA->getNumOperands() == 2) {
1626 auto *SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1627 auto *SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1629 if (auto *SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1630 const APInt &C1 = SC1->getValue()->getValue();
1631 const APInt &C2 = SC2->getValue()->getValue();
1632 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1633 C2.ugt(C1) && C2.isPowerOf2())
1634 return getAddExpr(getSignExtendExpr(SC1, Ty),
1635 getSignExtendExpr(SMul, Ty));
1640 // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw>
1641 if (SA->getNoWrapFlags(SCEV::FlagNSW)) {
1642 // If the addition does not sign overflow then we can, by definition,
1643 // commute the sign extension with the addition operation.
1644 SmallVector<const SCEV *, 4> Ops;
1645 for (const auto *Op : SA->operands())
1646 Ops.push_back(getSignExtendExpr(Op, Ty));
1647 return getAddExpr(Ops, SCEV::FlagNSW);
1650 // If the input value is a chrec scev, and we can prove that the value
1651 // did not overflow the old, smaller, value, we can sign extend all of the
1652 // operands (often constants). This allows analysis of something like
1653 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1654 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1655 if (AR->isAffine()) {
1656 const SCEV *Start = AR->getStart();
1657 const SCEV *Step = AR->getStepRecurrence(*this);
1658 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1659 const Loop *L = AR->getLoop();
1661 // If we have special knowledge that this addrec won't overflow,
1662 // we don't need to do any further analysis.
1663 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1664 return getAddRecExpr(
1665 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1666 getSignExtendExpr(Step, Ty), L, SCEV::FlagNSW);
1668 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1669 // Note that this serves two purposes: It filters out loops that are
1670 // simply not analyzable, and it covers the case where this code is
1671 // being called from within backedge-taken count analysis, such that
1672 // attempting to ask for the backedge-taken count would likely result
1673 // in infinite recursion. In the later case, the analysis code will
1674 // cope with a conservative value, and it will take care to purge
1675 // that value once it has finished.
1676 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1677 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1678 // Manually compute the final value for AR, checking for
1681 // Check whether the backedge-taken count can be losslessly casted to
1682 // the addrec's type. The count is always unsigned.
1683 const SCEV *CastedMaxBECount =
1684 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1685 const SCEV *RecastedMaxBECount =
1686 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1687 if (MaxBECount == RecastedMaxBECount) {
1688 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1689 // Check whether Start+Step*MaxBECount has no signed overflow.
1690 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1691 const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul), WideTy);
1692 const SCEV *WideStart = getSignExtendExpr(Start, WideTy);
1693 const SCEV *WideMaxBECount =
1694 getZeroExtendExpr(CastedMaxBECount, WideTy);
1695 const SCEV *OperandExtendedAdd =
1696 getAddExpr(WideStart,
1697 getMulExpr(WideMaxBECount,
1698 getSignExtendExpr(Step, WideTy)));
1699 if (SAdd == OperandExtendedAdd) {
1700 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1701 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1702 // Return the expression with the addrec on the outside.
1703 return getAddRecExpr(
1704 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1705 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1707 // Similar to above, only this time treat the step value as unsigned.
1708 // This covers loops that count up with an unsigned step.
1709 OperandExtendedAdd =
1710 getAddExpr(WideStart,
1711 getMulExpr(WideMaxBECount,
1712 getZeroExtendExpr(Step, WideTy)));
1713 if (SAdd == OperandExtendedAdd) {
1714 // If AR wraps around then
1716 // abs(Step) * MaxBECount > unsigned-max(AR->getType())
1717 // => SAdd != OperandExtendedAdd
1719 // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=>
1720 // (SAdd == OperandExtendedAdd => AR is NW)
1722 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1724 // Return the expression with the addrec on the outside.
1725 return getAddRecExpr(
1726 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1727 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1731 // If the backedge is guarded by a comparison with the pre-inc value
1732 // the addrec is safe. Also, if the entry is guarded by a comparison
1733 // with the start value and the backedge is guarded by a comparison
1734 // with the post-inc value, the addrec is safe.
1735 ICmpInst::Predicate Pred;
1736 const SCEV *OverflowLimit =
1737 getSignedOverflowLimitForStep(Step, &Pred, this);
1738 if (OverflowLimit &&
1739 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1740 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1741 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1743 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1744 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1745 return getAddRecExpr(
1746 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1747 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1750 // If Start and Step are constants, check if we can apply this
1752 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1753 auto *SC1 = dyn_cast<SCEVConstant>(Start);
1754 auto *SC2 = dyn_cast<SCEVConstant>(Step);
1756 const APInt &C1 = SC1->getValue()->getValue();
1757 const APInt &C2 = SC2->getValue()->getValue();
1758 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1760 Start = getSignExtendExpr(Start, Ty);
1761 const SCEV *NewAR = getAddRecExpr(getZero(AR->getType()), Step, L,
1762 AR->getNoWrapFlags());
1763 return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
1767 if (proveNoWrapByVaryingStart<SCEVSignExtendExpr>(Start, Step, L)) {
1768 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1769 return getAddRecExpr(
1770 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1771 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1775 // The cast wasn't folded; create an explicit cast node.
1776 // Recompute the insert position, as it may have been invalidated.
1777 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1778 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1780 UniqueSCEVs.InsertNode(S, IP);
1784 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1785 /// unspecified bits out to the given type.
1787 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1789 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1790 "This is not an extending conversion!");
1791 assert(isSCEVable(Ty) &&
1792 "This is not a conversion to a SCEVable type!");
1793 Ty = getEffectiveSCEVType(Ty);
1795 // Sign-extend negative constants.
1796 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1797 if (SC->getValue()->getValue().isNegative())
1798 return getSignExtendExpr(Op, Ty);
1800 // Peel off a truncate cast.
1801 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1802 const SCEV *NewOp = T->getOperand();
1803 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1804 return getAnyExtendExpr(NewOp, Ty);
1805 return getTruncateOrNoop(NewOp, Ty);
1808 // Next try a zext cast. If the cast is folded, use it.
1809 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1810 if (!isa<SCEVZeroExtendExpr>(ZExt))
1813 // Next try a sext cast. If the cast is folded, use it.
1814 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1815 if (!isa<SCEVSignExtendExpr>(SExt))
1818 // Force the cast to be folded into the operands of an addrec.
1819 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1820 SmallVector<const SCEV *, 4> Ops;
1821 for (const SCEV *Op : AR->operands())
1822 Ops.push_back(getAnyExtendExpr(Op, Ty));
1823 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1826 // If the expression is obviously signed, use the sext cast value.
1827 if (isa<SCEVSMaxExpr>(Op))
1830 // Absent any other information, use the zext cast value.
1834 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1835 /// a list of operands to be added under the given scale, update the given
1836 /// map. This is a helper function for getAddRecExpr. As an example of
1837 /// what it does, given a sequence of operands that would form an add
1838 /// expression like this:
1840 /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
1842 /// where A and B are constants, update the map with these values:
1844 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1846 /// and add 13 + A*B*29 to AccumulatedConstant.
1847 /// This will allow getAddRecExpr to produce this:
1849 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1851 /// This form often exposes folding opportunities that are hidden in
1852 /// the original operand list.
1854 /// Return true iff it appears that any interesting folding opportunities
1855 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1856 /// the common case where no interesting opportunities are present, and
1857 /// is also used as a check to avoid infinite recursion.
1860 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1861 SmallVectorImpl<const SCEV *> &NewOps,
1862 APInt &AccumulatedConstant,
1863 const SCEV *const *Ops, size_t NumOperands,
1865 ScalarEvolution &SE) {
1866 bool Interesting = false;
1868 // Iterate over the add operands. They are sorted, with constants first.
1870 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1872 // Pull a buried constant out to the outside.
1873 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1875 AccumulatedConstant += Scale * C->getValue()->getValue();
1878 // Next comes everything else. We're especially interested in multiplies
1879 // here, but they're in the middle, so just visit the rest with one loop.
1880 for (; i != NumOperands; ++i) {
1881 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1882 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1884 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1885 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1886 // A multiplication of a constant with another add; recurse.
1887 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1889 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1890 Add->op_begin(), Add->getNumOperands(),
1893 // A multiplication of a constant with some other value. Update
1895 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1896 const SCEV *Key = SE.getMulExpr(MulOps);
1897 auto Pair = M.insert(std::make_pair(Key, NewScale));
1899 NewOps.push_back(Pair.first->first);
1901 Pair.first->second += NewScale;
1902 // The map already had an entry for this value, which may indicate
1903 // a folding opportunity.
1908 // An ordinary operand. Update the map.
1909 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1910 M.insert(std::make_pair(Ops[i], Scale));
1912 NewOps.push_back(Pair.first->first);
1914 Pair.first->second += Scale;
1915 // The map already had an entry for this value, which may indicate
1916 // a folding opportunity.
1926 struct APIntCompare {
1927 bool operator()(const APInt &LHS, const APInt &RHS) const {
1928 return LHS.ult(RHS);
1933 // We're trying to construct a SCEV of type `Type' with `Ops' as operands and
1934 // `OldFlags' as can't-wrap behavior. Infer a more aggressive set of
1935 // can't-overflow flags for the operation if possible.
1936 static SCEV::NoWrapFlags
1937 StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
1938 const SmallVectorImpl<const SCEV *> &Ops,
1939 SCEV::NoWrapFlags Flags) {
1940 using namespace std::placeholders;
1941 typedef OverflowingBinaryOperator OBO;
1944 Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr;
1946 assert(CanAnalyze && "don't call from other places!");
1948 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1949 SCEV::NoWrapFlags SignOrUnsignWrap =
1950 ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
1952 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1953 auto IsKnownNonNegative =
1954 std::bind(std::mem_fn(&ScalarEvolution::isKnownNonNegative), SE, _1);
1956 if (SignOrUnsignWrap == SCEV::FlagNSW &&
1957 std::all_of(Ops.begin(), Ops.end(), IsKnownNonNegative))
1959 ScalarEvolution::setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1961 SignOrUnsignWrap = ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
1963 if (SignOrUnsignWrap != SignOrUnsignMask && Type == scAddExpr &&
1964 Ops.size() == 2 && isa<SCEVConstant>(Ops[0])) {
1966 // (A + C) --> (A + C)<nsw> if the addition does not sign overflow
1967 // (A + C) --> (A + C)<nuw> if the addition does not unsign overflow
1969 const APInt &C = cast<SCEVConstant>(Ops[0])->getValue()->getValue();
1970 if (!(SignOrUnsignWrap & SCEV::FlagNSW)) {
1972 ConstantRange::makeNoWrapRegion(Instruction::Add, C, OBO::NoSignedWrap);
1973 if (NSWRegion.contains(SE->getSignedRange(Ops[1])))
1974 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
1976 if (!(SignOrUnsignWrap & SCEV::FlagNUW)) {
1978 ConstantRange::makeNoWrapRegion(Instruction::Add, C,
1979 OBO::NoUnsignedWrap);
1980 if (NUWRegion.contains(SE->getUnsignedRange(Ops[1])))
1981 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
1988 /// getAddExpr - Get a canonical add expression, or something simpler if
1990 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1991 SCEV::NoWrapFlags Flags) {
1992 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
1993 "only nuw or nsw allowed");
1994 assert(!Ops.empty() && "Cannot get empty add!");
1995 if (Ops.size() == 1) return Ops[0];
1997 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1998 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1999 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2000 "SCEVAddExpr operand types don't match!");
2003 // Sort by complexity, this groups all similar expression types together.
2004 GroupByComplexity(Ops, &LI);
2006 Flags = StrengthenNoWrapFlags(this, scAddExpr, Ops, Flags);
2008 // If there are any constants, fold them together.
2010 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2012 assert(Idx < Ops.size());
2013 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2014 // We found two constants, fold them together!
2015 Ops[0] = getConstant(LHSC->getValue()->getValue() +
2016 RHSC->getValue()->getValue());
2017 if (Ops.size() == 2) return Ops[0];
2018 Ops.erase(Ops.begin()+1); // Erase the folded element
2019 LHSC = cast<SCEVConstant>(Ops[0]);
2022 // If we are left with a constant zero being added, strip it off.
2023 if (LHSC->getValue()->isZero()) {
2024 Ops.erase(Ops.begin());
2028 if (Ops.size() == 1) return Ops[0];
2031 // Okay, check to see if the same value occurs in the operand list more than
2032 // once. If so, merge them together into an multiply expression. Since we
2033 // sorted the list, these values are required to be adjacent.
2034 Type *Ty = Ops[0]->getType();
2035 bool FoundMatch = false;
2036 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
2037 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
2038 // Scan ahead to count how many equal operands there are.
2040 while (i+Count != e && Ops[i+Count] == Ops[i])
2042 // Merge the values into a multiply.
2043 const SCEV *Scale = getConstant(Ty, Count);
2044 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
2045 if (Ops.size() == Count)
2048 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
2049 --i; e -= Count - 1;
2053 return getAddExpr(Ops, Flags);
2055 // Check for truncates. If all the operands are truncated from the same
2056 // type, see if factoring out the truncate would permit the result to be
2057 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
2058 // if the contents of the resulting outer trunc fold to something simple.
2059 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
2060 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
2061 Type *DstType = Trunc->getType();
2062 Type *SrcType = Trunc->getOperand()->getType();
2063 SmallVector<const SCEV *, 8> LargeOps;
2065 // Check all the operands to see if they can be represented in the
2066 // source type of the truncate.
2067 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
2068 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
2069 if (T->getOperand()->getType() != SrcType) {
2073 LargeOps.push_back(T->getOperand());
2074 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2075 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
2076 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
2077 SmallVector<const SCEV *, 8> LargeMulOps;
2078 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
2079 if (const SCEVTruncateExpr *T =
2080 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
2081 if (T->getOperand()->getType() != SrcType) {
2085 LargeMulOps.push_back(T->getOperand());
2086 } else if (const auto *C = dyn_cast<SCEVConstant>(M->getOperand(j))) {
2087 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
2094 LargeOps.push_back(getMulExpr(LargeMulOps));
2101 // Evaluate the expression in the larger type.
2102 const SCEV *Fold = getAddExpr(LargeOps, Flags);
2103 // If it folds to something simple, use it. Otherwise, don't.
2104 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
2105 return getTruncateExpr(Fold, DstType);
2109 // Skip past any other cast SCEVs.
2110 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
2113 // If there are add operands they would be next.
2114 if (Idx < Ops.size()) {
2115 bool DeletedAdd = false;
2116 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
2117 // If we have an add, expand the add operands onto the end of the operands
2119 Ops.erase(Ops.begin()+Idx);
2120 Ops.append(Add->op_begin(), Add->op_end());
2124 // If we deleted at least one add, we added operands to the end of the list,
2125 // and they are not necessarily sorted. Recurse to resort and resimplify
2126 // any operands we just acquired.
2128 return getAddExpr(Ops);
2131 // Skip over the add expression until we get to a multiply.
2132 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2135 // Check to see if there are any folding opportunities present with
2136 // operands multiplied by constant values.
2137 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
2138 uint64_t BitWidth = getTypeSizeInBits(Ty);
2139 DenseMap<const SCEV *, APInt> M;
2140 SmallVector<const SCEV *, 8> NewOps;
2141 APInt AccumulatedConstant(BitWidth, 0);
2142 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2143 Ops.data(), Ops.size(),
2144 APInt(BitWidth, 1), *this)) {
2145 // Some interesting folding opportunity is present, so its worthwhile to
2146 // re-generate the operands list. Group the operands by constant scale,
2147 // to avoid multiplying by the same constant scale multiple times.
2148 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
2149 for (SmallVectorImpl<const SCEV *>::const_iterator I = NewOps.begin(),
2150 E = NewOps.end(); I != E; ++I)
2151 MulOpLists[M.find(*I)->second].push_back(*I);
2152 // Re-generate the operands list.
2154 if (AccumulatedConstant != 0)
2155 Ops.push_back(getConstant(AccumulatedConstant));
2156 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
2157 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
2159 Ops.push_back(getMulExpr(getConstant(I->first),
2160 getAddExpr(I->second)));
2163 if (Ops.size() == 1)
2165 return getAddExpr(Ops);
2169 // If we are adding something to a multiply expression, make sure the
2170 // something is not already an operand of the multiply. If so, merge it into
2172 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
2173 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
2174 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
2175 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
2176 if (isa<SCEVConstant>(MulOpSCEV))
2178 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
2179 if (MulOpSCEV == Ops[AddOp]) {
2180 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
2181 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
2182 if (Mul->getNumOperands() != 2) {
2183 // If the multiply has more than two operands, we must get the
2185 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2186 Mul->op_begin()+MulOp);
2187 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2188 InnerMul = getMulExpr(MulOps);
2190 const SCEV *One = getOne(Ty);
2191 const SCEV *AddOne = getAddExpr(One, InnerMul);
2192 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
2193 if (Ops.size() == 2) return OuterMul;
2195 Ops.erase(Ops.begin()+AddOp);
2196 Ops.erase(Ops.begin()+Idx-1);
2198 Ops.erase(Ops.begin()+Idx);
2199 Ops.erase(Ops.begin()+AddOp-1);
2201 Ops.push_back(OuterMul);
2202 return getAddExpr(Ops);
2205 // Check this multiply against other multiplies being added together.
2206 for (unsigned OtherMulIdx = Idx+1;
2207 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
2209 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
2210 // If MulOp occurs in OtherMul, we can fold the two multiplies
2212 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
2213 OMulOp != e; ++OMulOp)
2214 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
2215 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
2216 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
2217 if (Mul->getNumOperands() != 2) {
2218 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2219 Mul->op_begin()+MulOp);
2220 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2221 InnerMul1 = getMulExpr(MulOps);
2223 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2224 if (OtherMul->getNumOperands() != 2) {
2225 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2226 OtherMul->op_begin()+OMulOp);
2227 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2228 InnerMul2 = getMulExpr(MulOps);
2230 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
2231 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2232 if (Ops.size() == 2) return OuterMul;
2233 Ops.erase(Ops.begin()+Idx);
2234 Ops.erase(Ops.begin()+OtherMulIdx-1);
2235 Ops.push_back(OuterMul);
2236 return getAddExpr(Ops);
2242 // If there are any add recurrences in the operands list, see if any other
2243 // added values are loop invariant. If so, we can fold them into the
2245 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2248 // Scan over all recurrences, trying to fold loop invariants into them.
2249 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2250 // Scan all of the other operands to this add and add them to the vector if
2251 // they are loop invariant w.r.t. the recurrence.
2252 SmallVector<const SCEV *, 8> LIOps;
2253 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2254 const Loop *AddRecLoop = AddRec->getLoop();
2255 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2256 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2257 LIOps.push_back(Ops[i]);
2258 Ops.erase(Ops.begin()+i);
2262 // If we found some loop invariants, fold them into the recurrence.
2263 if (!LIOps.empty()) {
2264 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2265 LIOps.push_back(AddRec->getStart());
2267 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2269 AddRecOps[0] = getAddExpr(LIOps);
2271 // Build the new addrec. Propagate the NUW and NSW flags if both the
2272 // outer add and the inner addrec are guaranteed to have no overflow.
2273 // Always propagate NW.
2274 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2275 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2277 // If all of the other operands were loop invariant, we are done.
2278 if (Ops.size() == 1) return NewRec;
2280 // Otherwise, add the folded AddRec by the non-invariant parts.
2281 for (unsigned i = 0;; ++i)
2282 if (Ops[i] == AddRec) {
2286 return getAddExpr(Ops);
2289 // Okay, if there weren't any loop invariants to be folded, check to see if
2290 // there are multiple AddRec's with the same loop induction variable being
2291 // added together. If so, we can fold them.
2292 for (unsigned OtherIdx = Idx+1;
2293 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2295 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2296 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2297 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2299 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2301 if (const SCEVAddRecExpr *OtherAddRec =
2302 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2303 if (OtherAddRec->getLoop() == AddRecLoop) {
2304 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2306 if (i >= AddRecOps.size()) {
2307 AddRecOps.append(OtherAddRec->op_begin()+i,
2308 OtherAddRec->op_end());
2311 AddRecOps[i] = getAddExpr(AddRecOps[i],
2312 OtherAddRec->getOperand(i));
2314 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2316 // Step size has changed, so we cannot guarantee no self-wraparound.
2317 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2318 return getAddExpr(Ops);
2321 // Otherwise couldn't fold anything into this recurrence. Move onto the
2325 // Okay, it looks like we really DO need an add expr. Check to see if we
2326 // already have one, otherwise create a new one.
2327 FoldingSetNodeID ID;
2328 ID.AddInteger(scAddExpr);
2329 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2330 ID.AddPointer(Ops[i]);
2333 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2335 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2336 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2337 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
2339 UniqueSCEVs.InsertNode(S, IP);
2341 S->setNoWrapFlags(Flags);
2345 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2347 if (j > 1 && k / j != i) Overflow = true;
2351 /// Compute the result of "n choose k", the binomial coefficient. If an
2352 /// intermediate computation overflows, Overflow will be set and the return will
2353 /// be garbage. Overflow is not cleared on absence of overflow.
2354 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2355 // We use the multiplicative formula:
2356 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2357 // At each iteration, we take the n-th term of the numeral and divide by the
2358 // (k-n)th term of the denominator. This division will always produce an
2359 // integral result, and helps reduce the chance of overflow in the
2360 // intermediate computations. However, we can still overflow even when the
2361 // final result would fit.
2363 if (n == 0 || n == k) return 1;
2364 if (k > n) return 0;
2370 for (uint64_t i = 1; i <= k; ++i) {
2371 r = umul_ov(r, n-(i-1), Overflow);
2377 /// Determine if any of the operands in this SCEV are a constant or if
2378 /// any of the add or multiply expressions in this SCEV contain a constant.
2379 static bool containsConstantSomewhere(const SCEV *StartExpr) {
2380 SmallVector<const SCEV *, 4> Ops;
2381 Ops.push_back(StartExpr);
2382 while (!Ops.empty()) {
2383 const SCEV *CurrentExpr = Ops.pop_back_val();
2384 if (isa<SCEVConstant>(*CurrentExpr))
2387 if (isa<SCEVAddExpr>(*CurrentExpr) || isa<SCEVMulExpr>(*CurrentExpr)) {
2388 const auto *CurrentNAry = cast<SCEVNAryExpr>(CurrentExpr);
2389 Ops.append(CurrentNAry->op_begin(), CurrentNAry->op_end());
2395 /// getMulExpr - Get a canonical multiply expression, or something simpler if
2397 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2398 SCEV::NoWrapFlags Flags) {
2399 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
2400 "only nuw or nsw allowed");
2401 assert(!Ops.empty() && "Cannot get empty mul!");
2402 if (Ops.size() == 1) return Ops[0];
2404 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2405 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2406 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2407 "SCEVMulExpr operand types don't match!");
2410 // Sort by complexity, this groups all similar expression types together.
2411 GroupByComplexity(Ops, &LI);
2413 Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
2415 // If there are any constants, fold them together.
2417 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2419 // C1*(C2+V) -> C1*C2 + C1*V
2420 if (Ops.size() == 2)
2421 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2422 // If any of Add's ops are Adds or Muls with a constant,
2423 // apply this transformation as well.
2424 if (Add->getNumOperands() == 2)
2425 if (containsConstantSomewhere(Add))
2426 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2427 getMulExpr(LHSC, Add->getOperand(1)));
2430 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2431 // We found two constants, fold them together!
2432 ConstantInt *Fold = ConstantInt::get(getContext(),
2433 LHSC->getValue()->getValue() *
2434 RHSC->getValue()->getValue());
2435 Ops[0] = getConstant(Fold);
2436 Ops.erase(Ops.begin()+1); // Erase the folded element
2437 if (Ops.size() == 1) return Ops[0];
2438 LHSC = cast<SCEVConstant>(Ops[0]);
2441 // If we are left with a constant one being multiplied, strip it off.
2442 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2443 Ops.erase(Ops.begin());
2445 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2446 // If we have a multiply of zero, it will always be zero.
2448 } else if (Ops[0]->isAllOnesValue()) {
2449 // If we have a mul by -1 of an add, try distributing the -1 among the
2451 if (Ops.size() == 2) {
2452 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2453 SmallVector<const SCEV *, 4> NewOps;
2454 bool AnyFolded = false;
2455 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
2456 E = Add->op_end(); I != E; ++I) {
2457 const SCEV *Mul = getMulExpr(Ops[0], *I);
2458 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2459 NewOps.push_back(Mul);
2462 return getAddExpr(NewOps);
2463 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2464 // Negation preserves a recurrence's no self-wrap property.
2465 SmallVector<const SCEV *, 4> Operands;
2466 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
2467 E = AddRec->op_end(); I != E; ++I) {
2468 Operands.push_back(getMulExpr(Ops[0], *I));
2470 return getAddRecExpr(Operands, AddRec->getLoop(),
2471 AddRec->getNoWrapFlags(SCEV::FlagNW));
2476 if (Ops.size() == 1)
2480 // Skip over the add expression until we get to a multiply.
2481 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2484 // If there are mul operands inline them all into this expression.
2485 if (Idx < Ops.size()) {
2486 bool DeletedMul = false;
2487 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2488 // If we have an mul, expand the mul operands onto the end of the operands
2490 Ops.erase(Ops.begin()+Idx);
2491 Ops.append(Mul->op_begin(), Mul->op_end());
2495 // If we deleted at least one mul, we added operands to the end of the list,
2496 // and they are not necessarily sorted. Recurse to resort and resimplify
2497 // any operands we just acquired.
2499 return getMulExpr(Ops);
2502 // If there are any add recurrences in the operands list, see if any other
2503 // added values are loop invariant. If so, we can fold them into the
2505 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2508 // Scan over all recurrences, trying to fold loop invariants into them.
2509 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2510 // Scan all of the other operands to this mul and add them to the vector if
2511 // they are loop invariant w.r.t. the recurrence.
2512 SmallVector<const SCEV *, 8> LIOps;
2513 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2514 const Loop *AddRecLoop = AddRec->getLoop();
2515 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2516 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2517 LIOps.push_back(Ops[i]);
2518 Ops.erase(Ops.begin()+i);
2522 // If we found some loop invariants, fold them into the recurrence.
2523 if (!LIOps.empty()) {
2524 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2525 SmallVector<const SCEV *, 4> NewOps;
2526 NewOps.reserve(AddRec->getNumOperands());
2527 const SCEV *Scale = getMulExpr(LIOps);
2528 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2529 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2531 // Build the new addrec. Propagate the NUW and NSW flags if both the
2532 // outer mul and the inner addrec are guaranteed to have no overflow.
2534 // No self-wrap cannot be guaranteed after changing the step size, but
2535 // will be inferred if either NUW or NSW is true.
2536 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2537 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2539 // If all of the other operands were loop invariant, we are done.
2540 if (Ops.size() == 1) return NewRec;
2542 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2543 for (unsigned i = 0;; ++i)
2544 if (Ops[i] == AddRec) {
2548 return getMulExpr(Ops);
2551 // Okay, if there weren't any loop invariants to be folded, check to see if
2552 // there are multiple AddRec's with the same loop induction variable being
2553 // multiplied together. If so, we can fold them.
2555 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2556 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2557 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2558 // ]]],+,...up to x=2n}.
2559 // Note that the arguments to choose() are always integers with values
2560 // known at compile time, never SCEV objects.
2562 // The implementation avoids pointless extra computations when the two
2563 // addrec's are of different length (mathematically, it's equivalent to
2564 // an infinite stream of zeros on the right).
2565 bool OpsModified = false;
2566 for (unsigned OtherIdx = Idx+1;
2567 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2569 const SCEVAddRecExpr *OtherAddRec =
2570 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2571 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2574 bool Overflow = false;
2575 Type *Ty = AddRec->getType();
2576 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2577 SmallVector<const SCEV*, 7> AddRecOps;
2578 for (int x = 0, xe = AddRec->getNumOperands() +
2579 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2580 const SCEV *Term = getZero(Ty);
2581 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2582 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2583 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2584 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2585 z < ze && !Overflow; ++z) {
2586 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2588 if (LargerThan64Bits)
2589 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2591 Coeff = Coeff1*Coeff2;
2592 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2593 const SCEV *Term1 = AddRec->getOperand(y-z);
2594 const SCEV *Term2 = OtherAddRec->getOperand(z);
2595 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2598 AddRecOps.push_back(Term);
2601 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2603 if (Ops.size() == 2) return NewAddRec;
2604 Ops[Idx] = NewAddRec;
2605 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2607 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2613 return getMulExpr(Ops);
2615 // Otherwise couldn't fold anything into this recurrence. Move onto the
2619 // Okay, it looks like we really DO need an mul expr. Check to see if we
2620 // already have one, otherwise create a new one.
2621 FoldingSetNodeID ID;
2622 ID.AddInteger(scMulExpr);
2623 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2624 ID.AddPointer(Ops[i]);
2627 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2629 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2630 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2631 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2633 UniqueSCEVs.InsertNode(S, IP);
2635 S->setNoWrapFlags(Flags);
2639 /// getUDivExpr - Get a canonical unsigned division expression, or something
2640 /// simpler if possible.
2641 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2643 assert(getEffectiveSCEVType(LHS->getType()) ==
2644 getEffectiveSCEVType(RHS->getType()) &&
2645 "SCEVUDivExpr operand types don't match!");
2647 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2648 if (RHSC->getValue()->equalsInt(1))
2649 return LHS; // X udiv 1 --> x
2650 // If the denominator is zero, the result of the udiv is undefined. Don't
2651 // try to analyze it, because the resolution chosen here may differ from
2652 // the resolution chosen in other parts of the compiler.
2653 if (!RHSC->getValue()->isZero()) {
2654 // Determine if the division can be folded into the operands of
2656 // TODO: Generalize this to non-constants by using known-bits information.
2657 Type *Ty = LHS->getType();
2658 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2659 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2660 // For non-power-of-two values, effectively round the value up to the
2661 // nearest power of two.
2662 if (!RHSC->getValue()->getValue().isPowerOf2())
2664 IntegerType *ExtTy =
2665 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2666 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2667 if (const SCEVConstant *Step =
2668 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2669 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2670 const APInt &StepInt = Step->getValue()->getValue();
2671 const APInt &DivInt = RHSC->getValue()->getValue();
2672 if (!StepInt.urem(DivInt) &&
2673 getZeroExtendExpr(AR, ExtTy) ==
2674 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2675 getZeroExtendExpr(Step, ExtTy),
2676 AR->getLoop(), SCEV::FlagAnyWrap)) {
2677 SmallVector<const SCEV *, 4> Operands;
2678 for (const SCEV *Op : AR->operands())
2679 Operands.push_back(getUDivExpr(Op, RHS));
2680 return getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagNW);
2682 /// Get a canonical UDivExpr for a recurrence.
2683 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2684 // We can currently only fold X%N if X is constant.
2685 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2686 if (StartC && !DivInt.urem(StepInt) &&
2687 getZeroExtendExpr(AR, ExtTy) ==
2688 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2689 getZeroExtendExpr(Step, ExtTy),
2690 AR->getLoop(), SCEV::FlagAnyWrap)) {
2691 const APInt &StartInt = StartC->getValue()->getValue();
2692 const APInt &StartRem = StartInt.urem(StepInt);
2694 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2695 AR->getLoop(), SCEV::FlagNW);
2698 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2699 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2700 SmallVector<const SCEV *, 4> Operands;
2701 for (const SCEV *Op : M->operands())
2702 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2703 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2704 // Find an operand that's safely divisible.
2705 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2706 const SCEV *Op = M->getOperand(i);
2707 const SCEV *Div = getUDivExpr(Op, RHSC);
2708 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2709 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2712 return getMulExpr(Operands);
2716 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2717 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2718 SmallVector<const SCEV *, 4> Operands;
2719 for (const SCEV *Op : A->operands())
2720 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2721 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2723 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2724 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2725 if (isa<SCEVUDivExpr>(Op) ||
2726 getMulExpr(Op, RHS) != A->getOperand(i))
2728 Operands.push_back(Op);
2730 if (Operands.size() == A->getNumOperands())
2731 return getAddExpr(Operands);
2735 // Fold if both operands are constant.
2736 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2737 Constant *LHSCV = LHSC->getValue();
2738 Constant *RHSCV = RHSC->getValue();
2739 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2745 FoldingSetNodeID ID;
2746 ID.AddInteger(scUDivExpr);
2750 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2751 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2753 UniqueSCEVs.InsertNode(S, IP);
2757 static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2758 APInt A = C1->getValue()->getValue().abs();
2759 APInt B = C2->getValue()->getValue().abs();
2760 uint32_t ABW = A.getBitWidth();
2761 uint32_t BBW = B.getBitWidth();
2768 return APIntOps::GreatestCommonDivisor(A, B);
2771 /// getUDivExactExpr - Get a canonical unsigned division expression, or
2772 /// something simpler if possible. There is no representation for an exact udiv
2773 /// in SCEV IR, but we can attempt to remove factors from the LHS and RHS.
2774 /// We can't do this when it's not exact because the udiv may be clearing bits.
2775 const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2777 // TODO: we could try to find factors in all sorts of things, but for now we
2778 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2779 // end of this file for inspiration.
2781 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2783 return getUDivExpr(LHS, RHS);
2785 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2786 // If the mulexpr multiplies by a constant, then that constant must be the
2787 // first element of the mulexpr.
2788 if (const auto *LHSCst = dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2789 if (LHSCst == RHSCst) {
2790 SmallVector<const SCEV *, 2> Operands;
2791 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2792 return getMulExpr(Operands);
2795 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
2796 // that there's a factor provided by one of the other terms. We need to
2798 APInt Factor = gcd(LHSCst, RHSCst);
2799 if (!Factor.isIntN(1)) {
2800 LHSCst = cast<SCEVConstant>(
2801 getConstant(LHSCst->getValue()->getValue().udiv(Factor)));
2802 RHSCst = cast<SCEVConstant>(
2803 getConstant(RHSCst->getValue()->getValue().udiv(Factor)));
2804 SmallVector<const SCEV *, 2> Operands;
2805 Operands.push_back(LHSCst);
2806 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2807 LHS = getMulExpr(Operands);
2809 Mul = dyn_cast<SCEVMulExpr>(LHS);
2811 return getUDivExactExpr(LHS, RHS);
2816 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
2817 if (Mul->getOperand(i) == RHS) {
2818 SmallVector<const SCEV *, 2> Operands;
2819 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
2820 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
2821 return getMulExpr(Operands);
2825 return getUDivExpr(LHS, RHS);
2828 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2829 /// Simplify the expression as much as possible.
2830 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2832 SCEV::NoWrapFlags Flags) {
2833 SmallVector<const SCEV *, 4> Operands;
2834 Operands.push_back(Start);
2835 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2836 if (StepChrec->getLoop() == L) {
2837 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2838 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2841 Operands.push_back(Step);
2842 return getAddRecExpr(Operands, L, Flags);
2845 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2846 /// Simplify the expression as much as possible.
2848 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2849 const Loop *L, SCEV::NoWrapFlags Flags) {
2850 if (Operands.size() == 1) return Operands[0];
2852 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2853 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2854 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2855 "SCEVAddRecExpr operand types don't match!");
2856 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2857 assert(isLoopInvariant(Operands[i], L) &&
2858 "SCEVAddRecExpr operand is not loop-invariant!");
2861 if (Operands.back()->isZero()) {
2862 Operands.pop_back();
2863 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2866 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2867 // use that information to infer NUW and NSW flags. However, computing a
2868 // BE count requires calling getAddRecExpr, so we may not yet have a
2869 // meaningful BE count at this point (and if we don't, we'd be stuck
2870 // with a SCEVCouldNotCompute as the cached BE count).
2872 Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags);
2874 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2875 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2876 const Loop *NestedLoop = NestedAR->getLoop();
2877 if (L->contains(NestedLoop)
2878 ? (L->getLoopDepth() < NestedLoop->getLoopDepth())
2879 : (!NestedLoop->contains(L) &&
2880 DT.dominates(L->getHeader(), NestedLoop->getHeader()))) {
2881 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2882 NestedAR->op_end());
2883 Operands[0] = NestedAR->getStart();
2884 // AddRecs require their operands be loop-invariant with respect to their
2885 // loops. Don't perform this transformation if it would break this
2888 std::all_of(Operands.begin(), Operands.end(),
2889 [&](const SCEV *Op) { return isLoopInvariant(Op, L); });
2892 // Create a recurrence for the outer loop with the same step size.
2894 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2895 // inner recurrence has the same property.
2896 SCEV::NoWrapFlags OuterFlags =
2897 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2899 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2900 AllInvariant = std::all_of(
2901 NestedOperands.begin(), NestedOperands.end(),
2902 [&](const SCEV *Op) { return isLoopInvariant(Op, NestedLoop); });
2905 // Ok, both add recurrences are valid after the transformation.
2907 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2908 // the outer recurrence has the same property.
2909 SCEV::NoWrapFlags InnerFlags =
2910 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2911 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2914 // Reset Operands to its original state.
2915 Operands[0] = NestedAR;
2919 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2920 // already have one, otherwise create a new one.
2921 FoldingSetNodeID ID;
2922 ID.AddInteger(scAddRecExpr);
2923 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2924 ID.AddPointer(Operands[i]);
2928 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2930 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2931 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2932 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2933 O, Operands.size(), L);
2934 UniqueSCEVs.InsertNode(S, IP);
2936 S->setNoWrapFlags(Flags);
2941 ScalarEvolution::getGEPExpr(Type *PointeeType, const SCEV *BaseExpr,
2942 const SmallVectorImpl<const SCEV *> &IndexExprs,
2944 // getSCEV(Base)->getType() has the same address space as Base->getType()
2945 // because SCEV::getType() preserves the address space.
2946 Type *IntPtrTy = getEffectiveSCEVType(BaseExpr->getType());
2947 // FIXME(PR23527): Don't blindly transfer the inbounds flag from the GEP
2948 // instruction to its SCEV, because the Instruction may be guarded by control
2949 // flow and the no-overflow bits may not be valid for the expression in any
2950 // context. This can be fixed similarly to how these flags are handled for
2952 SCEV::NoWrapFlags Wrap = InBounds ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
2954 const SCEV *TotalOffset = getZero(IntPtrTy);
2955 // The address space is unimportant. The first thing we do on CurTy is getting
2956 // its element type.
2957 Type *CurTy = PointerType::getUnqual(PointeeType);
2958 for (const SCEV *IndexExpr : IndexExprs) {
2959 // Compute the (potentially symbolic) offset in bytes for this index.
2960 if (StructType *STy = dyn_cast<StructType>(CurTy)) {
2961 // For a struct, add the member offset.
2962 ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue();
2963 unsigned FieldNo = Index->getZExtValue();
2964 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
2966 // Add the field offset to the running total offset.
2967 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
2969 // Update CurTy to the type of the field at Index.
2970 CurTy = STy->getTypeAtIndex(Index);
2972 // Update CurTy to its element type.
2973 CurTy = cast<SequentialType>(CurTy)->getElementType();
2974 // For an array, add the element offset, explicitly scaled.
2975 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, CurTy);
2976 // Getelementptr indices are signed.
2977 IndexExpr = getTruncateOrSignExtend(IndexExpr, IntPtrTy);
2979 // Multiply the index by the element size to compute the element offset.
2980 const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, Wrap);
2982 // Add the element offset to the running total offset.
2983 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
2987 // Add the total offset from all the GEP indices to the base.
2988 return getAddExpr(BaseExpr, TotalOffset, Wrap);
2991 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2993 SmallVector<const SCEV *, 2> Ops;
2996 return getSMaxExpr(Ops);
3000 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3001 assert(!Ops.empty() && "Cannot get empty smax!");
3002 if (Ops.size() == 1) return Ops[0];
3004 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3005 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3006 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3007 "SCEVSMaxExpr operand types don't match!");
3010 // Sort by complexity, this groups all similar expression types together.
3011 GroupByComplexity(Ops, &LI);
3013 // If there are any constants, fold them together.
3015 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3017 assert(Idx < Ops.size());
3018 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3019 // We found two constants, fold them together!
3020 ConstantInt *Fold = ConstantInt::get(getContext(),
3021 APIntOps::smax(LHSC->getValue()->getValue(),
3022 RHSC->getValue()->getValue()));
3023 Ops[0] = getConstant(Fold);
3024 Ops.erase(Ops.begin()+1); // Erase the folded element
3025 if (Ops.size() == 1) return Ops[0];
3026 LHSC = cast<SCEVConstant>(Ops[0]);
3029 // If we are left with a constant minimum-int, strip it off.
3030 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
3031 Ops.erase(Ops.begin());
3033 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
3034 // If we have an smax with a constant maximum-int, it will always be
3039 if (Ops.size() == 1) return Ops[0];
3042 // Find the first SMax
3043 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
3046 // Check to see if one of the operands is an SMax. If so, expand its operands
3047 // onto our operand list, and recurse to simplify.
3048 if (Idx < Ops.size()) {
3049 bool DeletedSMax = false;
3050 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
3051 Ops.erase(Ops.begin()+Idx);
3052 Ops.append(SMax->op_begin(), SMax->op_end());
3057 return getSMaxExpr(Ops);
3060 // Okay, check to see if the same value occurs in the operand list twice. If
3061 // so, delete one. Since we sorted the list, these values are required to
3063 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3064 // X smax Y smax Y --> X smax Y
3065 // X smax Y --> X, if X is always greater than Y
3066 if (Ops[i] == Ops[i+1] ||
3067 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
3068 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3070 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
3071 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3075 if (Ops.size() == 1) return Ops[0];
3077 assert(!Ops.empty() && "Reduced smax down to nothing!");
3079 // Okay, it looks like we really DO need an smax expr. Check to see if we
3080 // already have one, otherwise create a new one.
3081 FoldingSetNodeID ID;
3082 ID.AddInteger(scSMaxExpr);
3083 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3084 ID.AddPointer(Ops[i]);
3086 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3087 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3088 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3089 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
3091 UniqueSCEVs.InsertNode(S, IP);
3095 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
3097 SmallVector<const SCEV *, 2> Ops;
3100 return getUMaxExpr(Ops);
3104 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3105 assert(!Ops.empty() && "Cannot get empty umax!");
3106 if (Ops.size() == 1) return Ops[0];
3108 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3109 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3110 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
3111 "SCEVUMaxExpr operand types don't match!");
3114 // Sort by complexity, this groups all similar expression types together.
3115 GroupByComplexity(Ops, &LI);
3117 // If there are any constants, fold them together.
3119 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3121 assert(Idx < Ops.size());
3122 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3123 // We found two constants, fold them together!
3124 ConstantInt *Fold = ConstantInt::get(getContext(),
3125 APIntOps::umax(LHSC->getValue()->getValue(),
3126 RHSC->getValue()->getValue()));
3127 Ops[0] = getConstant(Fold);
3128 Ops.erase(Ops.begin()+1); // Erase the folded element
3129 if (Ops.size() == 1) return Ops[0];
3130 LHSC = cast<SCEVConstant>(Ops[0]);
3133 // If we are left with a constant minimum-int, strip it off.
3134 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
3135 Ops.erase(Ops.begin());
3137 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
3138 // If we have an umax with a constant maximum-int, it will always be
3143 if (Ops.size() == 1) return Ops[0];
3146 // Find the first UMax
3147 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
3150 // Check to see if one of the operands is a UMax. If so, expand its operands
3151 // onto our operand list, and recurse to simplify.
3152 if (Idx < Ops.size()) {
3153 bool DeletedUMax = false;
3154 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
3155 Ops.erase(Ops.begin()+Idx);
3156 Ops.append(UMax->op_begin(), UMax->op_end());
3161 return getUMaxExpr(Ops);
3164 // Okay, check to see if the same value occurs in the operand list twice. If
3165 // so, delete one. Since we sorted the list, these values are required to
3167 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3168 // X umax Y umax Y --> X umax Y
3169 // X umax Y --> X, if X is always greater than Y
3170 if (Ops[i] == Ops[i+1] ||
3171 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
3172 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3174 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
3175 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3179 if (Ops.size() == 1) return Ops[0];
3181 assert(!Ops.empty() && "Reduced umax down to nothing!");
3183 // Okay, it looks like we really DO need a umax expr. Check to see if we
3184 // already have one, otherwise create a new one.
3185 FoldingSetNodeID ID;
3186 ID.AddInteger(scUMaxExpr);
3187 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3188 ID.AddPointer(Ops[i]);
3190 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3191 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3192 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3193 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
3195 UniqueSCEVs.InsertNode(S, IP);
3199 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
3201 // ~smax(~x, ~y) == smin(x, y).
3202 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3205 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
3207 // ~umax(~x, ~y) == umin(x, y)
3208 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3211 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
3212 // We can bypass creating a target-independent
3213 // constant expression and then folding it back into a ConstantInt.
3214 // This is just a compile-time optimization.
3215 return getConstant(IntTy,
3216 F.getParent()->getDataLayout().getTypeAllocSize(AllocTy));
3219 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
3222 // We can bypass creating a target-independent
3223 // constant expression and then folding it back into a ConstantInt.
3224 // This is just a compile-time optimization.
3227 F.getParent()->getDataLayout().getStructLayout(STy)->getElementOffset(
3231 const SCEV *ScalarEvolution::getUnknown(Value *V) {
3232 // Don't attempt to do anything other than create a SCEVUnknown object
3233 // here. createSCEV only calls getUnknown after checking for all other
3234 // interesting possibilities, and any other code that calls getUnknown
3235 // is doing so in order to hide a value from SCEV canonicalization.
3237 FoldingSetNodeID ID;
3238 ID.AddInteger(scUnknown);
3241 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3242 assert(cast<SCEVUnknown>(S)->getValue() == V &&
3243 "Stale SCEVUnknown in uniquing map!");
3246 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3248 FirstUnknown = cast<SCEVUnknown>(S);
3249 UniqueSCEVs.InsertNode(S, IP);
3253 //===----------------------------------------------------------------------===//
3254 // Basic SCEV Analysis and PHI Idiom Recognition Code
3257 /// isSCEVable - Test if values of the given type are analyzable within
3258 /// the SCEV framework. This primarily includes integer types, and it
3259 /// can optionally include pointer types if the ScalarEvolution class
3260 /// has access to target-specific information.
3261 bool ScalarEvolution::isSCEVable(Type *Ty) const {
3262 // Integers and pointers are always SCEVable.
3263 return Ty->isIntegerTy() || Ty->isPointerTy();
3266 /// getTypeSizeInBits - Return the size in bits of the specified type,
3267 /// for which isSCEVable must return true.
3268 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3269 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3270 return F.getParent()->getDataLayout().getTypeSizeInBits(Ty);
3273 /// getEffectiveSCEVType - Return a type with the same bitwidth as
3274 /// the given type and which represents how SCEV will treat the given
3275 /// type, for which isSCEVable must return true. For pointer types,
3276 /// this is the pointer-sized integer type.
3277 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3278 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3280 if (Ty->isIntegerTy())
3283 // The only other support type is pointer.
3284 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
3285 return F.getParent()->getDataLayout().getIntPtrType(Ty);
3288 const SCEV *ScalarEvolution::getCouldNotCompute() {
3289 return CouldNotCompute.get();
3293 // Helper class working with SCEVTraversal to figure out if a SCEV contains
3294 // a SCEVUnknown with null value-pointer. FindInvalidSCEVUnknown::FindOne
3295 // is set iff if find such SCEVUnknown.
3297 struct FindInvalidSCEVUnknown {
3299 FindInvalidSCEVUnknown() { FindOne = false; }
3300 bool follow(const SCEV *S) {
3301 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
3305 if (!cast<SCEVUnknown>(S)->getValue())
3312 bool isDone() const { return FindOne; }
3316 bool ScalarEvolution::checkValidity(const SCEV *S) const {
3317 FindInvalidSCEVUnknown F;
3318 SCEVTraversal<FindInvalidSCEVUnknown> ST(F);
3324 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
3325 /// expression and create a new one.
3326 const SCEV *ScalarEvolution::getSCEV(Value *V) {
3327 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3329 const SCEV *S = getExistingSCEV(V);
3332 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
3337 const SCEV *ScalarEvolution::getExistingSCEV(Value *V) {
3338 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3340 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3341 if (I != ValueExprMap.end()) {
3342 const SCEV *S = I->second;
3343 if (checkValidity(S))
3345 ValueExprMap.erase(I);
3350 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
3352 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V,
3353 SCEV::NoWrapFlags Flags) {
3354 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3356 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3358 Type *Ty = V->getType();
3359 Ty = getEffectiveSCEVType(Ty);
3361 V, getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))), Flags);
3364 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
3365 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3366 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3368 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3370 Type *Ty = V->getType();
3371 Ty = getEffectiveSCEVType(Ty);
3372 const SCEV *AllOnes =
3373 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3374 return getMinusSCEV(AllOnes, V);
3377 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
3378 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3379 SCEV::NoWrapFlags Flags) {
3380 // Fast path: X - X --> 0.
3382 return getZero(LHS->getType());
3384 // We represent LHS - RHS as LHS + (-1)*RHS. This transformation
3385 // makes it so that we cannot make much use of NUW.
3386 auto AddFlags = SCEV::FlagAnyWrap;
3387 const bool RHSIsNotMinSigned =
3388 !getSignedRange(RHS).getSignedMin().isMinSignedValue();
3389 if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) {
3390 // Let M be the minimum representable signed value. Then (-1)*RHS
3391 // signed-wraps if and only if RHS is M. That can happen even for
3392 // a NSW subtraction because e.g. (-1)*M signed-wraps even though
3393 // -1 - M does not. So to transfer NSW from LHS - RHS to LHS +
3394 // (-1)*RHS, we need to prove that RHS != M.
3396 // If LHS is non-negative and we know that LHS - RHS does not
3397 // signed-wrap, then RHS cannot be M. So we can rule out signed-wrap
3398 // either by proving that RHS > M or that LHS >= 0.
3399 if (RHSIsNotMinSigned || isKnownNonNegative(LHS)) {
3400 AddFlags = SCEV::FlagNSW;
3404 // FIXME: Find a correct way to transfer NSW to (-1)*M when LHS -
3405 // RHS is NSW and LHS >= 0.
3407 // The difficulty here is that the NSW flag may have been proven
3408 // relative to a loop that is to be found in a recurrence in LHS and
3409 // not in RHS. Applying NSW to (-1)*M may then let the NSW have a
3410 // larger scope than intended.
3411 auto NegFlags = RHSIsNotMinSigned ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3413 return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags);
3416 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
3417 /// input value to the specified type. If the type must be extended, it is zero
3420 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3421 Type *SrcTy = V->getType();
3422 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3423 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3424 "Cannot truncate or zero extend with non-integer arguments!");
3425 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3426 return V; // No conversion
3427 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3428 return getTruncateExpr(V, Ty);
3429 return getZeroExtendExpr(V, Ty);
3432 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
3433 /// input value to the specified type. If the type must be extended, it is sign
3436 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3438 Type *SrcTy = V->getType();
3439 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3440 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3441 "Cannot truncate or zero extend with non-integer arguments!");
3442 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3443 return V; // No conversion
3444 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3445 return getTruncateExpr(V, Ty);
3446 return getSignExtendExpr(V, Ty);
3449 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
3450 /// input value to the specified type. If the type must be extended, it is zero
3451 /// extended. The conversion must not be narrowing.
3453 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3454 Type *SrcTy = V->getType();
3455 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3456 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3457 "Cannot noop or zero extend with non-integer arguments!");
3458 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3459 "getNoopOrZeroExtend cannot truncate!");
3460 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3461 return V; // No conversion
3462 return getZeroExtendExpr(V, Ty);
3465 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
3466 /// input value to the specified type. If the type must be extended, it is sign
3467 /// extended. The conversion must not be narrowing.
3469 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3470 Type *SrcTy = V->getType();
3471 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3472 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3473 "Cannot noop or sign extend with non-integer arguments!");
3474 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3475 "getNoopOrSignExtend cannot truncate!");
3476 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3477 return V; // No conversion
3478 return getSignExtendExpr(V, Ty);
3481 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
3482 /// the input value to the specified type. If the type must be extended,
3483 /// it is extended with unspecified bits. The conversion must not be
3486 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3487 Type *SrcTy = V->getType();
3488 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3489 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3490 "Cannot noop or any extend with non-integer arguments!");
3491 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3492 "getNoopOrAnyExtend cannot truncate!");
3493 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3494 return V; // No conversion
3495 return getAnyExtendExpr(V, Ty);
3498 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
3499 /// input value to the specified type. The conversion must not be widening.
3501 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3502 Type *SrcTy = V->getType();
3503 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3504 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3505 "Cannot truncate or noop with non-integer arguments!");
3506 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
3507 "getTruncateOrNoop cannot extend!");
3508 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3509 return V; // No conversion
3510 return getTruncateExpr(V, Ty);
3513 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
3514 /// the types using zero-extension, and then perform a umax operation
3516 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3518 const SCEV *PromotedLHS = LHS;
3519 const SCEV *PromotedRHS = RHS;
3521 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3522 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3524 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3526 return getUMaxExpr(PromotedLHS, PromotedRHS);
3529 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
3530 /// the types using zero-extension, and then perform a umin operation
3532 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3534 const SCEV *PromotedLHS = LHS;
3535 const SCEV *PromotedRHS = RHS;
3537 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3538 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3540 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3542 return getUMinExpr(PromotedLHS, PromotedRHS);
3545 /// getPointerBase - Transitively follow the chain of pointer-type operands
3546 /// until reaching a SCEV that does not have a single pointer operand. This
3547 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
3548 /// but corner cases do exist.
3549 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3550 // A pointer operand may evaluate to a nonpointer expression, such as null.
3551 if (!V->getType()->isPointerTy())
3554 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3555 return getPointerBase(Cast->getOperand());
3556 } else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3557 const SCEV *PtrOp = nullptr;
3558 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
3560 if ((*I)->getType()->isPointerTy()) {
3561 // Cannot find the base of an expression with multiple pointer operands.
3569 return getPointerBase(PtrOp);
3574 /// PushDefUseChildren - Push users of the given Instruction
3575 /// onto the given Worklist.
3577 PushDefUseChildren(Instruction *I,
3578 SmallVectorImpl<Instruction *> &Worklist) {
3579 // Push the def-use children onto the Worklist stack.
3580 for (User *U : I->users())
3581 Worklist.push_back(cast<Instruction>(U));
3584 /// ForgetSymbolicValue - This looks up computed SCEV values for all
3585 /// instructions that depend on the given instruction and removes them from
3586 /// the ValueExprMapType map if they reference SymName. This is used during PHI
3589 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3590 SmallVector<Instruction *, 16> Worklist;
3591 PushDefUseChildren(PN, Worklist);
3593 SmallPtrSet<Instruction *, 8> Visited;
3595 while (!Worklist.empty()) {
3596 Instruction *I = Worklist.pop_back_val();
3597 if (!Visited.insert(I).second)
3600 auto It = ValueExprMap.find_as(static_cast<Value *>(I));
3601 if (It != ValueExprMap.end()) {
3602 const SCEV *Old = It->second;
3604 // Short-circuit the def-use traversal if the symbolic name
3605 // ceases to appear in expressions.
3606 if (Old != SymName && !hasOperand(Old, SymName))
3609 // SCEVUnknown for a PHI either means that it has an unrecognized
3610 // structure, it's a PHI that's in the progress of being computed
3611 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3612 // additional loop trip count information isn't going to change anything.
3613 // In the second case, createNodeForPHI will perform the necessary
3614 // updates on its own when it gets to that point. In the third, we do
3615 // want to forget the SCEVUnknown.
3616 if (!isa<PHINode>(I) ||
3617 !isa<SCEVUnknown>(Old) ||
3618 (I != PN && Old == SymName)) {
3619 forgetMemoizedResults(Old);
3620 ValueExprMap.erase(It);
3624 PushDefUseChildren(I, Worklist);
3628 const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
3629 const Loop *L = LI.getLoopFor(PN->getParent());
3630 if (!L || L->getHeader() != PN->getParent())
3633 // The loop may have multiple entrances or multiple exits; we can analyze
3634 // this phi as an addrec if it has a unique entry value and a unique
3636 Value *BEValueV = nullptr, *StartValueV = nullptr;
3637 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
3638 Value *V = PN->getIncomingValue(i);
3639 if (L->contains(PN->getIncomingBlock(i))) {
3642 } else if (BEValueV != V) {
3646 } else if (!StartValueV) {
3648 } else if (StartValueV != V) {
3649 StartValueV = nullptr;
3653 if (BEValueV && StartValueV) {
3654 // While we are analyzing this PHI node, handle its value symbolically.
3655 const SCEV *SymbolicName = getUnknown(PN);
3656 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&
3657 "PHI node already processed?");
3658 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
3660 // Using this symbolic name for the PHI, analyze the value coming around
3662 const SCEV *BEValue = getSCEV(BEValueV);
3664 // NOTE: If BEValue is loop invariant, we know that the PHI node just
3665 // has a special value for the first iteration of the loop.
3667 // If the value coming around the backedge is an add with the symbolic
3668 // value we just inserted, then we found a simple induction variable!
3669 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
3670 // If there is a single occurrence of the symbolic value, replace it
3671 // with a recurrence.
3672 unsigned FoundIndex = Add->getNumOperands();
3673 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3674 if (Add->getOperand(i) == SymbolicName)
3675 if (FoundIndex == e) {
3680 if (FoundIndex != Add->getNumOperands()) {
3681 // Create an add with everything but the specified operand.
3682 SmallVector<const SCEV *, 8> Ops;
3683 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3684 if (i != FoundIndex)
3685 Ops.push_back(Add->getOperand(i));
3686 const SCEV *Accum = getAddExpr(Ops);
3688 // This is not a valid addrec if the step amount is varying each
3689 // loop iteration, but is not itself an addrec in this loop.
3690 if (isLoopInvariant(Accum, L) ||
3691 (isa<SCEVAddRecExpr>(Accum) &&
3692 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
3693 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3695 // If the increment doesn't overflow, then neither the addrec nor
3696 // the post-increment will overflow.
3697 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
3698 if (OBO->getOperand(0) == PN) {
3699 if (OBO->hasNoUnsignedWrap())
3700 Flags = setFlags(Flags, SCEV::FlagNUW);
3701 if (OBO->hasNoSignedWrap())
3702 Flags = setFlags(Flags, SCEV::FlagNSW);
3704 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
3705 // If the increment is an inbounds GEP, then we know the address
3706 // space cannot be wrapped around. We cannot make any guarantee
3707 // about signed or unsigned overflow because pointers are
3708 // unsigned but we may have a negative index from the base
3709 // pointer. We can guarantee that no unsigned wrap occurs if the
3710 // indices form a positive value.
3711 if (GEP->isInBounds() && GEP->getOperand(0) == PN) {
3712 Flags = setFlags(Flags, SCEV::FlagNW);
3714 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
3715 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
3716 Flags = setFlags(Flags, SCEV::FlagNUW);
3719 // We cannot transfer nuw and nsw flags from subtraction
3720 // operations -- sub nuw X, Y is not the same as add nuw X, -Y
3724 const SCEV *StartVal = getSCEV(StartValueV);
3725 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
3727 // Since the no-wrap flags are on the increment, they apply to the
3728 // post-incremented value as well.
3729 if (isLoopInvariant(Accum, L))
3730 (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
3732 // Okay, for the entire analysis of this edge we assumed the PHI
3733 // to be symbolic. We now need to go back and purge all of the
3734 // entries for the scalars that use the symbolic expression.
3735 ForgetSymbolicName(PN, SymbolicName);
3736 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3740 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(BEValue)) {
3741 // Otherwise, this could be a loop like this:
3742 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
3743 // In this case, j = {1,+,1} and BEValue is j.
3744 // Because the other in-value of i (0) fits the evolution of BEValue
3745 // i really is an addrec evolution.
3746 if (AddRec->getLoop() == L && AddRec->isAffine()) {
3747 const SCEV *StartVal = getSCEV(StartValueV);
3749 // If StartVal = j.start - j.stride, we can use StartVal as the
3750 // initial step of the addrec evolution.
3752 getMinusSCEV(AddRec->getOperand(0), AddRec->getOperand(1))) {
3753 // FIXME: For constant StartVal, we should be able to infer
3755 const SCEV *PHISCEV = getAddRecExpr(StartVal, AddRec->getOperand(1),
3756 L, SCEV::FlagAnyWrap);
3758 // Okay, for the entire analysis of this edge we assumed the PHI
3759 // to be symbolic. We now need to go back and purge all of the
3760 // entries for the scalars that use the symbolic expression.
3761 ForgetSymbolicName(PN, SymbolicName);
3762 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3772 // Checks if the SCEV S is available at BB. S is considered available at BB
3773 // if S can be materialized at BB without introducing a fault.
3774 static bool IsAvailableOnEntry(const Loop *L, DominatorTree &DT, const SCEV *S,
3776 struct CheckAvailable {
3777 bool TraversalDone = false;
3778 bool Available = true;
3780 const Loop *L = nullptr; // The loop BB is in (can be nullptr)
3781 BasicBlock *BB = nullptr;
3784 CheckAvailable(const Loop *L, BasicBlock *BB, DominatorTree &DT)
3785 : L(L), BB(BB), DT(DT) {}
3787 bool setUnavailable() {
3788 TraversalDone = true;
3793 bool follow(const SCEV *S) {
3794 switch (S->getSCEVType()) {
3795 case scConstant: case scTruncate: case scZeroExtend: case scSignExtend:
3796 case scAddExpr: case scMulExpr: case scUMaxExpr: case scSMaxExpr:
3797 // These expressions are available if their operand(s) is/are.
3800 case scAddRecExpr: {
3801 // We allow add recurrences that are on the loop BB is in, or some
3802 // outer loop. This guarantees availability because the value of the
3803 // add recurrence at BB is simply the "current" value of the induction
3804 // variable. We can relax this in the future; for instance an add
3805 // recurrence on a sibling dominating loop is also available at BB.
3806 const auto *ARLoop = cast<SCEVAddRecExpr>(S)->getLoop();
3807 if (L && (ARLoop == L || ARLoop->contains(L)))
3810 return setUnavailable();
3814 // For SCEVUnknown, we check for simple dominance.
3815 const auto *SU = cast<SCEVUnknown>(S);
3816 Value *V = SU->getValue();
3818 if (isa<Argument>(V))
3821 if (isa<Instruction>(V) && DT.dominates(cast<Instruction>(V), BB))
3824 return setUnavailable();
3828 case scCouldNotCompute:
3829 // We do not try to smart about these at all.
3830 return setUnavailable();
3832 llvm_unreachable("switch should be fully covered!");
3835 bool isDone() { return TraversalDone; }
3838 CheckAvailable CA(L, BB, DT);
3839 SCEVTraversal<CheckAvailable> ST(CA);
3842 return CA.Available;
3845 // Try to match a control flow sequence that branches out at BI and merges back
3846 // at Merge into a "C ? LHS : RHS" select pattern. Return true on a successful
3848 static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge,
3849 Value *&C, Value *&LHS, Value *&RHS) {
3850 C = BI->getCondition();
3852 BasicBlockEdge LeftEdge(BI->getParent(), BI->getSuccessor(0));
3853 BasicBlockEdge RightEdge(BI->getParent(), BI->getSuccessor(1));
3855 if (!LeftEdge.isSingleEdge())
3858 assert(RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()");
3860 Use &LeftUse = Merge->getOperandUse(0);
3861 Use &RightUse = Merge->getOperandUse(1);
3863 if (DT.dominates(LeftEdge, LeftUse) && DT.dominates(RightEdge, RightUse)) {
3869 if (DT.dominates(LeftEdge, RightUse) && DT.dominates(RightEdge, LeftUse)) {
3878 const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
3879 if (PN->getNumIncomingValues() == 2) {
3880 const Loop *L = LI.getLoopFor(PN->getParent());
3884 // br %cond, label %left, label %right
3890 // V = phi [ %x, %left ], [ %y, %right ]
3892 // as "select %cond, %x, %y"
3894 BasicBlock *IDom = DT[PN->getParent()]->getIDom()->getBlock();
3895 assert(IDom && "At least the entry block should dominate PN");
3897 auto *BI = dyn_cast<BranchInst>(IDom->getTerminator());
3898 Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr;
3900 if (BI && BI->isConditional() &&
3901 BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
3902 IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
3903 IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent()))
3904 return createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
3910 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
3911 if (const SCEV *S = createAddRecFromPHI(PN))
3914 if (const SCEV *S = createNodeFromSelectLikePHI(PN))
3917 // If the PHI has a single incoming value, follow that value, unless the
3918 // PHI's incoming blocks are in a different loop, in which case doing so
3919 // risks breaking LCSSA form. Instcombine would normally zap these, but
3920 // it doesn't have DominatorTree information, so it may miss cases.
3921 if (Value *V = SimplifyInstruction(PN, F.getParent()->getDataLayout(), &TLI,
3923 if (LI.replacementPreservesLCSSAForm(PN, V))
3926 // If it's not a loop phi, we can't handle it yet.
3927 return getUnknown(PN);
3930 const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
3934 // Handle "constant" branch or select. This can occur for instance when a
3935 // loop pass transforms an inner loop and moves on to process the outer loop.
3936 if (auto *CI = dyn_cast<ConstantInt>(Cond))
3937 return getSCEV(CI->isOne() ? TrueVal : FalseVal);
3939 // Try to match some simple smax or umax patterns.
3940 auto *ICI = dyn_cast<ICmpInst>(Cond);
3942 return getUnknown(I);
3944 Value *LHS = ICI->getOperand(0);
3945 Value *RHS = ICI->getOperand(1);
3947 switch (ICI->getPredicate()) {
3948 case ICmpInst::ICMP_SLT:
3949 case ICmpInst::ICMP_SLE:
3950 std::swap(LHS, RHS);
3952 case ICmpInst::ICMP_SGT:
3953 case ICmpInst::ICMP_SGE:
3954 // a >s b ? a+x : b+x -> smax(a, b)+x
3955 // a >s b ? b+x : a+x -> smin(a, b)+x
3956 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
3957 const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), I->getType());
3958 const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), I->getType());
3959 const SCEV *LA = getSCEV(TrueVal);
3960 const SCEV *RA = getSCEV(FalseVal);
3961 const SCEV *LDiff = getMinusSCEV(LA, LS);
3962 const SCEV *RDiff = getMinusSCEV(RA, RS);
3964 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3965 LDiff = getMinusSCEV(LA, RS);
3966 RDiff = getMinusSCEV(RA, LS);
3968 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3971 case ICmpInst::ICMP_ULT:
3972 case ICmpInst::ICMP_ULE:
3973 std::swap(LHS, RHS);
3975 case ICmpInst::ICMP_UGT:
3976 case ICmpInst::ICMP_UGE:
3977 // a >u b ? a+x : b+x -> umax(a, b)+x
3978 // a >u b ? b+x : a+x -> umin(a, b)+x
3979 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
3980 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
3981 const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), I->getType());
3982 const SCEV *LA = getSCEV(TrueVal);
3983 const SCEV *RA = getSCEV(FalseVal);
3984 const SCEV *LDiff = getMinusSCEV(LA, LS);
3985 const SCEV *RDiff = getMinusSCEV(RA, RS);
3987 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3988 LDiff = getMinusSCEV(LA, RS);
3989 RDiff = getMinusSCEV(RA, LS);
3991 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3994 case ICmpInst::ICMP_NE:
3995 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3996 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
3997 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
3998 const SCEV *One = getOne(I->getType());
3999 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4000 const SCEV *LA = getSCEV(TrueVal);
4001 const SCEV *RA = getSCEV(FalseVal);
4002 const SCEV *LDiff = getMinusSCEV(LA, LS);
4003 const SCEV *RDiff = getMinusSCEV(RA, One);
4005 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4008 case ICmpInst::ICMP_EQ:
4009 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4010 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4011 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4012 const SCEV *One = getOne(I->getType());
4013 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4014 const SCEV *LA = getSCEV(TrueVal);
4015 const SCEV *RA = getSCEV(FalseVal);
4016 const SCEV *LDiff = getMinusSCEV(LA, One);
4017 const SCEV *RDiff = getMinusSCEV(RA, LS);
4019 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4026 return getUnknown(I);
4029 /// createNodeForGEP - Expand GEP instructions into add and multiply
4030 /// operations. This allows them to be analyzed by regular SCEV code.
4032 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
4033 Value *Base = GEP->getOperand(0);
4034 // Don't attempt to analyze GEPs over unsized objects.
4035 if (!Base->getType()->getPointerElementType()->isSized())
4036 return getUnknown(GEP);
4038 SmallVector<const SCEV *, 4> IndexExprs;
4039 for (auto Index = GEP->idx_begin(); Index != GEP->idx_end(); ++Index)
4040 IndexExprs.push_back(getSCEV(*Index));
4041 return getGEPExpr(GEP->getSourceElementType(), getSCEV(Base), IndexExprs,
4045 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
4046 /// guaranteed to end in (at every loop iteration). It is, at the same time,
4047 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
4048 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
4050 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
4051 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4052 return C->getValue()->getValue().countTrailingZeros();
4054 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
4055 return std::min(GetMinTrailingZeros(T->getOperand()),
4056 (uint32_t)getTypeSizeInBits(T->getType()));
4058 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
4059 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4060 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
4061 getTypeSizeInBits(E->getType()) : OpRes;
4064 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
4065 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4066 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
4067 getTypeSizeInBits(E->getType()) : OpRes;
4070 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
4071 // The result is the min of all operands results.
4072 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4073 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4074 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4078 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
4079 // The result is the sum of all operands results.
4080 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
4081 uint32_t BitWidth = getTypeSizeInBits(M->getType());
4082 for (unsigned i = 1, e = M->getNumOperands();
4083 SumOpRes != BitWidth && i != e; ++i)
4084 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
4089 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
4090 // The result is the min of all operands results.
4091 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4092 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4093 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4097 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
4098 // The result is the min of all operands results.
4099 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4100 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4101 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4105 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
4106 // The result is the min of all operands results.
4107 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4108 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4109 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4113 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4114 // For a SCEVUnknown, ask ValueTracking.
4115 unsigned BitWidth = getTypeSizeInBits(U->getType());
4116 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4117 computeKnownBits(U->getValue(), Zeros, Ones, F.getParent()->getDataLayout(),
4118 0, &AC, nullptr, &DT);
4119 return Zeros.countTrailingOnes();
4126 /// GetRangeFromMetadata - Helper method to assign a range to V from
4127 /// metadata present in the IR.
4128 static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
4129 if (Instruction *I = dyn_cast<Instruction>(V))
4130 if (MDNode *MD = I->getMetadata(LLVMContext::MD_range))
4131 return getConstantRangeFromMetadata(*MD);
4136 /// getRange - Determine the range for a particular SCEV. If SignHint is
4137 /// HINT_RANGE_UNSIGNED (resp. HINT_RANGE_SIGNED) then getRange prefers ranges
4138 /// with a "cleaner" unsigned (resp. signed) representation.
4141 ScalarEvolution::getRange(const SCEV *S,
4142 ScalarEvolution::RangeSignHint SignHint) {
4143 DenseMap<const SCEV *, ConstantRange> &Cache =
4144 SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED ? UnsignedRanges
4147 // See if we've computed this range already.
4148 DenseMap<const SCEV *, ConstantRange>::iterator I = Cache.find(S);
4149 if (I != Cache.end())
4152 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4153 return setRange(C, SignHint, ConstantRange(C->getValue()->getValue()));
4155 unsigned BitWidth = getTypeSizeInBits(S->getType());
4156 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
4158 // If the value has known zeros, the maximum value will have those known zeros
4160 uint32_t TZ = GetMinTrailingZeros(S);
4162 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED)
4163 ConservativeResult =
4164 ConstantRange(APInt::getMinValue(BitWidth),
4165 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
4167 ConservativeResult = ConstantRange(
4168 APInt::getSignedMinValue(BitWidth),
4169 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
4172 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
4173 ConstantRange X = getRange(Add->getOperand(0), SignHint);
4174 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
4175 X = X.add(getRange(Add->getOperand(i), SignHint));
4176 return setRange(Add, SignHint, ConservativeResult.intersectWith(X));
4179 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
4180 ConstantRange X = getRange(Mul->getOperand(0), SignHint);
4181 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
4182 X = X.multiply(getRange(Mul->getOperand(i), SignHint));
4183 return setRange(Mul, SignHint, ConservativeResult.intersectWith(X));
4186 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
4187 ConstantRange X = getRange(SMax->getOperand(0), SignHint);
4188 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
4189 X = X.smax(getRange(SMax->getOperand(i), SignHint));
4190 return setRange(SMax, SignHint, ConservativeResult.intersectWith(X));
4193 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
4194 ConstantRange X = getRange(UMax->getOperand(0), SignHint);
4195 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
4196 X = X.umax(getRange(UMax->getOperand(i), SignHint));
4197 return setRange(UMax, SignHint, ConservativeResult.intersectWith(X));
4200 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
4201 ConstantRange X = getRange(UDiv->getLHS(), SignHint);
4202 ConstantRange Y = getRange(UDiv->getRHS(), SignHint);
4203 return setRange(UDiv, SignHint,
4204 ConservativeResult.intersectWith(X.udiv(Y)));
4207 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
4208 ConstantRange X = getRange(ZExt->getOperand(), SignHint);
4209 return setRange(ZExt, SignHint,
4210 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
4213 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
4214 ConstantRange X = getRange(SExt->getOperand(), SignHint);
4215 return setRange(SExt, SignHint,
4216 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
4219 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
4220 ConstantRange X = getRange(Trunc->getOperand(), SignHint);
4221 return setRange(Trunc, SignHint,
4222 ConservativeResult.intersectWith(X.truncate(BitWidth)));
4225 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
4226 // If there's no unsigned wrap, the value will never be less than its
4228 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
4229 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
4230 if (!C->getValue()->isZero())
4231 ConservativeResult =
4232 ConservativeResult.intersectWith(
4233 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
4235 // If there's no signed wrap, and all the operands have the same sign or
4236 // zero, the value won't ever change sign.
4237 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
4238 bool AllNonNeg = true;
4239 bool AllNonPos = true;
4240 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4241 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
4242 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
4245 ConservativeResult = ConservativeResult.intersectWith(
4246 ConstantRange(APInt(BitWidth, 0),
4247 APInt::getSignedMinValue(BitWidth)));
4249 ConservativeResult = ConservativeResult.intersectWith(
4250 ConstantRange(APInt::getSignedMinValue(BitWidth),
4251 APInt(BitWidth, 1)));
4254 // TODO: non-affine addrec
4255 if (AddRec->isAffine()) {
4256 Type *Ty = AddRec->getType();
4257 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
4258 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
4259 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
4261 // Check for overflow. This must be done with ConstantRange arithmetic
4262 // because we could be called from within the ScalarEvolution overflow
4265 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
4266 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
4267 ConstantRange ZExtMaxBECountRange =
4268 MaxBECountRange.zextOrTrunc(BitWidth * 2 + 1);
4270 const SCEV *Start = AddRec->getStart();
4271 const SCEV *Step = AddRec->getStepRecurrence(*this);
4272 ConstantRange StepSRange = getSignedRange(Step);
4273 ConstantRange SExtStepSRange = StepSRange.sextOrTrunc(BitWidth * 2 + 1);
4275 ConstantRange StartURange = getUnsignedRange(Start);
4276 ConstantRange EndURange =
4277 StartURange.add(MaxBECountRange.multiply(StepSRange));
4279 // Check for unsigned overflow.
4280 ConstantRange ZExtStartURange =
4281 StartURange.zextOrTrunc(BitWidth * 2 + 1);
4282 ConstantRange ZExtEndURange = EndURange.zextOrTrunc(BitWidth * 2 + 1);
4283 if (ZExtStartURange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
4285 APInt Min = APIntOps::umin(StartURange.getUnsignedMin(),
4286 EndURange.getUnsignedMin());
4287 APInt Max = APIntOps::umax(StartURange.getUnsignedMax(),
4288 EndURange.getUnsignedMax());
4289 bool IsFullRange = Min.isMinValue() && Max.isMaxValue();
4291 ConservativeResult =
4292 ConservativeResult.intersectWith(ConstantRange(Min, Max + 1));
4295 ConstantRange StartSRange = getSignedRange(Start);
4296 ConstantRange EndSRange =
4297 StartSRange.add(MaxBECountRange.multiply(StepSRange));
4299 // Check for signed overflow. This must be done with ConstantRange
4300 // arithmetic because we could be called from within the ScalarEvolution
4301 // overflow checking code.
4302 ConstantRange SExtStartSRange =
4303 StartSRange.sextOrTrunc(BitWidth * 2 + 1);
4304 ConstantRange SExtEndSRange = EndSRange.sextOrTrunc(BitWidth * 2 + 1);
4305 if (SExtStartSRange.add(ZExtMaxBECountRange.multiply(SExtStepSRange)) ==
4307 APInt Min = APIntOps::smin(StartSRange.getSignedMin(),
4308 EndSRange.getSignedMin());
4309 APInt Max = APIntOps::smax(StartSRange.getSignedMax(),
4310 EndSRange.getSignedMax());
4311 bool IsFullRange = Min.isMinSignedValue() && Max.isMaxSignedValue();
4313 ConservativeResult =
4314 ConservativeResult.intersectWith(ConstantRange(Min, Max + 1));
4319 return setRange(AddRec, SignHint, ConservativeResult);
4322 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4323 // Check if the IR explicitly contains !range metadata.
4324 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
4325 if (MDRange.hasValue())
4326 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
4328 // Split here to avoid paying the compile-time cost of calling both
4329 // computeKnownBits and ComputeNumSignBits. This restriction can be lifted
4331 const DataLayout &DL = F.getParent()->getDataLayout();
4332 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) {
4333 // For a SCEVUnknown, ask ValueTracking.
4334 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4335 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, &AC, nullptr, &DT);
4336 if (Ones != ~Zeros + 1)
4337 ConservativeResult =
4338 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
4340 assert(SignHint == ScalarEvolution::HINT_RANGE_SIGNED &&
4341 "generalize as needed!");
4342 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
4344 ConservativeResult = ConservativeResult.intersectWith(
4345 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
4346 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1) + 1));
4349 return setRange(U, SignHint, ConservativeResult);
4352 return setRange(S, SignHint, ConservativeResult);
4355 SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) {
4356 if (isa<ConstantExpr>(V)) return SCEV::FlagAnyWrap;
4357 const BinaryOperator *BinOp = cast<BinaryOperator>(V);
4359 // Return early if there are no flags to propagate to the SCEV.
4360 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
4361 if (BinOp->hasNoUnsignedWrap())
4362 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
4363 if (BinOp->hasNoSignedWrap())
4364 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
4365 if (Flags == SCEV::FlagAnyWrap) {
4366 return SCEV::FlagAnyWrap;
4369 // Here we check that BinOp is in the header of the innermost loop
4370 // containing BinOp, since we only deal with instructions in the loop
4371 // header. The actual loop we need to check later will come from an add
4372 // recurrence, but getting that requires computing the SCEV of the operands,
4373 // which can be expensive. This check we can do cheaply to rule out some
4375 Loop *innermostContainingLoop = LI.getLoopFor(BinOp->getParent());
4376 if (innermostContainingLoop == nullptr ||
4377 innermostContainingLoop->getHeader() != BinOp->getParent())
4378 return SCEV::FlagAnyWrap;
4380 // Only proceed if we can prove that BinOp does not yield poison.
4381 if (!isKnownNotFullPoison(BinOp)) return SCEV::FlagAnyWrap;
4383 // At this point we know that if V is executed, then it does not wrap
4384 // according to at least one of NSW or NUW. If V is not executed, then we do
4385 // not know if the calculation that V represents would wrap. Multiple
4386 // instructions can map to the same SCEV. If we apply NSW or NUW from V to
4387 // the SCEV, we must guarantee no wrapping for that SCEV also when it is
4388 // derived from other instructions that map to the same SCEV. We cannot make
4389 // that guarantee for cases where V is not executed. So we need to find the
4390 // loop that V is considered in relation to and prove that V is executed for
4391 // every iteration of that loop. That implies that the value that V
4392 // calculates does not wrap anywhere in the loop, so then we can apply the
4393 // flags to the SCEV.
4395 // We check isLoopInvariant to disambiguate in case we are adding two
4396 // recurrences from different loops, so that we know which loop to prove
4397 // that V is executed in.
4398 for (int OpIndex = 0; OpIndex < 2; ++OpIndex) {
4399 const SCEV *Op = getSCEV(BinOp->getOperand(OpIndex));
4400 if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
4401 const int OtherOpIndex = 1 - OpIndex;
4402 const SCEV *OtherOp = getSCEV(BinOp->getOperand(OtherOpIndex));
4403 if (isLoopInvariant(OtherOp, AddRec->getLoop()) &&
4404 isGuaranteedToExecuteForEveryIteration(BinOp, AddRec->getLoop()))
4408 return SCEV::FlagAnyWrap;
4411 /// createSCEV - We know that there is no SCEV for the specified value. Analyze
4414 const SCEV *ScalarEvolution::createSCEV(Value *V) {
4415 if (!isSCEVable(V->getType()))
4416 return getUnknown(V);
4418 unsigned Opcode = Instruction::UserOp1;
4419 if (Instruction *I = dyn_cast<Instruction>(V)) {
4420 Opcode = I->getOpcode();
4422 // Don't attempt to analyze instructions in blocks that aren't
4423 // reachable. Such instructions don't matter, and they aren't required
4424 // to obey basic rules for definitions dominating uses which this
4425 // analysis depends on.
4426 if (!DT.isReachableFromEntry(I->getParent()))
4427 return getUnknown(V);
4428 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
4429 Opcode = CE->getOpcode();
4430 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
4431 return getConstant(CI);
4432 else if (isa<ConstantPointerNull>(V))
4433 return getZero(V->getType());
4434 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
4435 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
4437 return getUnknown(V);
4439 Operator *U = cast<Operator>(V);
4441 case Instruction::Add: {
4442 // The simple thing to do would be to just call getSCEV on both operands
4443 // and call getAddExpr with the result. However if we're looking at a
4444 // bunch of things all added together, this can be quite inefficient,
4445 // because it leads to N-1 getAddExpr calls for N ultimate operands.
4446 // Instead, gather up all the operands and make a single getAddExpr call.
4447 // LLVM IR canonical form means we need only traverse the left operands.
4448 SmallVector<const SCEV *, 4> AddOps;
4449 for (Value *Op = U;; Op = U->getOperand(0)) {
4450 U = dyn_cast<Operator>(Op);
4451 unsigned Opcode = U ? U->getOpcode() : 0;
4452 if (!U || (Opcode != Instruction::Add && Opcode != Instruction::Sub)) {
4453 assert(Op != V && "V should be an add");
4454 AddOps.push_back(getSCEV(Op));
4458 if (auto *OpSCEV = getExistingSCEV(U)) {
4459 AddOps.push_back(OpSCEV);
4463 // If a NUW or NSW flag can be applied to the SCEV for this
4464 // addition, then compute the SCEV for this addition by itself
4465 // with a separate call to getAddExpr. We need to do that
4466 // instead of pushing the operands of the addition onto AddOps,
4467 // since the flags are only known to apply to this particular
4468 // addition - they may not apply to other additions that can be
4469 // formed with operands from AddOps.
4470 const SCEV *RHS = getSCEV(U->getOperand(1));
4471 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(U);
4472 if (Flags != SCEV::FlagAnyWrap) {
4473 const SCEV *LHS = getSCEV(U->getOperand(0));
4474 if (Opcode == Instruction::Sub)
4475 AddOps.push_back(getMinusSCEV(LHS, RHS, Flags));
4477 AddOps.push_back(getAddExpr(LHS, RHS, Flags));
4481 if (Opcode == Instruction::Sub)
4482 AddOps.push_back(getNegativeSCEV(RHS));
4484 AddOps.push_back(RHS);
4486 return getAddExpr(AddOps);
4489 case Instruction::Mul: {
4490 SmallVector<const SCEV *, 4> MulOps;
4491 for (Value *Op = U;; Op = U->getOperand(0)) {
4492 U = dyn_cast<Operator>(Op);
4493 if (!U || U->getOpcode() != Instruction::Mul) {
4494 assert(Op != V && "V should be a mul");
4495 MulOps.push_back(getSCEV(Op));
4499 if (auto *OpSCEV = getExistingSCEV(U)) {
4500 MulOps.push_back(OpSCEV);
4504 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(U);
4505 if (Flags != SCEV::FlagAnyWrap) {
4506 MulOps.push_back(getMulExpr(getSCEV(U->getOperand(0)),
4507 getSCEV(U->getOperand(1)), Flags));
4511 MulOps.push_back(getSCEV(U->getOperand(1)));
4513 return getMulExpr(MulOps);
4515 case Instruction::UDiv:
4516 return getUDivExpr(getSCEV(U->getOperand(0)),
4517 getSCEV(U->getOperand(1)));
4518 case Instruction::Sub:
4519 return getMinusSCEV(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)),
4520 getNoWrapFlagsFromUB(U));
4521 case Instruction::And:
4522 // For an expression like x&255 that merely masks off the high bits,
4523 // use zext(trunc(x)) as the SCEV expression.
4524 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4525 if (CI->isNullValue())
4526 return getSCEV(U->getOperand(1));
4527 if (CI->isAllOnesValue())
4528 return getSCEV(U->getOperand(0));
4529 const APInt &A = CI->getValue();
4531 // Instcombine's ShrinkDemandedConstant may strip bits out of
4532 // constants, obscuring what would otherwise be a low-bits mask.
4533 // Use computeKnownBits to compute what ShrinkDemandedConstant
4534 // knew about to reconstruct a low-bits mask value.
4535 unsigned LZ = A.countLeadingZeros();
4536 unsigned TZ = A.countTrailingZeros();
4537 unsigned BitWidth = A.getBitWidth();
4538 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4539 computeKnownBits(U->getOperand(0), KnownZero, KnownOne,
4540 F.getParent()->getDataLayout(), 0, &AC, nullptr, &DT);
4542 APInt EffectiveMask =
4543 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
4544 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
4545 const SCEV *MulCount = getConstant(
4546 ConstantInt::get(getContext(), APInt::getOneBitSet(BitWidth, TZ)));
4550 getUDivExactExpr(getSCEV(U->getOperand(0)), MulCount),
4551 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
4558 case Instruction::Or:
4559 // If the RHS of the Or is a constant, we may have something like:
4560 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
4561 // optimizations will transparently handle this case.
4563 // In order for this transformation to be safe, the LHS must be of the
4564 // form X*(2^n) and the Or constant must be less than 2^n.
4565 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4566 const SCEV *LHS = getSCEV(U->getOperand(0));
4567 const APInt &CIVal = CI->getValue();
4568 if (GetMinTrailingZeros(LHS) >=
4569 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
4570 // Build a plain add SCEV.
4571 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
4572 // If the LHS of the add was an addrec and it has no-wrap flags,
4573 // transfer the no-wrap flags, since an or won't introduce a wrap.
4574 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
4575 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
4576 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
4577 OldAR->getNoWrapFlags());
4583 case Instruction::Xor:
4584 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4585 // If the RHS of the xor is a signbit, then this is just an add.
4586 // Instcombine turns add of signbit into xor as a strength reduction step.
4587 if (CI->getValue().isSignBit())
4588 return getAddExpr(getSCEV(U->getOperand(0)),
4589 getSCEV(U->getOperand(1)));
4591 // If the RHS of xor is -1, then this is a not operation.
4592 if (CI->isAllOnesValue())
4593 return getNotSCEV(getSCEV(U->getOperand(0)));
4595 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
4596 // This is a variant of the check for xor with -1, and it handles
4597 // the case where instcombine has trimmed non-demanded bits out
4598 // of an xor with -1.
4599 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
4600 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
4601 if (BO->getOpcode() == Instruction::And &&
4602 LCI->getValue() == CI->getValue())
4603 if (const SCEVZeroExtendExpr *Z =
4604 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
4605 Type *UTy = U->getType();
4606 const SCEV *Z0 = Z->getOperand();
4607 Type *Z0Ty = Z0->getType();
4608 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
4610 // If C is a low-bits mask, the zero extend is serving to
4611 // mask off the high bits. Complement the operand and
4612 // re-apply the zext.
4613 if (APIntOps::isMask(Z0TySize, CI->getValue()))
4614 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
4616 // If C is a single bit, it may be in the sign-bit position
4617 // before the zero-extend. In this case, represent the xor
4618 // using an add, which is equivalent, and re-apply the zext.
4619 APInt Trunc = CI->getValue().trunc(Z0TySize);
4620 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
4622 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
4628 case Instruction::Shl:
4629 // Turn shift left of a constant amount into a multiply.
4630 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4631 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4633 // If the shift count is not less than the bitwidth, the result of
4634 // the shift is undefined. Don't try to analyze it, because the
4635 // resolution chosen here may differ from the resolution chosen in
4636 // other parts of the compiler.
4637 if (SA->getValue().uge(BitWidth))
4640 // It is currently not resolved how to interpret NSW for left
4641 // shift by BitWidth - 1, so we avoid applying flags in that
4642 // case. Remove this check (or this comment) once the situation
4644 // http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html
4645 // and http://reviews.llvm.org/D8890 .
4646 auto Flags = SCEV::FlagAnyWrap;
4647 if (SA->getValue().ult(BitWidth - 1)) Flags = getNoWrapFlagsFromUB(U);
4649 Constant *X = ConstantInt::get(getContext(),
4650 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4651 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X), Flags);
4655 case Instruction::LShr:
4656 // Turn logical shift right of a constant into a unsigned divide.
4657 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4658 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4660 // If the shift count is not less than the bitwidth, the result of
4661 // the shift is undefined. Don't try to analyze it, because the
4662 // resolution chosen here may differ from the resolution chosen in
4663 // other parts of the compiler.
4664 if (SA->getValue().uge(BitWidth))
4667 Constant *X = ConstantInt::get(getContext(),
4668 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4669 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4673 case Instruction::AShr:
4674 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
4675 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
4676 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
4677 if (L->getOpcode() == Instruction::Shl &&
4678 L->getOperand(1) == U->getOperand(1)) {
4679 uint64_t BitWidth = getTypeSizeInBits(U->getType());
4681 // If the shift count is not less than the bitwidth, the result of
4682 // the shift is undefined. Don't try to analyze it, because the
4683 // resolution chosen here may differ from the resolution chosen in
4684 // other parts of the compiler.
4685 if (CI->getValue().uge(BitWidth))
4688 uint64_t Amt = BitWidth - CI->getZExtValue();
4689 if (Amt == BitWidth)
4690 return getSCEV(L->getOperand(0)); // shift by zero --> noop
4692 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
4693 IntegerType::get(getContext(),
4699 case Instruction::Trunc:
4700 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
4702 case Instruction::ZExt:
4703 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4705 case Instruction::SExt:
4706 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4708 case Instruction::BitCast:
4709 // BitCasts are no-op casts so we just eliminate the cast.
4710 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
4711 return getSCEV(U->getOperand(0));
4714 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
4715 // lead to pointer expressions which cannot safely be expanded to GEPs,
4716 // because ScalarEvolution doesn't respect the GEP aliasing rules when
4717 // simplifying integer expressions.
4719 case Instruction::GetElementPtr:
4720 return createNodeForGEP(cast<GEPOperator>(U));
4722 case Instruction::PHI:
4723 return createNodeForPHI(cast<PHINode>(U));
4725 case Instruction::Select:
4726 // U can also be a select constant expr, which let fall through. Since
4727 // createNodeForSelect only works for a condition that is an `ICmpInst`, and
4728 // constant expressions cannot have instructions as operands, we'd have
4729 // returned getUnknown for a select constant expressions anyway.
4730 if (isa<Instruction>(U))
4731 return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0),
4732 U->getOperand(1), U->getOperand(2));
4734 default: // We cannot analyze this expression.
4738 return getUnknown(V);
4743 //===----------------------------------------------------------------------===//
4744 // Iteration Count Computation Code
4747 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
4748 if (BasicBlock *ExitingBB = L->getExitingBlock())
4749 return getSmallConstantTripCount(L, ExitingBB);
4751 // No trip count information for multiple exits.
4755 /// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
4756 /// normal unsigned value. Returns 0 if the trip count is unknown or not
4757 /// constant. Will also return 0 if the maximum trip count is very large (>=
4760 /// This "trip count" assumes that control exits via ExitingBlock. More
4761 /// precisely, it is the number of times that control may reach ExitingBlock
4762 /// before taking the branch. For loops with multiple exits, it may not be the
4763 /// number times that the loop header executes because the loop may exit
4764 /// prematurely via another branch.
4765 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
4766 BasicBlock *ExitingBlock) {
4767 assert(ExitingBlock && "Must pass a non-null exiting block!");
4768 assert(L->isLoopExiting(ExitingBlock) &&
4769 "Exiting block must actually branch out of the loop!");
4770 const SCEVConstant *ExitCount =
4771 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
4775 ConstantInt *ExitConst = ExitCount->getValue();
4777 // Guard against huge trip counts.
4778 if (ExitConst->getValue().getActiveBits() > 32)
4781 // In case of integer overflow, this returns 0, which is correct.
4782 return ((unsigned)ExitConst->getZExtValue()) + 1;
4785 unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
4786 if (BasicBlock *ExitingBB = L->getExitingBlock())
4787 return getSmallConstantTripMultiple(L, ExitingBB);
4789 // No trip multiple information for multiple exits.
4793 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
4794 /// trip count of this loop as a normal unsigned value, if possible. This
4795 /// means that the actual trip count is always a multiple of the returned
4796 /// value (don't forget the trip count could very well be zero as well!).
4798 /// Returns 1 if the trip count is unknown or not guaranteed to be the
4799 /// multiple of a constant (which is also the case if the trip count is simply
4800 /// constant, use getSmallConstantTripCount for that case), Will also return 1
4801 /// if the trip count is very large (>= 2^32).
4803 /// As explained in the comments for getSmallConstantTripCount, this assumes
4804 /// that control exits the loop via ExitingBlock.
4806 ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
4807 BasicBlock *ExitingBlock) {
4808 assert(ExitingBlock && "Must pass a non-null exiting block!");
4809 assert(L->isLoopExiting(ExitingBlock) &&
4810 "Exiting block must actually branch out of the loop!");
4811 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
4812 if (ExitCount == getCouldNotCompute())
4815 // Get the trip count from the BE count by adding 1.
4816 const SCEV *TCMul = getAddExpr(ExitCount, getOne(ExitCount->getType()));
4817 // FIXME: SCEV distributes multiplication as V1*C1 + V2*C1. We could attempt
4818 // to factor simple cases.
4819 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(TCMul))
4820 TCMul = Mul->getOperand(0);
4822 const SCEVConstant *MulC = dyn_cast<SCEVConstant>(TCMul);
4826 ConstantInt *Result = MulC->getValue();
4828 // Guard against huge trip counts (this requires checking
4829 // for zero to handle the case where the trip count == -1 and the
4831 if (!Result || Result->getValue().getActiveBits() > 32 ||
4832 Result->getValue().getActiveBits() == 0)
4835 return (unsigned)Result->getZExtValue();
4838 // getExitCount - Get the expression for the number of loop iterations for which
4839 // this loop is guaranteed not to exit via ExitingBlock. Otherwise return
4840 // SCEVCouldNotCompute.
4841 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
4842 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
4845 /// getBackedgeTakenCount - If the specified loop has a predictable
4846 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
4847 /// object. The backedge-taken count is the number of times the loop header
4848 /// will be branched to from within the loop. This is one less than the
4849 /// trip count of the loop, since it doesn't count the first iteration,
4850 /// when the header is branched to from outside the loop.
4852 /// Note that it is not valid to call this method on a loop without a
4853 /// loop-invariant backedge-taken count (see
4854 /// hasLoopInvariantBackedgeTakenCount).
4856 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
4857 return getBackedgeTakenInfo(L).getExact(this);
4860 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
4861 /// return the least SCEV value that is known never to be less than the
4862 /// actual backedge taken count.
4863 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
4864 return getBackedgeTakenInfo(L).getMax(this);
4867 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
4868 /// onto the given Worklist.
4870 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
4871 BasicBlock *Header = L->getHeader();
4873 // Push all Loop-header PHIs onto the Worklist stack.
4874 for (BasicBlock::iterator I = Header->begin();
4875 PHINode *PN = dyn_cast<PHINode>(I); ++I)
4876 Worklist.push_back(PN);
4879 const ScalarEvolution::BackedgeTakenInfo &
4880 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
4881 // Initially insert an invalid entry for this loop. If the insertion
4882 // succeeds, proceed to actually compute a backedge-taken count and
4883 // update the value. The temporary CouldNotCompute value tells SCEV
4884 // code elsewhere that it shouldn't attempt to request a new
4885 // backedge-taken count, which could result in infinite recursion.
4886 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
4887 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
4889 return Pair.first->second;
4891 // computeBackedgeTakenCount may allocate memory for its result. Inserting it
4892 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
4893 // must be cleared in this scope.
4894 BackedgeTakenInfo Result = computeBackedgeTakenCount(L);
4896 if (Result.getExact(this) != getCouldNotCompute()) {
4897 assert(isLoopInvariant(Result.getExact(this), L) &&
4898 isLoopInvariant(Result.getMax(this), L) &&
4899 "Computed backedge-taken count isn't loop invariant for loop!");
4900 ++NumTripCountsComputed;
4902 else if (Result.getMax(this) == getCouldNotCompute() &&
4903 isa<PHINode>(L->getHeader()->begin())) {
4904 // Only count loops that have phi nodes as not being computable.
4905 ++NumTripCountsNotComputed;
4908 // Now that we know more about the trip count for this loop, forget any
4909 // existing SCEV values for PHI nodes in this loop since they are only
4910 // conservative estimates made without the benefit of trip count
4911 // information. This is similar to the code in forgetLoop, except that
4912 // it handles SCEVUnknown PHI nodes specially.
4913 if (Result.hasAnyInfo()) {
4914 SmallVector<Instruction *, 16> Worklist;
4915 PushLoopPHIs(L, Worklist);
4917 SmallPtrSet<Instruction *, 8> Visited;
4918 while (!Worklist.empty()) {
4919 Instruction *I = Worklist.pop_back_val();
4920 if (!Visited.insert(I).second)
4923 ValueExprMapType::iterator It =
4924 ValueExprMap.find_as(static_cast<Value *>(I));
4925 if (It != ValueExprMap.end()) {
4926 const SCEV *Old = It->second;
4928 // SCEVUnknown for a PHI either means that it has an unrecognized
4929 // structure, or it's a PHI that's in the progress of being computed
4930 // by createNodeForPHI. In the former case, additional loop trip
4931 // count information isn't going to change anything. In the later
4932 // case, createNodeForPHI will perform the necessary updates on its
4933 // own when it gets to that point.
4934 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
4935 forgetMemoizedResults(Old);
4936 ValueExprMap.erase(It);
4938 if (PHINode *PN = dyn_cast<PHINode>(I))
4939 ConstantEvolutionLoopExitValue.erase(PN);
4942 PushDefUseChildren(I, Worklist);
4946 // Re-lookup the insert position, since the call to
4947 // computeBackedgeTakenCount above could result in a
4948 // recusive call to getBackedgeTakenInfo (on a different
4949 // loop), which would invalidate the iterator computed
4951 return BackedgeTakenCounts.find(L)->second = Result;
4954 /// forgetLoop - This method should be called by the client when it has
4955 /// changed a loop in a way that may effect ScalarEvolution's ability to
4956 /// compute a trip count, or if the loop is deleted.
4957 void ScalarEvolution::forgetLoop(const Loop *L) {
4958 // Drop any stored trip count value.
4959 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
4960 BackedgeTakenCounts.find(L);
4961 if (BTCPos != BackedgeTakenCounts.end()) {
4962 BTCPos->second.clear();
4963 BackedgeTakenCounts.erase(BTCPos);
4966 // Drop information about expressions based on loop-header PHIs.
4967 SmallVector<Instruction *, 16> Worklist;
4968 PushLoopPHIs(L, Worklist);
4970 SmallPtrSet<Instruction *, 8> Visited;
4971 while (!Worklist.empty()) {
4972 Instruction *I = Worklist.pop_back_val();
4973 if (!Visited.insert(I).second)
4976 ValueExprMapType::iterator It =
4977 ValueExprMap.find_as(static_cast<Value *>(I));
4978 if (It != ValueExprMap.end()) {
4979 forgetMemoizedResults(It->second);
4980 ValueExprMap.erase(It);
4981 if (PHINode *PN = dyn_cast<PHINode>(I))
4982 ConstantEvolutionLoopExitValue.erase(PN);
4985 PushDefUseChildren(I, Worklist);
4988 // Forget all contained loops too, to avoid dangling entries in the
4989 // ValuesAtScopes map.
4990 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
4994 /// forgetValue - This method should be called by the client when it has
4995 /// changed a value in a way that may effect its value, or which may
4996 /// disconnect it from a def-use chain linking it to a loop.
4997 void ScalarEvolution::forgetValue(Value *V) {
4998 Instruction *I = dyn_cast<Instruction>(V);
5001 // Drop information about expressions based on loop-header PHIs.
5002 SmallVector<Instruction *, 16> Worklist;
5003 Worklist.push_back(I);
5005 SmallPtrSet<Instruction *, 8> Visited;
5006 while (!Worklist.empty()) {
5007 I = Worklist.pop_back_val();
5008 if (!Visited.insert(I).second)
5011 ValueExprMapType::iterator It =
5012 ValueExprMap.find_as(static_cast<Value *>(I));
5013 if (It != ValueExprMap.end()) {
5014 forgetMemoizedResults(It->second);
5015 ValueExprMap.erase(It);
5016 if (PHINode *PN = dyn_cast<PHINode>(I))
5017 ConstantEvolutionLoopExitValue.erase(PN);
5020 PushDefUseChildren(I, Worklist);
5024 /// getExact - Get the exact loop backedge taken count considering all loop
5025 /// exits. A computable result can only be returned for loops with a single
5026 /// exit. Returning the minimum taken count among all exits is incorrect
5027 /// because one of the loop's exit limit's may have been skipped. HowFarToZero
5028 /// assumes that the limit of each loop test is never skipped. This is a valid
5029 /// assumption as long as the loop exits via that test. For precise results, it
5030 /// is the caller's responsibility to specify the relevant loop exit using
5031 /// getExact(ExitingBlock, SE).
5033 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
5034 // If any exits were not computable, the loop is not computable.
5035 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
5037 // We need exactly one computable exit.
5038 if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
5039 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
5041 const SCEV *BECount = nullptr;
5042 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5043 ENT != nullptr; ENT = ENT->getNextExit()) {
5045 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
5048 BECount = ENT->ExactNotTaken;
5049 else if (BECount != ENT->ExactNotTaken)
5050 return SE->getCouldNotCompute();
5052 assert(BECount && "Invalid not taken count for loop exit");
5056 /// getExact - Get the exact not taken count for this loop exit.
5058 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
5059 ScalarEvolution *SE) const {
5060 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5061 ENT != nullptr; ENT = ENT->getNextExit()) {
5063 if (ENT->ExitingBlock == ExitingBlock)
5064 return ENT->ExactNotTaken;
5066 return SE->getCouldNotCompute();
5069 /// getMax - Get the max backedge taken count for the loop.
5071 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
5072 return Max ? Max : SE->getCouldNotCompute();
5075 bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
5076 ScalarEvolution *SE) const {
5077 if (Max && Max != SE->getCouldNotCompute() && SE->hasOperand(Max, S))
5080 if (!ExitNotTaken.ExitingBlock)
5083 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
5084 ENT != nullptr; ENT = ENT->getNextExit()) {
5086 if (ENT->ExactNotTaken != SE->getCouldNotCompute()
5087 && SE->hasOperand(ENT->ExactNotTaken, S)) {
5094 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
5095 /// computable exit into a persistent ExitNotTakenInfo array.
5096 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
5097 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
5098 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
5101 ExitNotTaken.setIncomplete();
5103 unsigned NumExits = ExitCounts.size();
5104 if (NumExits == 0) return;
5106 ExitNotTaken.ExitingBlock = ExitCounts[0].first;
5107 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
5108 if (NumExits == 1) return;
5110 // Handle the rare case of multiple computable exits.
5111 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
5113 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
5114 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
5115 PrevENT->setNextExit(ENT);
5116 ENT->ExitingBlock = ExitCounts[i].first;
5117 ENT->ExactNotTaken = ExitCounts[i].second;
5121 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
5122 void ScalarEvolution::BackedgeTakenInfo::clear() {
5123 ExitNotTaken.ExitingBlock = nullptr;
5124 ExitNotTaken.ExactNotTaken = nullptr;
5125 delete[] ExitNotTaken.getNextExit();
5128 /// computeBackedgeTakenCount - Compute the number of times the backedge
5129 /// of the specified loop will execute.
5130 ScalarEvolution::BackedgeTakenInfo
5131 ScalarEvolution::computeBackedgeTakenCount(const Loop *L) {
5132 SmallVector<BasicBlock *, 8> ExitingBlocks;
5133 L->getExitingBlocks(ExitingBlocks);
5135 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
5136 bool CouldComputeBECount = true;
5137 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
5138 const SCEV *MustExitMaxBECount = nullptr;
5139 const SCEV *MayExitMaxBECount = nullptr;
5141 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
5142 // and compute maxBECount.
5143 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
5144 BasicBlock *ExitBB = ExitingBlocks[i];
5145 ExitLimit EL = computeExitLimit(L, ExitBB);
5147 // 1. For each exit that can be computed, add an entry to ExitCounts.
5148 // CouldComputeBECount is true only if all exits can be computed.
5149 if (EL.Exact == getCouldNotCompute())
5150 // We couldn't compute an exact value for this exit, so
5151 // we won't be able to compute an exact value for the loop.
5152 CouldComputeBECount = false;
5154 ExitCounts.push_back(std::make_pair(ExitBB, EL.Exact));
5156 // 2. Derive the loop's MaxBECount from each exit's max number of
5157 // non-exiting iterations. Partition the loop exits into two kinds:
5158 // LoopMustExits and LoopMayExits.
5160 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
5161 // is a LoopMayExit. If any computable LoopMustExit is found, then
5162 // MaxBECount is the minimum EL.Max of computable LoopMustExits. Otherwise,
5163 // MaxBECount is conservatively the maximum EL.Max, where CouldNotCompute is
5164 // considered greater than any computable EL.Max.
5165 if (EL.Max != getCouldNotCompute() && Latch &&
5166 DT.dominates(ExitBB, Latch)) {
5167 if (!MustExitMaxBECount)
5168 MustExitMaxBECount = EL.Max;
5170 MustExitMaxBECount =
5171 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.Max);
5173 } else if (MayExitMaxBECount != getCouldNotCompute()) {
5174 if (!MayExitMaxBECount || EL.Max == getCouldNotCompute())
5175 MayExitMaxBECount = EL.Max;
5178 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.Max);
5182 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
5183 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
5184 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
5187 ScalarEvolution::ExitLimit
5188 ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
5190 // Okay, we've chosen an exiting block. See what condition causes us to exit
5191 // at this block and remember the exit block and whether all other targets
5192 // lead to the loop header.
5193 bool MustExecuteLoopHeader = true;
5194 BasicBlock *Exit = nullptr;
5195 for (succ_iterator SI = succ_begin(ExitingBlock), SE = succ_end(ExitingBlock);
5197 if (!L->contains(*SI)) {
5198 if (Exit) // Multiple exit successors.
5199 return getCouldNotCompute();
5201 } else if (*SI != L->getHeader()) {
5202 MustExecuteLoopHeader = false;
5205 // At this point, we know we have a conditional branch that determines whether
5206 // the loop is exited. However, we don't know if the branch is executed each
5207 // time through the loop. If not, then the execution count of the branch will
5208 // not be equal to the trip count of the loop.
5210 // Currently we check for this by checking to see if the Exit branch goes to
5211 // the loop header. If so, we know it will always execute the same number of
5212 // times as the loop. We also handle the case where the exit block *is* the
5213 // loop header. This is common for un-rotated loops.
5215 // If both of those tests fail, walk up the unique predecessor chain to the
5216 // header, stopping if there is an edge that doesn't exit the loop. If the
5217 // header is reached, the execution count of the branch will be equal to the
5218 // trip count of the loop.
5220 // More extensive analysis could be done to handle more cases here.
5222 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
5223 // The simple checks failed, try climbing the unique predecessor chain
5224 // up to the header.
5226 for (BasicBlock *BB = ExitingBlock; BB; ) {
5227 BasicBlock *Pred = BB->getUniquePredecessor();
5229 return getCouldNotCompute();
5230 TerminatorInst *PredTerm = Pred->getTerminator();
5231 for (const BasicBlock *PredSucc : PredTerm->successors()) {
5234 // If the predecessor has a successor that isn't BB and isn't
5235 // outside the loop, assume the worst.
5236 if (L->contains(PredSucc))
5237 return getCouldNotCompute();
5239 if (Pred == L->getHeader()) {
5246 return getCouldNotCompute();
5249 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
5250 TerminatorInst *Term = ExitingBlock->getTerminator();
5251 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
5252 assert(BI->isConditional() && "If unconditional, it can't be in loop!");
5253 // Proceed to the next level to examine the exit condition expression.
5254 return computeExitLimitFromCond(L, BI->getCondition(), BI->getSuccessor(0),
5255 BI->getSuccessor(1),
5256 /*ControlsExit=*/IsOnlyExit);
5259 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
5260 return computeExitLimitFromSingleExitSwitch(L, SI, Exit,
5261 /*ControlsExit=*/IsOnlyExit);
5263 return getCouldNotCompute();
5266 /// computeExitLimitFromCond - Compute the number of times the
5267 /// backedge of the specified loop will execute if its exit condition
5268 /// were a conditional branch of ExitCond, TBB, and FBB.
5270 /// @param ControlsExit is true if ExitCond directly controls the exit
5271 /// branch. In this case, we can assume that the loop exits only if the
5272 /// condition is true and can infer that failing to meet the condition prior to
5273 /// integer wraparound results in undefined behavior.
5274 ScalarEvolution::ExitLimit
5275 ScalarEvolution::computeExitLimitFromCond(const Loop *L,
5279 bool ControlsExit) {
5280 // Check if the controlling expression for this loop is an And or Or.
5281 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
5282 if (BO->getOpcode() == Instruction::And) {
5283 // Recurse on the operands of the and.
5284 bool EitherMayExit = L->contains(TBB);
5285 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
5286 ControlsExit && !EitherMayExit);
5287 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
5288 ControlsExit && !EitherMayExit);
5289 const SCEV *BECount = getCouldNotCompute();
5290 const SCEV *MaxBECount = getCouldNotCompute();
5291 if (EitherMayExit) {
5292 // Both conditions must be true for the loop to continue executing.
5293 // Choose the less conservative count.
5294 if (EL0.Exact == getCouldNotCompute() ||
5295 EL1.Exact == getCouldNotCompute())
5296 BECount = getCouldNotCompute();
5298 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
5299 if (EL0.Max == getCouldNotCompute())
5300 MaxBECount = EL1.Max;
5301 else if (EL1.Max == getCouldNotCompute())
5302 MaxBECount = EL0.Max;
5304 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
5306 // Both conditions must be true at the same time for the loop to exit.
5307 // For now, be conservative.
5308 assert(L->contains(FBB) && "Loop block has no successor in loop!");
5309 if (EL0.Max == EL1.Max)
5310 MaxBECount = EL0.Max;
5311 if (EL0.Exact == EL1.Exact)
5312 BECount = EL0.Exact;
5315 return ExitLimit(BECount, MaxBECount);
5317 if (BO->getOpcode() == Instruction::Or) {
5318 // Recurse on the operands of the or.
5319 bool EitherMayExit = L->contains(FBB);
5320 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
5321 ControlsExit && !EitherMayExit);
5322 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
5323 ControlsExit && !EitherMayExit);
5324 const SCEV *BECount = getCouldNotCompute();
5325 const SCEV *MaxBECount = getCouldNotCompute();
5326 if (EitherMayExit) {
5327 // Both conditions must be false for the loop to continue executing.
5328 // Choose the less conservative count.
5329 if (EL0.Exact == getCouldNotCompute() ||
5330 EL1.Exact == getCouldNotCompute())
5331 BECount = getCouldNotCompute();
5333 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
5334 if (EL0.Max == getCouldNotCompute())
5335 MaxBECount = EL1.Max;
5336 else if (EL1.Max == getCouldNotCompute())
5337 MaxBECount = EL0.Max;
5339 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
5341 // Both conditions must be false at the same time for the loop to exit.
5342 // For now, be conservative.
5343 assert(L->contains(TBB) && "Loop block has no successor in loop!");
5344 if (EL0.Max == EL1.Max)
5345 MaxBECount = EL0.Max;
5346 if (EL0.Exact == EL1.Exact)
5347 BECount = EL0.Exact;
5350 return ExitLimit(BECount, MaxBECount);
5354 // With an icmp, it may be feasible to compute an exact backedge-taken count.
5355 // Proceed to the next level to examine the icmp.
5356 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
5357 return computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
5359 // Check for a constant condition. These are normally stripped out by
5360 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
5361 // preserve the CFG and is temporarily leaving constant conditions
5363 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
5364 if (L->contains(FBB) == !CI->getZExtValue())
5365 // The backedge is always taken.
5366 return getCouldNotCompute();
5368 // The backedge is never taken.
5369 return getZero(CI->getType());
5372 // If it's not an integer or pointer comparison then compute it the hard way.
5373 return computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5376 ScalarEvolution::ExitLimit
5377 ScalarEvolution::computeExitLimitFromICmp(const Loop *L,
5381 bool ControlsExit) {
5383 // If the condition was exit on true, convert the condition to exit on false
5384 ICmpInst::Predicate Cond;
5385 if (!L->contains(FBB))
5386 Cond = ExitCond->getPredicate();
5388 Cond = ExitCond->getInversePredicate();
5390 // Handle common loops like: for (X = "string"; *X; ++X)
5391 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
5392 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
5394 computeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
5395 if (ItCnt.hasAnyInfo())
5399 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
5400 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
5402 // Try to evaluate any dependencies out of the loop.
5403 LHS = getSCEVAtScope(LHS, L);
5404 RHS = getSCEVAtScope(RHS, L);
5406 // At this point, we would like to compute how many iterations of the
5407 // loop the predicate will return true for these inputs.
5408 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
5409 // If there is a loop-invariant, force it into the RHS.
5410 std::swap(LHS, RHS);
5411 Cond = ICmpInst::getSwappedPredicate(Cond);
5414 // Simplify the operands before analyzing them.
5415 (void)SimplifyICmpOperands(Cond, LHS, RHS);
5417 // If we have a comparison of a chrec against a constant, try to use value
5418 // ranges to answer this query.
5419 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
5420 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
5421 if (AddRec->getLoop() == L) {
5422 // Form the constant range.
5423 ConstantRange CompRange(
5424 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
5426 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
5427 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
5431 case ICmpInst::ICMP_NE: { // while (X != Y)
5432 // Convert to: while (X-Y != 0)
5433 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5434 if (EL.hasAnyInfo()) return EL;
5437 case ICmpInst::ICMP_EQ: { // while (X == Y)
5438 // Convert to: while (X-Y == 0)
5439 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
5440 if (EL.hasAnyInfo()) return EL;
5443 case ICmpInst::ICMP_SLT:
5444 case ICmpInst::ICMP_ULT: { // while (X < Y)
5445 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
5446 ExitLimit EL = HowManyLessThans(LHS, RHS, L, IsSigned, ControlsExit);
5447 if (EL.hasAnyInfo()) return EL;
5450 case ICmpInst::ICMP_SGT:
5451 case ICmpInst::ICMP_UGT: { // while (X > Y)
5452 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
5453 ExitLimit EL = HowManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit);
5454 if (EL.hasAnyInfo()) return EL;
5459 dbgs() << "computeBackedgeTakenCount ";
5460 if (ExitCond->getOperand(0)->getType()->isUnsigned())
5461 dbgs() << "[unsigned] ";
5462 dbgs() << *LHS << " "
5463 << Instruction::getOpcodeName(Instruction::ICmp)
5464 << " " << *RHS << "\n";
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()) {
5579 dbgs() << "\n***\n*** Computed loop count " << *ItCst
5580 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
5583 ++NumArrayLenItCounts;
5584 return getConstant(ItCst); // Found terminating iteration!
5587 return getCouldNotCompute();
5591 /// CanConstantFold - Return true if we can constant fold an instruction of the
5592 /// specified type, assuming that all operands were constants.
5593 static bool CanConstantFold(const Instruction *I) {
5594 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
5595 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
5599 if (const CallInst *CI = dyn_cast<CallInst>(I))
5600 if (const Function *F = CI->getCalledFunction())
5601 return canConstantFoldCallTo(F);
5605 /// Determine whether this instruction can constant evolve within this loop
5606 /// assuming its operands can all constant evolve.
5607 static bool canConstantEvolve(Instruction *I, const Loop *L) {
5608 // An instruction outside of the loop can't be derived from a loop PHI.
5609 if (!L->contains(I)) return false;
5611 if (isa<PHINode>(I)) {
5612 // We don't currently keep track of the control flow needed to evaluate
5613 // PHIs, so we cannot handle PHIs inside of loops.
5614 return L->getHeader() == I->getParent();
5617 // If we won't be able to constant fold this expression even if the operands
5618 // are constants, bail early.
5619 return CanConstantFold(I);
5622 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
5623 /// recursing through each instruction operand until reaching a loop header phi.
5625 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
5626 DenseMap<Instruction *, PHINode *> &PHIMap) {
5628 // Otherwise, we can evaluate this instruction if all of its operands are
5629 // constant or derived from a PHI node themselves.
5630 PHINode *PHI = nullptr;
5631 for (Instruction::op_iterator OpI = UseInst->op_begin(),
5632 OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
5634 if (isa<Constant>(*OpI)) continue;
5636 Instruction *OpInst = dyn_cast<Instruction>(*OpI);
5637 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
5639 PHINode *P = dyn_cast<PHINode>(OpInst);
5641 // If this operand is already visited, reuse the prior result.
5642 // We may have P != PHI if this is the deepest point at which the
5643 // inconsistent paths meet.
5644 P = PHIMap.lookup(OpInst);
5646 // Recurse and memoize the results, whether a phi is found or not.
5647 // This recursive call invalidates pointers into PHIMap.
5648 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
5652 return nullptr; // Not evolving from PHI
5653 if (PHI && PHI != P)
5654 return nullptr; // Evolving from multiple different PHIs.
5657 // This is a expression evolving from a constant PHI!
5661 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
5662 /// in the loop that V is derived from. We allow arbitrary operations along the
5663 /// way, but the operands of an operation must either be constants or a value
5664 /// derived from a constant PHI. If this expression does not fit with these
5665 /// constraints, return null.
5666 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
5667 Instruction *I = dyn_cast<Instruction>(V);
5668 if (!I || !canConstantEvolve(I, L)) return nullptr;
5670 if (PHINode *PN = dyn_cast<PHINode>(I))
5673 // Record non-constant instructions contained by the loop.
5674 DenseMap<Instruction *, PHINode *> PHIMap;
5675 return getConstantEvolvingPHIOperands(I, L, PHIMap);
5678 /// EvaluateExpression - Given an expression that passes the
5679 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
5680 /// in the loop has the value PHIVal. If we can't fold this expression for some
5681 /// reason, return null.
5682 static Constant *EvaluateExpression(Value *V, const Loop *L,
5683 DenseMap<Instruction *, Constant *> &Vals,
5684 const DataLayout &DL,
5685 const TargetLibraryInfo *TLI) {
5686 // Convenient constant check, but redundant for recursive calls.
5687 if (Constant *C = dyn_cast<Constant>(V)) return C;
5688 Instruction *I = dyn_cast<Instruction>(V);
5689 if (!I) return nullptr;
5691 if (Constant *C = Vals.lookup(I)) return C;
5693 // An instruction inside the loop depends on a value outside the loop that we
5694 // weren't given a mapping for, or a value such as a call inside the loop.
5695 if (!canConstantEvolve(I, L)) return nullptr;
5697 // An unmapped PHI can be due to a branch or another loop inside this loop,
5698 // or due to this not being the initial iteration through a loop where we
5699 // couldn't compute the evolution of this particular PHI last time.
5700 if (isa<PHINode>(I)) return nullptr;
5702 std::vector<Constant*> Operands(I->getNumOperands());
5704 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5705 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
5707 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
5708 if (!Operands[i]) return nullptr;
5711 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
5713 if (!C) return nullptr;
5717 if (CmpInst *CI = dyn_cast<CmpInst>(I))
5718 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
5719 Operands[1], DL, TLI);
5720 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
5721 if (!LI->isVolatile())
5722 return ConstantFoldLoadFromConstPtr(Operands[0], DL);
5724 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, DL,
5728 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
5729 /// in the header of its containing loop, we know the loop executes a
5730 /// constant number of times, and the PHI node is just a recurrence
5731 /// involving constants, fold it.
5733 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
5736 auto I = ConstantEvolutionLoopExitValue.find(PN);
5737 if (I != ConstantEvolutionLoopExitValue.end())
5740 if (BEs.ugt(MaxBruteForceIterations))
5741 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
5743 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
5745 DenseMap<Instruction *, Constant *> CurrentIterVals;
5746 BasicBlock *Header = L->getHeader();
5747 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5749 BasicBlock *Latch = L->getLoopLatch();
5753 // Since the loop has one latch, the PHI node must have two entries. One
5754 // entry must be a constant (coming in from outside of the loop), and the
5755 // second must be derived from the same PHI.
5757 BasicBlock *NonLatch = Latch == PN->getIncomingBlock(0)
5758 ? PN->getIncomingBlock(1)
5759 : PN->getIncomingBlock(0);
5761 assert(PN->getNumIncomingValues() == 2 && "Follows from having one latch!");
5763 // Note: not all PHI nodes in the same block have to have their incoming
5764 // values in the same order, so we use the basic block to look up the incoming
5765 // value, not an index.
5767 for (auto &I : *Header) {
5768 PHINode *PHI = dyn_cast<PHINode>(&I);
5771 dyn_cast<Constant>(PHI->getIncomingValueForBlock(NonLatch));
5772 if (!StartCST) continue;
5773 CurrentIterVals[PHI] = StartCST;
5775 if (!CurrentIterVals.count(PN))
5776 return RetVal = nullptr;
5778 Value *BEValue = PN->getIncomingValueForBlock(Latch);
5780 // Execute the loop symbolically to determine the exit value.
5781 if (BEs.getActiveBits() >= 32)
5782 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
5784 unsigned NumIterations = BEs.getZExtValue(); // must be in range
5785 unsigned IterationNum = 0;
5786 const DataLayout &DL = F.getParent()->getDataLayout();
5787 for (; ; ++IterationNum) {
5788 if (IterationNum == NumIterations)
5789 return RetVal = CurrentIterVals[PN]; // Got exit value!
5791 // Compute the value of the PHIs for the next iteration.
5792 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
5793 DenseMap<Instruction *, Constant *> NextIterVals;
5795 EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
5797 return nullptr; // Couldn't evaluate!
5798 NextIterVals[PN] = NextPHI;
5800 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
5802 // Also evaluate the other PHI nodes. However, we don't get to stop if we
5803 // cease to be able to evaluate one of them or if they stop evolving,
5804 // because that doesn't necessarily prevent us from computing PN.
5805 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
5806 for (const auto &I : CurrentIterVals) {
5807 PHINode *PHI = dyn_cast<PHINode>(I.first);
5808 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
5809 PHIsToCompute.emplace_back(PHI, I.second);
5811 // We use two distinct loops because EvaluateExpression may invalidate any
5812 // iterators into CurrentIterVals.
5813 for (const auto &I : PHIsToCompute) {
5814 PHINode *PHI = I.first;
5815 Constant *&NextPHI = NextIterVals[PHI];
5816 if (!NextPHI) { // Not already computed.
5817 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
5818 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
5820 if (NextPHI != I.second)
5821 StoppedEvolving = false;
5824 // If all entries in CurrentIterVals == NextIterVals then we can stop
5825 // iterating, the loop can't continue to change.
5826 if (StoppedEvolving)
5827 return RetVal = CurrentIterVals[PN];
5829 CurrentIterVals.swap(NextIterVals);
5833 const SCEV *ScalarEvolution::computeExitCountExhaustively(const Loop *L,
5836 PHINode *PN = getConstantEvolvingPHI(Cond, L);
5837 if (!PN) return getCouldNotCompute();
5839 // If the loop is canonicalized, the PHI will have exactly two entries.
5840 // That's the only form we support here.
5841 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
5843 DenseMap<Instruction *, Constant *> CurrentIterVals;
5844 BasicBlock *Header = L->getHeader();
5845 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5847 BasicBlock *Latch = L->getLoopLatch();
5848 assert(Latch && "Should follow from NumIncomingValues == 2!");
5850 // NonLatch is the preheader, or something equivalent.
5851 BasicBlock *NonLatch = Latch == PN->getIncomingBlock(0)
5852 ? PN->getIncomingBlock(1)
5853 : PN->getIncomingBlock(0);
5855 // Note: not all PHI nodes in the same block have to have their incoming
5856 // values in the same order, so we use the basic block to look up the incoming
5857 // value, not an index.
5859 for (auto &I : *Header) {
5860 PHINode *PHI = dyn_cast<PHINode>(&I);
5864 dyn_cast<Constant>(PHI->getIncomingValueForBlock(NonLatch));
5865 if (!StartCST) continue;
5866 CurrentIterVals[PHI] = StartCST;
5868 if (!CurrentIterVals.count(PN))
5869 return getCouldNotCompute();
5871 // Okay, we find a PHI node that defines the trip count of this loop. Execute
5872 // the loop symbolically to determine when the condition gets a value of
5874 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
5875 const DataLayout &DL = F.getParent()->getDataLayout();
5876 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
5877 auto *CondVal = dyn_cast_or_null<ConstantInt>(
5878 EvaluateExpression(Cond, L, CurrentIterVals, DL, &TLI));
5880 // Couldn't symbolically evaluate.
5881 if (!CondVal) return getCouldNotCompute();
5883 if (CondVal->getValue() == uint64_t(ExitWhen)) {
5884 ++NumBruteForceTripCountsComputed;
5885 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
5888 // Update all the PHI nodes for the next iteration.
5889 DenseMap<Instruction *, Constant *> NextIterVals;
5891 // Create a list of which PHIs we need to compute. We want to do this before
5892 // calling EvaluateExpression on them because that may invalidate iterators
5893 // into CurrentIterVals.
5894 SmallVector<PHINode *, 8> PHIsToCompute;
5895 for (const auto &I : CurrentIterVals) {
5896 PHINode *PHI = dyn_cast<PHINode>(I.first);
5897 if (!PHI || PHI->getParent() != Header) continue;
5898 PHIsToCompute.push_back(PHI);
5900 for (PHINode *PHI : PHIsToCompute) {
5901 Constant *&NextPHI = NextIterVals[PHI];
5902 if (NextPHI) continue; // Already computed!
5904 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
5905 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
5907 CurrentIterVals.swap(NextIterVals);
5910 // Too many iterations were needed to evaluate.
5911 return getCouldNotCompute();
5914 /// getSCEVAtScope - Return a SCEV expression for the specified value
5915 /// at the specified scope in the program. The L value specifies a loop
5916 /// nest to evaluate the expression at, where null is the top-level or a
5917 /// specified loop is immediately inside of the loop.
5919 /// This method can be used to compute the exit value for a variable defined
5920 /// in a loop by querying what the value will hold in the parent loop.
5922 /// In the case that a relevant loop exit value cannot be computed, the
5923 /// original value V is returned.
5924 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
5925 // Check to see if we've folded this expression at this loop before.
5926 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = ValuesAtScopes[V];
5927 for (unsigned u = 0; u < Values.size(); u++) {
5928 if (Values[u].first == L)
5929 return Values[u].second ? Values[u].second : V;
5931 Values.push_back(std::make_pair(L, static_cast<const SCEV *>(nullptr)));
5932 // Otherwise compute it.
5933 const SCEV *C = computeSCEVAtScope(V, L);
5934 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values2 = ValuesAtScopes[V];
5935 for (unsigned u = Values2.size(); u > 0; u--) {
5936 if (Values2[u - 1].first == L) {
5937 Values2[u - 1].second = C;
5944 /// This builds up a Constant using the ConstantExpr interface. That way, we
5945 /// will return Constants for objects which aren't represented by a
5946 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
5947 /// Returns NULL if the SCEV isn't representable as a Constant.
5948 static Constant *BuildConstantFromSCEV(const SCEV *V) {
5949 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
5950 case scCouldNotCompute:
5954 return cast<SCEVConstant>(V)->getValue();
5956 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
5957 case scSignExtend: {
5958 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
5959 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
5960 return ConstantExpr::getSExt(CastOp, SS->getType());
5963 case scZeroExtend: {
5964 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
5965 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
5966 return ConstantExpr::getZExt(CastOp, SZ->getType());
5970 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
5971 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
5972 return ConstantExpr::getTrunc(CastOp, ST->getType());
5976 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
5977 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
5978 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
5979 unsigned AS = PTy->getAddressSpace();
5980 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5981 C = ConstantExpr::getBitCast(C, DestPtrTy);
5983 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
5984 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
5985 if (!C2) return nullptr;
5988 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
5989 unsigned AS = C2->getType()->getPointerAddressSpace();
5991 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5992 // The offsets have been converted to bytes. We can add bytes to an
5993 // i8* by GEP with the byte count in the first index.
5994 C = ConstantExpr::getBitCast(C, DestPtrTy);
5997 // Don't bother trying to sum two pointers. We probably can't
5998 // statically compute a load that results from it anyway.
5999 if (C2->getType()->isPointerTy())
6002 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6003 if (PTy->getElementType()->isStructTy())
6004 C2 = ConstantExpr::getIntegerCast(
6005 C2, Type::getInt32Ty(C->getContext()), true);
6006 C = ConstantExpr::getGetElementPtr(PTy->getElementType(), C, C2);
6008 C = ConstantExpr::getAdd(C, C2);
6015 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
6016 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
6017 // Don't bother with pointers at all.
6018 if (C->getType()->isPointerTy()) return nullptr;
6019 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
6020 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
6021 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
6022 C = ConstantExpr::getMul(C, C2);
6029 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
6030 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
6031 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
6032 if (LHS->getType() == RHS->getType())
6033 return ConstantExpr::getUDiv(LHS, RHS);
6038 break; // TODO: smax, umax.
6043 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
6044 if (isa<SCEVConstant>(V)) return V;
6046 // If this instruction is evolved from a constant-evolving PHI, compute the
6047 // exit value from the loop without using SCEVs.
6048 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
6049 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
6050 const Loop *LI = this->LI[I->getParent()];
6051 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
6052 if (PHINode *PN = dyn_cast<PHINode>(I))
6053 if (PN->getParent() == LI->getHeader()) {
6054 // Okay, there is no closed form solution for the PHI node. Check
6055 // to see if the loop that contains it has a known backedge-taken
6056 // count. If so, we may be able to force computation of the exit
6058 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
6059 if (const SCEVConstant *BTCC =
6060 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
6061 // Okay, we know how many times the containing loop executes. If
6062 // this is a constant evolving PHI node, get the final value at
6063 // the specified iteration number.
6064 Constant *RV = getConstantEvolutionLoopExitValue(PN,
6065 BTCC->getValue()->getValue(),
6067 if (RV) return getSCEV(RV);
6071 // Okay, this is an expression that we cannot symbolically evaluate
6072 // into a SCEV. Check to see if it's possible to symbolically evaluate
6073 // the arguments into constants, and if so, try to constant propagate the
6074 // result. This is particularly useful for computing loop exit values.
6075 if (CanConstantFold(I)) {
6076 SmallVector<Constant *, 4> Operands;
6077 bool MadeImprovement = false;
6078 for (Value *Op : I->operands()) {
6079 if (Constant *C = dyn_cast<Constant>(Op)) {
6080 Operands.push_back(C);
6084 // If any of the operands is non-constant and if they are
6085 // non-integer and non-pointer, don't even try to analyze them
6086 // with scev techniques.
6087 if (!isSCEVable(Op->getType()))
6090 const SCEV *OrigV = getSCEV(Op);
6091 const SCEV *OpV = getSCEVAtScope(OrigV, L);
6092 MadeImprovement |= OrigV != OpV;
6094 Constant *C = BuildConstantFromSCEV(OpV);
6096 if (C->getType() != Op->getType())
6097 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
6101 Operands.push_back(C);
6104 // Check to see if getSCEVAtScope actually made an improvement.
6105 if (MadeImprovement) {
6106 Constant *C = nullptr;
6107 const DataLayout &DL = F.getParent()->getDataLayout();
6108 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
6109 C = ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
6110 Operands[1], DL, &TLI);
6111 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
6112 if (!LI->isVolatile())
6113 C = ConstantFoldLoadFromConstPtr(Operands[0], DL);
6115 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands,
6123 // This is some other type of SCEVUnknown, just return it.
6127 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
6128 // Avoid performing the look-up in the common case where the specified
6129 // expression has no loop-variant portions.
6130 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
6131 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
6132 if (OpAtScope != Comm->getOperand(i)) {
6133 // Okay, at least one of these operands is loop variant but might be
6134 // foldable. Build a new instance of the folded commutative expression.
6135 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
6136 Comm->op_begin()+i);
6137 NewOps.push_back(OpAtScope);
6139 for (++i; i != e; ++i) {
6140 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
6141 NewOps.push_back(OpAtScope);
6143 if (isa<SCEVAddExpr>(Comm))
6144 return getAddExpr(NewOps);
6145 if (isa<SCEVMulExpr>(Comm))
6146 return getMulExpr(NewOps);
6147 if (isa<SCEVSMaxExpr>(Comm))
6148 return getSMaxExpr(NewOps);
6149 if (isa<SCEVUMaxExpr>(Comm))
6150 return getUMaxExpr(NewOps);
6151 llvm_unreachable("Unknown commutative SCEV type!");
6154 // If we got here, all operands are loop invariant.
6158 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
6159 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
6160 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
6161 if (LHS == Div->getLHS() && RHS == Div->getRHS())
6162 return Div; // must be loop invariant
6163 return getUDivExpr(LHS, RHS);
6166 // If this is a loop recurrence for a loop that does not contain L, then we
6167 // are dealing with the final value computed by the loop.
6168 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
6169 // First, attempt to evaluate each operand.
6170 // Avoid performing the look-up in the common case where the specified
6171 // expression has no loop-variant portions.
6172 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
6173 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
6174 if (OpAtScope == AddRec->getOperand(i))
6177 // Okay, at least one of these operands is loop variant but might be
6178 // foldable. Build a new instance of the folded commutative expression.
6179 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
6180 AddRec->op_begin()+i);
6181 NewOps.push_back(OpAtScope);
6182 for (++i; i != e; ++i)
6183 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
6185 const SCEV *FoldedRec =
6186 getAddRecExpr(NewOps, AddRec->getLoop(),
6187 AddRec->getNoWrapFlags(SCEV::FlagNW));
6188 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
6189 // The addrec may be folded to a nonrecurrence, for example, if the
6190 // induction variable is multiplied by zero after constant folding. Go
6191 // ahead and return the folded value.
6197 // If the scope is outside the addrec's loop, evaluate it by using the
6198 // loop exit value of the addrec.
6199 if (!AddRec->getLoop()->contains(L)) {
6200 // To evaluate this recurrence, we need to know how many times the AddRec
6201 // loop iterates. Compute this now.
6202 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
6203 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
6205 // Then, evaluate the AddRec.
6206 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
6212 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
6213 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6214 if (Op == Cast->getOperand())
6215 return Cast; // must be loop invariant
6216 return getZeroExtendExpr(Op, Cast->getType());
6219 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
6220 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6221 if (Op == Cast->getOperand())
6222 return Cast; // must be loop invariant
6223 return getSignExtendExpr(Op, Cast->getType());
6226 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
6227 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
6228 if (Op == Cast->getOperand())
6229 return Cast; // must be loop invariant
6230 return getTruncateExpr(Op, Cast->getType());
6233 llvm_unreachable("Unknown SCEV type!");
6236 /// getSCEVAtScope - This is a convenience function which does
6237 /// getSCEVAtScope(getSCEV(V), L).
6238 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
6239 return getSCEVAtScope(getSCEV(V), L);
6242 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
6243 /// following equation:
6245 /// A * X = B (mod N)
6247 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
6248 /// A and B isn't important.
6250 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
6251 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
6252 ScalarEvolution &SE) {
6253 uint32_t BW = A.getBitWidth();
6254 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
6255 assert(A != 0 && "A must be non-zero.");
6259 // The gcd of A and N may have only one prime factor: 2. The number of
6260 // trailing zeros in A is its multiplicity
6261 uint32_t Mult2 = A.countTrailingZeros();
6264 // 2. Check if B is divisible by D.
6266 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
6267 // is not less than multiplicity of this prime factor for D.
6268 if (B.countTrailingZeros() < Mult2)
6269 return SE.getCouldNotCompute();
6271 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
6274 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
6275 // bit width during computations.
6276 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
6277 APInt Mod(BW + 1, 0);
6278 Mod.setBit(BW - Mult2); // Mod = N / D
6279 APInt I = AD.multiplicativeInverse(Mod);
6281 // 4. Compute the minimum unsigned root of the equation:
6282 // I * (B / D) mod (N / D)
6283 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
6285 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
6287 return SE.getConstant(Result.trunc(BW));
6290 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
6291 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
6292 /// might be the same) or two SCEVCouldNotCompute objects.
6294 static std::pair<const SCEV *,const SCEV *>
6295 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
6296 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
6297 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
6298 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
6299 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
6301 // We currently can only solve this if the coefficients are constants.
6302 if (!LC || !MC || !NC) {
6303 const SCEV *CNC = SE.getCouldNotCompute();
6304 return std::make_pair(CNC, CNC);
6307 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
6308 const APInt &L = LC->getValue()->getValue();
6309 const APInt &M = MC->getValue()->getValue();
6310 const APInt &N = NC->getValue()->getValue();
6311 APInt Two(BitWidth, 2);
6312 APInt Four(BitWidth, 4);
6315 using namespace APIntOps;
6317 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
6318 // The B coefficient is M-N/2
6322 // The A coefficient is N/2
6323 APInt A(N.sdiv(Two));
6325 // Compute the B^2-4ac term.
6328 SqrtTerm -= Four * (A * C);
6330 if (SqrtTerm.isNegative()) {
6331 // The loop is provably infinite.
6332 const SCEV *CNC = SE.getCouldNotCompute();
6333 return std::make_pair(CNC, CNC);
6336 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
6337 // integer value or else APInt::sqrt() will assert.
6338 APInt SqrtVal(SqrtTerm.sqrt());
6340 // Compute the two solutions for the quadratic formula.
6341 // The divisions must be performed as signed divisions.
6344 if (TwoA.isMinValue()) {
6345 const SCEV *CNC = SE.getCouldNotCompute();
6346 return std::make_pair(CNC, CNC);
6349 LLVMContext &Context = SE.getContext();
6351 ConstantInt *Solution1 =
6352 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
6353 ConstantInt *Solution2 =
6354 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
6356 return std::make_pair(SE.getConstant(Solution1),
6357 SE.getConstant(Solution2));
6358 } // end APIntOps namespace
6361 /// HowFarToZero - Return the number of times a backedge comparing the specified
6362 /// value to zero will execute. If not computable, return CouldNotCompute.
6364 /// This is only used for loops with a "x != y" exit test. The exit condition is
6365 /// now expressed as a single expression, V = x-y. So the exit test is
6366 /// effectively V != 0. We know and take advantage of the fact that this
6367 /// expression only being used in a comparison by zero context.
6368 ScalarEvolution::ExitLimit
6369 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool ControlsExit) {
6370 // If the value is a constant
6371 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6372 // If the value is already zero, the branch will execute zero times.
6373 if (C->getValue()->isZero()) return C;
6374 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6377 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
6378 if (!AddRec || AddRec->getLoop() != L)
6379 return getCouldNotCompute();
6381 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
6382 // the quadratic equation to solve it.
6383 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
6384 std::pair<const SCEV *,const SCEV *> Roots =
6385 SolveQuadraticEquation(AddRec, *this);
6386 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
6387 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
6390 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
6391 << " sol#2: " << *R2 << "\n";
6393 // Pick the smallest positive root value.
6394 if (ConstantInt *CB =
6395 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
6398 if (!CB->getZExtValue())
6399 std::swap(R1, R2); // R1 is the minimum root now.
6401 // We can only use this value if the chrec ends up with an exact zero
6402 // value at this index. When solving for "X*X != 5", for example, we
6403 // should not accept a root of 2.
6404 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
6406 return R1; // We found a quadratic root!
6409 return getCouldNotCompute();
6412 // Otherwise we can only handle this if it is affine.
6413 if (!AddRec->isAffine())
6414 return getCouldNotCompute();
6416 // If this is an affine expression, the execution count of this branch is
6417 // the minimum unsigned root of the following equation:
6419 // Start + Step*N = 0 (mod 2^BW)
6423 // Step*N = -Start (mod 2^BW)
6425 // where BW is the common bit width of Start and Step.
6427 // Get the initial value for the loop.
6428 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
6429 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
6431 // For now we handle only constant steps.
6433 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
6434 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
6435 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
6436 // We have not yet seen any such cases.
6437 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
6438 if (!StepC || StepC->getValue()->equalsInt(0))
6439 return getCouldNotCompute();
6441 // For positive steps (counting up until unsigned overflow):
6442 // N = -Start/Step (as unsigned)
6443 // For negative steps (counting down to zero):
6445 // First compute the unsigned distance from zero in the direction of Step.
6446 bool CountDown = StepC->getValue()->getValue().isNegative();
6447 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
6449 // Handle unitary steps, which cannot wraparound.
6450 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
6451 // N = Distance (as unsigned)
6452 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
6453 ConstantRange CR = getUnsignedRange(Start);
6454 const SCEV *MaxBECount;
6455 if (!CountDown && CR.getUnsignedMin().isMinValue())
6456 // When counting up, the worst starting value is 1, not 0.
6457 MaxBECount = CR.getUnsignedMax().isMinValue()
6458 ? getConstant(APInt::getMinValue(CR.getBitWidth()))
6459 : getConstant(APInt::getMaxValue(CR.getBitWidth()));
6461 MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
6462 : -CR.getUnsignedMin());
6463 return ExitLimit(Distance, MaxBECount);
6466 // As a special case, handle the instance where Step is a positive power of
6467 // two. In this case, determining whether Step divides Distance evenly can be
6468 // done by counting and comparing the number of trailing zeros of Step and
6471 const APInt &StepV = StepC->getValue()->getValue();
6472 // StepV.isPowerOf2() returns true if StepV is an positive power of two. It
6473 // also returns true if StepV is maximally negative (eg, INT_MIN), but that
6474 // case is not handled as this code is guarded by !CountDown.
6475 if (StepV.isPowerOf2() &&
6476 GetMinTrailingZeros(Distance) >= StepV.countTrailingZeros()) {
6477 // Here we've constrained the equation to be of the form
6479 // 2^(N + k) * Distance' = (StepV == 2^N) * X (mod 2^W) ... (0)
6481 // where we're operating on a W bit wide integer domain and k is
6482 // non-negative. The smallest unsigned solution for X is the trip count.
6484 // (0) is equivalent to:
6486 // 2^(N + k) * Distance' - 2^N * X = L * 2^W
6487 // <=> 2^N(2^k * Distance' - X) = L * 2^(W - N) * 2^N
6488 // <=> 2^k * Distance' - X = L * 2^(W - N)
6489 // <=> 2^k * Distance' = L * 2^(W - N) + X ... (1)
6491 // The smallest X satisfying (1) is unsigned remainder of dividing the LHS
6494 // <=> X = 2^k * Distance' URem 2^(W - N) ... (2)
6496 // E.g. say we're solving
6498 // 2 * Val = 2 * X (in i8) ... (3)
6500 // then from (2), we get X = Val URem i8 128 (k = 0 in this case).
6502 // Note: It is tempting to solve (3) by setting X = Val, but Val is not
6503 // necessarily the smallest unsigned value of X that satisfies (3).
6504 // E.g. if Val is i8 -127 then the smallest value of X that satisfies (3)
6505 // is i8 1, not i8 -127
6507 const auto *ModuloResult = getUDivExactExpr(Distance, Step);
6509 // Since SCEV does not have a URem node, we construct one using a truncate
6510 // and a zero extend.
6512 unsigned NarrowWidth = StepV.getBitWidth() - StepV.countTrailingZeros();
6513 auto *NarrowTy = IntegerType::get(getContext(), NarrowWidth);
6514 auto *WideTy = Distance->getType();
6516 return getZeroExtendExpr(getTruncateExpr(ModuloResult, NarrowTy), WideTy);
6520 // If the condition controls loop exit (the loop exits only if the expression
6521 // is true) and the addition is no-wrap we can use unsigned divide to
6522 // compute the backedge count. In this case, the step may not divide the
6523 // distance, but we don't care because if the condition is "missed" the loop
6524 // will have undefined behavior due to wrapping.
6525 if (ControlsExit && AddRec->getNoWrapFlags(SCEV::FlagNW)) {
6527 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6528 return ExitLimit(Exact, Exact);
6531 // Then, try to solve the above equation provided that Start is constant.
6532 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
6533 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
6534 -StartC->getValue()->getValue(),
6536 return getCouldNotCompute();
6539 /// HowFarToNonZero - Return the number of times a backedge checking the
6540 /// specified value for nonzero will execute. If not computable, return
6542 ScalarEvolution::ExitLimit
6543 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
6544 // Loops that look like: while (X == 0) are very strange indeed. We don't
6545 // handle them yet except for the trivial case. This could be expanded in the
6546 // future as needed.
6548 // If the value is a constant, check to see if it is known to be non-zero
6549 // already. If so, the backedge will execute zero times.
6550 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6551 if (!C->getValue()->isNullValue())
6552 return getZero(C->getType());
6553 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6556 // We could implement others, but I really doubt anyone writes loops like
6557 // this, and if they did, they would already be constant folded.
6558 return getCouldNotCompute();
6561 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
6562 /// (which may not be an immediate predecessor) which has exactly one
6563 /// successor from which BB is reachable, or null if no such block is
6566 std::pair<BasicBlock *, BasicBlock *>
6567 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
6568 // If the block has a unique predecessor, then there is no path from the
6569 // predecessor to the block that does not go through the direct edge
6570 // from the predecessor to the block.
6571 if (BasicBlock *Pred = BB->getSinglePredecessor())
6572 return std::make_pair(Pred, BB);
6574 // A loop's header is defined to be a block that dominates the loop.
6575 // If the header has a unique predecessor outside the loop, it must be
6576 // a block that has exactly one successor that can reach the loop.
6577 if (Loop *L = LI.getLoopFor(BB))
6578 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
6580 return std::pair<BasicBlock *, BasicBlock *>();
6583 /// HasSameValue - SCEV structural equivalence is usually sufficient for
6584 /// testing whether two expressions are equal, however for the purposes of
6585 /// looking for a condition guarding a loop, it can be useful to be a little
6586 /// more general, since a front-end may have replicated the controlling
6589 static bool HasSameValue(const SCEV *A, const SCEV *B) {
6590 // Quick check to see if they are the same SCEV.
6591 if (A == B) return true;
6593 auto ComputesEqualValues = [](const Instruction *A, const Instruction *B) {
6594 // Not all instructions that are "identical" compute the same value. For
6595 // instance, two distinct alloca instructions allocating the same type are
6596 // identical and do not read memory; but compute distinct values.
6597 return A->isIdenticalTo(B) && (isa<BinaryOperator>(A) || isa<GetElementPtrInst>(A));
6600 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
6601 // two different instructions with the same value. Check for this case.
6602 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
6603 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
6604 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
6605 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
6606 if (ComputesEqualValues(AI, BI))
6609 // Otherwise assume they may have a different value.
6613 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
6614 /// predicate Pred. Return true iff any changes were made.
6616 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
6617 const SCEV *&LHS, const SCEV *&RHS,
6619 bool Changed = false;
6621 // If we hit the max recursion limit bail out.
6625 // Canonicalize a constant to the right side.
6626 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
6627 // Check for both operands constant.
6628 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
6629 if (ConstantExpr::getICmp(Pred,
6631 RHSC->getValue())->isNullValue())
6632 goto trivially_false;
6634 goto trivially_true;
6636 // Otherwise swap the operands to put the constant on the right.
6637 std::swap(LHS, RHS);
6638 Pred = ICmpInst::getSwappedPredicate(Pred);
6642 // If we're comparing an addrec with a value which is loop-invariant in the
6643 // addrec's loop, put the addrec on the left. Also make a dominance check,
6644 // as both operands could be addrecs loop-invariant in each other's loop.
6645 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
6646 const Loop *L = AR->getLoop();
6647 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
6648 std::swap(LHS, RHS);
6649 Pred = ICmpInst::getSwappedPredicate(Pred);
6654 // If there's a constant operand, canonicalize comparisons with boundary
6655 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
6656 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
6657 const APInt &RA = RC->getValue()->getValue();
6659 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6660 case ICmpInst::ICMP_EQ:
6661 case ICmpInst::ICMP_NE:
6662 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
6664 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
6665 if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
6666 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
6667 ME->getOperand(0)->isAllOnesValue()) {
6668 RHS = AE->getOperand(1);
6669 LHS = ME->getOperand(1);
6673 case ICmpInst::ICMP_UGE:
6674 if ((RA - 1).isMinValue()) {
6675 Pred = ICmpInst::ICMP_NE;
6676 RHS = getConstant(RA - 1);
6680 if (RA.isMaxValue()) {
6681 Pred = ICmpInst::ICMP_EQ;
6685 if (RA.isMinValue()) goto trivially_true;
6687 Pred = ICmpInst::ICMP_UGT;
6688 RHS = getConstant(RA - 1);
6691 case ICmpInst::ICMP_ULE:
6692 if ((RA + 1).isMaxValue()) {
6693 Pred = ICmpInst::ICMP_NE;
6694 RHS = getConstant(RA + 1);
6698 if (RA.isMinValue()) {
6699 Pred = ICmpInst::ICMP_EQ;
6703 if (RA.isMaxValue()) goto trivially_true;
6705 Pred = ICmpInst::ICMP_ULT;
6706 RHS = getConstant(RA + 1);
6709 case ICmpInst::ICMP_SGE:
6710 if ((RA - 1).isMinSignedValue()) {
6711 Pred = ICmpInst::ICMP_NE;
6712 RHS = getConstant(RA - 1);
6716 if (RA.isMaxSignedValue()) {
6717 Pred = ICmpInst::ICMP_EQ;
6721 if (RA.isMinSignedValue()) goto trivially_true;
6723 Pred = ICmpInst::ICMP_SGT;
6724 RHS = getConstant(RA - 1);
6727 case ICmpInst::ICMP_SLE:
6728 if ((RA + 1).isMaxSignedValue()) {
6729 Pred = ICmpInst::ICMP_NE;
6730 RHS = getConstant(RA + 1);
6734 if (RA.isMinSignedValue()) {
6735 Pred = ICmpInst::ICMP_EQ;
6739 if (RA.isMaxSignedValue()) goto trivially_true;
6741 Pred = ICmpInst::ICMP_SLT;
6742 RHS = getConstant(RA + 1);
6745 case ICmpInst::ICMP_UGT:
6746 if (RA.isMinValue()) {
6747 Pred = ICmpInst::ICMP_NE;
6751 if ((RA + 1).isMaxValue()) {
6752 Pred = ICmpInst::ICMP_EQ;
6753 RHS = getConstant(RA + 1);
6757 if (RA.isMaxValue()) goto trivially_false;
6759 case ICmpInst::ICMP_ULT:
6760 if (RA.isMaxValue()) {
6761 Pred = ICmpInst::ICMP_NE;
6765 if ((RA - 1).isMinValue()) {
6766 Pred = ICmpInst::ICMP_EQ;
6767 RHS = getConstant(RA - 1);
6771 if (RA.isMinValue()) goto trivially_false;
6773 case ICmpInst::ICMP_SGT:
6774 if (RA.isMinSignedValue()) {
6775 Pred = ICmpInst::ICMP_NE;
6779 if ((RA + 1).isMaxSignedValue()) {
6780 Pred = ICmpInst::ICMP_EQ;
6781 RHS = getConstant(RA + 1);
6785 if (RA.isMaxSignedValue()) goto trivially_false;
6787 case ICmpInst::ICMP_SLT:
6788 if (RA.isMaxSignedValue()) {
6789 Pred = ICmpInst::ICMP_NE;
6793 if ((RA - 1).isMinSignedValue()) {
6794 Pred = ICmpInst::ICMP_EQ;
6795 RHS = getConstant(RA - 1);
6799 if (RA.isMinSignedValue()) goto trivially_false;
6804 // Check for obvious equality.
6805 if (HasSameValue(LHS, RHS)) {
6806 if (ICmpInst::isTrueWhenEqual(Pred))
6807 goto trivially_true;
6808 if (ICmpInst::isFalseWhenEqual(Pred))
6809 goto trivially_false;
6812 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
6813 // adding or subtracting 1 from one of the operands.
6815 case ICmpInst::ICMP_SLE:
6816 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
6817 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6819 Pred = ICmpInst::ICMP_SLT;
6821 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
6822 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6824 Pred = ICmpInst::ICMP_SLT;
6828 case ICmpInst::ICMP_SGE:
6829 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
6830 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6832 Pred = ICmpInst::ICMP_SGT;
6834 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
6835 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6837 Pred = ICmpInst::ICMP_SGT;
6841 case ICmpInst::ICMP_ULE:
6842 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
6843 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6845 Pred = ICmpInst::ICMP_ULT;
6847 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
6848 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6850 Pred = ICmpInst::ICMP_ULT;
6854 case ICmpInst::ICMP_UGE:
6855 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
6856 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6858 Pred = ICmpInst::ICMP_UGT;
6860 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
6861 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6863 Pred = ICmpInst::ICMP_UGT;
6871 // TODO: More simplifications are possible here.
6873 // Recursively simplify until we either hit a recursion limit or nothing
6876 return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1);
6882 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6883 Pred = ICmpInst::ICMP_EQ;
6888 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6889 Pred = ICmpInst::ICMP_NE;
6893 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
6894 return getSignedRange(S).getSignedMax().isNegative();
6897 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
6898 return getSignedRange(S).getSignedMin().isStrictlyPositive();
6901 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
6902 return !getSignedRange(S).getSignedMin().isNegative();
6905 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
6906 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
6909 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
6910 return isKnownNegative(S) || isKnownPositive(S);
6913 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
6914 const SCEV *LHS, const SCEV *RHS) {
6915 // Canonicalize the inputs first.
6916 (void)SimplifyICmpOperands(Pred, LHS, RHS);
6918 // If LHS or RHS is an addrec, check to see if the condition is true in
6919 // every iteration of the loop.
6920 // If LHS and RHS are both addrec, both conditions must be true in
6921 // every iteration of the loop.
6922 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
6923 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
6924 bool LeftGuarded = false;
6925 bool RightGuarded = false;
6927 const Loop *L = LAR->getLoop();
6928 if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
6929 isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
6930 if (!RAR) return true;
6935 const Loop *L = RAR->getLoop();
6936 if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
6937 isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
6938 if (!LAR) return true;
6939 RightGuarded = true;
6942 if (LeftGuarded && RightGuarded)
6945 if (isKnownPredicateViaSplitting(Pred, LHS, RHS))
6948 // Otherwise see what can be done with known constant ranges.
6949 return isKnownPredicateWithRanges(Pred, LHS, RHS);
6952 bool ScalarEvolution::isMonotonicPredicate(const SCEVAddRecExpr *LHS,
6953 ICmpInst::Predicate Pred,
6955 bool Result = isMonotonicPredicateImpl(LHS, Pred, Increasing);
6958 // Verify an invariant: inverting the predicate should turn a monotonically
6959 // increasing change to a monotonically decreasing one, and vice versa.
6960 bool IncreasingSwapped;
6961 bool ResultSwapped = isMonotonicPredicateImpl(
6962 LHS, ICmpInst::getSwappedPredicate(Pred), IncreasingSwapped);
6964 assert(Result == ResultSwapped && "should be able to analyze both!");
6966 assert(Increasing == !IncreasingSwapped &&
6967 "monotonicity should flip as we flip the predicate");
6973 bool ScalarEvolution::isMonotonicPredicateImpl(const SCEVAddRecExpr *LHS,
6974 ICmpInst::Predicate Pred,
6977 // A zero step value for LHS means the induction variable is essentially a
6978 // loop invariant value. We don't really depend on the predicate actually
6979 // flipping from false to true (for increasing predicates, and the other way
6980 // around for decreasing predicates), all we care about is that *if* the
6981 // predicate changes then it only changes from false to true.
6983 // A zero step value in itself is not very useful, but there may be places
6984 // where SCEV can prove X >= 0 but not prove X > 0, so it is helpful to be
6985 // as general as possible.
6989 return false; // Conservative answer
6991 case ICmpInst::ICMP_UGT:
6992 case ICmpInst::ICMP_UGE:
6993 case ICmpInst::ICMP_ULT:
6994 case ICmpInst::ICMP_ULE:
6995 if (!LHS->getNoWrapFlags(SCEV::FlagNUW))
6998 Increasing = Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE;
7001 case ICmpInst::ICMP_SGT:
7002 case ICmpInst::ICMP_SGE:
7003 case ICmpInst::ICMP_SLT:
7004 case ICmpInst::ICMP_SLE: {
7005 if (!LHS->getNoWrapFlags(SCEV::FlagNSW))
7008 const SCEV *Step = LHS->getStepRecurrence(*this);
7010 if (isKnownNonNegative(Step)) {
7011 Increasing = Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE;
7015 if (isKnownNonPositive(Step)) {
7016 Increasing = Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE;
7025 llvm_unreachable("switch has default clause!");
7028 bool ScalarEvolution::isLoopInvariantPredicate(
7029 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS, const Loop *L,
7030 ICmpInst::Predicate &InvariantPred, const SCEV *&InvariantLHS,
7031 const SCEV *&InvariantRHS) {
7033 // If there is a loop-invariant, force it into the RHS, otherwise bail out.
7034 if (!isLoopInvariant(RHS, L)) {
7035 if (!isLoopInvariant(LHS, L))
7038 std::swap(LHS, RHS);
7039 Pred = ICmpInst::getSwappedPredicate(Pred);
7042 const SCEVAddRecExpr *ArLHS = dyn_cast<SCEVAddRecExpr>(LHS);
7043 if (!ArLHS || ArLHS->getLoop() != L)
7047 if (!isMonotonicPredicate(ArLHS, Pred, Increasing))
7050 // If the predicate "ArLHS `Pred` RHS" monotonically increases from false to
7051 // true as the loop iterates, and the backedge is control dependent on
7052 // "ArLHS `Pred` RHS" == true then we can reason as follows:
7054 // * if the predicate was false in the first iteration then the predicate
7055 // is never evaluated again, since the loop exits without taking the
7057 // * if the predicate was true in the first iteration then it will
7058 // continue to be true for all future iterations since it is
7059 // monotonically increasing.
7061 // For both the above possibilities, we can replace the loop varying
7062 // predicate with its value on the first iteration of the loop (which is
7065 // A similar reasoning applies for a monotonically decreasing predicate, by
7066 // replacing true with false and false with true in the above two bullets.
7068 auto P = Increasing ? Pred : ICmpInst::getInversePredicate(Pred);
7070 if (!isLoopBackedgeGuardedByCond(L, P, LHS, RHS))
7073 InvariantPred = Pred;
7074 InvariantLHS = ArLHS->getStart();
7080 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
7081 const SCEV *LHS, const SCEV *RHS) {
7082 if (HasSameValue(LHS, RHS))
7083 return ICmpInst::isTrueWhenEqual(Pred);
7085 // This code is split out from isKnownPredicate because it is called from
7086 // within isLoopEntryGuardedByCond.
7089 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
7090 case ICmpInst::ICMP_SGT:
7091 std::swap(LHS, RHS);
7092 case ICmpInst::ICMP_SLT: {
7093 ConstantRange LHSRange = getSignedRange(LHS);
7094 ConstantRange RHSRange = getSignedRange(RHS);
7095 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
7097 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
7101 case ICmpInst::ICMP_SGE:
7102 std::swap(LHS, RHS);
7103 case ICmpInst::ICMP_SLE: {
7104 ConstantRange LHSRange = getSignedRange(LHS);
7105 ConstantRange RHSRange = getSignedRange(RHS);
7106 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
7108 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
7112 case ICmpInst::ICMP_UGT:
7113 std::swap(LHS, RHS);
7114 case ICmpInst::ICMP_ULT: {
7115 ConstantRange LHSRange = getUnsignedRange(LHS);
7116 ConstantRange RHSRange = getUnsignedRange(RHS);
7117 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
7119 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
7123 case ICmpInst::ICMP_UGE:
7124 std::swap(LHS, RHS);
7125 case ICmpInst::ICMP_ULE: {
7126 ConstantRange LHSRange = getUnsignedRange(LHS);
7127 ConstantRange RHSRange = getUnsignedRange(RHS);
7128 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
7130 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
7134 case ICmpInst::ICMP_NE: {
7135 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
7137 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
7140 const SCEV *Diff = getMinusSCEV(LHS, RHS);
7141 if (isKnownNonZero(Diff))
7145 case ICmpInst::ICMP_EQ:
7146 // The check at the top of the function catches the case where
7147 // the values are known to be equal.
7153 bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
7157 // Match Result to (X + Y)<ExpectedFlags> where Y is a constant integer.
7158 // Return Y via OutY.
7159 auto MatchBinaryAddToConst =
7160 [this](const SCEV *Result, const SCEV *X, APInt &OutY,
7161 SCEV::NoWrapFlags ExpectedFlags) {
7162 const SCEV *NonConstOp, *ConstOp;
7163 SCEV::NoWrapFlags FlagsPresent;
7165 if (!splitBinaryAdd(Result, ConstOp, NonConstOp, FlagsPresent) ||
7166 !isa<SCEVConstant>(ConstOp) || NonConstOp != X)
7169 OutY = cast<SCEVConstant>(ConstOp)->getValue()->getValue();
7170 return (FlagsPresent & ExpectedFlags) == ExpectedFlags;
7179 case ICmpInst::ICMP_SGE:
7180 std::swap(LHS, RHS);
7181 case ICmpInst::ICMP_SLE:
7182 // X s<= (X + C)<nsw> if C >= 0
7183 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
7186 // (X + C)<nsw> s<= X if C <= 0
7187 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) &&
7188 !C.isStrictlyPositive())
7191 case ICmpInst::ICMP_SGT:
7192 std::swap(LHS, RHS);
7193 case ICmpInst::ICMP_SLT:
7194 // X s< (X + C)<nsw> if C > 0
7195 if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) &&
7196 C.isStrictlyPositive())
7199 // (X + C)<nsw> s< X if C < 0
7200 if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
7207 bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
7210 if (Pred != ICmpInst::ICMP_ULT || ProvingSplitPredicate)
7213 // Allowing arbitrary number of activations of isKnownPredicateViaSplitting on
7214 // the stack can result in exponential time complexity.
7215 SaveAndRestore<bool> Restore(ProvingSplitPredicate, true);
7217 // If L >= 0 then I `ult` L <=> I >= 0 && I `slt` L
7219 // To prove L >= 0 we use isKnownNonNegative whereas to prove I >= 0 we use
7220 // isKnownPredicate. isKnownPredicate is more powerful, but also more
7221 // expensive; and using isKnownNonNegative(RHS) is sufficient for most of the
7222 // interesting cases seen in practice. We can consider "upgrading" L >= 0 to
7223 // use isKnownPredicate later if needed.
7224 if (isKnownNonNegative(RHS) &&
7225 isKnownPredicate(CmpInst::ICMP_SGE, LHS, getZero(LHS->getType())) &&
7226 isKnownPredicate(CmpInst::ICMP_SLT, LHS, RHS))
7232 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
7233 /// protected by a conditional between LHS and RHS. This is used to
7234 /// to eliminate casts.
7236 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
7237 ICmpInst::Predicate Pred,
7238 const SCEV *LHS, const SCEV *RHS) {
7239 // Interpret a null as meaning no loop, where there is obviously no guard
7240 // (interprocedural conditions notwithstanding).
7241 if (!L) return true;
7243 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
7245 BasicBlock *Latch = L->getLoopLatch();
7249 BranchInst *LoopContinuePredicate =
7250 dyn_cast<BranchInst>(Latch->getTerminator());
7251 if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
7252 isImpliedCond(Pred, LHS, RHS,
7253 LoopContinuePredicate->getCondition(),
7254 LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
7257 // We don't want more than one activation of the following loops on the stack
7258 // -- that can lead to O(n!) time complexity.
7259 if (WalkingBEDominatingConds)
7262 SaveAndRestore<bool> ClearOnExit(WalkingBEDominatingConds, true);
7264 // See if we can exploit a trip count to prove the predicate.
7265 const auto &BETakenInfo = getBackedgeTakenInfo(L);
7266 const SCEV *LatchBECount = BETakenInfo.getExact(Latch, this);
7267 if (LatchBECount != getCouldNotCompute()) {
7268 // We know that Latch branches back to the loop header exactly
7269 // LatchBECount times. This means the backdege condition at Latch is
7270 // equivalent to "{0,+,1} u< LatchBECount".
7271 Type *Ty = LatchBECount->getType();
7272 auto NoWrapFlags = SCEV::NoWrapFlags(SCEV::FlagNUW | SCEV::FlagNW);
7273 const SCEV *LoopCounter =
7274 getAddRecExpr(getZero(Ty), getOne(Ty), L, NoWrapFlags);
7275 if (isImpliedCond(Pred, LHS, RHS, ICmpInst::ICMP_ULT, LoopCounter,
7280 // Check conditions due to any @llvm.assume intrinsics.
7281 for (auto &AssumeVH : AC.assumptions()) {
7284 auto *CI = cast<CallInst>(AssumeVH);
7285 if (!DT.dominates(CI, Latch->getTerminator()))
7288 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
7292 // If the loop is not reachable from the entry block, we risk running into an
7293 // infinite loop as we walk up into the dom tree. These loops do not matter
7294 // anyway, so we just return a conservative answer when we see them.
7295 if (!DT.isReachableFromEntry(L->getHeader()))
7298 for (DomTreeNode *DTN = DT[Latch], *HeaderDTN = DT[L->getHeader()];
7299 DTN != HeaderDTN; DTN = DTN->getIDom()) {
7301 assert(DTN && "should reach the loop header before reaching the root!");
7303 BasicBlock *BB = DTN->getBlock();
7304 BasicBlock *PBB = BB->getSinglePredecessor();
7308 BranchInst *ContinuePredicate = dyn_cast<BranchInst>(PBB->getTerminator());
7309 if (!ContinuePredicate || !ContinuePredicate->isConditional())
7312 Value *Condition = ContinuePredicate->getCondition();
7314 // If we have an edge `E` within the loop body that dominates the only
7315 // latch, the condition guarding `E` also guards the backedge. This
7316 // reasoning works only for loops with a single latch.
7318 BasicBlockEdge DominatingEdge(PBB, BB);
7319 if (DominatingEdge.isSingleEdge()) {
7320 // We're constructively (and conservatively) enumerating edges within the
7321 // loop body that dominate the latch. The dominator tree better agree
7323 assert(DT.dominates(DominatingEdge, Latch) && "should be!");
7325 if (isImpliedCond(Pred, LHS, RHS, Condition,
7326 BB != ContinuePredicate->getSuccessor(0)))
7334 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
7335 /// by a conditional between LHS and RHS. This is used to help avoid max
7336 /// expressions in loop trip counts, and to eliminate casts.
7338 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
7339 ICmpInst::Predicate Pred,
7340 const SCEV *LHS, const SCEV *RHS) {
7341 // Interpret a null as meaning no loop, where there is obviously no guard
7342 // (interprocedural conditions notwithstanding).
7343 if (!L) return false;
7345 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
7347 // Starting at the loop predecessor, climb up the predecessor chain, as long
7348 // as there are predecessors that can be found that have unique successors
7349 // leading to the original header.
7350 for (std::pair<BasicBlock *, BasicBlock *>
7351 Pair(L->getLoopPredecessor(), L->getHeader());
7353 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
7355 BranchInst *LoopEntryPredicate =
7356 dyn_cast<BranchInst>(Pair.first->getTerminator());
7357 if (!LoopEntryPredicate ||
7358 LoopEntryPredicate->isUnconditional())
7361 if (isImpliedCond(Pred, LHS, RHS,
7362 LoopEntryPredicate->getCondition(),
7363 LoopEntryPredicate->getSuccessor(0) != Pair.second))
7367 // Check conditions due to any @llvm.assume intrinsics.
7368 for (auto &AssumeVH : AC.assumptions()) {
7371 auto *CI = cast<CallInst>(AssumeVH);
7372 if (!DT.dominates(CI, L->getHeader()))
7375 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
7382 /// RAII wrapper to prevent recursive application of isImpliedCond.
7383 /// ScalarEvolution's PendingLoopPredicates set must be empty unless we are
7384 /// currently evaluating isImpliedCond.
7385 struct MarkPendingLoopPredicate {
7387 DenseSet<Value*> &LoopPreds;
7390 MarkPendingLoopPredicate(Value *C, DenseSet<Value*> &LP)
7391 : Cond(C), LoopPreds(LP) {
7392 Pending = !LoopPreds.insert(Cond).second;
7394 ~MarkPendingLoopPredicate() {
7396 LoopPreds.erase(Cond);
7400 /// isImpliedCond - Test whether the condition described by Pred, LHS,
7401 /// and RHS is true whenever the given Cond value evaluates to true.
7402 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
7403 const SCEV *LHS, const SCEV *RHS,
7404 Value *FoundCondValue,
7406 MarkPendingLoopPredicate Mark(FoundCondValue, PendingLoopPredicates);
7410 // Recursively handle And and Or conditions.
7411 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
7412 if (BO->getOpcode() == Instruction::And) {
7414 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
7415 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
7416 } else if (BO->getOpcode() == Instruction::Or) {
7418 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
7419 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
7423 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
7424 if (!ICI) return false;
7426 // Now that we found a conditional branch that dominates the loop or controls
7427 // the loop latch. Check to see if it is the comparison we are looking for.
7428 ICmpInst::Predicate FoundPred;
7430 FoundPred = ICI->getInversePredicate();
7432 FoundPred = ICI->getPredicate();
7434 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
7435 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
7437 return isImpliedCond(Pred, LHS, RHS, FoundPred, FoundLHS, FoundRHS);
7440 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS,
7442 ICmpInst::Predicate FoundPred,
7443 const SCEV *FoundLHS,
7444 const SCEV *FoundRHS) {
7445 // Balance the types.
7446 if (getTypeSizeInBits(LHS->getType()) <
7447 getTypeSizeInBits(FoundLHS->getType())) {
7448 if (CmpInst::isSigned(Pred)) {
7449 LHS = getSignExtendExpr(LHS, FoundLHS->getType());
7450 RHS = getSignExtendExpr(RHS, FoundLHS->getType());
7452 LHS = getZeroExtendExpr(LHS, FoundLHS->getType());
7453 RHS = getZeroExtendExpr(RHS, FoundLHS->getType());
7455 } else if (getTypeSizeInBits(LHS->getType()) >
7456 getTypeSizeInBits(FoundLHS->getType())) {
7457 if (CmpInst::isSigned(FoundPred)) {
7458 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
7459 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
7461 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
7462 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
7466 // Canonicalize the query to match the way instcombine will have
7467 // canonicalized the comparison.
7468 if (SimplifyICmpOperands(Pred, LHS, RHS))
7470 return CmpInst::isTrueWhenEqual(Pred);
7471 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
7472 if (FoundLHS == FoundRHS)
7473 return CmpInst::isFalseWhenEqual(FoundPred);
7475 // Check to see if we can make the LHS or RHS match.
7476 if (LHS == FoundRHS || RHS == FoundLHS) {
7477 if (isa<SCEVConstant>(RHS)) {
7478 std::swap(FoundLHS, FoundRHS);
7479 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
7481 std::swap(LHS, RHS);
7482 Pred = ICmpInst::getSwappedPredicate(Pred);
7486 // Check whether the found predicate is the same as the desired predicate.
7487 if (FoundPred == Pred)
7488 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
7490 // Check whether swapping the found predicate makes it the same as the
7491 // desired predicate.
7492 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
7493 if (isa<SCEVConstant>(RHS))
7494 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
7496 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
7497 RHS, LHS, FoundLHS, FoundRHS);
7500 // Unsigned comparison is the same as signed comparison when both the operands
7501 // are non-negative.
7502 if (CmpInst::isUnsigned(FoundPred) &&
7503 CmpInst::getSignedPredicate(FoundPred) == Pred &&
7504 isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS))
7505 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
7507 // Check if we can make progress by sharpening ranges.
7508 if (FoundPred == ICmpInst::ICMP_NE &&
7509 (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
7511 const SCEVConstant *C = nullptr;
7512 const SCEV *V = nullptr;
7514 if (isa<SCEVConstant>(FoundLHS)) {
7515 C = cast<SCEVConstant>(FoundLHS);
7518 C = cast<SCEVConstant>(FoundRHS);
7522 // The guarding predicate tells us that C != V. If the known range
7523 // of V is [C, t), we can sharpen the range to [C + 1, t). The
7524 // range we consider has to correspond to same signedness as the
7525 // predicate we're interested in folding.
7527 APInt Min = ICmpInst::isSigned(Pred) ?
7528 getSignedRange(V).getSignedMin() : getUnsignedRange(V).getUnsignedMin();
7530 if (Min == C->getValue()->getValue()) {
7531 // Given (V >= Min && V != Min) we conclude V >= (Min + 1).
7532 // This is true even if (Min + 1) wraps around -- in case of
7533 // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)).
7535 APInt SharperMin = Min + 1;
7538 case ICmpInst::ICMP_SGE:
7539 case ICmpInst::ICMP_UGE:
7540 // We know V `Pred` SharperMin. If this implies LHS `Pred`
7542 if (isImpliedCondOperands(Pred, LHS, RHS, V,
7543 getConstant(SharperMin)))
7546 case ICmpInst::ICMP_SGT:
7547 case ICmpInst::ICMP_UGT:
7548 // We know from the range information that (V `Pred` Min ||
7549 // V == Min). We know from the guarding condition that !(V
7550 // == Min). This gives us
7552 // V `Pred` Min || V == Min && !(V == Min)
7555 // If V `Pred` Min implies LHS `Pred` RHS, we're done.
7557 if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
7567 // Check whether the actual condition is beyond sufficient.
7568 if (FoundPred == ICmpInst::ICMP_EQ)
7569 if (ICmpInst::isTrueWhenEqual(Pred))
7570 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
7572 if (Pred == ICmpInst::ICMP_NE)
7573 if (!ICmpInst::isTrueWhenEqual(FoundPred))
7574 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
7577 // Otherwise assume the worst.
7581 bool ScalarEvolution::splitBinaryAdd(const SCEV *Expr,
7582 const SCEV *&L, const SCEV *&R,
7583 SCEV::NoWrapFlags &Flags) {
7584 const auto *AE = dyn_cast<SCEVAddExpr>(Expr);
7585 if (!AE || AE->getNumOperands() != 2)
7588 L = AE->getOperand(0);
7589 R = AE->getOperand(1);
7590 Flags = AE->getNoWrapFlags();
7594 bool ScalarEvolution::computeConstantDifference(const SCEV *Less,
7597 // We avoid subtracting expressions here because this function is usually
7598 // fairly deep in the call stack (i.e. is called many times).
7600 if (isa<SCEVAddRecExpr>(Less) && isa<SCEVAddRecExpr>(More)) {
7601 const auto *LAR = cast<SCEVAddRecExpr>(Less);
7602 const auto *MAR = cast<SCEVAddRecExpr>(More);
7604 if (LAR->getLoop() != MAR->getLoop())
7607 // We look at affine expressions only; not for correctness but to keep
7608 // getStepRecurrence cheap.
7609 if (!LAR->isAffine() || !MAR->isAffine())
7612 if (LAR->getStepRecurrence(*this) != MAR->getStepRecurrence(*this))
7615 Less = LAR->getStart();
7616 More = MAR->getStart();
7621 if (isa<SCEVConstant>(Less) && isa<SCEVConstant>(More)) {
7622 const auto &M = cast<SCEVConstant>(More)->getValue()->getValue();
7623 const auto &L = cast<SCEVConstant>(Less)->getValue()->getValue();
7629 SCEV::NoWrapFlags Flags;
7630 if (splitBinaryAdd(Less, L, R, Flags))
7631 if (const auto *LC = dyn_cast<SCEVConstant>(L))
7633 C = -(LC->getValue()->getValue());
7637 if (splitBinaryAdd(More, L, R, Flags))
7638 if (const auto *LC = dyn_cast<SCEVConstant>(L))
7640 C = LC->getValue()->getValue();
7647 bool ScalarEvolution::isImpliedCondOperandsViaNoOverflow(
7648 ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS,
7649 const SCEV *FoundLHS, const SCEV *FoundRHS) {
7650 if (Pred != CmpInst::ICMP_SLT && Pred != CmpInst::ICMP_ULT)
7653 const auto *AddRecLHS = dyn_cast<SCEVAddRecExpr>(LHS);
7657 const auto *AddRecFoundLHS = dyn_cast<SCEVAddRecExpr>(FoundLHS);
7658 if (!AddRecFoundLHS)
7661 // We'd like to let SCEV reason about control dependencies, so we constrain
7662 // both the inequalities to be about add recurrences on the same loop. This
7663 // way we can use isLoopEntryGuardedByCond later.
7665 const Loop *L = AddRecFoundLHS->getLoop();
7666 if (L != AddRecLHS->getLoop())
7669 // FoundLHS u< FoundRHS u< -C => (FoundLHS + C) u< (FoundRHS + C) ... (1)
7671 // FoundLHS s< FoundRHS s< INT_MIN - C => (FoundLHS + C) s< (FoundRHS + C)
7674 // Informal proof for (2), assuming (1) [*]:
7676 // We'll also assume (A s< B) <=> ((A + INT_MIN) u< (B + INT_MIN)) ... (3)[**]
7680 // FoundLHS s< FoundRHS s< INT_MIN - C
7681 // <=> (FoundLHS + INT_MIN) u< (FoundRHS + INT_MIN) u< -C [ using (3) ]
7682 // <=> (FoundLHS + INT_MIN + C) u< (FoundRHS + INT_MIN + C) [ using (1) ]
7683 // <=> (FoundLHS + INT_MIN + C + INT_MIN) s<
7684 // (FoundRHS + INT_MIN + C + INT_MIN) [ using (3) ]
7685 // <=> FoundLHS + C s< FoundRHS + C
7687 // [*]: (1) can be proved by ruling out overflow.
7689 // [**]: This can be proved by analyzing all the four possibilities:
7690 // (A s< 0, B s< 0), (A s< 0, B s>= 0), (A s>= 0, B s< 0) and
7691 // (A s>= 0, B s>= 0).
7694 // Despite (2), "FoundRHS s< INT_MIN - C" does not mean that "FoundRHS + C"
7695 // will not sign underflow. For instance, say FoundLHS = (i8 -128), FoundRHS
7696 // = (i8 -127) and C = (i8 -100). Then INT_MIN - C = (i8 -28), and FoundRHS
7697 // s< (INT_MIN - C). Lack of sign overflow / underflow in "FoundRHS + C" is
7698 // neither necessary nor sufficient to prove "(FoundLHS + C) s< (FoundRHS +
7702 if (!computeConstantDifference(FoundLHS, LHS, LDiff) ||
7703 !computeConstantDifference(FoundRHS, RHS, RDiff) ||
7710 APInt FoundRHSLimit;
7712 if (Pred == CmpInst::ICMP_ULT) {
7713 FoundRHSLimit = -RDiff;
7715 assert(Pred == CmpInst::ICMP_SLT && "Checked above!");
7716 FoundRHSLimit = APInt::getSignedMinValue(getTypeSizeInBits(RHS->getType())) - RDiff;
7719 // Try to prove (1) or (2), as needed.
7720 return isLoopEntryGuardedByCond(L, Pred, FoundRHS,
7721 getConstant(FoundRHSLimit));
7724 /// isImpliedCondOperands - Test whether the condition described by Pred,
7725 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
7726 /// and FoundRHS is true.
7727 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
7728 const SCEV *LHS, const SCEV *RHS,
7729 const SCEV *FoundLHS,
7730 const SCEV *FoundRHS) {
7731 if (isImpliedCondOperandsViaRanges(Pred, LHS, RHS, FoundLHS, FoundRHS))
7734 if (isImpliedCondOperandsViaNoOverflow(Pred, LHS, RHS, FoundLHS, FoundRHS))
7737 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
7738 FoundLHS, FoundRHS) ||
7739 // ~x < ~y --> x > y
7740 isImpliedCondOperandsHelper(Pred, LHS, RHS,
7741 getNotSCEV(FoundRHS),
7742 getNotSCEV(FoundLHS));
7746 /// If Expr computes ~A, return A else return nullptr
7747 static const SCEV *MatchNotExpr(const SCEV *Expr) {
7748 const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Expr);
7749 if (!Add || Add->getNumOperands() != 2 ||
7750 !Add->getOperand(0)->isAllOnesValue())
7753 const SCEVMulExpr *AddRHS = dyn_cast<SCEVMulExpr>(Add->getOperand(1));
7754 if (!AddRHS || AddRHS->getNumOperands() != 2 ||
7755 !AddRHS->getOperand(0)->isAllOnesValue())
7758 return AddRHS->getOperand(1);
7762 /// Is MaybeMaxExpr an SMax or UMax of Candidate and some other values?
7763 template<typename MaxExprType>
7764 static bool IsMaxConsistingOf(const SCEV *MaybeMaxExpr,
7765 const SCEV *Candidate) {
7766 const MaxExprType *MaxExpr = dyn_cast<MaxExprType>(MaybeMaxExpr);
7767 if (!MaxExpr) return false;
7769 auto It = std::find(MaxExpr->op_begin(), MaxExpr->op_end(), Candidate);
7770 return It != MaxExpr->op_end();
7774 /// Is MaybeMinExpr an SMin or UMin of Candidate and some other values?
7775 template<typename MaxExprType>
7776 static bool IsMinConsistingOf(ScalarEvolution &SE,
7777 const SCEV *MaybeMinExpr,
7778 const SCEV *Candidate) {
7779 const SCEV *MaybeMaxExpr = MatchNotExpr(MaybeMinExpr);
7783 return IsMaxConsistingOf<MaxExprType>(MaybeMaxExpr, SE.getNotSCEV(Candidate));
7786 static bool IsKnownPredicateViaAddRecStart(ScalarEvolution &SE,
7787 ICmpInst::Predicate Pred,
7788 const SCEV *LHS, const SCEV *RHS) {
7790 // If both sides are affine addrecs for the same loop, with equal
7791 // steps, and we know the recurrences don't wrap, then we only
7792 // need to check the predicate on the starting values.
7794 if (!ICmpInst::isRelational(Pred))
7797 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
7800 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
7803 if (LAR->getLoop() != RAR->getLoop())
7805 if (!LAR->isAffine() || !RAR->isAffine())
7808 if (LAR->getStepRecurrence(SE) != RAR->getStepRecurrence(SE))
7811 SCEV::NoWrapFlags NW = ICmpInst::isSigned(Pred) ?
7812 SCEV::FlagNSW : SCEV::FlagNUW;
7813 if (!LAR->getNoWrapFlags(NW) || !RAR->getNoWrapFlags(NW))
7816 return SE.isKnownPredicate(Pred, LAR->getStart(), RAR->getStart());
7819 /// Is LHS `Pred` RHS true on the virtue of LHS or RHS being a Min or Max
7821 static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE,
7822 ICmpInst::Predicate Pred,
7823 const SCEV *LHS, const SCEV *RHS) {
7828 case ICmpInst::ICMP_SGE:
7829 std::swap(LHS, RHS);
7831 case ICmpInst::ICMP_SLE:
7834 IsMinConsistingOf<SCEVSMaxExpr>(SE, LHS, RHS) ||
7836 IsMaxConsistingOf<SCEVSMaxExpr>(RHS, LHS);
7838 case ICmpInst::ICMP_UGE:
7839 std::swap(LHS, RHS);
7841 case ICmpInst::ICMP_ULE:
7844 IsMinConsistingOf<SCEVUMaxExpr>(SE, LHS, RHS) ||
7846 IsMaxConsistingOf<SCEVUMaxExpr>(RHS, LHS);
7849 llvm_unreachable("covered switch fell through?!");
7852 /// isImpliedCondOperandsHelper - Test whether the condition described by
7853 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
7854 /// FoundLHS, and FoundRHS is true.
7856 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
7857 const SCEV *LHS, const SCEV *RHS,
7858 const SCEV *FoundLHS,
7859 const SCEV *FoundRHS) {
7860 auto IsKnownPredicateFull =
7861 [this](ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) {
7862 return isKnownPredicateWithRanges(Pred, LHS, RHS) ||
7863 IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) ||
7864 IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) ||
7865 isKnownPredicateViaNoOverflow(Pred, LHS, RHS);
7869 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
7870 case ICmpInst::ICMP_EQ:
7871 case ICmpInst::ICMP_NE:
7872 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
7875 case ICmpInst::ICMP_SLT:
7876 case ICmpInst::ICMP_SLE:
7877 if (IsKnownPredicateFull(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
7878 IsKnownPredicateFull(ICmpInst::ICMP_SGE, RHS, FoundRHS))
7881 case ICmpInst::ICMP_SGT:
7882 case ICmpInst::ICMP_SGE:
7883 if (IsKnownPredicateFull(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
7884 IsKnownPredicateFull(ICmpInst::ICMP_SLE, RHS, FoundRHS))
7887 case ICmpInst::ICMP_ULT:
7888 case ICmpInst::ICMP_ULE:
7889 if (IsKnownPredicateFull(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
7890 IsKnownPredicateFull(ICmpInst::ICMP_UGE, RHS, FoundRHS))
7893 case ICmpInst::ICMP_UGT:
7894 case ICmpInst::ICMP_UGE:
7895 if (IsKnownPredicateFull(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
7896 IsKnownPredicateFull(ICmpInst::ICMP_ULE, RHS, FoundRHS))
7904 /// isImpliedCondOperandsViaRanges - helper function for isImpliedCondOperands.
7905 /// Tries to get cases like "X `sgt` 0 => X - 1 `sgt` -1".
7906 bool ScalarEvolution::isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred,
7909 const SCEV *FoundLHS,
7910 const SCEV *FoundRHS) {
7911 if (!isa<SCEVConstant>(RHS) || !isa<SCEVConstant>(FoundRHS))
7912 // The restriction on `FoundRHS` be lifted easily -- it exists only to
7913 // reduce the compile time impact of this optimization.
7916 const SCEVAddExpr *AddLHS = dyn_cast<SCEVAddExpr>(LHS);
7917 if (!AddLHS || AddLHS->getOperand(1) != FoundLHS ||
7918 !isa<SCEVConstant>(AddLHS->getOperand(0)))
7921 APInt ConstFoundRHS = cast<SCEVConstant>(FoundRHS)->getValue()->getValue();
7923 // `FoundLHSRange` is the range we know `FoundLHS` to be in by virtue of the
7924 // antecedent "`FoundLHS` `Pred` `FoundRHS`".
7925 ConstantRange FoundLHSRange =
7926 ConstantRange::makeAllowedICmpRegion(Pred, ConstFoundRHS);
7928 // Since `LHS` is `FoundLHS` + `AddLHS->getOperand(0)`, we can compute a range
7931 cast<SCEVConstant>(AddLHS->getOperand(0))->getValue()->getValue();
7932 ConstantRange LHSRange = FoundLHSRange.add(ConstantRange(Addend));
7934 // We can also compute the range of values for `LHS` that satisfy the
7935 // consequent, "`LHS` `Pred` `RHS`":
7936 APInt ConstRHS = cast<SCEVConstant>(RHS)->getValue()->getValue();
7937 ConstantRange SatisfyingLHSRange =
7938 ConstantRange::makeSatisfyingICmpRegion(Pred, ConstRHS);
7940 // The antecedent implies the consequent if every value of `LHS` that
7941 // satisfies the antecedent also satisfies the consequent.
7942 return SatisfyingLHSRange.contains(LHSRange);
7945 // Verify if an linear IV with positive stride can overflow when in a
7946 // less-than comparison, knowing the invariant term of the comparison, the
7947 // stride and the knowledge of NSW/NUW flags on the recurrence.
7948 bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
7949 bool IsSigned, bool NoWrap) {
7950 if (NoWrap) return false;
7952 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
7953 const SCEV *One = getOne(Stride->getType());
7956 APInt MaxRHS = getSignedRange(RHS).getSignedMax();
7957 APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
7958 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
7961 // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
7962 return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
7965 APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
7966 APInt MaxValue = APInt::getMaxValue(BitWidth);
7967 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
7970 // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
7971 return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
7974 // Verify if an linear IV with negative stride can overflow when in a
7975 // greater-than comparison, knowing the invariant term of the comparison,
7976 // the stride and the knowledge of NSW/NUW flags on the recurrence.
7977 bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
7978 bool IsSigned, bool NoWrap) {
7979 if (NoWrap) return false;
7981 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
7982 const SCEV *One = getOne(Stride->getType());
7985 APInt MinRHS = getSignedRange(RHS).getSignedMin();
7986 APInt MinValue = APInt::getSignedMinValue(BitWidth);
7987 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
7990 // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
7991 return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
7994 APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
7995 APInt MinValue = APInt::getMinValue(BitWidth);
7996 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
7999 // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
8000 return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
8003 // Compute the backedge taken count knowing the interval difference, the
8004 // stride and presence of the equality in the comparison.
8005 const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
8007 const SCEV *One = getOne(Step->getType());
8008 Delta = Equality ? getAddExpr(Delta, Step)
8009 : getAddExpr(Delta, getMinusSCEV(Step, One));
8010 return getUDivExpr(Delta, Step);
8013 /// HowManyLessThans - Return the number of times a backedge containing the
8014 /// specified less-than comparison will execute. If not computable, return
8015 /// CouldNotCompute.
8017 /// @param ControlsExit is true when the LHS < RHS condition directly controls
8018 /// the branch (loops exits only if condition is true). In this case, we can use
8019 /// NoWrapFlags to skip overflow checks.
8020 ScalarEvolution::ExitLimit
8021 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
8022 const Loop *L, bool IsSigned,
8023 bool ControlsExit) {
8024 // We handle only IV < Invariant
8025 if (!isLoopInvariant(RHS, L))
8026 return getCouldNotCompute();
8028 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
8030 // Avoid weird loops
8031 if (!IV || IV->getLoop() != L || !IV->isAffine())
8032 return getCouldNotCompute();
8034 bool NoWrap = ControlsExit &&
8035 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
8037 const SCEV *Stride = IV->getStepRecurrence(*this);
8039 // Avoid negative or zero stride values
8040 if (!isKnownPositive(Stride))
8041 return getCouldNotCompute();
8043 // Avoid proven overflow cases: this will ensure that the backedge taken count
8044 // will not generate any unsigned overflow. Relaxed no-overflow conditions
8045 // exploit NoWrapFlags, allowing to optimize in presence of undefined
8046 // behaviors like the case of C language.
8047 if (!Stride->isOne() && doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
8048 return getCouldNotCompute();
8050 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
8051 : ICmpInst::ICMP_ULT;
8052 const SCEV *Start = IV->getStart();
8053 const SCEV *End = RHS;
8054 if (!isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS)) {
8055 const SCEV *Diff = getMinusSCEV(RHS, Start);
8056 // If we have NoWrap set, then we can assume that the increment won't
8057 // overflow, in which case if RHS - Start is a constant, we don't need to
8058 // do a max operation since we can just figure it out statically
8059 if (NoWrap && isa<SCEVConstant>(Diff)) {
8060 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
8064 End = IsSigned ? getSMaxExpr(RHS, Start)
8065 : getUMaxExpr(RHS, Start);
8068 const SCEV *BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
8070 APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
8071 : getUnsignedRange(Start).getUnsignedMin();
8073 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
8074 : getUnsignedRange(Stride).getUnsignedMin();
8076 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
8077 APInt Limit = IsSigned ? APInt::getSignedMaxValue(BitWidth) - (MinStride - 1)
8078 : APInt::getMaxValue(BitWidth) - (MinStride - 1);
8080 // Although End can be a MAX expression we estimate MaxEnd considering only
8081 // the case End = RHS. This is safe because in the other case (End - Start)
8082 // is zero, leading to a zero maximum backedge taken count.
8084 IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
8085 : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
8087 const SCEV *MaxBECount;
8088 if (isa<SCEVConstant>(BECount))
8089 MaxBECount = BECount;
8091 MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
8092 getConstant(MinStride), false);
8094 if (isa<SCEVCouldNotCompute>(MaxBECount))
8095 MaxBECount = BECount;
8097 return ExitLimit(BECount, MaxBECount);
8100 ScalarEvolution::ExitLimit
8101 ScalarEvolution::HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
8102 const Loop *L, bool IsSigned,
8103 bool ControlsExit) {
8104 // We handle only IV > Invariant
8105 if (!isLoopInvariant(RHS, L))
8106 return getCouldNotCompute();
8108 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
8110 // Avoid weird loops
8111 if (!IV || IV->getLoop() != L || !IV->isAffine())
8112 return getCouldNotCompute();
8114 bool NoWrap = ControlsExit &&
8115 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
8117 const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
8119 // Avoid negative or zero stride values
8120 if (!isKnownPositive(Stride))
8121 return getCouldNotCompute();
8123 // Avoid proven overflow cases: this will ensure that the backedge taken count
8124 // will not generate any unsigned overflow. Relaxed no-overflow conditions
8125 // exploit NoWrapFlags, allowing to optimize in presence of undefined
8126 // behaviors like the case of C language.
8127 if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
8128 return getCouldNotCompute();
8130 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
8131 : ICmpInst::ICMP_UGT;
8133 const SCEV *Start = IV->getStart();
8134 const SCEV *End = RHS;
8135 if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS)) {
8136 const SCEV *Diff = getMinusSCEV(RHS, Start);
8137 // If we have NoWrap set, then we can assume that the increment won't
8138 // overflow, in which case if RHS - Start is a constant, we don't need to
8139 // do a max operation since we can just figure it out statically
8140 if (NoWrap && isa<SCEVConstant>(Diff)) {
8141 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
8142 if (!D.isNegative())
8145 End = IsSigned ? getSMinExpr(RHS, Start)
8146 : getUMinExpr(RHS, Start);
8149 const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
8151 APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
8152 : getUnsignedRange(Start).getUnsignedMax();
8154 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
8155 : getUnsignedRange(Stride).getUnsignedMin();
8157 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
8158 APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
8159 : APInt::getMinValue(BitWidth) + (MinStride - 1);
8161 // Although End can be a MIN expression we estimate MinEnd considering only
8162 // the case End = RHS. This is safe because in the other case (Start - End)
8163 // is zero, leading to a zero maximum backedge taken count.
8165 IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
8166 : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
8169 const SCEV *MaxBECount = getCouldNotCompute();
8170 if (isa<SCEVConstant>(BECount))
8171 MaxBECount = BECount;
8173 MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
8174 getConstant(MinStride), false);
8176 if (isa<SCEVCouldNotCompute>(MaxBECount))
8177 MaxBECount = BECount;
8179 return ExitLimit(BECount, MaxBECount);
8182 /// getNumIterationsInRange - Return the number of iterations of this loop that
8183 /// produce values in the specified constant range. Another way of looking at
8184 /// this is that it returns the first iteration number where the value is not in
8185 /// the condition, thus computing the exit count. If the iteration count can't
8186 /// be computed, an instance of SCEVCouldNotCompute is returned.
8187 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
8188 ScalarEvolution &SE) const {
8189 if (Range.isFullSet()) // Infinite loop.
8190 return SE.getCouldNotCompute();
8192 // If the start is a non-zero constant, shift the range to simplify things.
8193 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
8194 if (!SC->getValue()->isZero()) {
8195 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
8196 Operands[0] = SE.getZero(SC->getType());
8197 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
8198 getNoWrapFlags(FlagNW));
8199 if (const auto *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
8200 return ShiftedAddRec->getNumIterationsInRange(
8201 Range.subtract(SC->getValue()->getValue()), SE);
8202 // This is strange and shouldn't happen.
8203 return SE.getCouldNotCompute();
8206 // The only time we can solve this is when we have all constant indices.
8207 // Otherwise, we cannot determine the overflow conditions.
8208 if (std::any_of(op_begin(), op_end(),
8209 [](const SCEV *Op) { return !isa<SCEVConstant>(Op);}))
8210 return SE.getCouldNotCompute();
8212 // Okay at this point we know that all elements of the chrec are constants and
8213 // that the start element is zero.
8215 // First check to see if the range contains zero. If not, the first
8217 unsigned BitWidth = SE.getTypeSizeInBits(getType());
8218 if (!Range.contains(APInt(BitWidth, 0)))
8219 return SE.getZero(getType());
8222 // If this is an affine expression then we have this situation:
8223 // Solve {0,+,A} in Range === Ax in Range
8225 // We know that zero is in the range. If A is positive then we know that
8226 // the upper value of the range must be the first possible exit value.
8227 // If A is negative then the lower of the range is the last possible loop
8228 // value. Also note that we already checked for a full range.
8229 APInt One(BitWidth,1);
8230 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
8231 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
8233 // The exit value should be (End+A)/A.
8234 APInt ExitVal = (End + A).udiv(A);
8235 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
8237 // Evaluate at the exit value. If we really did fall out of the valid
8238 // range, then we computed our trip count, otherwise wrap around or other
8239 // things must have happened.
8240 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
8241 if (Range.contains(Val->getValue()))
8242 return SE.getCouldNotCompute(); // Something strange happened
8244 // Ensure that the previous value is in the range. This is a sanity check.
8245 assert(Range.contains(
8246 EvaluateConstantChrecAtConstant(this,
8247 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
8248 "Linear scev computation is off in a bad way!");
8249 return SE.getConstant(ExitValue);
8250 } else if (isQuadratic()) {
8251 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
8252 // quadratic equation to solve it. To do this, we must frame our problem in
8253 // terms of figuring out when zero is crossed, instead of when
8254 // Range.getUpper() is crossed.
8255 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
8256 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
8257 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
8258 // getNoWrapFlags(FlagNW)
8261 // Next, solve the constructed addrec
8262 std::pair<const SCEV *,const SCEV *> Roots =
8263 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
8264 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
8265 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
8267 // Pick the smallest positive root value.
8268 if (ConstantInt *CB =
8269 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
8270 R1->getValue(), R2->getValue()))) {
8271 if (!CB->getZExtValue())
8272 std::swap(R1, R2); // R1 is the minimum root now.
8274 // Make sure the root is not off by one. The returned iteration should
8275 // not be in the range, but the previous one should be. When solving
8276 // for "X*X < 5", for example, we should not return a root of 2.
8277 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
8280 if (Range.contains(R1Val->getValue())) {
8281 // The next iteration must be out of the range...
8282 ConstantInt *NextVal =
8283 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
8285 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
8286 if (!Range.contains(R1Val->getValue()))
8287 return SE.getConstant(NextVal);
8288 return SE.getCouldNotCompute(); // Something strange happened
8291 // If R1 was not in the range, then it is a good return value. Make
8292 // sure that R1-1 WAS in the range though, just in case.
8293 ConstantInt *NextVal =
8294 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
8295 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
8296 if (Range.contains(R1Val->getValue()))
8298 return SE.getCouldNotCompute(); // Something strange happened
8303 return SE.getCouldNotCompute();
8309 FindUndefs() : Found(false) {}
8311 bool follow(const SCEV *S) {
8312 if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
8313 if (isa<UndefValue>(C->getValue()))
8315 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
8316 if (isa<UndefValue>(C->getValue()))
8320 // Keep looking if we haven't found it yet.
8323 bool isDone() const {
8324 // Stop recursion if we have found an undef.
8330 // Return true when S contains at least an undef value.
8332 containsUndefs(const SCEV *S) {
8334 SCEVTraversal<FindUndefs> ST(F);
8341 // Collect all steps of SCEV expressions.
8342 struct SCEVCollectStrides {
8343 ScalarEvolution &SE;
8344 SmallVectorImpl<const SCEV *> &Strides;
8346 SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
8347 : SE(SE), Strides(S) {}
8349 bool follow(const SCEV *S) {
8350 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
8351 Strides.push_back(AR->getStepRecurrence(SE));
8354 bool isDone() const { return false; }
8357 // Collect all SCEVUnknown and SCEVMulExpr expressions.
8358 struct SCEVCollectTerms {
8359 SmallVectorImpl<const SCEV *> &Terms;
8361 SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
8364 bool follow(const SCEV *S) {
8365 if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S)) {
8366 if (!containsUndefs(S))
8369 // Stop recursion: once we collected a term, do not walk its operands.
8376 bool isDone() const { return false; }
8379 // Check if a SCEV contains an AddRecExpr.
8380 struct SCEVHasAddRec {
8381 bool &ContainsAddRec;
8383 SCEVHasAddRec(bool &ContainsAddRec) : ContainsAddRec(ContainsAddRec) {
8384 ContainsAddRec = false;
8387 bool follow(const SCEV *S) {
8388 if (isa<SCEVAddRecExpr>(S)) {
8389 ContainsAddRec = true;
8391 // Stop recursion: once we collected a term, do not walk its operands.
8398 bool isDone() const { return false; }
8401 // Find factors that are multiplied with an expression that (possibly as a
8402 // subexpression) contains an AddRecExpr. In the expression:
8404 // 8 * (100 + %p * %q * (%a + {0, +, 1}_loop))
8406 // "%p * %q" are factors multiplied by the expression "(%a + {0, +, 1}_loop)"
8407 // that contains the AddRec {0, +, 1}_loop. %p * %q are likely to be array size
8408 // parameters as they form a product with an induction variable.
8410 // This collector expects all array size parameters to be in the same MulExpr.
8411 // It might be necessary to later add support for collecting parameters that are
8412 // spread over different nested MulExpr.
8413 struct SCEVCollectAddRecMultiplies {
8414 SmallVectorImpl<const SCEV *> &Terms;
8415 ScalarEvolution &SE;
8417 SCEVCollectAddRecMultiplies(SmallVectorImpl<const SCEV *> &T, ScalarEvolution &SE)
8418 : Terms(T), SE(SE) {}
8420 bool follow(const SCEV *S) {
8421 if (auto *Mul = dyn_cast<SCEVMulExpr>(S)) {
8422 bool HasAddRec = false;
8423 SmallVector<const SCEV *, 0> Operands;
8424 for (auto Op : Mul->operands()) {
8425 if (isa<SCEVUnknown>(Op)) {
8426 Operands.push_back(Op);
8428 bool ContainsAddRec;
8429 SCEVHasAddRec ContiansAddRec(ContainsAddRec);
8430 visitAll(Op, ContiansAddRec);
8431 HasAddRec |= ContainsAddRec;
8434 if (Operands.size() == 0)
8440 Terms.push_back(SE.getMulExpr(Operands));
8441 // Stop recursion: once we collected a term, do not walk its operands.
8448 bool isDone() const { return false; }
8452 /// Find parametric terms in this SCEVAddRecExpr. We first for parameters in
8454 /// 1) The strides of AddRec expressions.
8455 /// 2) Unknowns that are multiplied with AddRec expressions.
8456 void ScalarEvolution::collectParametricTerms(const SCEV *Expr,
8457 SmallVectorImpl<const SCEV *> &Terms) {
8458 SmallVector<const SCEV *, 4> Strides;
8459 SCEVCollectStrides StrideCollector(*this, Strides);
8460 visitAll(Expr, StrideCollector);
8463 dbgs() << "Strides:\n";
8464 for (const SCEV *S : Strides)
8465 dbgs() << *S << "\n";
8468 for (const SCEV *S : Strides) {
8469 SCEVCollectTerms TermCollector(Terms);
8470 visitAll(S, TermCollector);
8474 dbgs() << "Terms:\n";
8475 for (const SCEV *T : Terms)
8476 dbgs() << *T << "\n";
8479 SCEVCollectAddRecMultiplies MulCollector(Terms, *this);
8480 visitAll(Expr, MulCollector);
8483 static bool findArrayDimensionsRec(ScalarEvolution &SE,
8484 SmallVectorImpl<const SCEV *> &Terms,
8485 SmallVectorImpl<const SCEV *> &Sizes) {
8486 int Last = Terms.size() - 1;
8487 const SCEV *Step = Terms[Last];
8489 // End of recursion.
8491 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
8492 SmallVector<const SCEV *, 2> Qs;
8493 for (const SCEV *Op : M->operands())
8494 if (!isa<SCEVConstant>(Op))
8497 Step = SE.getMulExpr(Qs);
8500 Sizes.push_back(Step);
8504 for (const SCEV *&Term : Terms) {
8505 // Normalize the terms before the next call to findArrayDimensionsRec.
8507 SCEVDivision::divide(SE, Term, Step, &Q, &R);
8509 // Bail out when GCD does not evenly divide one of the terms.
8516 // Remove all SCEVConstants.
8517 Terms.erase(std::remove_if(Terms.begin(), Terms.end(), [](const SCEV *E) {
8518 return isa<SCEVConstant>(E);
8522 if (Terms.size() > 0)
8523 if (!findArrayDimensionsRec(SE, Terms, Sizes))
8526 Sizes.push_back(Step);
8531 struct FindParameter {
8532 bool FoundParameter;
8533 FindParameter() : FoundParameter(false) {}
8535 bool follow(const SCEV *S) {
8536 if (isa<SCEVUnknown>(S)) {
8537 FoundParameter = true;
8538 // Stop recursion: we found a parameter.
8544 bool isDone() const {
8545 // Stop recursion if we have found a parameter.
8546 return FoundParameter;
8551 // Returns true when S contains at least a SCEVUnknown parameter.
8553 containsParameters(const SCEV *S) {
8555 SCEVTraversal<FindParameter> ST(F);
8558 return F.FoundParameter;
8561 // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
8563 containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
8564 for (const SCEV *T : Terms)
8565 if (containsParameters(T))
8570 // Return the number of product terms in S.
8571 static inline int numberOfTerms(const SCEV *S) {
8572 if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
8573 return Expr->getNumOperands();
8577 static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
8578 if (isa<SCEVConstant>(T))
8581 if (isa<SCEVUnknown>(T))
8584 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
8585 SmallVector<const SCEV *, 2> Factors;
8586 for (const SCEV *Op : M->operands())
8587 if (!isa<SCEVConstant>(Op))
8588 Factors.push_back(Op);
8590 return SE.getMulExpr(Factors);
8596 /// Return the size of an element read or written by Inst.
8597 const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
8599 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
8600 Ty = Store->getValueOperand()->getType();
8601 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
8602 Ty = Load->getType();
8606 Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
8607 return getSizeOfExpr(ETy, Ty);
8610 /// Second step of delinearization: compute the array dimensions Sizes from the
8611 /// set of Terms extracted from the memory access function of this SCEVAddRec.
8612 void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
8613 SmallVectorImpl<const SCEV *> &Sizes,
8614 const SCEV *ElementSize) const {
8616 if (Terms.size() < 1 || !ElementSize)
8619 // Early return when Terms do not contain parameters: we do not delinearize
8620 // non parametric SCEVs.
8621 if (!containsParameters(Terms))
8625 dbgs() << "Terms:\n";
8626 for (const SCEV *T : Terms)
8627 dbgs() << *T << "\n";
8630 // Remove duplicates.
8631 std::sort(Terms.begin(), Terms.end());
8632 Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
8634 // Put larger terms first.
8635 std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
8636 return numberOfTerms(LHS) > numberOfTerms(RHS);
8639 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
8641 // Try to divide all terms by the element size. If term is not divisible by
8642 // element size, proceed with the original term.
8643 for (const SCEV *&Term : Terms) {
8645 SCEVDivision::divide(SE, Term, ElementSize, &Q, &R);
8650 SmallVector<const SCEV *, 4> NewTerms;
8652 // Remove constant factors.
8653 for (const SCEV *T : Terms)
8654 if (const SCEV *NewT = removeConstantFactors(SE, T))
8655 NewTerms.push_back(NewT);
8658 dbgs() << "Terms after sorting:\n";
8659 for (const SCEV *T : NewTerms)
8660 dbgs() << *T << "\n";
8663 if (NewTerms.empty() ||
8664 !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
8669 // The last element to be pushed into Sizes is the size of an element.
8670 Sizes.push_back(ElementSize);
8673 dbgs() << "Sizes:\n";
8674 for (const SCEV *S : Sizes)
8675 dbgs() << *S << "\n";
8679 /// Third step of delinearization: compute the access functions for the
8680 /// Subscripts based on the dimensions in Sizes.
8681 void ScalarEvolution::computeAccessFunctions(
8682 const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts,
8683 SmallVectorImpl<const SCEV *> &Sizes) {
8685 // Early exit in case this SCEV is not an affine multivariate function.
8689 if (auto *AR = dyn_cast<SCEVAddRecExpr>(Expr))
8690 if (!AR->isAffine())
8693 const SCEV *Res = Expr;
8694 int Last = Sizes.size() - 1;
8695 for (int i = Last; i >= 0; i--) {
8697 SCEVDivision::divide(*this, Res, Sizes[i], &Q, &R);
8700 dbgs() << "Res: " << *Res << "\n";
8701 dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
8702 dbgs() << "Res divided by Sizes[i]:\n";
8703 dbgs() << "Quotient: " << *Q << "\n";
8704 dbgs() << "Remainder: " << *R << "\n";
8709 // Do not record the last subscript corresponding to the size of elements in
8713 // Bail out if the remainder is too complex.
8714 if (isa<SCEVAddRecExpr>(R)) {
8723 // Record the access function for the current subscript.
8724 Subscripts.push_back(R);
8727 // Also push in last position the remainder of the last division: it will be
8728 // the access function of the innermost dimension.
8729 Subscripts.push_back(Res);
8731 std::reverse(Subscripts.begin(), Subscripts.end());
8734 dbgs() << "Subscripts:\n";
8735 for (const SCEV *S : Subscripts)
8736 dbgs() << *S << "\n";
8740 /// Splits the SCEV into two vectors of SCEVs representing the subscripts and
8741 /// sizes of an array access. Returns the remainder of the delinearization that
8742 /// is the offset start of the array. The SCEV->delinearize algorithm computes
8743 /// the multiples of SCEV coefficients: that is a pattern matching of sub
8744 /// expressions in the stride and base of a SCEV corresponding to the
8745 /// computation of a GCD (greatest common divisor) of base and stride. When
8746 /// SCEV->delinearize fails, it returns the SCEV unchanged.
8748 /// For example: when analyzing the memory access A[i][j][k] in this loop nest
8750 /// void foo(long n, long m, long o, double A[n][m][o]) {
8752 /// for (long i = 0; i < n; i++)
8753 /// for (long j = 0; j < m; j++)
8754 /// for (long k = 0; k < o; k++)
8755 /// A[i][j][k] = 1.0;
8758 /// the delinearization input is the following AddRec SCEV:
8760 /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
8762 /// From this SCEV, we are able to say that the base offset of the access is %A
8763 /// because it appears as an offset that does not divide any of the strides in
8766 /// CHECK: Base offset: %A
8768 /// and then SCEV->delinearize determines the size of some of the dimensions of
8769 /// the array as these are the multiples by which the strides are happening:
8771 /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
8773 /// Note that the outermost dimension remains of UnknownSize because there are
8774 /// no strides that would help identifying the size of the last dimension: when
8775 /// the array has been statically allocated, one could compute the size of that
8776 /// dimension by dividing the overall size of the array by the size of the known
8777 /// dimensions: %m * %o * 8.
8779 /// Finally delinearize provides the access functions for the array reference
8780 /// that does correspond to A[i][j][k] of the above C testcase:
8782 /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
8784 /// The testcases are checking the output of a function pass:
8785 /// DelinearizationPass that walks through all loads and stores of a function
8786 /// asking for the SCEV of the memory access with respect to all enclosing
8787 /// loops, calling SCEV->delinearize on that and printing the results.
8789 void ScalarEvolution::delinearize(const SCEV *Expr,
8790 SmallVectorImpl<const SCEV *> &Subscripts,
8791 SmallVectorImpl<const SCEV *> &Sizes,
8792 const SCEV *ElementSize) {
8793 // First step: collect parametric terms.
8794 SmallVector<const SCEV *, 4> Terms;
8795 collectParametricTerms(Expr, Terms);
8800 // Second step: find subscript sizes.
8801 findArrayDimensions(Terms, Sizes, ElementSize);
8806 // Third step: compute the access functions for each subscript.
8807 computeAccessFunctions(Expr, Subscripts, Sizes);
8809 if (Subscripts.empty())
8813 dbgs() << "succeeded to delinearize " << *Expr << "\n";
8814 dbgs() << "ArrayDecl[UnknownSize]";
8815 for (const SCEV *S : Sizes)
8816 dbgs() << "[" << *S << "]";
8818 dbgs() << "\nArrayRef";
8819 for (const SCEV *S : Subscripts)
8820 dbgs() << "[" << *S << "]";
8825 //===----------------------------------------------------------------------===//
8826 // SCEVCallbackVH Class Implementation
8827 //===----------------------------------------------------------------------===//
8829 void ScalarEvolution::SCEVCallbackVH::deleted() {
8830 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
8831 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
8832 SE->ConstantEvolutionLoopExitValue.erase(PN);
8833 SE->ValueExprMap.erase(getValPtr());
8834 // this now dangles!
8837 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
8838 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
8840 // Forget all the expressions associated with users of the old value,
8841 // so that future queries will recompute the expressions using the new
8843 Value *Old = getValPtr();
8844 SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
8845 SmallPtrSet<User *, 8> Visited;
8846 while (!Worklist.empty()) {
8847 User *U = Worklist.pop_back_val();
8848 // Deleting the Old value will cause this to dangle. Postpone
8849 // that until everything else is done.
8852 if (!Visited.insert(U).second)
8854 if (PHINode *PN = dyn_cast<PHINode>(U))
8855 SE->ConstantEvolutionLoopExitValue.erase(PN);
8856 SE->ValueExprMap.erase(U);
8857 Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
8859 // Delete the Old value.
8860 if (PHINode *PN = dyn_cast<PHINode>(Old))
8861 SE->ConstantEvolutionLoopExitValue.erase(PN);
8862 SE->ValueExprMap.erase(Old);
8863 // this now dangles!
8866 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
8867 : CallbackVH(V), SE(se) {}
8869 //===----------------------------------------------------------------------===//
8870 // ScalarEvolution Class Implementation
8871 //===----------------------------------------------------------------------===//
8873 ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI,
8874 AssumptionCache &AC, DominatorTree &DT,
8876 : F(F), TLI(TLI), AC(AC), DT(DT), LI(LI),
8877 CouldNotCompute(new SCEVCouldNotCompute()),
8878 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
8879 ValuesAtScopes(64), LoopDispositions(64), BlockDispositions(64),
8880 FirstUnknown(nullptr) {}
8882 ScalarEvolution::ScalarEvolution(ScalarEvolution &&Arg)
8883 : F(Arg.F), TLI(Arg.TLI), AC(Arg.AC), DT(Arg.DT), LI(Arg.LI),
8884 CouldNotCompute(std::move(Arg.CouldNotCompute)),
8885 ValueExprMap(std::move(Arg.ValueExprMap)),
8886 WalkingBEDominatingConds(false), ProvingSplitPredicate(false),
8887 BackedgeTakenCounts(std::move(Arg.BackedgeTakenCounts)),
8888 ConstantEvolutionLoopExitValue(
8889 std::move(Arg.ConstantEvolutionLoopExitValue)),
8890 ValuesAtScopes(std::move(Arg.ValuesAtScopes)),
8891 LoopDispositions(std::move(Arg.LoopDispositions)),
8892 BlockDispositions(std::move(Arg.BlockDispositions)),
8893 UnsignedRanges(std::move(Arg.UnsignedRanges)),
8894 SignedRanges(std::move(Arg.SignedRanges)),
8895 UniqueSCEVs(std::move(Arg.UniqueSCEVs)),
8896 SCEVAllocator(std::move(Arg.SCEVAllocator)),
8897 FirstUnknown(Arg.FirstUnknown) {
8898 Arg.FirstUnknown = nullptr;
8901 ScalarEvolution::~ScalarEvolution() {
8902 // Iterate through all the SCEVUnknown instances and call their
8903 // destructors, so that they release their references to their values.
8904 for (SCEVUnknown *U = FirstUnknown; U;) {
8905 SCEVUnknown *Tmp = U;
8907 Tmp->~SCEVUnknown();
8909 FirstUnknown = nullptr;
8911 ValueExprMap.clear();
8913 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
8914 // that a loop had multiple computable exits.
8915 for (auto &BTCI : BackedgeTakenCounts)
8916 BTCI.second.clear();
8918 assert(PendingLoopPredicates.empty() && "isImpliedCond garbage");
8919 assert(!WalkingBEDominatingConds && "isLoopBackedgeGuardedByCond garbage!");
8920 assert(!ProvingSplitPredicate && "ProvingSplitPredicate garbage!");
8923 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
8924 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
8927 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
8929 // Print all inner loops first
8930 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
8931 PrintLoopInfo(OS, SE, *I);
8934 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
8937 SmallVector<BasicBlock *, 8> ExitBlocks;
8938 L->getExitBlocks(ExitBlocks);
8939 if (ExitBlocks.size() != 1)
8940 OS << "<multiple exits> ";
8942 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
8943 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
8945 OS << "Unpredictable backedge-taken count. ";
8950 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
8953 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
8954 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
8956 OS << "Unpredictable max backedge-taken count. ";
8962 void ScalarEvolution::print(raw_ostream &OS) const {
8963 // ScalarEvolution's implementation of the print method is to print
8964 // out SCEV values of all instructions that are interesting. Doing
8965 // this potentially causes it to create new SCEV objects though,
8966 // which technically conflicts with the const qualifier. This isn't
8967 // observable from outside the class though, so casting away the
8968 // const isn't dangerous.
8969 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
8971 OS << "Classifying expressions for: ";
8972 F.printAsOperand(OS, /*PrintType=*/false);
8974 for (Instruction &I : instructions(F))
8975 if (isSCEVable(I.getType()) && !isa<CmpInst>(I)) {
8978 const SCEV *SV = SE.getSCEV(&I);
8980 if (!isa<SCEVCouldNotCompute>(SV)) {
8982 SE.getUnsignedRange(SV).print(OS);
8984 SE.getSignedRange(SV).print(OS);
8987 const Loop *L = LI.getLoopFor(I.getParent());
8989 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
8993 if (!isa<SCEVCouldNotCompute>(AtUse)) {
8995 SE.getUnsignedRange(AtUse).print(OS);
8997 SE.getSignedRange(AtUse).print(OS);
9002 OS << "\t\t" "Exits: ";
9003 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
9004 if (!SE.isLoopInvariant(ExitValue, L)) {
9005 OS << "<<Unknown>>";
9014 OS << "Determining loop execution counts for: ";
9015 F.printAsOperand(OS, /*PrintType=*/false);
9017 for (LoopInfo::iterator I = LI.begin(), E = LI.end(); I != E; ++I)
9018 PrintLoopInfo(OS, &SE, *I);
9021 ScalarEvolution::LoopDisposition
9022 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
9023 auto &Values = LoopDispositions[S];
9024 for (auto &V : Values) {
9025 if (V.getPointer() == L)
9028 Values.emplace_back(L, LoopVariant);
9029 LoopDisposition D = computeLoopDisposition(S, L);
9030 auto &Values2 = LoopDispositions[S];
9031 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
9032 if (V.getPointer() == L) {
9040 ScalarEvolution::LoopDisposition
9041 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
9042 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
9044 return LoopInvariant;
9048 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
9049 case scAddRecExpr: {
9050 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
9052 // If L is the addrec's loop, it's computable.
9053 if (AR->getLoop() == L)
9054 return LoopComputable;
9056 // Add recurrences are never invariant in the function-body (null loop).
9060 // This recurrence is variant w.r.t. L if L contains AR's loop.
9061 if (L->contains(AR->getLoop()))
9064 // This recurrence is invariant w.r.t. L if AR's loop contains L.
9065 if (AR->getLoop()->contains(L))
9066 return LoopInvariant;
9068 // This recurrence is variant w.r.t. L if any of its operands
9070 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
9072 if (!isLoopInvariant(*I, L))
9075 // Otherwise it's loop-invariant.
9076 return LoopInvariant;
9082 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
9083 bool HasVarying = false;
9084 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
9086 LoopDisposition D = getLoopDisposition(*I, L);
9087 if (D == LoopVariant)
9089 if (D == LoopComputable)
9092 return HasVarying ? LoopComputable : LoopInvariant;
9095 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
9096 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
9097 if (LD == LoopVariant)
9099 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
9100 if (RD == LoopVariant)
9102 return (LD == LoopInvariant && RD == LoopInvariant) ?
9103 LoopInvariant : LoopComputable;
9106 // All non-instruction values are loop invariant. All instructions are loop
9107 // invariant if they are not contained in the specified loop.
9108 // Instructions are never considered invariant in the function body
9109 // (null loop) because they are defined within the "loop".
9110 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
9111 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
9112 return LoopInvariant;
9113 case scCouldNotCompute:
9114 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
9116 llvm_unreachable("Unknown SCEV kind!");
9119 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
9120 return getLoopDisposition(S, L) == LoopInvariant;
9123 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
9124 return getLoopDisposition(S, L) == LoopComputable;
9127 ScalarEvolution::BlockDisposition
9128 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
9129 auto &Values = BlockDispositions[S];
9130 for (auto &V : Values) {
9131 if (V.getPointer() == BB)
9134 Values.emplace_back(BB, DoesNotDominateBlock);
9135 BlockDisposition D = computeBlockDisposition(S, BB);
9136 auto &Values2 = BlockDispositions[S];
9137 for (auto &V : make_range(Values2.rbegin(), Values2.rend())) {
9138 if (V.getPointer() == BB) {
9146 ScalarEvolution::BlockDisposition
9147 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
9148 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
9150 return ProperlyDominatesBlock;
9154 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
9155 case scAddRecExpr: {
9156 // This uses a "dominates" query instead of "properly dominates" query
9157 // to test for proper dominance too, because the instruction which
9158 // produces the addrec's value is a PHI, and a PHI effectively properly
9159 // dominates its entire containing block.
9160 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
9161 if (!DT.dominates(AR->getLoop()->getHeader(), BB))
9162 return DoesNotDominateBlock;
9164 // FALL THROUGH into SCEVNAryExpr handling.
9169 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
9171 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
9173 BlockDisposition D = getBlockDisposition(*I, BB);
9174 if (D == DoesNotDominateBlock)
9175 return DoesNotDominateBlock;
9176 if (D == DominatesBlock)
9179 return Proper ? ProperlyDominatesBlock : DominatesBlock;
9182 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
9183 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
9184 BlockDisposition LD = getBlockDisposition(LHS, BB);
9185 if (LD == DoesNotDominateBlock)
9186 return DoesNotDominateBlock;
9187 BlockDisposition RD = getBlockDisposition(RHS, BB);
9188 if (RD == DoesNotDominateBlock)
9189 return DoesNotDominateBlock;
9190 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
9191 ProperlyDominatesBlock : DominatesBlock;
9194 if (Instruction *I =
9195 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
9196 if (I->getParent() == BB)
9197 return DominatesBlock;
9198 if (DT.properlyDominates(I->getParent(), BB))
9199 return ProperlyDominatesBlock;
9200 return DoesNotDominateBlock;
9202 return ProperlyDominatesBlock;
9203 case scCouldNotCompute:
9204 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
9206 llvm_unreachable("Unknown SCEV kind!");
9209 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
9210 return getBlockDisposition(S, BB) >= DominatesBlock;
9213 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
9214 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
9218 // Search for a SCEV expression node within an expression tree.
9219 // Implements SCEVTraversal::Visitor.
9224 SCEVSearch(const SCEV *N): Node(N), IsFound(false) {}
9226 bool follow(const SCEV *S) {
9227 IsFound |= (S == Node);
9230 bool isDone() const { return IsFound; }
9234 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
9235 SCEVSearch Search(Op);
9236 visitAll(S, Search);
9237 return Search.IsFound;
9240 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
9241 ValuesAtScopes.erase(S);
9242 LoopDispositions.erase(S);
9243 BlockDispositions.erase(S);
9244 UnsignedRanges.erase(S);
9245 SignedRanges.erase(S);
9247 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
9248 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end(); I != E; ) {
9249 BackedgeTakenInfo &BEInfo = I->second;
9250 if (BEInfo.hasOperand(S, this)) {
9252 BackedgeTakenCounts.erase(I++);
9259 typedef DenseMap<const Loop *, std::string> VerifyMap;
9261 /// replaceSubString - Replaces all occurrences of From in Str with To.
9262 static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
9264 while ((Pos = Str.find(From, Pos)) != std::string::npos) {
9265 Str.replace(Pos, From.size(), To.data(), To.size());
9270 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
9272 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
9273 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) {
9274 getLoopBackedgeTakenCounts(*I, Map, SE); // recurse.
9276 std::string &S = Map[L];
9278 raw_string_ostream OS(S);
9279 SE.getBackedgeTakenCount(L)->print(OS);
9281 // false and 0 are semantically equivalent. This can happen in dead loops.
9282 replaceSubString(OS.str(), "false", "0");
9283 // Remove wrap flags, their use in SCEV is highly fragile.
9284 // FIXME: Remove this when SCEV gets smarter about them.
9285 replaceSubString(OS.str(), "<nw>", "");
9286 replaceSubString(OS.str(), "<nsw>", "");
9287 replaceSubString(OS.str(), "<nuw>", "");
9292 void ScalarEvolution::verify() const {
9293 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
9295 // Gather stringified backedge taken counts for all loops using SCEV's caches.
9296 // FIXME: It would be much better to store actual values instead of strings,
9297 // but SCEV pointers will change if we drop the caches.
9298 VerifyMap BackedgeDumpsOld, BackedgeDumpsNew;
9299 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
9300 getLoopBackedgeTakenCounts(*I, BackedgeDumpsOld, SE);
9302 // Gather stringified backedge taken counts for all loops using a fresh
9303 // ScalarEvolution object.
9304 ScalarEvolution SE2(F, TLI, AC, DT, LI);
9305 for (LoopInfo::reverse_iterator I = LI.rbegin(), E = LI.rend(); I != E; ++I)
9306 getLoopBackedgeTakenCounts(*I, BackedgeDumpsNew, SE2);
9308 // Now compare whether they're the same with and without caches. This allows
9309 // verifying that no pass changed the cache.
9310 assert(BackedgeDumpsOld.size() == BackedgeDumpsNew.size() &&
9311 "New loops suddenly appeared!");
9313 for (VerifyMap::iterator OldI = BackedgeDumpsOld.begin(),
9314 OldE = BackedgeDumpsOld.end(),
9315 NewI = BackedgeDumpsNew.begin();
9316 OldI != OldE; ++OldI, ++NewI) {
9317 assert(OldI->first == NewI->first && "Loop order changed!");
9319 // Compare the stringified SCEVs. We don't care if undef backedgetaken count
9321 // FIXME: We currently ignore SCEV changes from/to CouldNotCompute. This
9322 // means that a pass is buggy or SCEV has to learn a new pattern but is
9323 // usually not harmful.
9324 if (OldI->second != NewI->second &&
9325 OldI->second.find("undef") == std::string::npos &&
9326 NewI->second.find("undef") == std::string::npos &&
9327 OldI->second != "***COULDNOTCOMPUTE***" &&
9328 NewI->second != "***COULDNOTCOMPUTE***") {
9329 dbgs() << "SCEVValidator: SCEV for loop '"
9330 << OldI->first->getHeader()->getName()
9331 << "' changed from '" << OldI->second
9332 << "' to '" << NewI->second << "'!\n";
9337 // TODO: Verify more things.
9340 char ScalarEvolutionAnalysis::PassID;
9342 ScalarEvolution ScalarEvolutionAnalysis::run(Function &F,
9343 AnalysisManager<Function> *AM) {
9344 return ScalarEvolution(F, AM->getResult<TargetLibraryAnalysis>(F),
9345 AM->getResult<AssumptionAnalysis>(F),
9346 AM->getResult<DominatorTreeAnalysis>(F),
9347 AM->getResult<LoopAnalysis>(F));
9351 ScalarEvolutionPrinterPass::run(Function &F, AnalysisManager<Function> *AM) {
9352 AM->getResult<ScalarEvolutionAnalysis>(F).print(OS);
9353 return PreservedAnalyses::all();
9356 INITIALIZE_PASS_BEGIN(ScalarEvolutionWrapperPass, "scalar-evolution",
9357 "Scalar Evolution Analysis", false, true)
9358 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
9359 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
9360 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
9361 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
9362 INITIALIZE_PASS_END(ScalarEvolutionWrapperPass, "scalar-evolution",
9363 "Scalar Evolution Analysis", false, true)
9364 char ScalarEvolutionWrapperPass::ID = 0;
9366 ScalarEvolutionWrapperPass::ScalarEvolutionWrapperPass() : FunctionPass(ID) {
9367 initializeScalarEvolutionWrapperPassPass(*PassRegistry::getPassRegistry());
9370 bool ScalarEvolutionWrapperPass::runOnFunction(Function &F) {
9371 SE.reset(new ScalarEvolution(
9372 F, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
9373 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
9374 getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
9375 getAnalysis<LoopInfoWrapperPass>().getLoopInfo()));
9379 void ScalarEvolutionWrapperPass::releaseMemory() { SE.reset(); }
9381 void ScalarEvolutionWrapperPass::print(raw_ostream &OS, const Module *) const {
9385 void ScalarEvolutionWrapperPass::verifyAnalysis() const {
9392 void ScalarEvolutionWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
9393 AU.setPreservesAll();
9394 AU.addRequiredTransitive<AssumptionCacheTracker>();
9395 AU.addRequiredTransitive<LoopInfoWrapperPass>();
9396 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
9397 AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();