1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis ----------*- C++ -*-===//
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 #define DEBUG_TYPE "scalar-evolution"
62 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
63 #include "llvm/Constants.h"
64 #include "llvm/DerivedTypes.h"
65 #include "llvm/GlobalVariable.h"
66 #include "llvm/GlobalAlias.h"
67 #include "llvm/Instructions.h"
68 #include "llvm/LLVMContext.h"
69 #include "llvm/Operator.h"
70 #include "llvm/Analysis/ConstantFolding.h"
71 #include "llvm/Analysis/Dominators.h"
72 #include "llvm/Analysis/InstructionSimplify.h"
73 #include "llvm/Analysis/LoopInfo.h"
74 #include "llvm/Analysis/ValueTracking.h"
75 #include "llvm/Assembly/Writer.h"
76 #include "llvm/Target/TargetData.h"
77 #include "llvm/Support/CommandLine.h"
78 #include "llvm/Support/ConstantRange.h"
79 #include "llvm/Support/Debug.h"
80 #include "llvm/Support/ErrorHandling.h"
81 #include "llvm/Support/GetElementPtrTypeIterator.h"
82 #include "llvm/Support/InstIterator.h"
83 #include "llvm/Support/MathExtras.h"
84 #include "llvm/Support/raw_ostream.h"
85 #include "llvm/ADT/Statistic.h"
86 #include "llvm/ADT/STLExtras.h"
87 #include "llvm/ADT/SmallPtrSet.h"
91 STATISTIC(NumArrayLenItCounts,
92 "Number of trip counts computed with array length");
93 STATISTIC(NumTripCountsComputed,
94 "Number of loops with predictable loop counts");
95 STATISTIC(NumTripCountsNotComputed,
96 "Number of loops without predictable loop counts");
97 STATISTIC(NumBruteForceTripCountsComputed,
98 "Number of loops with trip counts computed by force");
100 static cl::opt<unsigned>
101 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
102 cl::desc("Maximum number of iterations SCEV will "
103 "symbolically execute a constant "
107 INITIALIZE_PASS_BEGIN(ScalarEvolution, "scalar-evolution",
108 "Scalar Evolution Analysis", false, true)
109 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
110 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
111 INITIALIZE_PASS_END(ScalarEvolution, "scalar-evolution",
112 "Scalar Evolution Analysis", false, true)
113 char ScalarEvolution::ID = 0;
115 //===----------------------------------------------------------------------===//
116 // SCEV class definitions
117 //===----------------------------------------------------------------------===//
119 //===----------------------------------------------------------------------===//
120 // Implementation of the SCEV class.
123 void SCEV::dump() const {
128 void SCEV::print(raw_ostream &OS) const {
129 switch (getSCEVType()) {
131 WriteAsOperand(OS, cast<SCEVConstant>(this)->getValue(), false);
134 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
135 const SCEV *Op = Trunc->getOperand();
136 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
137 << *Trunc->getType() << ")";
141 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
142 const SCEV *Op = ZExt->getOperand();
143 OS << "(zext " << *Op->getType() << " " << *Op << " to "
144 << *ZExt->getType() << ")";
148 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
149 const SCEV *Op = SExt->getOperand();
150 OS << "(sext " << *Op->getType() << " " << *Op << " to "
151 << *SExt->getType() << ")";
155 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
156 OS << "{" << *AR->getOperand(0);
157 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
158 OS << ",+," << *AR->getOperand(i);
160 if (AR->hasNoUnsignedWrap())
162 if (AR->hasNoSignedWrap())
164 WriteAsOperand(OS, AR->getLoop()->getHeader(), /*PrintType=*/false);
172 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
173 const char *OpStr = 0;
174 switch (NAry->getSCEVType()) {
175 case scAddExpr: OpStr = " + "; break;
176 case scMulExpr: OpStr = " * "; break;
177 case scUMaxExpr: OpStr = " umax "; break;
178 case scSMaxExpr: OpStr = " smax "; break;
181 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
184 if (llvm::next(I) != E)
191 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
192 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
196 const SCEVUnknown *U = cast<SCEVUnknown>(this);
198 if (U->isSizeOf(AllocTy)) {
199 OS << "sizeof(" << *AllocTy << ")";
202 if (U->isAlignOf(AllocTy)) {
203 OS << "alignof(" << *AllocTy << ")";
209 if (U->isOffsetOf(CTy, FieldNo)) {
210 OS << "offsetof(" << *CTy << ", ";
211 WriteAsOperand(OS, FieldNo, false);
216 // Otherwise just print it normally.
217 WriteAsOperand(OS, U->getValue(), false);
220 case scCouldNotCompute:
221 OS << "***COULDNOTCOMPUTE***";
225 llvm_unreachable("Unknown SCEV kind!");
228 const Type *SCEV::getType() const {
229 switch (getSCEVType()) {
231 return cast<SCEVConstant>(this)->getType();
235 return cast<SCEVCastExpr>(this)->getType();
240 return cast<SCEVNAryExpr>(this)->getType();
242 return cast<SCEVAddExpr>(this)->getType();
244 return cast<SCEVUDivExpr>(this)->getType();
246 return cast<SCEVUnknown>(this)->getType();
247 case scCouldNotCompute:
248 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
252 llvm_unreachable("Unknown SCEV kind!");
256 bool SCEV::isZero() const {
257 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
258 return SC->getValue()->isZero();
262 bool SCEV::isOne() const {
263 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
264 return SC->getValue()->isOne();
268 bool SCEV::isAllOnesValue() const {
269 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
270 return SC->getValue()->isAllOnesValue();
274 SCEVCouldNotCompute::SCEVCouldNotCompute() :
275 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
277 bool SCEVCouldNotCompute::classof(const SCEV *S) {
278 return S->getSCEVType() == scCouldNotCompute;
281 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
283 ID.AddInteger(scConstant);
286 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
287 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
288 UniqueSCEVs.InsertNode(S, IP);
292 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
293 return getConstant(ConstantInt::get(getContext(), Val));
297 ScalarEvolution::getConstant(const Type *Ty, uint64_t V, bool isSigned) {
298 const IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
299 return getConstant(ConstantInt::get(ITy, V, isSigned));
302 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
303 unsigned SCEVTy, const SCEV *op, const Type *ty)
304 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
306 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
307 const SCEV *op, const Type *ty)
308 : SCEVCastExpr(ID, scTruncate, op, ty) {
309 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
310 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
311 "Cannot truncate non-integer value!");
314 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
315 const SCEV *op, const Type *ty)
316 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
317 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
318 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
319 "Cannot zero extend non-integer value!");
322 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
323 const SCEV *op, const Type *ty)
324 : SCEVCastExpr(ID, scSignExtend, op, ty) {
325 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
326 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
327 "Cannot sign extend non-integer value!");
330 void SCEVUnknown::deleted() {
331 // Clear this SCEVUnknown from various maps.
332 SE->forgetMemoizedResults(this);
334 // Remove this SCEVUnknown from the uniquing map.
335 SE->UniqueSCEVs.RemoveNode(this);
337 // Release the value.
341 void SCEVUnknown::allUsesReplacedWith(Value *New) {
342 // Clear this SCEVUnknown from various maps.
343 SE->forgetMemoizedResults(this);
345 // Remove this SCEVUnknown from the uniquing map.
346 SE->UniqueSCEVs.RemoveNode(this);
348 // Update this SCEVUnknown to point to the new value. This is needed
349 // because there may still be outstanding SCEVs which still point to
354 bool SCEVUnknown::isSizeOf(const Type *&AllocTy) const {
355 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
356 if (VCE->getOpcode() == Instruction::PtrToInt)
357 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
358 if (CE->getOpcode() == Instruction::GetElementPtr &&
359 CE->getOperand(0)->isNullValue() &&
360 CE->getNumOperands() == 2)
361 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
363 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
371 bool SCEVUnknown::isAlignOf(const Type *&AllocTy) const {
372 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
373 if (VCE->getOpcode() == Instruction::PtrToInt)
374 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
375 if (CE->getOpcode() == Instruction::GetElementPtr &&
376 CE->getOperand(0)->isNullValue()) {
378 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
379 if (const StructType *STy = dyn_cast<StructType>(Ty))
380 if (!STy->isPacked() &&
381 CE->getNumOperands() == 3 &&
382 CE->getOperand(1)->isNullValue()) {
383 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
385 STy->getNumElements() == 2 &&
386 STy->getElementType(0)->isIntegerTy(1)) {
387 AllocTy = STy->getElementType(1);
396 bool SCEVUnknown::isOffsetOf(const Type *&CTy, Constant *&FieldNo) const {
397 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
398 if (VCE->getOpcode() == Instruction::PtrToInt)
399 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
400 if (CE->getOpcode() == Instruction::GetElementPtr &&
401 CE->getNumOperands() == 3 &&
402 CE->getOperand(0)->isNullValue() &&
403 CE->getOperand(1)->isNullValue()) {
405 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
406 // Ignore vector types here so that ScalarEvolutionExpander doesn't
407 // emit getelementptrs that index into vectors.
408 if (Ty->isStructTy() || Ty->isArrayTy()) {
410 FieldNo = CE->getOperand(2);
418 //===----------------------------------------------------------------------===//
420 //===----------------------------------------------------------------------===//
423 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
424 /// than the complexity of the RHS. This comparator is used to canonicalize
426 class SCEVComplexityCompare {
427 const LoopInfo *const LI;
429 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
431 // Return true or false if LHS is less than, or at least RHS, respectively.
432 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
433 return compare(LHS, RHS) < 0;
436 // Return negative, zero, or positive, if LHS is less than, equal to, or
437 // greater than RHS, respectively. A three-way result allows recursive
438 // comparisons to be more efficient.
439 int compare(const SCEV *LHS, const SCEV *RHS) const {
440 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
444 // Primarily, sort the SCEVs by their getSCEVType().
445 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
447 return (int)LType - (int)RType;
449 // Aside from the getSCEVType() ordering, the particular ordering
450 // isn't very important except that it's beneficial to be consistent,
451 // so that (a + b) and (b + a) don't end up as different expressions.
454 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
455 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
457 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
458 // not as complete as it could be.
459 const Value *LV = LU->getValue(), *RV = RU->getValue();
461 // Order pointer values after integer values. This helps SCEVExpander
463 bool LIsPointer = LV->getType()->isPointerTy(),
464 RIsPointer = RV->getType()->isPointerTy();
465 if (LIsPointer != RIsPointer)
466 return (int)LIsPointer - (int)RIsPointer;
468 // Compare getValueID values.
469 unsigned LID = LV->getValueID(),
470 RID = RV->getValueID();
472 return (int)LID - (int)RID;
474 // Sort arguments by their position.
475 if (const Argument *LA = dyn_cast<Argument>(LV)) {
476 const Argument *RA = cast<Argument>(RV);
477 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
478 return (int)LArgNo - (int)RArgNo;
481 // For instructions, compare their loop depth, and their operand
482 // count. This is pretty loose.
483 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
484 const Instruction *RInst = cast<Instruction>(RV);
486 // Compare loop depths.
487 const BasicBlock *LParent = LInst->getParent(),
488 *RParent = RInst->getParent();
489 if (LParent != RParent) {
490 unsigned LDepth = LI->getLoopDepth(LParent),
491 RDepth = LI->getLoopDepth(RParent);
492 if (LDepth != RDepth)
493 return (int)LDepth - (int)RDepth;
496 // Compare the number of operands.
497 unsigned LNumOps = LInst->getNumOperands(),
498 RNumOps = RInst->getNumOperands();
499 return (int)LNumOps - (int)RNumOps;
506 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
507 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
509 // Compare constant values.
510 const APInt &LA = LC->getValue()->getValue();
511 const APInt &RA = RC->getValue()->getValue();
512 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
513 if (LBitWidth != RBitWidth)
514 return (int)LBitWidth - (int)RBitWidth;
515 return LA.ult(RA) ? -1 : 1;
519 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
520 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
522 // Compare addrec loop depths.
523 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
524 if (LLoop != RLoop) {
525 unsigned LDepth = LLoop->getLoopDepth(),
526 RDepth = RLoop->getLoopDepth();
527 if (LDepth != RDepth)
528 return (int)LDepth - (int)RDepth;
531 // Addrec complexity grows with operand count.
532 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
533 if (LNumOps != RNumOps)
534 return (int)LNumOps - (int)RNumOps;
536 // Lexicographically compare.
537 for (unsigned i = 0; i != LNumOps; ++i) {
538 long X = compare(LA->getOperand(i), RA->getOperand(i));
550 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
551 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
553 // Lexicographically compare n-ary expressions.
554 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
555 for (unsigned i = 0; i != LNumOps; ++i) {
558 long X = compare(LC->getOperand(i), RC->getOperand(i));
562 return (int)LNumOps - (int)RNumOps;
566 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
567 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
569 // Lexicographically compare udiv expressions.
570 long X = compare(LC->getLHS(), RC->getLHS());
573 return compare(LC->getRHS(), RC->getRHS());
579 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
580 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
582 // Compare cast expressions by operand.
583 return compare(LC->getOperand(), RC->getOperand());
590 llvm_unreachable("Unknown SCEV kind!");
596 /// GroupByComplexity - Given a list of SCEV objects, order them by their
597 /// complexity, and group objects of the same complexity together by value.
598 /// When this routine is finished, we know that any duplicates in the vector are
599 /// consecutive and that complexity is monotonically increasing.
601 /// Note that we go take special precautions to ensure that we get deterministic
602 /// results from this routine. In other words, we don't want the results of
603 /// this to depend on where the addresses of various SCEV objects happened to
606 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
608 if (Ops.size() < 2) return; // Noop
609 if (Ops.size() == 2) {
610 // This is the common case, which also happens to be trivially simple.
612 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
613 if (SCEVComplexityCompare(LI)(RHS, LHS))
618 // Do the rough sort by complexity.
619 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
621 // Now that we are sorted by complexity, group elements of the same
622 // complexity. Note that this is, at worst, N^2, but the vector is likely to
623 // be extremely short in practice. Note that we take this approach because we
624 // do not want to depend on the addresses of the objects we are grouping.
625 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
626 const SCEV *S = Ops[i];
627 unsigned Complexity = S->getSCEVType();
629 // If there are any objects of the same complexity and same value as this
631 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
632 if (Ops[j] == S) { // Found a duplicate.
633 // Move it to immediately after i'th element.
634 std::swap(Ops[i+1], Ops[j]);
635 ++i; // no need to rescan it.
636 if (i == e-2) return; // Done!
644 //===----------------------------------------------------------------------===//
645 // Simple SCEV method implementations
646 //===----------------------------------------------------------------------===//
648 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
650 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
652 const Type* ResultTy) {
653 // Handle the simplest case efficiently.
655 return SE.getTruncateOrZeroExtend(It, ResultTy);
657 // We are using the following formula for BC(It, K):
659 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
661 // Suppose, W is the bitwidth of the return value. We must be prepared for
662 // overflow. Hence, we must assure that the result of our computation is
663 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
664 // safe in modular arithmetic.
666 // However, this code doesn't use exactly that formula; the formula it uses
667 // is something like the following, where T is the number of factors of 2 in
668 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
671 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
673 // This formula is trivially equivalent to the previous formula. However,
674 // this formula can be implemented much more efficiently. The trick is that
675 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
676 // arithmetic. To do exact division in modular arithmetic, all we have
677 // to do is multiply by the inverse. Therefore, this step can be done at
680 // The next issue is how to safely do the division by 2^T. The way this
681 // is done is by doing the multiplication step at a width of at least W + T
682 // bits. This way, the bottom W+T bits of the product are accurate. Then,
683 // when we perform the division by 2^T (which is equivalent to a right shift
684 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
685 // truncated out after the division by 2^T.
687 // In comparison to just directly using the first formula, this technique
688 // is much more efficient; using the first formula requires W * K bits,
689 // but this formula less than W + K bits. Also, the first formula requires
690 // a division step, whereas this formula only requires multiplies and shifts.
692 // It doesn't matter whether the subtraction step is done in the calculation
693 // width or the input iteration count's width; if the subtraction overflows,
694 // the result must be zero anyway. We prefer here to do it in the width of
695 // the induction variable because it helps a lot for certain cases; CodeGen
696 // isn't smart enough to ignore the overflow, which leads to much less
697 // efficient code if the width of the subtraction is wider than the native
700 // (It's possible to not widen at all by pulling out factors of 2 before
701 // the multiplication; for example, K=2 can be calculated as
702 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
703 // extra arithmetic, so it's not an obvious win, and it gets
704 // much more complicated for K > 3.)
706 // Protection from insane SCEVs; this bound is conservative,
707 // but it probably doesn't matter.
709 return SE.getCouldNotCompute();
711 unsigned W = SE.getTypeSizeInBits(ResultTy);
713 // Calculate K! / 2^T and T; we divide out the factors of two before
714 // multiplying for calculating K! / 2^T to avoid overflow.
715 // Other overflow doesn't matter because we only care about the bottom
716 // W bits of the result.
717 APInt OddFactorial(W, 1);
719 for (unsigned i = 3; i <= K; ++i) {
721 unsigned TwoFactors = Mult.countTrailingZeros();
723 Mult = Mult.lshr(TwoFactors);
724 OddFactorial *= Mult;
727 // We need at least W + T bits for the multiplication step
728 unsigned CalculationBits = W + T;
730 // Calculate 2^T, at width T+W.
731 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
733 // Calculate the multiplicative inverse of K! / 2^T;
734 // this multiplication factor will perform the exact division by
736 APInt Mod = APInt::getSignedMinValue(W+1);
737 APInt MultiplyFactor = OddFactorial.zext(W+1);
738 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
739 MultiplyFactor = MultiplyFactor.trunc(W);
741 // Calculate the product, at width T+W
742 const IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
744 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
745 for (unsigned i = 1; i != K; ++i) {
746 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
747 Dividend = SE.getMulExpr(Dividend,
748 SE.getTruncateOrZeroExtend(S, CalculationTy));
752 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
754 // Truncate the result, and divide by K! / 2^T.
756 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
757 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
760 /// evaluateAtIteration - Return the value of this chain of recurrences at
761 /// the specified iteration number. We can evaluate this recurrence by
762 /// multiplying each element in the chain by the binomial coefficient
763 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
765 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
767 /// where BC(It, k) stands for binomial coefficient.
769 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
770 ScalarEvolution &SE) const {
771 const SCEV *Result = getStart();
772 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
773 // The computation is correct in the face of overflow provided that the
774 // multiplication is performed _after_ the evaluation of the binomial
776 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
777 if (isa<SCEVCouldNotCompute>(Coeff))
780 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
785 //===----------------------------------------------------------------------===//
786 // SCEV Expression folder implementations
787 //===----------------------------------------------------------------------===//
789 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
791 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
792 "This is not a truncating conversion!");
793 assert(isSCEVable(Ty) &&
794 "This is not a conversion to a SCEVable type!");
795 Ty = getEffectiveSCEVType(Ty);
798 ID.AddInteger(scTruncate);
802 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
804 // Fold if the operand is constant.
805 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
807 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
808 getEffectiveSCEVType(Ty))));
810 // trunc(trunc(x)) --> trunc(x)
811 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
812 return getTruncateExpr(ST->getOperand(), Ty);
814 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
815 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
816 return getTruncateOrSignExtend(SS->getOperand(), Ty);
818 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
819 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
820 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
822 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
823 // eliminate all the truncates.
824 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
825 SmallVector<const SCEV *, 4> Operands;
826 bool hasTrunc = false;
827 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
828 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
829 hasTrunc = isa<SCEVTruncateExpr>(S);
830 Operands.push_back(S);
833 return getAddExpr(Operands, false, false);
836 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
837 // eliminate all the truncates.
838 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
839 SmallVector<const SCEV *, 4> Operands;
840 bool hasTrunc = false;
841 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
842 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
843 hasTrunc = isa<SCEVTruncateExpr>(S);
844 Operands.push_back(S);
847 return getMulExpr(Operands, false, false);
850 // If the input value is a chrec scev, truncate the chrec's operands.
851 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
852 SmallVector<const SCEV *, 4> Operands;
853 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
854 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
855 return getAddRecExpr(Operands, AddRec->getLoop());
858 // As a special case, fold trunc(undef) to undef. We don't want to
859 // know too much about SCEVUnknowns, but this special case is handy
861 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
862 if (isa<UndefValue>(U->getValue()))
863 return getSCEV(UndefValue::get(Ty));
865 // The cast wasn't folded; create an explicit cast node. We can reuse
866 // the existing insert position since if we get here, we won't have
867 // made any changes which would invalidate it.
868 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
870 UniqueSCEVs.InsertNode(S, IP);
874 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
876 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
877 "This is not an extending conversion!");
878 assert(isSCEVable(Ty) &&
879 "This is not a conversion to a SCEVable type!");
880 Ty = getEffectiveSCEVType(Ty);
882 // Fold if the operand is constant.
883 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
885 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
886 getEffectiveSCEVType(Ty))));
888 // zext(zext(x)) --> zext(x)
889 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
890 return getZeroExtendExpr(SZ->getOperand(), Ty);
892 // Before doing any expensive analysis, check to see if we've already
893 // computed a SCEV for this Op and Ty.
895 ID.AddInteger(scZeroExtend);
899 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
901 // zext(trunc(x)) --> zext(x) or x or trunc(x)
902 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
903 // It's possible the bits taken off by the truncate were all zero bits. If
904 // so, we should be able to simplify this further.
905 const SCEV *X = ST->getOperand();
906 ConstantRange CR = getUnsignedRange(X);
907 unsigned OrigBits = CR.getBitWidth();
908 unsigned TruncBits = getTypeSizeInBits(ST->getType());
909 unsigned NewBits = getTypeSizeInBits(Ty);
910 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
911 CR.zextOrTrunc(NewBits))) {
912 if (NewBits > OrigBits) return getZeroExtendExpr(X, Ty);
913 if (NewBits < OrigBits) return getTruncateExpr(X, Ty);
918 // If the input value is a chrec scev, and we can prove that the value
919 // did not overflow the old, smaller, value, we can zero extend all of the
920 // operands (often constants). This allows analysis of something like
921 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
922 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
923 if (AR->isAffine()) {
924 const SCEV *Start = AR->getStart();
925 const SCEV *Step = AR->getStepRecurrence(*this);
926 unsigned BitWidth = getTypeSizeInBits(AR->getType());
927 const Loop *L = AR->getLoop();
929 // If we have special knowledge that this addrec won't overflow,
930 // we don't need to do any further analysis.
931 if (AR->hasNoUnsignedWrap())
932 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
933 getZeroExtendExpr(Step, Ty),
936 // Check whether the backedge-taken count is SCEVCouldNotCompute.
937 // Note that this serves two purposes: It filters out loops that are
938 // simply not analyzable, and it covers the case where this code is
939 // being called from within backedge-taken count analysis, such that
940 // attempting to ask for the backedge-taken count would likely result
941 // in infinite recursion. In the later case, the analysis code will
942 // cope with a conservative value, and it will take care to purge
943 // that value once it has finished.
944 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
945 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
946 // Manually compute the final value for AR, checking for
949 // Check whether the backedge-taken count can be losslessly casted to
950 // the addrec's type. The count is always unsigned.
951 const SCEV *CastedMaxBECount =
952 getTruncateOrZeroExtend(MaxBECount, Start->getType());
953 const SCEV *RecastedMaxBECount =
954 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
955 if (MaxBECount == RecastedMaxBECount) {
956 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
957 // Check whether Start+Step*MaxBECount has no unsigned overflow.
958 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
959 const SCEV *Add = getAddExpr(Start, ZMul);
960 const SCEV *OperandExtendedAdd =
961 getAddExpr(getZeroExtendExpr(Start, WideTy),
962 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
963 getZeroExtendExpr(Step, WideTy)));
964 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
965 // Return the expression with the addrec on the outside.
966 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
967 getZeroExtendExpr(Step, Ty),
970 // Similar to above, only this time treat the step value as signed.
971 // This covers loops that count down.
972 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
973 Add = getAddExpr(Start, SMul);
975 getAddExpr(getZeroExtendExpr(Start, WideTy),
976 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
977 getSignExtendExpr(Step, WideTy)));
978 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
979 // Return the expression with the addrec on the outside.
980 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
981 getSignExtendExpr(Step, Ty),
985 // If the backedge is guarded by a comparison with the pre-inc value
986 // the addrec is safe. Also, if the entry is guarded by a comparison
987 // with the start value and the backedge is guarded by a comparison
988 // with the post-inc value, the addrec is safe.
989 if (isKnownPositive(Step)) {
990 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
991 getUnsignedRange(Step).getUnsignedMax());
992 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
993 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
994 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
995 AR->getPostIncExpr(*this), N)))
996 // Return the expression with the addrec on the outside.
997 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
998 getZeroExtendExpr(Step, Ty),
1000 } else if (isKnownNegative(Step)) {
1001 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1002 getSignedRange(Step).getSignedMin());
1003 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1004 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1005 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1006 AR->getPostIncExpr(*this), N)))
1007 // Return the expression with the addrec on the outside.
1008 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1009 getSignExtendExpr(Step, Ty),
1015 // The cast wasn't folded; create an explicit cast node.
1016 // Recompute the insert position, as it may have been invalidated.
1017 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1018 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1020 UniqueSCEVs.InsertNode(S, IP);
1024 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1026 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1027 "This is not an extending conversion!");
1028 assert(isSCEVable(Ty) &&
1029 "This is not a conversion to a SCEVable type!");
1030 Ty = getEffectiveSCEVType(Ty);
1032 // Fold if the operand is constant.
1033 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1035 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1036 getEffectiveSCEVType(Ty))));
1038 // sext(sext(x)) --> sext(x)
1039 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1040 return getSignExtendExpr(SS->getOperand(), Ty);
1042 // sext(zext(x)) --> zext(x)
1043 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1044 return getZeroExtendExpr(SZ->getOperand(), Ty);
1046 // Before doing any expensive analysis, check to see if we've already
1047 // computed a SCEV for this Op and Ty.
1048 FoldingSetNodeID ID;
1049 ID.AddInteger(scSignExtend);
1053 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1055 // If the input value is provably positive, build a zext instead.
1056 if (isKnownNonNegative(Op))
1057 return getZeroExtendExpr(Op, Ty);
1059 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1060 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1061 // It's possible the bits taken off by the truncate were all sign bits. If
1062 // so, we should be able to simplify this further.
1063 const SCEV *X = ST->getOperand();
1064 ConstantRange CR = getSignedRange(X);
1065 unsigned OrigBits = CR.getBitWidth();
1066 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1067 unsigned NewBits = getTypeSizeInBits(Ty);
1068 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1069 CR.sextOrTrunc(NewBits))) {
1070 if (NewBits > OrigBits) return getSignExtendExpr(X, Ty);
1071 if (NewBits < OrigBits) return getTruncateExpr(X, Ty);
1076 // If the input value is a chrec scev, and we can prove that the value
1077 // did not overflow the old, smaller, value, we can sign extend all of the
1078 // operands (often constants). This allows analysis of something like
1079 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1080 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1081 if (AR->isAffine()) {
1082 const SCEV *Start = AR->getStart();
1083 const SCEV *Step = AR->getStepRecurrence(*this);
1084 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1085 const Loop *L = AR->getLoop();
1087 // If we have special knowledge that this addrec won't overflow,
1088 // we don't need to do any further analysis.
1089 if (AR->hasNoSignedWrap())
1090 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1091 getSignExtendExpr(Step, Ty),
1094 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1095 // Note that this serves two purposes: It filters out loops that are
1096 // simply not analyzable, and it covers the case where this code is
1097 // being called from within backedge-taken count analysis, such that
1098 // attempting to ask for the backedge-taken count would likely result
1099 // in infinite recursion. In the later case, the analysis code will
1100 // cope with a conservative value, and it will take care to purge
1101 // that value once it has finished.
1102 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1103 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1104 // Manually compute the final value for AR, checking for
1107 // Check whether the backedge-taken count can be losslessly casted to
1108 // the addrec's type. The count is always unsigned.
1109 const SCEV *CastedMaxBECount =
1110 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1111 const SCEV *RecastedMaxBECount =
1112 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1113 if (MaxBECount == RecastedMaxBECount) {
1114 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1115 // Check whether Start+Step*MaxBECount has no signed overflow.
1116 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1117 const SCEV *Add = getAddExpr(Start, SMul);
1118 const SCEV *OperandExtendedAdd =
1119 getAddExpr(getSignExtendExpr(Start, WideTy),
1120 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1121 getSignExtendExpr(Step, WideTy)));
1122 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1123 // Return the expression with the addrec on the outside.
1124 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1125 getSignExtendExpr(Step, Ty),
1128 // Similar to above, only this time treat the step value as unsigned.
1129 // This covers loops that count up with an unsigned step.
1130 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1131 Add = getAddExpr(Start, UMul);
1132 OperandExtendedAdd =
1133 getAddExpr(getSignExtendExpr(Start, WideTy),
1134 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1135 getZeroExtendExpr(Step, WideTy)));
1136 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1137 // Return the expression with the addrec on the outside.
1138 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1139 getZeroExtendExpr(Step, Ty),
1143 // If the backedge is guarded by a comparison with the pre-inc value
1144 // the addrec is safe. Also, if the entry is guarded by a comparison
1145 // with the start value and the backedge is guarded by a comparison
1146 // with the post-inc value, the addrec is safe.
1147 if (isKnownPositive(Step)) {
1148 const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
1149 getSignedRange(Step).getSignedMax());
1150 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
1151 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
1152 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
1153 AR->getPostIncExpr(*this), N)))
1154 // Return the expression with the addrec on the outside.
1155 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1156 getSignExtendExpr(Step, Ty),
1158 } else if (isKnownNegative(Step)) {
1159 const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
1160 getSignedRange(Step).getSignedMin());
1161 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
1162 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
1163 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
1164 AR->getPostIncExpr(*this), N)))
1165 // Return the expression with the addrec on the outside.
1166 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1167 getSignExtendExpr(Step, Ty),
1173 // The cast wasn't folded; create an explicit cast node.
1174 // Recompute the insert position, as it may have been invalidated.
1175 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1176 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1178 UniqueSCEVs.InsertNode(S, IP);
1182 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1183 /// unspecified bits out to the given type.
1185 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1187 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1188 "This is not an extending conversion!");
1189 assert(isSCEVable(Ty) &&
1190 "This is not a conversion to a SCEVable type!");
1191 Ty = getEffectiveSCEVType(Ty);
1193 // Sign-extend negative constants.
1194 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1195 if (SC->getValue()->getValue().isNegative())
1196 return getSignExtendExpr(Op, Ty);
1198 // Peel off a truncate cast.
1199 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1200 const SCEV *NewOp = T->getOperand();
1201 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1202 return getAnyExtendExpr(NewOp, Ty);
1203 return getTruncateOrNoop(NewOp, Ty);
1206 // Next try a zext cast. If the cast is folded, use it.
1207 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1208 if (!isa<SCEVZeroExtendExpr>(ZExt))
1211 // Next try a sext cast. If the cast is folded, use it.
1212 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1213 if (!isa<SCEVSignExtendExpr>(SExt))
1216 // Force the cast to be folded into the operands of an addrec.
1217 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1218 SmallVector<const SCEV *, 4> Ops;
1219 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1221 Ops.push_back(getAnyExtendExpr(*I, Ty));
1222 return getAddRecExpr(Ops, AR->getLoop());
1225 // As a special case, fold anyext(undef) to undef. We don't want to
1226 // know too much about SCEVUnknowns, but this special case is handy
1228 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
1229 if (isa<UndefValue>(U->getValue()))
1230 return getSCEV(UndefValue::get(Ty));
1232 // If the expression is obviously signed, use the sext cast value.
1233 if (isa<SCEVSMaxExpr>(Op))
1236 // Absent any other information, use the zext cast value.
1240 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1241 /// a list of operands to be added under the given scale, update the given
1242 /// map. This is a helper function for getAddRecExpr. As an example of
1243 /// what it does, given a sequence of operands that would form an add
1244 /// expression like this:
1246 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1248 /// where A and B are constants, update the map with these values:
1250 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1252 /// and add 13 + A*B*29 to AccumulatedConstant.
1253 /// This will allow getAddRecExpr to produce this:
1255 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1257 /// This form often exposes folding opportunities that are hidden in
1258 /// the original operand list.
1260 /// Return true iff it appears that any interesting folding opportunities
1261 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1262 /// the common case where no interesting opportunities are present, and
1263 /// is also used as a check to avoid infinite recursion.
1266 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1267 SmallVector<const SCEV *, 8> &NewOps,
1268 APInt &AccumulatedConstant,
1269 const SCEV *const *Ops, size_t NumOperands,
1271 ScalarEvolution &SE) {
1272 bool Interesting = false;
1274 // Iterate over the add operands. They are sorted, with constants first.
1276 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1278 // Pull a buried constant out to the outside.
1279 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1281 AccumulatedConstant += Scale * C->getValue()->getValue();
1284 // Next comes everything else. We're especially interested in multiplies
1285 // here, but they're in the middle, so just visit the rest with one loop.
1286 for (; i != NumOperands; ++i) {
1287 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1288 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1290 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1291 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1292 // A multiplication of a constant with another add; recurse.
1293 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1295 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1296 Add->op_begin(), Add->getNumOperands(),
1299 // A multiplication of a constant with some other value. Update
1301 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1302 const SCEV *Key = SE.getMulExpr(MulOps);
1303 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1304 M.insert(std::make_pair(Key, NewScale));
1306 NewOps.push_back(Pair.first->first);
1308 Pair.first->second += NewScale;
1309 // The map already had an entry for this value, which may indicate
1310 // a folding opportunity.
1315 // An ordinary operand. Update the map.
1316 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1317 M.insert(std::make_pair(Ops[i], Scale));
1319 NewOps.push_back(Pair.first->first);
1321 Pair.first->second += Scale;
1322 // The map already had an entry for this value, which may indicate
1323 // a folding opportunity.
1333 struct APIntCompare {
1334 bool operator()(const APInt &LHS, const APInt &RHS) const {
1335 return LHS.ult(RHS);
1340 /// getAddExpr - Get a canonical add expression, or something simpler if
1342 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1343 bool HasNUW, bool HasNSW) {
1344 assert(!Ops.empty() && "Cannot get empty add!");
1345 if (Ops.size() == 1) return Ops[0];
1347 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1348 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1349 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1350 "SCEVAddExpr operand types don't match!");
1353 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1354 if (!HasNUW && HasNSW) {
1356 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1357 E = Ops.end(); I != E; ++I)
1358 if (!isKnownNonNegative(*I)) {
1362 if (All) HasNUW = true;
1365 // Sort by complexity, this groups all similar expression types together.
1366 GroupByComplexity(Ops, LI);
1368 // If there are any constants, fold them together.
1370 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1372 assert(Idx < Ops.size());
1373 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1374 // We found two constants, fold them together!
1375 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1376 RHSC->getValue()->getValue());
1377 if (Ops.size() == 2) return Ops[0];
1378 Ops.erase(Ops.begin()+1); // Erase the folded element
1379 LHSC = cast<SCEVConstant>(Ops[0]);
1382 // If we are left with a constant zero being added, strip it off.
1383 if (LHSC->getValue()->isZero()) {
1384 Ops.erase(Ops.begin());
1388 if (Ops.size() == 1) return Ops[0];
1391 // Okay, check to see if the same value occurs in the operand list more than
1392 // once. If so, merge them together into an multiply expression. Since we
1393 // sorted the list, these values are required to be adjacent.
1394 const Type *Ty = Ops[0]->getType();
1395 bool FoundMatch = false;
1396 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1397 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1398 // Scan ahead to count how many equal operands there are.
1400 while (i+Count != e && Ops[i+Count] == Ops[i])
1402 // Merge the values into a multiply.
1403 const SCEV *Scale = getConstant(Ty, Count);
1404 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1405 if (Ops.size() == Count)
1408 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1409 --i; e -= Count - 1;
1413 return getAddExpr(Ops, HasNUW, HasNSW);
1415 // Check for truncates. If all the operands are truncated from the same
1416 // type, see if factoring out the truncate would permit the result to be
1417 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1418 // if the contents of the resulting outer trunc fold to something simple.
1419 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1420 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1421 const Type *DstType = Trunc->getType();
1422 const Type *SrcType = Trunc->getOperand()->getType();
1423 SmallVector<const SCEV *, 8> LargeOps;
1425 // Check all the operands to see if they can be represented in the
1426 // source type of the truncate.
1427 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1428 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1429 if (T->getOperand()->getType() != SrcType) {
1433 LargeOps.push_back(T->getOperand());
1434 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1435 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1436 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1437 SmallVector<const SCEV *, 8> LargeMulOps;
1438 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1439 if (const SCEVTruncateExpr *T =
1440 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1441 if (T->getOperand()->getType() != SrcType) {
1445 LargeMulOps.push_back(T->getOperand());
1446 } else if (const SCEVConstant *C =
1447 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1448 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1455 LargeOps.push_back(getMulExpr(LargeMulOps));
1462 // Evaluate the expression in the larger type.
1463 const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
1464 // If it folds to something simple, use it. Otherwise, don't.
1465 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1466 return getTruncateExpr(Fold, DstType);
1470 // Skip past any other cast SCEVs.
1471 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1474 // If there are add operands they would be next.
1475 if (Idx < Ops.size()) {
1476 bool DeletedAdd = false;
1477 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1478 // If we have an add, expand the add operands onto the end of the operands
1480 Ops.erase(Ops.begin()+Idx);
1481 Ops.append(Add->op_begin(), Add->op_end());
1485 // If we deleted at least one add, we added operands to the end of the list,
1486 // and they are not necessarily sorted. Recurse to resort and resimplify
1487 // any operands we just acquired.
1489 return getAddExpr(Ops);
1492 // Skip over the add expression until we get to a multiply.
1493 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1496 // Check to see if there are any folding opportunities present with
1497 // operands multiplied by constant values.
1498 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1499 uint64_t BitWidth = getTypeSizeInBits(Ty);
1500 DenseMap<const SCEV *, APInt> M;
1501 SmallVector<const SCEV *, 8> NewOps;
1502 APInt AccumulatedConstant(BitWidth, 0);
1503 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1504 Ops.data(), Ops.size(),
1505 APInt(BitWidth, 1), *this)) {
1506 // Some interesting folding opportunity is present, so its worthwhile to
1507 // re-generate the operands list. Group the operands by constant scale,
1508 // to avoid multiplying by the same constant scale multiple times.
1509 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1510 for (SmallVector<const SCEV *, 8>::const_iterator I = NewOps.begin(),
1511 E = NewOps.end(); I != E; ++I)
1512 MulOpLists[M.find(*I)->second].push_back(*I);
1513 // Re-generate the operands list.
1515 if (AccumulatedConstant != 0)
1516 Ops.push_back(getConstant(AccumulatedConstant));
1517 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1518 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1520 Ops.push_back(getMulExpr(getConstant(I->first),
1521 getAddExpr(I->second)));
1523 return getConstant(Ty, 0);
1524 if (Ops.size() == 1)
1526 return getAddExpr(Ops);
1530 // If we are adding something to a multiply expression, make sure the
1531 // something is not already an operand of the multiply. If so, merge it into
1533 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1534 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1535 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1536 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1537 if (isa<SCEVConstant>(MulOpSCEV))
1539 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1540 if (MulOpSCEV == Ops[AddOp]) {
1541 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1542 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1543 if (Mul->getNumOperands() != 2) {
1544 // If the multiply has more than two operands, we must get the
1546 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1547 Mul->op_begin()+MulOp);
1548 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1549 InnerMul = getMulExpr(MulOps);
1551 const SCEV *One = getConstant(Ty, 1);
1552 const SCEV *AddOne = getAddExpr(One, InnerMul);
1553 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1554 if (Ops.size() == 2) return OuterMul;
1556 Ops.erase(Ops.begin()+AddOp);
1557 Ops.erase(Ops.begin()+Idx-1);
1559 Ops.erase(Ops.begin()+Idx);
1560 Ops.erase(Ops.begin()+AddOp-1);
1562 Ops.push_back(OuterMul);
1563 return getAddExpr(Ops);
1566 // Check this multiply against other multiplies being added together.
1567 for (unsigned OtherMulIdx = Idx+1;
1568 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1570 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1571 // If MulOp occurs in OtherMul, we can fold the two multiplies
1573 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1574 OMulOp != e; ++OMulOp)
1575 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1576 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1577 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1578 if (Mul->getNumOperands() != 2) {
1579 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1580 Mul->op_begin()+MulOp);
1581 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1582 InnerMul1 = getMulExpr(MulOps);
1584 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1585 if (OtherMul->getNumOperands() != 2) {
1586 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1587 OtherMul->op_begin()+OMulOp);
1588 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
1589 InnerMul2 = getMulExpr(MulOps);
1591 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1592 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1593 if (Ops.size() == 2) return OuterMul;
1594 Ops.erase(Ops.begin()+Idx);
1595 Ops.erase(Ops.begin()+OtherMulIdx-1);
1596 Ops.push_back(OuterMul);
1597 return getAddExpr(Ops);
1603 // If there are any add recurrences in the operands list, see if any other
1604 // added values are loop invariant. If so, we can fold them into the
1606 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1609 // Scan over all recurrences, trying to fold loop invariants into them.
1610 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1611 // Scan all of the other operands to this add and add them to the vector if
1612 // they are loop invariant w.r.t. the recurrence.
1613 SmallVector<const SCEV *, 8> LIOps;
1614 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1615 const Loop *AddRecLoop = AddRec->getLoop();
1616 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1617 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1618 LIOps.push_back(Ops[i]);
1619 Ops.erase(Ops.begin()+i);
1623 // If we found some loop invariants, fold them into the recurrence.
1624 if (!LIOps.empty()) {
1625 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1626 LIOps.push_back(AddRec->getStart());
1628 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1630 AddRecOps[0] = getAddExpr(LIOps);
1632 // Build the new addrec. Propagate the NUW and NSW flags if both the
1633 // outer add and the inner addrec are guaranteed to have no overflow.
1634 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
1635 HasNUW && AddRec->hasNoUnsignedWrap(),
1636 HasNSW && AddRec->hasNoSignedWrap());
1638 // If all of the other operands were loop invariant, we are done.
1639 if (Ops.size() == 1) return NewRec;
1641 // Otherwise, add the folded AddRec by the non-liv parts.
1642 for (unsigned i = 0;; ++i)
1643 if (Ops[i] == AddRec) {
1647 return getAddExpr(Ops);
1650 // Okay, if there weren't any loop invariants to be folded, check to see if
1651 // there are multiple AddRec's with the same loop induction variable being
1652 // added together. If so, we can fold them.
1653 for (unsigned OtherIdx = Idx+1;
1654 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1656 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1657 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
1658 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1660 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1662 if (const SCEVAddRecExpr *OtherAddRec =
1663 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1664 if (OtherAddRec->getLoop() == AddRecLoop) {
1665 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
1667 if (i >= AddRecOps.size()) {
1668 AddRecOps.append(OtherAddRec->op_begin()+i,
1669 OtherAddRec->op_end());
1672 AddRecOps[i] = getAddExpr(AddRecOps[i],
1673 OtherAddRec->getOperand(i));
1675 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1677 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop);
1678 return getAddExpr(Ops);
1681 // Otherwise couldn't fold anything into this recurrence. Move onto the
1685 // Okay, it looks like we really DO need an add expr. Check to see if we
1686 // already have one, otherwise create a new one.
1687 FoldingSetNodeID ID;
1688 ID.AddInteger(scAddExpr);
1689 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1690 ID.AddPointer(Ops[i]);
1693 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1695 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1696 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1697 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1699 UniqueSCEVs.InsertNode(S, IP);
1701 if (HasNUW) S->setHasNoUnsignedWrap(true);
1702 if (HasNSW) S->setHasNoSignedWrap(true);
1706 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1708 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1709 bool HasNUW, bool HasNSW) {
1710 assert(!Ops.empty() && "Cannot get empty mul!");
1711 if (Ops.size() == 1) return Ops[0];
1713 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1714 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1715 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1716 "SCEVMulExpr operand types don't match!");
1719 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1720 if (!HasNUW && HasNSW) {
1722 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1723 E = Ops.end(); I != E; ++I)
1724 if (!isKnownNonNegative(*I)) {
1728 if (All) HasNUW = true;
1731 // Sort by complexity, this groups all similar expression types together.
1732 GroupByComplexity(Ops, LI);
1734 // If there are any constants, fold them together.
1736 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1738 // C1*(C2+V) -> C1*C2 + C1*V
1739 if (Ops.size() == 2)
1740 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1741 if (Add->getNumOperands() == 2 &&
1742 isa<SCEVConstant>(Add->getOperand(0)))
1743 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1744 getMulExpr(LHSC, Add->getOperand(1)));
1747 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1748 // We found two constants, fold them together!
1749 ConstantInt *Fold = ConstantInt::get(getContext(),
1750 LHSC->getValue()->getValue() *
1751 RHSC->getValue()->getValue());
1752 Ops[0] = getConstant(Fold);
1753 Ops.erase(Ops.begin()+1); // Erase the folded element
1754 if (Ops.size() == 1) return Ops[0];
1755 LHSC = cast<SCEVConstant>(Ops[0]);
1758 // If we are left with a constant one being multiplied, strip it off.
1759 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1760 Ops.erase(Ops.begin());
1762 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1763 // If we have a multiply of zero, it will always be zero.
1765 } else if (Ops[0]->isAllOnesValue()) {
1766 // If we have a mul by -1 of an add, try distributing the -1 among the
1768 if (Ops.size() == 2)
1769 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1770 SmallVector<const SCEV *, 4> NewOps;
1771 bool AnyFolded = false;
1772 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1774 const SCEV *Mul = getMulExpr(Ops[0], *I);
1775 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1776 NewOps.push_back(Mul);
1779 return getAddExpr(NewOps);
1783 if (Ops.size() == 1)
1787 // Skip over the add expression until we get to a multiply.
1788 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1791 // If there are mul operands inline them all into this expression.
1792 if (Idx < Ops.size()) {
1793 bool DeletedMul = false;
1794 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1795 // If we have an mul, expand the mul operands onto the end of the operands
1797 Ops.erase(Ops.begin()+Idx);
1798 Ops.append(Mul->op_begin(), Mul->op_end());
1802 // If we deleted at least one mul, we added operands to the end of the list,
1803 // and they are not necessarily sorted. Recurse to resort and resimplify
1804 // any operands we just acquired.
1806 return getMulExpr(Ops);
1809 // If there are any add recurrences in the operands list, see if any other
1810 // added values are loop invariant. If so, we can fold them into the
1812 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1815 // Scan over all recurrences, trying to fold loop invariants into them.
1816 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1817 // Scan all of the other operands to this mul and add them to the vector if
1818 // they are loop invariant w.r.t. the recurrence.
1819 SmallVector<const SCEV *, 8> LIOps;
1820 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1821 const Loop *AddRecLoop = AddRec->getLoop();
1822 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1823 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1824 LIOps.push_back(Ops[i]);
1825 Ops.erase(Ops.begin()+i);
1829 // If we found some loop invariants, fold them into the recurrence.
1830 if (!LIOps.empty()) {
1831 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1832 SmallVector<const SCEV *, 4> NewOps;
1833 NewOps.reserve(AddRec->getNumOperands());
1834 const SCEV *Scale = getMulExpr(LIOps);
1835 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1836 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1838 // Build the new addrec. Propagate the NUW and NSW flags if both the
1839 // outer mul and the inner addrec are guaranteed to have no overflow.
1840 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop,
1841 HasNUW && AddRec->hasNoUnsignedWrap(),
1842 HasNSW && AddRec->hasNoSignedWrap());
1844 // If all of the other operands were loop invariant, we are done.
1845 if (Ops.size() == 1) return NewRec;
1847 // Otherwise, multiply the folded AddRec by the non-liv parts.
1848 for (unsigned i = 0;; ++i)
1849 if (Ops[i] == AddRec) {
1853 return getMulExpr(Ops);
1856 // Okay, if there weren't any loop invariants to be folded, check to see if
1857 // there are multiple AddRec's with the same loop induction variable being
1858 // multiplied together. If so, we can fold them.
1859 for (unsigned OtherIdx = Idx+1;
1860 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1862 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1863 // F * G, where F = {A,+,B}<L> and G = {C,+,D}<L> -->
1864 // {A*C,+,F*D + G*B + B*D}<L>
1865 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1867 if (const SCEVAddRecExpr *OtherAddRec =
1868 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1869 if (OtherAddRec->getLoop() == AddRecLoop) {
1870 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1871 const SCEV *NewStart = getMulExpr(F->getStart(), G->getStart());
1872 const SCEV *B = F->getStepRecurrence(*this);
1873 const SCEV *D = G->getStepRecurrence(*this);
1874 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1877 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1879 if (Ops.size() == 2) return NewAddRec;
1880 Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
1881 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1883 return getMulExpr(Ops);
1886 // Otherwise couldn't fold anything into this recurrence. Move onto the
1890 // Okay, it looks like we really DO need an mul expr. Check to see if we
1891 // already have one, otherwise create a new one.
1892 FoldingSetNodeID ID;
1893 ID.AddInteger(scMulExpr);
1894 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1895 ID.AddPointer(Ops[i]);
1898 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1900 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1901 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1902 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
1904 UniqueSCEVs.InsertNode(S, IP);
1906 if (HasNUW) S->setHasNoUnsignedWrap(true);
1907 if (HasNSW) S->setHasNoSignedWrap(true);
1911 /// getUDivExpr - Get a canonical unsigned division expression, or something
1912 /// simpler if possible.
1913 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
1915 assert(getEffectiveSCEVType(LHS->getType()) ==
1916 getEffectiveSCEVType(RHS->getType()) &&
1917 "SCEVUDivExpr operand types don't match!");
1919 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
1920 if (RHSC->getValue()->equalsInt(1))
1921 return LHS; // X udiv 1 --> x
1922 // If the denominator is zero, the result of the udiv is undefined. Don't
1923 // try to analyze it, because the resolution chosen here may differ from
1924 // the resolution chosen in other parts of the compiler.
1925 if (!RHSC->getValue()->isZero()) {
1926 // Determine if the division can be folded into the operands of
1928 // TODO: Generalize this to non-constants by using known-bits information.
1929 const Type *Ty = LHS->getType();
1930 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
1931 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
1932 // For non-power-of-two values, effectively round the value up to the
1933 // nearest power of two.
1934 if (!RHSC->getValue()->getValue().isPowerOf2())
1936 const IntegerType *ExtTy =
1937 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
1938 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
1939 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
1940 if (const SCEVConstant *Step =
1941 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
1942 if (!Step->getValue()->getValue()
1943 .urem(RHSC->getValue()->getValue()) &&
1944 getZeroExtendExpr(AR, ExtTy) ==
1945 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
1946 getZeroExtendExpr(Step, ExtTy),
1948 SmallVector<const SCEV *, 4> Operands;
1949 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
1950 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
1951 return getAddRecExpr(Operands, AR->getLoop());
1953 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
1954 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
1955 SmallVector<const SCEV *, 4> Operands;
1956 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
1957 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
1958 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
1959 // Find an operand that's safely divisible.
1960 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
1961 const SCEV *Op = M->getOperand(i);
1962 const SCEV *Div = getUDivExpr(Op, RHSC);
1963 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
1964 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
1967 return getMulExpr(Operands);
1971 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
1972 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
1973 SmallVector<const SCEV *, 4> Operands;
1974 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
1975 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
1976 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
1978 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
1979 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
1980 if (isa<SCEVUDivExpr>(Op) ||
1981 getMulExpr(Op, RHS) != A->getOperand(i))
1983 Operands.push_back(Op);
1985 if (Operands.size() == A->getNumOperands())
1986 return getAddExpr(Operands);
1990 // Fold if both operands are constant.
1991 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
1992 Constant *LHSCV = LHSC->getValue();
1993 Constant *RHSCV = RHSC->getValue();
1994 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2000 FoldingSetNodeID ID;
2001 ID.AddInteger(scUDivExpr);
2005 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2006 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2008 UniqueSCEVs.InsertNode(S, IP);
2013 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2014 /// Simplify the expression as much as possible.
2015 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
2016 const SCEV *Step, const Loop *L,
2017 bool HasNUW, bool HasNSW) {
2018 SmallVector<const SCEV *, 4> Operands;
2019 Operands.push_back(Start);
2020 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2021 if (StepChrec->getLoop() == L) {
2022 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2023 return getAddRecExpr(Operands, L);
2026 Operands.push_back(Step);
2027 return getAddRecExpr(Operands, L, HasNUW, HasNSW);
2030 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2031 /// Simplify the expression as much as possible.
2033 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2035 bool HasNUW, bool HasNSW) {
2036 if (Operands.size() == 1) return Operands[0];
2038 const Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2039 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2040 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2041 "SCEVAddRecExpr operand types don't match!");
2042 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2043 assert(isLoopInvariant(Operands[i], L) &&
2044 "SCEVAddRecExpr operand is not loop-invariant!");
2047 if (Operands.back()->isZero()) {
2048 Operands.pop_back();
2049 return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0} --> X
2052 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2053 // use that information to infer NUW and NSW flags. However, computing a
2054 // BE count requires calling getAddRecExpr, so we may not yet have a
2055 // meaningful BE count at this point (and if we don't, we'd be stuck
2056 // with a SCEVCouldNotCompute as the cached BE count).
2058 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
2059 if (!HasNUW && HasNSW) {
2061 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2062 E = Operands.end(); I != E; ++I)
2063 if (!isKnownNonNegative(*I)) {
2067 if (All) HasNUW = true;
2070 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2071 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2072 const Loop *NestedLoop = NestedAR->getLoop();
2073 if (L->contains(NestedLoop) ?
2074 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2075 (!NestedLoop->contains(L) &&
2076 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2077 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2078 NestedAR->op_end());
2079 Operands[0] = NestedAR->getStart();
2080 // AddRecs require their operands be loop-invariant with respect to their
2081 // loops. Don't perform this transformation if it would break this
2083 bool AllInvariant = true;
2084 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2085 if (!isLoopInvariant(Operands[i], L)) {
2086 AllInvariant = false;
2090 NestedOperands[0] = getAddRecExpr(Operands, L);
2091 AllInvariant = true;
2092 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2093 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2094 AllInvariant = false;
2098 // Ok, both add recurrences are valid after the transformation.
2099 return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
2101 // Reset Operands to its original state.
2102 Operands[0] = NestedAR;
2106 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2107 // already have one, otherwise create a new one.
2108 FoldingSetNodeID ID;
2109 ID.AddInteger(scAddRecExpr);
2110 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2111 ID.AddPointer(Operands[i]);
2115 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2117 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2118 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2119 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2120 O, Operands.size(), L);
2121 UniqueSCEVs.InsertNode(S, IP);
2123 if (HasNUW) S->setHasNoUnsignedWrap(true);
2124 if (HasNSW) S->setHasNoSignedWrap(true);
2128 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2130 SmallVector<const SCEV *, 2> Ops;
2133 return getSMaxExpr(Ops);
2137 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2138 assert(!Ops.empty() && "Cannot get empty smax!");
2139 if (Ops.size() == 1) return Ops[0];
2141 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2142 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2143 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2144 "SCEVSMaxExpr operand types don't match!");
2147 // Sort by complexity, this groups all similar expression types together.
2148 GroupByComplexity(Ops, LI);
2150 // If there are any constants, fold them together.
2152 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2154 assert(Idx < Ops.size());
2155 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2156 // We found two constants, fold them together!
2157 ConstantInt *Fold = ConstantInt::get(getContext(),
2158 APIntOps::smax(LHSC->getValue()->getValue(),
2159 RHSC->getValue()->getValue()));
2160 Ops[0] = getConstant(Fold);
2161 Ops.erase(Ops.begin()+1); // Erase the folded element
2162 if (Ops.size() == 1) return Ops[0];
2163 LHSC = cast<SCEVConstant>(Ops[0]);
2166 // If we are left with a constant minimum-int, strip it off.
2167 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2168 Ops.erase(Ops.begin());
2170 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2171 // If we have an smax with a constant maximum-int, it will always be
2176 if (Ops.size() == 1) return Ops[0];
2179 // Find the first SMax
2180 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2183 // Check to see if one of the operands is an SMax. If so, expand its operands
2184 // onto our operand list, and recurse to simplify.
2185 if (Idx < Ops.size()) {
2186 bool DeletedSMax = false;
2187 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2188 Ops.erase(Ops.begin()+Idx);
2189 Ops.append(SMax->op_begin(), SMax->op_end());
2194 return getSMaxExpr(Ops);
2197 // Okay, check to see if the same value occurs in the operand list twice. If
2198 // so, delete one. Since we sorted the list, these values are required to
2200 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2201 // X smax Y smax Y --> X smax Y
2202 // X smax Y --> X, if X is always greater than Y
2203 if (Ops[i] == Ops[i+1] ||
2204 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2205 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2207 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2208 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2212 if (Ops.size() == 1) return Ops[0];
2214 assert(!Ops.empty() && "Reduced smax down to nothing!");
2216 // Okay, it looks like we really DO need an smax expr. Check to see if we
2217 // already have one, otherwise create a new one.
2218 FoldingSetNodeID ID;
2219 ID.AddInteger(scSMaxExpr);
2220 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2221 ID.AddPointer(Ops[i]);
2223 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2224 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2225 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2226 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2228 UniqueSCEVs.InsertNode(S, IP);
2232 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2234 SmallVector<const SCEV *, 2> Ops;
2237 return getUMaxExpr(Ops);
2241 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2242 assert(!Ops.empty() && "Cannot get empty umax!");
2243 if (Ops.size() == 1) return Ops[0];
2245 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2246 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2247 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2248 "SCEVUMaxExpr operand types don't match!");
2251 // Sort by complexity, this groups all similar expression types together.
2252 GroupByComplexity(Ops, LI);
2254 // If there are any constants, fold them together.
2256 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2258 assert(Idx < Ops.size());
2259 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2260 // We found two constants, fold them together!
2261 ConstantInt *Fold = ConstantInt::get(getContext(),
2262 APIntOps::umax(LHSC->getValue()->getValue(),
2263 RHSC->getValue()->getValue()));
2264 Ops[0] = getConstant(Fold);
2265 Ops.erase(Ops.begin()+1); // Erase the folded element
2266 if (Ops.size() == 1) return Ops[0];
2267 LHSC = cast<SCEVConstant>(Ops[0]);
2270 // If we are left with a constant minimum-int, strip it off.
2271 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2272 Ops.erase(Ops.begin());
2274 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2275 // If we have an umax with a constant maximum-int, it will always be
2280 if (Ops.size() == 1) return Ops[0];
2283 // Find the first UMax
2284 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2287 // Check to see if one of the operands is a UMax. If so, expand its operands
2288 // onto our operand list, and recurse to simplify.
2289 if (Idx < Ops.size()) {
2290 bool DeletedUMax = false;
2291 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2292 Ops.erase(Ops.begin()+Idx);
2293 Ops.append(UMax->op_begin(), UMax->op_end());
2298 return getUMaxExpr(Ops);
2301 // Okay, check to see if the same value occurs in the operand list twice. If
2302 // so, delete one. Since we sorted the list, these values are required to
2304 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2305 // X umax Y umax Y --> X umax Y
2306 // X umax Y --> X, if X is always greater than Y
2307 if (Ops[i] == Ops[i+1] ||
2308 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2309 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2311 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2312 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2316 if (Ops.size() == 1) return Ops[0];
2318 assert(!Ops.empty() && "Reduced umax down to nothing!");
2320 // Okay, it looks like we really DO need a umax expr. Check to see if we
2321 // already have one, otherwise create a new one.
2322 FoldingSetNodeID ID;
2323 ID.AddInteger(scUMaxExpr);
2324 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2325 ID.AddPointer(Ops[i]);
2327 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2328 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2329 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2330 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2332 UniqueSCEVs.InsertNode(S, IP);
2336 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2338 // ~smax(~x, ~y) == smin(x, y).
2339 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2342 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2344 // ~umax(~x, ~y) == umin(x, y)
2345 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2348 const SCEV *ScalarEvolution::getSizeOfExpr(const Type *AllocTy) {
2349 // If we have TargetData, we can bypass creating a target-independent
2350 // constant expression and then folding it back into a ConstantInt.
2351 // This is just a compile-time optimization.
2353 return getConstant(TD->getIntPtrType(getContext()),
2354 TD->getTypeAllocSize(AllocTy));
2356 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2357 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2358 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2360 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2361 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2364 const SCEV *ScalarEvolution::getAlignOfExpr(const Type *AllocTy) {
2365 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2366 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2367 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2369 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2370 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2373 const SCEV *ScalarEvolution::getOffsetOfExpr(const StructType *STy,
2375 // If we have TargetData, we can bypass creating a target-independent
2376 // constant expression and then folding it back into a ConstantInt.
2377 // This is just a compile-time optimization.
2379 return getConstant(TD->getIntPtrType(getContext()),
2380 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2382 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2383 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2384 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2386 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2387 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2390 const SCEV *ScalarEvolution::getOffsetOfExpr(const Type *CTy,
2391 Constant *FieldNo) {
2392 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2393 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2394 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2396 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2397 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2400 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2401 // Don't attempt to do anything other than create a SCEVUnknown object
2402 // here. createSCEV only calls getUnknown after checking for all other
2403 // interesting possibilities, and any other code that calls getUnknown
2404 // is doing so in order to hide a value from SCEV canonicalization.
2406 FoldingSetNodeID ID;
2407 ID.AddInteger(scUnknown);
2410 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
2411 assert(cast<SCEVUnknown>(S)->getValue() == V &&
2412 "Stale SCEVUnknown in uniquing map!");
2415 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
2417 FirstUnknown = cast<SCEVUnknown>(S);
2418 UniqueSCEVs.InsertNode(S, IP);
2422 //===----------------------------------------------------------------------===//
2423 // Basic SCEV Analysis and PHI Idiom Recognition Code
2426 /// isSCEVable - Test if values of the given type are analyzable within
2427 /// the SCEV framework. This primarily includes integer types, and it
2428 /// can optionally include pointer types if the ScalarEvolution class
2429 /// has access to target-specific information.
2430 bool ScalarEvolution::isSCEVable(const Type *Ty) const {
2431 // Integers and pointers are always SCEVable.
2432 return Ty->isIntegerTy() || Ty->isPointerTy();
2435 /// getTypeSizeInBits - Return the size in bits of the specified type,
2436 /// for which isSCEVable must return true.
2437 uint64_t ScalarEvolution::getTypeSizeInBits(const Type *Ty) const {
2438 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2440 // If we have a TargetData, use it!
2442 return TD->getTypeSizeInBits(Ty);
2444 // Integer types have fixed sizes.
2445 if (Ty->isIntegerTy())
2446 return Ty->getPrimitiveSizeInBits();
2448 // The only other support type is pointer. Without TargetData, conservatively
2449 // assume pointers are 64-bit.
2450 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2454 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2455 /// the given type and which represents how SCEV will treat the given
2456 /// type, for which isSCEVable must return true. For pointer types,
2457 /// this is the pointer-sized integer type.
2458 const Type *ScalarEvolution::getEffectiveSCEVType(const Type *Ty) const {
2459 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2461 if (Ty->isIntegerTy())
2464 // The only other support type is pointer.
2465 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2466 if (TD) return TD->getIntPtrType(getContext());
2468 // Without TargetData, conservatively assume pointers are 64-bit.
2469 return Type::getInt64Ty(getContext());
2472 const SCEV *ScalarEvolution::getCouldNotCompute() {
2473 return &CouldNotCompute;
2476 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2477 /// expression and create a new one.
2478 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2479 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2481 ValueExprMapType::const_iterator I = ValueExprMap.find(V);
2482 if (I != ValueExprMap.end()) return I->second;
2483 const SCEV *S = createSCEV(V);
2485 // The process of creating a SCEV for V may have caused other SCEVs
2486 // to have been created, so it's necessary to insert the new entry
2487 // from scratch, rather than trying to remember the insert position
2489 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2493 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2495 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2496 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2498 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2500 const Type *Ty = V->getType();
2501 Ty = getEffectiveSCEVType(Ty);
2502 return getMulExpr(V,
2503 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2506 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2507 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2508 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2510 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2512 const Type *Ty = V->getType();
2513 Ty = getEffectiveSCEVType(Ty);
2514 const SCEV *AllOnes =
2515 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2516 return getMinusSCEV(AllOnes, V);
2519 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1,
2520 /// and thus the HasNUW and HasNSW bits apply to the resultant add, not
2521 /// whether the sub would have overflowed.
2522 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
2523 bool HasNUW, bool HasNSW) {
2524 // Fast path: X - X --> 0.
2526 return getConstant(LHS->getType(), 0);
2529 return getAddExpr(LHS, getNegativeSCEV(RHS), HasNUW, HasNSW);
2532 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2533 /// input value to the specified type. If the type must be extended, it is zero
2536 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, const Type *Ty) {
2537 const Type *SrcTy = V->getType();
2538 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2539 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2540 "Cannot truncate or zero extend with non-integer arguments!");
2541 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2542 return V; // No conversion
2543 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2544 return getTruncateExpr(V, Ty);
2545 return getZeroExtendExpr(V, Ty);
2548 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2549 /// input value to the specified type. If the type must be extended, it is sign
2552 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2554 const Type *SrcTy = V->getType();
2555 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2556 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2557 "Cannot truncate or zero extend with non-integer arguments!");
2558 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2559 return V; // No conversion
2560 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2561 return getTruncateExpr(V, Ty);
2562 return getSignExtendExpr(V, Ty);
2565 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2566 /// input value to the specified type. If the type must be extended, it is zero
2567 /// extended. The conversion must not be narrowing.
2569 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, const Type *Ty) {
2570 const Type *SrcTy = V->getType();
2571 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2572 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2573 "Cannot noop or zero extend with non-integer arguments!");
2574 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2575 "getNoopOrZeroExtend cannot truncate!");
2576 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2577 return V; // No conversion
2578 return getZeroExtendExpr(V, Ty);
2581 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2582 /// input value to the specified type. If the type must be extended, it is sign
2583 /// extended. The conversion must not be narrowing.
2585 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, const Type *Ty) {
2586 const Type *SrcTy = V->getType();
2587 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2588 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2589 "Cannot noop or sign extend with non-integer arguments!");
2590 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2591 "getNoopOrSignExtend cannot truncate!");
2592 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2593 return V; // No conversion
2594 return getSignExtendExpr(V, Ty);
2597 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2598 /// the input value to the specified type. If the type must be extended,
2599 /// it is extended with unspecified bits. The conversion must not be
2602 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, const Type *Ty) {
2603 const Type *SrcTy = V->getType();
2604 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2605 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2606 "Cannot noop or any extend with non-integer arguments!");
2607 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2608 "getNoopOrAnyExtend cannot truncate!");
2609 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2610 return V; // No conversion
2611 return getAnyExtendExpr(V, Ty);
2614 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2615 /// input value to the specified type. The conversion must not be widening.
2617 ScalarEvolution::getTruncateOrNoop(const SCEV *V, const Type *Ty) {
2618 const Type *SrcTy = V->getType();
2619 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2620 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2621 "Cannot truncate or noop with non-integer arguments!");
2622 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2623 "getTruncateOrNoop cannot extend!");
2624 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2625 return V; // No conversion
2626 return getTruncateExpr(V, Ty);
2629 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2630 /// the types using zero-extension, and then perform a umax operation
2632 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2634 const SCEV *PromotedLHS = LHS;
2635 const SCEV *PromotedRHS = RHS;
2637 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2638 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2640 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2642 return getUMaxExpr(PromotedLHS, PromotedRHS);
2645 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2646 /// the types using zero-extension, and then perform a umin operation
2648 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2650 const SCEV *PromotedLHS = LHS;
2651 const SCEV *PromotedRHS = RHS;
2653 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2654 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2656 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2658 return getUMinExpr(PromotedLHS, PromotedRHS);
2661 /// PushDefUseChildren - Push users of the given Instruction
2662 /// onto the given Worklist.
2664 PushDefUseChildren(Instruction *I,
2665 SmallVectorImpl<Instruction *> &Worklist) {
2666 // Push the def-use children onto the Worklist stack.
2667 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2669 Worklist.push_back(cast<Instruction>(*UI));
2672 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2673 /// instructions that depend on the given instruction and removes them from
2674 /// the ValueExprMapType map if they reference SymName. This is used during PHI
2677 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2678 SmallVector<Instruction *, 16> Worklist;
2679 PushDefUseChildren(PN, Worklist);
2681 SmallPtrSet<Instruction *, 8> Visited;
2683 while (!Worklist.empty()) {
2684 Instruction *I = Worklist.pop_back_val();
2685 if (!Visited.insert(I)) continue;
2687 ValueExprMapType::iterator It =
2688 ValueExprMap.find(static_cast<Value *>(I));
2689 if (It != ValueExprMap.end()) {
2690 const SCEV *Old = It->second;
2692 // Short-circuit the def-use traversal if the symbolic name
2693 // ceases to appear in expressions.
2694 if (Old != SymName && !hasOperand(Old, SymName))
2697 // SCEVUnknown for a PHI either means that it has an unrecognized
2698 // structure, it's a PHI that's in the progress of being computed
2699 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2700 // additional loop trip count information isn't going to change anything.
2701 // In the second case, createNodeForPHI will perform the necessary
2702 // updates on its own when it gets to that point. In the third, we do
2703 // want to forget the SCEVUnknown.
2704 if (!isa<PHINode>(I) ||
2705 !isa<SCEVUnknown>(Old) ||
2706 (I != PN && Old == SymName)) {
2707 forgetMemoizedResults(Old);
2708 ValueExprMap.erase(It);
2712 PushDefUseChildren(I, Worklist);
2716 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2717 /// a loop header, making it a potential recurrence, or it doesn't.
2719 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2720 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2721 if (L->getHeader() == PN->getParent()) {
2722 // The loop may have multiple entrances or multiple exits; we can analyze
2723 // this phi as an addrec if it has a unique entry value and a unique
2725 Value *BEValueV = 0, *StartValueV = 0;
2726 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2727 Value *V = PN->getIncomingValue(i);
2728 if (L->contains(PN->getIncomingBlock(i))) {
2731 } else if (BEValueV != V) {
2735 } else if (!StartValueV) {
2737 } else if (StartValueV != V) {
2742 if (BEValueV && StartValueV) {
2743 // While we are analyzing this PHI node, handle its value symbolically.
2744 const SCEV *SymbolicName = getUnknown(PN);
2745 assert(ValueExprMap.find(PN) == ValueExprMap.end() &&
2746 "PHI node already processed?");
2747 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2749 // Using this symbolic name for the PHI, analyze the value coming around
2751 const SCEV *BEValue = getSCEV(BEValueV);
2753 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2754 // has a special value for the first iteration of the loop.
2756 // If the value coming around the backedge is an add with the symbolic
2757 // value we just inserted, then we found a simple induction variable!
2758 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2759 // If there is a single occurrence of the symbolic value, replace it
2760 // with a recurrence.
2761 unsigned FoundIndex = Add->getNumOperands();
2762 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2763 if (Add->getOperand(i) == SymbolicName)
2764 if (FoundIndex == e) {
2769 if (FoundIndex != Add->getNumOperands()) {
2770 // Create an add with everything but the specified operand.
2771 SmallVector<const SCEV *, 8> Ops;
2772 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2773 if (i != FoundIndex)
2774 Ops.push_back(Add->getOperand(i));
2775 const SCEV *Accum = getAddExpr(Ops);
2777 // This is not a valid addrec if the step amount is varying each
2778 // loop iteration, but is not itself an addrec in this loop.
2779 if (isLoopInvariant(Accum, L) ||
2780 (isa<SCEVAddRecExpr>(Accum) &&
2781 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2782 bool HasNUW = false;
2783 bool HasNSW = false;
2785 // If the increment doesn't overflow, then neither the addrec nor
2786 // the post-increment will overflow.
2787 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2788 if (OBO->hasNoUnsignedWrap())
2790 if (OBO->hasNoSignedWrap())
2792 } else if (const GEPOperator *GEP =
2793 dyn_cast<GEPOperator>(BEValueV)) {
2794 // If the increment is a GEP, then we know it won't perform an
2795 // unsigned overflow, because the address space cannot be
2797 HasNUW |= GEP->isInBounds();
2800 const SCEV *StartVal = getSCEV(StartValueV);
2801 const SCEV *PHISCEV =
2802 getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
2804 // Since the no-wrap flags are on the increment, they apply to the
2805 // post-incremented value as well.
2806 if (isLoopInvariant(Accum, L))
2807 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2808 Accum, L, HasNUW, HasNSW);
2810 // Okay, for the entire analysis of this edge we assumed the PHI
2811 // to be symbolic. We now need to go back and purge all of the
2812 // entries for the scalars that use the symbolic expression.
2813 ForgetSymbolicName(PN, SymbolicName);
2814 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2818 } else if (const SCEVAddRecExpr *AddRec =
2819 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2820 // Otherwise, this could be a loop like this:
2821 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2822 // In this case, j = {1,+,1} and BEValue is j.
2823 // Because the other in-value of i (0) fits the evolution of BEValue
2824 // i really is an addrec evolution.
2825 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2826 const SCEV *StartVal = getSCEV(StartValueV);
2828 // If StartVal = j.start - j.stride, we can use StartVal as the
2829 // initial step of the addrec evolution.
2830 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2831 AddRec->getOperand(1))) {
2832 const SCEV *PHISCEV =
2833 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
2835 // Okay, for the entire analysis of this edge we assumed the PHI
2836 // to be symbolic. We now need to go back and purge all of the
2837 // entries for the scalars that use the symbolic expression.
2838 ForgetSymbolicName(PN, SymbolicName);
2839 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2847 // If the PHI has a single incoming value, follow that value, unless the
2848 // PHI's incoming blocks are in a different loop, in which case doing so
2849 // risks breaking LCSSA form. Instcombine would normally zap these, but
2850 // it doesn't have DominatorTree information, so it may miss cases.
2851 if (Value *V = SimplifyInstruction(PN, TD, DT))
2852 if (LI->replacementPreservesLCSSAForm(PN, V))
2855 // If it's not a loop phi, we can't handle it yet.
2856 return getUnknown(PN);
2859 /// createNodeForGEP - Expand GEP instructions into add and multiply
2860 /// operations. This allows them to be analyzed by regular SCEV code.
2862 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
2864 // Don't blindly transfer the inbounds flag from the GEP instruction to the
2865 // Add expression, because the Instruction may be guarded by control flow
2866 // and the no-overflow bits may not be valid for the expression in any
2869 const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
2870 Value *Base = GEP->getOperand(0);
2871 // Don't attempt to analyze GEPs over unsized objects.
2872 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
2873 return getUnknown(GEP);
2874 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
2875 gep_type_iterator GTI = gep_type_begin(GEP);
2876 for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
2880 // Compute the (potentially symbolic) offset in bytes for this index.
2881 if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
2882 // For a struct, add the member offset.
2883 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
2884 const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
2886 // Add the field offset to the running total offset.
2887 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
2889 // For an array, add the element offset, explicitly scaled.
2890 const SCEV *ElementSize = getSizeOfExpr(*GTI);
2891 const SCEV *IndexS = getSCEV(Index);
2892 // Getelementptr indices are signed.
2893 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
2895 // Multiply the index by the element size to compute the element offset.
2896 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize);
2898 // Add the element offset to the running total offset.
2899 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
2903 // Get the SCEV for the GEP base.
2904 const SCEV *BaseS = getSCEV(Base);
2906 // Add the total offset from all the GEP indices to the base.
2907 return getAddExpr(BaseS, TotalOffset);
2910 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
2911 /// guaranteed to end in (at every loop iteration). It is, at the same time,
2912 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
2913 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
2915 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
2916 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2917 return C->getValue()->getValue().countTrailingZeros();
2919 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
2920 return std::min(GetMinTrailingZeros(T->getOperand()),
2921 (uint32_t)getTypeSizeInBits(T->getType()));
2923 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
2924 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2925 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2926 getTypeSizeInBits(E->getType()) : OpRes;
2929 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
2930 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2931 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2932 getTypeSizeInBits(E->getType()) : OpRes;
2935 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
2936 // The result is the min of all operands results.
2937 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2938 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2939 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2943 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
2944 // The result is the sum of all operands results.
2945 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
2946 uint32_t BitWidth = getTypeSizeInBits(M->getType());
2947 for (unsigned i = 1, e = M->getNumOperands();
2948 SumOpRes != BitWidth && i != e; ++i)
2949 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
2954 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
2955 // The result is the min of all operands results.
2956 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2957 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2958 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2962 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
2963 // The result is the min of all operands results.
2964 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2965 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2966 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2970 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
2971 // The result is the min of all operands results.
2972 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2973 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2974 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2978 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2979 // For a SCEVUnknown, ask ValueTracking.
2980 unsigned BitWidth = getTypeSizeInBits(U->getType());
2981 APInt Mask = APInt::getAllOnesValue(BitWidth);
2982 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
2983 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
2984 return Zeros.countTrailingOnes();
2991 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
2994 ScalarEvolution::getUnsignedRange(const SCEV *S) {
2995 // See if we've computed this range already.
2996 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
2997 if (I != UnsignedRanges.end())
3000 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3001 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
3003 unsigned BitWidth = getTypeSizeInBits(S->getType());
3004 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3006 // If the value has known zeros, the maximum unsigned value will have those
3007 // known zeros as well.
3008 uint32_t TZ = GetMinTrailingZeros(S);
3010 ConservativeResult =
3011 ConstantRange(APInt::getMinValue(BitWidth),
3012 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3014 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3015 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3016 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3017 X = X.add(getUnsignedRange(Add->getOperand(i)));
3018 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3021 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3022 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3023 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3024 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3025 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3028 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3029 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3030 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3031 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3032 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3035 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3036 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3037 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3038 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3039 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3042 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3043 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3044 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3045 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3048 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3049 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3050 return setUnsignedRange(ZExt,
3051 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3054 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3055 ConstantRange X = getUnsignedRange(SExt->getOperand());
3056 return setUnsignedRange(SExt,
3057 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3060 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3061 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3062 return setUnsignedRange(Trunc,
3063 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3066 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3067 // If there's no unsigned wrap, the value will never be less than its
3069 if (AddRec->hasNoUnsignedWrap())
3070 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3071 if (!C->getValue()->isZero())
3072 ConservativeResult =
3073 ConservativeResult.intersectWith(
3074 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3076 // TODO: non-affine addrec
3077 if (AddRec->isAffine()) {
3078 const Type *Ty = AddRec->getType();
3079 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3080 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3081 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3082 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3084 const SCEV *Start = AddRec->getStart();
3085 const SCEV *Step = AddRec->getStepRecurrence(*this);
3087 ConstantRange StartRange = getUnsignedRange(Start);
3088 ConstantRange StepRange = getSignedRange(Step);
3089 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3090 ConstantRange EndRange =
3091 StartRange.add(MaxBECountRange.multiply(StepRange));
3093 // Check for overflow. This must be done with ConstantRange arithmetic
3094 // because we could be called from within the ScalarEvolution overflow
3096 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3097 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3098 ConstantRange ExtMaxBECountRange =
3099 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3100 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3101 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3103 return setUnsignedRange(AddRec, ConservativeResult);
3105 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3106 EndRange.getUnsignedMin());
3107 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3108 EndRange.getUnsignedMax());
3109 if (Min.isMinValue() && Max.isMaxValue())
3110 return setUnsignedRange(AddRec, ConservativeResult);
3111 return setUnsignedRange(AddRec,
3112 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3116 return setUnsignedRange(AddRec, ConservativeResult);
3119 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3120 // For a SCEVUnknown, ask ValueTracking.
3121 APInt Mask = APInt::getAllOnesValue(BitWidth);
3122 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3123 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3124 if (Ones == ~Zeros + 1)
3125 return setUnsignedRange(U, ConservativeResult);
3126 return setUnsignedRange(U,
3127 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3130 return setUnsignedRange(S, ConservativeResult);
3133 /// getSignedRange - Determine the signed range for a particular SCEV.
3136 ScalarEvolution::getSignedRange(const SCEV *S) {
3137 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3138 if (I != SignedRanges.end())
3141 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3142 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3144 unsigned BitWidth = getTypeSizeInBits(S->getType());
3145 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3147 // If the value has known zeros, the maximum signed value will have those
3148 // known zeros as well.
3149 uint32_t TZ = GetMinTrailingZeros(S);
3151 ConservativeResult =
3152 ConstantRange(APInt::getSignedMinValue(BitWidth),
3153 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3155 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3156 ConstantRange X = getSignedRange(Add->getOperand(0));
3157 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3158 X = X.add(getSignedRange(Add->getOperand(i)));
3159 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3162 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3163 ConstantRange X = getSignedRange(Mul->getOperand(0));
3164 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3165 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3166 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3169 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3170 ConstantRange X = getSignedRange(SMax->getOperand(0));
3171 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3172 X = X.smax(getSignedRange(SMax->getOperand(i)));
3173 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3176 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3177 ConstantRange X = getSignedRange(UMax->getOperand(0));
3178 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3179 X = X.umax(getSignedRange(UMax->getOperand(i)));
3180 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3183 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3184 ConstantRange X = getSignedRange(UDiv->getLHS());
3185 ConstantRange Y = getSignedRange(UDiv->getRHS());
3186 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3189 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3190 ConstantRange X = getSignedRange(ZExt->getOperand());
3191 return setSignedRange(ZExt,
3192 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3195 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3196 ConstantRange X = getSignedRange(SExt->getOperand());
3197 return setSignedRange(SExt,
3198 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3201 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3202 ConstantRange X = getSignedRange(Trunc->getOperand());
3203 return setSignedRange(Trunc,
3204 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3207 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3208 // If there's no signed wrap, and all the operands have the same sign or
3209 // zero, the value won't ever change sign.
3210 if (AddRec->hasNoSignedWrap()) {
3211 bool AllNonNeg = true;
3212 bool AllNonPos = true;
3213 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3214 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3215 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3218 ConservativeResult = ConservativeResult.intersectWith(
3219 ConstantRange(APInt(BitWidth, 0),
3220 APInt::getSignedMinValue(BitWidth)));
3222 ConservativeResult = ConservativeResult.intersectWith(
3223 ConstantRange(APInt::getSignedMinValue(BitWidth),
3224 APInt(BitWidth, 1)));
3227 // TODO: non-affine addrec
3228 if (AddRec->isAffine()) {
3229 const Type *Ty = AddRec->getType();
3230 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3231 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3232 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3233 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3235 const SCEV *Start = AddRec->getStart();
3236 const SCEV *Step = AddRec->getStepRecurrence(*this);
3238 ConstantRange StartRange = getSignedRange(Start);
3239 ConstantRange StepRange = getSignedRange(Step);
3240 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3241 ConstantRange EndRange =
3242 StartRange.add(MaxBECountRange.multiply(StepRange));
3244 // Check for overflow. This must be done with ConstantRange arithmetic
3245 // because we could be called from within the ScalarEvolution overflow
3247 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3248 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3249 ConstantRange ExtMaxBECountRange =
3250 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3251 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3252 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3254 return setSignedRange(AddRec, ConservativeResult);
3256 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3257 EndRange.getSignedMin());
3258 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3259 EndRange.getSignedMax());
3260 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3261 return setSignedRange(AddRec, ConservativeResult);
3262 return setSignedRange(AddRec,
3263 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3267 return setSignedRange(AddRec, ConservativeResult);
3270 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3271 // For a SCEVUnknown, ask ValueTracking.
3272 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3273 return setSignedRange(U, ConservativeResult);
3274 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3276 return setSignedRange(U, ConservativeResult);
3277 return setSignedRange(U, ConservativeResult.intersectWith(
3278 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3279 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
3282 return setSignedRange(S, ConservativeResult);
3285 /// createSCEV - We know that there is no SCEV for the specified value.
3286 /// Analyze the expression.
3288 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3289 if (!isSCEVable(V->getType()))
3290 return getUnknown(V);
3292 unsigned Opcode = Instruction::UserOp1;
3293 if (Instruction *I = dyn_cast<Instruction>(V)) {
3294 Opcode = I->getOpcode();
3296 // Don't attempt to analyze instructions in blocks that aren't
3297 // reachable. Such instructions don't matter, and they aren't required
3298 // to obey basic rules for definitions dominating uses which this
3299 // analysis depends on.
3300 if (!DT->isReachableFromEntry(I->getParent()))
3301 return getUnknown(V);
3302 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3303 Opcode = CE->getOpcode();
3304 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3305 return getConstant(CI);
3306 else if (isa<ConstantPointerNull>(V))
3307 return getConstant(V->getType(), 0);
3308 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3309 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3311 return getUnknown(V);
3313 Operator *U = cast<Operator>(V);
3315 case Instruction::Add: {
3316 // The simple thing to do would be to just call getSCEV on both operands
3317 // and call getAddExpr with the result. However if we're looking at a
3318 // bunch of things all added together, this can be quite inefficient,
3319 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3320 // Instead, gather up all the operands and make a single getAddExpr call.
3321 // LLVM IR canonical form means we need only traverse the left operands.
3322 SmallVector<const SCEV *, 4> AddOps;
3323 AddOps.push_back(getSCEV(U->getOperand(1)));
3324 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
3325 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
3326 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
3328 U = cast<Operator>(Op);
3329 const SCEV *Op1 = getSCEV(U->getOperand(1));
3330 if (Opcode == Instruction::Sub)
3331 AddOps.push_back(getNegativeSCEV(Op1));
3333 AddOps.push_back(Op1);
3335 AddOps.push_back(getSCEV(U->getOperand(0)));
3336 return getAddExpr(AddOps);
3338 case Instruction::Mul: {
3339 // See the Add code above.
3340 SmallVector<const SCEV *, 4> MulOps;
3341 MulOps.push_back(getSCEV(U->getOperand(1)));
3342 for (Value *Op = U->getOperand(0);
3343 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
3344 Op = U->getOperand(0)) {
3345 U = cast<Operator>(Op);
3346 MulOps.push_back(getSCEV(U->getOperand(1)));
3348 MulOps.push_back(getSCEV(U->getOperand(0)));
3349 return getMulExpr(MulOps);
3351 case Instruction::UDiv:
3352 return getUDivExpr(getSCEV(U->getOperand(0)),
3353 getSCEV(U->getOperand(1)));
3354 case Instruction::Sub:
3355 return getMinusSCEV(getSCEV(U->getOperand(0)),
3356 getSCEV(U->getOperand(1)));
3357 case Instruction::And:
3358 // For an expression like x&255 that merely masks off the high bits,
3359 // use zext(trunc(x)) as the SCEV expression.
3360 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3361 if (CI->isNullValue())
3362 return getSCEV(U->getOperand(1));
3363 if (CI->isAllOnesValue())
3364 return getSCEV(U->getOperand(0));
3365 const APInt &A = CI->getValue();
3367 // Instcombine's ShrinkDemandedConstant may strip bits out of
3368 // constants, obscuring what would otherwise be a low-bits mask.
3369 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3370 // knew about to reconstruct a low-bits mask value.
3371 unsigned LZ = A.countLeadingZeros();
3372 unsigned BitWidth = A.getBitWidth();
3373 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3374 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3375 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3377 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3379 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3381 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3382 IntegerType::get(getContext(), BitWidth - LZ)),
3387 case Instruction::Or:
3388 // If the RHS of the Or is a constant, we may have something like:
3389 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3390 // optimizations will transparently handle this case.
3392 // In order for this transformation to be safe, the LHS must be of the
3393 // form X*(2^n) and the Or constant must be less than 2^n.
3394 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3395 const SCEV *LHS = getSCEV(U->getOperand(0));
3396 const APInt &CIVal = CI->getValue();
3397 if (GetMinTrailingZeros(LHS) >=
3398 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3399 // Build a plain add SCEV.
3400 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3401 // If the LHS of the add was an addrec and it has no-wrap flags,
3402 // transfer the no-wrap flags, since an or won't introduce a wrap.
3403 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3404 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3405 if (OldAR->hasNoUnsignedWrap())
3406 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoUnsignedWrap(true);
3407 if (OldAR->hasNoSignedWrap())
3408 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoSignedWrap(true);
3414 case Instruction::Xor:
3415 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3416 // If the RHS of the xor is a signbit, then this is just an add.
3417 // Instcombine turns add of signbit into xor as a strength reduction step.
3418 if (CI->getValue().isSignBit())
3419 return getAddExpr(getSCEV(U->getOperand(0)),
3420 getSCEV(U->getOperand(1)));
3422 // If the RHS of xor is -1, then this is a not operation.
3423 if (CI->isAllOnesValue())
3424 return getNotSCEV(getSCEV(U->getOperand(0)));
3426 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3427 // This is a variant of the check for xor with -1, and it handles
3428 // the case where instcombine has trimmed non-demanded bits out
3429 // of an xor with -1.
3430 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3431 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3432 if (BO->getOpcode() == Instruction::And &&
3433 LCI->getValue() == CI->getValue())
3434 if (const SCEVZeroExtendExpr *Z =
3435 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3436 const Type *UTy = U->getType();
3437 const SCEV *Z0 = Z->getOperand();
3438 const Type *Z0Ty = Z0->getType();
3439 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3441 // If C is a low-bits mask, the zero extend is serving to
3442 // mask off the high bits. Complement the operand and
3443 // re-apply the zext.
3444 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3445 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3447 // If C is a single bit, it may be in the sign-bit position
3448 // before the zero-extend. In this case, represent the xor
3449 // using an add, which is equivalent, and re-apply the zext.
3450 APInt Trunc = CI->getValue().trunc(Z0TySize);
3451 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3453 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3459 case Instruction::Shl:
3460 // Turn shift left of a constant amount into a multiply.
3461 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3462 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3464 // If the shift count is not less than the bitwidth, the result of
3465 // the shift is undefined. Don't try to analyze it, because the
3466 // resolution chosen here may differ from the resolution chosen in
3467 // other parts of the compiler.
3468 if (SA->getValue().uge(BitWidth))
3471 Constant *X = ConstantInt::get(getContext(),
3472 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3473 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3477 case Instruction::LShr:
3478 // Turn logical shift right of a constant into a unsigned divide.
3479 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3480 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3482 // If the shift count is not less than the bitwidth, the result of
3483 // the shift is undefined. Don't try to analyze it, because the
3484 // resolution chosen here may differ from the resolution chosen in
3485 // other parts of the compiler.
3486 if (SA->getValue().uge(BitWidth))
3489 Constant *X = ConstantInt::get(getContext(),
3490 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3491 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3495 case Instruction::AShr:
3496 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3497 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3498 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3499 if (L->getOpcode() == Instruction::Shl &&
3500 L->getOperand(1) == U->getOperand(1)) {
3501 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3503 // If the shift count is not less than the bitwidth, the result of
3504 // the shift is undefined. Don't try to analyze it, because the
3505 // resolution chosen here may differ from the resolution chosen in
3506 // other parts of the compiler.
3507 if (CI->getValue().uge(BitWidth))
3510 uint64_t Amt = BitWidth - CI->getZExtValue();
3511 if (Amt == BitWidth)
3512 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3514 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3515 IntegerType::get(getContext(),
3521 case Instruction::Trunc:
3522 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3524 case Instruction::ZExt:
3525 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3527 case Instruction::SExt:
3528 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3530 case Instruction::BitCast:
3531 // BitCasts are no-op casts so we just eliminate the cast.
3532 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3533 return getSCEV(U->getOperand(0));
3536 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3537 // lead to pointer expressions which cannot safely be expanded to GEPs,
3538 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3539 // simplifying integer expressions.
3541 case Instruction::GetElementPtr:
3542 return createNodeForGEP(cast<GEPOperator>(U));
3544 case Instruction::PHI:
3545 return createNodeForPHI(cast<PHINode>(U));
3547 case Instruction::Select:
3548 // This could be a smax or umax that was lowered earlier.
3549 // Try to recover it.
3550 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3551 Value *LHS = ICI->getOperand(0);
3552 Value *RHS = ICI->getOperand(1);
3553 switch (ICI->getPredicate()) {
3554 case ICmpInst::ICMP_SLT:
3555 case ICmpInst::ICMP_SLE:
3556 std::swap(LHS, RHS);
3558 case ICmpInst::ICMP_SGT:
3559 case ICmpInst::ICMP_SGE:
3560 // a >s b ? a+x : b+x -> smax(a, b)+x
3561 // a >s b ? b+x : a+x -> smin(a, b)+x
3562 if (LHS->getType() == U->getType()) {
3563 const SCEV *LS = getSCEV(LHS);
3564 const SCEV *RS = getSCEV(RHS);
3565 const SCEV *LA = getSCEV(U->getOperand(1));
3566 const SCEV *RA = getSCEV(U->getOperand(2));
3567 const SCEV *LDiff = getMinusSCEV(LA, LS);
3568 const SCEV *RDiff = getMinusSCEV(RA, RS);
3570 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3571 LDiff = getMinusSCEV(LA, RS);
3572 RDiff = getMinusSCEV(RA, LS);
3574 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3577 case ICmpInst::ICMP_ULT:
3578 case ICmpInst::ICMP_ULE:
3579 std::swap(LHS, RHS);
3581 case ICmpInst::ICMP_UGT:
3582 case ICmpInst::ICMP_UGE:
3583 // a >u b ? a+x : b+x -> umax(a, b)+x
3584 // a >u b ? b+x : a+x -> umin(a, b)+x
3585 if (LHS->getType() == U->getType()) {
3586 const SCEV *LS = getSCEV(LHS);
3587 const SCEV *RS = getSCEV(RHS);
3588 const SCEV *LA = getSCEV(U->getOperand(1));
3589 const SCEV *RA = getSCEV(U->getOperand(2));
3590 const SCEV *LDiff = getMinusSCEV(LA, LS);
3591 const SCEV *RDiff = getMinusSCEV(RA, RS);
3593 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3594 LDiff = getMinusSCEV(LA, RS);
3595 RDiff = getMinusSCEV(RA, LS);
3597 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3600 case ICmpInst::ICMP_NE:
3601 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3602 if (LHS->getType() == U->getType() &&
3603 isa<ConstantInt>(RHS) &&
3604 cast<ConstantInt>(RHS)->isZero()) {
3605 const SCEV *One = getConstant(LHS->getType(), 1);
3606 const SCEV *LS = getSCEV(LHS);
3607 const SCEV *LA = getSCEV(U->getOperand(1));
3608 const SCEV *RA = getSCEV(U->getOperand(2));
3609 const SCEV *LDiff = getMinusSCEV(LA, LS);
3610 const SCEV *RDiff = getMinusSCEV(RA, One);
3612 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3615 case ICmpInst::ICMP_EQ:
3616 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3617 if (LHS->getType() == U->getType() &&
3618 isa<ConstantInt>(RHS) &&
3619 cast<ConstantInt>(RHS)->isZero()) {
3620 const SCEV *One = getConstant(LHS->getType(), 1);
3621 const SCEV *LS = getSCEV(LHS);
3622 const SCEV *LA = getSCEV(U->getOperand(1));
3623 const SCEV *RA = getSCEV(U->getOperand(2));
3624 const SCEV *LDiff = getMinusSCEV(LA, One);
3625 const SCEV *RDiff = getMinusSCEV(RA, LS);
3627 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3635 default: // We cannot analyze this expression.
3639 return getUnknown(V);
3644 //===----------------------------------------------------------------------===//
3645 // Iteration Count Computation Code
3648 /// getBackedgeTakenCount - If the specified loop has a predictable
3649 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3650 /// object. The backedge-taken count is the number of times the loop header
3651 /// will be branched to from within the loop. This is one less than the
3652 /// trip count of the loop, since it doesn't count the first iteration,
3653 /// when the header is branched to from outside the loop.
3655 /// Note that it is not valid to call this method on a loop without a
3656 /// loop-invariant backedge-taken count (see
3657 /// hasLoopInvariantBackedgeTakenCount).
3659 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3660 return getBackedgeTakenInfo(L).Exact;
3663 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3664 /// return the least SCEV value that is known never to be less than the
3665 /// actual backedge taken count.
3666 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3667 return getBackedgeTakenInfo(L).Max;
3670 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3671 /// onto the given Worklist.
3673 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3674 BasicBlock *Header = L->getHeader();
3676 // Push all Loop-header PHIs onto the Worklist stack.
3677 for (BasicBlock::iterator I = Header->begin();
3678 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3679 Worklist.push_back(PN);
3682 const ScalarEvolution::BackedgeTakenInfo &
3683 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3684 // Initially insert a CouldNotCompute for this loop. If the insertion
3685 // succeeds, proceed to actually compute a backedge-taken count and
3686 // update the value. The temporary CouldNotCompute value tells SCEV
3687 // code elsewhere that it shouldn't attempt to request a new
3688 // backedge-taken count, which could result in infinite recursion.
3689 std::pair<std::map<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3690 BackedgeTakenCounts.insert(std::make_pair(L, getCouldNotCompute()));
3692 return Pair.first->second;
3694 BackedgeTakenInfo BECount = ComputeBackedgeTakenCount(L);
3695 if (BECount.Exact != getCouldNotCompute()) {
3696 assert(isLoopInvariant(BECount.Exact, L) &&
3697 isLoopInvariant(BECount.Max, L) &&
3698 "Computed backedge-taken count isn't loop invariant for loop!");
3699 ++NumTripCountsComputed;
3701 // Update the value in the map.
3702 Pair.first->second = BECount;
3704 if (BECount.Max != getCouldNotCompute())
3705 // Update the value in the map.
3706 Pair.first->second = BECount;
3707 if (isa<PHINode>(L->getHeader()->begin()))
3708 // Only count loops that have phi nodes as not being computable.
3709 ++NumTripCountsNotComputed;
3712 // Now that we know more about the trip count for this loop, forget any
3713 // existing SCEV values for PHI nodes in this loop since they are only
3714 // conservative estimates made without the benefit of trip count
3715 // information. This is similar to the code in forgetLoop, except that
3716 // it handles SCEVUnknown PHI nodes specially.
3717 if (BECount.hasAnyInfo()) {
3718 SmallVector<Instruction *, 16> Worklist;
3719 PushLoopPHIs(L, Worklist);
3721 SmallPtrSet<Instruction *, 8> Visited;
3722 while (!Worklist.empty()) {
3723 Instruction *I = Worklist.pop_back_val();
3724 if (!Visited.insert(I)) continue;
3726 ValueExprMapType::iterator It =
3727 ValueExprMap.find(static_cast<Value *>(I));
3728 if (It != ValueExprMap.end()) {
3729 const SCEV *Old = It->second;
3731 // SCEVUnknown for a PHI either means that it has an unrecognized
3732 // structure, or it's a PHI that's in the progress of being computed
3733 // by createNodeForPHI. In the former case, additional loop trip
3734 // count information isn't going to change anything. In the later
3735 // case, createNodeForPHI will perform the necessary updates on its
3736 // own when it gets to that point.
3737 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
3738 forgetMemoizedResults(Old);
3739 ValueExprMap.erase(It);
3741 if (PHINode *PN = dyn_cast<PHINode>(I))
3742 ConstantEvolutionLoopExitValue.erase(PN);
3745 PushDefUseChildren(I, Worklist);
3748 return Pair.first->second;
3751 /// forgetLoop - This method should be called by the client when it has
3752 /// changed a loop in a way that may effect ScalarEvolution's ability to
3753 /// compute a trip count, or if the loop is deleted.
3754 void ScalarEvolution::forgetLoop(const Loop *L) {
3755 // Drop any stored trip count value.
3756 BackedgeTakenCounts.erase(L);
3758 // Drop information about expressions based on loop-header PHIs.
3759 SmallVector<Instruction *, 16> Worklist;
3760 PushLoopPHIs(L, Worklist);
3762 SmallPtrSet<Instruction *, 8> Visited;
3763 while (!Worklist.empty()) {
3764 Instruction *I = Worklist.pop_back_val();
3765 if (!Visited.insert(I)) continue;
3767 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3768 if (It != ValueExprMap.end()) {
3769 forgetMemoizedResults(It->second);
3770 ValueExprMap.erase(It);
3771 if (PHINode *PN = dyn_cast<PHINode>(I))
3772 ConstantEvolutionLoopExitValue.erase(PN);
3775 PushDefUseChildren(I, Worklist);
3778 // Forget all contained loops too, to avoid dangling entries in the
3779 // ValuesAtScopes map.
3780 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
3784 /// forgetValue - This method should be called by the client when it has
3785 /// changed a value in a way that may effect its value, or which may
3786 /// disconnect it from a def-use chain linking it to a loop.
3787 void ScalarEvolution::forgetValue(Value *V) {
3788 Instruction *I = dyn_cast<Instruction>(V);
3791 // Drop information about expressions based on loop-header PHIs.
3792 SmallVector<Instruction *, 16> Worklist;
3793 Worklist.push_back(I);
3795 SmallPtrSet<Instruction *, 8> Visited;
3796 while (!Worklist.empty()) {
3797 I = Worklist.pop_back_val();
3798 if (!Visited.insert(I)) continue;
3800 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3801 if (It != ValueExprMap.end()) {
3802 forgetMemoizedResults(It->second);
3803 ValueExprMap.erase(It);
3804 if (PHINode *PN = dyn_cast<PHINode>(I))
3805 ConstantEvolutionLoopExitValue.erase(PN);
3808 PushDefUseChildren(I, Worklist);
3812 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
3813 /// of the specified loop will execute.
3814 ScalarEvolution::BackedgeTakenInfo
3815 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
3816 SmallVector<BasicBlock *, 8> ExitingBlocks;
3817 L->getExitingBlocks(ExitingBlocks);
3819 // Examine all exits and pick the most conservative values.
3820 const SCEV *BECount = getCouldNotCompute();
3821 const SCEV *MaxBECount = getCouldNotCompute();
3822 bool CouldNotComputeBECount = false;
3823 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
3824 BackedgeTakenInfo NewBTI =
3825 ComputeBackedgeTakenCountFromExit(L, ExitingBlocks[i]);
3827 if (NewBTI.Exact == getCouldNotCompute()) {
3828 // We couldn't compute an exact value for this exit, so
3829 // we won't be able to compute an exact value for the loop.
3830 CouldNotComputeBECount = true;
3831 BECount = getCouldNotCompute();
3832 } else if (!CouldNotComputeBECount) {
3833 if (BECount == getCouldNotCompute())
3834 BECount = NewBTI.Exact;
3836 BECount = getUMinFromMismatchedTypes(BECount, NewBTI.Exact);
3838 if (MaxBECount == getCouldNotCompute())
3839 MaxBECount = NewBTI.Max;
3840 else if (NewBTI.Max != getCouldNotCompute())
3841 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, NewBTI.Max);
3844 return BackedgeTakenInfo(BECount, MaxBECount);
3847 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the backedge
3848 /// of the specified loop will execute if it exits via the specified block.
3849 ScalarEvolution::BackedgeTakenInfo
3850 ScalarEvolution::ComputeBackedgeTakenCountFromExit(const Loop *L,
3851 BasicBlock *ExitingBlock) {
3853 // Okay, we've chosen an exiting block. See what condition causes us to
3854 // exit at this block.
3856 // FIXME: we should be able to handle switch instructions (with a single exit)
3857 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
3858 if (ExitBr == 0) return getCouldNotCompute();
3859 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
3861 // At this point, we know we have a conditional branch that determines whether
3862 // the loop is exited. However, we don't know if the branch is executed each
3863 // time through the loop. If not, then the execution count of the branch will
3864 // not be equal to the trip count of the loop.
3866 // Currently we check for this by checking to see if the Exit branch goes to
3867 // the loop header. If so, we know it will always execute the same number of
3868 // times as the loop. We also handle the case where the exit block *is* the
3869 // loop header. This is common for un-rotated loops.
3871 // If both of those tests fail, walk up the unique predecessor chain to the
3872 // header, stopping if there is an edge that doesn't exit the loop. If the
3873 // header is reached, the execution count of the branch will be equal to the
3874 // trip count of the loop.
3876 // More extensive analysis could be done to handle more cases here.
3878 if (ExitBr->getSuccessor(0) != L->getHeader() &&
3879 ExitBr->getSuccessor(1) != L->getHeader() &&
3880 ExitBr->getParent() != L->getHeader()) {
3881 // The simple checks failed, try climbing the unique predecessor chain
3882 // up to the header.
3884 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
3885 BasicBlock *Pred = BB->getUniquePredecessor();
3887 return getCouldNotCompute();
3888 TerminatorInst *PredTerm = Pred->getTerminator();
3889 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
3890 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
3893 // If the predecessor has a successor that isn't BB and isn't
3894 // outside the loop, assume the worst.
3895 if (L->contains(PredSucc))
3896 return getCouldNotCompute();
3898 if (Pred == L->getHeader()) {
3905 return getCouldNotCompute();
3908 // Proceed to the next level to examine the exit condition expression.
3909 return ComputeBackedgeTakenCountFromExitCond(L, ExitBr->getCondition(),
3910 ExitBr->getSuccessor(0),
3911 ExitBr->getSuccessor(1));
3914 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
3915 /// backedge of the specified loop will execute if its exit condition
3916 /// were a conditional branch of ExitCond, TBB, and FBB.
3917 ScalarEvolution::BackedgeTakenInfo
3918 ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
3922 // Check if the controlling expression for this loop is an And or Or.
3923 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
3924 if (BO->getOpcode() == Instruction::And) {
3925 // Recurse on the operands of the and.
3926 BackedgeTakenInfo BTI0 =
3927 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3928 BackedgeTakenInfo BTI1 =
3929 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3930 const SCEV *BECount = getCouldNotCompute();
3931 const SCEV *MaxBECount = getCouldNotCompute();
3932 if (L->contains(TBB)) {
3933 // Both conditions must be true for the loop to continue executing.
3934 // Choose the less conservative count.
3935 if (BTI0.Exact == getCouldNotCompute() ||
3936 BTI1.Exact == getCouldNotCompute())
3937 BECount = getCouldNotCompute();
3939 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3940 if (BTI0.Max == getCouldNotCompute())
3941 MaxBECount = BTI1.Max;
3942 else if (BTI1.Max == getCouldNotCompute())
3943 MaxBECount = BTI0.Max;
3945 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3947 // Both conditions must be true at the same time for the loop to exit.
3948 // For now, be conservative.
3949 assert(L->contains(FBB) && "Loop block has no successor in loop!");
3950 if (BTI0.Max == BTI1.Max)
3951 MaxBECount = BTI0.Max;
3952 if (BTI0.Exact == BTI1.Exact)
3953 BECount = BTI0.Exact;
3956 return BackedgeTakenInfo(BECount, MaxBECount);
3958 if (BO->getOpcode() == Instruction::Or) {
3959 // Recurse on the operands of the or.
3960 BackedgeTakenInfo BTI0 =
3961 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3962 BackedgeTakenInfo BTI1 =
3963 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3964 const SCEV *BECount = getCouldNotCompute();
3965 const SCEV *MaxBECount = getCouldNotCompute();
3966 if (L->contains(FBB)) {
3967 // Both conditions must be false for the loop to continue executing.
3968 // Choose the less conservative count.
3969 if (BTI0.Exact == getCouldNotCompute() ||
3970 BTI1.Exact == getCouldNotCompute())
3971 BECount = getCouldNotCompute();
3973 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3974 if (BTI0.Max == getCouldNotCompute())
3975 MaxBECount = BTI1.Max;
3976 else if (BTI1.Max == getCouldNotCompute())
3977 MaxBECount = BTI0.Max;
3979 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3981 // Both conditions must be false at the same time for the loop to exit.
3982 // For now, be conservative.
3983 assert(L->contains(TBB) && "Loop block has no successor in loop!");
3984 if (BTI0.Max == BTI1.Max)
3985 MaxBECount = BTI0.Max;
3986 if (BTI0.Exact == BTI1.Exact)
3987 BECount = BTI0.Exact;
3990 return BackedgeTakenInfo(BECount, MaxBECount);
3994 // With an icmp, it may be feasible to compute an exact backedge-taken count.
3995 // Proceed to the next level to examine the icmp.
3996 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
3997 return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
3999 // Check for a constant condition. These are normally stripped out by
4000 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
4001 // preserve the CFG and is temporarily leaving constant conditions
4003 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
4004 if (L->contains(FBB) == !CI->getZExtValue())
4005 // The backedge is always taken.
4006 return getCouldNotCompute();
4008 // The backedge is never taken.
4009 return getConstant(CI->getType(), 0);
4012 // If it's not an integer or pointer comparison then compute it the hard way.
4013 return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4016 static const SCEVAddRecExpr *
4017 isSimpleUnwrappingAddRec(const SCEV *S, const Loop *L) {
4018 const SCEVAddRecExpr *SA = dyn_cast<SCEVAddRecExpr>(S);
4020 // The SCEV must be an addrec of this loop.
4021 if (!SA || SA->getLoop() != L || !SA->isAffine())
4024 // The SCEV must be known to not wrap in some way to be interesting.
4025 if (!SA->hasNoUnsignedWrap() && !SA->hasNoSignedWrap())
4028 // The stride must be a constant so that we know if it is striding up or down.
4029 if (!isa<SCEVConstant>(SA->getOperand(1)))
4034 /// getMinusSCEVForExitTest - When considering an exit test for a loop with a
4035 /// "x != y" exit test, we turn this into a computation that evaluates x-y != 0,
4036 /// and this function returns the expression to use for x-y. We know and take
4037 /// advantage of the fact that this subtraction is only being used in a
4038 /// comparison by zero context.
4040 static const SCEV *getMinusSCEVForExitTest(const SCEV *LHS, const SCEV *RHS,
4041 const Loop *L, ScalarEvolution &SE) {
4042 // If either LHS or RHS is an AddRec SCEV (of this loop) that is known to not
4043 // wrap (either NSW or NUW), then we know that the value will either become
4044 // the other one (and thus the loop terminates), that the loop will terminate
4045 // through some other exit condition first, or that the loop has undefined
4046 // behavior. This information is useful when the addrec has a stride that is
4047 // != 1 or -1, because it means we can't "miss" the exit value.
4049 // In any of these three cases, it is safe to turn the exit condition into a
4050 // "counting down" AddRec (to zero) by subtracting the two inputs as normal,
4051 // but since we know that the "end cannot be missed" we can force the
4052 // resulting AddRec to be a NUW addrec. Since it is counting down, this means
4053 // that the AddRec *cannot* pass zero.
4055 // See if LHS and RHS are addrec's we can handle.
4056 const SCEVAddRecExpr *LHSA = isSimpleUnwrappingAddRec(LHS, L);
4057 const SCEVAddRecExpr *RHSA = isSimpleUnwrappingAddRec(RHS, L);
4059 // If neither addrec is interesting, just return a minus.
4060 if (RHSA == 0 && LHSA == 0)
4061 return SE.getMinusSCEV(LHS, RHS);
4063 // If only one of LHS and RHS are an AddRec of this loop, make sure it is LHS.
4064 if (RHSA && LHSA == 0) {
4065 // Safe because a-b === b-a for comparisons against zero.
4066 std::swap(LHS, RHS);
4067 std::swap(LHSA, RHSA);
4070 // Handle the case when only one is advancing in a non-overflowing way.
4072 // If RHS is loop varying, then we can't predict when LHS will cross it.
4073 if (!SE.isLoopInvariant(RHS, L))
4074 return SE.getMinusSCEV(LHS, RHS);
4076 // If LHS has a positive stride, then we compute RHS-LHS, because the loop
4077 // is counting up until it crosses RHS (which must be larger than LHS). If
4078 // it is negative, we compute LHS-RHS because we're counting down to RHS.
4079 const ConstantInt *Stride =
4080 cast<SCEVConstant>(LHSA->getOperand(1))->getValue();
4081 if (Stride->getValue().isNegative())
4082 std::swap(LHS, RHS);
4084 return SE.getMinusSCEV(RHS, LHS, true /*HasNUW*/);
4087 // If both LHS and RHS are interesting, we have something like:
4089 const ConstantInt *LHSStride =
4090 cast<SCEVConstant>(LHSA->getOperand(1))->getValue();
4091 const ConstantInt *RHSStride =
4092 cast<SCEVConstant>(RHSA->getOperand(1))->getValue();
4094 // If the strides are equal, then this is just a (complex) loop invariant
4095 // comparison of a and b.
4096 if (LHSStride == RHSStride)
4097 return SE.getMinusSCEV(LHSA->getStart(), RHSA->getStart());
4099 // If the signs of the strides differ, then the negative stride is counting
4100 // down to the positive stride.
4101 if (LHSStride->getValue().isNegative() != RHSStride->getValue().isNegative()){
4102 if (RHSStride->getValue().isNegative())
4103 std::swap(LHS, RHS);
4105 // If LHS's stride is smaller than RHS's stride, then "b" must be less than
4106 // "a" and "b" is RHS is counting up (catching up) to LHS. This is true
4107 // whether the strides are positive or negative.
4108 if (RHSStride->getValue().slt(LHSStride->getValue()))
4109 std::swap(LHS, RHS);
4112 return SE.getMinusSCEV(LHS, RHS, true /*HasNUW*/);
4115 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of times the
4116 /// backedge of the specified loop will execute if its exit condition
4117 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4118 ScalarEvolution::BackedgeTakenInfo
4119 ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
4124 // If the condition was exit on true, convert the condition to exit on false
4125 ICmpInst::Predicate Cond;
4126 if (!L->contains(FBB))
4127 Cond = ExitCond->getPredicate();
4129 Cond = ExitCond->getInversePredicate();
4131 // Handle common loops like: for (X = "string"; *X; ++X)
4132 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4133 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4134 BackedgeTakenInfo ItCnt =
4135 ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
4136 if (ItCnt.hasAnyInfo())
4140 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4141 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4143 // Try to evaluate any dependencies out of the loop.
4144 LHS = getSCEVAtScope(LHS, L);
4145 RHS = getSCEVAtScope(RHS, L);
4147 // At this point, we would like to compute how many iterations of the
4148 // loop the predicate will return true for these inputs.
4149 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
4150 // If there is a loop-invariant, force it into the RHS.
4151 std::swap(LHS, RHS);
4152 Cond = ICmpInst::getSwappedPredicate(Cond);
4155 // Simplify the operands before analyzing them.
4156 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4158 // If we have a comparison of a chrec against a constant, try to use value
4159 // ranges to answer this query.
4160 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4161 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4162 if (AddRec->getLoop() == L) {
4163 // Form the constant range.
4164 ConstantRange CompRange(
4165 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4167 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4168 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4172 case ICmpInst::ICMP_NE: { // while (X != Y)
4173 // Convert to: while (X-Y != 0)
4174 BackedgeTakenInfo BTI = HowFarToZero(getMinusSCEVForExitTest(LHS, RHS, L,
4176 if (BTI.hasAnyInfo()) return BTI;
4179 case ICmpInst::ICMP_EQ: { // while (X == Y)
4180 // Convert to: while (X-Y == 0)
4181 BackedgeTakenInfo BTI = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
4182 if (BTI.hasAnyInfo()) return BTI;
4185 case ICmpInst::ICMP_SLT: {
4186 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, true);
4187 if (BTI.hasAnyInfo()) return BTI;
4190 case ICmpInst::ICMP_SGT: {
4191 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4192 getNotSCEV(RHS), L, true);
4193 if (BTI.hasAnyInfo()) return BTI;
4196 case ICmpInst::ICMP_ULT: {
4197 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, false);
4198 if (BTI.hasAnyInfo()) return BTI;
4201 case ICmpInst::ICMP_UGT: {
4202 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4203 getNotSCEV(RHS), L, false);
4204 if (BTI.hasAnyInfo()) return BTI;
4209 dbgs() << "ComputeBackedgeTakenCount ";
4210 if (ExitCond->getOperand(0)->getType()->isUnsigned())
4211 dbgs() << "[unsigned] ";
4212 dbgs() << *LHS << " "
4213 << Instruction::getOpcodeName(Instruction::ICmp)
4214 << " " << *RHS << "\n";
4219 ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4222 static ConstantInt *
4223 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
4224 ScalarEvolution &SE) {
4225 const SCEV *InVal = SE.getConstant(C);
4226 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
4227 assert(isa<SCEVConstant>(Val) &&
4228 "Evaluation of SCEV at constant didn't fold correctly?");
4229 return cast<SCEVConstant>(Val)->getValue();
4232 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
4233 /// and a GEP expression (missing the pointer index) indexing into it, return
4234 /// the addressed element of the initializer or null if the index expression is
4237 GetAddressedElementFromGlobal(GlobalVariable *GV,
4238 const std::vector<ConstantInt*> &Indices) {
4239 Constant *Init = GV->getInitializer();
4240 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
4241 uint64_t Idx = Indices[i]->getZExtValue();
4242 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
4243 assert(Idx < CS->getNumOperands() && "Bad struct index!");
4244 Init = cast<Constant>(CS->getOperand(Idx));
4245 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
4246 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
4247 Init = cast<Constant>(CA->getOperand(Idx));
4248 } else if (isa<ConstantAggregateZero>(Init)) {
4249 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
4250 assert(Idx < STy->getNumElements() && "Bad struct index!");
4251 Init = Constant::getNullValue(STy->getElementType(Idx));
4252 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
4253 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4254 Init = Constant::getNullValue(ATy->getElementType());
4256 llvm_unreachable("Unknown constant aggregate type!");
4260 return 0; // Unknown initializer type
4266 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
4267 /// 'icmp op load X, cst', try to see if we can compute the backedge
4268 /// execution count.
4269 ScalarEvolution::BackedgeTakenInfo
4270 ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
4274 ICmpInst::Predicate predicate) {
4275 if (LI->isVolatile()) return getCouldNotCompute();
4277 // Check to see if the loaded pointer is a getelementptr of a global.
4278 // TODO: Use SCEV instead of manually grubbing with GEPs.
4279 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4280 if (!GEP) return getCouldNotCompute();
4282 // Make sure that it is really a constant global we are gepping, with an
4283 // initializer, and make sure the first IDX is really 0.
4284 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4285 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4286 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4287 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4288 return getCouldNotCompute();
4290 // Okay, we allow one non-constant index into the GEP instruction.
4292 std::vector<ConstantInt*> Indexes;
4293 unsigned VarIdxNum = 0;
4294 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4295 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4296 Indexes.push_back(CI);
4297 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4298 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4299 VarIdx = GEP->getOperand(i);
4301 Indexes.push_back(0);
4304 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4305 // Check to see if X is a loop variant variable value now.
4306 const SCEV *Idx = getSCEV(VarIdx);
4307 Idx = getSCEVAtScope(Idx, L);
4309 // We can only recognize very limited forms of loop index expressions, in
4310 // particular, only affine AddRec's like {C1,+,C2}.
4311 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4312 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
4313 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4314 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4315 return getCouldNotCompute();
4317 unsigned MaxSteps = MaxBruteForceIterations;
4318 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4319 ConstantInt *ItCst = ConstantInt::get(
4320 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4321 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4323 // Form the GEP offset.
4324 Indexes[VarIdxNum] = Val;
4326 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4327 if (Result == 0) break; // Cannot compute!
4329 // Evaluate the condition for this iteration.
4330 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4331 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4332 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4334 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4335 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4338 ++NumArrayLenItCounts;
4339 return getConstant(ItCst); // Found terminating iteration!
4342 return getCouldNotCompute();
4346 /// CanConstantFold - Return true if we can constant fold an instruction of the
4347 /// specified type, assuming that all operands were constants.
4348 static bool CanConstantFold(const Instruction *I) {
4349 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4350 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
4353 if (const CallInst *CI = dyn_cast<CallInst>(I))
4354 if (const Function *F = CI->getCalledFunction())
4355 return canConstantFoldCallTo(F);
4359 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4360 /// in the loop that V is derived from. We allow arbitrary operations along the
4361 /// way, but the operands of an operation must either be constants or a value
4362 /// derived from a constant PHI. If this expression does not fit with these
4363 /// constraints, return null.
4364 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4365 // If this is not an instruction, or if this is an instruction outside of the
4366 // loop, it can't be derived from a loop PHI.
4367 Instruction *I = dyn_cast<Instruction>(V);
4368 if (I == 0 || !L->contains(I)) return 0;
4370 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4371 if (L->getHeader() == I->getParent())
4374 // We don't currently keep track of the control flow needed to evaluate
4375 // PHIs, so we cannot handle PHIs inside of loops.
4379 // If we won't be able to constant fold this expression even if the operands
4380 // are constants, return early.
4381 if (!CanConstantFold(I)) return 0;
4383 // Otherwise, we can evaluate this instruction if all of its operands are
4384 // constant or derived from a PHI node themselves.
4386 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4387 if (!isa<Constant>(I->getOperand(Op))) {
4388 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4389 if (P == 0) return 0; // Not evolving from PHI
4393 return 0; // Evolving from multiple different PHIs.
4396 // This is a expression evolving from a constant PHI!
4400 /// EvaluateExpression - Given an expression that passes the
4401 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4402 /// in the loop has the value PHIVal. If we can't fold this expression for some
4403 /// reason, return null.
4404 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4405 const TargetData *TD) {
4406 if (isa<PHINode>(V)) return PHIVal;
4407 if (Constant *C = dyn_cast<Constant>(V)) return C;
4408 Instruction *I = cast<Instruction>(V);
4410 std::vector<Constant*> Operands(I->getNumOperands());
4412 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4413 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4414 if (Operands[i] == 0) return 0;
4417 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4418 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4420 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4421 &Operands[0], Operands.size(), TD);
4424 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4425 /// in the header of its containing loop, we know the loop executes a
4426 /// constant number of times, and the PHI node is just a recurrence
4427 /// involving constants, fold it.
4429 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4432 std::map<PHINode*, Constant*>::const_iterator I =
4433 ConstantEvolutionLoopExitValue.find(PN);
4434 if (I != ConstantEvolutionLoopExitValue.end())
4437 if (BEs.ugt(MaxBruteForceIterations))
4438 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4440 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4442 // Since the loop is canonicalized, the PHI node must have two entries. One
4443 // entry must be a constant (coming in from outside of the loop), and the
4444 // second must be derived from the same PHI.
4445 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4446 Constant *StartCST =
4447 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4449 return RetVal = 0; // Must be a constant.
4451 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4452 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4453 !isa<Constant>(BEValue))
4454 return RetVal = 0; // Not derived from same PHI.
4456 // Execute the loop symbolically to determine the exit value.
4457 if (BEs.getActiveBits() >= 32)
4458 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4460 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4461 unsigned IterationNum = 0;
4462 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4463 if (IterationNum == NumIterations)
4464 return RetVal = PHIVal; // Got exit value!
4466 // Compute the value of the PHI node for the next iteration.
4467 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4468 if (NextPHI == PHIVal)
4469 return RetVal = NextPHI; // Stopped evolving!
4471 return 0; // Couldn't evaluate!
4476 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute a
4477 /// constant number of times (the condition evolves only from constants),
4478 /// try to evaluate a few iterations of the loop until we get the exit
4479 /// condition gets a value of ExitWhen (true or false). If we cannot
4480 /// evaluate the trip count of the loop, return getCouldNotCompute().
4482 ScalarEvolution::ComputeBackedgeTakenCountExhaustively(const Loop *L,
4485 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4486 if (PN == 0) return getCouldNotCompute();
4488 // If the loop is canonicalized, the PHI will have exactly two entries.
4489 // That's the only form we support here.
4490 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4492 // One entry must be a constant (coming in from outside of the loop), and the
4493 // second must be derived from the same PHI.
4494 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4495 Constant *StartCST =
4496 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4497 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4499 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4500 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4501 !isa<Constant>(BEValue))
4502 return getCouldNotCompute(); // Not derived from same PHI.
4504 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4505 // the loop symbolically to determine when the condition gets a value of
4507 unsigned IterationNum = 0;
4508 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4509 for (Constant *PHIVal = StartCST;
4510 IterationNum != MaxIterations; ++IterationNum) {
4511 ConstantInt *CondVal =
4512 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4514 // Couldn't symbolically evaluate.
4515 if (!CondVal) return getCouldNotCompute();
4517 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4518 ++NumBruteForceTripCountsComputed;
4519 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4522 // Compute the value of the PHI node for the next iteration.
4523 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4524 if (NextPHI == 0 || NextPHI == PHIVal)
4525 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4529 // Too many iterations were needed to evaluate.
4530 return getCouldNotCompute();
4533 /// getSCEVAtScope - Return a SCEV expression for the specified value
4534 /// at the specified scope in the program. The L value specifies a loop
4535 /// nest to evaluate the expression at, where null is the top-level or a
4536 /// specified loop is immediately inside of the loop.
4538 /// This method can be used to compute the exit value for a variable defined
4539 /// in a loop by querying what the value will hold in the parent loop.
4541 /// In the case that a relevant loop exit value cannot be computed, the
4542 /// original value V is returned.
4543 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4544 // Check to see if we've folded this expression at this loop before.
4545 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4546 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4547 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4549 return Pair.first->second ? Pair.first->second : V;
4551 // Otherwise compute it.
4552 const SCEV *C = computeSCEVAtScope(V, L);
4553 ValuesAtScopes[V][L] = C;
4557 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4558 if (isa<SCEVConstant>(V)) return V;
4560 // If this instruction is evolved from a constant-evolving PHI, compute the
4561 // exit value from the loop without using SCEVs.
4562 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4563 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4564 const Loop *LI = (*this->LI)[I->getParent()];
4565 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4566 if (PHINode *PN = dyn_cast<PHINode>(I))
4567 if (PN->getParent() == LI->getHeader()) {
4568 // Okay, there is no closed form solution for the PHI node. Check
4569 // to see if the loop that contains it has a known backedge-taken
4570 // count. If so, we may be able to force computation of the exit
4572 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4573 if (const SCEVConstant *BTCC =
4574 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4575 // Okay, we know how many times the containing loop executes. If
4576 // this is a constant evolving PHI node, get the final value at
4577 // the specified iteration number.
4578 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4579 BTCC->getValue()->getValue(),
4581 if (RV) return getSCEV(RV);
4585 // Okay, this is an expression that we cannot symbolically evaluate
4586 // into a SCEV. Check to see if it's possible to symbolically evaluate
4587 // the arguments into constants, and if so, try to constant propagate the
4588 // result. This is particularly useful for computing loop exit values.
4589 if (CanConstantFold(I)) {
4590 SmallVector<Constant *, 4> Operands;
4591 bool MadeImprovement = false;
4592 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4593 Value *Op = I->getOperand(i);
4594 if (Constant *C = dyn_cast<Constant>(Op)) {
4595 Operands.push_back(C);
4599 // If any of the operands is non-constant and if they are
4600 // non-integer and non-pointer, don't even try to analyze them
4601 // with scev techniques.
4602 if (!isSCEVable(Op->getType()))
4605 const SCEV *OrigV = getSCEV(Op);
4606 const SCEV *OpV = getSCEVAtScope(OrigV, L);
4607 MadeImprovement |= OrigV != OpV;
4610 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
4612 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
4613 C = dyn_cast<Constant>(SU->getValue());
4615 if (C->getType() != Op->getType())
4616 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4620 Operands.push_back(C);
4623 // Check to see if getSCEVAtScope actually made an improvement.
4624 if (MadeImprovement) {
4626 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4627 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4628 Operands[0], Operands[1], TD);
4630 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4631 &Operands[0], Operands.size(), TD);
4638 // This is some other type of SCEVUnknown, just return it.
4642 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4643 // Avoid performing the look-up in the common case where the specified
4644 // expression has no loop-variant portions.
4645 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4646 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4647 if (OpAtScope != Comm->getOperand(i)) {
4648 // Okay, at least one of these operands is loop variant but might be
4649 // foldable. Build a new instance of the folded commutative expression.
4650 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4651 Comm->op_begin()+i);
4652 NewOps.push_back(OpAtScope);
4654 for (++i; i != e; ++i) {
4655 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4656 NewOps.push_back(OpAtScope);
4658 if (isa<SCEVAddExpr>(Comm))
4659 return getAddExpr(NewOps);
4660 if (isa<SCEVMulExpr>(Comm))
4661 return getMulExpr(NewOps);
4662 if (isa<SCEVSMaxExpr>(Comm))
4663 return getSMaxExpr(NewOps);
4664 if (isa<SCEVUMaxExpr>(Comm))
4665 return getUMaxExpr(NewOps);
4666 llvm_unreachable("Unknown commutative SCEV type!");
4669 // If we got here, all operands are loop invariant.
4673 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4674 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4675 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4676 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4677 return Div; // must be loop invariant
4678 return getUDivExpr(LHS, RHS);
4681 // If this is a loop recurrence for a loop that does not contain L, then we
4682 // are dealing with the final value computed by the loop.
4683 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4684 // First, attempt to evaluate each operand.
4685 // Avoid performing the look-up in the common case where the specified
4686 // expression has no loop-variant portions.
4687 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4688 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
4689 if (OpAtScope == AddRec->getOperand(i))
4692 // Okay, at least one of these operands is loop variant but might be
4693 // foldable. Build a new instance of the folded commutative expression.
4694 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
4695 AddRec->op_begin()+i);
4696 NewOps.push_back(OpAtScope);
4697 for (++i; i != e; ++i)
4698 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
4700 AddRec = cast<SCEVAddRecExpr>(getAddRecExpr(NewOps, AddRec->getLoop()));
4704 // If the scope is outside the addrec's loop, evaluate it by using the
4705 // loop exit value of the addrec.
4706 if (!AddRec->getLoop()->contains(L)) {
4707 // To evaluate this recurrence, we need to know how many times the AddRec
4708 // loop iterates. Compute this now.
4709 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4710 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4712 // Then, evaluate the AddRec.
4713 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4719 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4720 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4721 if (Op == Cast->getOperand())
4722 return Cast; // must be loop invariant
4723 return getZeroExtendExpr(Op, Cast->getType());
4726 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4727 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4728 if (Op == Cast->getOperand())
4729 return Cast; // must be loop invariant
4730 return getSignExtendExpr(Op, Cast->getType());
4733 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4734 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4735 if (Op == Cast->getOperand())
4736 return Cast; // must be loop invariant
4737 return getTruncateExpr(Op, Cast->getType());
4740 llvm_unreachable("Unknown SCEV type!");
4744 /// getSCEVAtScope - This is a convenience function which does
4745 /// getSCEVAtScope(getSCEV(V), L).
4746 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4747 return getSCEVAtScope(getSCEV(V), L);
4750 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4751 /// following equation:
4753 /// A * X = B (mod N)
4755 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4756 /// A and B isn't important.
4758 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
4759 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4760 ScalarEvolution &SE) {
4761 uint32_t BW = A.getBitWidth();
4762 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4763 assert(A != 0 && "A must be non-zero.");
4767 // The gcd of A and N may have only one prime factor: 2. The number of
4768 // trailing zeros in A is its multiplicity
4769 uint32_t Mult2 = A.countTrailingZeros();
4772 // 2. Check if B is divisible by D.
4774 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4775 // is not less than multiplicity of this prime factor for D.
4776 if (B.countTrailingZeros() < Mult2)
4777 return SE.getCouldNotCompute();
4779 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4782 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4783 // bit width during computations.
4784 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4785 APInt Mod(BW + 1, 0);
4786 Mod.setBit(BW - Mult2); // Mod = N / D
4787 APInt I = AD.multiplicativeInverse(Mod);
4789 // 4. Compute the minimum unsigned root of the equation:
4790 // I * (B / D) mod (N / D)
4791 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4793 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4795 return SE.getConstant(Result.trunc(BW));
4798 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4799 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4800 /// might be the same) or two SCEVCouldNotCompute objects.
4802 static std::pair<const SCEV *,const SCEV *>
4803 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4804 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4805 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4806 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4807 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4809 // We currently can only solve this if the coefficients are constants.
4810 if (!LC || !MC || !NC) {
4811 const SCEV *CNC = SE.getCouldNotCompute();
4812 return std::make_pair(CNC, CNC);
4815 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4816 const APInt &L = LC->getValue()->getValue();
4817 const APInt &M = MC->getValue()->getValue();
4818 const APInt &N = NC->getValue()->getValue();
4819 APInt Two(BitWidth, 2);
4820 APInt Four(BitWidth, 4);
4823 using namespace APIntOps;
4825 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4826 // The B coefficient is M-N/2
4830 // The A coefficient is N/2
4831 APInt A(N.sdiv(Two));
4833 // Compute the B^2-4ac term.
4836 SqrtTerm -= Four * (A * C);
4838 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4839 // integer value or else APInt::sqrt() will assert.
4840 APInt SqrtVal(SqrtTerm.sqrt());
4842 // Compute the two solutions for the quadratic formula.
4843 // The divisions must be performed as signed divisions.
4845 APInt TwoA( A << 1 );
4846 if (TwoA.isMinValue()) {
4847 const SCEV *CNC = SE.getCouldNotCompute();
4848 return std::make_pair(CNC, CNC);
4851 LLVMContext &Context = SE.getContext();
4853 ConstantInt *Solution1 =
4854 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
4855 ConstantInt *Solution2 =
4856 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
4858 return std::make_pair(SE.getConstant(Solution1),
4859 SE.getConstant(Solution2));
4860 } // end APIntOps namespace
4863 /// HowFarToZero - Return the number of times a backedge comparing the specified
4864 /// value to zero will execute. If not computable, return CouldNotCompute.
4865 ScalarEvolution::BackedgeTakenInfo
4866 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
4867 // If the value is a constant
4868 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4869 // If the value is already zero, the branch will execute zero times.
4870 if (C->getValue()->isZero()) return C;
4871 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4874 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
4875 if (!AddRec || AddRec->getLoop() != L)
4876 return getCouldNotCompute();
4878 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
4879 // the quadratic equation to solve it.
4880 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
4881 std::pair<const SCEV *,const SCEV *> Roots =
4882 SolveQuadraticEquation(AddRec, *this);
4883 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
4884 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
4887 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
4888 << " sol#2: " << *R2 << "\n";
4890 // Pick the smallest positive root value.
4891 if (ConstantInt *CB =
4892 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
4895 if (CB->getZExtValue() == false)
4896 std::swap(R1, R2); // R1 is the minimum root now.
4898 // We can only use this value if the chrec ends up with an exact zero
4899 // value at this index. When solving for "X*X != 5", for example, we
4900 // should not accept a root of 2.
4901 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
4903 return R1; // We found a quadratic root!
4906 return getCouldNotCompute();
4909 // Otherwise we can only handle this if it is affine.
4910 if (!AddRec->isAffine())
4911 return getCouldNotCompute();
4913 // If this is an affine expression, the execution count of this branch is
4914 // the minimum unsigned root of the following equation:
4916 // Start + Step*N = 0 (mod 2^BW)
4920 // Step*N = -Start (mod 2^BW)
4922 // where BW is the common bit width of Start and Step.
4924 // Get the initial value for the loop.
4925 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
4926 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
4928 // If the AddRec is NUW, then (in an unsigned sense) it cannot be counting up
4929 // to wrap to 0, it must be counting down to equal 0. Also, while counting
4930 // down, it cannot "miss" 0 (which would cause it to wrap), regardless of what
4931 // the stride is. As such, NUW addrec's will always become zero in
4932 // "start / -stride" steps, and we know that the division is exact.
4933 if (AddRec->hasNoUnsignedWrap())
4934 // FIXME: We really want an "isexact" bit for udiv.
4935 return getUDivExpr(Start, getNegativeSCEV(Step));
4937 // For now we handle only constant steps.
4938 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
4940 return getCouldNotCompute();
4942 // First, handle unitary steps.
4943 if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
4944 return getNegativeSCEV(Start); // N = -Start (as unsigned)
4946 if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
4947 return Start; // N = Start (as unsigned)
4949 // Then, try to solve the above equation provided that Start is constant.
4950 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
4951 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
4952 -StartC->getValue()->getValue(),
4954 return getCouldNotCompute();
4957 /// HowFarToNonZero - Return the number of times a backedge checking the
4958 /// specified value for nonzero will execute. If not computable, return
4960 ScalarEvolution::BackedgeTakenInfo
4961 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
4962 // Loops that look like: while (X == 0) are very strange indeed. We don't
4963 // handle them yet except for the trivial case. This could be expanded in the
4964 // future as needed.
4966 // If the value is a constant, check to see if it is known to be non-zero
4967 // already. If so, the backedge will execute zero times.
4968 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4969 if (!C->getValue()->isNullValue())
4970 return getConstant(C->getType(), 0);
4971 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4974 // We could implement others, but I really doubt anyone writes loops like
4975 // this, and if they did, they would already be constant folded.
4976 return getCouldNotCompute();
4979 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
4980 /// (which may not be an immediate predecessor) which has exactly one
4981 /// successor from which BB is reachable, or null if no such block is
4984 std::pair<BasicBlock *, BasicBlock *>
4985 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
4986 // If the block has a unique predecessor, then there is no path from the
4987 // predecessor to the block that does not go through the direct edge
4988 // from the predecessor to the block.
4989 if (BasicBlock *Pred = BB->getSinglePredecessor())
4990 return std::make_pair(Pred, BB);
4992 // A loop's header is defined to be a block that dominates the loop.
4993 // If the header has a unique predecessor outside the loop, it must be
4994 // a block that has exactly one successor that can reach the loop.
4995 if (Loop *L = LI->getLoopFor(BB))
4996 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
4998 return std::pair<BasicBlock *, BasicBlock *>();
5001 /// HasSameValue - SCEV structural equivalence is usually sufficient for
5002 /// testing whether two expressions are equal, however for the purposes of
5003 /// looking for a condition guarding a loop, it can be useful to be a little
5004 /// more general, since a front-end may have replicated the controlling
5007 static bool HasSameValue(const SCEV *A, const SCEV *B) {
5008 // Quick check to see if they are the same SCEV.
5009 if (A == B) return true;
5011 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
5012 // two different instructions with the same value. Check for this case.
5013 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
5014 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
5015 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
5016 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
5017 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
5020 // Otherwise assume they may have a different value.
5024 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
5025 /// predicate Pred. Return true iff any changes were made.
5027 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
5028 const SCEV *&LHS, const SCEV *&RHS) {
5029 bool Changed = false;
5031 // Canonicalize a constant to the right side.
5032 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
5033 // Check for both operands constant.
5034 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
5035 if (ConstantExpr::getICmp(Pred,
5037 RHSC->getValue())->isNullValue())
5038 goto trivially_false;
5040 goto trivially_true;
5042 // Otherwise swap the operands to put the constant on the right.
5043 std::swap(LHS, RHS);
5044 Pred = ICmpInst::getSwappedPredicate(Pred);
5048 // If we're comparing an addrec with a value which is loop-invariant in the
5049 // addrec's loop, put the addrec on the left. Also make a dominance check,
5050 // as both operands could be addrecs loop-invariant in each other's loop.
5051 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
5052 const Loop *L = AR->getLoop();
5053 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
5054 std::swap(LHS, RHS);
5055 Pred = ICmpInst::getSwappedPredicate(Pred);
5060 // If there's a constant operand, canonicalize comparisons with boundary
5061 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
5062 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
5063 const APInt &RA = RC->getValue()->getValue();
5065 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5066 case ICmpInst::ICMP_EQ:
5067 case ICmpInst::ICMP_NE:
5069 case ICmpInst::ICMP_UGE:
5070 if ((RA - 1).isMinValue()) {
5071 Pred = ICmpInst::ICMP_NE;
5072 RHS = getConstant(RA - 1);
5076 if (RA.isMaxValue()) {
5077 Pred = ICmpInst::ICMP_EQ;
5081 if (RA.isMinValue()) goto trivially_true;
5083 Pred = ICmpInst::ICMP_UGT;
5084 RHS = getConstant(RA - 1);
5087 case ICmpInst::ICMP_ULE:
5088 if ((RA + 1).isMaxValue()) {
5089 Pred = ICmpInst::ICMP_NE;
5090 RHS = getConstant(RA + 1);
5094 if (RA.isMinValue()) {
5095 Pred = ICmpInst::ICMP_EQ;
5099 if (RA.isMaxValue()) goto trivially_true;
5101 Pred = ICmpInst::ICMP_ULT;
5102 RHS = getConstant(RA + 1);
5105 case ICmpInst::ICMP_SGE:
5106 if ((RA - 1).isMinSignedValue()) {
5107 Pred = ICmpInst::ICMP_NE;
5108 RHS = getConstant(RA - 1);
5112 if (RA.isMaxSignedValue()) {
5113 Pred = ICmpInst::ICMP_EQ;
5117 if (RA.isMinSignedValue()) goto trivially_true;
5119 Pred = ICmpInst::ICMP_SGT;
5120 RHS = getConstant(RA - 1);
5123 case ICmpInst::ICMP_SLE:
5124 if ((RA + 1).isMaxSignedValue()) {
5125 Pred = ICmpInst::ICMP_NE;
5126 RHS = getConstant(RA + 1);
5130 if (RA.isMinSignedValue()) {
5131 Pred = ICmpInst::ICMP_EQ;
5135 if (RA.isMaxSignedValue()) goto trivially_true;
5137 Pred = ICmpInst::ICMP_SLT;
5138 RHS = getConstant(RA + 1);
5141 case ICmpInst::ICMP_UGT:
5142 if (RA.isMinValue()) {
5143 Pred = ICmpInst::ICMP_NE;
5147 if ((RA + 1).isMaxValue()) {
5148 Pred = ICmpInst::ICMP_EQ;
5149 RHS = getConstant(RA + 1);
5153 if (RA.isMaxValue()) goto trivially_false;
5155 case ICmpInst::ICMP_ULT:
5156 if (RA.isMaxValue()) {
5157 Pred = ICmpInst::ICMP_NE;
5161 if ((RA - 1).isMinValue()) {
5162 Pred = ICmpInst::ICMP_EQ;
5163 RHS = getConstant(RA - 1);
5167 if (RA.isMinValue()) goto trivially_false;
5169 case ICmpInst::ICMP_SGT:
5170 if (RA.isMinSignedValue()) {
5171 Pred = ICmpInst::ICMP_NE;
5175 if ((RA + 1).isMaxSignedValue()) {
5176 Pred = ICmpInst::ICMP_EQ;
5177 RHS = getConstant(RA + 1);
5181 if (RA.isMaxSignedValue()) goto trivially_false;
5183 case ICmpInst::ICMP_SLT:
5184 if (RA.isMaxSignedValue()) {
5185 Pred = ICmpInst::ICMP_NE;
5189 if ((RA - 1).isMinSignedValue()) {
5190 Pred = ICmpInst::ICMP_EQ;
5191 RHS = getConstant(RA - 1);
5195 if (RA.isMinSignedValue()) goto trivially_false;
5200 // Check for obvious equality.
5201 if (HasSameValue(LHS, RHS)) {
5202 if (ICmpInst::isTrueWhenEqual(Pred))
5203 goto trivially_true;
5204 if (ICmpInst::isFalseWhenEqual(Pred))
5205 goto trivially_false;
5208 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
5209 // adding or subtracting 1 from one of the operands.
5211 case ICmpInst::ICMP_SLE:
5212 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
5213 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5214 /*HasNUW=*/false, /*HasNSW=*/true);
5215 Pred = ICmpInst::ICMP_SLT;
5217 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
5218 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5219 /*HasNUW=*/false, /*HasNSW=*/true);
5220 Pred = ICmpInst::ICMP_SLT;
5224 case ICmpInst::ICMP_SGE:
5225 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
5226 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5227 /*HasNUW=*/false, /*HasNSW=*/true);
5228 Pred = ICmpInst::ICMP_SGT;
5230 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
5231 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5232 /*HasNUW=*/false, /*HasNSW=*/true);
5233 Pred = ICmpInst::ICMP_SGT;
5237 case ICmpInst::ICMP_ULE:
5238 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
5239 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5240 /*HasNUW=*/true, /*HasNSW=*/false);
5241 Pred = ICmpInst::ICMP_ULT;
5243 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
5244 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5245 /*HasNUW=*/true, /*HasNSW=*/false);
5246 Pred = ICmpInst::ICMP_ULT;
5250 case ICmpInst::ICMP_UGE:
5251 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
5252 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5253 /*HasNUW=*/true, /*HasNSW=*/false);
5254 Pred = ICmpInst::ICMP_UGT;
5256 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
5257 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5258 /*HasNUW=*/true, /*HasNSW=*/false);
5259 Pred = ICmpInst::ICMP_UGT;
5267 // TODO: More simplifications are possible here.
5273 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5274 Pred = ICmpInst::ICMP_EQ;
5279 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5280 Pred = ICmpInst::ICMP_NE;
5284 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
5285 return getSignedRange(S).getSignedMax().isNegative();
5288 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5289 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5292 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5293 return !getSignedRange(S).getSignedMin().isNegative();
5296 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5297 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5300 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5301 return isKnownNegative(S) || isKnownPositive(S);
5304 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5305 const SCEV *LHS, const SCEV *RHS) {
5306 // Canonicalize the inputs first.
5307 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5309 // If LHS or RHS is an addrec, check to see if the condition is true in
5310 // every iteration of the loop.
5311 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5312 if (isLoopEntryGuardedByCond(
5313 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5314 isLoopBackedgeGuardedByCond(
5315 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5317 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5318 if (isLoopEntryGuardedByCond(
5319 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5320 isLoopBackedgeGuardedByCond(
5321 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5324 // Otherwise see what can be done with known constant ranges.
5325 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5329 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5330 const SCEV *LHS, const SCEV *RHS) {
5331 if (HasSameValue(LHS, RHS))
5332 return ICmpInst::isTrueWhenEqual(Pred);
5334 // This code is split out from isKnownPredicate because it is called from
5335 // within isLoopEntryGuardedByCond.
5338 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5340 case ICmpInst::ICMP_SGT:
5341 Pred = ICmpInst::ICMP_SLT;
5342 std::swap(LHS, RHS);
5343 case ICmpInst::ICMP_SLT: {
5344 ConstantRange LHSRange = getSignedRange(LHS);
5345 ConstantRange RHSRange = getSignedRange(RHS);
5346 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5348 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5352 case ICmpInst::ICMP_SGE:
5353 Pred = ICmpInst::ICMP_SLE;
5354 std::swap(LHS, RHS);
5355 case ICmpInst::ICMP_SLE: {
5356 ConstantRange LHSRange = getSignedRange(LHS);
5357 ConstantRange RHSRange = getSignedRange(RHS);
5358 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5360 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5364 case ICmpInst::ICMP_UGT:
5365 Pred = ICmpInst::ICMP_ULT;
5366 std::swap(LHS, RHS);
5367 case ICmpInst::ICMP_ULT: {
5368 ConstantRange LHSRange = getUnsignedRange(LHS);
5369 ConstantRange RHSRange = getUnsignedRange(RHS);
5370 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5372 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5376 case ICmpInst::ICMP_UGE:
5377 Pred = ICmpInst::ICMP_ULE;
5378 std::swap(LHS, RHS);
5379 case ICmpInst::ICMP_ULE: {
5380 ConstantRange LHSRange = getUnsignedRange(LHS);
5381 ConstantRange RHSRange = getUnsignedRange(RHS);
5382 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5384 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5388 case ICmpInst::ICMP_NE: {
5389 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5391 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5394 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5395 if (isKnownNonZero(Diff))
5399 case ICmpInst::ICMP_EQ:
5400 // The check at the top of the function catches the case where
5401 // the values are known to be equal.
5407 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5408 /// protected by a conditional between LHS and RHS. This is used to
5409 /// to eliminate casts.
5411 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5412 ICmpInst::Predicate Pred,
5413 const SCEV *LHS, const SCEV *RHS) {
5414 // Interpret a null as meaning no loop, where there is obviously no guard
5415 // (interprocedural conditions notwithstanding).
5416 if (!L) return true;
5418 BasicBlock *Latch = L->getLoopLatch();
5422 BranchInst *LoopContinuePredicate =
5423 dyn_cast<BranchInst>(Latch->getTerminator());
5424 if (!LoopContinuePredicate ||
5425 LoopContinuePredicate->isUnconditional())
5428 return isImpliedCond(Pred, LHS, RHS,
5429 LoopContinuePredicate->getCondition(),
5430 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
5433 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
5434 /// by a conditional between LHS and RHS. This is used to help avoid max
5435 /// expressions in loop trip counts, and to eliminate casts.
5437 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
5438 ICmpInst::Predicate Pred,
5439 const SCEV *LHS, const SCEV *RHS) {
5440 // Interpret a null as meaning no loop, where there is obviously no guard
5441 // (interprocedural conditions notwithstanding).
5442 if (!L) return false;
5444 // Starting at the loop predecessor, climb up the predecessor chain, as long
5445 // as there are predecessors that can be found that have unique successors
5446 // leading to the original header.
5447 for (std::pair<BasicBlock *, BasicBlock *>
5448 Pair(L->getLoopPredecessor(), L->getHeader());
5450 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
5452 BranchInst *LoopEntryPredicate =
5453 dyn_cast<BranchInst>(Pair.first->getTerminator());
5454 if (!LoopEntryPredicate ||
5455 LoopEntryPredicate->isUnconditional())
5458 if (isImpliedCond(Pred, LHS, RHS,
5459 LoopEntryPredicate->getCondition(),
5460 LoopEntryPredicate->getSuccessor(0) != Pair.second))
5467 /// isImpliedCond - Test whether the condition described by Pred, LHS,
5468 /// and RHS is true whenever the given Cond value evaluates to true.
5469 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
5470 const SCEV *LHS, const SCEV *RHS,
5471 Value *FoundCondValue,
5473 // Recursively handle And and Or conditions.
5474 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
5475 if (BO->getOpcode() == Instruction::And) {
5477 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5478 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5479 } else if (BO->getOpcode() == Instruction::Or) {
5481 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5482 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5486 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
5487 if (!ICI) return false;
5489 // Bail if the ICmp's operands' types are wider than the needed type
5490 // before attempting to call getSCEV on them. This avoids infinite
5491 // recursion, since the analysis of widening casts can require loop
5492 // exit condition information for overflow checking, which would
5494 if (getTypeSizeInBits(LHS->getType()) <
5495 getTypeSizeInBits(ICI->getOperand(0)->getType()))
5498 // Now that we found a conditional branch that dominates the loop, check to
5499 // see if it is the comparison we are looking for.
5500 ICmpInst::Predicate FoundPred;
5502 FoundPred = ICI->getInversePredicate();
5504 FoundPred = ICI->getPredicate();
5506 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
5507 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
5509 // Balance the types. The case where FoundLHS' type is wider than
5510 // LHS' type is checked for above.
5511 if (getTypeSizeInBits(LHS->getType()) >
5512 getTypeSizeInBits(FoundLHS->getType())) {
5513 if (CmpInst::isSigned(Pred)) {
5514 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
5515 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
5517 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
5518 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
5522 // Canonicalize the query to match the way instcombine will have
5523 // canonicalized the comparison.
5524 if (SimplifyICmpOperands(Pred, LHS, RHS))
5526 return CmpInst::isTrueWhenEqual(Pred);
5527 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
5528 if (FoundLHS == FoundRHS)
5529 return CmpInst::isFalseWhenEqual(Pred);
5531 // Check to see if we can make the LHS or RHS match.
5532 if (LHS == FoundRHS || RHS == FoundLHS) {
5533 if (isa<SCEVConstant>(RHS)) {
5534 std::swap(FoundLHS, FoundRHS);
5535 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
5537 std::swap(LHS, RHS);
5538 Pred = ICmpInst::getSwappedPredicate(Pred);
5542 // Check whether the found predicate is the same as the desired predicate.
5543 if (FoundPred == Pred)
5544 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
5546 // Check whether swapping the found predicate makes it the same as the
5547 // desired predicate.
5548 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
5549 if (isa<SCEVConstant>(RHS))
5550 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
5552 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
5553 RHS, LHS, FoundLHS, FoundRHS);
5556 // Check whether the actual condition is beyond sufficient.
5557 if (FoundPred == ICmpInst::ICMP_EQ)
5558 if (ICmpInst::isTrueWhenEqual(Pred))
5559 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
5561 if (Pred == ICmpInst::ICMP_NE)
5562 if (!ICmpInst::isTrueWhenEqual(FoundPred))
5563 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
5566 // Otherwise assume the worst.
5570 /// isImpliedCondOperands - Test whether the condition described by Pred,
5571 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
5572 /// and FoundRHS is true.
5573 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
5574 const SCEV *LHS, const SCEV *RHS,
5575 const SCEV *FoundLHS,
5576 const SCEV *FoundRHS) {
5577 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
5578 FoundLHS, FoundRHS) ||
5579 // ~x < ~y --> x > y
5580 isImpliedCondOperandsHelper(Pred, LHS, RHS,
5581 getNotSCEV(FoundRHS),
5582 getNotSCEV(FoundLHS));
5585 /// isImpliedCondOperandsHelper - Test whether the condition described by
5586 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
5587 /// FoundLHS, and FoundRHS is true.
5589 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
5590 const SCEV *LHS, const SCEV *RHS,
5591 const SCEV *FoundLHS,
5592 const SCEV *FoundRHS) {
5594 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5595 case ICmpInst::ICMP_EQ:
5596 case ICmpInst::ICMP_NE:
5597 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5600 case ICmpInst::ICMP_SLT:
5601 case ICmpInst::ICMP_SLE:
5602 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5603 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5606 case ICmpInst::ICMP_SGT:
5607 case ICmpInst::ICMP_SGE:
5608 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5609 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5612 case ICmpInst::ICMP_ULT:
5613 case ICmpInst::ICMP_ULE:
5614 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5615 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5618 case ICmpInst::ICMP_UGT:
5619 case ICmpInst::ICMP_UGE:
5620 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5621 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5629 /// getBECount - Subtract the end and start values and divide by the step,
5630 /// rounding up, to get the number of times the backedge is executed. Return
5631 /// CouldNotCompute if an intermediate computation overflows.
5632 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5636 assert(!isKnownNegative(Step) &&
5637 "This code doesn't handle negative strides yet!");
5639 const Type *Ty = Start->getType();
5640 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
5641 const SCEV *Diff = getMinusSCEV(End, Start);
5642 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5644 // Add an adjustment to the difference between End and Start so that
5645 // the division will effectively round up.
5646 const SCEV *Add = getAddExpr(Diff, RoundUp);
5649 // Check Add for unsigned overflow.
5650 // TODO: More sophisticated things could be done here.
5651 const Type *WideTy = IntegerType::get(getContext(),
5652 getTypeSizeInBits(Ty) + 1);
5653 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5654 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5655 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5656 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5657 return getCouldNotCompute();
5660 return getUDivExpr(Add, Step);
5663 /// HowManyLessThans - Return the number of times a backedge containing the
5664 /// specified less-than comparison will execute. If not computable, return
5665 /// CouldNotCompute.
5666 ScalarEvolution::BackedgeTakenInfo
5667 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5668 const Loop *L, bool isSigned) {
5669 // Only handle: "ADDREC < LoopInvariant".
5670 if (!isLoopInvariant(RHS, L)) return getCouldNotCompute();
5672 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5673 if (!AddRec || AddRec->getLoop() != L)
5674 return getCouldNotCompute();
5676 // Check to see if we have a flag which makes analysis easy.
5677 bool NoWrap = isSigned ? AddRec->hasNoSignedWrap() :
5678 AddRec->hasNoUnsignedWrap();
5680 if (AddRec->isAffine()) {
5681 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5682 const SCEV *Step = AddRec->getStepRecurrence(*this);
5685 return getCouldNotCompute();
5686 if (Step->isOne()) {
5687 // With unit stride, the iteration never steps past the limit value.
5688 } else if (isKnownPositive(Step)) {
5689 // Test whether a positive iteration can step past the limit
5690 // value and past the maximum value for its type in a single step.
5691 // Note that it's not sufficient to check NoWrap here, because even
5692 // though the value after a wrap is undefined, it's not undefined
5693 // behavior, so if wrap does occur, the loop could either terminate or
5694 // loop infinitely, but in either case, the loop is guaranteed to
5695 // iterate at least until the iteration where the wrapping occurs.
5696 const SCEV *One = getConstant(Step->getType(), 1);
5698 APInt Max = APInt::getSignedMaxValue(BitWidth);
5699 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5700 .slt(getSignedRange(RHS).getSignedMax()))
5701 return getCouldNotCompute();
5703 APInt Max = APInt::getMaxValue(BitWidth);
5704 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5705 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5706 return getCouldNotCompute();
5709 // TODO: Handle negative strides here and below.
5710 return getCouldNotCompute();
5712 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5713 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5714 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5715 // treat m-n as signed nor unsigned due to overflow possibility.
5717 // First, we get the value of the LHS in the first iteration: n
5718 const SCEV *Start = AddRec->getOperand(0);
5720 // Determine the minimum constant start value.
5721 const SCEV *MinStart = getConstant(isSigned ?
5722 getSignedRange(Start).getSignedMin() :
5723 getUnsignedRange(Start).getUnsignedMin());
5725 // If we know that the condition is true in order to enter the loop,
5726 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5727 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5728 // the division must round up.
5729 const SCEV *End = RHS;
5730 if (!isLoopEntryGuardedByCond(L,
5731 isSigned ? ICmpInst::ICMP_SLT :
5733 getMinusSCEV(Start, Step), RHS))
5734 End = isSigned ? getSMaxExpr(RHS, Start)
5735 : getUMaxExpr(RHS, Start);
5737 // Determine the maximum constant end value.
5738 const SCEV *MaxEnd = getConstant(isSigned ?
5739 getSignedRange(End).getSignedMax() :
5740 getUnsignedRange(End).getUnsignedMax());
5742 // If MaxEnd is within a step of the maximum integer value in its type,
5743 // adjust it down to the minimum value which would produce the same effect.
5744 // This allows the subsequent ceiling division of (N+(step-1))/step to
5745 // compute the correct value.
5746 const SCEV *StepMinusOne = getMinusSCEV(Step,
5747 getConstant(Step->getType(), 1));
5750 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5753 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5756 // Finally, we subtract these two values and divide, rounding up, to get
5757 // the number of times the backedge is executed.
5758 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5760 // The maximum backedge count is similar, except using the minimum start
5761 // value and the maximum end value.
5762 const SCEV *MaxBECount = getBECount(MinStart, MaxEnd, Step, NoWrap);
5764 return BackedgeTakenInfo(BECount, MaxBECount);
5767 return getCouldNotCompute();
5770 /// getNumIterationsInRange - Return the number of iterations of this loop that
5771 /// produce values in the specified constant range. Another way of looking at
5772 /// this is that it returns the first iteration number where the value is not in
5773 /// the condition, thus computing the exit count. If the iteration count can't
5774 /// be computed, an instance of SCEVCouldNotCompute is returned.
5775 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5776 ScalarEvolution &SE) const {
5777 if (Range.isFullSet()) // Infinite loop.
5778 return SE.getCouldNotCompute();
5780 // If the start is a non-zero constant, shift the range to simplify things.
5781 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5782 if (!SC->getValue()->isZero()) {
5783 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5784 Operands[0] = SE.getConstant(SC->getType(), 0);
5785 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop());
5786 if (const SCEVAddRecExpr *ShiftedAddRec =
5787 dyn_cast<SCEVAddRecExpr>(Shifted))
5788 return ShiftedAddRec->getNumIterationsInRange(
5789 Range.subtract(SC->getValue()->getValue()), SE);
5790 // This is strange and shouldn't happen.
5791 return SE.getCouldNotCompute();
5794 // The only time we can solve this is when we have all constant indices.
5795 // Otherwise, we cannot determine the overflow conditions.
5796 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5797 if (!isa<SCEVConstant>(getOperand(i)))
5798 return SE.getCouldNotCompute();
5801 // Okay at this point we know that all elements of the chrec are constants and
5802 // that the start element is zero.
5804 // First check to see if the range contains zero. If not, the first
5806 unsigned BitWidth = SE.getTypeSizeInBits(getType());
5807 if (!Range.contains(APInt(BitWidth, 0)))
5808 return SE.getConstant(getType(), 0);
5811 // If this is an affine expression then we have this situation:
5812 // Solve {0,+,A} in Range === Ax in Range
5814 // We know that zero is in the range. If A is positive then we know that
5815 // the upper value of the range must be the first possible exit value.
5816 // If A is negative then the lower of the range is the last possible loop
5817 // value. Also note that we already checked for a full range.
5818 APInt One(BitWidth,1);
5819 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
5820 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
5822 // The exit value should be (End+A)/A.
5823 APInt ExitVal = (End + A).udiv(A);
5824 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
5826 // Evaluate at the exit value. If we really did fall out of the valid
5827 // range, then we computed our trip count, otherwise wrap around or other
5828 // things must have happened.
5829 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
5830 if (Range.contains(Val->getValue()))
5831 return SE.getCouldNotCompute(); // Something strange happened
5833 // Ensure that the previous value is in the range. This is a sanity check.
5834 assert(Range.contains(
5835 EvaluateConstantChrecAtConstant(this,
5836 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
5837 "Linear scev computation is off in a bad way!");
5838 return SE.getConstant(ExitValue);
5839 } else if (isQuadratic()) {
5840 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
5841 // quadratic equation to solve it. To do this, we must frame our problem in
5842 // terms of figuring out when zero is crossed, instead of when
5843 // Range.getUpper() is crossed.
5844 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
5845 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
5846 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
5848 // Next, solve the constructed addrec
5849 std::pair<const SCEV *,const SCEV *> Roots =
5850 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
5851 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5852 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5854 // Pick the smallest positive root value.
5855 if (ConstantInt *CB =
5856 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
5857 R1->getValue(), R2->getValue()))) {
5858 if (CB->getZExtValue() == false)
5859 std::swap(R1, R2); // R1 is the minimum root now.
5861 // Make sure the root is not off by one. The returned iteration should
5862 // not be in the range, but the previous one should be. When solving
5863 // for "X*X < 5", for example, we should not return a root of 2.
5864 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
5867 if (Range.contains(R1Val->getValue())) {
5868 // The next iteration must be out of the range...
5869 ConstantInt *NextVal =
5870 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
5872 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5873 if (!Range.contains(R1Val->getValue()))
5874 return SE.getConstant(NextVal);
5875 return SE.getCouldNotCompute(); // Something strange happened
5878 // If R1 was not in the range, then it is a good return value. Make
5879 // sure that R1-1 WAS in the range though, just in case.
5880 ConstantInt *NextVal =
5881 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
5882 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5883 if (Range.contains(R1Val->getValue()))
5885 return SE.getCouldNotCompute(); // Something strange happened
5890 return SE.getCouldNotCompute();
5895 //===----------------------------------------------------------------------===//
5896 // SCEVCallbackVH Class Implementation
5897 //===----------------------------------------------------------------------===//
5899 void ScalarEvolution::SCEVCallbackVH::deleted() {
5900 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5901 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
5902 SE->ConstantEvolutionLoopExitValue.erase(PN);
5903 SE->ValueExprMap.erase(getValPtr());
5904 // this now dangles!
5907 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
5908 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5910 // Forget all the expressions associated with users of the old value,
5911 // so that future queries will recompute the expressions using the new
5913 Value *Old = getValPtr();
5914 SmallVector<User *, 16> Worklist;
5915 SmallPtrSet<User *, 8> Visited;
5916 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
5918 Worklist.push_back(*UI);
5919 while (!Worklist.empty()) {
5920 User *U = Worklist.pop_back_val();
5921 // Deleting the Old value will cause this to dangle. Postpone
5922 // that until everything else is done.
5925 if (!Visited.insert(U))
5927 if (PHINode *PN = dyn_cast<PHINode>(U))
5928 SE->ConstantEvolutionLoopExitValue.erase(PN);
5929 SE->ValueExprMap.erase(U);
5930 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
5932 Worklist.push_back(*UI);
5934 // Delete the Old value.
5935 if (PHINode *PN = dyn_cast<PHINode>(Old))
5936 SE->ConstantEvolutionLoopExitValue.erase(PN);
5937 SE->ValueExprMap.erase(Old);
5938 // this now dangles!
5941 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
5942 : CallbackVH(V), SE(se) {}
5944 //===----------------------------------------------------------------------===//
5945 // ScalarEvolution Class Implementation
5946 //===----------------------------------------------------------------------===//
5948 ScalarEvolution::ScalarEvolution()
5949 : FunctionPass(ID), FirstUnknown(0) {
5950 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
5953 bool ScalarEvolution::runOnFunction(Function &F) {
5955 LI = &getAnalysis<LoopInfo>();
5956 TD = getAnalysisIfAvailable<TargetData>();
5957 DT = &getAnalysis<DominatorTree>();
5961 void ScalarEvolution::releaseMemory() {
5962 // Iterate through all the SCEVUnknown instances and call their
5963 // destructors, so that they release their references to their values.
5964 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
5968 ValueExprMap.clear();
5969 BackedgeTakenCounts.clear();
5970 ConstantEvolutionLoopExitValue.clear();
5971 ValuesAtScopes.clear();
5972 LoopDispositions.clear();
5973 BlockDispositions.clear();
5974 UnsignedRanges.clear();
5975 SignedRanges.clear();
5976 UniqueSCEVs.clear();
5977 SCEVAllocator.Reset();
5980 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
5981 AU.setPreservesAll();
5982 AU.addRequiredTransitive<LoopInfo>();
5983 AU.addRequiredTransitive<DominatorTree>();
5986 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
5987 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
5990 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
5992 // Print all inner loops first
5993 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
5994 PrintLoopInfo(OS, SE, *I);
5997 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6000 SmallVector<BasicBlock *, 8> ExitBlocks;
6001 L->getExitBlocks(ExitBlocks);
6002 if (ExitBlocks.size() != 1)
6003 OS << "<multiple exits> ";
6005 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
6006 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
6008 OS << "Unpredictable backedge-taken count. ";
6013 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6016 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
6017 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
6019 OS << "Unpredictable max backedge-taken count. ";
6025 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
6026 // ScalarEvolution's implementation of the print method is to print
6027 // out SCEV values of all instructions that are interesting. Doing
6028 // this potentially causes it to create new SCEV objects though,
6029 // which technically conflicts with the const qualifier. This isn't
6030 // observable from outside the class though, so casting away the
6031 // const isn't dangerous.
6032 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6034 OS << "Classifying expressions for: ";
6035 WriteAsOperand(OS, F, /*PrintType=*/false);
6037 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
6038 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
6041 const SCEV *SV = SE.getSCEV(&*I);
6044 const Loop *L = LI->getLoopFor((*I).getParent());
6046 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
6053 OS << "\t\t" "Exits: ";
6054 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
6055 if (!SE.isLoopInvariant(ExitValue, L)) {
6056 OS << "<<Unknown>>";
6065 OS << "Determining loop execution counts for: ";
6066 WriteAsOperand(OS, F, /*PrintType=*/false);
6068 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
6069 PrintLoopInfo(OS, &SE, *I);
6072 ScalarEvolution::LoopDisposition
6073 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
6074 std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
6075 std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
6076 Values.insert(std::make_pair(L, LoopVariant));
6078 return Pair.first->second;
6080 LoopDisposition D = computeLoopDisposition(S, L);
6081 return LoopDispositions[S][L] = D;
6084 ScalarEvolution::LoopDisposition
6085 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
6086 switch (S->getSCEVType()) {
6088 return LoopInvariant;
6092 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
6093 case scAddRecExpr: {
6094 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6096 // If L is the addrec's loop, it's computable.
6097 if (AR->getLoop() == L)
6098 return LoopComputable;
6100 // Add recurrences are never invariant in the function-body (null loop).
6104 // This recurrence is variant w.r.t. L if L contains AR's loop.
6105 if (L->contains(AR->getLoop()))
6108 // This recurrence is invariant w.r.t. L if AR's loop contains L.
6109 if (AR->getLoop()->contains(L))
6110 return LoopInvariant;
6112 // This recurrence is variant w.r.t. L if any of its operands
6114 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
6116 if (!isLoopInvariant(*I, L))
6119 // Otherwise it's loop-invariant.
6120 return LoopInvariant;
6126 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6127 bool HasVarying = false;
6128 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6130 LoopDisposition D = getLoopDisposition(*I, L);
6131 if (D == LoopVariant)
6133 if (D == LoopComputable)
6136 return HasVarying ? LoopComputable : LoopInvariant;
6139 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6140 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
6141 if (LD == LoopVariant)
6143 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
6144 if (RD == LoopVariant)
6146 return (LD == LoopInvariant && RD == LoopInvariant) ?
6147 LoopInvariant : LoopComputable;
6150 // All non-instruction values are loop invariant. All instructions are loop
6151 // invariant if they are not contained in the specified loop.
6152 // Instructions are never considered invariant in the function body
6153 // (null loop) because they are defined within the "loop".
6154 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
6155 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
6156 return LoopInvariant;
6157 case scCouldNotCompute:
6158 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6162 llvm_unreachable("Unknown SCEV kind!");
6166 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
6167 return getLoopDisposition(S, L) == LoopInvariant;
6170 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
6171 return getLoopDisposition(S, L) == LoopComputable;
6174 ScalarEvolution::BlockDisposition
6175 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6176 std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
6177 std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
6178 Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
6180 return Pair.first->second;
6182 BlockDisposition D = computeBlockDisposition(S, BB);
6183 return BlockDispositions[S][BB] = D;
6186 ScalarEvolution::BlockDisposition
6187 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6188 switch (S->getSCEVType()) {
6190 return ProperlyDominatesBlock;
6194 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
6195 case scAddRecExpr: {
6196 // This uses a "dominates" query instead of "properly dominates" query
6197 // to test for proper dominance too, because the instruction which
6198 // produces the addrec's value is a PHI, and a PHI effectively properly
6199 // dominates its entire containing block.
6200 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6201 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
6202 return DoesNotDominateBlock;
6204 // FALL THROUGH into SCEVNAryExpr handling.
6209 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6211 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6213 BlockDisposition D = getBlockDisposition(*I, BB);
6214 if (D == DoesNotDominateBlock)
6215 return DoesNotDominateBlock;
6216 if (D == DominatesBlock)
6219 return Proper ? ProperlyDominatesBlock : DominatesBlock;
6222 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6223 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6224 BlockDisposition LD = getBlockDisposition(LHS, BB);
6225 if (LD == DoesNotDominateBlock)
6226 return DoesNotDominateBlock;
6227 BlockDisposition RD = getBlockDisposition(RHS, BB);
6228 if (RD == DoesNotDominateBlock)
6229 return DoesNotDominateBlock;
6230 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
6231 ProperlyDominatesBlock : DominatesBlock;
6234 if (Instruction *I =
6235 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
6236 if (I->getParent() == BB)
6237 return DominatesBlock;
6238 if (DT->properlyDominates(I->getParent(), BB))
6239 return ProperlyDominatesBlock;
6240 return DoesNotDominateBlock;
6242 return ProperlyDominatesBlock;
6243 case scCouldNotCompute:
6244 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6245 return DoesNotDominateBlock;
6248 llvm_unreachable("Unknown SCEV kind!");
6249 return DoesNotDominateBlock;
6252 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
6253 return getBlockDisposition(S, BB) >= DominatesBlock;
6256 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
6257 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
6260 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
6261 switch (S->getSCEVType()) {
6266 case scSignExtend: {
6267 const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
6268 const SCEV *CastOp = Cast->getOperand();
6269 return Op == CastOp || hasOperand(CastOp, Op);
6276 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6277 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6279 const SCEV *NAryOp = *I;
6280 if (NAryOp == Op || hasOperand(NAryOp, Op))
6286 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6287 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6288 return LHS == Op || hasOperand(LHS, Op) ||
6289 RHS == Op || hasOperand(RHS, Op);
6293 case scCouldNotCompute:
6294 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6298 llvm_unreachable("Unknown SCEV kind!");
6302 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
6303 ValuesAtScopes.erase(S);
6304 LoopDispositions.erase(S);
6305 BlockDispositions.erase(S);
6306 UnsignedRanges.erase(S);
6307 SignedRanges.erase(S);