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/STLExtras.h"
63 #include "llvm/ADT/SmallPtrSet.h"
64 #include "llvm/ADT/Statistic.h"
65 #include "llvm/Analysis/AssumptionTracker.h"
66 #include "llvm/Analysis/ConstantFolding.h"
67 #include "llvm/Analysis/InstructionSimplify.h"
68 #include "llvm/Analysis/LoopInfo.h"
69 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
70 #include "llvm/Analysis/ValueTracking.h"
71 #include "llvm/IR/ConstantRange.h"
72 #include "llvm/IR/Constants.h"
73 #include "llvm/IR/DataLayout.h"
74 #include "llvm/IR/DerivedTypes.h"
75 #include "llvm/IR/Dominators.h"
76 #include "llvm/IR/GetElementPtrTypeIterator.h"
77 #include "llvm/IR/GlobalAlias.h"
78 #include "llvm/IR/GlobalVariable.h"
79 #include "llvm/IR/InstIterator.h"
80 #include "llvm/IR/Instructions.h"
81 #include "llvm/IR/LLVMContext.h"
82 #include "llvm/IR/Operator.h"
83 #include "llvm/Support/CommandLine.h"
84 #include "llvm/Support/Debug.h"
85 #include "llvm/Support/ErrorHandling.h"
86 #include "llvm/Support/MathExtras.h"
87 #include "llvm/Support/raw_ostream.h"
88 #include "llvm/Target/TargetLibraryInfo.h"
92 #define DEBUG_TYPE "scalar-evolution"
94 STATISTIC(NumArrayLenItCounts,
95 "Number of trip counts computed with array length");
96 STATISTIC(NumTripCountsComputed,
97 "Number of loops with predictable loop counts");
98 STATISTIC(NumTripCountsNotComputed,
99 "Number of loops without predictable loop counts");
100 STATISTIC(NumBruteForceTripCountsComputed,
101 "Number of loops with trip counts computed by force");
103 static cl::opt<unsigned>
104 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
105 cl::desc("Maximum number of iterations SCEV will "
106 "symbolically execute a constant "
110 // FIXME: Enable this with XDEBUG when the test suite is clean.
112 VerifySCEV("verify-scev",
113 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
115 INITIALIZE_PASS_BEGIN(ScalarEvolution, "scalar-evolution",
116 "Scalar Evolution Analysis", false, true)
117 INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
118 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
119 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
120 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
121 INITIALIZE_PASS_END(ScalarEvolution, "scalar-evolution",
122 "Scalar Evolution Analysis", false, true)
123 char ScalarEvolution::ID = 0;
125 //===----------------------------------------------------------------------===//
126 // SCEV class definitions
127 //===----------------------------------------------------------------------===//
129 //===----------------------------------------------------------------------===//
130 // Implementation of the SCEV class.
133 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
134 void SCEV::dump() const {
140 void SCEV::print(raw_ostream &OS) const {
141 switch (static_cast<SCEVTypes>(getSCEVType())) {
143 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
146 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
147 const SCEV *Op = Trunc->getOperand();
148 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
149 << *Trunc->getType() << ")";
153 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
154 const SCEV *Op = ZExt->getOperand();
155 OS << "(zext " << *Op->getType() << " " << *Op << " to "
156 << *ZExt->getType() << ")";
160 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
161 const SCEV *Op = SExt->getOperand();
162 OS << "(sext " << *Op->getType() << " " << *Op << " to "
163 << *SExt->getType() << ")";
167 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
168 OS << "{" << *AR->getOperand(0);
169 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
170 OS << ",+," << *AR->getOperand(i);
172 if (AR->getNoWrapFlags(FlagNUW))
174 if (AR->getNoWrapFlags(FlagNSW))
176 if (AR->getNoWrapFlags(FlagNW) &&
177 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
179 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
187 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
188 const char *OpStr = nullptr;
189 switch (NAry->getSCEVType()) {
190 case scAddExpr: OpStr = " + "; break;
191 case scMulExpr: OpStr = " * "; break;
192 case scUMaxExpr: OpStr = " umax "; break;
193 case scSMaxExpr: OpStr = " smax "; break;
196 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
199 if (std::next(I) != E)
203 switch (NAry->getSCEVType()) {
206 if (NAry->getNoWrapFlags(FlagNUW))
208 if (NAry->getNoWrapFlags(FlagNSW))
214 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
215 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
219 const SCEVUnknown *U = cast<SCEVUnknown>(this);
221 if (U->isSizeOf(AllocTy)) {
222 OS << "sizeof(" << *AllocTy << ")";
225 if (U->isAlignOf(AllocTy)) {
226 OS << "alignof(" << *AllocTy << ")";
232 if (U->isOffsetOf(CTy, FieldNo)) {
233 OS << "offsetof(" << *CTy << ", ";
234 FieldNo->printAsOperand(OS, false);
239 // Otherwise just print it normally.
240 U->getValue()->printAsOperand(OS, false);
243 case scCouldNotCompute:
244 OS << "***COULDNOTCOMPUTE***";
247 llvm_unreachable("Unknown SCEV kind!");
250 Type *SCEV::getType() const {
251 switch (static_cast<SCEVTypes>(getSCEVType())) {
253 return cast<SCEVConstant>(this)->getType();
257 return cast<SCEVCastExpr>(this)->getType();
262 return cast<SCEVNAryExpr>(this)->getType();
264 return cast<SCEVAddExpr>(this)->getType();
266 return cast<SCEVUDivExpr>(this)->getType();
268 return cast<SCEVUnknown>(this)->getType();
269 case scCouldNotCompute:
270 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
272 llvm_unreachable("Unknown SCEV kind!");
275 bool SCEV::isZero() const {
276 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
277 return SC->getValue()->isZero();
281 bool SCEV::isOne() const {
282 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
283 return SC->getValue()->isOne();
287 bool SCEV::isAllOnesValue() const {
288 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
289 return SC->getValue()->isAllOnesValue();
293 /// isNonConstantNegative - Return true if the specified scev is negated, but
295 bool SCEV::isNonConstantNegative() const {
296 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
297 if (!Mul) return false;
299 // If there is a constant factor, it will be first.
300 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
301 if (!SC) return false;
303 // Return true if the value is negative, this matches things like (-42 * V).
304 return SC->getValue()->getValue().isNegative();
307 SCEVCouldNotCompute::SCEVCouldNotCompute() :
308 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
310 bool SCEVCouldNotCompute::classof(const SCEV *S) {
311 return S->getSCEVType() == scCouldNotCompute;
314 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
316 ID.AddInteger(scConstant);
319 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
320 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
321 UniqueSCEVs.InsertNode(S, IP);
325 const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
326 return getConstant(ConstantInt::get(getContext(), Val));
330 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
331 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
332 return getConstant(ConstantInt::get(ITy, V, isSigned));
335 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
336 unsigned SCEVTy, const SCEV *op, Type *ty)
337 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
339 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
340 const SCEV *op, Type *ty)
341 : SCEVCastExpr(ID, scTruncate, op, ty) {
342 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
343 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
344 "Cannot truncate non-integer value!");
347 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
348 const SCEV *op, Type *ty)
349 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
350 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
351 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
352 "Cannot zero extend non-integer value!");
355 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
356 const SCEV *op, Type *ty)
357 : SCEVCastExpr(ID, scSignExtend, op, ty) {
358 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
359 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
360 "Cannot sign extend non-integer value!");
363 void SCEVUnknown::deleted() {
364 // Clear this SCEVUnknown from various maps.
365 SE->forgetMemoizedResults(this);
367 // Remove this SCEVUnknown from the uniquing map.
368 SE->UniqueSCEVs.RemoveNode(this);
370 // Release the value.
374 void SCEVUnknown::allUsesReplacedWith(Value *New) {
375 // Clear this SCEVUnknown from various maps.
376 SE->forgetMemoizedResults(this);
378 // Remove this SCEVUnknown from the uniquing map.
379 SE->UniqueSCEVs.RemoveNode(this);
381 // Update this SCEVUnknown to point to the new value. This is needed
382 // because there may still be outstanding SCEVs which still point to
387 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
388 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
389 if (VCE->getOpcode() == Instruction::PtrToInt)
390 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
391 if (CE->getOpcode() == Instruction::GetElementPtr &&
392 CE->getOperand(0)->isNullValue() &&
393 CE->getNumOperands() == 2)
394 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
396 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
404 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
405 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
406 if (VCE->getOpcode() == Instruction::PtrToInt)
407 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
408 if (CE->getOpcode() == Instruction::GetElementPtr &&
409 CE->getOperand(0)->isNullValue()) {
411 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
412 if (StructType *STy = dyn_cast<StructType>(Ty))
413 if (!STy->isPacked() &&
414 CE->getNumOperands() == 3 &&
415 CE->getOperand(1)->isNullValue()) {
416 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
418 STy->getNumElements() == 2 &&
419 STy->getElementType(0)->isIntegerTy(1)) {
420 AllocTy = STy->getElementType(1);
429 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
430 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
431 if (VCE->getOpcode() == Instruction::PtrToInt)
432 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
433 if (CE->getOpcode() == Instruction::GetElementPtr &&
434 CE->getNumOperands() == 3 &&
435 CE->getOperand(0)->isNullValue() &&
436 CE->getOperand(1)->isNullValue()) {
438 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
439 // Ignore vector types here so that ScalarEvolutionExpander doesn't
440 // emit getelementptrs that index into vectors.
441 if (Ty->isStructTy() || Ty->isArrayTy()) {
443 FieldNo = CE->getOperand(2);
451 //===----------------------------------------------------------------------===//
453 //===----------------------------------------------------------------------===//
456 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
457 /// than the complexity of the RHS. This comparator is used to canonicalize
459 class SCEVComplexityCompare {
460 const LoopInfo *const LI;
462 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
464 // Return true or false if LHS is less than, or at least RHS, respectively.
465 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
466 return compare(LHS, RHS) < 0;
469 // Return negative, zero, or positive, if LHS is less than, equal to, or
470 // greater than RHS, respectively. A three-way result allows recursive
471 // comparisons to be more efficient.
472 int compare(const SCEV *LHS, const SCEV *RHS) const {
473 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
477 // Primarily, sort the SCEVs by their getSCEVType().
478 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
480 return (int)LType - (int)RType;
482 // Aside from the getSCEVType() ordering, the particular ordering
483 // isn't very important except that it's beneficial to be consistent,
484 // so that (a + b) and (b + a) don't end up as different expressions.
485 switch (static_cast<SCEVTypes>(LType)) {
487 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
488 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
490 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
491 // not as complete as it could be.
492 const Value *LV = LU->getValue(), *RV = RU->getValue();
494 // Order pointer values after integer values. This helps SCEVExpander
496 bool LIsPointer = LV->getType()->isPointerTy(),
497 RIsPointer = RV->getType()->isPointerTy();
498 if (LIsPointer != RIsPointer)
499 return (int)LIsPointer - (int)RIsPointer;
501 // Compare getValueID values.
502 unsigned LID = LV->getValueID(),
503 RID = RV->getValueID();
505 return (int)LID - (int)RID;
507 // Sort arguments by their position.
508 if (const Argument *LA = dyn_cast<Argument>(LV)) {
509 const Argument *RA = cast<Argument>(RV);
510 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
511 return (int)LArgNo - (int)RArgNo;
514 // For instructions, compare their loop depth, and their operand
515 // count. This is pretty loose.
516 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
517 const Instruction *RInst = cast<Instruction>(RV);
519 // Compare loop depths.
520 const BasicBlock *LParent = LInst->getParent(),
521 *RParent = RInst->getParent();
522 if (LParent != RParent) {
523 unsigned LDepth = LI->getLoopDepth(LParent),
524 RDepth = LI->getLoopDepth(RParent);
525 if (LDepth != RDepth)
526 return (int)LDepth - (int)RDepth;
529 // Compare the number of operands.
530 unsigned LNumOps = LInst->getNumOperands(),
531 RNumOps = RInst->getNumOperands();
532 return (int)LNumOps - (int)RNumOps;
539 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
540 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
542 // Compare constant values.
543 const APInt &LA = LC->getValue()->getValue();
544 const APInt &RA = RC->getValue()->getValue();
545 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
546 if (LBitWidth != RBitWidth)
547 return (int)LBitWidth - (int)RBitWidth;
548 return LA.ult(RA) ? -1 : 1;
552 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
553 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
555 // Compare addrec loop depths.
556 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
557 if (LLoop != RLoop) {
558 unsigned LDepth = LLoop->getLoopDepth(),
559 RDepth = RLoop->getLoopDepth();
560 if (LDepth != RDepth)
561 return (int)LDepth - (int)RDepth;
564 // Addrec complexity grows with operand count.
565 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
566 if (LNumOps != RNumOps)
567 return (int)LNumOps - (int)RNumOps;
569 // Lexicographically compare.
570 for (unsigned i = 0; i != LNumOps; ++i) {
571 long X = compare(LA->getOperand(i), RA->getOperand(i));
583 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
584 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
586 // Lexicographically compare n-ary expressions.
587 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
588 if (LNumOps != RNumOps)
589 return (int)LNumOps - (int)RNumOps;
591 for (unsigned i = 0; i != LNumOps; ++i) {
594 long X = compare(LC->getOperand(i), RC->getOperand(i));
598 return (int)LNumOps - (int)RNumOps;
602 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
603 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
605 // Lexicographically compare udiv expressions.
606 long X = compare(LC->getLHS(), RC->getLHS());
609 return compare(LC->getRHS(), RC->getRHS());
615 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
616 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
618 // Compare cast expressions by operand.
619 return compare(LC->getOperand(), RC->getOperand());
622 case scCouldNotCompute:
623 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
625 llvm_unreachable("Unknown SCEV kind!");
630 /// GroupByComplexity - Given a list of SCEV objects, order them by their
631 /// complexity, and group objects of the same complexity together by value.
632 /// When this routine is finished, we know that any duplicates in the vector are
633 /// consecutive and that complexity is monotonically increasing.
635 /// Note that we go take special precautions to ensure that we get deterministic
636 /// results from this routine. In other words, we don't want the results of
637 /// this to depend on where the addresses of various SCEV objects happened to
640 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
642 if (Ops.size() < 2) return; // Noop
643 if (Ops.size() == 2) {
644 // This is the common case, which also happens to be trivially simple.
646 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
647 if (SCEVComplexityCompare(LI)(RHS, LHS))
652 // Do the rough sort by complexity.
653 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
655 // Now that we are sorted by complexity, group elements of the same
656 // complexity. Note that this is, at worst, N^2, but the vector is likely to
657 // be extremely short in practice. Note that we take this approach because we
658 // do not want to depend on the addresses of the objects we are grouping.
659 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
660 const SCEV *S = Ops[i];
661 unsigned Complexity = S->getSCEVType();
663 // If there are any objects of the same complexity and same value as this
665 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
666 if (Ops[j] == S) { // Found a duplicate.
667 // Move it to immediately after i'th element.
668 std::swap(Ops[i+1], Ops[j]);
669 ++i; // no need to rescan it.
670 if (i == e-2) return; // Done!
676 static const APInt srem(const SCEVConstant *C1, const SCEVConstant *C2) {
677 APInt A = C1->getValue()->getValue();
678 APInt B = C2->getValue()->getValue();
679 uint32_t ABW = A.getBitWidth();
680 uint32_t BBW = B.getBitWidth();
687 return APIntOps::srem(A, B);
690 static const APInt sdiv(const SCEVConstant *C1, const SCEVConstant *C2) {
691 APInt A = C1->getValue()->getValue();
692 APInt B = C2->getValue()->getValue();
693 uint32_t ABW = A.getBitWidth();
694 uint32_t BBW = B.getBitWidth();
701 return APIntOps::sdiv(A, B);
705 struct FindSCEVSize {
707 FindSCEVSize() : Size(0) {}
709 bool follow(const SCEV *S) {
711 // Keep looking at all operands of S.
714 bool isDone() const {
720 // Returns the size of the SCEV S.
721 static inline int sizeOfSCEV(const SCEV *S) {
723 SCEVTraversal<FindSCEVSize> ST(F);
730 struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
732 // Computes the Quotient and Remainder of the division of Numerator by
734 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
735 const SCEV *Denominator, const SCEV **Quotient,
736 const SCEV **Remainder) {
737 assert(Numerator && Denominator && "Uninitialized SCEV");
739 SCEVDivision D(SE, Numerator, Denominator);
741 // Check for the trivial case here to avoid having to check for it in the
743 if (Numerator == Denominator) {
749 if (Numerator->isZero()) {
755 // Split the Denominator when it is a product.
756 if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
758 *Quotient = Numerator;
759 for (const SCEV *Op : T->operands()) {
760 divide(SE, *Quotient, Op, &Q, &R);
763 // Bail out when the Numerator is not divisible by one of the terms of
767 *Remainder = Numerator;
776 *Quotient = D.Quotient;
777 *Remainder = D.Remainder;
780 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator, const SCEV *Denominator)
781 : SE(S), Denominator(Denominator) {
782 Zero = SE.getConstant(Denominator->getType(), 0);
783 One = SE.getConstant(Denominator->getType(), 1);
785 // By default, we don't know how to divide Expr by Denominator.
786 // Providing the default here simplifies the rest of the code.
788 Remainder = Numerator;
791 // Except in the trivial case described above, we do not know how to divide
792 // Expr by Denominator for the following functions with empty implementation.
793 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
794 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
795 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
796 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
797 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
798 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
799 void visitUnknown(const SCEVUnknown *Numerator) {}
800 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
802 void visitConstant(const SCEVConstant *Numerator) {
803 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
804 Quotient = SE.getConstant(sdiv(Numerator, D));
805 Remainder = SE.getConstant(srem(Numerator, D));
810 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
811 const SCEV *StartQ, *StartR, *StepQ, *StepR;
812 assert(Numerator->isAffine() && "Numerator should be affine");
813 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
814 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
815 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
816 Numerator->getNoWrapFlags());
817 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
818 Numerator->getNoWrapFlags());
821 void visitAddExpr(const SCEVAddExpr *Numerator) {
822 SmallVector<const SCEV *, 2> Qs, Rs;
823 Type *Ty = Denominator->getType();
825 for (const SCEV *Op : Numerator->operands()) {
827 divide(SE, Op, Denominator, &Q, &R);
829 // Bail out if types do not match.
830 if (Ty != Q->getType() || Ty != R->getType()) {
832 Remainder = Numerator;
840 if (Qs.size() == 1) {
846 Quotient = SE.getAddExpr(Qs);
847 Remainder = SE.getAddExpr(Rs);
850 void visitMulExpr(const SCEVMulExpr *Numerator) {
851 SmallVector<const SCEV *, 2> Qs;
852 Type *Ty = Denominator->getType();
854 bool FoundDenominatorTerm = false;
855 for (const SCEV *Op : Numerator->operands()) {
856 // Bail out if types do not match.
857 if (Ty != Op->getType()) {
859 Remainder = Numerator;
863 if (FoundDenominatorTerm) {
868 // Check whether Denominator divides one of the product operands.
870 divide(SE, Op, Denominator, &Q, &R);
876 // Bail out if types do not match.
877 if (Ty != Q->getType()) {
879 Remainder = Numerator;
883 FoundDenominatorTerm = true;
887 if (FoundDenominatorTerm) {
892 Quotient = SE.getMulExpr(Qs);
896 if (!isa<SCEVUnknown>(Denominator)) {
898 Remainder = Numerator;
902 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
903 ValueToValueMap RewriteMap;
904 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
905 cast<SCEVConstant>(Zero)->getValue();
906 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
908 if (Remainder->isZero()) {
909 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
910 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
911 cast<SCEVConstant>(One)->getValue();
913 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
917 // Quotient is (Numerator - Remainder) divided by Denominator.
919 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
920 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator)) {
921 // This SCEV does not seem to simplify: fail the division here.
923 Remainder = Numerator;
926 divide(SE, Diff, Denominator, &Q, &R);
928 "(Numerator - Remainder) should evenly divide Denominator");
934 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
940 //===----------------------------------------------------------------------===//
941 // Simple SCEV method implementations
942 //===----------------------------------------------------------------------===//
944 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
946 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
949 // Handle the simplest case efficiently.
951 return SE.getTruncateOrZeroExtend(It, ResultTy);
953 // We are using the following formula for BC(It, K):
955 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
957 // Suppose, W is the bitwidth of the return value. We must be prepared for
958 // overflow. Hence, we must assure that the result of our computation is
959 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
960 // safe in modular arithmetic.
962 // However, this code doesn't use exactly that formula; the formula it uses
963 // is something like the following, where T is the number of factors of 2 in
964 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
967 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
969 // This formula is trivially equivalent to the previous formula. However,
970 // this formula can be implemented much more efficiently. The trick is that
971 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
972 // arithmetic. To do exact division in modular arithmetic, all we have
973 // to do is multiply by the inverse. Therefore, this step can be done at
976 // The next issue is how to safely do the division by 2^T. The way this
977 // is done is by doing the multiplication step at a width of at least W + T
978 // bits. This way, the bottom W+T bits of the product are accurate. Then,
979 // when we perform the division by 2^T (which is equivalent to a right shift
980 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
981 // truncated out after the division by 2^T.
983 // In comparison to just directly using the first formula, this technique
984 // is much more efficient; using the first formula requires W * K bits,
985 // but this formula less than W + K bits. Also, the first formula requires
986 // a division step, whereas this formula only requires multiplies and shifts.
988 // It doesn't matter whether the subtraction step is done in the calculation
989 // width or the input iteration count's width; if the subtraction overflows,
990 // the result must be zero anyway. We prefer here to do it in the width of
991 // the induction variable because it helps a lot for certain cases; CodeGen
992 // isn't smart enough to ignore the overflow, which leads to much less
993 // efficient code if the width of the subtraction is wider than the native
996 // (It's possible to not widen at all by pulling out factors of 2 before
997 // the multiplication; for example, K=2 can be calculated as
998 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
999 // extra arithmetic, so it's not an obvious win, and it gets
1000 // much more complicated for K > 3.)
1002 // Protection from insane SCEVs; this bound is conservative,
1003 // but it probably doesn't matter.
1005 return SE.getCouldNotCompute();
1007 unsigned W = SE.getTypeSizeInBits(ResultTy);
1009 // Calculate K! / 2^T and T; we divide out the factors of two before
1010 // multiplying for calculating K! / 2^T to avoid overflow.
1011 // Other overflow doesn't matter because we only care about the bottom
1012 // W bits of the result.
1013 APInt OddFactorial(W, 1);
1015 for (unsigned i = 3; i <= K; ++i) {
1017 unsigned TwoFactors = Mult.countTrailingZeros();
1019 Mult = Mult.lshr(TwoFactors);
1020 OddFactorial *= Mult;
1023 // We need at least W + T bits for the multiplication step
1024 unsigned CalculationBits = W + T;
1026 // Calculate 2^T, at width T+W.
1027 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1029 // Calculate the multiplicative inverse of K! / 2^T;
1030 // this multiplication factor will perform the exact division by
1032 APInt Mod = APInt::getSignedMinValue(W+1);
1033 APInt MultiplyFactor = OddFactorial.zext(W+1);
1034 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1035 MultiplyFactor = MultiplyFactor.trunc(W);
1037 // Calculate the product, at width T+W
1038 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1040 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1041 for (unsigned i = 1; i != K; ++i) {
1042 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1043 Dividend = SE.getMulExpr(Dividend,
1044 SE.getTruncateOrZeroExtend(S, CalculationTy));
1048 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1050 // Truncate the result, and divide by K! / 2^T.
1052 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1053 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1056 /// evaluateAtIteration - Return the value of this chain of recurrences at
1057 /// the specified iteration number. We can evaluate this recurrence by
1058 /// multiplying each element in the chain by the binomial coefficient
1059 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
1061 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1063 /// where BC(It, k) stands for binomial coefficient.
1065 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1066 ScalarEvolution &SE) const {
1067 const SCEV *Result = getStart();
1068 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1069 // The computation is correct in the face of overflow provided that the
1070 // multiplication is performed _after_ the evaluation of the binomial
1072 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1073 if (isa<SCEVCouldNotCompute>(Coeff))
1076 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1081 //===----------------------------------------------------------------------===//
1082 // SCEV Expression folder implementations
1083 //===----------------------------------------------------------------------===//
1085 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1087 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
1088 "This is not a truncating conversion!");
1089 assert(isSCEVable(Ty) &&
1090 "This is not a conversion to a SCEVable type!");
1091 Ty = getEffectiveSCEVType(Ty);
1093 FoldingSetNodeID ID;
1094 ID.AddInteger(scTruncate);
1098 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1100 // Fold if the operand is constant.
1101 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1103 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1105 // trunc(trunc(x)) --> trunc(x)
1106 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1107 return getTruncateExpr(ST->getOperand(), Ty);
1109 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1110 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1111 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1113 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1114 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1115 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1117 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1118 // eliminate all the truncates.
1119 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1120 SmallVector<const SCEV *, 4> Operands;
1121 bool hasTrunc = false;
1122 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1123 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1124 hasTrunc = isa<SCEVTruncateExpr>(S);
1125 Operands.push_back(S);
1128 return getAddExpr(Operands);
1129 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1132 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1133 // eliminate all the truncates.
1134 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1135 SmallVector<const SCEV *, 4> Operands;
1136 bool hasTrunc = false;
1137 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1138 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1139 hasTrunc = isa<SCEVTruncateExpr>(S);
1140 Operands.push_back(S);
1143 return getMulExpr(Operands);
1144 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1147 // If the input value is a chrec scev, truncate the chrec's operands.
1148 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1149 SmallVector<const SCEV *, 4> Operands;
1150 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1151 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
1152 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1155 // The cast wasn't folded; create an explicit cast node. We can reuse
1156 // the existing insert position since if we get here, we won't have
1157 // made any changes which would invalidate it.
1158 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1160 UniqueSCEVs.InsertNode(S, IP);
1164 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
1166 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1167 "This is not an extending conversion!");
1168 assert(isSCEVable(Ty) &&
1169 "This is not a conversion to a SCEVable type!");
1170 Ty = getEffectiveSCEVType(Ty);
1172 // Fold if the operand is constant.
1173 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1175 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1177 // zext(zext(x)) --> zext(x)
1178 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1179 return getZeroExtendExpr(SZ->getOperand(), Ty);
1181 // Before doing any expensive analysis, check to see if we've already
1182 // computed a SCEV for this Op and Ty.
1183 FoldingSetNodeID ID;
1184 ID.AddInteger(scZeroExtend);
1188 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1190 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1191 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1192 // It's possible the bits taken off by the truncate were all zero bits. If
1193 // so, we should be able to simplify this further.
1194 const SCEV *X = ST->getOperand();
1195 ConstantRange CR = getUnsignedRange(X);
1196 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1197 unsigned NewBits = getTypeSizeInBits(Ty);
1198 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1199 CR.zextOrTrunc(NewBits)))
1200 return getTruncateOrZeroExtend(X, Ty);
1203 // If the input value is a chrec scev, and we can prove that the value
1204 // did not overflow the old, smaller, value, we can zero extend all of the
1205 // operands (often constants). This allows analysis of something like
1206 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1207 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1208 if (AR->isAffine()) {
1209 const SCEV *Start = AR->getStart();
1210 const SCEV *Step = AR->getStepRecurrence(*this);
1211 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1212 const Loop *L = AR->getLoop();
1214 // If we have special knowledge that this addrec won't overflow,
1215 // we don't need to do any further analysis.
1216 if (AR->getNoWrapFlags(SCEV::FlagNUW))
1217 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1218 getZeroExtendExpr(Step, Ty),
1219 L, AR->getNoWrapFlags());
1221 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1222 // Note that this serves two purposes: It filters out loops that are
1223 // simply not analyzable, and it covers the case where this code is
1224 // being called from within backedge-taken count analysis, such that
1225 // attempting to ask for the backedge-taken count would likely result
1226 // in infinite recursion. In the later case, the analysis code will
1227 // cope with a conservative value, and it will take care to purge
1228 // that value once it has finished.
1229 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1230 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1231 // Manually compute the final value for AR, checking for
1234 // Check whether the backedge-taken count can be losslessly casted to
1235 // the addrec's type. The count is always unsigned.
1236 const SCEV *CastedMaxBECount =
1237 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1238 const SCEV *RecastedMaxBECount =
1239 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1240 if (MaxBECount == RecastedMaxBECount) {
1241 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1242 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1243 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1244 const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul), WideTy);
1245 const SCEV *WideStart = getZeroExtendExpr(Start, WideTy);
1246 const SCEV *WideMaxBECount =
1247 getZeroExtendExpr(CastedMaxBECount, WideTy);
1248 const SCEV *OperandExtendedAdd =
1249 getAddExpr(WideStart,
1250 getMulExpr(WideMaxBECount,
1251 getZeroExtendExpr(Step, WideTy)));
1252 if (ZAdd == OperandExtendedAdd) {
1253 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1254 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1255 // Return the expression with the addrec on the outside.
1256 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1257 getZeroExtendExpr(Step, Ty),
1258 L, AR->getNoWrapFlags());
1260 // Similar to above, only this time treat the step value as signed.
1261 // This covers loops that count down.
1262 OperandExtendedAdd =
1263 getAddExpr(WideStart,
1264 getMulExpr(WideMaxBECount,
1265 getSignExtendExpr(Step, WideTy)));
1266 if (ZAdd == OperandExtendedAdd) {
1267 // Cache knowledge of AR NW, which is propagated to this AddRec.
1268 // Negative step causes unsigned wrap, but it still can't self-wrap.
1269 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1270 // Return the expression with the addrec on the outside.
1271 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1272 getSignExtendExpr(Step, Ty),
1273 L, AR->getNoWrapFlags());
1277 // If the backedge is guarded by a comparison with the pre-inc value
1278 // the addrec is safe. Also, if the entry is guarded by a comparison
1279 // with the start value and the backedge is guarded by a comparison
1280 // with the post-inc value, the addrec is safe.
1281 if (isKnownPositive(Step)) {
1282 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1283 getUnsignedRange(Step).getUnsignedMax());
1284 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1285 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1286 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1287 AR->getPostIncExpr(*this), N))) {
1288 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1289 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1290 // Return the expression with the addrec on the outside.
1291 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1292 getZeroExtendExpr(Step, Ty),
1293 L, AR->getNoWrapFlags());
1295 } else if (isKnownNegative(Step)) {
1296 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1297 getSignedRange(Step).getSignedMin());
1298 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1299 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1300 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1301 AR->getPostIncExpr(*this), N))) {
1302 // Cache knowledge of AR NW, which is propagated to this AddRec.
1303 // Negative step causes unsigned wrap, but it still can't self-wrap.
1304 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1305 // Return the expression with the addrec on the outside.
1306 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1307 getSignExtendExpr(Step, Ty),
1308 L, AR->getNoWrapFlags());
1314 // The cast wasn't folded; create an explicit cast node.
1315 // Recompute the insert position, as it may have been invalidated.
1316 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1317 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1319 UniqueSCEVs.InsertNode(S, IP);
1323 // Get the limit of a recurrence such that incrementing by Step cannot cause
1324 // signed overflow as long as the value of the recurrence within the loop does
1325 // not exceed this limit before incrementing.
1326 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1327 ICmpInst::Predicate *Pred,
1328 ScalarEvolution *SE) {
1329 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1330 if (SE->isKnownPositive(Step)) {
1331 *Pred = ICmpInst::ICMP_SLT;
1332 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1333 SE->getSignedRange(Step).getSignedMax());
1335 if (SE->isKnownNegative(Step)) {
1336 *Pred = ICmpInst::ICMP_SGT;
1337 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1338 SE->getSignedRange(Step).getSignedMin());
1343 // The recurrence AR has been shown to have no signed wrap. Typically, if we can
1344 // prove NSW for AR, then we can just as easily prove NSW for its preincrement
1345 // or postincrement sibling. This allows normalizing a sign extended AddRec as
1346 // such: {sext(Step + Start),+,Step} => {(Step + sext(Start),+,Step} As a
1347 // result, the expression "Step + sext(PreIncAR)" is congruent with
1348 // "sext(PostIncAR)"
1349 static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR,
1351 ScalarEvolution *SE) {
1352 const Loop *L = AR->getLoop();
1353 const SCEV *Start = AR->getStart();
1354 const SCEV *Step = AR->getStepRecurrence(*SE);
1356 // Check for a simple looking step prior to loop entry.
1357 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1361 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1362 // subtraction is expensive. For this purpose, perform a quick and dirty
1363 // difference, by checking for Step in the operand list.
1364 SmallVector<const SCEV *, 4> DiffOps;
1365 for (const SCEV *Op : SA->operands())
1367 DiffOps.push_back(Op);
1369 if (DiffOps.size() == SA->getNumOperands())
1372 // This is a postinc AR. Check for overflow on the preinc recurrence using the
1373 // same three conditions that getSignExtendedExpr checks.
1375 // 1. NSW flags on the step increment.
1376 const SCEV *PreStart = SE->getAddExpr(DiffOps, SA->getNoWrapFlags());
1377 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1378 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1380 if (PreAR && PreAR->getNoWrapFlags(SCEV::FlagNSW))
1383 // 2. Direct overflow check on the step operation's expression.
1384 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1385 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1386 const SCEV *OperandExtendedStart =
1387 SE->getAddExpr(SE->getSignExtendExpr(PreStart, WideTy),
1388 SE->getSignExtendExpr(Step, WideTy));
1389 if (SE->getSignExtendExpr(Start, WideTy) == OperandExtendedStart) {
1390 // Cache knowledge of PreAR NSW.
1392 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(SCEV::FlagNSW);
1393 // FIXME: this optimization needs a unit test
1394 DEBUG(dbgs() << "SCEV: untested prestart overflow check\n");
1398 // 3. Loop precondition.
1399 ICmpInst::Predicate Pred;
1400 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, SE);
1402 if (OverflowLimit &&
1403 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) {
1409 // Get the normalized sign-extended expression for this AddRec's Start.
1410 static const SCEV *getSignExtendAddRecStart(const SCEVAddRecExpr *AR,
1412 ScalarEvolution *SE) {
1413 const SCEV *PreStart = getPreStartForSignExtend(AR, Ty, SE);
1415 return SE->getSignExtendExpr(AR->getStart(), Ty);
1417 return SE->getAddExpr(SE->getSignExtendExpr(AR->getStepRecurrence(*SE), Ty),
1418 SE->getSignExtendExpr(PreStart, Ty));
1421 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1423 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1424 "This is not an extending conversion!");
1425 assert(isSCEVable(Ty) &&
1426 "This is not a conversion to a SCEVable type!");
1427 Ty = getEffectiveSCEVType(Ty);
1429 // Fold if the operand is constant.
1430 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1432 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1434 // sext(sext(x)) --> sext(x)
1435 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1436 return getSignExtendExpr(SS->getOperand(), Ty);
1438 // sext(zext(x)) --> zext(x)
1439 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1440 return getZeroExtendExpr(SZ->getOperand(), Ty);
1442 // Before doing any expensive analysis, check to see if we've already
1443 // computed a SCEV for this Op and Ty.
1444 FoldingSetNodeID ID;
1445 ID.AddInteger(scSignExtend);
1449 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1451 // If the input value is provably positive, build a zext instead.
1452 if (isKnownNonNegative(Op))
1453 return getZeroExtendExpr(Op, Ty);
1455 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1456 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1457 // It's possible the bits taken off by the truncate were all sign bits. If
1458 // so, we should be able to simplify this further.
1459 const SCEV *X = ST->getOperand();
1460 ConstantRange CR = getSignedRange(X);
1461 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1462 unsigned NewBits = getTypeSizeInBits(Ty);
1463 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1464 CR.sextOrTrunc(NewBits)))
1465 return getTruncateOrSignExtend(X, Ty);
1468 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1469 if (auto SA = dyn_cast<SCEVAddExpr>(Op)) {
1470 if (SA->getNumOperands() == 2) {
1471 auto SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1472 auto SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1474 if (auto SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1475 const APInt &C1 = SC1->getValue()->getValue();
1476 const APInt &C2 = SC2->getValue()->getValue();
1477 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1478 C2.ugt(C1) && C2.isPowerOf2())
1479 return getAddExpr(getSignExtendExpr(SC1, Ty),
1480 getSignExtendExpr(SMul, Ty));
1485 // If the input value is a chrec scev, and we can prove that the value
1486 // did not overflow the old, smaller, value, we can sign extend all of the
1487 // operands (often constants). This allows analysis of something like
1488 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1489 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1490 if (AR->isAffine()) {
1491 const SCEV *Start = AR->getStart();
1492 const SCEV *Step = AR->getStepRecurrence(*this);
1493 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1494 const Loop *L = AR->getLoop();
1496 // If we have special knowledge that this addrec won't overflow,
1497 // we don't need to do any further analysis.
1498 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1499 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1500 getSignExtendExpr(Step, Ty),
1503 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1504 // Note that this serves two purposes: It filters out loops that are
1505 // simply not analyzable, and it covers the case where this code is
1506 // being called from within backedge-taken count analysis, such that
1507 // attempting to ask for the backedge-taken count would likely result
1508 // in infinite recursion. In the later case, the analysis code will
1509 // cope with a conservative value, and it will take care to purge
1510 // that value once it has finished.
1511 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1512 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1513 // Manually compute the final value for AR, checking for
1516 // Check whether the backedge-taken count can be losslessly casted to
1517 // the addrec's type. The count is always unsigned.
1518 const SCEV *CastedMaxBECount =
1519 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1520 const SCEV *RecastedMaxBECount =
1521 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1522 if (MaxBECount == RecastedMaxBECount) {
1523 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1524 // Check whether Start+Step*MaxBECount has no signed overflow.
1525 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1526 const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul), WideTy);
1527 const SCEV *WideStart = getSignExtendExpr(Start, WideTy);
1528 const SCEV *WideMaxBECount =
1529 getZeroExtendExpr(CastedMaxBECount, WideTy);
1530 const SCEV *OperandExtendedAdd =
1531 getAddExpr(WideStart,
1532 getMulExpr(WideMaxBECount,
1533 getSignExtendExpr(Step, WideTy)));
1534 if (SAdd == OperandExtendedAdd) {
1535 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1536 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1537 // Return the expression with the addrec on the outside.
1538 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1539 getSignExtendExpr(Step, Ty),
1540 L, AR->getNoWrapFlags());
1542 // Similar to above, only this time treat the step value as unsigned.
1543 // This covers loops that count up with an unsigned step.
1544 OperandExtendedAdd =
1545 getAddExpr(WideStart,
1546 getMulExpr(WideMaxBECount,
1547 getZeroExtendExpr(Step, WideTy)));
1548 if (SAdd == OperandExtendedAdd) {
1549 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1550 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1551 // Return the expression with the addrec on the outside.
1552 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1553 getZeroExtendExpr(Step, Ty),
1554 L, AR->getNoWrapFlags());
1558 // If the backedge is guarded by a comparison with the pre-inc value
1559 // the addrec is safe. Also, if the entry is guarded by a comparison
1560 // with the start value and the backedge is guarded by a comparison
1561 // with the post-inc value, the addrec is safe.
1562 ICmpInst::Predicate Pred;
1563 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, this);
1564 if (OverflowLimit &&
1565 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1566 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1567 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1569 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1570 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1571 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1572 getSignExtendExpr(Step, Ty),
1573 L, AR->getNoWrapFlags());
1576 // If Start and Step are constants, check if we can apply this
1578 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1579 auto SC1 = dyn_cast<SCEVConstant>(Start);
1580 auto SC2 = dyn_cast<SCEVConstant>(Step);
1582 const APInt &C1 = SC1->getValue()->getValue();
1583 const APInt &C2 = SC2->getValue()->getValue();
1584 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1586 Start = getSignExtendExpr(Start, Ty);
1587 const SCEV *NewAR = getAddRecExpr(getConstant(AR->getType(), 0), Step,
1588 L, AR->getNoWrapFlags());
1589 return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
1594 // The cast wasn't folded; create an explicit cast node.
1595 // Recompute the insert position, as it may have been invalidated.
1596 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1597 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1599 UniqueSCEVs.InsertNode(S, IP);
1603 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1604 /// unspecified bits out to the given type.
1606 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1608 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1609 "This is not an extending conversion!");
1610 assert(isSCEVable(Ty) &&
1611 "This is not a conversion to a SCEVable type!");
1612 Ty = getEffectiveSCEVType(Ty);
1614 // Sign-extend negative constants.
1615 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1616 if (SC->getValue()->getValue().isNegative())
1617 return getSignExtendExpr(Op, Ty);
1619 // Peel off a truncate cast.
1620 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1621 const SCEV *NewOp = T->getOperand();
1622 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1623 return getAnyExtendExpr(NewOp, Ty);
1624 return getTruncateOrNoop(NewOp, Ty);
1627 // Next try a zext cast. If the cast is folded, use it.
1628 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1629 if (!isa<SCEVZeroExtendExpr>(ZExt))
1632 // Next try a sext cast. If the cast is folded, use it.
1633 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1634 if (!isa<SCEVSignExtendExpr>(SExt))
1637 // Force the cast to be folded into the operands of an addrec.
1638 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1639 SmallVector<const SCEV *, 4> Ops;
1640 for (const SCEV *Op : AR->operands())
1641 Ops.push_back(getAnyExtendExpr(Op, Ty));
1642 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1645 // If the expression is obviously signed, use the sext cast value.
1646 if (isa<SCEVSMaxExpr>(Op))
1649 // Absent any other information, use the zext cast value.
1653 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1654 /// a list of operands to be added under the given scale, update the given
1655 /// map. This is a helper function for getAddRecExpr. As an example of
1656 /// what it does, given a sequence of operands that would form an add
1657 /// expression like this:
1659 /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
1661 /// where A and B are constants, update the map with these values:
1663 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1665 /// and add 13 + A*B*29 to AccumulatedConstant.
1666 /// This will allow getAddRecExpr to produce this:
1668 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1670 /// This form often exposes folding opportunities that are hidden in
1671 /// the original operand list.
1673 /// Return true iff it appears that any interesting folding opportunities
1674 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1675 /// the common case where no interesting opportunities are present, and
1676 /// is also used as a check to avoid infinite recursion.
1679 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1680 SmallVectorImpl<const SCEV *> &NewOps,
1681 APInt &AccumulatedConstant,
1682 const SCEV *const *Ops, size_t NumOperands,
1684 ScalarEvolution &SE) {
1685 bool Interesting = false;
1687 // Iterate over the add operands. They are sorted, with constants first.
1689 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1691 // Pull a buried constant out to the outside.
1692 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1694 AccumulatedConstant += Scale * C->getValue()->getValue();
1697 // Next comes everything else. We're especially interested in multiplies
1698 // here, but they're in the middle, so just visit the rest with one loop.
1699 for (; i != NumOperands; ++i) {
1700 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1701 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1703 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1704 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1705 // A multiplication of a constant with another add; recurse.
1706 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1708 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1709 Add->op_begin(), Add->getNumOperands(),
1712 // A multiplication of a constant with some other value. Update
1714 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1715 const SCEV *Key = SE.getMulExpr(MulOps);
1716 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1717 M.insert(std::make_pair(Key, NewScale));
1719 NewOps.push_back(Pair.first->first);
1721 Pair.first->second += NewScale;
1722 // The map already had an entry for this value, which may indicate
1723 // a folding opportunity.
1728 // An ordinary operand. Update the map.
1729 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1730 M.insert(std::make_pair(Ops[i], Scale));
1732 NewOps.push_back(Pair.first->first);
1734 Pair.first->second += Scale;
1735 // The map already had an entry for this value, which may indicate
1736 // a folding opportunity.
1746 struct APIntCompare {
1747 bool operator()(const APInt &LHS, const APInt &RHS) const {
1748 return LHS.ult(RHS);
1753 /// getAddExpr - Get a canonical add expression, or something simpler if
1755 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1756 SCEV::NoWrapFlags Flags) {
1757 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
1758 "only nuw or nsw allowed");
1759 assert(!Ops.empty() && "Cannot get empty add!");
1760 if (Ops.size() == 1) return Ops[0];
1762 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1763 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1764 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1765 "SCEVAddExpr operand types don't match!");
1768 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1770 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1771 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1772 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1774 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1775 E = Ops.end(); I != E; ++I)
1776 if (!isKnownNonNegative(*I)) {
1780 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1783 // Sort by complexity, this groups all similar expression types together.
1784 GroupByComplexity(Ops, LI);
1786 // If there are any constants, fold them together.
1788 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1790 assert(Idx < Ops.size());
1791 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1792 // We found two constants, fold them together!
1793 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1794 RHSC->getValue()->getValue());
1795 if (Ops.size() == 2) return Ops[0];
1796 Ops.erase(Ops.begin()+1); // Erase the folded element
1797 LHSC = cast<SCEVConstant>(Ops[0]);
1800 // If we are left with a constant zero being added, strip it off.
1801 if (LHSC->getValue()->isZero()) {
1802 Ops.erase(Ops.begin());
1806 if (Ops.size() == 1) return Ops[0];
1809 // Okay, check to see if the same value occurs in the operand list more than
1810 // once. If so, merge them together into an multiply expression. Since we
1811 // sorted the list, these values are required to be adjacent.
1812 Type *Ty = Ops[0]->getType();
1813 bool FoundMatch = false;
1814 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1815 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1816 // Scan ahead to count how many equal operands there are.
1818 while (i+Count != e && Ops[i+Count] == Ops[i])
1820 // Merge the values into a multiply.
1821 const SCEV *Scale = getConstant(Ty, Count);
1822 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1823 if (Ops.size() == Count)
1826 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1827 --i; e -= Count - 1;
1831 return getAddExpr(Ops, Flags);
1833 // Check for truncates. If all the operands are truncated from the same
1834 // type, see if factoring out the truncate would permit the result to be
1835 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1836 // if the contents of the resulting outer trunc fold to something simple.
1837 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1838 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1839 Type *DstType = Trunc->getType();
1840 Type *SrcType = Trunc->getOperand()->getType();
1841 SmallVector<const SCEV *, 8> LargeOps;
1843 // Check all the operands to see if they can be represented in the
1844 // source type of the truncate.
1845 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1846 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1847 if (T->getOperand()->getType() != SrcType) {
1851 LargeOps.push_back(T->getOperand());
1852 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1853 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1854 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1855 SmallVector<const SCEV *, 8> LargeMulOps;
1856 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1857 if (const SCEVTruncateExpr *T =
1858 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1859 if (T->getOperand()->getType() != SrcType) {
1863 LargeMulOps.push_back(T->getOperand());
1864 } else if (const SCEVConstant *C =
1865 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1866 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1873 LargeOps.push_back(getMulExpr(LargeMulOps));
1880 // Evaluate the expression in the larger type.
1881 const SCEV *Fold = getAddExpr(LargeOps, Flags);
1882 // If it folds to something simple, use it. Otherwise, don't.
1883 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1884 return getTruncateExpr(Fold, DstType);
1888 // Skip past any other cast SCEVs.
1889 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1892 // If there are add operands they would be next.
1893 if (Idx < Ops.size()) {
1894 bool DeletedAdd = false;
1895 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1896 // If we have an add, expand the add operands onto the end of the operands
1898 Ops.erase(Ops.begin()+Idx);
1899 Ops.append(Add->op_begin(), Add->op_end());
1903 // If we deleted at least one add, we added operands to the end of the list,
1904 // and they are not necessarily sorted. Recurse to resort and resimplify
1905 // any operands we just acquired.
1907 return getAddExpr(Ops);
1910 // Skip over the add expression until we get to a multiply.
1911 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1914 // Check to see if there are any folding opportunities present with
1915 // operands multiplied by constant values.
1916 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1917 uint64_t BitWidth = getTypeSizeInBits(Ty);
1918 DenseMap<const SCEV *, APInt> M;
1919 SmallVector<const SCEV *, 8> NewOps;
1920 APInt AccumulatedConstant(BitWidth, 0);
1921 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1922 Ops.data(), Ops.size(),
1923 APInt(BitWidth, 1), *this)) {
1924 // Some interesting folding opportunity is present, so its worthwhile to
1925 // re-generate the operands list. Group the operands by constant scale,
1926 // to avoid multiplying by the same constant scale multiple times.
1927 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1928 for (SmallVectorImpl<const SCEV *>::const_iterator I = NewOps.begin(),
1929 E = NewOps.end(); I != E; ++I)
1930 MulOpLists[M.find(*I)->second].push_back(*I);
1931 // Re-generate the operands list.
1933 if (AccumulatedConstant != 0)
1934 Ops.push_back(getConstant(AccumulatedConstant));
1935 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1936 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1938 Ops.push_back(getMulExpr(getConstant(I->first),
1939 getAddExpr(I->second)));
1941 return getConstant(Ty, 0);
1942 if (Ops.size() == 1)
1944 return getAddExpr(Ops);
1948 // If we are adding something to a multiply expression, make sure the
1949 // something is not already an operand of the multiply. If so, merge it into
1951 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1952 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1953 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1954 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1955 if (isa<SCEVConstant>(MulOpSCEV))
1957 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1958 if (MulOpSCEV == Ops[AddOp]) {
1959 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1960 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1961 if (Mul->getNumOperands() != 2) {
1962 // If the multiply has more than two operands, we must get the
1964 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1965 Mul->op_begin()+MulOp);
1966 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1967 InnerMul = getMulExpr(MulOps);
1969 const SCEV *One = getConstant(Ty, 1);
1970 const SCEV *AddOne = getAddExpr(One, InnerMul);
1971 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1972 if (Ops.size() == 2) return OuterMul;
1974 Ops.erase(Ops.begin()+AddOp);
1975 Ops.erase(Ops.begin()+Idx-1);
1977 Ops.erase(Ops.begin()+Idx);
1978 Ops.erase(Ops.begin()+AddOp-1);
1980 Ops.push_back(OuterMul);
1981 return getAddExpr(Ops);
1984 // Check this multiply against other multiplies being added together.
1985 for (unsigned OtherMulIdx = Idx+1;
1986 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1988 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1989 // If MulOp occurs in OtherMul, we can fold the two multiplies
1991 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1992 OMulOp != e; ++OMulOp)
1993 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1994 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1995 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1996 if (Mul->getNumOperands() != 2) {
1997 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1998 Mul->op_begin()+MulOp);
1999 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2000 InnerMul1 = getMulExpr(MulOps);
2002 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2003 if (OtherMul->getNumOperands() != 2) {
2004 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2005 OtherMul->op_begin()+OMulOp);
2006 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2007 InnerMul2 = getMulExpr(MulOps);
2009 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
2010 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2011 if (Ops.size() == 2) return OuterMul;
2012 Ops.erase(Ops.begin()+Idx);
2013 Ops.erase(Ops.begin()+OtherMulIdx-1);
2014 Ops.push_back(OuterMul);
2015 return getAddExpr(Ops);
2021 // If there are any add recurrences in the operands list, see if any other
2022 // added values are loop invariant. If so, we can fold them into the
2024 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2027 // Scan over all recurrences, trying to fold loop invariants into them.
2028 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2029 // Scan all of the other operands to this add and add them to the vector if
2030 // they are loop invariant w.r.t. the recurrence.
2031 SmallVector<const SCEV *, 8> LIOps;
2032 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2033 const Loop *AddRecLoop = AddRec->getLoop();
2034 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2035 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2036 LIOps.push_back(Ops[i]);
2037 Ops.erase(Ops.begin()+i);
2041 // If we found some loop invariants, fold them into the recurrence.
2042 if (!LIOps.empty()) {
2043 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2044 LIOps.push_back(AddRec->getStart());
2046 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2048 AddRecOps[0] = getAddExpr(LIOps);
2050 // Build the new addrec. Propagate the NUW and NSW flags if both the
2051 // outer add and the inner addrec are guaranteed to have no overflow.
2052 // Always propagate NW.
2053 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2054 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2056 // If all of the other operands were loop invariant, we are done.
2057 if (Ops.size() == 1) return NewRec;
2059 // Otherwise, add the folded AddRec by the non-invariant parts.
2060 for (unsigned i = 0;; ++i)
2061 if (Ops[i] == AddRec) {
2065 return getAddExpr(Ops);
2068 // Okay, if there weren't any loop invariants to be folded, check to see if
2069 // there are multiple AddRec's with the same loop induction variable being
2070 // added together. If so, we can fold them.
2071 for (unsigned OtherIdx = Idx+1;
2072 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2074 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2075 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2076 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2078 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2080 if (const SCEVAddRecExpr *OtherAddRec =
2081 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2082 if (OtherAddRec->getLoop() == AddRecLoop) {
2083 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2085 if (i >= AddRecOps.size()) {
2086 AddRecOps.append(OtherAddRec->op_begin()+i,
2087 OtherAddRec->op_end());
2090 AddRecOps[i] = getAddExpr(AddRecOps[i],
2091 OtherAddRec->getOperand(i));
2093 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2095 // Step size has changed, so we cannot guarantee no self-wraparound.
2096 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2097 return getAddExpr(Ops);
2100 // Otherwise couldn't fold anything into this recurrence. Move onto the
2104 // Okay, it looks like we really DO need an add expr. Check to see if we
2105 // already have one, otherwise create a new one.
2106 FoldingSetNodeID ID;
2107 ID.AddInteger(scAddExpr);
2108 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2109 ID.AddPointer(Ops[i]);
2112 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2114 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2115 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2116 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
2118 UniqueSCEVs.InsertNode(S, IP);
2120 S->setNoWrapFlags(Flags);
2124 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2126 if (j > 1 && k / j != i) Overflow = true;
2130 /// Compute the result of "n choose k", the binomial coefficient. If an
2131 /// intermediate computation overflows, Overflow will be set and the return will
2132 /// be garbage. Overflow is not cleared on absence of overflow.
2133 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2134 // We use the multiplicative formula:
2135 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2136 // At each iteration, we take the n-th term of the numeral and divide by the
2137 // (k-n)th term of the denominator. This division will always produce an
2138 // integral result, and helps reduce the chance of overflow in the
2139 // intermediate computations. However, we can still overflow even when the
2140 // final result would fit.
2142 if (n == 0 || n == k) return 1;
2143 if (k > n) return 0;
2149 for (uint64_t i = 1; i <= k; ++i) {
2150 r = umul_ov(r, n-(i-1), Overflow);
2156 /// getMulExpr - Get a canonical multiply expression, or something simpler if
2158 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2159 SCEV::NoWrapFlags Flags) {
2160 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
2161 "only nuw or nsw allowed");
2162 assert(!Ops.empty() && "Cannot get empty mul!");
2163 if (Ops.size() == 1) return Ops[0];
2165 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2166 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2167 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2168 "SCEVMulExpr operand types don't match!");
2171 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2173 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2174 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2175 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2177 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
2178 E = Ops.end(); I != E; ++I)
2179 if (!isKnownNonNegative(*I)) {
2183 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2186 // Sort by complexity, this groups all similar expression types together.
2187 GroupByComplexity(Ops, LI);
2189 // If there are any constants, fold them together.
2191 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2193 // C1*(C2+V) -> C1*C2 + C1*V
2194 if (Ops.size() == 2)
2195 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2196 if (Add->getNumOperands() == 2 &&
2197 isa<SCEVConstant>(Add->getOperand(0)))
2198 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2199 getMulExpr(LHSC, Add->getOperand(1)));
2202 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2203 // We found two constants, fold them together!
2204 ConstantInt *Fold = ConstantInt::get(getContext(),
2205 LHSC->getValue()->getValue() *
2206 RHSC->getValue()->getValue());
2207 Ops[0] = getConstant(Fold);
2208 Ops.erase(Ops.begin()+1); // Erase the folded element
2209 if (Ops.size() == 1) return Ops[0];
2210 LHSC = cast<SCEVConstant>(Ops[0]);
2213 // If we are left with a constant one being multiplied, strip it off.
2214 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2215 Ops.erase(Ops.begin());
2217 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2218 // If we have a multiply of zero, it will always be zero.
2220 } else if (Ops[0]->isAllOnesValue()) {
2221 // If we have a mul by -1 of an add, try distributing the -1 among the
2223 if (Ops.size() == 2) {
2224 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2225 SmallVector<const SCEV *, 4> NewOps;
2226 bool AnyFolded = false;
2227 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
2228 E = Add->op_end(); I != E; ++I) {
2229 const SCEV *Mul = getMulExpr(Ops[0], *I);
2230 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2231 NewOps.push_back(Mul);
2234 return getAddExpr(NewOps);
2236 else if (const SCEVAddRecExpr *
2237 AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2238 // Negation preserves a recurrence's no self-wrap property.
2239 SmallVector<const SCEV *, 4> Operands;
2240 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
2241 E = AddRec->op_end(); I != E; ++I) {
2242 Operands.push_back(getMulExpr(Ops[0], *I));
2244 return getAddRecExpr(Operands, AddRec->getLoop(),
2245 AddRec->getNoWrapFlags(SCEV::FlagNW));
2250 if (Ops.size() == 1)
2254 // Skip over the add expression until we get to a multiply.
2255 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2258 // If there are mul operands inline them all into this expression.
2259 if (Idx < Ops.size()) {
2260 bool DeletedMul = false;
2261 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2262 // If we have an mul, expand the mul operands onto the end of the operands
2264 Ops.erase(Ops.begin()+Idx);
2265 Ops.append(Mul->op_begin(), Mul->op_end());
2269 // If we deleted at least one mul, we added operands to the end of the list,
2270 // and they are not necessarily sorted. Recurse to resort and resimplify
2271 // any operands we just acquired.
2273 return getMulExpr(Ops);
2276 // If there are any add recurrences in the operands list, see if any other
2277 // added values are loop invariant. If so, we can fold them into the
2279 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2282 // Scan over all recurrences, trying to fold loop invariants into them.
2283 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2284 // Scan all of the other operands to this mul and add them to the vector if
2285 // they are loop invariant w.r.t. the recurrence.
2286 SmallVector<const SCEV *, 8> LIOps;
2287 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2288 const Loop *AddRecLoop = AddRec->getLoop();
2289 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2290 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2291 LIOps.push_back(Ops[i]);
2292 Ops.erase(Ops.begin()+i);
2296 // If we found some loop invariants, fold them into the recurrence.
2297 if (!LIOps.empty()) {
2298 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2299 SmallVector<const SCEV *, 4> NewOps;
2300 NewOps.reserve(AddRec->getNumOperands());
2301 const SCEV *Scale = getMulExpr(LIOps);
2302 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2303 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2305 // Build the new addrec. Propagate the NUW and NSW flags if both the
2306 // outer mul and the inner addrec are guaranteed to have no overflow.
2308 // No self-wrap cannot be guaranteed after changing the step size, but
2309 // will be inferred if either NUW or NSW is true.
2310 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2311 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2313 // If all of the other operands were loop invariant, we are done.
2314 if (Ops.size() == 1) return NewRec;
2316 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2317 for (unsigned i = 0;; ++i)
2318 if (Ops[i] == AddRec) {
2322 return getMulExpr(Ops);
2325 // Okay, if there weren't any loop invariants to be folded, check to see if
2326 // there are multiple AddRec's with the same loop induction variable being
2327 // multiplied together. If so, we can fold them.
2329 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2330 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2331 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2332 // ]]],+,...up to x=2n}.
2333 // Note that the arguments to choose() are always integers with values
2334 // known at compile time, never SCEV objects.
2336 // The implementation avoids pointless extra computations when the two
2337 // addrec's are of different length (mathematically, it's equivalent to
2338 // an infinite stream of zeros on the right).
2339 bool OpsModified = false;
2340 for (unsigned OtherIdx = Idx+1;
2341 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2343 const SCEVAddRecExpr *OtherAddRec =
2344 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2345 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2348 bool Overflow = false;
2349 Type *Ty = AddRec->getType();
2350 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2351 SmallVector<const SCEV*, 7> AddRecOps;
2352 for (int x = 0, xe = AddRec->getNumOperands() +
2353 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2354 const SCEV *Term = getConstant(Ty, 0);
2355 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2356 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2357 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2358 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2359 z < ze && !Overflow; ++z) {
2360 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2362 if (LargerThan64Bits)
2363 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2365 Coeff = Coeff1*Coeff2;
2366 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2367 const SCEV *Term1 = AddRec->getOperand(y-z);
2368 const SCEV *Term2 = OtherAddRec->getOperand(z);
2369 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2372 AddRecOps.push_back(Term);
2375 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2377 if (Ops.size() == 2) return NewAddRec;
2378 Ops[Idx] = NewAddRec;
2379 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2381 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2387 return getMulExpr(Ops);
2389 // Otherwise couldn't fold anything into this recurrence. Move onto the
2393 // Okay, it looks like we really DO need an mul expr. Check to see if we
2394 // already have one, otherwise create a new one.
2395 FoldingSetNodeID ID;
2396 ID.AddInteger(scMulExpr);
2397 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2398 ID.AddPointer(Ops[i]);
2401 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2403 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2404 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2405 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2407 UniqueSCEVs.InsertNode(S, IP);
2409 S->setNoWrapFlags(Flags);
2413 /// getUDivExpr - Get a canonical unsigned division expression, or something
2414 /// simpler if possible.
2415 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2417 assert(getEffectiveSCEVType(LHS->getType()) ==
2418 getEffectiveSCEVType(RHS->getType()) &&
2419 "SCEVUDivExpr operand types don't match!");
2421 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2422 if (RHSC->getValue()->equalsInt(1))
2423 return LHS; // X udiv 1 --> x
2424 // If the denominator is zero, the result of the udiv is undefined. Don't
2425 // try to analyze it, because the resolution chosen here may differ from
2426 // the resolution chosen in other parts of the compiler.
2427 if (!RHSC->getValue()->isZero()) {
2428 // Determine if the division can be folded into the operands of
2430 // TODO: Generalize this to non-constants by using known-bits information.
2431 Type *Ty = LHS->getType();
2432 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2433 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2434 // For non-power-of-two values, effectively round the value up to the
2435 // nearest power of two.
2436 if (!RHSC->getValue()->getValue().isPowerOf2())
2438 IntegerType *ExtTy =
2439 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2440 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2441 if (const SCEVConstant *Step =
2442 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2443 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2444 const APInt &StepInt = Step->getValue()->getValue();
2445 const APInt &DivInt = RHSC->getValue()->getValue();
2446 if (!StepInt.urem(DivInt) &&
2447 getZeroExtendExpr(AR, ExtTy) ==
2448 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2449 getZeroExtendExpr(Step, ExtTy),
2450 AR->getLoop(), SCEV::FlagAnyWrap)) {
2451 SmallVector<const SCEV *, 4> Operands;
2452 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
2453 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
2454 return getAddRecExpr(Operands, AR->getLoop(),
2457 /// Get a canonical UDivExpr for a recurrence.
2458 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2459 // We can currently only fold X%N if X is constant.
2460 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2461 if (StartC && !DivInt.urem(StepInt) &&
2462 getZeroExtendExpr(AR, ExtTy) ==
2463 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2464 getZeroExtendExpr(Step, ExtTy),
2465 AR->getLoop(), SCEV::FlagAnyWrap)) {
2466 const APInt &StartInt = StartC->getValue()->getValue();
2467 const APInt &StartRem = StartInt.urem(StepInt);
2469 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2470 AR->getLoop(), SCEV::FlagNW);
2473 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2474 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2475 SmallVector<const SCEV *, 4> Operands;
2476 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
2477 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
2478 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2479 // Find an operand that's safely divisible.
2480 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2481 const SCEV *Op = M->getOperand(i);
2482 const SCEV *Div = getUDivExpr(Op, RHSC);
2483 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2484 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2487 return getMulExpr(Operands);
2491 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2492 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2493 SmallVector<const SCEV *, 4> Operands;
2494 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
2495 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
2496 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2498 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2499 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2500 if (isa<SCEVUDivExpr>(Op) ||
2501 getMulExpr(Op, RHS) != A->getOperand(i))
2503 Operands.push_back(Op);
2505 if (Operands.size() == A->getNumOperands())
2506 return getAddExpr(Operands);
2510 // Fold if both operands are constant.
2511 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2512 Constant *LHSCV = LHSC->getValue();
2513 Constant *RHSCV = RHSC->getValue();
2514 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2520 FoldingSetNodeID ID;
2521 ID.AddInteger(scUDivExpr);
2525 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2526 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2528 UniqueSCEVs.InsertNode(S, IP);
2532 static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2533 APInt A = C1->getValue()->getValue().abs();
2534 APInt B = C2->getValue()->getValue().abs();
2535 uint32_t ABW = A.getBitWidth();
2536 uint32_t BBW = B.getBitWidth();
2543 return APIntOps::GreatestCommonDivisor(A, B);
2546 /// getUDivExactExpr - Get a canonical unsigned division expression, or
2547 /// something simpler if possible. There is no representation for an exact udiv
2548 /// in SCEV IR, but we can attempt to remove factors from the LHS and RHS.
2549 /// We can't do this when it's not exact because the udiv may be clearing bits.
2550 const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2552 // TODO: we could try to find factors in all sorts of things, but for now we
2553 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2554 // end of this file for inspiration.
2556 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2558 return getUDivExpr(LHS, RHS);
2560 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2561 // If the mulexpr multiplies by a constant, then that constant must be the
2562 // first element of the mulexpr.
2563 if (const SCEVConstant *LHSCst =
2564 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2565 if (LHSCst == RHSCst) {
2566 SmallVector<const SCEV *, 2> Operands;
2567 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2568 return getMulExpr(Operands);
2571 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
2572 // that there's a factor provided by one of the other terms. We need to
2574 APInt Factor = gcd(LHSCst, RHSCst);
2575 if (!Factor.isIntN(1)) {
2576 LHSCst = cast<SCEVConstant>(
2577 getConstant(LHSCst->getValue()->getValue().udiv(Factor)));
2578 RHSCst = cast<SCEVConstant>(
2579 getConstant(RHSCst->getValue()->getValue().udiv(Factor)));
2580 SmallVector<const SCEV *, 2> Operands;
2581 Operands.push_back(LHSCst);
2582 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2583 LHS = getMulExpr(Operands);
2585 Mul = dyn_cast<SCEVMulExpr>(LHS);
2587 return getUDivExactExpr(LHS, RHS);
2592 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
2593 if (Mul->getOperand(i) == RHS) {
2594 SmallVector<const SCEV *, 2> Operands;
2595 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
2596 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
2597 return getMulExpr(Operands);
2601 return getUDivExpr(LHS, RHS);
2604 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2605 /// Simplify the expression as much as possible.
2606 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2608 SCEV::NoWrapFlags Flags) {
2609 SmallVector<const SCEV *, 4> Operands;
2610 Operands.push_back(Start);
2611 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2612 if (StepChrec->getLoop() == L) {
2613 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2614 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2617 Operands.push_back(Step);
2618 return getAddRecExpr(Operands, L, Flags);
2621 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2622 /// Simplify the expression as much as possible.
2624 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2625 const Loop *L, SCEV::NoWrapFlags Flags) {
2626 if (Operands.size() == 1) return Operands[0];
2628 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2629 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2630 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2631 "SCEVAddRecExpr operand types don't match!");
2632 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2633 assert(isLoopInvariant(Operands[i], L) &&
2634 "SCEVAddRecExpr operand is not loop-invariant!");
2637 if (Operands.back()->isZero()) {
2638 Operands.pop_back();
2639 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2642 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2643 // use that information to infer NUW and NSW flags. However, computing a
2644 // BE count requires calling getAddRecExpr, so we may not yet have a
2645 // meaningful BE count at this point (and if we don't, we'd be stuck
2646 // with a SCEVCouldNotCompute as the cached BE count).
2648 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2650 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2651 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2652 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2654 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2655 E = Operands.end(); I != E; ++I)
2656 if (!isKnownNonNegative(*I)) {
2660 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2663 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2664 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2665 const Loop *NestedLoop = NestedAR->getLoop();
2666 if (L->contains(NestedLoop) ?
2667 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2668 (!NestedLoop->contains(L) &&
2669 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2670 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2671 NestedAR->op_end());
2672 Operands[0] = NestedAR->getStart();
2673 // AddRecs require their operands be loop-invariant with respect to their
2674 // loops. Don't perform this transformation if it would break this
2676 bool AllInvariant = true;
2677 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2678 if (!isLoopInvariant(Operands[i], L)) {
2679 AllInvariant = false;
2683 // Create a recurrence for the outer loop with the same step size.
2685 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2686 // inner recurrence has the same property.
2687 SCEV::NoWrapFlags OuterFlags =
2688 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2690 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2691 AllInvariant = true;
2692 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2693 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2694 AllInvariant = false;
2698 // Ok, both add recurrences are valid after the transformation.
2700 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2701 // the outer recurrence has the same property.
2702 SCEV::NoWrapFlags InnerFlags =
2703 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2704 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2707 // Reset Operands to its original state.
2708 Operands[0] = NestedAR;
2712 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2713 // already have one, otherwise create a new one.
2714 FoldingSetNodeID ID;
2715 ID.AddInteger(scAddRecExpr);
2716 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2717 ID.AddPointer(Operands[i]);
2721 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2723 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2724 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2725 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2726 O, Operands.size(), L);
2727 UniqueSCEVs.InsertNode(S, IP);
2729 S->setNoWrapFlags(Flags);
2733 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2735 SmallVector<const SCEV *, 2> Ops;
2738 return getSMaxExpr(Ops);
2742 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2743 assert(!Ops.empty() && "Cannot get empty smax!");
2744 if (Ops.size() == 1) return Ops[0];
2746 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2747 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2748 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2749 "SCEVSMaxExpr operand types don't match!");
2752 // Sort by complexity, this groups all similar expression types together.
2753 GroupByComplexity(Ops, LI);
2755 // If there are any constants, fold them together.
2757 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2759 assert(Idx < Ops.size());
2760 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2761 // We found two constants, fold them together!
2762 ConstantInt *Fold = ConstantInt::get(getContext(),
2763 APIntOps::smax(LHSC->getValue()->getValue(),
2764 RHSC->getValue()->getValue()));
2765 Ops[0] = getConstant(Fold);
2766 Ops.erase(Ops.begin()+1); // Erase the folded element
2767 if (Ops.size() == 1) return Ops[0];
2768 LHSC = cast<SCEVConstant>(Ops[0]);
2771 // If we are left with a constant minimum-int, strip it off.
2772 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2773 Ops.erase(Ops.begin());
2775 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2776 // If we have an smax with a constant maximum-int, it will always be
2781 if (Ops.size() == 1) return Ops[0];
2784 // Find the first SMax
2785 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2788 // Check to see if one of the operands is an SMax. If so, expand its operands
2789 // onto our operand list, and recurse to simplify.
2790 if (Idx < Ops.size()) {
2791 bool DeletedSMax = false;
2792 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2793 Ops.erase(Ops.begin()+Idx);
2794 Ops.append(SMax->op_begin(), SMax->op_end());
2799 return getSMaxExpr(Ops);
2802 // Okay, check to see if the same value occurs in the operand list twice. If
2803 // so, delete one. Since we sorted the list, these values are required to
2805 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2806 // X smax Y smax Y --> X smax Y
2807 // X smax Y --> X, if X is always greater than Y
2808 if (Ops[i] == Ops[i+1] ||
2809 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2810 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2812 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2813 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2817 if (Ops.size() == 1) return Ops[0];
2819 assert(!Ops.empty() && "Reduced smax down to nothing!");
2821 // Okay, it looks like we really DO need an smax expr. Check to see if we
2822 // already have one, otherwise create a new one.
2823 FoldingSetNodeID ID;
2824 ID.AddInteger(scSMaxExpr);
2825 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2826 ID.AddPointer(Ops[i]);
2828 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2829 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2830 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2831 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2833 UniqueSCEVs.InsertNode(S, IP);
2837 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2839 SmallVector<const SCEV *, 2> Ops;
2842 return getUMaxExpr(Ops);
2846 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2847 assert(!Ops.empty() && "Cannot get empty umax!");
2848 if (Ops.size() == 1) return Ops[0];
2850 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2851 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2852 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2853 "SCEVUMaxExpr operand types don't match!");
2856 // Sort by complexity, this groups all similar expression types together.
2857 GroupByComplexity(Ops, LI);
2859 // If there are any constants, fold them together.
2861 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2863 assert(Idx < Ops.size());
2864 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2865 // We found two constants, fold them together!
2866 ConstantInt *Fold = ConstantInt::get(getContext(),
2867 APIntOps::umax(LHSC->getValue()->getValue(),
2868 RHSC->getValue()->getValue()));
2869 Ops[0] = getConstant(Fold);
2870 Ops.erase(Ops.begin()+1); // Erase the folded element
2871 if (Ops.size() == 1) return Ops[0];
2872 LHSC = cast<SCEVConstant>(Ops[0]);
2875 // If we are left with a constant minimum-int, strip it off.
2876 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2877 Ops.erase(Ops.begin());
2879 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2880 // If we have an umax with a constant maximum-int, it will always be
2885 if (Ops.size() == 1) return Ops[0];
2888 // Find the first UMax
2889 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2892 // Check to see if one of the operands is a UMax. If so, expand its operands
2893 // onto our operand list, and recurse to simplify.
2894 if (Idx < Ops.size()) {
2895 bool DeletedUMax = false;
2896 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2897 Ops.erase(Ops.begin()+Idx);
2898 Ops.append(UMax->op_begin(), UMax->op_end());
2903 return getUMaxExpr(Ops);
2906 // Okay, check to see if the same value occurs in the operand list twice. If
2907 // so, delete one. Since we sorted the list, these values are required to
2909 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2910 // X umax Y umax Y --> X umax Y
2911 // X umax Y --> X, if X is always greater than Y
2912 if (Ops[i] == Ops[i+1] ||
2913 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2914 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2916 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2917 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2921 if (Ops.size() == 1) return Ops[0];
2923 assert(!Ops.empty() && "Reduced umax down to nothing!");
2925 // Okay, it looks like we really DO need a umax expr. Check to see if we
2926 // already have one, otherwise create a new one.
2927 FoldingSetNodeID ID;
2928 ID.AddInteger(scUMaxExpr);
2929 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2930 ID.AddPointer(Ops[i]);
2932 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2933 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2934 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2935 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2937 UniqueSCEVs.InsertNode(S, IP);
2941 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2943 // ~smax(~x, ~y) == smin(x, y).
2944 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2947 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2949 // ~umax(~x, ~y) == umin(x, y)
2950 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2953 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
2954 // If we have DataLayout, we can bypass creating a target-independent
2955 // constant expression and then folding it back into a ConstantInt.
2956 // This is just a compile-time optimization.
2958 return getConstant(IntTy, DL->getTypeAllocSize(AllocTy));
2960 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2961 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2962 if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
2964 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2965 assert(Ty == IntTy && "Effective SCEV type doesn't match");
2966 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2969 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
2972 // If we have DataLayout, we can bypass creating a target-independent
2973 // constant expression and then folding it back into a ConstantInt.
2974 // This is just a compile-time optimization.
2976 return getConstant(IntTy,
2977 DL->getStructLayout(STy)->getElementOffset(FieldNo));
2980 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2981 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2982 if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
2985 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2986 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2989 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2990 // Don't attempt to do anything other than create a SCEVUnknown object
2991 // here. createSCEV only calls getUnknown after checking for all other
2992 // interesting possibilities, and any other code that calls getUnknown
2993 // is doing so in order to hide a value from SCEV canonicalization.
2995 FoldingSetNodeID ID;
2996 ID.AddInteger(scUnknown);
2999 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3000 assert(cast<SCEVUnknown>(S)->getValue() == V &&
3001 "Stale SCEVUnknown in uniquing map!");
3004 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3006 FirstUnknown = cast<SCEVUnknown>(S);
3007 UniqueSCEVs.InsertNode(S, IP);
3011 //===----------------------------------------------------------------------===//
3012 // Basic SCEV Analysis and PHI Idiom Recognition Code
3015 /// isSCEVable - Test if values of the given type are analyzable within
3016 /// the SCEV framework. This primarily includes integer types, and it
3017 /// can optionally include pointer types if the ScalarEvolution class
3018 /// has access to target-specific information.
3019 bool ScalarEvolution::isSCEVable(Type *Ty) const {
3020 // Integers and pointers are always SCEVable.
3021 return Ty->isIntegerTy() || Ty->isPointerTy();
3024 /// getTypeSizeInBits - Return the size in bits of the specified type,
3025 /// for which isSCEVable must return true.
3026 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3027 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3029 // If we have a DataLayout, use it!
3031 return DL->getTypeSizeInBits(Ty);
3033 // Integer types have fixed sizes.
3034 if (Ty->isIntegerTy())
3035 return Ty->getPrimitiveSizeInBits();
3037 // The only other support type is pointer. Without DataLayout, conservatively
3038 // assume pointers are 64-bit.
3039 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
3043 /// getEffectiveSCEVType - Return a type with the same bitwidth as
3044 /// the given type and which represents how SCEV will treat the given
3045 /// type, for which isSCEVable must return true. For pointer types,
3046 /// this is the pointer-sized integer type.
3047 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3048 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3050 if (Ty->isIntegerTy()) {
3054 // The only other support type is pointer.
3055 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
3058 return DL->getIntPtrType(Ty);
3060 // Without DataLayout, conservatively assume pointers are 64-bit.
3061 return Type::getInt64Ty(getContext());
3064 const SCEV *ScalarEvolution::getCouldNotCompute() {
3065 return &CouldNotCompute;
3069 // Helper class working with SCEVTraversal to figure out if a SCEV contains
3070 // a SCEVUnknown with null value-pointer. FindInvalidSCEVUnknown::FindOne
3071 // is set iff if find such SCEVUnknown.
3073 struct FindInvalidSCEVUnknown {
3075 FindInvalidSCEVUnknown() { FindOne = false; }
3076 bool follow(const SCEV *S) {
3077 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
3081 if (!cast<SCEVUnknown>(S)->getValue())
3088 bool isDone() const { return FindOne; }
3092 bool ScalarEvolution::checkValidity(const SCEV *S) const {
3093 FindInvalidSCEVUnknown F;
3094 SCEVTraversal<FindInvalidSCEVUnknown> ST(F);
3100 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
3101 /// expression and create a new one.
3102 const SCEV *ScalarEvolution::getSCEV(Value *V) {
3103 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3105 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3106 if (I != ValueExprMap.end()) {
3107 const SCEV *S = I->second;
3108 if (checkValidity(S))
3111 ValueExprMap.erase(I);
3113 const SCEV *S = createSCEV(V);
3115 // The process of creating a SCEV for V may have caused other SCEVs
3116 // to have been created, so it's necessary to insert the new entry
3117 // from scratch, rather than trying to remember the insert position
3119 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
3123 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
3125 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
3126 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3128 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3130 Type *Ty = V->getType();
3131 Ty = getEffectiveSCEVType(Ty);
3132 return getMulExpr(V,
3133 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
3136 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
3137 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3138 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3140 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3142 Type *Ty = V->getType();
3143 Ty = getEffectiveSCEVType(Ty);
3144 const SCEV *AllOnes =
3145 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3146 return getMinusSCEV(AllOnes, V);
3149 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
3150 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3151 SCEV::NoWrapFlags Flags) {
3152 assert(!maskFlags(Flags, SCEV::FlagNUW) && "subtraction does not have NUW");
3154 // Fast path: X - X --> 0.
3156 return getConstant(LHS->getType(), 0);
3159 return getAddExpr(LHS, getNegativeSCEV(RHS), Flags);
3162 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
3163 /// input value to the specified type. If the type must be extended, it is zero
3166 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3167 Type *SrcTy = V->getType();
3168 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3169 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3170 "Cannot truncate or zero extend with non-integer arguments!");
3171 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3172 return V; // No conversion
3173 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3174 return getTruncateExpr(V, Ty);
3175 return getZeroExtendExpr(V, Ty);
3178 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
3179 /// input value to the specified type. If the type must be extended, it is sign
3182 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3184 Type *SrcTy = V->getType();
3185 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3186 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3187 "Cannot truncate or zero extend with non-integer arguments!");
3188 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3189 return V; // No conversion
3190 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3191 return getTruncateExpr(V, Ty);
3192 return getSignExtendExpr(V, Ty);
3195 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
3196 /// input value to the specified type. If the type must be extended, it is zero
3197 /// extended. The conversion must not be narrowing.
3199 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3200 Type *SrcTy = V->getType();
3201 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3202 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3203 "Cannot noop or zero extend with non-integer arguments!");
3204 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3205 "getNoopOrZeroExtend cannot truncate!");
3206 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3207 return V; // No conversion
3208 return getZeroExtendExpr(V, Ty);
3211 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
3212 /// input value to the specified type. If the type must be extended, it is sign
3213 /// extended. The conversion must not be narrowing.
3215 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3216 Type *SrcTy = V->getType();
3217 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3218 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3219 "Cannot noop or sign extend with non-integer arguments!");
3220 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3221 "getNoopOrSignExtend cannot truncate!");
3222 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3223 return V; // No conversion
3224 return getSignExtendExpr(V, Ty);
3227 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
3228 /// the input value to the specified type. If the type must be extended,
3229 /// it is extended with unspecified bits. The conversion must not be
3232 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3233 Type *SrcTy = V->getType();
3234 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3235 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3236 "Cannot noop or any extend with non-integer arguments!");
3237 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3238 "getNoopOrAnyExtend cannot truncate!");
3239 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3240 return V; // No conversion
3241 return getAnyExtendExpr(V, Ty);
3244 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
3245 /// input value to the specified type. The conversion must not be widening.
3247 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3248 Type *SrcTy = V->getType();
3249 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3250 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3251 "Cannot truncate or noop with non-integer arguments!");
3252 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
3253 "getTruncateOrNoop cannot extend!");
3254 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3255 return V; // No conversion
3256 return getTruncateExpr(V, Ty);
3259 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
3260 /// the types using zero-extension, and then perform a umax operation
3262 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3264 const SCEV *PromotedLHS = LHS;
3265 const SCEV *PromotedRHS = RHS;
3267 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3268 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3270 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3272 return getUMaxExpr(PromotedLHS, PromotedRHS);
3275 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
3276 /// the types using zero-extension, and then perform a umin operation
3278 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3280 const SCEV *PromotedLHS = LHS;
3281 const SCEV *PromotedRHS = RHS;
3283 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3284 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3286 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3288 return getUMinExpr(PromotedLHS, PromotedRHS);
3291 /// getPointerBase - Transitively follow the chain of pointer-type operands
3292 /// until reaching a SCEV that does not have a single pointer operand. This
3293 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
3294 /// but corner cases do exist.
3295 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3296 // A pointer operand may evaluate to a nonpointer expression, such as null.
3297 if (!V->getType()->isPointerTy())
3300 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3301 return getPointerBase(Cast->getOperand());
3303 else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3304 const SCEV *PtrOp = nullptr;
3305 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
3307 if ((*I)->getType()->isPointerTy()) {
3308 // Cannot find the base of an expression with multiple pointer operands.
3316 return getPointerBase(PtrOp);
3321 /// PushDefUseChildren - Push users of the given Instruction
3322 /// onto the given Worklist.
3324 PushDefUseChildren(Instruction *I,
3325 SmallVectorImpl<Instruction *> &Worklist) {
3326 // Push the def-use children onto the Worklist stack.
3327 for (User *U : I->users())
3328 Worklist.push_back(cast<Instruction>(U));
3331 /// ForgetSymbolicValue - This looks up computed SCEV values for all
3332 /// instructions that depend on the given instruction and removes them from
3333 /// the ValueExprMapType map if they reference SymName. This is used during PHI
3336 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3337 SmallVector<Instruction *, 16> Worklist;
3338 PushDefUseChildren(PN, Worklist);
3340 SmallPtrSet<Instruction *, 8> Visited;
3342 while (!Worklist.empty()) {
3343 Instruction *I = Worklist.pop_back_val();
3344 if (!Visited.insert(I)) continue;
3346 ValueExprMapType::iterator It =
3347 ValueExprMap.find_as(static_cast<Value *>(I));
3348 if (It != ValueExprMap.end()) {
3349 const SCEV *Old = It->second;
3351 // Short-circuit the def-use traversal if the symbolic name
3352 // ceases to appear in expressions.
3353 if (Old != SymName && !hasOperand(Old, SymName))
3356 // SCEVUnknown for a PHI either means that it has an unrecognized
3357 // structure, it's a PHI that's in the progress of being computed
3358 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3359 // additional loop trip count information isn't going to change anything.
3360 // In the second case, createNodeForPHI will perform the necessary
3361 // updates on its own when it gets to that point. In the third, we do
3362 // want to forget the SCEVUnknown.
3363 if (!isa<PHINode>(I) ||
3364 !isa<SCEVUnknown>(Old) ||
3365 (I != PN && Old == SymName)) {
3366 forgetMemoizedResults(Old);
3367 ValueExprMap.erase(It);
3371 PushDefUseChildren(I, Worklist);
3375 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
3376 /// a loop header, making it a potential recurrence, or it doesn't.
3378 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
3379 if (const Loop *L = LI->getLoopFor(PN->getParent()))
3380 if (L->getHeader() == PN->getParent()) {
3381 // The loop may have multiple entrances or multiple exits; we can analyze
3382 // this phi as an addrec if it has a unique entry value and a unique
3384 Value *BEValueV = nullptr, *StartValueV = nullptr;
3385 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
3386 Value *V = PN->getIncomingValue(i);
3387 if (L->contains(PN->getIncomingBlock(i))) {
3390 } else if (BEValueV != V) {
3394 } else if (!StartValueV) {
3396 } else if (StartValueV != V) {
3397 StartValueV = nullptr;
3401 if (BEValueV && StartValueV) {
3402 // While we are analyzing this PHI node, handle its value symbolically.
3403 const SCEV *SymbolicName = getUnknown(PN);
3404 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&
3405 "PHI node already processed?");
3406 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
3408 // Using this symbolic name for the PHI, analyze the value coming around
3410 const SCEV *BEValue = getSCEV(BEValueV);
3412 // NOTE: If BEValue is loop invariant, we know that the PHI node just
3413 // has a special value for the first iteration of the loop.
3415 // If the value coming around the backedge is an add with the symbolic
3416 // value we just inserted, then we found a simple induction variable!
3417 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
3418 // If there is a single occurrence of the symbolic value, replace it
3419 // with a recurrence.
3420 unsigned FoundIndex = Add->getNumOperands();
3421 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3422 if (Add->getOperand(i) == SymbolicName)
3423 if (FoundIndex == e) {
3428 if (FoundIndex != Add->getNumOperands()) {
3429 // Create an add with everything but the specified operand.
3430 SmallVector<const SCEV *, 8> Ops;
3431 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3432 if (i != FoundIndex)
3433 Ops.push_back(Add->getOperand(i));
3434 const SCEV *Accum = getAddExpr(Ops);
3436 // This is not a valid addrec if the step amount is varying each
3437 // loop iteration, but is not itself an addrec in this loop.
3438 if (isLoopInvariant(Accum, L) ||
3439 (isa<SCEVAddRecExpr>(Accum) &&
3440 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
3441 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3443 // If the increment doesn't overflow, then neither the addrec nor
3444 // the post-increment will overflow.
3445 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
3446 if (OBO->hasNoUnsignedWrap())
3447 Flags = setFlags(Flags, SCEV::FlagNUW);
3448 if (OBO->hasNoSignedWrap())
3449 Flags = setFlags(Flags, SCEV::FlagNSW);
3450 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
3451 // If the increment is an inbounds GEP, then we know the address
3452 // space cannot be wrapped around. We cannot make any guarantee
3453 // about signed or unsigned overflow because pointers are
3454 // unsigned but we may have a negative index from the base
3455 // pointer. We can guarantee that no unsigned wrap occurs if the
3456 // indices form a positive value.
3457 if (GEP->isInBounds()) {
3458 Flags = setFlags(Flags, SCEV::FlagNW);
3460 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
3461 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
3462 Flags = setFlags(Flags, SCEV::FlagNUW);
3464 } else if (const SubOperator *OBO =
3465 dyn_cast<SubOperator>(BEValueV)) {
3466 if (OBO->hasNoUnsignedWrap())
3467 Flags = setFlags(Flags, SCEV::FlagNUW);
3468 if (OBO->hasNoSignedWrap())
3469 Flags = setFlags(Flags, SCEV::FlagNSW);
3472 const SCEV *StartVal = getSCEV(StartValueV);
3473 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
3475 // Since the no-wrap flags are on the increment, they apply to the
3476 // post-incremented value as well.
3477 if (isLoopInvariant(Accum, L))
3478 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
3481 // Okay, for the entire analysis of this edge we assumed the PHI
3482 // to be symbolic. We now need to go back and purge all of the
3483 // entries for the scalars that use the symbolic expression.
3484 ForgetSymbolicName(PN, SymbolicName);
3485 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3489 } else if (const SCEVAddRecExpr *AddRec =
3490 dyn_cast<SCEVAddRecExpr>(BEValue)) {
3491 // Otherwise, this could be a loop like this:
3492 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
3493 // In this case, j = {1,+,1} and BEValue is j.
3494 // Because the other in-value of i (0) fits the evolution of BEValue
3495 // i really is an addrec evolution.
3496 if (AddRec->getLoop() == L && AddRec->isAffine()) {
3497 const SCEV *StartVal = getSCEV(StartValueV);
3499 // If StartVal = j.start - j.stride, we can use StartVal as the
3500 // initial step of the addrec evolution.
3501 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
3502 AddRec->getOperand(1))) {
3503 // FIXME: For constant StartVal, we should be able to infer
3505 const SCEV *PHISCEV =
3506 getAddRecExpr(StartVal, AddRec->getOperand(1), L,
3509 // Okay, for the entire analysis of this edge we assumed the PHI
3510 // to be symbolic. We now need to go back and purge all of the
3511 // entries for the scalars that use the symbolic expression.
3512 ForgetSymbolicName(PN, SymbolicName);
3513 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3521 // If the PHI has a single incoming value, follow that value, unless the
3522 // PHI's incoming blocks are in a different loop, in which case doing so
3523 // risks breaking LCSSA form. Instcombine would normally zap these, but
3524 // it doesn't have DominatorTree information, so it may miss cases.
3525 if (Value *V = SimplifyInstruction(PN, DL, TLI, DT, AT))
3526 if (LI->replacementPreservesLCSSAForm(PN, V))
3529 // If it's not a loop phi, we can't handle it yet.
3530 return getUnknown(PN);
3533 /// createNodeForGEP - Expand GEP instructions into add and multiply
3534 /// operations. This allows them to be analyzed by regular SCEV code.
3536 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
3537 Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
3538 Value *Base = GEP->getOperand(0);
3539 // Don't attempt to analyze GEPs over unsized objects.
3540 if (!Base->getType()->getPointerElementType()->isSized())
3541 return getUnknown(GEP);
3543 // Don't blindly transfer the inbounds flag from the GEP instruction to the
3544 // Add expression, because the Instruction may be guarded by control flow
3545 // and the no-overflow bits may not be valid for the expression in any
3547 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3549 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
3550 gep_type_iterator GTI = gep_type_begin(GEP);
3551 for (GetElementPtrInst::op_iterator I = std::next(GEP->op_begin()),
3555 // Compute the (potentially symbolic) offset in bytes for this index.
3556 if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
3557 // For a struct, add the member offset.
3558 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
3559 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
3561 // Add the field offset to the running total offset.
3562 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3564 // For an array, add the element offset, explicitly scaled.
3565 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, *GTI);
3566 const SCEV *IndexS = getSCEV(Index);
3567 // Getelementptr indices are signed.
3568 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
3570 // Multiply the index by the element size to compute the element offset.
3571 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize, Wrap);
3573 // Add the element offset to the running total offset.
3574 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3578 // Get the SCEV for the GEP base.
3579 const SCEV *BaseS = getSCEV(Base);
3581 // Add the total offset from all the GEP indices to the base.
3582 return getAddExpr(BaseS, TotalOffset, Wrap);
3585 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
3586 /// guaranteed to end in (at every loop iteration). It is, at the same time,
3587 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
3588 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
3590 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
3591 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3592 return C->getValue()->getValue().countTrailingZeros();
3594 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
3595 return std::min(GetMinTrailingZeros(T->getOperand()),
3596 (uint32_t)getTypeSizeInBits(T->getType()));
3598 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
3599 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3600 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3601 getTypeSizeInBits(E->getType()) : OpRes;
3604 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
3605 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3606 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3607 getTypeSizeInBits(E->getType()) : OpRes;
3610 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
3611 // The result is the min of all operands results.
3612 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3613 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3614 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3618 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
3619 // The result is the sum of all operands results.
3620 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
3621 uint32_t BitWidth = getTypeSizeInBits(M->getType());
3622 for (unsigned i = 1, e = M->getNumOperands();
3623 SumOpRes != BitWidth && i != e; ++i)
3624 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
3629 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
3630 // The result is the min of all operands results.
3631 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3632 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3633 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3637 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
3638 // The result is the min of all operands results.
3639 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3640 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3641 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3645 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
3646 // The result is the min of all operands results.
3647 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3648 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3649 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3653 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3654 // For a SCEVUnknown, ask ValueTracking.
3655 unsigned BitWidth = getTypeSizeInBits(U->getType());
3656 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3657 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
3658 return Zeros.countTrailingOnes();
3665 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
3668 ScalarEvolution::getUnsignedRange(const SCEV *S) {
3669 // See if we've computed this range already.
3670 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
3671 if (I != UnsignedRanges.end())
3674 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3675 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
3677 unsigned BitWidth = getTypeSizeInBits(S->getType());
3678 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3680 // If the value has known zeros, the maximum unsigned value will have those
3681 // known zeros as well.
3682 uint32_t TZ = GetMinTrailingZeros(S);
3684 ConservativeResult =
3685 ConstantRange(APInt::getMinValue(BitWidth),
3686 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3688 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3689 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3690 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3691 X = X.add(getUnsignedRange(Add->getOperand(i)));
3692 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3695 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3696 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3697 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3698 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3699 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3702 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3703 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3704 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3705 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3706 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3709 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3710 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3711 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3712 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3713 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3716 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3717 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3718 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3719 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3722 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3723 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3724 return setUnsignedRange(ZExt,
3725 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3728 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3729 ConstantRange X = getUnsignedRange(SExt->getOperand());
3730 return setUnsignedRange(SExt,
3731 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3734 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3735 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3736 return setUnsignedRange(Trunc,
3737 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3740 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3741 // If there's no unsigned wrap, the value will never be less than its
3743 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
3744 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3745 if (!C->getValue()->isZero())
3746 ConservativeResult =
3747 ConservativeResult.intersectWith(
3748 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3750 // TODO: non-affine addrec
3751 if (AddRec->isAffine()) {
3752 Type *Ty = AddRec->getType();
3753 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3754 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3755 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3756 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3758 const SCEV *Start = AddRec->getStart();
3759 const SCEV *Step = AddRec->getStepRecurrence(*this);
3761 ConstantRange StartRange = getUnsignedRange(Start);
3762 ConstantRange StepRange = getSignedRange(Step);
3763 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3764 ConstantRange EndRange =
3765 StartRange.add(MaxBECountRange.multiply(StepRange));
3767 // Check for overflow. This must be done with ConstantRange arithmetic
3768 // because we could be called from within the ScalarEvolution overflow
3770 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3771 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3772 ConstantRange ExtMaxBECountRange =
3773 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3774 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3775 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3777 return setUnsignedRange(AddRec, ConservativeResult);
3779 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3780 EndRange.getUnsignedMin());
3781 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3782 EndRange.getUnsignedMax());
3783 if (Min.isMinValue() && Max.isMaxValue())
3784 return setUnsignedRange(AddRec, ConservativeResult);
3785 return setUnsignedRange(AddRec,
3786 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3790 return setUnsignedRange(AddRec, ConservativeResult);
3793 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3794 // For a SCEVUnknown, ask ValueTracking.
3795 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3796 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
3797 if (Ones == ~Zeros + 1)
3798 return setUnsignedRange(U, ConservativeResult);
3799 return setUnsignedRange(U,
3800 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3803 return setUnsignedRange(S, ConservativeResult);
3806 /// getSignedRange - Determine the signed range for a particular SCEV.
3809 ScalarEvolution::getSignedRange(const SCEV *S) {
3810 // See if we've computed this range already.
3811 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3812 if (I != SignedRanges.end())
3815 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3816 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3818 unsigned BitWidth = getTypeSizeInBits(S->getType());
3819 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3821 // If the value has known zeros, the maximum signed value will have those
3822 // known zeros as well.
3823 uint32_t TZ = GetMinTrailingZeros(S);
3825 ConservativeResult =
3826 ConstantRange(APInt::getSignedMinValue(BitWidth),
3827 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3829 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3830 ConstantRange X = getSignedRange(Add->getOperand(0));
3831 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3832 X = X.add(getSignedRange(Add->getOperand(i)));
3833 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3836 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3837 ConstantRange X = getSignedRange(Mul->getOperand(0));
3838 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3839 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3840 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3843 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3844 ConstantRange X = getSignedRange(SMax->getOperand(0));
3845 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3846 X = X.smax(getSignedRange(SMax->getOperand(i)));
3847 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3850 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3851 ConstantRange X = getSignedRange(UMax->getOperand(0));
3852 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3853 X = X.umax(getSignedRange(UMax->getOperand(i)));
3854 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3857 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3858 ConstantRange X = getSignedRange(UDiv->getLHS());
3859 ConstantRange Y = getSignedRange(UDiv->getRHS());
3860 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3863 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3864 ConstantRange X = getSignedRange(ZExt->getOperand());
3865 return setSignedRange(ZExt,
3866 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3869 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3870 ConstantRange X = getSignedRange(SExt->getOperand());
3871 return setSignedRange(SExt,
3872 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3875 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3876 ConstantRange X = getSignedRange(Trunc->getOperand());
3877 return setSignedRange(Trunc,
3878 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3881 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3882 // If there's no signed wrap, and all the operands have the same sign or
3883 // zero, the value won't ever change sign.
3884 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
3885 bool AllNonNeg = true;
3886 bool AllNonPos = true;
3887 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3888 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3889 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3892 ConservativeResult = ConservativeResult.intersectWith(
3893 ConstantRange(APInt(BitWidth, 0),
3894 APInt::getSignedMinValue(BitWidth)));
3896 ConservativeResult = ConservativeResult.intersectWith(
3897 ConstantRange(APInt::getSignedMinValue(BitWidth),
3898 APInt(BitWidth, 1)));
3901 // TODO: non-affine addrec
3902 if (AddRec->isAffine()) {
3903 Type *Ty = AddRec->getType();
3904 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3905 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3906 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3907 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3909 const SCEV *Start = AddRec->getStart();
3910 const SCEV *Step = AddRec->getStepRecurrence(*this);
3912 ConstantRange StartRange = getSignedRange(Start);
3913 ConstantRange StepRange = getSignedRange(Step);
3914 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3915 ConstantRange EndRange =
3916 StartRange.add(MaxBECountRange.multiply(StepRange));
3918 // Check for overflow. This must be done with ConstantRange arithmetic
3919 // because we could be called from within the ScalarEvolution overflow
3921 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3922 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3923 ConstantRange ExtMaxBECountRange =
3924 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3925 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3926 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3928 return setSignedRange(AddRec, ConservativeResult);
3930 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3931 EndRange.getSignedMin());
3932 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3933 EndRange.getSignedMax());
3934 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3935 return setSignedRange(AddRec, ConservativeResult);
3936 return setSignedRange(AddRec,
3937 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3941 return setSignedRange(AddRec, ConservativeResult);
3944 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3945 // For a SCEVUnknown, ask ValueTracking.
3946 if (!U->getValue()->getType()->isIntegerTy() && !DL)
3947 return setSignedRange(U, ConservativeResult);
3948 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, AT, nullptr, DT);
3950 return setSignedRange(U, ConservativeResult);
3951 return setSignedRange(U, ConservativeResult.intersectWith(
3952 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3953 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
3956 return setSignedRange(S, ConservativeResult);
3959 /// createSCEV - We know that there is no SCEV for the specified value.
3960 /// Analyze the expression.
3962 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3963 if (!isSCEVable(V->getType()))
3964 return getUnknown(V);
3966 unsigned Opcode = Instruction::UserOp1;
3967 if (Instruction *I = dyn_cast<Instruction>(V)) {
3968 Opcode = I->getOpcode();
3970 // Don't attempt to analyze instructions in blocks that aren't
3971 // reachable. Such instructions don't matter, and they aren't required
3972 // to obey basic rules for definitions dominating uses which this
3973 // analysis depends on.
3974 if (!DT->isReachableFromEntry(I->getParent()))
3975 return getUnknown(V);
3976 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3977 Opcode = CE->getOpcode();
3978 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3979 return getConstant(CI);
3980 else if (isa<ConstantPointerNull>(V))
3981 return getConstant(V->getType(), 0);
3982 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3983 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3985 return getUnknown(V);
3987 Operator *U = cast<Operator>(V);
3989 case Instruction::Add: {
3990 // The simple thing to do would be to just call getSCEV on both operands
3991 // and call getAddExpr with the result. However if we're looking at a
3992 // bunch of things all added together, this can be quite inefficient,
3993 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3994 // Instead, gather up all the operands and make a single getAddExpr call.
3995 // LLVM IR canonical form means we need only traverse the left operands.
3997 // Don't apply this instruction's NSW or NUW flags to the new
3998 // expression. The instruction may be guarded by control flow that the
3999 // no-wrap behavior depends on. Non-control-equivalent instructions can be
4000 // mapped to the same SCEV expression, and it would be incorrect to transfer
4001 // NSW/NUW semantics to those operations.
4002 SmallVector<const SCEV *, 4> AddOps;
4003 AddOps.push_back(getSCEV(U->getOperand(1)));
4004 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
4005 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
4006 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
4008 U = cast<Operator>(Op);
4009 const SCEV *Op1 = getSCEV(U->getOperand(1));
4010 if (Opcode == Instruction::Sub)
4011 AddOps.push_back(getNegativeSCEV(Op1));
4013 AddOps.push_back(Op1);
4015 AddOps.push_back(getSCEV(U->getOperand(0)));
4016 return getAddExpr(AddOps);
4018 case Instruction::Mul: {
4019 // Don't transfer NSW/NUW for the same reason as AddExpr.
4020 SmallVector<const SCEV *, 4> MulOps;
4021 MulOps.push_back(getSCEV(U->getOperand(1)));
4022 for (Value *Op = U->getOperand(0);
4023 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
4024 Op = U->getOperand(0)) {
4025 U = cast<Operator>(Op);
4026 MulOps.push_back(getSCEV(U->getOperand(1)));
4028 MulOps.push_back(getSCEV(U->getOperand(0)));
4029 return getMulExpr(MulOps);
4031 case Instruction::UDiv:
4032 return getUDivExpr(getSCEV(U->getOperand(0)),
4033 getSCEV(U->getOperand(1)));
4034 case Instruction::Sub:
4035 return getMinusSCEV(getSCEV(U->getOperand(0)),
4036 getSCEV(U->getOperand(1)));
4037 case Instruction::And:
4038 // For an expression like x&255 that merely masks off the high bits,
4039 // use zext(trunc(x)) as the SCEV expression.
4040 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4041 if (CI->isNullValue())
4042 return getSCEV(U->getOperand(1));
4043 if (CI->isAllOnesValue())
4044 return getSCEV(U->getOperand(0));
4045 const APInt &A = CI->getValue();
4047 // Instcombine's ShrinkDemandedConstant may strip bits out of
4048 // constants, obscuring what would otherwise be a low-bits mask.
4049 // Use computeKnownBits to compute what ShrinkDemandedConstant
4050 // knew about to reconstruct a low-bits mask value.
4051 unsigned LZ = A.countLeadingZeros();
4052 unsigned TZ = A.countTrailingZeros();
4053 unsigned BitWidth = A.getBitWidth();
4054 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4055 computeKnownBits(U->getOperand(0), KnownZero, KnownOne, DL,
4056 0, AT, nullptr, DT);
4058 APInt EffectiveMask =
4059 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
4060 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
4061 const SCEV *MulCount = getConstant(
4062 ConstantInt::get(getContext(), APInt::getOneBitSet(BitWidth, TZ)));
4066 getUDivExactExpr(getSCEV(U->getOperand(0)), MulCount),
4067 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
4074 case Instruction::Or:
4075 // If the RHS of the Or is a constant, we may have something like:
4076 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
4077 // optimizations will transparently handle this case.
4079 // In order for this transformation to be safe, the LHS must be of the
4080 // form X*(2^n) and the Or constant must be less than 2^n.
4081 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4082 const SCEV *LHS = getSCEV(U->getOperand(0));
4083 const APInt &CIVal = CI->getValue();
4084 if (GetMinTrailingZeros(LHS) >=
4085 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
4086 // Build a plain add SCEV.
4087 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
4088 // If the LHS of the add was an addrec and it has no-wrap flags,
4089 // transfer the no-wrap flags, since an or won't introduce a wrap.
4090 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
4091 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
4092 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
4093 OldAR->getNoWrapFlags());
4099 case Instruction::Xor:
4100 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4101 // If the RHS of the xor is a signbit, then this is just an add.
4102 // Instcombine turns add of signbit into xor as a strength reduction step.
4103 if (CI->getValue().isSignBit())
4104 return getAddExpr(getSCEV(U->getOperand(0)),
4105 getSCEV(U->getOperand(1)));
4107 // If the RHS of xor is -1, then this is a not operation.
4108 if (CI->isAllOnesValue())
4109 return getNotSCEV(getSCEV(U->getOperand(0)));
4111 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
4112 // This is a variant of the check for xor with -1, and it handles
4113 // the case where instcombine has trimmed non-demanded bits out
4114 // of an xor with -1.
4115 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
4116 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
4117 if (BO->getOpcode() == Instruction::And &&
4118 LCI->getValue() == CI->getValue())
4119 if (const SCEVZeroExtendExpr *Z =
4120 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
4121 Type *UTy = U->getType();
4122 const SCEV *Z0 = Z->getOperand();
4123 Type *Z0Ty = Z0->getType();
4124 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
4126 // If C is a low-bits mask, the zero extend is serving to
4127 // mask off the high bits. Complement the operand and
4128 // re-apply the zext.
4129 if (APIntOps::isMask(Z0TySize, CI->getValue()))
4130 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
4132 // If C is a single bit, it may be in the sign-bit position
4133 // before the zero-extend. In this case, represent the xor
4134 // using an add, which is equivalent, and re-apply the zext.
4135 APInt Trunc = CI->getValue().trunc(Z0TySize);
4136 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
4138 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
4144 case Instruction::Shl:
4145 // Turn shift left of a constant amount into a multiply.
4146 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4147 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4149 // If the shift count is not less than the bitwidth, the result of
4150 // the shift is undefined. Don't try to analyze it, because the
4151 // resolution chosen here may differ from the resolution chosen in
4152 // other parts of the compiler.
4153 if (SA->getValue().uge(BitWidth))
4156 Constant *X = ConstantInt::get(getContext(),
4157 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4158 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4162 case Instruction::LShr:
4163 // Turn logical shift right of a constant into a unsigned divide.
4164 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4165 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4167 // If the shift count is not less than the bitwidth, the result of
4168 // the shift is undefined. Don't try to analyze it, because the
4169 // resolution chosen here may differ from the resolution chosen in
4170 // other parts of the compiler.
4171 if (SA->getValue().uge(BitWidth))
4174 Constant *X = ConstantInt::get(getContext(),
4175 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4176 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4180 case Instruction::AShr:
4181 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
4182 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
4183 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
4184 if (L->getOpcode() == Instruction::Shl &&
4185 L->getOperand(1) == U->getOperand(1)) {
4186 uint64_t BitWidth = getTypeSizeInBits(U->getType());
4188 // If the shift count is not less than the bitwidth, the result of
4189 // the shift is undefined. Don't try to analyze it, because the
4190 // resolution chosen here may differ from the resolution chosen in
4191 // other parts of the compiler.
4192 if (CI->getValue().uge(BitWidth))
4195 uint64_t Amt = BitWidth - CI->getZExtValue();
4196 if (Amt == BitWidth)
4197 return getSCEV(L->getOperand(0)); // shift by zero --> noop
4199 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
4200 IntegerType::get(getContext(),
4206 case Instruction::Trunc:
4207 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
4209 case Instruction::ZExt:
4210 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4212 case Instruction::SExt:
4213 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4215 case Instruction::BitCast:
4216 // BitCasts are no-op casts so we just eliminate the cast.
4217 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
4218 return getSCEV(U->getOperand(0));
4221 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
4222 // lead to pointer expressions which cannot safely be expanded to GEPs,
4223 // because ScalarEvolution doesn't respect the GEP aliasing rules when
4224 // simplifying integer expressions.
4226 case Instruction::GetElementPtr:
4227 return createNodeForGEP(cast<GEPOperator>(U));
4229 case Instruction::PHI:
4230 return createNodeForPHI(cast<PHINode>(U));
4232 case Instruction::Select:
4233 // This could be a smax or umax that was lowered earlier.
4234 // Try to recover it.
4235 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
4236 Value *LHS = ICI->getOperand(0);
4237 Value *RHS = ICI->getOperand(1);
4238 switch (ICI->getPredicate()) {
4239 case ICmpInst::ICMP_SLT:
4240 case ICmpInst::ICMP_SLE:
4241 std::swap(LHS, RHS);
4243 case ICmpInst::ICMP_SGT:
4244 case ICmpInst::ICMP_SGE:
4245 // a >s b ? a+x : b+x -> smax(a, b)+x
4246 // a >s b ? b+x : a+x -> smin(a, b)+x
4247 if (LHS->getType() == U->getType()) {
4248 const SCEV *LS = getSCEV(LHS);
4249 const SCEV *RS = getSCEV(RHS);
4250 const SCEV *LA = getSCEV(U->getOperand(1));
4251 const SCEV *RA = getSCEV(U->getOperand(2));
4252 const SCEV *LDiff = getMinusSCEV(LA, LS);
4253 const SCEV *RDiff = getMinusSCEV(RA, RS);
4255 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
4256 LDiff = getMinusSCEV(LA, RS);
4257 RDiff = getMinusSCEV(RA, LS);
4259 return getAddExpr(getSMinExpr(LS, RS), LDiff);
4262 case ICmpInst::ICMP_ULT:
4263 case ICmpInst::ICMP_ULE:
4264 std::swap(LHS, RHS);
4266 case ICmpInst::ICMP_UGT:
4267 case ICmpInst::ICMP_UGE:
4268 // a >u b ? a+x : b+x -> umax(a, b)+x
4269 // a >u b ? b+x : a+x -> umin(a, b)+x
4270 if (LHS->getType() == U->getType()) {
4271 const SCEV *LS = getSCEV(LHS);
4272 const SCEV *RS = getSCEV(RHS);
4273 const SCEV *LA = getSCEV(U->getOperand(1));
4274 const SCEV *RA = getSCEV(U->getOperand(2));
4275 const SCEV *LDiff = getMinusSCEV(LA, LS);
4276 const SCEV *RDiff = getMinusSCEV(RA, RS);
4278 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
4279 LDiff = getMinusSCEV(LA, RS);
4280 RDiff = getMinusSCEV(RA, LS);
4282 return getAddExpr(getUMinExpr(LS, RS), LDiff);
4285 case ICmpInst::ICMP_NE:
4286 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
4287 if (LHS->getType() == U->getType() &&
4288 isa<ConstantInt>(RHS) &&
4289 cast<ConstantInt>(RHS)->isZero()) {
4290 const SCEV *One = getConstant(LHS->getType(), 1);
4291 const SCEV *LS = getSCEV(LHS);
4292 const SCEV *LA = getSCEV(U->getOperand(1));
4293 const SCEV *RA = getSCEV(U->getOperand(2));
4294 const SCEV *LDiff = getMinusSCEV(LA, LS);
4295 const SCEV *RDiff = getMinusSCEV(RA, One);
4297 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4300 case ICmpInst::ICMP_EQ:
4301 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4302 if (LHS->getType() == U->getType() &&
4303 isa<ConstantInt>(RHS) &&
4304 cast<ConstantInt>(RHS)->isZero()) {
4305 const SCEV *One = getConstant(LHS->getType(), 1);
4306 const SCEV *LS = getSCEV(LHS);
4307 const SCEV *LA = getSCEV(U->getOperand(1));
4308 const SCEV *RA = getSCEV(U->getOperand(2));
4309 const SCEV *LDiff = getMinusSCEV(LA, One);
4310 const SCEV *RDiff = getMinusSCEV(RA, LS);
4312 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4320 default: // We cannot analyze this expression.
4324 return getUnknown(V);
4329 //===----------------------------------------------------------------------===//
4330 // Iteration Count Computation Code
4333 /// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
4334 /// normal unsigned value. Returns 0 if the trip count is unknown or not
4335 /// constant. Will also return 0 if the maximum trip count is very large (>=
4338 /// This "trip count" assumes that control exits via ExitingBlock. More
4339 /// precisely, it is the number of times that control may reach ExitingBlock
4340 /// before taking the branch. For loops with multiple exits, it may not be the
4341 /// number times that the loop header executes because the loop may exit
4342 /// prematurely via another branch.
4343 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
4344 BasicBlock *ExitingBlock) {
4345 const SCEVConstant *ExitCount =
4346 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
4350 ConstantInt *ExitConst = ExitCount->getValue();
4352 // Guard against huge trip counts.
4353 if (ExitConst->getValue().getActiveBits() > 32)
4356 // In case of integer overflow, this returns 0, which is correct.
4357 return ((unsigned)ExitConst->getZExtValue()) + 1;
4360 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
4361 /// trip count of this loop as a normal unsigned value, if possible. This
4362 /// means that the actual trip count is always a multiple of the returned
4363 /// value (don't forget the trip count could very well be zero as well!).
4365 /// Returns 1 if the trip count is unknown or not guaranteed to be the
4366 /// multiple of a constant (which is also the case if the trip count is simply
4367 /// constant, use getSmallConstantTripCount for that case), Will also return 1
4368 /// if the trip count is very large (>= 2^32).
4370 /// As explained in the comments for getSmallConstantTripCount, this assumes
4371 /// that control exits the loop via ExitingBlock.
4373 ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
4374 BasicBlock *ExitingBlock) {
4375 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
4376 if (ExitCount == getCouldNotCompute())
4379 // Get the trip count from the BE count by adding 1.
4380 const SCEV *TCMul = getAddExpr(ExitCount,
4381 getConstant(ExitCount->getType(), 1));
4382 // FIXME: SCEV distributes multiplication as V1*C1 + V2*C1. We could attempt
4383 // to factor simple cases.
4384 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(TCMul))
4385 TCMul = Mul->getOperand(0);
4387 const SCEVConstant *MulC = dyn_cast<SCEVConstant>(TCMul);
4391 ConstantInt *Result = MulC->getValue();
4393 // Guard against huge trip counts (this requires checking
4394 // for zero to handle the case where the trip count == -1 and the
4396 if (!Result || Result->getValue().getActiveBits() > 32 ||
4397 Result->getValue().getActiveBits() == 0)
4400 return (unsigned)Result->getZExtValue();
4403 // getExitCount - Get the expression for the number of loop iterations for which
4404 // this loop is guaranteed not to exit via ExitingBlock. Otherwise return
4405 // SCEVCouldNotCompute.
4406 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
4407 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
4410 /// getBackedgeTakenCount - If the specified loop has a predictable
4411 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
4412 /// object. The backedge-taken count is the number of times the loop header
4413 /// will be branched to from within the loop. This is one less than the
4414 /// trip count of the loop, since it doesn't count the first iteration,
4415 /// when the header is branched to from outside the loop.
4417 /// Note that it is not valid to call this method on a loop without a
4418 /// loop-invariant backedge-taken count (see
4419 /// hasLoopInvariantBackedgeTakenCount).
4421 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
4422 return getBackedgeTakenInfo(L).getExact(this);
4425 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
4426 /// return the least SCEV value that is known never to be less than the
4427 /// actual backedge taken count.
4428 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
4429 return getBackedgeTakenInfo(L).getMax(this);
4432 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
4433 /// onto the given Worklist.
4435 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
4436 BasicBlock *Header = L->getHeader();
4438 // Push all Loop-header PHIs onto the Worklist stack.
4439 for (BasicBlock::iterator I = Header->begin();
4440 PHINode *PN = dyn_cast<PHINode>(I); ++I)
4441 Worklist.push_back(PN);
4444 const ScalarEvolution::BackedgeTakenInfo &
4445 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
4446 // Initially insert an invalid entry for this loop. If the insertion
4447 // succeeds, proceed to actually compute a backedge-taken count and
4448 // update the value. The temporary CouldNotCompute value tells SCEV
4449 // code elsewhere that it shouldn't attempt to request a new
4450 // backedge-taken count, which could result in infinite recursion.
4451 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
4452 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
4454 return Pair.first->second;
4456 // ComputeBackedgeTakenCount may allocate memory for its result. Inserting it
4457 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
4458 // must be cleared in this scope.
4459 BackedgeTakenInfo Result = ComputeBackedgeTakenCount(L);
4461 if (Result.getExact(this) != getCouldNotCompute()) {
4462 assert(isLoopInvariant(Result.getExact(this), L) &&
4463 isLoopInvariant(Result.getMax(this), L) &&
4464 "Computed backedge-taken count isn't loop invariant for loop!");
4465 ++NumTripCountsComputed;
4467 else if (Result.getMax(this) == getCouldNotCompute() &&
4468 isa<PHINode>(L->getHeader()->begin())) {
4469 // Only count loops that have phi nodes as not being computable.
4470 ++NumTripCountsNotComputed;
4473 // Now that we know more about the trip count for this loop, forget any
4474 // existing SCEV values for PHI nodes in this loop since they are only
4475 // conservative estimates made without the benefit of trip count
4476 // information. This is similar to the code in forgetLoop, except that
4477 // it handles SCEVUnknown PHI nodes specially.
4478 if (Result.hasAnyInfo()) {
4479 SmallVector<Instruction *, 16> Worklist;
4480 PushLoopPHIs(L, Worklist);
4482 SmallPtrSet<Instruction *, 8> Visited;
4483 while (!Worklist.empty()) {
4484 Instruction *I = Worklist.pop_back_val();
4485 if (!Visited.insert(I)) continue;
4487 ValueExprMapType::iterator It =
4488 ValueExprMap.find_as(static_cast<Value *>(I));
4489 if (It != ValueExprMap.end()) {
4490 const SCEV *Old = It->second;
4492 // SCEVUnknown for a PHI either means that it has an unrecognized
4493 // structure, or it's a PHI that's in the progress of being computed
4494 // by createNodeForPHI. In the former case, additional loop trip
4495 // count information isn't going to change anything. In the later
4496 // case, createNodeForPHI will perform the necessary updates on its
4497 // own when it gets to that point.
4498 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
4499 forgetMemoizedResults(Old);
4500 ValueExprMap.erase(It);
4502 if (PHINode *PN = dyn_cast<PHINode>(I))
4503 ConstantEvolutionLoopExitValue.erase(PN);
4506 PushDefUseChildren(I, Worklist);
4510 // Re-lookup the insert position, since the call to
4511 // ComputeBackedgeTakenCount above could result in a
4512 // recusive call to getBackedgeTakenInfo (on a different
4513 // loop), which would invalidate the iterator computed
4515 return BackedgeTakenCounts.find(L)->second = Result;
4518 /// forgetLoop - This method should be called by the client when it has
4519 /// changed a loop in a way that may effect ScalarEvolution's ability to
4520 /// compute a trip count, or if the loop is deleted.
4521 void ScalarEvolution::forgetLoop(const Loop *L) {
4522 // Drop any stored trip count value.
4523 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
4524 BackedgeTakenCounts.find(L);
4525 if (BTCPos != BackedgeTakenCounts.end()) {
4526 BTCPos->second.clear();
4527 BackedgeTakenCounts.erase(BTCPos);
4530 // Drop information about expressions based on loop-header PHIs.
4531 SmallVector<Instruction *, 16> Worklist;
4532 PushLoopPHIs(L, Worklist);
4534 SmallPtrSet<Instruction *, 8> Visited;
4535 while (!Worklist.empty()) {
4536 Instruction *I = Worklist.pop_back_val();
4537 if (!Visited.insert(I)) continue;
4539 ValueExprMapType::iterator It =
4540 ValueExprMap.find_as(static_cast<Value *>(I));
4541 if (It != ValueExprMap.end()) {
4542 forgetMemoizedResults(It->second);
4543 ValueExprMap.erase(It);
4544 if (PHINode *PN = dyn_cast<PHINode>(I))
4545 ConstantEvolutionLoopExitValue.erase(PN);
4548 PushDefUseChildren(I, Worklist);
4551 // Forget all contained loops too, to avoid dangling entries in the
4552 // ValuesAtScopes map.
4553 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
4557 /// forgetValue - This method should be called by the client when it has
4558 /// changed a value in a way that may effect its value, or which may
4559 /// disconnect it from a def-use chain linking it to a loop.
4560 void ScalarEvolution::forgetValue(Value *V) {
4561 Instruction *I = dyn_cast<Instruction>(V);
4564 // Drop information about expressions based on loop-header PHIs.
4565 SmallVector<Instruction *, 16> Worklist;
4566 Worklist.push_back(I);
4568 SmallPtrSet<Instruction *, 8> Visited;
4569 while (!Worklist.empty()) {
4570 I = Worklist.pop_back_val();
4571 if (!Visited.insert(I)) continue;
4573 ValueExprMapType::iterator It =
4574 ValueExprMap.find_as(static_cast<Value *>(I));
4575 if (It != ValueExprMap.end()) {
4576 forgetMemoizedResults(It->second);
4577 ValueExprMap.erase(It);
4578 if (PHINode *PN = dyn_cast<PHINode>(I))
4579 ConstantEvolutionLoopExitValue.erase(PN);
4582 PushDefUseChildren(I, Worklist);
4586 /// getExact - Get the exact loop backedge taken count considering all loop
4587 /// exits. A computable result can only be return for loops with a single exit.
4588 /// Returning the minimum taken count among all exits is incorrect because one
4589 /// of the loop's exit limit's may have been skipped. HowFarToZero assumes that
4590 /// the limit of each loop test is never skipped. This is a valid assumption as
4591 /// long as the loop exits via that test. For precise results, it is the
4592 /// caller's responsibility to specify the relevant loop exit using
4593 /// getExact(ExitingBlock, SE).
4595 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
4596 // If any exits were not computable, the loop is not computable.
4597 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
4599 // We need exactly one computable exit.
4600 if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
4601 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
4603 const SCEV *BECount = nullptr;
4604 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4605 ENT != nullptr; ENT = ENT->getNextExit()) {
4607 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
4610 BECount = ENT->ExactNotTaken;
4611 else if (BECount != ENT->ExactNotTaken)
4612 return SE->getCouldNotCompute();
4614 assert(BECount && "Invalid not taken count for loop exit");
4618 /// getExact - Get the exact not taken count for this loop exit.
4620 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
4621 ScalarEvolution *SE) const {
4622 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4623 ENT != nullptr; ENT = ENT->getNextExit()) {
4625 if (ENT->ExitingBlock == ExitingBlock)
4626 return ENT->ExactNotTaken;
4628 return SE->getCouldNotCompute();
4631 /// getMax - Get the max backedge taken count for the loop.
4633 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
4634 return Max ? Max : SE->getCouldNotCompute();
4637 bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
4638 ScalarEvolution *SE) const {
4639 if (Max && Max != SE->getCouldNotCompute() && SE->hasOperand(Max, S))
4642 if (!ExitNotTaken.ExitingBlock)
4645 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4646 ENT != nullptr; ENT = ENT->getNextExit()) {
4648 if (ENT->ExactNotTaken != SE->getCouldNotCompute()
4649 && SE->hasOperand(ENT->ExactNotTaken, S)) {
4656 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
4657 /// computable exit into a persistent ExitNotTakenInfo array.
4658 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
4659 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
4660 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
4663 ExitNotTaken.setIncomplete();
4665 unsigned NumExits = ExitCounts.size();
4666 if (NumExits == 0) return;
4668 ExitNotTaken.ExitingBlock = ExitCounts[0].first;
4669 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
4670 if (NumExits == 1) return;
4672 // Handle the rare case of multiple computable exits.
4673 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
4675 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
4676 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
4677 PrevENT->setNextExit(ENT);
4678 ENT->ExitingBlock = ExitCounts[i].first;
4679 ENT->ExactNotTaken = ExitCounts[i].second;
4683 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
4684 void ScalarEvolution::BackedgeTakenInfo::clear() {
4685 ExitNotTaken.ExitingBlock = nullptr;
4686 ExitNotTaken.ExactNotTaken = nullptr;
4687 delete[] ExitNotTaken.getNextExit();
4690 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
4691 /// of the specified loop will execute.
4692 ScalarEvolution::BackedgeTakenInfo
4693 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
4694 SmallVector<BasicBlock *, 8> ExitingBlocks;
4695 L->getExitingBlocks(ExitingBlocks);
4697 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
4698 bool CouldComputeBECount = true;
4699 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
4700 const SCEV *MustExitMaxBECount = nullptr;
4701 const SCEV *MayExitMaxBECount = nullptr;
4703 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
4704 // and compute maxBECount.
4705 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
4706 BasicBlock *ExitBB = ExitingBlocks[i];
4707 ExitLimit EL = ComputeExitLimit(L, ExitBB);
4709 // 1. For each exit that can be computed, add an entry to ExitCounts.
4710 // CouldComputeBECount is true only if all exits can be computed.
4711 if (EL.Exact == getCouldNotCompute())
4712 // We couldn't compute an exact value for this exit, so
4713 // we won't be able to compute an exact value for the loop.
4714 CouldComputeBECount = false;
4716 ExitCounts.push_back(std::make_pair(ExitBB, EL.Exact));
4718 // 2. Derive the loop's MaxBECount from each exit's max number of
4719 // non-exiting iterations. Partition the loop exits into two kinds:
4720 // LoopMustExits and LoopMayExits.
4722 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
4723 // is a LoopMayExit. If any computable LoopMustExit is found, then
4724 // MaxBECount is the minimum EL.Max of computable LoopMustExits. Otherwise,
4725 // MaxBECount is conservatively the maximum EL.Max, where CouldNotCompute is
4726 // considered greater than any computable EL.Max.
4727 if (EL.Max != getCouldNotCompute() && Latch &&
4728 DT->dominates(ExitBB, Latch)) {
4729 if (!MustExitMaxBECount)
4730 MustExitMaxBECount = EL.Max;
4732 MustExitMaxBECount =
4733 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.Max);
4735 } else if (MayExitMaxBECount != getCouldNotCompute()) {
4736 if (!MayExitMaxBECount || EL.Max == getCouldNotCompute())
4737 MayExitMaxBECount = EL.Max;
4740 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.Max);
4744 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
4745 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
4746 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
4749 /// ComputeExitLimit - Compute the number of times the backedge of the specified
4750 /// loop will execute if it exits via the specified block.
4751 ScalarEvolution::ExitLimit
4752 ScalarEvolution::ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
4754 // Okay, we've chosen an exiting block. See what condition causes us to
4755 // exit at this block and remember the exit block and whether all other targets
4756 // lead to the loop header.
4757 bool MustExecuteLoopHeader = true;
4758 BasicBlock *Exit = nullptr;
4759 for (succ_iterator SI = succ_begin(ExitingBlock), SE = succ_end(ExitingBlock);
4761 if (!L->contains(*SI)) {
4762 if (Exit) // Multiple exit successors.
4763 return getCouldNotCompute();
4765 } else if (*SI != L->getHeader()) {
4766 MustExecuteLoopHeader = false;
4769 // At this point, we know we have a conditional branch that determines whether
4770 // the loop is exited. However, we don't know if the branch is executed each
4771 // time through the loop. If not, then the execution count of the branch will
4772 // not be equal to the trip count of the loop.
4774 // Currently we check for this by checking to see if the Exit branch goes to
4775 // the loop header. If so, we know it will always execute the same number of
4776 // times as the loop. We also handle the case where the exit block *is* the
4777 // loop header. This is common for un-rotated loops.
4779 // If both of those tests fail, walk up the unique predecessor chain to the
4780 // header, stopping if there is an edge that doesn't exit the loop. If the
4781 // header is reached, the execution count of the branch will be equal to the
4782 // trip count of the loop.
4784 // More extensive analysis could be done to handle more cases here.
4786 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
4787 // The simple checks failed, try climbing the unique predecessor chain
4788 // up to the header.
4790 for (BasicBlock *BB = ExitingBlock; BB; ) {
4791 BasicBlock *Pred = BB->getUniquePredecessor();
4793 return getCouldNotCompute();
4794 TerminatorInst *PredTerm = Pred->getTerminator();
4795 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
4796 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
4799 // If the predecessor has a successor that isn't BB and isn't
4800 // outside the loop, assume the worst.
4801 if (L->contains(PredSucc))
4802 return getCouldNotCompute();
4804 if (Pred == L->getHeader()) {
4811 return getCouldNotCompute();
4814 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
4815 TerminatorInst *Term = ExitingBlock->getTerminator();
4816 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
4817 assert(BI->isConditional() && "If unconditional, it can't be in loop!");
4818 // Proceed to the next level to examine the exit condition expression.
4819 return ComputeExitLimitFromCond(L, BI->getCondition(), BI->getSuccessor(0),
4820 BI->getSuccessor(1),
4821 /*ControlsExit=*/IsOnlyExit);
4824 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
4825 return ComputeExitLimitFromSingleExitSwitch(L, SI, Exit,
4826 /*ControlsExit=*/IsOnlyExit);
4828 return getCouldNotCompute();
4831 /// ComputeExitLimitFromCond - Compute the number of times the
4832 /// backedge of the specified loop will execute if its exit condition
4833 /// were a conditional branch of ExitCond, TBB, and FBB.
4835 /// @param ControlsExit is true if ExitCond directly controls the exit
4836 /// branch. In this case, we can assume that the loop exits only if the
4837 /// condition is true and can infer that failing to meet the condition prior to
4838 /// integer wraparound results in undefined behavior.
4839 ScalarEvolution::ExitLimit
4840 ScalarEvolution::ComputeExitLimitFromCond(const Loop *L,
4844 bool ControlsExit) {
4845 // Check if the controlling expression for this loop is an And or Or.
4846 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
4847 if (BO->getOpcode() == Instruction::And) {
4848 // Recurse on the operands of the and.
4849 bool EitherMayExit = L->contains(TBB);
4850 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
4851 ControlsExit && !EitherMayExit);
4852 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
4853 ControlsExit && !EitherMayExit);
4854 const SCEV *BECount = getCouldNotCompute();
4855 const SCEV *MaxBECount = getCouldNotCompute();
4856 if (EitherMayExit) {
4857 // Both conditions must be true for the loop to continue executing.
4858 // Choose the less conservative count.
4859 if (EL0.Exact == getCouldNotCompute() ||
4860 EL1.Exact == getCouldNotCompute())
4861 BECount = getCouldNotCompute();
4863 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4864 if (EL0.Max == getCouldNotCompute())
4865 MaxBECount = EL1.Max;
4866 else if (EL1.Max == getCouldNotCompute())
4867 MaxBECount = EL0.Max;
4869 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4871 // Both conditions must be true at the same time for the loop to exit.
4872 // For now, be conservative.
4873 assert(L->contains(FBB) && "Loop block has no successor in loop!");
4874 if (EL0.Max == EL1.Max)
4875 MaxBECount = EL0.Max;
4876 if (EL0.Exact == EL1.Exact)
4877 BECount = EL0.Exact;
4880 return ExitLimit(BECount, MaxBECount);
4882 if (BO->getOpcode() == Instruction::Or) {
4883 // Recurse on the operands of the or.
4884 bool EitherMayExit = L->contains(FBB);
4885 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
4886 ControlsExit && !EitherMayExit);
4887 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
4888 ControlsExit && !EitherMayExit);
4889 const SCEV *BECount = getCouldNotCompute();
4890 const SCEV *MaxBECount = getCouldNotCompute();
4891 if (EitherMayExit) {
4892 // Both conditions must be false for the loop to continue executing.
4893 // Choose the less conservative count.
4894 if (EL0.Exact == getCouldNotCompute() ||
4895 EL1.Exact == getCouldNotCompute())
4896 BECount = getCouldNotCompute();
4898 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4899 if (EL0.Max == getCouldNotCompute())
4900 MaxBECount = EL1.Max;
4901 else if (EL1.Max == getCouldNotCompute())
4902 MaxBECount = EL0.Max;
4904 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4906 // Both conditions must be false at the same time for the loop to exit.
4907 // For now, be conservative.
4908 assert(L->contains(TBB) && "Loop block has no successor in loop!");
4909 if (EL0.Max == EL1.Max)
4910 MaxBECount = EL0.Max;
4911 if (EL0.Exact == EL1.Exact)
4912 BECount = EL0.Exact;
4915 return ExitLimit(BECount, MaxBECount);
4919 // With an icmp, it may be feasible to compute an exact backedge-taken count.
4920 // Proceed to the next level to examine the icmp.
4921 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
4922 return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
4924 // Check for a constant condition. These are normally stripped out by
4925 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
4926 // preserve the CFG and is temporarily leaving constant conditions
4928 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
4929 if (L->contains(FBB) == !CI->getZExtValue())
4930 // The backedge is always taken.
4931 return getCouldNotCompute();
4933 // The backedge is never taken.
4934 return getConstant(CI->getType(), 0);
4937 // If it's not an integer or pointer comparison then compute it the hard way.
4938 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
4941 /// ComputeExitLimitFromICmp - Compute the number of times the
4942 /// backedge of the specified loop will execute if its exit condition
4943 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4944 ScalarEvolution::ExitLimit
4945 ScalarEvolution::ComputeExitLimitFromICmp(const Loop *L,
4949 bool ControlsExit) {
4951 // If the condition was exit on true, convert the condition to exit on false
4952 ICmpInst::Predicate Cond;
4953 if (!L->contains(FBB))
4954 Cond = ExitCond->getPredicate();
4956 Cond = ExitCond->getInversePredicate();
4958 // Handle common loops like: for (X = "string"; *X; ++X)
4959 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4960 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4962 ComputeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
4963 if (ItCnt.hasAnyInfo())
4967 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4968 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4970 // Try to evaluate any dependencies out of the loop.
4971 LHS = getSCEVAtScope(LHS, L);
4972 RHS = getSCEVAtScope(RHS, L);
4974 // At this point, we would like to compute how many iterations of the
4975 // loop the predicate will return true for these inputs.
4976 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
4977 // If there is a loop-invariant, force it into the RHS.
4978 std::swap(LHS, RHS);
4979 Cond = ICmpInst::getSwappedPredicate(Cond);
4982 // Simplify the operands before analyzing them.
4983 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4985 // If we have a comparison of a chrec against a constant, try to use value
4986 // ranges to answer this query.
4987 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4988 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4989 if (AddRec->getLoop() == L) {
4990 // Form the constant range.
4991 ConstantRange CompRange(
4992 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4994 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4995 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4999 case ICmpInst::ICMP_NE: { // while (X != Y)
5000 // Convert to: while (X-Y != 0)
5001 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5002 if (EL.hasAnyInfo()) return EL;
5005 case ICmpInst::ICMP_EQ: { // while (X == Y)
5006 // Convert to: while (X-Y == 0)
5007 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
5008 if (EL.hasAnyInfo()) return EL;
5011 case ICmpInst::ICMP_SLT:
5012 case ICmpInst::ICMP_ULT: { // while (X < Y)
5013 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
5014 ExitLimit EL = HowManyLessThans(LHS, RHS, L, IsSigned, ControlsExit);
5015 if (EL.hasAnyInfo()) return EL;
5018 case ICmpInst::ICMP_SGT:
5019 case ICmpInst::ICMP_UGT: { // while (X > Y)
5020 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
5021 ExitLimit EL = HowManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit);
5022 if (EL.hasAnyInfo()) return EL;
5027 dbgs() << "ComputeBackedgeTakenCount ";
5028 if (ExitCond->getOperand(0)->getType()->isUnsigned())
5029 dbgs() << "[unsigned] ";
5030 dbgs() << *LHS << " "
5031 << Instruction::getOpcodeName(Instruction::ICmp)
5032 << " " << *RHS << "\n";
5036 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5039 ScalarEvolution::ExitLimit
5040 ScalarEvolution::ComputeExitLimitFromSingleExitSwitch(const Loop *L,
5042 BasicBlock *ExitingBlock,
5043 bool ControlsExit) {
5044 assert(!L->contains(ExitingBlock) && "Not an exiting block!");
5046 // Give up if the exit is the default dest of a switch.
5047 if (Switch->getDefaultDest() == ExitingBlock)
5048 return getCouldNotCompute();
5050 assert(L->contains(Switch->getDefaultDest()) &&
5051 "Default case must not exit the loop!");
5052 const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
5053 const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
5055 // while (X != Y) --> while (X-Y != 0)
5056 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5057 if (EL.hasAnyInfo())
5060 return getCouldNotCompute();
5063 static ConstantInt *
5064 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
5065 ScalarEvolution &SE) {
5066 const SCEV *InVal = SE.getConstant(C);
5067 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
5068 assert(isa<SCEVConstant>(Val) &&
5069 "Evaluation of SCEV at constant didn't fold correctly?");
5070 return cast<SCEVConstant>(Val)->getValue();
5073 /// ComputeLoadConstantCompareExitLimit - Given an exit condition of
5074 /// 'icmp op load X, cst', try to see if we can compute the backedge
5075 /// execution count.
5076 ScalarEvolution::ExitLimit
5077 ScalarEvolution::ComputeLoadConstantCompareExitLimit(
5081 ICmpInst::Predicate predicate) {
5083 if (LI->isVolatile()) return getCouldNotCompute();
5085 // Check to see if the loaded pointer is a getelementptr of a global.
5086 // TODO: Use SCEV instead of manually grubbing with GEPs.
5087 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
5088 if (!GEP) return getCouldNotCompute();
5090 // Make sure that it is really a constant global we are gepping, with an
5091 // initializer, and make sure the first IDX is really 0.
5092 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
5093 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
5094 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
5095 !cast<Constant>(GEP->getOperand(1))->isNullValue())
5096 return getCouldNotCompute();
5098 // Okay, we allow one non-constant index into the GEP instruction.
5099 Value *VarIdx = nullptr;
5100 std::vector<Constant*> Indexes;
5101 unsigned VarIdxNum = 0;
5102 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
5103 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
5104 Indexes.push_back(CI);
5105 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
5106 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
5107 VarIdx = GEP->getOperand(i);
5109 Indexes.push_back(nullptr);
5112 // Loop-invariant loads may be a byproduct of loop optimization. Skip them.
5114 return getCouldNotCompute();
5116 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
5117 // Check to see if X is a loop variant variable value now.
5118 const SCEV *Idx = getSCEV(VarIdx);
5119 Idx = getSCEVAtScope(Idx, L);
5121 // We can only recognize very limited forms of loop index expressions, in
5122 // particular, only affine AddRec's like {C1,+,C2}.
5123 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
5124 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
5125 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
5126 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
5127 return getCouldNotCompute();
5129 unsigned MaxSteps = MaxBruteForceIterations;
5130 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
5131 ConstantInt *ItCst = ConstantInt::get(
5132 cast<IntegerType>(IdxExpr->getType()), IterationNum);
5133 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
5135 // Form the GEP offset.
5136 Indexes[VarIdxNum] = Val;
5138 Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
5140 if (!Result) break; // Cannot compute!
5142 // Evaluate the condition for this iteration.
5143 Result = ConstantExpr::getICmp(predicate, Result, RHS);
5144 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
5145 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
5147 dbgs() << "\n***\n*** Computed loop count " << *ItCst
5148 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
5151 ++NumArrayLenItCounts;
5152 return getConstant(ItCst); // Found terminating iteration!
5155 return getCouldNotCompute();
5159 /// CanConstantFold - Return true if we can constant fold an instruction of the
5160 /// specified type, assuming that all operands were constants.
5161 static bool CanConstantFold(const Instruction *I) {
5162 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
5163 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
5167 if (const CallInst *CI = dyn_cast<CallInst>(I))
5168 if (const Function *F = CI->getCalledFunction())
5169 return canConstantFoldCallTo(F);
5173 /// Determine whether this instruction can constant evolve within this loop
5174 /// assuming its operands can all constant evolve.
5175 static bool canConstantEvolve(Instruction *I, const Loop *L) {
5176 // An instruction outside of the loop can't be derived from a loop PHI.
5177 if (!L->contains(I)) return false;
5179 if (isa<PHINode>(I)) {
5180 if (L->getHeader() == I->getParent())
5183 // We don't currently keep track of the control flow needed to evaluate
5184 // PHIs, so we cannot handle PHIs inside of loops.
5188 // If we won't be able to constant fold this expression even if the operands
5189 // are constants, bail early.
5190 return CanConstantFold(I);
5193 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
5194 /// recursing through each instruction operand until reaching a loop header phi.
5196 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
5197 DenseMap<Instruction *, PHINode *> &PHIMap) {
5199 // Otherwise, we can evaluate this instruction if all of its operands are
5200 // constant or derived from a PHI node themselves.
5201 PHINode *PHI = nullptr;
5202 for (Instruction::op_iterator OpI = UseInst->op_begin(),
5203 OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
5205 if (isa<Constant>(*OpI)) continue;
5207 Instruction *OpInst = dyn_cast<Instruction>(*OpI);
5208 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
5210 PHINode *P = dyn_cast<PHINode>(OpInst);
5212 // If this operand is already visited, reuse the prior result.
5213 // We may have P != PHI if this is the deepest point at which the
5214 // inconsistent paths meet.
5215 P = PHIMap.lookup(OpInst);
5217 // Recurse and memoize the results, whether a phi is found or not.
5218 // This recursive call invalidates pointers into PHIMap.
5219 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
5223 return nullptr; // Not evolving from PHI
5224 if (PHI && PHI != P)
5225 return nullptr; // Evolving from multiple different PHIs.
5228 // This is a expression evolving from a constant PHI!
5232 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
5233 /// in the loop that V is derived from. We allow arbitrary operations along the
5234 /// way, but the operands of an operation must either be constants or a value
5235 /// derived from a constant PHI. If this expression does not fit with these
5236 /// constraints, return null.
5237 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
5238 Instruction *I = dyn_cast<Instruction>(V);
5239 if (!I || !canConstantEvolve(I, L)) return nullptr;
5241 if (PHINode *PN = dyn_cast<PHINode>(I)) {
5245 // Record non-constant instructions contained by the loop.
5246 DenseMap<Instruction *, PHINode *> PHIMap;
5247 return getConstantEvolvingPHIOperands(I, L, PHIMap);
5250 /// EvaluateExpression - Given an expression that passes the
5251 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
5252 /// in the loop has the value PHIVal. If we can't fold this expression for some
5253 /// reason, return null.
5254 static Constant *EvaluateExpression(Value *V, const Loop *L,
5255 DenseMap<Instruction *, Constant *> &Vals,
5256 const DataLayout *DL,
5257 const TargetLibraryInfo *TLI) {
5258 // Convenient constant check, but redundant for recursive calls.
5259 if (Constant *C = dyn_cast<Constant>(V)) return C;
5260 Instruction *I = dyn_cast<Instruction>(V);
5261 if (!I) return nullptr;
5263 if (Constant *C = Vals.lookup(I)) return C;
5265 // An instruction inside the loop depends on a value outside the loop that we
5266 // weren't given a mapping for, or a value such as a call inside the loop.
5267 if (!canConstantEvolve(I, L)) return nullptr;
5269 // An unmapped PHI can be due to a branch or another loop inside this loop,
5270 // or due to this not being the initial iteration through a loop where we
5271 // couldn't compute the evolution of this particular PHI last time.
5272 if (isa<PHINode>(I)) return nullptr;
5274 std::vector<Constant*> Operands(I->getNumOperands());
5276 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5277 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
5279 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
5280 if (!Operands[i]) return nullptr;
5283 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
5285 if (!C) return nullptr;
5289 if (CmpInst *CI = dyn_cast<CmpInst>(I))
5290 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
5291 Operands[1], DL, TLI);
5292 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
5293 if (!LI->isVolatile())
5294 return ConstantFoldLoadFromConstPtr(Operands[0], DL);
5296 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, DL,
5300 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
5301 /// in the header of its containing loop, we know the loop executes a
5302 /// constant number of times, and the PHI node is just a recurrence
5303 /// involving constants, fold it.
5305 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
5308 DenseMap<PHINode*, Constant*>::const_iterator I =
5309 ConstantEvolutionLoopExitValue.find(PN);
5310 if (I != ConstantEvolutionLoopExitValue.end())
5313 if (BEs.ugt(MaxBruteForceIterations))
5314 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
5316 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
5318 DenseMap<Instruction *, Constant *> CurrentIterVals;
5319 BasicBlock *Header = L->getHeader();
5320 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5322 // Since the loop is canonicalized, the PHI node must have two entries. One
5323 // entry must be a constant (coming in from outside of the loop), and the
5324 // second must be derived from the same PHI.
5325 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
5326 PHINode *PHI = nullptr;
5327 for (BasicBlock::iterator I = Header->begin();
5328 (PHI = dyn_cast<PHINode>(I)); ++I) {
5329 Constant *StartCST =
5330 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
5331 if (!StartCST) continue;
5332 CurrentIterVals[PHI] = StartCST;
5334 if (!CurrentIterVals.count(PN))
5335 return RetVal = nullptr;
5337 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
5339 // Execute the loop symbolically to determine the exit value.
5340 if (BEs.getActiveBits() >= 32)
5341 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
5343 unsigned NumIterations = BEs.getZExtValue(); // must be in range
5344 unsigned IterationNum = 0;
5345 for (; ; ++IterationNum) {
5346 if (IterationNum == NumIterations)
5347 return RetVal = CurrentIterVals[PN]; // Got exit value!
5349 // Compute the value of the PHIs for the next iteration.
5350 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
5351 DenseMap<Instruction *, Constant *> NextIterVals;
5352 Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL,
5355 return nullptr; // Couldn't evaluate!
5356 NextIterVals[PN] = NextPHI;
5358 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
5360 // Also evaluate the other PHI nodes. However, we don't get to stop if we
5361 // cease to be able to evaluate one of them or if they stop evolving,
5362 // because that doesn't necessarily prevent us from computing PN.
5363 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
5364 for (DenseMap<Instruction *, Constant *>::const_iterator
5365 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
5366 PHINode *PHI = dyn_cast<PHINode>(I->first);
5367 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
5368 PHIsToCompute.push_back(std::make_pair(PHI, I->second));
5370 // We use two distinct loops because EvaluateExpression may invalidate any
5371 // iterators into CurrentIterVals.
5372 for (SmallVectorImpl<std::pair<PHINode *, Constant*> >::const_iterator
5373 I = PHIsToCompute.begin(), E = PHIsToCompute.end(); I != E; ++I) {
5374 PHINode *PHI = I->first;
5375 Constant *&NextPHI = NextIterVals[PHI];
5376 if (!NextPHI) { // Not already computed.
5377 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
5378 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
5380 if (NextPHI != I->second)
5381 StoppedEvolving = false;
5384 // If all entries in CurrentIterVals == NextIterVals then we can stop
5385 // iterating, the loop can't continue to change.
5386 if (StoppedEvolving)
5387 return RetVal = CurrentIterVals[PN];
5389 CurrentIterVals.swap(NextIterVals);
5393 /// ComputeExitCountExhaustively - If the loop is known to execute a
5394 /// constant number of times (the condition evolves only from constants),
5395 /// try to evaluate a few iterations of the loop until we get the exit
5396 /// condition gets a value of ExitWhen (true or false). If we cannot
5397 /// evaluate the trip count of the loop, return getCouldNotCompute().
5398 const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
5401 PHINode *PN = getConstantEvolvingPHI(Cond, L);
5402 if (!PN) return getCouldNotCompute();
5404 // If the loop is canonicalized, the PHI will have exactly two entries.
5405 // That's the only form we support here.
5406 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
5408 DenseMap<Instruction *, Constant *> CurrentIterVals;
5409 BasicBlock *Header = L->getHeader();
5410 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5412 // One entry must be a constant (coming in from outside of the loop), and the
5413 // second must be derived from the same PHI.
5414 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
5415 PHINode *PHI = nullptr;
5416 for (BasicBlock::iterator I = Header->begin();
5417 (PHI = dyn_cast<PHINode>(I)); ++I) {
5418 Constant *StartCST =
5419 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
5420 if (!StartCST) continue;
5421 CurrentIterVals[PHI] = StartCST;
5423 if (!CurrentIterVals.count(PN))
5424 return getCouldNotCompute();
5426 // Okay, we find a PHI node that defines the trip count of this loop. Execute
5427 // the loop symbolically to determine when the condition gets a value of
5430 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
5431 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
5432 ConstantInt *CondVal =
5433 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L, CurrentIterVals,
5436 // Couldn't symbolically evaluate.
5437 if (!CondVal) return getCouldNotCompute();
5439 if (CondVal->getValue() == uint64_t(ExitWhen)) {
5440 ++NumBruteForceTripCountsComputed;
5441 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
5444 // Update all the PHI nodes for the next iteration.
5445 DenseMap<Instruction *, Constant *> NextIterVals;
5447 // Create a list of which PHIs we need to compute. We want to do this before
5448 // calling EvaluateExpression on them because that may invalidate iterators
5449 // into CurrentIterVals.
5450 SmallVector<PHINode *, 8> PHIsToCompute;
5451 for (DenseMap<Instruction *, Constant *>::const_iterator
5452 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
5453 PHINode *PHI = dyn_cast<PHINode>(I->first);
5454 if (!PHI || PHI->getParent() != Header) continue;
5455 PHIsToCompute.push_back(PHI);
5457 for (SmallVectorImpl<PHINode *>::const_iterator I = PHIsToCompute.begin(),
5458 E = PHIsToCompute.end(); I != E; ++I) {
5460 Constant *&NextPHI = NextIterVals[PHI];
5461 if (NextPHI) continue; // Already computed!
5463 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
5464 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
5466 CurrentIterVals.swap(NextIterVals);
5469 // Too many iterations were needed to evaluate.
5470 return getCouldNotCompute();
5473 /// getSCEVAtScope - Return a SCEV expression for the specified value
5474 /// at the specified scope in the program. The L value specifies a loop
5475 /// nest to evaluate the expression at, where null is the top-level or a
5476 /// specified loop is immediately inside of the loop.
5478 /// This method can be used to compute the exit value for a variable defined
5479 /// in a loop by querying what the value will hold in the parent loop.
5481 /// In the case that a relevant loop exit value cannot be computed, the
5482 /// original value V is returned.
5483 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
5484 // Check to see if we've folded this expression at this loop before.
5485 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = ValuesAtScopes[V];
5486 for (unsigned u = 0; u < Values.size(); u++) {
5487 if (Values[u].first == L)
5488 return Values[u].second ? Values[u].second : V;
5490 Values.push_back(std::make_pair(L, static_cast<const SCEV *>(nullptr)));
5491 // Otherwise compute it.
5492 const SCEV *C = computeSCEVAtScope(V, L);
5493 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values2 = ValuesAtScopes[V];
5494 for (unsigned u = Values2.size(); u > 0; u--) {
5495 if (Values2[u - 1].first == L) {
5496 Values2[u - 1].second = C;
5503 /// This builds up a Constant using the ConstantExpr interface. That way, we
5504 /// will return Constants for objects which aren't represented by a
5505 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
5506 /// Returns NULL if the SCEV isn't representable as a Constant.
5507 static Constant *BuildConstantFromSCEV(const SCEV *V) {
5508 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
5509 case scCouldNotCompute:
5513 return cast<SCEVConstant>(V)->getValue();
5515 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
5516 case scSignExtend: {
5517 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
5518 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
5519 return ConstantExpr::getSExt(CastOp, SS->getType());
5522 case scZeroExtend: {
5523 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
5524 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
5525 return ConstantExpr::getZExt(CastOp, SZ->getType());
5529 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
5530 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
5531 return ConstantExpr::getTrunc(CastOp, ST->getType());
5535 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
5536 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
5537 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
5538 unsigned AS = PTy->getAddressSpace();
5539 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5540 C = ConstantExpr::getBitCast(C, DestPtrTy);
5542 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
5543 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
5544 if (!C2) return nullptr;
5547 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
5548 unsigned AS = C2->getType()->getPointerAddressSpace();
5550 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5551 // The offsets have been converted to bytes. We can add bytes to an
5552 // i8* by GEP with the byte count in the first index.
5553 C = ConstantExpr::getBitCast(C, DestPtrTy);
5556 // Don't bother trying to sum two pointers. We probably can't
5557 // statically compute a load that results from it anyway.
5558 if (C2->getType()->isPointerTy())
5561 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
5562 if (PTy->getElementType()->isStructTy())
5563 C2 = ConstantExpr::getIntegerCast(
5564 C2, Type::getInt32Ty(C->getContext()), true);
5565 C = ConstantExpr::getGetElementPtr(C, C2);
5567 C = ConstantExpr::getAdd(C, C2);
5574 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
5575 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
5576 // Don't bother with pointers at all.
5577 if (C->getType()->isPointerTy()) return nullptr;
5578 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
5579 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
5580 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
5581 C = ConstantExpr::getMul(C, C2);
5588 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
5589 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
5590 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
5591 if (LHS->getType() == RHS->getType())
5592 return ConstantExpr::getUDiv(LHS, RHS);
5597 break; // TODO: smax, umax.
5602 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
5603 if (isa<SCEVConstant>(V)) return V;
5605 // If this instruction is evolved from a constant-evolving PHI, compute the
5606 // exit value from the loop without using SCEVs.
5607 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
5608 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
5609 const Loop *LI = (*this->LI)[I->getParent()];
5610 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
5611 if (PHINode *PN = dyn_cast<PHINode>(I))
5612 if (PN->getParent() == LI->getHeader()) {
5613 // Okay, there is no closed form solution for the PHI node. Check
5614 // to see if the loop that contains it has a known backedge-taken
5615 // count. If so, we may be able to force computation of the exit
5617 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
5618 if (const SCEVConstant *BTCC =
5619 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
5620 // Okay, we know how many times the containing loop executes. If
5621 // this is a constant evolving PHI node, get the final value at
5622 // the specified iteration number.
5623 Constant *RV = getConstantEvolutionLoopExitValue(PN,
5624 BTCC->getValue()->getValue(),
5626 if (RV) return getSCEV(RV);
5630 // Okay, this is an expression that we cannot symbolically evaluate
5631 // into a SCEV. Check to see if it's possible to symbolically evaluate
5632 // the arguments into constants, and if so, try to constant propagate the
5633 // result. This is particularly useful for computing loop exit values.
5634 if (CanConstantFold(I)) {
5635 SmallVector<Constant *, 4> Operands;
5636 bool MadeImprovement = false;
5637 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5638 Value *Op = I->getOperand(i);
5639 if (Constant *C = dyn_cast<Constant>(Op)) {
5640 Operands.push_back(C);
5644 // If any of the operands is non-constant and if they are
5645 // non-integer and non-pointer, don't even try to analyze them
5646 // with scev techniques.
5647 if (!isSCEVable(Op->getType()))
5650 const SCEV *OrigV = getSCEV(Op);
5651 const SCEV *OpV = getSCEVAtScope(OrigV, L);
5652 MadeImprovement |= OrigV != OpV;
5654 Constant *C = BuildConstantFromSCEV(OpV);
5656 if (C->getType() != Op->getType())
5657 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5661 Operands.push_back(C);
5664 // Check to see if getSCEVAtScope actually made an improvement.
5665 if (MadeImprovement) {
5666 Constant *C = nullptr;
5667 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
5668 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
5669 Operands[0], Operands[1], DL,
5671 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
5672 if (!LI->isVolatile())
5673 C = ConstantFoldLoadFromConstPtr(Operands[0], DL);
5675 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
5683 // This is some other type of SCEVUnknown, just return it.
5687 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
5688 // Avoid performing the look-up in the common case where the specified
5689 // expression has no loop-variant portions.
5690 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
5691 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5692 if (OpAtScope != Comm->getOperand(i)) {
5693 // Okay, at least one of these operands is loop variant but might be
5694 // foldable. Build a new instance of the folded commutative expression.
5695 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
5696 Comm->op_begin()+i);
5697 NewOps.push_back(OpAtScope);
5699 for (++i; i != e; ++i) {
5700 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5701 NewOps.push_back(OpAtScope);
5703 if (isa<SCEVAddExpr>(Comm))
5704 return getAddExpr(NewOps);
5705 if (isa<SCEVMulExpr>(Comm))
5706 return getMulExpr(NewOps);
5707 if (isa<SCEVSMaxExpr>(Comm))
5708 return getSMaxExpr(NewOps);
5709 if (isa<SCEVUMaxExpr>(Comm))
5710 return getUMaxExpr(NewOps);
5711 llvm_unreachable("Unknown commutative SCEV type!");
5714 // If we got here, all operands are loop invariant.
5718 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
5719 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
5720 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
5721 if (LHS == Div->getLHS() && RHS == Div->getRHS())
5722 return Div; // must be loop invariant
5723 return getUDivExpr(LHS, RHS);
5726 // If this is a loop recurrence for a loop that does not contain L, then we
5727 // are dealing with the final value computed by the loop.
5728 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
5729 // First, attempt to evaluate each operand.
5730 // Avoid performing the look-up in the common case where the specified
5731 // expression has no loop-variant portions.
5732 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
5733 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
5734 if (OpAtScope == AddRec->getOperand(i))
5737 // Okay, at least one of these operands is loop variant but might be
5738 // foldable. Build a new instance of the folded commutative expression.
5739 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
5740 AddRec->op_begin()+i);
5741 NewOps.push_back(OpAtScope);
5742 for (++i; i != e; ++i)
5743 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
5745 const SCEV *FoldedRec =
5746 getAddRecExpr(NewOps, AddRec->getLoop(),
5747 AddRec->getNoWrapFlags(SCEV::FlagNW));
5748 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
5749 // The addrec may be folded to a nonrecurrence, for example, if the
5750 // induction variable is multiplied by zero after constant folding. Go
5751 // ahead and return the folded value.
5757 // If the scope is outside the addrec's loop, evaluate it by using the
5758 // loop exit value of the addrec.
5759 if (!AddRec->getLoop()->contains(L)) {
5760 // To evaluate this recurrence, we need to know how many times the AddRec
5761 // loop iterates. Compute this now.
5762 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
5763 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
5765 // Then, evaluate the AddRec.
5766 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
5772 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
5773 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5774 if (Op == Cast->getOperand())
5775 return Cast; // must be loop invariant
5776 return getZeroExtendExpr(Op, Cast->getType());
5779 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
5780 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5781 if (Op == Cast->getOperand())
5782 return Cast; // must be loop invariant
5783 return getSignExtendExpr(Op, Cast->getType());
5786 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
5787 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5788 if (Op == Cast->getOperand())
5789 return Cast; // must be loop invariant
5790 return getTruncateExpr(Op, Cast->getType());
5793 llvm_unreachable("Unknown SCEV type!");
5796 /// getSCEVAtScope - This is a convenience function which does
5797 /// getSCEVAtScope(getSCEV(V), L).
5798 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
5799 return getSCEVAtScope(getSCEV(V), L);
5802 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
5803 /// following equation:
5805 /// A * X = B (mod N)
5807 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
5808 /// A and B isn't important.
5810 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
5811 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
5812 ScalarEvolution &SE) {
5813 uint32_t BW = A.getBitWidth();
5814 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
5815 assert(A != 0 && "A must be non-zero.");
5819 // The gcd of A and N may have only one prime factor: 2. The number of
5820 // trailing zeros in A is its multiplicity
5821 uint32_t Mult2 = A.countTrailingZeros();
5824 // 2. Check if B is divisible by D.
5826 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
5827 // is not less than multiplicity of this prime factor for D.
5828 if (B.countTrailingZeros() < Mult2)
5829 return SE.getCouldNotCompute();
5831 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
5834 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
5835 // bit width during computations.
5836 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
5837 APInt Mod(BW + 1, 0);
5838 Mod.setBit(BW - Mult2); // Mod = N / D
5839 APInt I = AD.multiplicativeInverse(Mod);
5841 // 4. Compute the minimum unsigned root of the equation:
5842 // I * (B / D) mod (N / D)
5843 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
5845 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
5847 return SE.getConstant(Result.trunc(BW));
5850 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
5851 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
5852 /// might be the same) or two SCEVCouldNotCompute objects.
5854 static std::pair<const SCEV *,const SCEV *>
5855 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
5856 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
5857 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
5858 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
5859 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
5861 // We currently can only solve this if the coefficients are constants.
5862 if (!LC || !MC || !NC) {
5863 const SCEV *CNC = SE.getCouldNotCompute();
5864 return std::make_pair(CNC, CNC);
5867 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
5868 const APInt &L = LC->getValue()->getValue();
5869 const APInt &M = MC->getValue()->getValue();
5870 const APInt &N = NC->getValue()->getValue();
5871 APInt Two(BitWidth, 2);
5872 APInt Four(BitWidth, 4);
5875 using namespace APIntOps;
5877 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
5878 // The B coefficient is M-N/2
5882 // The A coefficient is N/2
5883 APInt A(N.sdiv(Two));
5885 // Compute the B^2-4ac term.
5888 SqrtTerm -= Four * (A * C);
5890 if (SqrtTerm.isNegative()) {
5891 // The loop is provably infinite.
5892 const SCEV *CNC = SE.getCouldNotCompute();
5893 return std::make_pair(CNC, CNC);
5896 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
5897 // integer value or else APInt::sqrt() will assert.
5898 APInt SqrtVal(SqrtTerm.sqrt());
5900 // Compute the two solutions for the quadratic formula.
5901 // The divisions must be performed as signed divisions.
5904 if (TwoA.isMinValue()) {
5905 const SCEV *CNC = SE.getCouldNotCompute();
5906 return std::make_pair(CNC, CNC);
5909 LLVMContext &Context = SE.getContext();
5911 ConstantInt *Solution1 =
5912 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
5913 ConstantInt *Solution2 =
5914 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
5916 return std::make_pair(SE.getConstant(Solution1),
5917 SE.getConstant(Solution2));
5918 } // end APIntOps namespace
5921 /// HowFarToZero - Return the number of times a backedge comparing the specified
5922 /// value to zero will execute. If not computable, return CouldNotCompute.
5924 /// This is only used for loops with a "x != y" exit test. The exit condition is
5925 /// now expressed as a single expression, V = x-y. So the exit test is
5926 /// effectively V != 0. We know and take advantage of the fact that this
5927 /// expression only being used in a comparison by zero context.
5928 ScalarEvolution::ExitLimit
5929 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool ControlsExit) {
5930 // If the value is a constant
5931 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
5932 // If the value is already zero, the branch will execute zero times.
5933 if (C->getValue()->isZero()) return C;
5934 return getCouldNotCompute(); // Otherwise it will loop infinitely.
5937 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
5938 if (!AddRec || AddRec->getLoop() != L)
5939 return getCouldNotCompute();
5941 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
5942 // the quadratic equation to solve it.
5943 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
5944 std::pair<const SCEV *,const SCEV *> Roots =
5945 SolveQuadraticEquation(AddRec, *this);
5946 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5947 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5950 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
5951 << " sol#2: " << *R2 << "\n";
5953 // Pick the smallest positive root value.
5954 if (ConstantInt *CB =
5955 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
5958 if (CB->getZExtValue() == false)
5959 std::swap(R1, R2); // R1 is the minimum root now.
5961 // We can only use this value if the chrec ends up with an exact zero
5962 // value at this index. When solving for "X*X != 5", for example, we
5963 // should not accept a root of 2.
5964 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
5966 return R1; // We found a quadratic root!
5969 return getCouldNotCompute();
5972 // Otherwise we can only handle this if it is affine.
5973 if (!AddRec->isAffine())
5974 return getCouldNotCompute();
5976 // If this is an affine expression, the execution count of this branch is
5977 // the minimum unsigned root of the following equation:
5979 // Start + Step*N = 0 (mod 2^BW)
5983 // Step*N = -Start (mod 2^BW)
5985 // where BW is the common bit width of Start and Step.
5987 // Get the initial value for the loop.
5988 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
5989 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
5991 // For now we handle only constant steps.
5993 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
5994 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
5995 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
5996 // We have not yet seen any such cases.
5997 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
5998 if (!StepC || StepC->getValue()->equalsInt(0))
5999 return getCouldNotCompute();
6001 // For positive steps (counting up until unsigned overflow):
6002 // N = -Start/Step (as unsigned)
6003 // For negative steps (counting down to zero):
6005 // First compute the unsigned distance from zero in the direction of Step.
6006 bool CountDown = StepC->getValue()->getValue().isNegative();
6007 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
6009 // Handle unitary steps, which cannot wraparound.
6010 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
6011 // N = Distance (as unsigned)
6012 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
6013 ConstantRange CR = getUnsignedRange(Start);
6014 const SCEV *MaxBECount;
6015 if (!CountDown && CR.getUnsignedMin().isMinValue())
6016 // When counting up, the worst starting value is 1, not 0.
6017 MaxBECount = CR.getUnsignedMax().isMinValue()
6018 ? getConstant(APInt::getMinValue(CR.getBitWidth()))
6019 : getConstant(APInt::getMaxValue(CR.getBitWidth()));
6021 MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
6022 : -CR.getUnsignedMin());
6023 return ExitLimit(Distance, MaxBECount);
6026 // If the step exactly divides the distance then unsigned divide computes the
6029 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6030 SCEVDivision::divide(SE, Distance, Step, &Q, &R);
6033 getUDivExactExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6034 return ExitLimit(Exact, Exact);
6037 // If the condition controls loop exit (the loop exits only if the expression
6038 // is true) and the addition is no-wrap we can use unsigned divide to
6039 // compute the backedge count. In this case, the step may not divide the
6040 // distance, but we don't care because if the condition is "missed" the loop
6041 // will have undefined behavior due to wrapping.
6042 if (ControlsExit && AddRec->getNoWrapFlags(SCEV::FlagNW)) {
6044 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6045 return ExitLimit(Exact, Exact);
6048 // Then, try to solve the above equation provided that Start is constant.
6049 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
6050 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
6051 -StartC->getValue()->getValue(),
6053 return getCouldNotCompute();
6056 /// HowFarToNonZero - Return the number of times a backedge checking the
6057 /// specified value for nonzero will execute. If not computable, return
6059 ScalarEvolution::ExitLimit
6060 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
6061 // Loops that look like: while (X == 0) are very strange indeed. We don't
6062 // handle them yet except for the trivial case. This could be expanded in the
6063 // future as needed.
6065 // If the value is a constant, check to see if it is known to be non-zero
6066 // already. If so, the backedge will execute zero times.
6067 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6068 if (!C->getValue()->isNullValue())
6069 return getConstant(C->getType(), 0);
6070 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6073 // We could implement others, but I really doubt anyone writes loops like
6074 // this, and if they did, they would already be constant folded.
6075 return getCouldNotCompute();
6078 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
6079 /// (which may not be an immediate predecessor) which has exactly one
6080 /// successor from which BB is reachable, or null if no such block is
6083 std::pair<BasicBlock *, BasicBlock *>
6084 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
6085 // If the block has a unique predecessor, then there is no path from the
6086 // predecessor to the block that does not go through the direct edge
6087 // from the predecessor to the block.
6088 if (BasicBlock *Pred = BB->getSinglePredecessor())
6089 return std::make_pair(Pred, BB);
6091 // A loop's header is defined to be a block that dominates the loop.
6092 // If the header has a unique predecessor outside the loop, it must be
6093 // a block that has exactly one successor that can reach the loop.
6094 if (Loop *L = LI->getLoopFor(BB))
6095 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
6097 return std::pair<BasicBlock *, BasicBlock *>();
6100 /// HasSameValue - SCEV structural equivalence is usually sufficient for
6101 /// testing whether two expressions are equal, however for the purposes of
6102 /// looking for a condition guarding a loop, it can be useful to be a little
6103 /// more general, since a front-end may have replicated the controlling
6106 static bool HasSameValue(const SCEV *A, const SCEV *B) {
6107 // Quick check to see if they are the same SCEV.
6108 if (A == B) return true;
6110 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
6111 // two different instructions with the same value. Check for this case.
6112 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
6113 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
6114 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
6115 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
6116 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
6119 // Otherwise assume they may have a different value.
6123 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
6124 /// predicate Pred. Return true iff any changes were made.
6126 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
6127 const SCEV *&LHS, const SCEV *&RHS,
6129 bool Changed = false;
6131 // If we hit the max recursion limit bail out.
6135 // Canonicalize a constant to the right side.
6136 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
6137 // Check for both operands constant.
6138 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
6139 if (ConstantExpr::getICmp(Pred,
6141 RHSC->getValue())->isNullValue())
6142 goto trivially_false;
6144 goto trivially_true;
6146 // Otherwise swap the operands to put the constant on the right.
6147 std::swap(LHS, RHS);
6148 Pred = ICmpInst::getSwappedPredicate(Pred);
6152 // If we're comparing an addrec with a value which is loop-invariant in the
6153 // addrec's loop, put the addrec on the left. Also make a dominance check,
6154 // as both operands could be addrecs loop-invariant in each other's loop.
6155 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
6156 const Loop *L = AR->getLoop();
6157 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
6158 std::swap(LHS, RHS);
6159 Pred = ICmpInst::getSwappedPredicate(Pred);
6164 // If there's a constant operand, canonicalize comparisons with boundary
6165 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
6166 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
6167 const APInt &RA = RC->getValue()->getValue();
6169 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6170 case ICmpInst::ICMP_EQ:
6171 case ICmpInst::ICMP_NE:
6172 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
6174 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
6175 if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
6176 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
6177 ME->getOperand(0)->isAllOnesValue()) {
6178 RHS = AE->getOperand(1);
6179 LHS = ME->getOperand(1);
6183 case ICmpInst::ICMP_UGE:
6184 if ((RA - 1).isMinValue()) {
6185 Pred = ICmpInst::ICMP_NE;
6186 RHS = getConstant(RA - 1);
6190 if (RA.isMaxValue()) {
6191 Pred = ICmpInst::ICMP_EQ;
6195 if (RA.isMinValue()) goto trivially_true;
6197 Pred = ICmpInst::ICMP_UGT;
6198 RHS = getConstant(RA - 1);
6201 case ICmpInst::ICMP_ULE:
6202 if ((RA + 1).isMaxValue()) {
6203 Pred = ICmpInst::ICMP_NE;
6204 RHS = getConstant(RA + 1);
6208 if (RA.isMinValue()) {
6209 Pred = ICmpInst::ICMP_EQ;
6213 if (RA.isMaxValue()) goto trivially_true;
6215 Pred = ICmpInst::ICMP_ULT;
6216 RHS = getConstant(RA + 1);
6219 case ICmpInst::ICMP_SGE:
6220 if ((RA - 1).isMinSignedValue()) {
6221 Pred = ICmpInst::ICMP_NE;
6222 RHS = getConstant(RA - 1);
6226 if (RA.isMaxSignedValue()) {
6227 Pred = ICmpInst::ICMP_EQ;
6231 if (RA.isMinSignedValue()) goto trivially_true;
6233 Pred = ICmpInst::ICMP_SGT;
6234 RHS = getConstant(RA - 1);
6237 case ICmpInst::ICMP_SLE:
6238 if ((RA + 1).isMaxSignedValue()) {
6239 Pred = ICmpInst::ICMP_NE;
6240 RHS = getConstant(RA + 1);
6244 if (RA.isMinSignedValue()) {
6245 Pred = ICmpInst::ICMP_EQ;
6249 if (RA.isMaxSignedValue()) goto trivially_true;
6251 Pred = ICmpInst::ICMP_SLT;
6252 RHS = getConstant(RA + 1);
6255 case ICmpInst::ICMP_UGT:
6256 if (RA.isMinValue()) {
6257 Pred = ICmpInst::ICMP_NE;
6261 if ((RA + 1).isMaxValue()) {
6262 Pred = ICmpInst::ICMP_EQ;
6263 RHS = getConstant(RA + 1);
6267 if (RA.isMaxValue()) goto trivially_false;
6269 case ICmpInst::ICMP_ULT:
6270 if (RA.isMaxValue()) {
6271 Pred = ICmpInst::ICMP_NE;
6275 if ((RA - 1).isMinValue()) {
6276 Pred = ICmpInst::ICMP_EQ;
6277 RHS = getConstant(RA - 1);
6281 if (RA.isMinValue()) goto trivially_false;
6283 case ICmpInst::ICMP_SGT:
6284 if (RA.isMinSignedValue()) {
6285 Pred = ICmpInst::ICMP_NE;
6289 if ((RA + 1).isMaxSignedValue()) {
6290 Pred = ICmpInst::ICMP_EQ;
6291 RHS = getConstant(RA + 1);
6295 if (RA.isMaxSignedValue()) goto trivially_false;
6297 case ICmpInst::ICMP_SLT:
6298 if (RA.isMaxSignedValue()) {
6299 Pred = ICmpInst::ICMP_NE;
6303 if ((RA - 1).isMinSignedValue()) {
6304 Pred = ICmpInst::ICMP_EQ;
6305 RHS = getConstant(RA - 1);
6309 if (RA.isMinSignedValue()) goto trivially_false;
6314 // Check for obvious equality.
6315 if (HasSameValue(LHS, RHS)) {
6316 if (ICmpInst::isTrueWhenEqual(Pred))
6317 goto trivially_true;
6318 if (ICmpInst::isFalseWhenEqual(Pred))
6319 goto trivially_false;
6322 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
6323 // adding or subtracting 1 from one of the operands.
6325 case ICmpInst::ICMP_SLE:
6326 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
6327 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6329 Pred = ICmpInst::ICMP_SLT;
6331 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
6332 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6334 Pred = ICmpInst::ICMP_SLT;
6338 case ICmpInst::ICMP_SGE:
6339 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
6340 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6342 Pred = ICmpInst::ICMP_SGT;
6344 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
6345 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6347 Pred = ICmpInst::ICMP_SGT;
6351 case ICmpInst::ICMP_ULE:
6352 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
6353 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6355 Pred = ICmpInst::ICMP_ULT;
6357 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
6358 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6360 Pred = ICmpInst::ICMP_ULT;
6364 case ICmpInst::ICMP_UGE:
6365 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
6366 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6368 Pred = ICmpInst::ICMP_UGT;
6370 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
6371 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6373 Pred = ICmpInst::ICMP_UGT;
6381 // TODO: More simplifications are possible here.
6383 // Recursively simplify until we either hit a recursion limit or nothing
6386 return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1);
6392 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6393 Pred = ICmpInst::ICMP_EQ;
6398 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6399 Pred = ICmpInst::ICMP_NE;
6403 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
6404 return getSignedRange(S).getSignedMax().isNegative();
6407 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
6408 return getSignedRange(S).getSignedMin().isStrictlyPositive();
6411 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
6412 return !getSignedRange(S).getSignedMin().isNegative();
6415 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
6416 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
6419 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
6420 return isKnownNegative(S) || isKnownPositive(S);
6423 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
6424 const SCEV *LHS, const SCEV *RHS) {
6425 // Canonicalize the inputs first.
6426 (void)SimplifyICmpOperands(Pred, LHS, RHS);
6428 // If LHS or RHS is an addrec, check to see if the condition is true in
6429 // every iteration of the loop.
6430 // If LHS and RHS are both addrec, both conditions must be true in
6431 // every iteration of the loop.
6432 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
6433 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
6434 bool LeftGuarded = false;
6435 bool RightGuarded = false;
6437 const Loop *L = LAR->getLoop();
6438 if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
6439 isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
6440 if (!RAR) return true;
6445 const Loop *L = RAR->getLoop();
6446 if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
6447 isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
6448 if (!LAR) return true;
6449 RightGuarded = true;
6452 if (LeftGuarded && RightGuarded)
6455 // Otherwise see what can be done with known constant ranges.
6456 return isKnownPredicateWithRanges(Pred, LHS, RHS);
6460 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
6461 const SCEV *LHS, const SCEV *RHS) {
6462 if (HasSameValue(LHS, RHS))
6463 return ICmpInst::isTrueWhenEqual(Pred);
6465 // This code is split out from isKnownPredicate because it is called from
6466 // within isLoopEntryGuardedByCond.
6469 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6470 case ICmpInst::ICMP_SGT:
6471 std::swap(LHS, RHS);
6472 case ICmpInst::ICMP_SLT: {
6473 ConstantRange LHSRange = getSignedRange(LHS);
6474 ConstantRange RHSRange = getSignedRange(RHS);
6475 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
6477 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
6481 case ICmpInst::ICMP_SGE:
6482 std::swap(LHS, RHS);
6483 case ICmpInst::ICMP_SLE: {
6484 ConstantRange LHSRange = getSignedRange(LHS);
6485 ConstantRange RHSRange = getSignedRange(RHS);
6486 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
6488 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
6492 case ICmpInst::ICMP_UGT:
6493 std::swap(LHS, RHS);
6494 case ICmpInst::ICMP_ULT: {
6495 ConstantRange LHSRange = getUnsignedRange(LHS);
6496 ConstantRange RHSRange = getUnsignedRange(RHS);
6497 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
6499 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
6503 case ICmpInst::ICMP_UGE:
6504 std::swap(LHS, RHS);
6505 case ICmpInst::ICMP_ULE: {
6506 ConstantRange LHSRange = getUnsignedRange(LHS);
6507 ConstantRange RHSRange = getUnsignedRange(RHS);
6508 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
6510 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
6514 case ICmpInst::ICMP_NE: {
6515 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
6517 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
6520 const SCEV *Diff = getMinusSCEV(LHS, RHS);
6521 if (isKnownNonZero(Diff))
6525 case ICmpInst::ICMP_EQ:
6526 // The check at the top of the function catches the case where
6527 // the values are known to be equal.
6533 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
6534 /// protected by a conditional between LHS and RHS. This is used to
6535 /// to eliminate casts.
6537 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
6538 ICmpInst::Predicate Pred,
6539 const SCEV *LHS, const SCEV *RHS) {
6540 // Interpret a null as meaning no loop, where there is obviously no guard
6541 // (interprocedural conditions notwithstanding).
6542 if (!L) return true;
6544 BasicBlock *Latch = L->getLoopLatch();
6548 BranchInst *LoopContinuePredicate =
6549 dyn_cast<BranchInst>(Latch->getTerminator());
6550 if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
6551 isImpliedCond(Pred, LHS, RHS,
6552 LoopContinuePredicate->getCondition(),
6553 LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
6556 // Check conditions due to any @llvm.assume intrinsics.
6557 for (auto &CI : AT->assumptions(F)) {
6558 if (!DT->dominates(CI, Latch->getTerminator()))
6561 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
6568 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
6569 /// by a conditional between LHS and RHS. This is used to help avoid max
6570 /// expressions in loop trip counts, and to eliminate casts.
6572 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
6573 ICmpInst::Predicate Pred,
6574 const SCEV *LHS, const SCEV *RHS) {
6575 // Interpret a null as meaning no loop, where there is obviously no guard
6576 // (interprocedural conditions notwithstanding).
6577 if (!L) return false;
6579 // Starting at the loop predecessor, climb up the predecessor chain, as long
6580 // as there are predecessors that can be found that have unique successors
6581 // leading to the original header.
6582 for (std::pair<BasicBlock *, BasicBlock *>
6583 Pair(L->getLoopPredecessor(), L->getHeader());
6585 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
6587 BranchInst *LoopEntryPredicate =
6588 dyn_cast<BranchInst>(Pair.first->getTerminator());
6589 if (!LoopEntryPredicate ||
6590 LoopEntryPredicate->isUnconditional())
6593 if (isImpliedCond(Pred, LHS, RHS,
6594 LoopEntryPredicate->getCondition(),
6595 LoopEntryPredicate->getSuccessor(0) != Pair.second))
6599 // Check conditions due to any @llvm.assume intrinsics.
6600 for (auto &CI : AT->assumptions(F)) {
6601 if (!DT->dominates(CI, L->getHeader()))
6604 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
6611 /// RAII wrapper to prevent recursive application of isImpliedCond.
6612 /// ScalarEvolution's PendingLoopPredicates set must be empty unless we are
6613 /// currently evaluating isImpliedCond.
6614 struct MarkPendingLoopPredicate {
6616 DenseSet<Value*> &LoopPreds;
6619 MarkPendingLoopPredicate(Value *C, DenseSet<Value*> &LP)
6620 : Cond(C), LoopPreds(LP) {
6621 Pending = !LoopPreds.insert(Cond).second;
6623 ~MarkPendingLoopPredicate() {
6625 LoopPreds.erase(Cond);
6629 /// isImpliedCond - Test whether the condition described by Pred, LHS,
6630 /// and RHS is true whenever the given Cond value evaluates to true.
6631 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
6632 const SCEV *LHS, const SCEV *RHS,
6633 Value *FoundCondValue,
6635 MarkPendingLoopPredicate Mark(FoundCondValue, PendingLoopPredicates);
6639 // Recursively handle And and Or conditions.
6640 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
6641 if (BO->getOpcode() == Instruction::And) {
6643 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6644 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6645 } else if (BO->getOpcode() == Instruction::Or) {
6647 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6648 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6652 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
6653 if (!ICI) return false;
6655 // Bail if the ICmp's operands' types are wider than the needed type
6656 // before attempting to call getSCEV on them. This avoids infinite
6657 // recursion, since the analysis of widening casts can require loop
6658 // exit condition information for overflow checking, which would
6660 if (getTypeSizeInBits(LHS->getType()) <
6661 getTypeSizeInBits(ICI->getOperand(0)->getType()))
6664 // Now that we found a conditional branch that dominates the loop or controls
6665 // the loop latch. Check to see if it is the comparison we are looking for.
6666 ICmpInst::Predicate FoundPred;
6668 FoundPred = ICI->getInversePredicate();
6670 FoundPred = ICI->getPredicate();
6672 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
6673 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
6675 // Balance the types. The case where FoundLHS' type is wider than
6676 // LHS' type is checked for above.
6677 if (getTypeSizeInBits(LHS->getType()) >
6678 getTypeSizeInBits(FoundLHS->getType())) {
6679 if (CmpInst::isSigned(FoundPred)) {
6680 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
6681 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
6683 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
6684 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
6688 // Canonicalize the query to match the way instcombine will have
6689 // canonicalized the comparison.
6690 if (SimplifyICmpOperands(Pred, LHS, RHS))
6692 return CmpInst::isTrueWhenEqual(Pred);
6693 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
6694 if (FoundLHS == FoundRHS)
6695 return CmpInst::isFalseWhenEqual(FoundPred);
6697 // Check to see if we can make the LHS or RHS match.
6698 if (LHS == FoundRHS || RHS == FoundLHS) {
6699 if (isa<SCEVConstant>(RHS)) {
6700 std::swap(FoundLHS, FoundRHS);
6701 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
6703 std::swap(LHS, RHS);
6704 Pred = ICmpInst::getSwappedPredicate(Pred);
6708 // Check whether the found predicate is the same as the desired predicate.
6709 if (FoundPred == Pred)
6710 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
6712 // Check whether swapping the found predicate makes it the same as the
6713 // desired predicate.
6714 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
6715 if (isa<SCEVConstant>(RHS))
6716 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
6718 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
6719 RHS, LHS, FoundLHS, FoundRHS);
6722 // Check whether the actual condition is beyond sufficient.
6723 if (FoundPred == ICmpInst::ICMP_EQ)
6724 if (ICmpInst::isTrueWhenEqual(Pred))
6725 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
6727 if (Pred == ICmpInst::ICMP_NE)
6728 if (!ICmpInst::isTrueWhenEqual(FoundPred))
6729 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
6732 // Otherwise assume the worst.
6736 /// isImpliedCondOperands - Test whether the condition described by Pred,
6737 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
6738 /// and FoundRHS is true.
6739 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
6740 const SCEV *LHS, const SCEV *RHS,
6741 const SCEV *FoundLHS,
6742 const SCEV *FoundRHS) {
6743 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
6744 FoundLHS, FoundRHS) ||
6745 // ~x < ~y --> x > y
6746 isImpliedCondOperandsHelper(Pred, LHS, RHS,
6747 getNotSCEV(FoundRHS),
6748 getNotSCEV(FoundLHS));
6751 /// isImpliedCondOperandsHelper - Test whether the condition described by
6752 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
6753 /// FoundLHS, and FoundRHS is true.
6755 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
6756 const SCEV *LHS, const SCEV *RHS,
6757 const SCEV *FoundLHS,
6758 const SCEV *FoundRHS) {
6760 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6761 case ICmpInst::ICMP_EQ:
6762 case ICmpInst::ICMP_NE:
6763 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
6766 case ICmpInst::ICMP_SLT:
6767 case ICmpInst::ICMP_SLE:
6768 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
6769 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
6772 case ICmpInst::ICMP_SGT:
6773 case ICmpInst::ICMP_SGE:
6774 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
6775 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
6778 case ICmpInst::ICMP_ULT:
6779 case ICmpInst::ICMP_ULE:
6780 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
6781 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
6784 case ICmpInst::ICMP_UGT:
6785 case ICmpInst::ICMP_UGE:
6786 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
6787 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
6795 // Verify if an linear IV with positive stride can overflow when in a
6796 // less-than comparison, knowing the invariant term of the comparison, the
6797 // stride and the knowledge of NSW/NUW flags on the recurrence.
6798 bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
6799 bool IsSigned, bool NoWrap) {
6800 if (NoWrap) return false;
6802 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6803 const SCEV *One = getConstant(Stride->getType(), 1);
6806 APInt MaxRHS = getSignedRange(RHS).getSignedMax();
6807 APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
6808 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
6811 // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
6812 return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
6815 APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
6816 APInt MaxValue = APInt::getMaxValue(BitWidth);
6817 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
6820 // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
6821 return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
6824 // Verify if an linear IV with negative stride can overflow when in a
6825 // greater-than comparison, knowing the invariant term of the comparison,
6826 // the stride and the knowledge of NSW/NUW flags on the recurrence.
6827 bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
6828 bool IsSigned, bool NoWrap) {
6829 if (NoWrap) return false;
6831 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6832 const SCEV *One = getConstant(Stride->getType(), 1);
6835 APInt MinRHS = getSignedRange(RHS).getSignedMin();
6836 APInt MinValue = APInt::getSignedMinValue(BitWidth);
6837 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
6840 // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
6841 return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
6844 APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
6845 APInt MinValue = APInt::getMinValue(BitWidth);
6846 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
6849 // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
6850 return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
6853 // Compute the backedge taken count knowing the interval difference, the
6854 // stride and presence of the equality in the comparison.
6855 const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
6857 const SCEV *One = getConstant(Step->getType(), 1);
6858 Delta = Equality ? getAddExpr(Delta, Step)
6859 : getAddExpr(Delta, getMinusSCEV(Step, One));
6860 return getUDivExpr(Delta, Step);
6863 /// HowManyLessThans - Return the number of times a backedge containing the
6864 /// specified less-than comparison will execute. If not computable, return
6865 /// CouldNotCompute.
6867 /// @param ControlsExit is true when the LHS < RHS condition directly controls
6868 /// the branch (loops exits only if condition is true). In this case, we can use
6869 /// NoWrapFlags to skip overflow checks.
6870 ScalarEvolution::ExitLimit
6871 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
6872 const Loop *L, bool IsSigned,
6873 bool ControlsExit) {
6874 // We handle only IV < Invariant
6875 if (!isLoopInvariant(RHS, L))
6876 return getCouldNotCompute();
6878 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
6880 // Avoid weird loops
6881 if (!IV || IV->getLoop() != L || !IV->isAffine())
6882 return getCouldNotCompute();
6884 bool NoWrap = ControlsExit &&
6885 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
6887 const SCEV *Stride = IV->getStepRecurrence(*this);
6889 // Avoid negative or zero stride values
6890 if (!isKnownPositive(Stride))
6891 return getCouldNotCompute();
6893 // Avoid proven overflow cases: this will ensure that the backedge taken count
6894 // will not generate any unsigned overflow. Relaxed no-overflow conditions
6895 // exploit NoWrapFlags, allowing to optimize in presence of undefined
6896 // behaviors like the case of C language.
6897 if (!Stride->isOne() && doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
6898 return getCouldNotCompute();
6900 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
6901 : ICmpInst::ICMP_ULT;
6902 const SCEV *Start = IV->getStart();
6903 const SCEV *End = RHS;
6904 if (!isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS))
6905 End = IsSigned ? getSMaxExpr(RHS, Start)
6906 : getUMaxExpr(RHS, Start);
6908 const SCEV *BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
6910 APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
6911 : getUnsignedRange(Start).getUnsignedMin();
6913 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
6914 : getUnsignedRange(Stride).getUnsignedMin();
6916 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
6917 APInt Limit = IsSigned ? APInt::getSignedMaxValue(BitWidth) - (MinStride - 1)
6918 : APInt::getMaxValue(BitWidth) - (MinStride - 1);
6920 // Although End can be a MAX expression we estimate MaxEnd considering only
6921 // the case End = RHS. This is safe because in the other case (End - Start)
6922 // is zero, leading to a zero maximum backedge taken count.
6924 IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
6925 : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
6927 const SCEV *MaxBECount;
6928 if (isa<SCEVConstant>(BECount))
6929 MaxBECount = BECount;
6931 MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
6932 getConstant(MinStride), false);
6934 if (isa<SCEVCouldNotCompute>(MaxBECount))
6935 MaxBECount = BECount;
6937 return ExitLimit(BECount, MaxBECount);
6940 ScalarEvolution::ExitLimit
6941 ScalarEvolution::HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
6942 const Loop *L, bool IsSigned,
6943 bool ControlsExit) {
6944 // We handle only IV > Invariant
6945 if (!isLoopInvariant(RHS, L))
6946 return getCouldNotCompute();
6948 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
6950 // Avoid weird loops
6951 if (!IV || IV->getLoop() != L || !IV->isAffine())
6952 return getCouldNotCompute();
6954 bool NoWrap = ControlsExit &&
6955 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
6957 const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
6959 // Avoid negative or zero stride values
6960 if (!isKnownPositive(Stride))
6961 return getCouldNotCompute();
6963 // Avoid proven overflow cases: this will ensure that the backedge taken count
6964 // will not generate any unsigned overflow. Relaxed no-overflow conditions
6965 // exploit NoWrapFlags, allowing to optimize in presence of undefined
6966 // behaviors like the case of C language.
6967 if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
6968 return getCouldNotCompute();
6970 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
6971 : ICmpInst::ICMP_UGT;
6973 const SCEV *Start = IV->getStart();
6974 const SCEV *End = RHS;
6975 if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS))
6976 End = IsSigned ? getSMinExpr(RHS, Start)
6977 : getUMinExpr(RHS, Start);
6979 const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
6981 APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
6982 : getUnsignedRange(Start).getUnsignedMax();
6984 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
6985 : getUnsignedRange(Stride).getUnsignedMin();
6987 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
6988 APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
6989 : APInt::getMinValue(BitWidth) + (MinStride - 1);
6991 // Although End can be a MIN expression we estimate MinEnd considering only
6992 // the case End = RHS. This is safe because in the other case (Start - End)
6993 // is zero, leading to a zero maximum backedge taken count.
6995 IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
6996 : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
6999 const SCEV *MaxBECount = getCouldNotCompute();
7000 if (isa<SCEVConstant>(BECount))
7001 MaxBECount = BECount;
7003 MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
7004 getConstant(MinStride), false);
7006 if (isa<SCEVCouldNotCompute>(MaxBECount))
7007 MaxBECount = BECount;
7009 return ExitLimit(BECount, MaxBECount);
7012 /// getNumIterationsInRange - Return the number of iterations of this loop that
7013 /// produce values in the specified constant range. Another way of looking at
7014 /// this is that it returns the first iteration number where the value is not in
7015 /// the condition, thus computing the exit count. If the iteration count can't
7016 /// be computed, an instance of SCEVCouldNotCompute is returned.
7017 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
7018 ScalarEvolution &SE) const {
7019 if (Range.isFullSet()) // Infinite loop.
7020 return SE.getCouldNotCompute();
7022 // If the start is a non-zero constant, shift the range to simplify things.
7023 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
7024 if (!SC->getValue()->isZero()) {
7025 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
7026 Operands[0] = SE.getConstant(SC->getType(), 0);
7027 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
7028 getNoWrapFlags(FlagNW));
7029 if (const SCEVAddRecExpr *ShiftedAddRec =
7030 dyn_cast<SCEVAddRecExpr>(Shifted))
7031 return ShiftedAddRec->getNumIterationsInRange(
7032 Range.subtract(SC->getValue()->getValue()), SE);
7033 // This is strange and shouldn't happen.
7034 return SE.getCouldNotCompute();
7037 // The only time we can solve this is when we have all constant indices.
7038 // Otherwise, we cannot determine the overflow conditions.
7039 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
7040 if (!isa<SCEVConstant>(getOperand(i)))
7041 return SE.getCouldNotCompute();
7044 // Okay at this point we know that all elements of the chrec are constants and
7045 // that the start element is zero.
7047 // First check to see if the range contains zero. If not, the first
7049 unsigned BitWidth = SE.getTypeSizeInBits(getType());
7050 if (!Range.contains(APInt(BitWidth, 0)))
7051 return SE.getConstant(getType(), 0);
7054 // If this is an affine expression then we have this situation:
7055 // Solve {0,+,A} in Range === Ax in Range
7057 // We know that zero is in the range. If A is positive then we know that
7058 // the upper value of the range must be the first possible exit value.
7059 // If A is negative then the lower of the range is the last possible loop
7060 // value. Also note that we already checked for a full range.
7061 APInt One(BitWidth,1);
7062 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
7063 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
7065 // The exit value should be (End+A)/A.
7066 APInt ExitVal = (End + A).udiv(A);
7067 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
7069 // Evaluate at the exit value. If we really did fall out of the valid
7070 // range, then we computed our trip count, otherwise wrap around or other
7071 // things must have happened.
7072 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
7073 if (Range.contains(Val->getValue()))
7074 return SE.getCouldNotCompute(); // Something strange happened
7076 // Ensure that the previous value is in the range. This is a sanity check.
7077 assert(Range.contains(
7078 EvaluateConstantChrecAtConstant(this,
7079 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
7080 "Linear scev computation is off in a bad way!");
7081 return SE.getConstant(ExitValue);
7082 } else if (isQuadratic()) {
7083 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
7084 // quadratic equation to solve it. To do this, we must frame our problem in
7085 // terms of figuring out when zero is crossed, instead of when
7086 // Range.getUpper() is crossed.
7087 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
7088 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
7089 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
7090 // getNoWrapFlags(FlagNW)
7093 // Next, solve the constructed addrec
7094 std::pair<const SCEV *,const SCEV *> Roots =
7095 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
7096 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
7097 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
7099 // Pick the smallest positive root value.
7100 if (ConstantInt *CB =
7101 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
7102 R1->getValue(), R2->getValue()))) {
7103 if (CB->getZExtValue() == false)
7104 std::swap(R1, R2); // R1 is the minimum root now.
7106 // Make sure the root is not off by one. The returned iteration should
7107 // not be in the range, but the previous one should be. When solving
7108 // for "X*X < 5", for example, we should not return a root of 2.
7109 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
7112 if (Range.contains(R1Val->getValue())) {
7113 // The next iteration must be out of the range...
7114 ConstantInt *NextVal =
7115 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
7117 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
7118 if (!Range.contains(R1Val->getValue()))
7119 return SE.getConstant(NextVal);
7120 return SE.getCouldNotCompute(); // Something strange happened
7123 // If R1 was not in the range, then it is a good return value. Make
7124 // sure that R1-1 WAS in the range though, just in case.
7125 ConstantInt *NextVal =
7126 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
7127 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
7128 if (Range.contains(R1Val->getValue()))
7130 return SE.getCouldNotCompute(); // Something strange happened
7135 return SE.getCouldNotCompute();
7141 FindUndefs() : Found(false) {}
7143 bool follow(const SCEV *S) {
7144 if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
7145 if (isa<UndefValue>(C->getValue()))
7147 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
7148 if (isa<UndefValue>(C->getValue()))
7152 // Keep looking if we haven't found it yet.
7155 bool isDone() const {
7156 // Stop recursion if we have found an undef.
7162 // Return true when S contains at least an undef value.
7164 containsUndefs(const SCEV *S) {
7166 SCEVTraversal<FindUndefs> ST(F);
7173 // Collect all steps of SCEV expressions.
7174 struct SCEVCollectStrides {
7175 ScalarEvolution &SE;
7176 SmallVectorImpl<const SCEV *> &Strides;
7178 SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
7179 : SE(SE), Strides(S) {}
7181 bool follow(const SCEV *S) {
7182 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
7183 Strides.push_back(AR->getStepRecurrence(SE));
7186 bool isDone() const { return false; }
7189 // Collect all SCEVUnknown and SCEVMulExpr expressions.
7190 struct SCEVCollectTerms {
7191 SmallVectorImpl<const SCEV *> &Terms;
7193 SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
7196 bool follow(const SCEV *S) {
7197 if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S)) {
7198 if (!containsUndefs(S))
7201 // Stop recursion: once we collected a term, do not walk its operands.
7208 bool isDone() const { return false; }
7212 /// Find parametric terms in this SCEVAddRecExpr.
7213 void SCEVAddRecExpr::collectParametricTerms(
7214 ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Terms) const {
7215 SmallVector<const SCEV *, 4> Strides;
7216 SCEVCollectStrides StrideCollector(SE, Strides);
7217 visitAll(this, StrideCollector);
7220 dbgs() << "Strides:\n";
7221 for (const SCEV *S : Strides)
7222 dbgs() << *S << "\n";
7225 for (const SCEV *S : Strides) {
7226 SCEVCollectTerms TermCollector(Terms);
7227 visitAll(S, TermCollector);
7231 dbgs() << "Terms:\n";
7232 for (const SCEV *T : Terms)
7233 dbgs() << *T << "\n";
7237 static bool findArrayDimensionsRec(ScalarEvolution &SE,
7238 SmallVectorImpl<const SCEV *> &Terms,
7239 SmallVectorImpl<const SCEV *> &Sizes) {
7240 int Last = Terms.size() - 1;
7241 const SCEV *Step = Terms[Last];
7243 // End of recursion.
7245 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
7246 SmallVector<const SCEV *, 2> Qs;
7247 for (const SCEV *Op : M->operands())
7248 if (!isa<SCEVConstant>(Op))
7251 Step = SE.getMulExpr(Qs);
7254 Sizes.push_back(Step);
7258 for (const SCEV *&Term : Terms) {
7259 // Normalize the terms before the next call to findArrayDimensionsRec.
7261 SCEVDivision::divide(SE, Term, Step, &Q, &R);
7263 // Bail out when GCD does not evenly divide one of the terms.
7270 // Remove all SCEVConstants.
7271 Terms.erase(std::remove_if(Terms.begin(), Terms.end(), [](const SCEV *E) {
7272 return isa<SCEVConstant>(E);
7276 if (Terms.size() > 0)
7277 if (!findArrayDimensionsRec(SE, Terms, Sizes))
7280 Sizes.push_back(Step);
7285 struct FindParameter {
7286 bool FoundParameter;
7287 FindParameter() : FoundParameter(false) {}
7289 bool follow(const SCEV *S) {
7290 if (isa<SCEVUnknown>(S)) {
7291 FoundParameter = true;
7292 // Stop recursion: we found a parameter.
7298 bool isDone() const {
7299 // Stop recursion if we have found a parameter.
7300 return FoundParameter;
7305 // Returns true when S contains at least a SCEVUnknown parameter.
7307 containsParameters(const SCEV *S) {
7309 SCEVTraversal<FindParameter> ST(F);
7312 return F.FoundParameter;
7315 // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
7317 containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
7318 for (const SCEV *T : Terms)
7319 if (containsParameters(T))
7324 // Return the number of product terms in S.
7325 static inline int numberOfTerms(const SCEV *S) {
7326 if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
7327 return Expr->getNumOperands();
7331 static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
7332 if (isa<SCEVConstant>(T))
7335 if (isa<SCEVUnknown>(T))
7338 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
7339 SmallVector<const SCEV *, 2> Factors;
7340 for (const SCEV *Op : M->operands())
7341 if (!isa<SCEVConstant>(Op))
7342 Factors.push_back(Op);
7344 return SE.getMulExpr(Factors);
7350 /// Return the size of an element read or written by Inst.
7351 const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
7353 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
7354 Ty = Store->getValueOperand()->getType();
7355 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
7356 Ty = Load->getType();
7360 Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
7361 return getSizeOfExpr(ETy, Ty);
7364 /// Second step of delinearization: compute the array dimensions Sizes from the
7365 /// set of Terms extracted from the memory access function of this SCEVAddRec.
7366 void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
7367 SmallVectorImpl<const SCEV *> &Sizes,
7368 const SCEV *ElementSize) const {
7370 if (Terms.size() < 1 || !ElementSize)
7373 // Early return when Terms do not contain parameters: we do not delinearize
7374 // non parametric SCEVs.
7375 if (!containsParameters(Terms))
7379 dbgs() << "Terms:\n";
7380 for (const SCEV *T : Terms)
7381 dbgs() << *T << "\n";
7384 // Remove duplicates.
7385 std::sort(Terms.begin(), Terms.end());
7386 Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
7388 // Put larger terms first.
7389 std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
7390 return numberOfTerms(LHS) > numberOfTerms(RHS);
7393 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
7395 // Divide all terms by the element size.
7396 for (const SCEV *&Term : Terms) {
7398 SCEVDivision::divide(SE, Term, ElementSize, &Q, &R);
7402 SmallVector<const SCEV *, 4> NewTerms;
7404 // Remove constant factors.
7405 for (const SCEV *T : Terms)
7406 if (const SCEV *NewT = removeConstantFactors(SE, T))
7407 NewTerms.push_back(NewT);
7410 dbgs() << "Terms after sorting:\n";
7411 for (const SCEV *T : NewTerms)
7412 dbgs() << *T << "\n";
7415 if (NewTerms.empty() ||
7416 !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
7421 // The last element to be pushed into Sizes is the size of an element.
7422 Sizes.push_back(ElementSize);
7425 dbgs() << "Sizes:\n";
7426 for (const SCEV *S : Sizes)
7427 dbgs() << *S << "\n";
7431 /// Third step of delinearization: compute the access functions for the
7432 /// Subscripts based on the dimensions in Sizes.
7433 void SCEVAddRecExpr::computeAccessFunctions(
7434 ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Subscripts,
7435 SmallVectorImpl<const SCEV *> &Sizes) const {
7437 // Early exit in case this SCEV is not an affine multivariate function.
7438 if (Sizes.empty() || !this->isAffine())
7441 const SCEV *Res = this;
7442 int Last = Sizes.size() - 1;
7443 for (int i = Last; i >= 0; i--) {
7445 SCEVDivision::divide(SE, Res, Sizes[i], &Q, &R);
7448 dbgs() << "Res: " << *Res << "\n";
7449 dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
7450 dbgs() << "Res divided by Sizes[i]:\n";
7451 dbgs() << "Quotient: " << *Q << "\n";
7452 dbgs() << "Remainder: " << *R << "\n";
7457 // Do not record the last subscript corresponding to the size of elements in
7461 // Bail out if the remainder is too complex.
7462 if (isa<SCEVAddRecExpr>(R)) {
7471 // Record the access function for the current subscript.
7472 Subscripts.push_back(R);
7475 // Also push in last position the remainder of the last division: it will be
7476 // the access function of the innermost dimension.
7477 Subscripts.push_back(Res);
7479 std::reverse(Subscripts.begin(), Subscripts.end());
7482 dbgs() << "Subscripts:\n";
7483 for (const SCEV *S : Subscripts)
7484 dbgs() << *S << "\n";
7488 /// Splits the SCEV into two vectors of SCEVs representing the subscripts and
7489 /// sizes of an array access. Returns the remainder of the delinearization that
7490 /// is the offset start of the array. The SCEV->delinearize algorithm computes
7491 /// the multiples of SCEV coefficients: that is a pattern matching of sub
7492 /// expressions in the stride and base of a SCEV corresponding to the
7493 /// computation of a GCD (greatest common divisor) of base and stride. When
7494 /// SCEV->delinearize fails, it returns the SCEV unchanged.
7496 /// For example: when analyzing the memory access A[i][j][k] in this loop nest
7498 /// void foo(long n, long m, long o, double A[n][m][o]) {
7500 /// for (long i = 0; i < n; i++)
7501 /// for (long j = 0; j < m; j++)
7502 /// for (long k = 0; k < o; k++)
7503 /// A[i][j][k] = 1.0;
7506 /// the delinearization input is the following AddRec SCEV:
7508 /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
7510 /// From this SCEV, we are able to say that the base offset of the access is %A
7511 /// because it appears as an offset that does not divide any of the strides in
7514 /// CHECK: Base offset: %A
7516 /// and then SCEV->delinearize determines the size of some of the dimensions of
7517 /// the array as these are the multiples by which the strides are happening:
7519 /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
7521 /// Note that the outermost dimension remains of UnknownSize because there are
7522 /// no strides that would help identifying the size of the last dimension: when
7523 /// the array has been statically allocated, one could compute the size of that
7524 /// dimension by dividing the overall size of the array by the size of the known
7525 /// dimensions: %m * %o * 8.
7527 /// Finally delinearize provides the access functions for the array reference
7528 /// that does correspond to A[i][j][k] of the above C testcase:
7530 /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
7532 /// The testcases are checking the output of a function pass:
7533 /// DelinearizationPass that walks through all loads and stores of a function
7534 /// asking for the SCEV of the memory access with respect to all enclosing
7535 /// loops, calling SCEV->delinearize on that and printing the results.
7537 void SCEVAddRecExpr::delinearize(ScalarEvolution &SE,
7538 SmallVectorImpl<const SCEV *> &Subscripts,
7539 SmallVectorImpl<const SCEV *> &Sizes,
7540 const SCEV *ElementSize) const {
7541 // First step: collect parametric terms.
7542 SmallVector<const SCEV *, 4> Terms;
7543 collectParametricTerms(SE, Terms);
7548 // Second step: find subscript sizes.
7549 SE.findArrayDimensions(Terms, Sizes, ElementSize);
7554 // Third step: compute the access functions for each subscript.
7555 computeAccessFunctions(SE, Subscripts, Sizes);
7557 if (Subscripts.empty())
7561 dbgs() << "succeeded to delinearize " << *this << "\n";
7562 dbgs() << "ArrayDecl[UnknownSize]";
7563 for (const SCEV *S : Sizes)
7564 dbgs() << "[" << *S << "]";
7566 dbgs() << "\nArrayRef";
7567 for (const SCEV *S : Subscripts)
7568 dbgs() << "[" << *S << "]";
7573 //===----------------------------------------------------------------------===//
7574 // SCEVCallbackVH Class Implementation
7575 //===----------------------------------------------------------------------===//
7577 void ScalarEvolution::SCEVCallbackVH::deleted() {
7578 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
7579 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
7580 SE->ConstantEvolutionLoopExitValue.erase(PN);
7581 SE->ValueExprMap.erase(getValPtr());
7582 // this now dangles!
7585 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
7586 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
7588 // Forget all the expressions associated with users of the old value,
7589 // so that future queries will recompute the expressions using the new
7591 Value *Old = getValPtr();
7592 SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
7593 SmallPtrSet<User *, 8> Visited;
7594 while (!Worklist.empty()) {
7595 User *U = Worklist.pop_back_val();
7596 // Deleting the Old value will cause this to dangle. Postpone
7597 // that until everything else is done.
7600 if (!Visited.insert(U))
7602 if (PHINode *PN = dyn_cast<PHINode>(U))
7603 SE->ConstantEvolutionLoopExitValue.erase(PN);
7604 SE->ValueExprMap.erase(U);
7605 Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
7607 // Delete the Old value.
7608 if (PHINode *PN = dyn_cast<PHINode>(Old))
7609 SE->ConstantEvolutionLoopExitValue.erase(PN);
7610 SE->ValueExprMap.erase(Old);
7611 // this now dangles!
7614 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
7615 : CallbackVH(V), SE(se) {}
7617 //===----------------------------------------------------------------------===//
7618 // ScalarEvolution Class Implementation
7619 //===----------------------------------------------------------------------===//
7621 ScalarEvolution::ScalarEvolution()
7622 : FunctionPass(ID), ValuesAtScopes(64), LoopDispositions(64),
7623 BlockDispositions(64), FirstUnknown(nullptr) {
7624 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
7627 bool ScalarEvolution::runOnFunction(Function &F) {
7629 AT = &getAnalysis<AssumptionTracker>();
7630 LI = &getAnalysis<LoopInfo>();
7631 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
7632 DL = DLP ? &DLP->getDataLayout() : nullptr;
7633 TLI = &getAnalysis<TargetLibraryInfo>();
7634 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
7638 void ScalarEvolution::releaseMemory() {
7639 // Iterate through all the SCEVUnknown instances and call their
7640 // destructors, so that they release their references to their values.
7641 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
7643 FirstUnknown = nullptr;
7645 ValueExprMap.clear();
7647 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
7648 // that a loop had multiple computable exits.
7649 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
7650 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end();
7655 assert(PendingLoopPredicates.empty() && "isImpliedCond garbage");
7657 BackedgeTakenCounts.clear();
7658 ConstantEvolutionLoopExitValue.clear();
7659 ValuesAtScopes.clear();
7660 LoopDispositions.clear();
7661 BlockDispositions.clear();
7662 UnsignedRanges.clear();
7663 SignedRanges.clear();
7664 UniqueSCEVs.clear();
7665 SCEVAllocator.Reset();
7668 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
7669 AU.setPreservesAll();
7670 AU.addRequired<AssumptionTracker>();
7671 AU.addRequiredTransitive<LoopInfo>();
7672 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
7673 AU.addRequired<TargetLibraryInfo>();
7676 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
7677 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
7680 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
7682 // Print all inner loops first
7683 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
7684 PrintLoopInfo(OS, SE, *I);
7687 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
7690 SmallVector<BasicBlock *, 8> ExitBlocks;
7691 L->getExitBlocks(ExitBlocks);
7692 if (ExitBlocks.size() != 1)
7693 OS << "<multiple exits> ";
7695 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
7696 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
7698 OS << "Unpredictable backedge-taken count. ";
7703 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
7706 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
7707 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
7709 OS << "Unpredictable max backedge-taken count. ";
7715 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
7716 // ScalarEvolution's implementation of the print method is to print
7717 // out SCEV values of all instructions that are interesting. Doing
7718 // this potentially causes it to create new SCEV objects though,
7719 // which technically conflicts with the const qualifier. This isn't
7720 // observable from outside the class though, so casting away the
7721 // const isn't dangerous.
7722 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
7724 OS << "Classifying expressions for: ";
7725 F->printAsOperand(OS, /*PrintType=*/false);
7727 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
7728 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
7731 const SCEV *SV = SE.getSCEV(&*I);
7734 const Loop *L = LI->getLoopFor((*I).getParent());
7736 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
7743 OS << "\t\t" "Exits: ";
7744 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
7745 if (!SE.isLoopInvariant(ExitValue, L)) {
7746 OS << "<<Unknown>>";
7755 OS << "Determining loop execution counts for: ";
7756 F->printAsOperand(OS, /*PrintType=*/false);
7758 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
7759 PrintLoopInfo(OS, &SE, *I);
7762 ScalarEvolution::LoopDisposition
7763 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
7764 SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values = LoopDispositions[S];
7765 for (unsigned u = 0; u < Values.size(); u++) {
7766 if (Values[u].first == L)
7767 return Values[u].second;
7769 Values.push_back(std::make_pair(L, LoopVariant));
7770 LoopDisposition D = computeLoopDisposition(S, L);
7771 SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values2 = LoopDispositions[S];
7772 for (unsigned u = Values2.size(); u > 0; u--) {
7773 if (Values2[u - 1].first == L) {
7774 Values2[u - 1].second = D;
7781 ScalarEvolution::LoopDisposition
7782 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
7783 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
7785 return LoopInvariant;
7789 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
7790 case scAddRecExpr: {
7791 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
7793 // If L is the addrec's loop, it's computable.
7794 if (AR->getLoop() == L)
7795 return LoopComputable;
7797 // Add recurrences are never invariant in the function-body (null loop).
7801 // This recurrence is variant w.r.t. L if L contains AR's loop.
7802 if (L->contains(AR->getLoop()))
7805 // This recurrence is invariant w.r.t. L if AR's loop contains L.
7806 if (AR->getLoop()->contains(L))
7807 return LoopInvariant;
7809 // This recurrence is variant w.r.t. L if any of its operands
7811 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
7813 if (!isLoopInvariant(*I, L))
7816 // Otherwise it's loop-invariant.
7817 return LoopInvariant;
7823 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
7824 bool HasVarying = false;
7825 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
7827 LoopDisposition D = getLoopDisposition(*I, L);
7828 if (D == LoopVariant)
7830 if (D == LoopComputable)
7833 return HasVarying ? LoopComputable : LoopInvariant;
7836 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
7837 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
7838 if (LD == LoopVariant)
7840 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
7841 if (RD == LoopVariant)
7843 return (LD == LoopInvariant && RD == LoopInvariant) ?
7844 LoopInvariant : LoopComputable;
7847 // All non-instruction values are loop invariant. All instructions are loop
7848 // invariant if they are not contained in the specified loop.
7849 // Instructions are never considered invariant in the function body
7850 // (null loop) because they are defined within the "loop".
7851 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
7852 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
7853 return LoopInvariant;
7854 case scCouldNotCompute:
7855 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
7857 llvm_unreachable("Unknown SCEV kind!");
7860 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
7861 return getLoopDisposition(S, L) == LoopInvariant;
7864 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
7865 return getLoopDisposition(S, L) == LoopComputable;
7868 ScalarEvolution::BlockDisposition
7869 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
7870 SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values = BlockDispositions[S];
7871 for (unsigned u = 0; u < Values.size(); u++) {
7872 if (Values[u].first == BB)
7873 return Values[u].second;
7875 Values.push_back(std::make_pair(BB, DoesNotDominateBlock));
7876 BlockDisposition D = computeBlockDisposition(S, BB);
7877 SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values2 = BlockDispositions[S];
7878 for (unsigned u = Values2.size(); u > 0; u--) {
7879 if (Values2[u - 1].first == BB) {
7880 Values2[u - 1].second = D;
7887 ScalarEvolution::BlockDisposition
7888 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
7889 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
7891 return ProperlyDominatesBlock;
7895 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
7896 case scAddRecExpr: {
7897 // This uses a "dominates" query instead of "properly dominates" query
7898 // to test for proper dominance too, because the instruction which
7899 // produces the addrec's value is a PHI, and a PHI effectively properly
7900 // dominates its entire containing block.
7901 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
7902 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
7903 return DoesNotDominateBlock;
7905 // FALL THROUGH into SCEVNAryExpr handling.
7910 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
7912 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
7914 BlockDisposition D = getBlockDisposition(*I, BB);
7915 if (D == DoesNotDominateBlock)
7916 return DoesNotDominateBlock;
7917 if (D == DominatesBlock)
7920 return Proper ? ProperlyDominatesBlock : DominatesBlock;
7923 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
7924 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
7925 BlockDisposition LD = getBlockDisposition(LHS, BB);
7926 if (LD == DoesNotDominateBlock)
7927 return DoesNotDominateBlock;
7928 BlockDisposition RD = getBlockDisposition(RHS, BB);
7929 if (RD == DoesNotDominateBlock)
7930 return DoesNotDominateBlock;
7931 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
7932 ProperlyDominatesBlock : DominatesBlock;
7935 if (Instruction *I =
7936 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
7937 if (I->getParent() == BB)
7938 return DominatesBlock;
7939 if (DT->properlyDominates(I->getParent(), BB))
7940 return ProperlyDominatesBlock;
7941 return DoesNotDominateBlock;
7943 return ProperlyDominatesBlock;
7944 case scCouldNotCompute:
7945 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
7947 llvm_unreachable("Unknown SCEV kind!");
7950 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
7951 return getBlockDisposition(S, BB) >= DominatesBlock;
7954 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
7955 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
7959 // Search for a SCEV expression node within an expression tree.
7960 // Implements SCEVTraversal::Visitor.
7965 SCEVSearch(const SCEV *N): Node(N), IsFound(false) {}
7967 bool follow(const SCEV *S) {
7968 IsFound |= (S == Node);
7971 bool isDone() const { return IsFound; }
7975 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
7976 SCEVSearch Search(Op);
7977 visitAll(S, Search);
7978 return Search.IsFound;
7981 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
7982 ValuesAtScopes.erase(S);
7983 LoopDispositions.erase(S);
7984 BlockDispositions.erase(S);
7985 UnsignedRanges.erase(S);
7986 SignedRanges.erase(S);
7988 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
7989 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end(); I != E; ) {
7990 BackedgeTakenInfo &BEInfo = I->second;
7991 if (BEInfo.hasOperand(S, this)) {
7993 BackedgeTakenCounts.erase(I++);
8000 typedef DenseMap<const Loop *, std::string> VerifyMap;
8002 /// replaceSubString - Replaces all occurrences of From in Str with To.
8003 static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
8005 while ((Pos = Str.find(From, Pos)) != std::string::npos) {
8006 Str.replace(Pos, From.size(), To.data(), To.size());
8011 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
8013 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
8014 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) {
8015 getLoopBackedgeTakenCounts(*I, Map, SE); // recurse.
8017 std::string &S = Map[L];
8019 raw_string_ostream OS(S);
8020 SE.getBackedgeTakenCount(L)->print(OS);
8022 // false and 0 are semantically equivalent. This can happen in dead loops.
8023 replaceSubString(OS.str(), "false", "0");
8024 // Remove wrap flags, their use in SCEV is highly fragile.
8025 // FIXME: Remove this when SCEV gets smarter about them.
8026 replaceSubString(OS.str(), "<nw>", "");
8027 replaceSubString(OS.str(), "<nsw>", "");
8028 replaceSubString(OS.str(), "<nuw>", "");
8033 void ScalarEvolution::verifyAnalysis() const {
8037 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
8039 // Gather stringified backedge taken counts for all loops using SCEV's caches.
8040 // FIXME: It would be much better to store actual values instead of strings,
8041 // but SCEV pointers will change if we drop the caches.
8042 VerifyMap BackedgeDumpsOld, BackedgeDumpsNew;
8043 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
8044 getLoopBackedgeTakenCounts(*I, BackedgeDumpsOld, SE);
8046 // Gather stringified backedge taken counts for all loops without using
8049 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
8050 getLoopBackedgeTakenCounts(*I, BackedgeDumpsNew, SE);
8052 // Now compare whether they're the same with and without caches. This allows
8053 // verifying that no pass changed the cache.
8054 assert(BackedgeDumpsOld.size() == BackedgeDumpsNew.size() &&
8055 "New loops suddenly appeared!");
8057 for (VerifyMap::iterator OldI = BackedgeDumpsOld.begin(),
8058 OldE = BackedgeDumpsOld.end(),
8059 NewI = BackedgeDumpsNew.begin();
8060 OldI != OldE; ++OldI, ++NewI) {
8061 assert(OldI->first == NewI->first && "Loop order changed!");
8063 // Compare the stringified SCEVs. We don't care if undef backedgetaken count
8065 // FIXME: We currently ignore SCEV changes from/to CouldNotCompute. This
8066 // means that a pass is buggy or SCEV has to learn a new pattern but is
8067 // usually not harmful.
8068 if (OldI->second != NewI->second &&
8069 OldI->second.find("undef") == std::string::npos &&
8070 NewI->second.find("undef") == std::string::npos &&
8071 OldI->second != "***COULDNOTCOMPUTE***" &&
8072 NewI->second != "***COULDNOTCOMPUTE***") {
8073 dbgs() << "SCEVValidator: SCEV for loop '"
8074 << OldI->first->getHeader()->getName()
8075 << "' changed from '" << OldI->second
8076 << "' to '" << NewI->second << "'!\n";
8081 // TODO: Verify more things.