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/LoopInfo.h"
73 #include "llvm/Analysis/ValueTracking.h"
74 #include "llvm/Assembly/Writer.h"
75 #include "llvm/Target/TargetData.h"
76 #include "llvm/Support/CommandLine.h"
77 #include "llvm/Support/ConstantRange.h"
78 #include "llvm/Support/Debug.h"
79 #include "llvm/Support/ErrorHandling.h"
80 #include "llvm/Support/GetElementPtrTypeIterator.h"
81 #include "llvm/Support/InstIterator.h"
82 #include "llvm/Support/MathExtras.h"
83 #include "llvm/Support/raw_ostream.h"
84 #include "llvm/ADT/Statistic.h"
85 #include "llvm/ADT/STLExtras.h"
86 #include "llvm/ADT/SmallPtrSet.h"
90 STATISTIC(NumArrayLenItCounts,
91 "Number of trip counts computed with array length");
92 STATISTIC(NumTripCountsComputed,
93 "Number of loops with predictable loop counts");
94 STATISTIC(NumTripCountsNotComputed,
95 "Number of loops without predictable loop counts");
96 STATISTIC(NumBruteForceTripCountsComputed,
97 "Number of loops with trip counts computed by force");
99 static cl::opt<unsigned>
100 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
101 cl::desc("Maximum number of iterations SCEV will "
102 "symbolically execute a constant "
106 static RegisterPass<ScalarEvolution>
107 R("scalar-evolution", "Scalar Evolution Analysis", false, true);
108 char ScalarEvolution::ID = 0;
110 //===----------------------------------------------------------------------===//
111 // SCEV class definitions
112 //===----------------------------------------------------------------------===//
114 //===----------------------------------------------------------------------===//
115 // Implementation of the SCEV class.
120 void SCEV::dump() const {
125 bool SCEV::isZero() const {
126 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
127 return SC->getValue()->isZero();
131 bool SCEV::isOne() const {
132 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
133 return SC->getValue()->isOne();
137 bool SCEV::isAllOnesValue() const {
138 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
139 return SC->getValue()->isAllOnesValue();
143 SCEVCouldNotCompute::SCEVCouldNotCompute() :
144 SCEV(FoldingSetNodeID(), scCouldNotCompute) {}
146 bool SCEVCouldNotCompute::isLoopInvariant(const Loop *L) const {
147 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
151 const Type *SCEVCouldNotCompute::getType() const {
152 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
156 bool SCEVCouldNotCompute::hasComputableLoopEvolution(const Loop *L) const {
157 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
161 bool SCEVCouldNotCompute::hasOperand(const SCEV *) const {
162 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
166 void SCEVCouldNotCompute::print(raw_ostream &OS) const {
167 OS << "***COULDNOTCOMPUTE***";
170 bool SCEVCouldNotCompute::classof(const SCEV *S) {
171 return S->getSCEVType() == scCouldNotCompute;
174 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
176 ID.AddInteger(scConstant);
179 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
180 SCEV *S = SCEVAllocator.Allocate<SCEVConstant>();
181 new (S) SCEVConstant(ID, V);
182 UniqueSCEVs.InsertNode(S, IP);
186 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
187 return getConstant(ConstantInt::get(getContext(), Val));
191 ScalarEvolution::getConstant(const Type *Ty, uint64_t V, bool isSigned) {
193 ConstantInt::get(cast<IntegerType>(Ty), V, isSigned));
196 const Type *SCEVConstant::getType() const { return V->getType(); }
198 void SCEVConstant::print(raw_ostream &OS) const {
199 WriteAsOperand(OS, V, false);
202 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeID &ID,
203 unsigned SCEVTy, const SCEV *op, const Type *ty)
204 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
206 bool SCEVCastExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
207 return Op->dominates(BB, DT);
210 bool SCEVCastExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
211 return Op->properlyDominates(BB, DT);
214 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeID &ID,
215 const SCEV *op, const Type *ty)
216 : SCEVCastExpr(ID, scTruncate, op, ty) {
217 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
218 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
219 "Cannot truncate non-integer value!");
222 void SCEVTruncateExpr::print(raw_ostream &OS) const {
223 OS << "(trunc " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
226 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeID &ID,
227 const SCEV *op, const Type *ty)
228 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
229 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
230 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
231 "Cannot zero extend non-integer value!");
234 void SCEVZeroExtendExpr::print(raw_ostream &OS) const {
235 OS << "(zext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
238 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeID &ID,
239 const SCEV *op, const Type *ty)
240 : SCEVCastExpr(ID, scSignExtend, op, ty) {
241 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
242 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
243 "Cannot sign extend non-integer value!");
246 void SCEVSignExtendExpr::print(raw_ostream &OS) const {
247 OS << "(sext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
250 void SCEVCommutativeExpr::print(raw_ostream &OS) const {
251 assert(Operands.size() > 1 && "This plus expr shouldn't exist!");
252 const char *OpStr = getOperationStr();
253 OS << "(" << *Operands[0];
254 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
255 OS << OpStr << *Operands[i];
259 bool SCEVNAryExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
260 for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
261 if (!getOperand(i)->dominates(BB, DT))
267 bool SCEVNAryExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
268 for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
269 if (!getOperand(i)->properlyDominates(BB, DT))
275 bool SCEVUDivExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
276 return LHS->dominates(BB, DT) && RHS->dominates(BB, DT);
279 bool SCEVUDivExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
280 return LHS->properlyDominates(BB, DT) && RHS->properlyDominates(BB, DT);
283 void SCEVUDivExpr::print(raw_ostream &OS) const {
284 OS << "(" << *LHS << " /u " << *RHS << ")";
287 const Type *SCEVUDivExpr::getType() const {
288 // In most cases the types of LHS and RHS will be the same, but in some
289 // crazy cases one or the other may be a pointer. ScalarEvolution doesn't
290 // depend on the type for correctness, but handling types carefully can
291 // avoid extra casts in the SCEVExpander. The LHS is more likely to be
292 // a pointer type than the RHS, so use the RHS' type here.
293 return RHS->getType();
296 bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
297 // Add recurrences are never invariant in the function-body (null loop).
301 // This recurrence is variant w.r.t. QueryLoop if QueryLoop contains L.
302 if (QueryLoop->contains(L))
305 // This recurrence is variant w.r.t. QueryLoop if any of its operands
307 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
308 if (!getOperand(i)->isLoopInvariant(QueryLoop))
311 // Otherwise it's loop-invariant.
316 SCEVAddRecExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
317 return DT->dominates(L->getHeader(), BB) &&
318 SCEVNAryExpr::dominates(BB, DT);
322 SCEVAddRecExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
323 // This uses a "dominates" query instead of "properly dominates" query because
324 // the instruction which produces the addrec's value is a PHI, and a PHI
325 // effectively properly dominates its entire containing block.
326 return DT->dominates(L->getHeader(), BB) &&
327 SCEVNAryExpr::properlyDominates(BB, DT);
330 void SCEVAddRecExpr::print(raw_ostream &OS) const {
331 OS << "{" << *Operands[0];
332 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
333 OS << ",+," << *Operands[i];
335 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
339 bool SCEVUnknown::isLoopInvariant(const Loop *L) const {
340 // All non-instruction values are loop invariant. All instructions are loop
341 // invariant if they are not contained in the specified loop.
342 // Instructions are never considered invariant in the function body
343 // (null loop) because they are defined within the "loop".
344 if (Instruction *I = dyn_cast<Instruction>(V))
345 return L && !L->contains(I);
349 bool SCEVUnknown::dominates(BasicBlock *BB, DominatorTree *DT) const {
350 if (Instruction *I = dyn_cast<Instruction>(getValue()))
351 return DT->dominates(I->getParent(), BB);
355 bool SCEVUnknown::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
356 if (Instruction *I = dyn_cast<Instruction>(getValue()))
357 return DT->properlyDominates(I->getParent(), BB);
361 const Type *SCEVUnknown::getType() const {
365 bool SCEVUnknown::isSizeOf(const Type *&AllocTy) const {
366 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
367 if (VCE->getOpcode() == Instruction::PtrToInt)
368 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
369 if (CE->getOpcode() == Instruction::GetElementPtr &&
370 CE->getOperand(0)->isNullValue() &&
371 CE->getNumOperands() == 2)
372 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
374 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
382 bool SCEVUnknown::isAlignOf(const Type *&AllocTy) const {
383 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
384 if (VCE->getOpcode() == Instruction::PtrToInt)
385 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
386 if (CE->getOpcode() == Instruction::GetElementPtr &&
387 CE->getOperand(0)->isNullValue()) {
389 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
390 if (const StructType *STy = dyn_cast<StructType>(Ty))
391 if (!STy->isPacked() &&
392 CE->getNumOperands() == 3 &&
393 CE->getOperand(1)->isNullValue()) {
394 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
396 STy->getNumElements() == 2 &&
397 STy->getElementType(0)->isIntegerTy(1)) {
398 AllocTy = STy->getElementType(1);
407 bool SCEVUnknown::isOffsetOf(const Type *&CTy, Constant *&FieldNo) const {
408 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
409 if (VCE->getOpcode() == Instruction::PtrToInt)
410 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
411 if (CE->getOpcode() == Instruction::GetElementPtr &&
412 CE->getNumOperands() == 3 &&
413 CE->getOperand(0)->isNullValue() &&
414 CE->getOperand(1)->isNullValue()) {
416 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
417 // Ignore vector types here so that ScalarEvolutionExpander doesn't
418 // emit getelementptrs that index into vectors.
419 if (Ty->isStructTy() || Ty->isArrayTy()) {
421 FieldNo = CE->getOperand(2);
429 void SCEVUnknown::print(raw_ostream &OS) const {
431 if (isSizeOf(AllocTy)) {
432 OS << "sizeof(" << *AllocTy << ")";
435 if (isAlignOf(AllocTy)) {
436 OS << "alignof(" << *AllocTy << ")";
442 if (isOffsetOf(CTy, FieldNo)) {
443 OS << "offsetof(" << *CTy << ", ";
444 WriteAsOperand(OS, FieldNo, false);
449 // Otherwise just print it normally.
450 WriteAsOperand(OS, V, false);
453 //===----------------------------------------------------------------------===//
455 //===----------------------------------------------------------------------===//
457 static bool CompareTypes(const Type *A, const Type *B) {
458 if (A->getTypeID() != B->getTypeID())
459 return A->getTypeID() < B->getTypeID();
460 if (const IntegerType *AI = dyn_cast<IntegerType>(A)) {
461 const IntegerType *BI = cast<IntegerType>(B);
462 return AI->getBitWidth() < BI->getBitWidth();
464 if (const PointerType *AI = dyn_cast<PointerType>(A)) {
465 const PointerType *BI = cast<PointerType>(B);
466 return CompareTypes(AI->getElementType(), BI->getElementType());
468 if (const ArrayType *AI = dyn_cast<ArrayType>(A)) {
469 const ArrayType *BI = cast<ArrayType>(B);
470 if (AI->getNumElements() != BI->getNumElements())
471 return AI->getNumElements() < BI->getNumElements();
472 return CompareTypes(AI->getElementType(), BI->getElementType());
474 if (const VectorType *AI = dyn_cast<VectorType>(A)) {
475 const VectorType *BI = cast<VectorType>(B);
476 if (AI->getNumElements() != BI->getNumElements())
477 return AI->getNumElements() < BI->getNumElements();
478 return CompareTypes(AI->getElementType(), BI->getElementType());
480 if (const StructType *AI = dyn_cast<StructType>(A)) {
481 const StructType *BI = cast<StructType>(B);
482 if (AI->getNumElements() != BI->getNumElements())
483 return AI->getNumElements() < BI->getNumElements();
484 for (unsigned i = 0, e = AI->getNumElements(); i != e; ++i)
485 if (CompareTypes(AI->getElementType(i), BI->getElementType(i)) ||
486 CompareTypes(BI->getElementType(i), AI->getElementType(i)))
487 return CompareTypes(AI->getElementType(i), BI->getElementType(i));
493 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
494 /// than the complexity of the RHS. This comparator is used to canonicalize
496 class SCEVComplexityCompare {
499 explicit SCEVComplexityCompare(LoopInfo *li) : LI(li) {}
501 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
502 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
506 // Primarily, sort the SCEVs by their getSCEVType().
507 if (LHS->getSCEVType() != RHS->getSCEVType())
508 return LHS->getSCEVType() < RHS->getSCEVType();
510 // Aside from the getSCEVType() ordering, the particular ordering
511 // isn't very important except that it's beneficial to be consistent,
512 // so that (a + b) and (b + a) don't end up as different expressions.
514 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
515 // not as complete as it could be.
516 if (const SCEVUnknown *LU = dyn_cast<SCEVUnknown>(LHS)) {
517 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
519 // Order pointer values after integer values. This helps SCEVExpander
521 if (LU->getType()->isPointerTy() && !RU->getType()->isPointerTy())
523 if (RU->getType()->isPointerTy() && !LU->getType()->isPointerTy())
526 // Compare getValueID values.
527 if (LU->getValue()->getValueID() != RU->getValue()->getValueID())
528 return LU->getValue()->getValueID() < RU->getValue()->getValueID();
530 // Sort arguments by their position.
531 if (const Argument *LA = dyn_cast<Argument>(LU->getValue())) {
532 const Argument *RA = cast<Argument>(RU->getValue());
533 return LA->getArgNo() < RA->getArgNo();
536 // For instructions, compare their loop depth, and their opcode.
537 // This is pretty loose.
538 if (Instruction *LV = dyn_cast<Instruction>(LU->getValue())) {
539 Instruction *RV = cast<Instruction>(RU->getValue());
541 // Compare loop depths.
542 if (LI->getLoopDepth(LV->getParent()) !=
543 LI->getLoopDepth(RV->getParent()))
544 return LI->getLoopDepth(LV->getParent()) <
545 LI->getLoopDepth(RV->getParent());
548 if (LV->getOpcode() != RV->getOpcode())
549 return LV->getOpcode() < RV->getOpcode();
551 // Compare the number of operands.
552 if (LV->getNumOperands() != RV->getNumOperands())
553 return LV->getNumOperands() < RV->getNumOperands();
559 // Compare constant values.
560 if (const SCEVConstant *LC = dyn_cast<SCEVConstant>(LHS)) {
561 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
562 if (LC->getValue()->getBitWidth() != RC->getValue()->getBitWidth())
563 return LC->getValue()->getBitWidth() < RC->getValue()->getBitWidth();
564 return LC->getValue()->getValue().ult(RC->getValue()->getValue());
567 // Compare addrec loop depths.
568 if (const SCEVAddRecExpr *LA = dyn_cast<SCEVAddRecExpr>(LHS)) {
569 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
570 if (LA->getLoop()->getLoopDepth() != RA->getLoop()->getLoopDepth())
571 return LA->getLoop()->getLoopDepth() < RA->getLoop()->getLoopDepth();
574 // Lexicographically compare n-ary expressions.
575 if (const SCEVNAryExpr *LC = dyn_cast<SCEVNAryExpr>(LHS)) {
576 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
577 for (unsigned i = 0, e = LC->getNumOperands(); i != e; ++i) {
578 if (i >= RC->getNumOperands())
580 if (operator()(LC->getOperand(i), RC->getOperand(i)))
582 if (operator()(RC->getOperand(i), LC->getOperand(i)))
585 return LC->getNumOperands() < RC->getNumOperands();
588 // Lexicographically compare udiv expressions.
589 if (const SCEVUDivExpr *LC = dyn_cast<SCEVUDivExpr>(LHS)) {
590 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
591 if (operator()(LC->getLHS(), RC->getLHS()))
593 if (operator()(RC->getLHS(), LC->getLHS()))
595 if (operator()(LC->getRHS(), RC->getRHS()))
597 if (operator()(RC->getRHS(), LC->getRHS()))
602 // Compare cast expressions by operand.
603 if (const SCEVCastExpr *LC = dyn_cast<SCEVCastExpr>(LHS)) {
604 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
605 return operator()(LC->getOperand(), RC->getOperand());
608 llvm_unreachable("Unknown SCEV kind!");
614 /// GroupByComplexity - Given a list of SCEV objects, order them by their
615 /// complexity, and group objects of the same complexity together by value.
616 /// When this routine is finished, we know that any duplicates in the vector are
617 /// consecutive and that complexity is monotonically increasing.
619 /// Note that we go take special precautions to ensure that we get determinstic
620 /// results from this routine. In other words, we don't want the results of
621 /// this to depend on where the addresses of various SCEV objects happened to
624 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
626 if (Ops.size() < 2) return; // Noop
627 if (Ops.size() == 2) {
628 // This is the common case, which also happens to be trivially simple.
630 if (SCEVComplexityCompare(LI)(Ops[1], Ops[0]))
631 std::swap(Ops[0], Ops[1]);
635 // Do the rough sort by complexity.
636 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
638 // Now that we are sorted by complexity, group elements of the same
639 // complexity. Note that this is, at worst, N^2, but the vector is likely to
640 // be extremely short in practice. Note that we take this approach because we
641 // do not want to depend on the addresses of the objects we are grouping.
642 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
643 const SCEV *S = Ops[i];
644 unsigned Complexity = S->getSCEVType();
646 // If there are any objects of the same complexity and same value as this
648 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
649 if (Ops[j] == S) { // Found a duplicate.
650 // Move it to immediately after i'th element.
651 std::swap(Ops[i+1], Ops[j]);
652 ++i; // no need to rescan it.
653 if (i == e-2) return; // Done!
661 //===----------------------------------------------------------------------===//
662 // Simple SCEV method implementations
663 //===----------------------------------------------------------------------===//
665 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
667 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
669 const Type* ResultTy) {
670 // Handle the simplest case efficiently.
672 return SE.getTruncateOrZeroExtend(It, ResultTy);
674 // We are using the following formula for BC(It, K):
676 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
678 // Suppose, W is the bitwidth of the return value. We must be prepared for
679 // overflow. Hence, we must assure that the result of our computation is
680 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
681 // safe in modular arithmetic.
683 // However, this code doesn't use exactly that formula; the formula it uses
684 // is something like the following, where T is the number of factors of 2 in
685 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
688 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
690 // This formula is trivially equivalent to the previous formula. However,
691 // this formula can be implemented much more efficiently. The trick is that
692 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
693 // arithmetic. To do exact division in modular arithmetic, all we have
694 // to do is multiply by the inverse. Therefore, this step can be done at
697 // The next issue is how to safely do the division by 2^T. The way this
698 // is done is by doing the multiplication step at a width of at least W + T
699 // bits. This way, the bottom W+T bits of the product are accurate. Then,
700 // when we perform the division by 2^T (which is equivalent to a right shift
701 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
702 // truncated out after the division by 2^T.
704 // In comparison to just directly using the first formula, this technique
705 // is much more efficient; using the first formula requires W * K bits,
706 // but this formula less than W + K bits. Also, the first formula requires
707 // a division step, whereas this formula only requires multiplies and shifts.
709 // It doesn't matter whether the subtraction step is done in the calculation
710 // width or the input iteration count's width; if the subtraction overflows,
711 // the result must be zero anyway. We prefer here to do it in the width of
712 // the induction variable because it helps a lot for certain cases; CodeGen
713 // isn't smart enough to ignore the overflow, which leads to much less
714 // efficient code if the width of the subtraction is wider than the native
717 // (It's possible to not widen at all by pulling out factors of 2 before
718 // the multiplication; for example, K=2 can be calculated as
719 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
720 // extra arithmetic, so it's not an obvious win, and it gets
721 // much more complicated for K > 3.)
723 // Protection from insane SCEVs; this bound is conservative,
724 // but it probably doesn't matter.
726 return SE.getCouldNotCompute();
728 unsigned W = SE.getTypeSizeInBits(ResultTy);
730 // Calculate K! / 2^T and T; we divide out the factors of two before
731 // multiplying for calculating K! / 2^T to avoid overflow.
732 // Other overflow doesn't matter because we only care about the bottom
733 // W bits of the result.
734 APInt OddFactorial(W, 1);
736 for (unsigned i = 3; i <= K; ++i) {
738 unsigned TwoFactors = Mult.countTrailingZeros();
740 Mult = Mult.lshr(TwoFactors);
741 OddFactorial *= Mult;
744 // We need at least W + T bits for the multiplication step
745 unsigned CalculationBits = W + T;
747 // Calcuate 2^T, at width T+W.
748 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
750 // Calculate the multiplicative inverse of K! / 2^T;
751 // this multiplication factor will perform the exact division by
753 APInt Mod = APInt::getSignedMinValue(W+1);
754 APInt MultiplyFactor = OddFactorial.zext(W+1);
755 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
756 MultiplyFactor = MultiplyFactor.trunc(W);
758 // Calculate the product, at width T+W
759 const IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
761 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
762 for (unsigned i = 1; i != K; ++i) {
763 const SCEV *S = SE.getMinusSCEV(It, SE.getIntegerSCEV(i, It->getType()));
764 Dividend = SE.getMulExpr(Dividend,
765 SE.getTruncateOrZeroExtend(S, CalculationTy));
769 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
771 // Truncate the result, and divide by K! / 2^T.
773 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
774 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
777 /// evaluateAtIteration - Return the value of this chain of recurrences at
778 /// the specified iteration number. We can evaluate this recurrence by
779 /// multiplying each element in the chain by the binomial coefficient
780 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
782 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
784 /// where BC(It, k) stands for binomial coefficient.
786 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
787 ScalarEvolution &SE) const {
788 const SCEV *Result = getStart();
789 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
790 // The computation is correct in the face of overflow provided that the
791 // multiplication is performed _after_ the evaluation of the binomial
793 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
794 if (isa<SCEVCouldNotCompute>(Coeff))
797 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
802 //===----------------------------------------------------------------------===//
803 // SCEV Expression folder implementations
804 //===----------------------------------------------------------------------===//
806 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
808 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
809 "This is not a truncating conversion!");
810 assert(isSCEVable(Ty) &&
811 "This is not a conversion to a SCEVable type!");
812 Ty = getEffectiveSCEVType(Ty);
815 ID.AddInteger(scTruncate);
819 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
821 // Fold if the operand is constant.
822 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
824 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
826 // trunc(trunc(x)) --> trunc(x)
827 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
828 return getTruncateExpr(ST->getOperand(), Ty);
830 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
831 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
832 return getTruncateOrSignExtend(SS->getOperand(), Ty);
834 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
835 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
836 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
838 // If the input value is a chrec scev, truncate the chrec's operands.
839 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
840 SmallVector<const SCEV *, 4> Operands;
841 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
842 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
843 return getAddRecExpr(Operands, AddRec->getLoop());
846 // The cast wasn't folded; create an explicit cast node.
847 // Recompute the insert position, as it may have been invalidated.
848 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
849 SCEV *S = SCEVAllocator.Allocate<SCEVTruncateExpr>();
850 new (S) SCEVTruncateExpr(ID, Op, Ty);
851 UniqueSCEVs.InsertNode(S, IP);
855 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
857 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
858 "This is not an extending conversion!");
859 assert(isSCEVable(Ty) &&
860 "This is not a conversion to a SCEVable type!");
861 Ty = getEffectiveSCEVType(Ty);
863 // Fold if the operand is constant.
864 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) {
865 const Type *IntTy = getEffectiveSCEVType(Ty);
866 Constant *C = ConstantExpr::getZExt(SC->getValue(), IntTy);
867 if (IntTy != Ty) C = ConstantExpr::getIntToPtr(C, Ty);
868 return getConstant(cast<ConstantInt>(C));
871 // zext(zext(x)) --> zext(x)
872 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
873 return getZeroExtendExpr(SZ->getOperand(), Ty);
875 // Before doing any expensive analysis, check to see if we've already
876 // computed a SCEV for this Op and Ty.
878 ID.AddInteger(scZeroExtend);
882 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
884 // If the input value is a chrec scev, and we can prove that the value
885 // did not overflow the old, smaller, value, we can zero extend all of the
886 // operands (often constants). This allows analysis of something like
887 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
888 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
889 if (AR->isAffine()) {
890 const SCEV *Start = AR->getStart();
891 const SCEV *Step = AR->getStepRecurrence(*this);
892 unsigned BitWidth = getTypeSizeInBits(AR->getType());
893 const Loop *L = AR->getLoop();
895 // If we have special knowledge that this addrec won't overflow,
896 // we don't need to do any further analysis.
897 if (AR->hasNoUnsignedWrap())
898 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
899 getZeroExtendExpr(Step, Ty),
902 // Check whether the backedge-taken count is SCEVCouldNotCompute.
903 // Note that this serves two purposes: It filters out loops that are
904 // simply not analyzable, and it covers the case where this code is
905 // being called from within backedge-taken count analysis, such that
906 // attempting to ask for the backedge-taken count would likely result
907 // in infinite recursion. In the later case, the analysis code will
908 // cope with a conservative value, and it will take care to purge
909 // that value once it has finished.
910 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
911 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
912 // Manually compute the final value for AR, checking for
915 // Check whether the backedge-taken count can be losslessly casted to
916 // the addrec's type. The count is always unsigned.
917 const SCEV *CastedMaxBECount =
918 getTruncateOrZeroExtend(MaxBECount, Start->getType());
919 const SCEV *RecastedMaxBECount =
920 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
921 if (MaxBECount == RecastedMaxBECount) {
922 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
923 // Check whether Start+Step*MaxBECount has no unsigned overflow.
925 getMulExpr(CastedMaxBECount,
926 getTruncateOrZeroExtend(Step, Start->getType()));
927 const SCEV *Add = getAddExpr(Start, ZMul);
928 const SCEV *OperandExtendedAdd =
929 getAddExpr(getZeroExtendExpr(Start, WideTy),
930 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
931 getZeroExtendExpr(Step, WideTy)));
932 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
933 // Return the expression with the addrec on the outside.
934 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
935 getZeroExtendExpr(Step, Ty),
938 // Similar to above, only this time treat the step value as signed.
939 // This covers loops that count down.
941 getMulExpr(CastedMaxBECount,
942 getTruncateOrSignExtend(Step, Start->getType()));
943 Add = getAddExpr(Start, SMul);
945 getAddExpr(getZeroExtendExpr(Start, WideTy),
946 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
947 getSignExtendExpr(Step, WideTy)));
948 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
949 // Return the expression with the addrec on the outside.
950 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
951 getSignExtendExpr(Step, Ty),
955 // If the backedge is guarded by a comparison with the pre-inc value
956 // the addrec is safe. Also, if the entry is guarded by a comparison
957 // with the start value and the backedge is guarded by a comparison
958 // with the post-inc value, the addrec is safe.
959 if (isKnownPositive(Step)) {
960 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
961 getUnsignedRange(Step).getUnsignedMax());
962 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
963 (isLoopGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
964 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
965 AR->getPostIncExpr(*this), N)))
966 // Return the expression with the addrec on the outside.
967 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
968 getZeroExtendExpr(Step, Ty),
970 } else if (isKnownNegative(Step)) {
971 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
972 getSignedRange(Step).getSignedMin());
973 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) &&
974 (isLoopGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) ||
975 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
976 AR->getPostIncExpr(*this), N)))
977 // Return the expression with the addrec on the outside.
978 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
979 getSignExtendExpr(Step, Ty),
985 // The cast wasn't folded; create an explicit cast node.
986 // Recompute the insert position, as it may have been invalidated.
987 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
988 SCEV *S = SCEVAllocator.Allocate<SCEVZeroExtendExpr>();
989 new (S) SCEVZeroExtendExpr(ID, Op, Ty);
990 UniqueSCEVs.InsertNode(S, IP);
994 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
996 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
997 "This is not an extending conversion!");
998 assert(isSCEVable(Ty) &&
999 "This is not a conversion to a SCEVable type!");
1000 Ty = getEffectiveSCEVType(Ty);
1002 // Fold if the operand is constant.
1003 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) {
1004 const Type *IntTy = getEffectiveSCEVType(Ty);
1005 Constant *C = ConstantExpr::getSExt(SC->getValue(), IntTy);
1006 if (IntTy != Ty) C = ConstantExpr::getIntToPtr(C, Ty);
1007 return getConstant(cast<ConstantInt>(C));
1010 // sext(sext(x)) --> sext(x)
1011 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1012 return getSignExtendExpr(SS->getOperand(), Ty);
1014 // Before doing any expensive analysis, check to see if we've already
1015 // computed a SCEV for this Op and Ty.
1016 FoldingSetNodeID ID;
1017 ID.AddInteger(scSignExtend);
1021 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1023 // If the input value is a chrec scev, and we can prove that the value
1024 // did not overflow the old, smaller, value, we can sign extend all of the
1025 // operands (often constants). This allows analysis of something like
1026 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1027 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1028 if (AR->isAffine()) {
1029 const SCEV *Start = AR->getStart();
1030 const SCEV *Step = AR->getStepRecurrence(*this);
1031 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1032 const Loop *L = AR->getLoop();
1034 // If we have special knowledge that this addrec won't overflow,
1035 // we don't need to do any further analysis.
1036 if (AR->hasNoSignedWrap())
1037 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1038 getSignExtendExpr(Step, Ty),
1041 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1042 // Note that this serves two purposes: It filters out loops that are
1043 // simply not analyzable, and it covers the case where this code is
1044 // being called from within backedge-taken count analysis, such that
1045 // attempting to ask for the backedge-taken count would likely result
1046 // in infinite recursion. In the later case, the analysis code will
1047 // cope with a conservative value, and it will take care to purge
1048 // that value once it has finished.
1049 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1050 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1051 // Manually compute the final value for AR, checking for
1054 // Check whether the backedge-taken count can be losslessly casted to
1055 // the addrec's type. The count is always unsigned.
1056 const SCEV *CastedMaxBECount =
1057 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1058 const SCEV *RecastedMaxBECount =
1059 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1060 if (MaxBECount == RecastedMaxBECount) {
1061 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1062 // Check whether Start+Step*MaxBECount has no signed overflow.
1064 getMulExpr(CastedMaxBECount,
1065 getTruncateOrSignExtend(Step, Start->getType()));
1066 const SCEV *Add = getAddExpr(Start, SMul);
1067 const SCEV *OperandExtendedAdd =
1068 getAddExpr(getSignExtendExpr(Start, WideTy),
1069 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1070 getSignExtendExpr(Step, WideTy)));
1071 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1072 // Return the expression with the addrec on the outside.
1073 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1074 getSignExtendExpr(Step, Ty),
1077 // Similar to above, only this time treat the step value as unsigned.
1078 // This covers loops that count up with an unsigned step.
1080 getMulExpr(CastedMaxBECount,
1081 getTruncateOrZeroExtend(Step, Start->getType()));
1082 Add = getAddExpr(Start, UMul);
1083 OperandExtendedAdd =
1084 getAddExpr(getSignExtendExpr(Start, WideTy),
1085 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1086 getZeroExtendExpr(Step, WideTy)));
1087 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1088 // Return the expression with the addrec on the outside.
1089 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1090 getZeroExtendExpr(Step, Ty),
1094 // If the backedge is guarded by a comparison with the pre-inc value
1095 // the addrec is safe. Also, if the entry is guarded by a comparison
1096 // with the start value and the backedge is guarded by a comparison
1097 // with the post-inc value, the addrec is safe.
1098 if (isKnownPositive(Step)) {
1099 const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
1100 getSignedRange(Step).getSignedMax());
1101 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
1102 (isLoopGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
1103 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
1104 AR->getPostIncExpr(*this), N)))
1105 // Return the expression with the addrec on the outside.
1106 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1107 getSignExtendExpr(Step, Ty),
1109 } else if (isKnownNegative(Step)) {
1110 const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
1111 getSignedRange(Step).getSignedMin());
1112 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
1113 (isLoopGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
1114 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
1115 AR->getPostIncExpr(*this), N)))
1116 // Return the expression with the addrec on the outside.
1117 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1118 getSignExtendExpr(Step, Ty),
1124 // The cast wasn't folded; create an explicit cast node.
1125 // Recompute the insert position, as it may have been invalidated.
1126 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1127 SCEV *S = SCEVAllocator.Allocate<SCEVSignExtendExpr>();
1128 new (S) SCEVSignExtendExpr(ID, Op, Ty);
1129 UniqueSCEVs.InsertNode(S, IP);
1133 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1134 /// unspecified bits out to the given type.
1136 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1138 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1139 "This is not an extending conversion!");
1140 assert(isSCEVable(Ty) &&
1141 "This is not a conversion to a SCEVable type!");
1142 Ty = getEffectiveSCEVType(Ty);
1144 // Sign-extend negative constants.
1145 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1146 if (SC->getValue()->getValue().isNegative())
1147 return getSignExtendExpr(Op, Ty);
1149 // Peel off a truncate cast.
1150 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1151 const SCEV *NewOp = T->getOperand();
1152 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1153 return getAnyExtendExpr(NewOp, Ty);
1154 return getTruncateOrNoop(NewOp, Ty);
1157 // Next try a zext cast. If the cast is folded, use it.
1158 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1159 if (!isa<SCEVZeroExtendExpr>(ZExt))
1162 // Next try a sext cast. If the cast is folded, use it.
1163 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1164 if (!isa<SCEVSignExtendExpr>(SExt))
1167 // Force the cast to be folded into the operands of an addrec.
1168 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1169 SmallVector<const SCEV *, 4> Ops;
1170 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1172 Ops.push_back(getAnyExtendExpr(*I, Ty));
1173 return getAddRecExpr(Ops, AR->getLoop());
1176 // If the expression is obviously signed, use the sext cast value.
1177 if (isa<SCEVSMaxExpr>(Op))
1180 // Absent any other information, use the zext cast value.
1184 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1185 /// a list of operands to be added under the given scale, update the given
1186 /// map. This is a helper function for getAddRecExpr. As an example of
1187 /// what it does, given a sequence of operands that would form an add
1188 /// expression like this:
1190 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1192 /// where A and B are constants, update the map with these values:
1194 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1196 /// and add 13 + A*B*29 to AccumulatedConstant.
1197 /// This will allow getAddRecExpr to produce this:
1199 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1201 /// This form often exposes folding opportunities that are hidden in
1202 /// the original operand list.
1204 /// Return true iff it appears that any interesting folding opportunities
1205 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1206 /// the common case where no interesting opportunities are present, and
1207 /// is also used as a check to avoid infinite recursion.
1210 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1211 SmallVector<const SCEV *, 8> &NewOps,
1212 APInt &AccumulatedConstant,
1213 const SmallVectorImpl<const SCEV *> &Ops,
1215 ScalarEvolution &SE) {
1216 bool Interesting = false;
1218 // Iterate over the add operands.
1219 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1220 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1221 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1223 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1224 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1225 // A multiplication of a constant with another add; recurse.
1227 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1228 cast<SCEVAddExpr>(Mul->getOperand(1))
1232 // A multiplication of a constant with some other value. Update
1234 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1235 const SCEV *Key = SE.getMulExpr(MulOps);
1236 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1237 M.insert(std::make_pair(Key, NewScale));
1239 NewOps.push_back(Pair.first->first);
1241 Pair.first->second += NewScale;
1242 // The map already had an entry for this value, which may indicate
1243 // a folding opportunity.
1247 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1248 // Pull a buried constant out to the outside.
1249 if (Scale != 1 || AccumulatedConstant != 0 || C->isZero())
1251 AccumulatedConstant += Scale * C->getValue()->getValue();
1253 // An ordinary operand. Update the map.
1254 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1255 M.insert(std::make_pair(Ops[i], Scale));
1257 NewOps.push_back(Pair.first->first);
1259 Pair.first->second += Scale;
1260 // The map already had an entry for this value, which may indicate
1261 // a folding opportunity.
1271 struct APIntCompare {
1272 bool operator()(const APInt &LHS, const APInt &RHS) const {
1273 return LHS.ult(RHS);
1278 /// getAddExpr - Get a canonical add expression, or something simpler if
1280 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1281 bool HasNUW, bool HasNSW) {
1282 assert(!Ops.empty() && "Cannot get empty add!");
1283 if (Ops.size() == 1) return Ops[0];
1285 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1286 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
1287 getEffectiveSCEVType(Ops[0]->getType()) &&
1288 "SCEVAddExpr operand types don't match!");
1291 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1292 if (!HasNUW && HasNSW) {
1294 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1295 if (!isKnownNonNegative(Ops[i])) {
1299 if (All) HasNUW = true;
1302 // Sort by complexity, this groups all similar expression types together.
1303 GroupByComplexity(Ops, LI);
1305 // If there are any constants, fold them together.
1307 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1309 assert(Idx < Ops.size());
1310 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1311 // We found two constants, fold them together!
1312 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1313 RHSC->getValue()->getValue());
1314 if (Ops.size() == 2) return Ops[0];
1315 Ops.erase(Ops.begin()+1); // Erase the folded element
1316 LHSC = cast<SCEVConstant>(Ops[0]);
1319 // If we are left with a constant zero being added, strip it off.
1320 if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1321 Ops.erase(Ops.begin());
1326 if (Ops.size() == 1) return Ops[0];
1328 // Okay, check to see if the same value occurs in the operand list twice. If
1329 // so, merge them together into an multiply expression. Since we sorted the
1330 // list, these values are required to be adjacent.
1331 const Type *Ty = Ops[0]->getType();
1332 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
1333 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1334 // Found a match, merge the two values into a multiply, and add any
1335 // remaining values to the result.
1336 const SCEV *Two = getIntegerSCEV(2, Ty);
1337 const SCEV *Mul = getMulExpr(Ops[i], Two);
1338 if (Ops.size() == 2)
1340 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1342 return getAddExpr(Ops, HasNUW, HasNSW);
1345 // Check for truncates. If all the operands are truncated from the same
1346 // type, see if factoring out the truncate would permit the result to be
1347 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1348 // if the contents of the resulting outer trunc fold to something simple.
1349 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1350 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1351 const Type *DstType = Trunc->getType();
1352 const Type *SrcType = Trunc->getOperand()->getType();
1353 SmallVector<const SCEV *, 8> LargeOps;
1355 // Check all the operands to see if they can be represented in the
1356 // source type of the truncate.
1357 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1358 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1359 if (T->getOperand()->getType() != SrcType) {
1363 LargeOps.push_back(T->getOperand());
1364 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1365 // This could be either sign or zero extension, but sign extension
1366 // is much more likely to be foldable here.
1367 LargeOps.push_back(getSignExtendExpr(C, SrcType));
1368 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1369 SmallVector<const SCEV *, 8> LargeMulOps;
1370 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1371 if (const SCEVTruncateExpr *T =
1372 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1373 if (T->getOperand()->getType() != SrcType) {
1377 LargeMulOps.push_back(T->getOperand());
1378 } else if (const SCEVConstant *C =
1379 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1380 // This could be either sign or zero extension, but sign extension
1381 // is much more likely to be foldable here.
1382 LargeMulOps.push_back(getSignExtendExpr(C, SrcType));
1389 LargeOps.push_back(getMulExpr(LargeMulOps));
1396 // Evaluate the expression in the larger type.
1397 const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
1398 // If it folds to something simple, use it. Otherwise, don't.
1399 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1400 return getTruncateExpr(Fold, DstType);
1404 // Skip past any other cast SCEVs.
1405 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1408 // If there are add operands they would be next.
1409 if (Idx < Ops.size()) {
1410 bool DeletedAdd = false;
1411 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1412 // If we have an add, expand the add operands onto the end of the operands
1414 Ops.insert(Ops.end(), Add->op_begin(), Add->op_end());
1415 Ops.erase(Ops.begin()+Idx);
1419 // If we deleted at least one add, we added operands to the end of the list,
1420 // and they are not necessarily sorted. Recurse to resort and resimplify
1421 // any operands we just aquired.
1423 return getAddExpr(Ops);
1426 // Skip over the add expression until we get to a multiply.
1427 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1430 // Check to see if there are any folding opportunities present with
1431 // operands multiplied by constant values.
1432 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1433 uint64_t BitWidth = getTypeSizeInBits(Ty);
1434 DenseMap<const SCEV *, APInt> M;
1435 SmallVector<const SCEV *, 8> NewOps;
1436 APInt AccumulatedConstant(BitWidth, 0);
1437 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1438 Ops, APInt(BitWidth, 1), *this)) {
1439 // Some interesting folding opportunity is present, so its worthwhile to
1440 // re-generate the operands list. Group the operands by constant scale,
1441 // to avoid multiplying by the same constant scale multiple times.
1442 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1443 for (SmallVector<const SCEV *, 8>::iterator I = NewOps.begin(),
1444 E = NewOps.end(); I != E; ++I)
1445 MulOpLists[M.find(*I)->second].push_back(*I);
1446 // Re-generate the operands list.
1448 if (AccumulatedConstant != 0)
1449 Ops.push_back(getConstant(AccumulatedConstant));
1450 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1451 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1453 Ops.push_back(getMulExpr(getConstant(I->first),
1454 getAddExpr(I->second)));
1456 return getIntegerSCEV(0, Ty);
1457 if (Ops.size() == 1)
1459 return getAddExpr(Ops);
1463 // If we are adding something to a multiply expression, make sure the
1464 // something is not already an operand of the multiply. If so, merge it into
1466 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1467 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1468 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1469 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1470 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1471 if (MulOpSCEV == Ops[AddOp] && !isa<SCEVConstant>(Ops[AddOp])) {
1472 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1473 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1474 if (Mul->getNumOperands() != 2) {
1475 // If the multiply has more than two operands, we must get the
1477 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(), Mul->op_end());
1478 MulOps.erase(MulOps.begin()+MulOp);
1479 InnerMul = getMulExpr(MulOps);
1481 const SCEV *One = getIntegerSCEV(1, Ty);
1482 const SCEV *AddOne = getAddExpr(InnerMul, One);
1483 const SCEV *OuterMul = getMulExpr(AddOne, Ops[AddOp]);
1484 if (Ops.size() == 2) return OuterMul;
1486 Ops.erase(Ops.begin()+AddOp);
1487 Ops.erase(Ops.begin()+Idx-1);
1489 Ops.erase(Ops.begin()+Idx);
1490 Ops.erase(Ops.begin()+AddOp-1);
1492 Ops.push_back(OuterMul);
1493 return getAddExpr(Ops);
1496 // Check this multiply against other multiplies being added together.
1497 for (unsigned OtherMulIdx = Idx+1;
1498 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1500 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1501 // If MulOp occurs in OtherMul, we can fold the two multiplies
1503 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1504 OMulOp != e; ++OMulOp)
1505 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1506 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1507 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1508 if (Mul->getNumOperands() != 2) {
1509 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1511 MulOps.erase(MulOps.begin()+MulOp);
1512 InnerMul1 = getMulExpr(MulOps);
1514 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1515 if (OtherMul->getNumOperands() != 2) {
1516 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1517 OtherMul->op_end());
1518 MulOps.erase(MulOps.begin()+OMulOp);
1519 InnerMul2 = getMulExpr(MulOps);
1521 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1522 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1523 if (Ops.size() == 2) return OuterMul;
1524 Ops.erase(Ops.begin()+Idx);
1525 Ops.erase(Ops.begin()+OtherMulIdx-1);
1526 Ops.push_back(OuterMul);
1527 return getAddExpr(Ops);
1533 // If there are any add recurrences in the operands list, see if any other
1534 // added values are loop invariant. If so, we can fold them into the
1536 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1539 // Scan over all recurrences, trying to fold loop invariants into them.
1540 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1541 // Scan all of the other operands to this add and add them to the vector if
1542 // they are loop invariant w.r.t. the recurrence.
1543 SmallVector<const SCEV *, 8> LIOps;
1544 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1545 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1546 if (Ops[i]->isLoopInvariant(AddRec->getLoop())) {
1547 LIOps.push_back(Ops[i]);
1548 Ops.erase(Ops.begin()+i);
1552 // If we found some loop invariants, fold them into the recurrence.
1553 if (!LIOps.empty()) {
1554 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1555 LIOps.push_back(AddRec->getStart());
1557 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1559 AddRecOps[0] = getAddExpr(LIOps);
1561 // It's tempting to propagate NUW/NSW flags here, but nuw/nsw addition
1562 // is not associative so this isn't necessarily safe.
1563 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRec->getLoop());
1565 // If all of the other operands were loop invariant, we are done.
1566 if (Ops.size() == 1) return NewRec;
1568 // Otherwise, add the folded AddRec by the non-liv parts.
1569 for (unsigned i = 0;; ++i)
1570 if (Ops[i] == AddRec) {
1574 return getAddExpr(Ops);
1577 // Okay, if there weren't any loop invariants to be folded, check to see if
1578 // there are multiple AddRec's with the same loop induction variable being
1579 // added together. If so, we can fold them.
1580 for (unsigned OtherIdx = Idx+1;
1581 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
1582 if (OtherIdx != Idx) {
1583 const SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
1584 if (AddRec->getLoop() == OtherAddRec->getLoop()) {
1585 // Other + {A,+,B} + {C,+,D} --> Other + {A+C,+,B+D}
1586 SmallVector<const SCEV *, 4> NewOps(AddRec->op_begin(),
1588 for (unsigned i = 0, e = OtherAddRec->getNumOperands(); i != e; ++i) {
1589 if (i >= NewOps.size()) {
1590 NewOps.insert(NewOps.end(), OtherAddRec->op_begin()+i,
1591 OtherAddRec->op_end());
1594 NewOps[i] = getAddExpr(NewOps[i], OtherAddRec->getOperand(i));
1596 const SCEV *NewAddRec = getAddRecExpr(NewOps, AddRec->getLoop());
1598 if (Ops.size() == 2) return NewAddRec;
1600 Ops.erase(Ops.begin()+Idx);
1601 Ops.erase(Ops.begin()+OtherIdx-1);
1602 Ops.push_back(NewAddRec);
1603 return getAddExpr(Ops);
1607 // Otherwise couldn't fold anything into this recurrence. Move onto the
1611 // Okay, it looks like we really DO need an add expr. Check to see if we
1612 // already have one, otherwise create a new one.
1613 FoldingSetNodeID ID;
1614 ID.AddInteger(scAddExpr);
1615 ID.AddInteger(Ops.size());
1616 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1617 ID.AddPointer(Ops[i]);
1620 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1622 S = SCEVAllocator.Allocate<SCEVAddExpr>();
1623 new (S) SCEVAddExpr(ID, Ops);
1624 UniqueSCEVs.InsertNode(S, IP);
1626 if (HasNUW) S->setHasNoUnsignedWrap(true);
1627 if (HasNSW) S->setHasNoSignedWrap(true);
1631 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1633 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1634 bool HasNUW, bool HasNSW) {
1635 assert(!Ops.empty() && "Cannot get empty mul!");
1636 if (Ops.size() == 1) return Ops[0];
1638 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1639 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
1640 getEffectiveSCEVType(Ops[0]->getType()) &&
1641 "SCEVMulExpr operand types don't match!");
1644 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1645 if (!HasNUW && HasNSW) {
1647 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1648 if (!isKnownNonNegative(Ops[i])) {
1652 if (All) HasNUW = true;
1655 // Sort by complexity, this groups all similar expression types together.
1656 GroupByComplexity(Ops, LI);
1658 // If there are any constants, fold them together.
1660 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1662 // C1*(C2+V) -> C1*C2 + C1*V
1663 if (Ops.size() == 2)
1664 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1665 if (Add->getNumOperands() == 2 &&
1666 isa<SCEVConstant>(Add->getOperand(0)))
1667 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1668 getMulExpr(LHSC, Add->getOperand(1)));
1671 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1672 // We found two constants, fold them together!
1673 ConstantInt *Fold = ConstantInt::get(getContext(),
1674 LHSC->getValue()->getValue() *
1675 RHSC->getValue()->getValue());
1676 Ops[0] = getConstant(Fold);
1677 Ops.erase(Ops.begin()+1); // Erase the folded element
1678 if (Ops.size() == 1) return Ops[0];
1679 LHSC = cast<SCEVConstant>(Ops[0]);
1682 // If we are left with a constant one being multiplied, strip it off.
1683 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1684 Ops.erase(Ops.begin());
1686 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1687 // If we have a multiply of zero, it will always be zero.
1689 } else if (Ops[0]->isAllOnesValue()) {
1690 // If we have a mul by -1 of an add, try distributing the -1 among the
1692 if (Ops.size() == 2)
1693 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1694 SmallVector<const SCEV *, 4> NewOps;
1695 bool AnyFolded = false;
1696 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1698 const SCEV *Mul = getMulExpr(Ops[0], *I);
1699 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1700 NewOps.push_back(Mul);
1703 return getAddExpr(NewOps);
1708 // Skip over the add expression until we get to a multiply.
1709 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1712 if (Ops.size() == 1)
1715 // If there are mul operands inline them all into this expression.
1716 if (Idx < Ops.size()) {
1717 bool DeletedMul = false;
1718 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1719 // If we have an mul, expand the mul operands onto the end of the operands
1721 Ops.insert(Ops.end(), Mul->op_begin(), Mul->op_end());
1722 Ops.erase(Ops.begin()+Idx);
1726 // If we deleted at least one mul, we added operands to the end of the list,
1727 // and they are not necessarily sorted. Recurse to resort and resimplify
1728 // any operands we just aquired.
1730 return getMulExpr(Ops);
1733 // If there are any add recurrences in the operands list, see if any other
1734 // added values are loop invariant. If so, we can fold them into the
1736 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1739 // Scan over all recurrences, trying to fold loop invariants into them.
1740 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1741 // Scan all of the other operands to this mul and add them to the vector if
1742 // they are loop invariant w.r.t. the recurrence.
1743 SmallVector<const SCEV *, 8> LIOps;
1744 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1745 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1746 if (Ops[i]->isLoopInvariant(AddRec->getLoop())) {
1747 LIOps.push_back(Ops[i]);
1748 Ops.erase(Ops.begin()+i);
1752 // If we found some loop invariants, fold them into the recurrence.
1753 if (!LIOps.empty()) {
1754 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1755 SmallVector<const SCEV *, 4> NewOps;
1756 NewOps.reserve(AddRec->getNumOperands());
1757 if (LIOps.size() == 1) {
1758 const SCEV *Scale = LIOps[0];
1759 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1760 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1762 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
1763 SmallVector<const SCEV *, 4> MulOps(LIOps.begin(), LIOps.end());
1764 MulOps.push_back(AddRec->getOperand(i));
1765 NewOps.push_back(getMulExpr(MulOps));
1769 // It's tempting to propagate the NSW flag here, but nsw multiplication
1770 // is not associative so this isn't necessarily safe.
1771 const SCEV *NewRec = getAddRecExpr(NewOps, AddRec->getLoop(),
1772 HasNUW && AddRec->hasNoUnsignedWrap(),
1775 // If all of the other operands were loop invariant, we are done.
1776 if (Ops.size() == 1) return NewRec;
1778 // Otherwise, multiply the folded AddRec by the non-liv parts.
1779 for (unsigned i = 0;; ++i)
1780 if (Ops[i] == AddRec) {
1784 return getMulExpr(Ops);
1787 // Okay, if there weren't any loop invariants to be folded, check to see if
1788 // there are multiple AddRec's with the same loop induction variable being
1789 // multiplied together. If so, we can fold them.
1790 for (unsigned OtherIdx = Idx+1;
1791 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
1792 if (OtherIdx != Idx) {
1793 const SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
1794 if (AddRec->getLoop() == OtherAddRec->getLoop()) {
1795 // F * G --> {A,+,B} * {C,+,D} --> {A*C,+,F*D + G*B + B*D}
1796 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1797 const SCEV *NewStart = getMulExpr(F->getStart(),
1799 const SCEV *B = F->getStepRecurrence(*this);
1800 const SCEV *D = G->getStepRecurrence(*this);
1801 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1804 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1806 if (Ops.size() == 2) return NewAddRec;
1808 Ops.erase(Ops.begin()+Idx);
1809 Ops.erase(Ops.begin()+OtherIdx-1);
1810 Ops.push_back(NewAddRec);
1811 return getMulExpr(Ops);
1815 // Otherwise couldn't fold anything into this recurrence. Move onto the
1819 // Okay, it looks like we really DO need an mul expr. Check to see if we
1820 // already have one, otherwise create a new one.
1821 FoldingSetNodeID ID;
1822 ID.AddInteger(scMulExpr);
1823 ID.AddInteger(Ops.size());
1824 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1825 ID.AddPointer(Ops[i]);
1828 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1830 S = SCEVAllocator.Allocate<SCEVMulExpr>();
1831 new (S) SCEVMulExpr(ID, Ops);
1832 UniqueSCEVs.InsertNode(S, IP);
1834 if (HasNUW) S->setHasNoUnsignedWrap(true);
1835 if (HasNSW) S->setHasNoSignedWrap(true);
1839 /// getUDivExpr - Get a canonical unsigned division expression, or something
1840 /// simpler if possible.
1841 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
1843 assert(getEffectiveSCEVType(LHS->getType()) ==
1844 getEffectiveSCEVType(RHS->getType()) &&
1845 "SCEVUDivExpr operand types don't match!");
1847 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
1848 if (RHSC->getValue()->equalsInt(1))
1849 return LHS; // X udiv 1 --> x
1851 return getIntegerSCEV(0, LHS->getType()); // value is undefined
1853 // Determine if the division can be folded into the operands of
1855 // TODO: Generalize this to non-constants by using known-bits information.
1856 const Type *Ty = LHS->getType();
1857 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
1858 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ;
1859 // For non-power-of-two values, effectively round the value up to the
1860 // nearest power of two.
1861 if (!RHSC->getValue()->getValue().isPowerOf2())
1863 const IntegerType *ExtTy =
1864 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
1865 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
1866 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
1867 if (const SCEVConstant *Step =
1868 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
1869 if (!Step->getValue()->getValue()
1870 .urem(RHSC->getValue()->getValue()) &&
1871 getZeroExtendExpr(AR, ExtTy) ==
1872 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
1873 getZeroExtendExpr(Step, ExtTy),
1875 SmallVector<const SCEV *, 4> Operands;
1876 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
1877 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
1878 return getAddRecExpr(Operands, AR->getLoop());
1880 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
1881 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
1882 SmallVector<const SCEV *, 4> Operands;
1883 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
1884 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
1885 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
1886 // Find an operand that's safely divisible.
1887 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
1888 const SCEV *Op = M->getOperand(i);
1889 const SCEV *Div = getUDivExpr(Op, RHSC);
1890 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
1891 const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands();
1892 Operands = SmallVector<const SCEV *, 4>(MOperands.begin(),
1895 return getMulExpr(Operands);
1899 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
1900 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
1901 SmallVector<const SCEV *, 4> Operands;
1902 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
1903 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
1904 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
1906 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
1907 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
1908 if (isa<SCEVUDivExpr>(Op) || getMulExpr(Op, RHS) != A->getOperand(i))
1910 Operands.push_back(Op);
1912 if (Operands.size() == A->getNumOperands())
1913 return getAddExpr(Operands);
1917 // Fold if both operands are constant.
1918 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
1919 Constant *LHSCV = LHSC->getValue();
1920 Constant *RHSCV = RHSC->getValue();
1921 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
1926 FoldingSetNodeID ID;
1927 ID.AddInteger(scUDivExpr);
1931 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1932 SCEV *S = SCEVAllocator.Allocate<SCEVUDivExpr>();
1933 new (S) SCEVUDivExpr(ID, LHS, RHS);
1934 UniqueSCEVs.InsertNode(S, IP);
1939 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
1940 /// Simplify the expression as much as possible.
1941 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
1942 const SCEV *Step, const Loop *L,
1943 bool HasNUW, bool HasNSW) {
1944 SmallVector<const SCEV *, 4> Operands;
1945 Operands.push_back(Start);
1946 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
1947 if (StepChrec->getLoop() == L) {
1948 Operands.insert(Operands.end(), StepChrec->op_begin(),
1949 StepChrec->op_end());
1950 return getAddRecExpr(Operands, L);
1953 Operands.push_back(Step);
1954 return getAddRecExpr(Operands, L, HasNUW, HasNSW);
1957 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
1958 /// Simplify the expression as much as possible.
1960 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
1962 bool HasNUW, bool HasNSW) {
1963 if (Operands.size() == 1) return Operands[0];
1965 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
1966 assert(getEffectiveSCEVType(Operands[i]->getType()) ==
1967 getEffectiveSCEVType(Operands[0]->getType()) &&
1968 "SCEVAddRecExpr operand types don't match!");
1971 if (Operands.back()->isZero()) {
1972 Operands.pop_back();
1973 return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0} --> X
1976 // It's tempting to want to call getMaxBackedgeTakenCount count here and
1977 // use that information to infer NUW and NSW flags. However, computing a
1978 // BE count requires calling getAddRecExpr, so we may not yet have a
1979 // meaningful BE count at this point (and if we don't, we'd be stuck
1980 // with a SCEVCouldNotCompute as the cached BE count).
1982 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1983 if (!HasNUW && HasNSW) {
1985 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
1986 if (!isKnownNonNegative(Operands[i])) {
1990 if (All) HasNUW = true;
1993 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
1994 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
1995 const Loop *NestedLoop = NestedAR->getLoop();
1996 if (L->contains(NestedLoop->getHeader()) ?
1997 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
1998 (!NestedLoop->contains(L->getHeader()) &&
1999 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2000 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2001 NestedAR->op_end());
2002 Operands[0] = NestedAR->getStart();
2003 // AddRecs require their operands be loop-invariant with respect to their
2004 // loops. Don't perform this transformation if it would break this
2006 bool AllInvariant = true;
2007 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2008 if (!Operands[i]->isLoopInvariant(L)) {
2009 AllInvariant = false;
2013 NestedOperands[0] = getAddRecExpr(Operands, L);
2014 AllInvariant = true;
2015 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2016 if (!NestedOperands[i]->isLoopInvariant(NestedLoop)) {
2017 AllInvariant = false;
2021 // Ok, both add recurrences are valid after the transformation.
2022 return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
2024 // Reset Operands to its original state.
2025 Operands[0] = NestedAR;
2029 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2030 // already have one, otherwise create a new one.
2031 FoldingSetNodeID ID;
2032 ID.AddInteger(scAddRecExpr);
2033 ID.AddInteger(Operands.size());
2034 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2035 ID.AddPointer(Operands[i]);
2039 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2041 S = SCEVAllocator.Allocate<SCEVAddRecExpr>();
2042 new (S) SCEVAddRecExpr(ID, Operands, L);
2043 UniqueSCEVs.InsertNode(S, IP);
2045 if (HasNUW) S->setHasNoUnsignedWrap(true);
2046 if (HasNSW) S->setHasNoSignedWrap(true);
2050 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2052 SmallVector<const SCEV *, 2> Ops;
2055 return getSMaxExpr(Ops);
2059 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2060 assert(!Ops.empty() && "Cannot get empty smax!");
2061 if (Ops.size() == 1) return Ops[0];
2063 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2064 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
2065 getEffectiveSCEVType(Ops[0]->getType()) &&
2066 "SCEVSMaxExpr operand types don't match!");
2069 // Sort by complexity, this groups all similar expression types together.
2070 GroupByComplexity(Ops, LI);
2072 // If there are any constants, fold them together.
2074 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2076 assert(Idx < Ops.size());
2077 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2078 // We found two constants, fold them together!
2079 ConstantInt *Fold = ConstantInt::get(getContext(),
2080 APIntOps::smax(LHSC->getValue()->getValue(),
2081 RHSC->getValue()->getValue()));
2082 Ops[0] = getConstant(Fold);
2083 Ops.erase(Ops.begin()+1); // Erase the folded element
2084 if (Ops.size() == 1) return Ops[0];
2085 LHSC = cast<SCEVConstant>(Ops[0]);
2088 // If we are left with a constant minimum-int, strip it off.
2089 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2090 Ops.erase(Ops.begin());
2092 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2093 // If we have an smax with a constant maximum-int, it will always be
2099 if (Ops.size() == 1) return Ops[0];
2101 // Find the first SMax
2102 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2105 // Check to see if one of the operands is an SMax. If so, expand its operands
2106 // onto our operand list, and recurse to simplify.
2107 if (Idx < Ops.size()) {
2108 bool DeletedSMax = false;
2109 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2110 Ops.insert(Ops.end(), SMax->op_begin(), SMax->op_end());
2111 Ops.erase(Ops.begin()+Idx);
2116 return getSMaxExpr(Ops);
2119 // Okay, check to see if the same value occurs in the operand list twice. If
2120 // so, delete one. Since we sorted the list, these values are required to
2122 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2123 if (Ops[i] == Ops[i+1]) { // X smax Y smax Y --> X smax Y
2124 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2128 if (Ops.size() == 1) return Ops[0];
2130 assert(!Ops.empty() && "Reduced smax down to nothing!");
2132 // Okay, it looks like we really DO need an smax expr. Check to see if we
2133 // already have one, otherwise create a new one.
2134 FoldingSetNodeID ID;
2135 ID.AddInteger(scSMaxExpr);
2136 ID.AddInteger(Ops.size());
2137 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2138 ID.AddPointer(Ops[i]);
2140 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2141 SCEV *S = SCEVAllocator.Allocate<SCEVSMaxExpr>();
2142 new (S) SCEVSMaxExpr(ID, Ops);
2143 UniqueSCEVs.InsertNode(S, IP);
2147 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2149 SmallVector<const SCEV *, 2> Ops;
2152 return getUMaxExpr(Ops);
2156 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2157 assert(!Ops.empty() && "Cannot get empty umax!");
2158 if (Ops.size() == 1) return Ops[0];
2160 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2161 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
2162 getEffectiveSCEVType(Ops[0]->getType()) &&
2163 "SCEVUMaxExpr operand types don't match!");
2166 // Sort by complexity, this groups all similar expression types together.
2167 GroupByComplexity(Ops, LI);
2169 // If there are any constants, fold them together.
2171 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2173 assert(Idx < Ops.size());
2174 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2175 // We found two constants, fold them together!
2176 ConstantInt *Fold = ConstantInt::get(getContext(),
2177 APIntOps::umax(LHSC->getValue()->getValue(),
2178 RHSC->getValue()->getValue()));
2179 Ops[0] = getConstant(Fold);
2180 Ops.erase(Ops.begin()+1); // Erase the folded element
2181 if (Ops.size() == 1) return Ops[0];
2182 LHSC = cast<SCEVConstant>(Ops[0]);
2185 // If we are left with a constant minimum-int, strip it off.
2186 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2187 Ops.erase(Ops.begin());
2189 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2190 // If we have an umax with a constant maximum-int, it will always be
2196 if (Ops.size() == 1) return Ops[0];
2198 // Find the first UMax
2199 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2202 // Check to see if one of the operands is a UMax. If so, expand its operands
2203 // onto our operand list, and recurse to simplify.
2204 if (Idx < Ops.size()) {
2205 bool DeletedUMax = false;
2206 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2207 Ops.insert(Ops.end(), UMax->op_begin(), UMax->op_end());
2208 Ops.erase(Ops.begin()+Idx);
2213 return getUMaxExpr(Ops);
2216 // Okay, check to see if the same value occurs in the operand list twice. If
2217 // so, delete one. Since we sorted the list, these values are required to
2219 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2220 if (Ops[i] == Ops[i+1]) { // X umax Y umax Y --> X umax Y
2221 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2225 if (Ops.size() == 1) return Ops[0];
2227 assert(!Ops.empty() && "Reduced umax down to nothing!");
2229 // Okay, it looks like we really DO need a umax expr. Check to see if we
2230 // already have one, otherwise create a new one.
2231 FoldingSetNodeID ID;
2232 ID.AddInteger(scUMaxExpr);
2233 ID.AddInteger(Ops.size());
2234 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2235 ID.AddPointer(Ops[i]);
2237 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2238 SCEV *S = SCEVAllocator.Allocate<SCEVUMaxExpr>();
2239 new (S) SCEVUMaxExpr(ID, Ops);
2240 UniqueSCEVs.InsertNode(S, IP);
2244 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2246 // ~smax(~x, ~y) == smin(x, y).
2247 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2250 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2252 // ~umax(~x, ~y) == umin(x, y)
2253 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2256 const SCEV *ScalarEvolution::getSizeOfExpr(const Type *AllocTy) {
2257 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2258 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2259 C = ConstantFoldConstantExpression(CE, TD);
2260 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2261 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2264 const SCEV *ScalarEvolution::getAlignOfExpr(const Type *AllocTy) {
2265 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2266 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2267 C = ConstantFoldConstantExpression(CE, TD);
2268 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2269 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2272 const SCEV *ScalarEvolution::getOffsetOfExpr(const StructType *STy,
2274 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2275 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2276 C = ConstantFoldConstantExpression(CE, TD);
2277 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2278 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2281 const SCEV *ScalarEvolution::getOffsetOfExpr(const Type *CTy,
2282 Constant *FieldNo) {
2283 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2284 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2285 C = ConstantFoldConstantExpression(CE, TD);
2286 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2287 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2290 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2291 // Don't attempt to do anything other than create a SCEVUnknown object
2292 // here. createSCEV only calls getUnknown after checking for all other
2293 // interesting possibilities, and any other code that calls getUnknown
2294 // is doing so in order to hide a value from SCEV canonicalization.
2296 FoldingSetNodeID ID;
2297 ID.AddInteger(scUnknown);
2300 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2301 SCEV *S = SCEVAllocator.Allocate<SCEVUnknown>();
2302 new (S) SCEVUnknown(ID, V);
2303 UniqueSCEVs.InsertNode(S, IP);
2307 //===----------------------------------------------------------------------===//
2308 // Basic SCEV Analysis and PHI Idiom Recognition Code
2311 /// isSCEVable - Test if values of the given type are analyzable within
2312 /// the SCEV framework. This primarily includes integer types, and it
2313 /// can optionally include pointer types if the ScalarEvolution class
2314 /// has access to target-specific information.
2315 bool ScalarEvolution::isSCEVable(const Type *Ty) const {
2316 // Integers and pointers are always SCEVable.
2317 return Ty->isIntegerTy() || Ty->isPointerTy();
2320 /// getTypeSizeInBits - Return the size in bits of the specified type,
2321 /// for which isSCEVable must return true.
2322 uint64_t ScalarEvolution::getTypeSizeInBits(const Type *Ty) const {
2323 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2325 // If we have a TargetData, use it!
2327 return TD->getTypeSizeInBits(Ty);
2329 // Integer types have fixed sizes.
2330 if (Ty->isIntegerTy())
2331 return Ty->getPrimitiveSizeInBits();
2333 // The only other support type is pointer. Without TargetData, conservatively
2334 // assume pointers are 64-bit.
2335 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2339 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2340 /// the given type and which represents how SCEV will treat the given
2341 /// type, for which isSCEVable must return true. For pointer types,
2342 /// this is the pointer-sized integer type.
2343 const Type *ScalarEvolution::getEffectiveSCEVType(const Type *Ty) const {
2344 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2346 if (Ty->isIntegerTy())
2349 // The only other support type is pointer.
2350 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2351 if (TD) return TD->getIntPtrType(getContext());
2353 // Without TargetData, conservatively assume pointers are 64-bit.
2354 return Type::getInt64Ty(getContext());
2357 const SCEV *ScalarEvolution::getCouldNotCompute() {
2358 return &CouldNotCompute;
2361 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2362 /// expression and create a new one.
2363 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2364 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2366 std::map<SCEVCallbackVH, const SCEV *>::iterator I = Scalars.find(V);
2367 if (I != Scalars.end()) return I->second;
2368 const SCEV *S = createSCEV(V);
2369 Scalars.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2373 /// getIntegerSCEV - Given a SCEVable type, create a constant for the
2374 /// specified signed integer value and return a SCEV for the constant.
2375 const SCEV *ScalarEvolution::getIntegerSCEV(int64_t Val, const Type *Ty) {
2376 const IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
2377 return getConstant(ConstantInt::get(ITy, Val));
2380 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2382 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2383 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2385 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2387 const Type *Ty = V->getType();
2388 Ty = getEffectiveSCEVType(Ty);
2389 return getMulExpr(V,
2390 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2393 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2394 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2395 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2397 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2399 const Type *Ty = V->getType();
2400 Ty = getEffectiveSCEVType(Ty);
2401 const SCEV *AllOnes =
2402 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2403 return getMinusSCEV(AllOnes, V);
2406 /// getMinusSCEV - Return a SCEV corresponding to LHS - RHS.
2408 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
2411 return getAddExpr(LHS, getNegativeSCEV(RHS));
2414 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2415 /// input value to the specified type. If the type must be extended, it is zero
2418 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V,
2420 const Type *SrcTy = V->getType();
2421 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2422 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2423 "Cannot truncate or zero extend with non-integer arguments!");
2424 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2425 return V; // No conversion
2426 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2427 return getTruncateExpr(V, Ty);
2428 return getZeroExtendExpr(V, Ty);
2431 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2432 /// input value to the specified type. If the type must be extended, it is sign
2435 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2437 const Type *SrcTy = V->getType();
2438 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2439 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2440 "Cannot truncate or zero extend with non-integer arguments!");
2441 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2442 return V; // No conversion
2443 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2444 return getTruncateExpr(V, Ty);
2445 return getSignExtendExpr(V, Ty);
2448 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2449 /// input value to the specified type. If the type must be extended, it is zero
2450 /// extended. The conversion must not be narrowing.
2452 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, const Type *Ty) {
2453 const Type *SrcTy = V->getType();
2454 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2455 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2456 "Cannot noop or zero extend with non-integer arguments!");
2457 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2458 "getNoopOrZeroExtend cannot truncate!");
2459 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2460 return V; // No conversion
2461 return getZeroExtendExpr(V, Ty);
2464 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2465 /// input value to the specified type. If the type must be extended, it is sign
2466 /// extended. The conversion must not be narrowing.
2468 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, const Type *Ty) {
2469 const Type *SrcTy = V->getType();
2470 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2471 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2472 "Cannot noop or sign extend with non-integer arguments!");
2473 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2474 "getNoopOrSignExtend cannot truncate!");
2475 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2476 return V; // No conversion
2477 return getSignExtendExpr(V, Ty);
2480 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2481 /// the input value to the specified type. If the type must be extended,
2482 /// it is extended with unspecified bits. The conversion must not be
2485 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, const Type *Ty) {
2486 const Type *SrcTy = V->getType();
2487 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2488 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2489 "Cannot noop or any extend with non-integer arguments!");
2490 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2491 "getNoopOrAnyExtend cannot truncate!");
2492 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2493 return V; // No conversion
2494 return getAnyExtendExpr(V, Ty);
2497 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2498 /// input value to the specified type. The conversion must not be widening.
2500 ScalarEvolution::getTruncateOrNoop(const SCEV *V, const Type *Ty) {
2501 const Type *SrcTy = V->getType();
2502 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2503 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2504 "Cannot truncate or noop with non-integer arguments!");
2505 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2506 "getTruncateOrNoop cannot extend!");
2507 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2508 return V; // No conversion
2509 return getTruncateExpr(V, Ty);
2512 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2513 /// the types using zero-extension, and then perform a umax operation
2515 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2517 const SCEV *PromotedLHS = LHS;
2518 const SCEV *PromotedRHS = RHS;
2520 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2521 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2523 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2525 return getUMaxExpr(PromotedLHS, PromotedRHS);
2528 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2529 /// the types using zero-extension, and then perform a umin operation
2531 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2533 const SCEV *PromotedLHS = LHS;
2534 const SCEV *PromotedRHS = RHS;
2536 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2537 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2539 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2541 return getUMinExpr(PromotedLHS, PromotedRHS);
2544 /// PushDefUseChildren - Push users of the given Instruction
2545 /// onto the given Worklist.
2547 PushDefUseChildren(Instruction *I,
2548 SmallVectorImpl<Instruction *> &Worklist) {
2549 // Push the def-use children onto the Worklist stack.
2550 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2552 Worklist.push_back(cast<Instruction>(UI));
2555 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2556 /// instructions that depend on the given instruction and removes them from
2557 /// the Scalars map if they reference SymName. This is used during PHI
2560 ScalarEvolution::ForgetSymbolicName(Instruction *I, const SCEV *SymName) {
2561 SmallVector<Instruction *, 16> Worklist;
2562 PushDefUseChildren(I, Worklist);
2564 SmallPtrSet<Instruction *, 8> Visited;
2566 while (!Worklist.empty()) {
2567 Instruction *I = Worklist.pop_back_val();
2568 if (!Visited.insert(I)) continue;
2570 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
2571 Scalars.find(static_cast<Value *>(I));
2572 if (It != Scalars.end()) {
2573 // Short-circuit the def-use traversal if the symbolic name
2574 // ceases to appear in expressions.
2575 if (It->second != SymName && !It->second->hasOperand(SymName))
2578 // SCEVUnknown for a PHI either means that it has an unrecognized
2579 // structure, or it's a PHI that's in the progress of being computed
2580 // by createNodeForPHI. In the former case, additional loop trip
2581 // count information isn't going to change anything. In the later
2582 // case, createNodeForPHI will perform the necessary updates on its
2583 // own when it gets to that point.
2584 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(It->second)) {
2585 ValuesAtScopes.erase(It->second);
2590 PushDefUseChildren(I, Worklist);
2594 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2595 /// a loop header, making it a potential recurrence, or it doesn't.
2597 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2598 if (PN->getNumIncomingValues() == 2) // The loops have been canonicalized.
2599 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2600 if (L->getHeader() == PN->getParent()) {
2601 // If it lives in the loop header, it has two incoming values, one
2602 // from outside the loop, and one from inside.
2603 unsigned IncomingEdge = L->contains(PN->getIncomingBlock(0));
2604 unsigned BackEdge = IncomingEdge^1;
2606 // While we are analyzing this PHI node, handle its value symbolically.
2607 const SCEV *SymbolicName = getUnknown(PN);
2608 assert(Scalars.find(PN) == Scalars.end() &&
2609 "PHI node already processed?");
2610 Scalars.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2612 // Using this symbolic name for the PHI, analyze the value coming around
2614 Value *BEValueV = PN->getIncomingValue(BackEdge);
2615 const SCEV *BEValue = getSCEV(BEValueV);
2617 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2618 // has a special value for the first iteration of the loop.
2620 // If the value coming around the backedge is an add with the symbolic
2621 // value we just inserted, then we found a simple induction variable!
2622 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2623 // If there is a single occurrence of the symbolic value, replace it
2624 // with a recurrence.
2625 unsigned FoundIndex = Add->getNumOperands();
2626 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2627 if (Add->getOperand(i) == SymbolicName)
2628 if (FoundIndex == e) {
2633 if (FoundIndex != Add->getNumOperands()) {
2634 // Create an add with everything but the specified operand.
2635 SmallVector<const SCEV *, 8> Ops;
2636 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2637 if (i != FoundIndex)
2638 Ops.push_back(Add->getOperand(i));
2639 const SCEV *Accum = getAddExpr(Ops);
2641 // This is not a valid addrec if the step amount is varying each
2642 // loop iteration, but is not itself an addrec in this loop.
2643 if (Accum->isLoopInvariant(L) ||
2644 (isa<SCEVAddRecExpr>(Accum) &&
2645 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2646 bool HasNUW = false;
2647 bool HasNSW = false;
2649 // If the increment doesn't overflow, then neither the addrec nor
2650 // the post-increment will overflow.
2651 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2652 if (OBO->hasNoUnsignedWrap())
2654 if (OBO->hasNoSignedWrap())
2658 const SCEV *StartVal =
2659 getSCEV(PN->getIncomingValue(IncomingEdge));
2660 const SCEV *PHISCEV =
2661 getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
2663 // Since the no-wrap flags are on the increment, they apply to the
2664 // post-incremented value as well.
2665 if (Accum->isLoopInvariant(L))
2666 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2667 Accum, L, HasNUW, HasNSW);
2669 // Okay, for the entire analysis of this edge we assumed the PHI
2670 // to be symbolic. We now need to go back and purge all of the
2671 // entries for the scalars that use the symbolic expression.
2672 ForgetSymbolicName(PN, SymbolicName);
2673 Scalars[SCEVCallbackVH(PN, this)] = PHISCEV;
2677 } else if (const SCEVAddRecExpr *AddRec =
2678 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2679 // Otherwise, this could be a loop like this:
2680 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2681 // In this case, j = {1,+,1} and BEValue is j.
2682 // Because the other in-value of i (0) fits the evolution of BEValue
2683 // i really is an addrec evolution.
2684 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2685 const SCEV *StartVal = getSCEV(PN->getIncomingValue(IncomingEdge));
2687 // If StartVal = j.start - j.stride, we can use StartVal as the
2688 // initial step of the addrec evolution.
2689 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2690 AddRec->getOperand(1))) {
2691 const SCEV *PHISCEV =
2692 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
2694 // Okay, for the entire analysis of this edge we assumed the PHI
2695 // to be symbolic. We now need to go back and purge all of the
2696 // entries for the scalars that use the symbolic expression.
2697 ForgetSymbolicName(PN, SymbolicName);
2698 Scalars[SCEVCallbackVH(PN, this)] = PHISCEV;
2704 return SymbolicName;
2707 // It's tempting to recognize PHIs with a unique incoming value, however
2708 // this leads passes like indvars to break LCSSA form. Fortunately, such
2709 // PHIs are rare, as instcombine zaps them.
2711 // If it's not a loop phi, we can't handle it yet.
2712 return getUnknown(PN);
2715 /// createNodeForGEP - Expand GEP instructions into add and multiply
2716 /// operations. This allows them to be analyzed by regular SCEV code.
2718 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
2720 bool InBounds = GEP->isInBounds();
2721 const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
2722 Value *Base = GEP->getOperand(0);
2723 // Don't attempt to analyze GEPs over unsized objects.
2724 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
2725 return getUnknown(GEP);
2726 const SCEV *TotalOffset = getIntegerSCEV(0, IntPtrTy);
2727 gep_type_iterator GTI = gep_type_begin(GEP);
2728 for (GetElementPtrInst::op_iterator I = next(GEP->op_begin()),
2732 // Compute the (potentially symbolic) offset in bytes for this index.
2733 if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
2734 // For a struct, add the member offset.
2735 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
2736 TotalOffset = getAddExpr(TotalOffset,
2737 getOffsetOfExpr(STy, FieldNo),
2738 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2740 // For an array, add the element offset, explicitly scaled.
2741 const SCEV *LocalOffset = getSCEV(Index);
2742 // Getelementptr indicies are signed.
2743 LocalOffset = getTruncateOrSignExtend(LocalOffset, IntPtrTy);
2744 // Lower "inbounds" GEPs to NSW arithmetic.
2745 LocalOffset = getMulExpr(LocalOffset, getSizeOfExpr(*GTI),
2746 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2747 TotalOffset = getAddExpr(TotalOffset, LocalOffset,
2748 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2751 return getAddExpr(getSCEV(Base), TotalOffset,
2752 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2755 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
2756 /// guaranteed to end in (at every loop iteration). It is, at the same time,
2757 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
2758 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
2760 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
2761 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2762 return C->getValue()->getValue().countTrailingZeros();
2764 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
2765 return std::min(GetMinTrailingZeros(T->getOperand()),
2766 (uint32_t)getTypeSizeInBits(T->getType()));
2768 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
2769 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2770 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2771 getTypeSizeInBits(E->getType()) : OpRes;
2774 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
2775 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2776 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2777 getTypeSizeInBits(E->getType()) : OpRes;
2780 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
2781 // The result is the min of all operands results.
2782 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2783 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2784 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2788 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
2789 // The result is the sum of all operands results.
2790 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
2791 uint32_t BitWidth = getTypeSizeInBits(M->getType());
2792 for (unsigned i = 1, e = M->getNumOperands();
2793 SumOpRes != BitWidth && i != e; ++i)
2794 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
2799 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
2800 // The result is the min of all operands results.
2801 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2802 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2803 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2807 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
2808 // The result is the min of all operands results.
2809 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2810 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2811 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2815 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
2816 // The result is the min of all operands results.
2817 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2818 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2819 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2823 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2824 // For a SCEVUnknown, ask ValueTracking.
2825 unsigned BitWidth = getTypeSizeInBits(U->getType());
2826 APInt Mask = APInt::getAllOnesValue(BitWidth);
2827 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
2828 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
2829 return Zeros.countTrailingOnes();
2836 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
2839 ScalarEvolution::getUnsignedRange(const SCEV *S) {
2841 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2842 return ConstantRange(C->getValue()->getValue());
2844 unsigned BitWidth = getTypeSizeInBits(S->getType());
2845 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
2847 // If the value has known zeros, the maximum unsigned value will have those
2848 // known zeros as well.
2849 uint32_t TZ = GetMinTrailingZeros(S);
2851 ConservativeResult =
2852 ConstantRange(APInt::getMinValue(BitWidth),
2853 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
2855 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2856 ConstantRange X = getUnsignedRange(Add->getOperand(0));
2857 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
2858 X = X.add(getUnsignedRange(Add->getOperand(i)));
2859 return ConservativeResult.intersectWith(X);
2862 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2863 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
2864 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
2865 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
2866 return ConservativeResult.intersectWith(X);
2869 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
2870 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
2871 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
2872 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
2873 return ConservativeResult.intersectWith(X);
2876 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
2877 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
2878 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
2879 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
2880 return ConservativeResult.intersectWith(X);
2883 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
2884 ConstantRange X = getUnsignedRange(UDiv->getLHS());
2885 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
2886 return ConservativeResult.intersectWith(X.udiv(Y));
2889 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
2890 ConstantRange X = getUnsignedRange(ZExt->getOperand());
2891 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
2894 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
2895 ConstantRange X = getUnsignedRange(SExt->getOperand());
2896 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
2899 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
2900 ConstantRange X = getUnsignedRange(Trunc->getOperand());
2901 return ConservativeResult.intersectWith(X.truncate(BitWidth));
2904 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
2905 // If there's no unsigned wrap, the value will never be less than its
2907 if (AddRec->hasNoUnsignedWrap())
2908 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
2909 ConservativeResult =
2910 ConstantRange(C->getValue()->getValue(),
2911 APInt(getTypeSizeInBits(C->getType()), 0));
2913 // TODO: non-affine addrec
2914 if (AddRec->isAffine()) {
2915 const Type *Ty = AddRec->getType();
2916 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
2917 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
2918 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
2919 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
2921 const SCEV *Start = AddRec->getStart();
2922 const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this);
2924 // Check for overflow.
2925 if (!AddRec->hasNoUnsignedWrap())
2926 return ConservativeResult;
2928 ConstantRange StartRange = getUnsignedRange(Start);
2929 ConstantRange EndRange = getUnsignedRange(End);
2930 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
2931 EndRange.getUnsignedMin());
2932 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
2933 EndRange.getUnsignedMax());
2934 if (Min.isMinValue() && Max.isMaxValue())
2935 return ConservativeResult;
2936 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
2940 return ConservativeResult;
2943 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2944 // For a SCEVUnknown, ask ValueTracking.
2945 unsigned BitWidth = getTypeSizeInBits(U->getType());
2946 APInt Mask = APInt::getAllOnesValue(BitWidth);
2947 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
2948 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
2949 if (Ones == ~Zeros + 1)
2950 return ConservativeResult;
2951 return ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
2954 return ConservativeResult;
2957 /// getSignedRange - Determine the signed range for a particular SCEV.
2960 ScalarEvolution::getSignedRange(const SCEV *S) {
2962 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2963 return ConstantRange(C->getValue()->getValue());
2965 unsigned BitWidth = getTypeSizeInBits(S->getType());
2966 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
2968 // If the value has known zeros, the maximum signed value will have those
2969 // known zeros as well.
2970 uint32_t TZ = GetMinTrailingZeros(S);
2972 ConservativeResult =
2973 ConstantRange(APInt::getSignedMinValue(BitWidth),
2974 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
2976 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2977 ConstantRange X = getSignedRange(Add->getOperand(0));
2978 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
2979 X = X.add(getSignedRange(Add->getOperand(i)));
2980 return ConservativeResult.intersectWith(X);
2983 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2984 ConstantRange X = getSignedRange(Mul->getOperand(0));
2985 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
2986 X = X.multiply(getSignedRange(Mul->getOperand(i)));
2987 return ConservativeResult.intersectWith(X);
2990 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
2991 ConstantRange X = getSignedRange(SMax->getOperand(0));
2992 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
2993 X = X.smax(getSignedRange(SMax->getOperand(i)));
2994 return ConservativeResult.intersectWith(X);
2997 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
2998 ConstantRange X = getSignedRange(UMax->getOperand(0));
2999 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3000 X = X.umax(getSignedRange(UMax->getOperand(i)));
3001 return ConservativeResult.intersectWith(X);
3004 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3005 ConstantRange X = getSignedRange(UDiv->getLHS());
3006 ConstantRange Y = getSignedRange(UDiv->getRHS());
3007 return ConservativeResult.intersectWith(X.udiv(Y));
3010 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3011 ConstantRange X = getSignedRange(ZExt->getOperand());
3012 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
3015 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3016 ConstantRange X = getSignedRange(SExt->getOperand());
3017 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
3020 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3021 ConstantRange X = getSignedRange(Trunc->getOperand());
3022 return ConservativeResult.intersectWith(X.truncate(BitWidth));
3025 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3026 // If there's no signed wrap, and all the operands have the same sign or
3027 // zero, the value won't ever change sign.
3028 if (AddRec->hasNoSignedWrap()) {
3029 bool AllNonNeg = true;
3030 bool AllNonPos = true;
3031 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3032 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3033 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3036 ConservativeResult = ConservativeResult.intersectWith(
3037 ConstantRange(APInt(BitWidth, 0),
3038 APInt::getSignedMinValue(BitWidth)));
3040 ConservativeResult = ConservativeResult.intersectWith(
3041 ConstantRange(APInt::getSignedMinValue(BitWidth),
3042 APInt(BitWidth, 1)));
3045 // TODO: non-affine addrec
3046 if (AddRec->isAffine()) {
3047 const Type *Ty = AddRec->getType();
3048 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3049 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3050 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3051 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3053 const SCEV *Start = AddRec->getStart();
3054 const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this);
3056 // Check for overflow.
3057 if (!AddRec->hasNoSignedWrap())
3058 return ConservativeResult;
3060 ConstantRange StartRange = getSignedRange(Start);
3061 ConstantRange EndRange = getSignedRange(End);
3062 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3063 EndRange.getSignedMin());
3064 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3065 EndRange.getSignedMax());
3066 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3067 return ConservativeResult;
3068 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
3072 return ConservativeResult;
3075 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3076 // For a SCEVUnknown, ask ValueTracking.
3077 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3078 return ConservativeResult;
3079 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3081 return ConservativeResult;
3082 return ConservativeResult.intersectWith(
3083 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3084 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1));
3087 return ConservativeResult;
3090 /// createSCEV - We know that there is no SCEV for the specified value.
3091 /// Analyze the expression.
3093 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3094 if (!isSCEVable(V->getType()))
3095 return getUnknown(V);
3097 unsigned Opcode = Instruction::UserOp1;
3098 if (Instruction *I = dyn_cast<Instruction>(V))
3099 Opcode = I->getOpcode();
3100 else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3101 Opcode = CE->getOpcode();
3102 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3103 return getConstant(CI);
3104 else if (isa<ConstantPointerNull>(V))
3105 return getIntegerSCEV(0, V->getType());
3106 else if (isa<UndefValue>(V))
3107 return getIntegerSCEV(0, V->getType());
3108 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3109 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3111 return getUnknown(V);
3113 Operator *U = cast<Operator>(V);
3115 case Instruction::Add:
3116 // Don't transfer the NSW and NUW bits from the Add instruction to the
3117 // Add expression, because the Instruction may be guarded by control
3118 // flow and the no-overflow bits may not be valid for the expression in
3120 return getAddExpr(getSCEV(U->getOperand(0)),
3121 getSCEV(U->getOperand(1)));
3122 case Instruction::Mul:
3123 // Don't transfer the NSW and NUW bits from the Mul instruction to the
3124 // Mul expression, as with Add.
3125 return getMulExpr(getSCEV(U->getOperand(0)),
3126 getSCEV(U->getOperand(1)));
3127 case Instruction::UDiv:
3128 return getUDivExpr(getSCEV(U->getOperand(0)),
3129 getSCEV(U->getOperand(1)));
3130 case Instruction::Sub:
3131 return getMinusSCEV(getSCEV(U->getOperand(0)),
3132 getSCEV(U->getOperand(1)));
3133 case Instruction::And:
3134 // For an expression like x&255 that merely masks off the high bits,
3135 // use zext(trunc(x)) as the SCEV expression.
3136 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3137 if (CI->isNullValue())
3138 return getSCEV(U->getOperand(1));
3139 if (CI->isAllOnesValue())
3140 return getSCEV(U->getOperand(0));
3141 const APInt &A = CI->getValue();
3143 // Instcombine's ShrinkDemandedConstant may strip bits out of
3144 // constants, obscuring what would otherwise be a low-bits mask.
3145 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3146 // knew about to reconstruct a low-bits mask value.
3147 unsigned LZ = A.countLeadingZeros();
3148 unsigned BitWidth = A.getBitWidth();
3149 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3150 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3151 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3153 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3155 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3157 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3158 IntegerType::get(getContext(), BitWidth - LZ)),
3163 case Instruction::Or:
3164 // If the RHS of the Or is a constant, we may have something like:
3165 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3166 // optimizations will transparently handle this case.
3168 // In order for this transformation to be safe, the LHS must be of the
3169 // form X*(2^n) and the Or constant must be less than 2^n.
3170 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3171 const SCEV *LHS = getSCEV(U->getOperand(0));
3172 const APInt &CIVal = CI->getValue();
3173 if (GetMinTrailingZeros(LHS) >=
3174 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3175 // Build a plain add SCEV.
3176 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3177 // If the LHS of the add was an addrec and it has no-wrap flags,
3178 // transfer the no-wrap flags, since an or won't introduce a wrap.
3179 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3180 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3181 if (OldAR->hasNoUnsignedWrap())
3182 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoUnsignedWrap(true);
3183 if (OldAR->hasNoSignedWrap())
3184 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoSignedWrap(true);
3190 case Instruction::Xor:
3191 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3192 // If the RHS of the xor is a signbit, then this is just an add.
3193 // Instcombine turns add of signbit into xor as a strength reduction step.
3194 if (CI->getValue().isSignBit())
3195 return getAddExpr(getSCEV(U->getOperand(0)),
3196 getSCEV(U->getOperand(1)));
3198 // If the RHS of xor is -1, then this is a not operation.
3199 if (CI->isAllOnesValue())
3200 return getNotSCEV(getSCEV(U->getOperand(0)));
3202 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3203 // This is a variant of the check for xor with -1, and it handles
3204 // the case where instcombine has trimmed non-demanded bits out
3205 // of an xor with -1.
3206 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3207 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3208 if (BO->getOpcode() == Instruction::And &&
3209 LCI->getValue() == CI->getValue())
3210 if (const SCEVZeroExtendExpr *Z =
3211 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3212 const Type *UTy = U->getType();
3213 const SCEV *Z0 = Z->getOperand();
3214 const Type *Z0Ty = Z0->getType();
3215 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3217 // If C is a low-bits mask, the zero extend is zerving to
3218 // mask off the high bits. Complement the operand and
3219 // re-apply the zext.
3220 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3221 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3223 // If C is a single bit, it may be in the sign-bit position
3224 // before the zero-extend. In this case, represent the xor
3225 // using an add, which is equivalent, and re-apply the zext.
3226 APInt Trunc = APInt(CI->getValue()).trunc(Z0TySize);
3227 if (APInt(Trunc).zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3229 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3235 case Instruction::Shl:
3236 // Turn shift left of a constant amount into a multiply.
3237 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3238 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3239 Constant *X = ConstantInt::get(getContext(),
3240 APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
3241 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3245 case Instruction::LShr:
3246 // Turn logical shift right of a constant into a unsigned divide.
3247 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3248 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3249 Constant *X = ConstantInt::get(getContext(),
3250 APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
3251 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3255 case Instruction::AShr:
3256 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3257 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3258 if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
3259 if (L->getOpcode() == Instruction::Shl &&
3260 L->getOperand(1) == U->getOperand(1)) {
3261 unsigned BitWidth = getTypeSizeInBits(U->getType());
3262 uint64_t Amt = BitWidth - CI->getZExtValue();
3263 if (Amt == BitWidth)
3264 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3266 return getIntegerSCEV(0, U->getType()); // value is undefined
3268 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3269 IntegerType::get(getContext(), Amt)),
3274 case Instruction::Trunc:
3275 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3277 case Instruction::ZExt:
3278 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3280 case Instruction::SExt:
3281 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3283 case Instruction::BitCast:
3284 // BitCasts are no-op casts so we just eliminate the cast.
3285 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3286 return getSCEV(U->getOperand(0));
3289 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3290 // lead to pointer expressions which cannot safely be expanded to GEPs,
3291 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3292 // simplifying integer expressions.
3294 case Instruction::GetElementPtr:
3295 return createNodeForGEP(cast<GEPOperator>(U));
3297 case Instruction::PHI:
3298 return createNodeForPHI(cast<PHINode>(U));
3300 case Instruction::Select:
3301 // This could be a smax or umax that was lowered earlier.
3302 // Try to recover it.
3303 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3304 Value *LHS = ICI->getOperand(0);
3305 Value *RHS = ICI->getOperand(1);
3306 switch (ICI->getPredicate()) {
3307 case ICmpInst::ICMP_SLT:
3308 case ICmpInst::ICMP_SLE:
3309 std::swap(LHS, RHS);
3311 case ICmpInst::ICMP_SGT:
3312 case ICmpInst::ICMP_SGE:
3313 if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
3314 return getSMaxExpr(getSCEV(LHS), getSCEV(RHS));
3315 else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
3316 return getSMinExpr(getSCEV(LHS), getSCEV(RHS));
3318 case ICmpInst::ICMP_ULT:
3319 case ICmpInst::ICMP_ULE:
3320 std::swap(LHS, RHS);
3322 case ICmpInst::ICMP_UGT:
3323 case ICmpInst::ICMP_UGE:
3324 if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
3325 return getUMaxExpr(getSCEV(LHS), getSCEV(RHS));
3326 else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
3327 return getUMinExpr(getSCEV(LHS), getSCEV(RHS));
3329 case ICmpInst::ICMP_NE:
3330 // n != 0 ? n : 1 -> umax(n, 1)
3331 if (LHS == U->getOperand(1) &&
3332 isa<ConstantInt>(U->getOperand(2)) &&
3333 cast<ConstantInt>(U->getOperand(2))->isOne() &&
3334 isa<ConstantInt>(RHS) &&
3335 cast<ConstantInt>(RHS)->isZero())
3336 return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(2)));
3338 case ICmpInst::ICMP_EQ:
3339 // n == 0 ? 1 : n -> umax(n, 1)
3340 if (LHS == U->getOperand(2) &&
3341 isa<ConstantInt>(U->getOperand(1)) &&
3342 cast<ConstantInt>(U->getOperand(1))->isOne() &&
3343 isa<ConstantInt>(RHS) &&
3344 cast<ConstantInt>(RHS)->isZero())
3345 return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(1)));
3352 default: // We cannot analyze this expression.
3356 return getUnknown(V);
3361 //===----------------------------------------------------------------------===//
3362 // Iteration Count Computation Code
3365 /// getBackedgeTakenCount - If the specified loop has a predictable
3366 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3367 /// object. The backedge-taken count is the number of times the loop header
3368 /// will be branched to from within the loop. This is one less than the
3369 /// trip count of the loop, since it doesn't count the first iteration,
3370 /// when the header is branched to from outside the loop.
3372 /// Note that it is not valid to call this method on a loop without a
3373 /// loop-invariant backedge-taken count (see
3374 /// hasLoopInvariantBackedgeTakenCount).
3376 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3377 return getBackedgeTakenInfo(L).Exact;
3380 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3381 /// return the least SCEV value that is known never to be less than the
3382 /// actual backedge taken count.
3383 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3384 return getBackedgeTakenInfo(L).Max;
3387 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3388 /// onto the given Worklist.
3390 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3391 BasicBlock *Header = L->getHeader();
3393 // Push all Loop-header PHIs onto the Worklist stack.
3394 for (BasicBlock::iterator I = Header->begin();
3395 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3396 Worklist.push_back(PN);
3399 const ScalarEvolution::BackedgeTakenInfo &
3400 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3401 // Initially insert a CouldNotCompute for this loop. If the insertion
3402 // succeeds, procede to actually compute a backedge-taken count and
3403 // update the value. The temporary CouldNotCompute value tells SCEV
3404 // code elsewhere that it shouldn't attempt to request a new
3405 // backedge-taken count, which could result in infinite recursion.
3406 std::pair<std::map<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3407 BackedgeTakenCounts.insert(std::make_pair(L, getCouldNotCompute()));
3409 BackedgeTakenInfo BECount = ComputeBackedgeTakenCount(L);
3410 if (BECount.Exact != getCouldNotCompute()) {
3411 assert(BECount.Exact->isLoopInvariant(L) &&
3412 BECount.Max->isLoopInvariant(L) &&
3413 "Computed backedge-taken count isn't loop invariant for loop!");
3414 ++NumTripCountsComputed;
3416 // Update the value in the map.
3417 Pair.first->second = BECount;
3419 if (BECount.Max != getCouldNotCompute())
3420 // Update the value in the map.
3421 Pair.first->second = BECount;
3422 if (isa<PHINode>(L->getHeader()->begin()))
3423 // Only count loops that have phi nodes as not being computable.
3424 ++NumTripCountsNotComputed;
3427 // Now that we know more about the trip count for this loop, forget any
3428 // existing SCEV values for PHI nodes in this loop since they are only
3429 // conservative estimates made without the benefit of trip count
3430 // information. This is similar to the code in forgetLoop, except that
3431 // it handles SCEVUnknown PHI nodes specially.
3432 if (BECount.hasAnyInfo()) {
3433 SmallVector<Instruction *, 16> Worklist;
3434 PushLoopPHIs(L, Worklist);
3436 SmallPtrSet<Instruction *, 8> Visited;
3437 while (!Worklist.empty()) {
3438 Instruction *I = Worklist.pop_back_val();
3439 if (!Visited.insert(I)) continue;
3441 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3442 Scalars.find(static_cast<Value *>(I));
3443 if (It != Scalars.end()) {
3444 // SCEVUnknown for a PHI either means that it has an unrecognized
3445 // structure, or it's a PHI that's in the progress of being computed
3446 // by createNodeForPHI. In the former case, additional loop trip
3447 // count information isn't going to change anything. In the later
3448 // case, createNodeForPHI will perform the necessary updates on its
3449 // own when it gets to that point.
3450 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(It->second)) {
3451 ValuesAtScopes.erase(It->second);
3454 if (PHINode *PN = dyn_cast<PHINode>(I))
3455 ConstantEvolutionLoopExitValue.erase(PN);
3458 PushDefUseChildren(I, Worklist);
3462 return Pair.first->second;
3465 /// forgetLoop - This method should be called by the client when it has
3466 /// changed a loop in a way that may effect ScalarEvolution's ability to
3467 /// compute a trip count, or if the loop is deleted.
3468 void ScalarEvolution::forgetLoop(const Loop *L) {
3469 // Drop any stored trip count value.
3470 BackedgeTakenCounts.erase(L);
3472 // Drop information about expressions based on loop-header PHIs.
3473 SmallVector<Instruction *, 16> Worklist;
3474 PushLoopPHIs(L, Worklist);
3476 SmallPtrSet<Instruction *, 8> Visited;
3477 while (!Worklist.empty()) {
3478 Instruction *I = Worklist.pop_back_val();
3479 if (!Visited.insert(I)) continue;
3481 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3482 Scalars.find(static_cast<Value *>(I));
3483 if (It != Scalars.end()) {
3484 ValuesAtScopes.erase(It->second);
3486 if (PHINode *PN = dyn_cast<PHINode>(I))
3487 ConstantEvolutionLoopExitValue.erase(PN);
3490 PushDefUseChildren(I, Worklist);
3494 /// forgetValue - This method should be called by the client when it has
3495 /// changed a value in a way that may effect its value, or which may
3496 /// disconnect it from a def-use chain linking it to a loop.
3497 void ScalarEvolution::forgetValue(Value *V) {
3498 Instruction *I = dyn_cast<Instruction>(V);
3501 // Drop information about expressions based on loop-header PHIs.
3502 SmallVector<Instruction *, 16> Worklist;
3503 Worklist.push_back(I);
3505 SmallPtrSet<Instruction *, 8> Visited;
3506 while (!Worklist.empty()) {
3507 I = Worklist.pop_back_val();
3508 if (!Visited.insert(I)) continue;
3510 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3511 Scalars.find(static_cast<Value *>(I));
3512 if (It != Scalars.end()) {
3513 ValuesAtScopes.erase(It->second);
3515 if (PHINode *PN = dyn_cast<PHINode>(I))
3516 ConstantEvolutionLoopExitValue.erase(PN);
3519 PushDefUseChildren(I, Worklist);
3523 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
3524 /// of the specified loop will execute.
3525 ScalarEvolution::BackedgeTakenInfo
3526 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
3527 SmallVector<BasicBlock *, 8> ExitingBlocks;
3528 L->getExitingBlocks(ExitingBlocks);
3530 // Examine all exits and pick the most conservative values.
3531 const SCEV *BECount = getCouldNotCompute();
3532 const SCEV *MaxBECount = getCouldNotCompute();
3533 bool CouldNotComputeBECount = false;
3534 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
3535 BackedgeTakenInfo NewBTI =
3536 ComputeBackedgeTakenCountFromExit(L, ExitingBlocks[i]);
3538 if (NewBTI.Exact == getCouldNotCompute()) {
3539 // We couldn't compute an exact value for this exit, so
3540 // we won't be able to compute an exact value for the loop.
3541 CouldNotComputeBECount = true;
3542 BECount = getCouldNotCompute();
3543 } else if (!CouldNotComputeBECount) {
3544 if (BECount == getCouldNotCompute())
3545 BECount = NewBTI.Exact;
3547 BECount = getUMinFromMismatchedTypes(BECount, NewBTI.Exact);
3549 if (MaxBECount == getCouldNotCompute())
3550 MaxBECount = NewBTI.Max;
3551 else if (NewBTI.Max != getCouldNotCompute())
3552 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, NewBTI.Max);
3555 return BackedgeTakenInfo(BECount, MaxBECount);
3558 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the backedge
3559 /// of the specified loop will execute if it exits via the specified block.
3560 ScalarEvolution::BackedgeTakenInfo
3561 ScalarEvolution::ComputeBackedgeTakenCountFromExit(const Loop *L,
3562 BasicBlock *ExitingBlock) {
3564 // Okay, we've chosen an exiting block. See what condition causes us to
3565 // exit at this block.
3567 // FIXME: we should be able to handle switch instructions (with a single exit)
3568 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
3569 if (ExitBr == 0) return getCouldNotCompute();
3570 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
3572 // At this point, we know we have a conditional branch that determines whether
3573 // the loop is exited. However, we don't know if the branch is executed each
3574 // time through the loop. If not, then the execution count of the branch will
3575 // not be equal to the trip count of the loop.
3577 // Currently we check for this by checking to see if the Exit branch goes to
3578 // the loop header. If so, we know it will always execute the same number of
3579 // times as the loop. We also handle the case where the exit block *is* the
3580 // loop header. This is common for un-rotated loops.
3582 // If both of those tests fail, walk up the unique predecessor chain to the
3583 // header, stopping if there is an edge that doesn't exit the loop. If the
3584 // header is reached, the execution count of the branch will be equal to the
3585 // trip count of the loop.
3587 // More extensive analysis could be done to handle more cases here.
3589 if (ExitBr->getSuccessor(0) != L->getHeader() &&
3590 ExitBr->getSuccessor(1) != L->getHeader() &&
3591 ExitBr->getParent() != L->getHeader()) {
3592 // The simple checks failed, try climbing the unique predecessor chain
3593 // up to the header.
3595 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
3596 BasicBlock *Pred = BB->getUniquePredecessor();
3598 return getCouldNotCompute();
3599 TerminatorInst *PredTerm = Pred->getTerminator();
3600 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
3601 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
3604 // If the predecessor has a successor that isn't BB and isn't
3605 // outside the loop, assume the worst.
3606 if (L->contains(PredSucc))
3607 return getCouldNotCompute();
3609 if (Pred == L->getHeader()) {
3616 return getCouldNotCompute();
3619 // Procede to the next level to examine the exit condition expression.
3620 return ComputeBackedgeTakenCountFromExitCond(L, ExitBr->getCondition(),
3621 ExitBr->getSuccessor(0),
3622 ExitBr->getSuccessor(1));
3625 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
3626 /// backedge of the specified loop will execute if its exit condition
3627 /// were a conditional branch of ExitCond, TBB, and FBB.
3628 ScalarEvolution::BackedgeTakenInfo
3629 ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
3633 // Check if the controlling expression for this loop is an And or Or.
3634 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
3635 if (BO->getOpcode() == Instruction::And) {
3636 // Recurse on the operands of the and.
3637 BackedgeTakenInfo BTI0 =
3638 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3639 BackedgeTakenInfo BTI1 =
3640 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3641 const SCEV *BECount = getCouldNotCompute();
3642 const SCEV *MaxBECount = getCouldNotCompute();
3643 if (L->contains(TBB)) {
3644 // Both conditions must be true for the loop to continue executing.
3645 // Choose the less conservative count.
3646 if (BTI0.Exact == getCouldNotCompute() ||
3647 BTI1.Exact == getCouldNotCompute())
3648 BECount = getCouldNotCompute();
3650 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3651 if (BTI0.Max == getCouldNotCompute())
3652 MaxBECount = BTI1.Max;
3653 else if (BTI1.Max == getCouldNotCompute())
3654 MaxBECount = BTI0.Max;
3656 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3658 // Both conditions must be true for the loop to exit.
3659 assert(L->contains(FBB) && "Loop block has no successor in loop!");
3660 if (BTI0.Exact != getCouldNotCompute() &&
3661 BTI1.Exact != getCouldNotCompute())
3662 BECount = getUMaxFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3663 if (BTI0.Max != getCouldNotCompute() &&
3664 BTI1.Max != getCouldNotCompute())
3665 MaxBECount = getUMaxFromMismatchedTypes(BTI0.Max, BTI1.Max);
3668 return BackedgeTakenInfo(BECount, MaxBECount);
3670 if (BO->getOpcode() == Instruction::Or) {
3671 // Recurse on the operands of the or.
3672 BackedgeTakenInfo BTI0 =
3673 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3674 BackedgeTakenInfo BTI1 =
3675 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3676 const SCEV *BECount = getCouldNotCompute();
3677 const SCEV *MaxBECount = getCouldNotCompute();
3678 if (L->contains(FBB)) {
3679 // Both conditions must be false for the loop to continue executing.
3680 // Choose the less conservative count.
3681 if (BTI0.Exact == getCouldNotCompute() ||
3682 BTI1.Exact == getCouldNotCompute())
3683 BECount = getCouldNotCompute();
3685 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3686 if (BTI0.Max == getCouldNotCompute())
3687 MaxBECount = BTI1.Max;
3688 else if (BTI1.Max == getCouldNotCompute())
3689 MaxBECount = BTI0.Max;
3691 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3693 // Both conditions must be false for the loop to exit.
3694 assert(L->contains(TBB) && "Loop block has no successor in loop!");
3695 if (BTI0.Exact != getCouldNotCompute() &&
3696 BTI1.Exact != getCouldNotCompute())
3697 BECount = getUMaxFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3698 if (BTI0.Max != getCouldNotCompute() &&
3699 BTI1.Max != getCouldNotCompute())
3700 MaxBECount = getUMaxFromMismatchedTypes(BTI0.Max, BTI1.Max);
3703 return BackedgeTakenInfo(BECount, MaxBECount);
3707 // With an icmp, it may be feasible to compute an exact backedge-taken count.
3708 // Procede to the next level to examine the icmp.
3709 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
3710 return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
3712 // Check for a constant condition. These are normally stripped out by
3713 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
3714 // preserve the CFG and is temporarily leaving constant conditions
3716 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
3717 if (L->contains(FBB) == !CI->getZExtValue())
3718 // The backedge is always taken.
3719 return getCouldNotCompute();
3721 // The backedge is never taken.
3722 return getIntegerSCEV(0, CI->getType());
3725 // If it's not an integer or pointer comparison then compute it the hard way.
3726 return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
3729 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of times the
3730 /// backedge of the specified loop will execute if its exit condition
3731 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
3732 ScalarEvolution::BackedgeTakenInfo
3733 ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
3738 // If the condition was exit on true, convert the condition to exit on false
3739 ICmpInst::Predicate Cond;
3740 if (!L->contains(FBB))
3741 Cond = ExitCond->getPredicate();
3743 Cond = ExitCond->getInversePredicate();
3745 // Handle common loops like: for (X = "string"; *X; ++X)
3746 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
3747 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
3749 ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
3750 if (!isa<SCEVCouldNotCompute>(ItCnt)) {
3751 unsigned BitWidth = getTypeSizeInBits(ItCnt->getType());
3752 return BackedgeTakenInfo(ItCnt,
3753 isa<SCEVConstant>(ItCnt) ? ItCnt :
3754 getConstant(APInt::getMaxValue(BitWidth)-1));
3758 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
3759 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
3761 // Try to evaluate any dependencies out of the loop.
3762 LHS = getSCEVAtScope(LHS, L);
3763 RHS = getSCEVAtScope(RHS, L);
3765 // At this point, we would like to compute how many iterations of the
3766 // loop the predicate will return true for these inputs.
3767 if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) {
3768 // If there is a loop-invariant, force it into the RHS.
3769 std::swap(LHS, RHS);
3770 Cond = ICmpInst::getSwappedPredicate(Cond);
3773 // If we have a comparison of a chrec against a constant, try to use value
3774 // ranges to answer this query.
3775 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
3776 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
3777 if (AddRec->getLoop() == L) {
3778 // Form the constant range.
3779 ConstantRange CompRange(
3780 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
3782 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
3783 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
3787 case ICmpInst::ICMP_NE: { // while (X != Y)
3788 // Convert to: while (X-Y != 0)
3789 const SCEV *TC = HowFarToZero(getMinusSCEV(LHS, RHS), L);
3790 if (!isa<SCEVCouldNotCompute>(TC)) return TC;
3793 case ICmpInst::ICMP_EQ: { // while (X == Y)
3794 // Convert to: while (X-Y == 0)
3795 const SCEV *TC = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
3796 if (!isa<SCEVCouldNotCompute>(TC)) return TC;
3799 case ICmpInst::ICMP_SLT: {
3800 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, true);
3801 if (BTI.hasAnyInfo()) return BTI;
3804 case ICmpInst::ICMP_SGT: {
3805 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
3806 getNotSCEV(RHS), L, true);
3807 if (BTI.hasAnyInfo()) return BTI;
3810 case ICmpInst::ICMP_ULT: {
3811 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, false);
3812 if (BTI.hasAnyInfo()) return BTI;
3815 case ICmpInst::ICMP_UGT: {
3816 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
3817 getNotSCEV(RHS), L, false);
3818 if (BTI.hasAnyInfo()) return BTI;
3823 dbgs() << "ComputeBackedgeTakenCount ";
3824 if (ExitCond->getOperand(0)->getType()->isUnsigned())
3825 dbgs() << "[unsigned] ";
3826 dbgs() << *LHS << " "
3827 << Instruction::getOpcodeName(Instruction::ICmp)
3828 << " " << *RHS << "\n";
3833 ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
3836 static ConstantInt *
3837 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
3838 ScalarEvolution &SE) {
3839 const SCEV *InVal = SE.getConstant(C);
3840 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
3841 assert(isa<SCEVConstant>(Val) &&
3842 "Evaluation of SCEV at constant didn't fold correctly?");
3843 return cast<SCEVConstant>(Val)->getValue();
3846 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
3847 /// and a GEP expression (missing the pointer index) indexing into it, return
3848 /// the addressed element of the initializer or null if the index expression is
3851 GetAddressedElementFromGlobal(GlobalVariable *GV,
3852 const std::vector<ConstantInt*> &Indices) {
3853 Constant *Init = GV->getInitializer();
3854 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
3855 uint64_t Idx = Indices[i]->getZExtValue();
3856 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
3857 assert(Idx < CS->getNumOperands() && "Bad struct index!");
3858 Init = cast<Constant>(CS->getOperand(Idx));
3859 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
3860 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
3861 Init = cast<Constant>(CA->getOperand(Idx));
3862 } else if (isa<ConstantAggregateZero>(Init)) {
3863 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
3864 assert(Idx < STy->getNumElements() && "Bad struct index!");
3865 Init = Constant::getNullValue(STy->getElementType(Idx));
3866 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
3867 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
3868 Init = Constant::getNullValue(ATy->getElementType());
3870 llvm_unreachable("Unknown constant aggregate type!");
3874 return 0; // Unknown initializer type
3880 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
3881 /// 'icmp op load X, cst', try to see if we can compute the backedge
3882 /// execution count.
3884 ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
3888 ICmpInst::Predicate predicate) {
3889 if (LI->isVolatile()) return getCouldNotCompute();
3891 // Check to see if the loaded pointer is a getelementptr of a global.
3892 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
3893 if (!GEP) return getCouldNotCompute();
3895 // Make sure that it is really a constant global we are gepping, with an
3896 // initializer, and make sure the first IDX is really 0.
3897 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
3898 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
3899 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
3900 !cast<Constant>(GEP->getOperand(1))->isNullValue())
3901 return getCouldNotCompute();
3903 // Okay, we allow one non-constant index into the GEP instruction.
3905 std::vector<ConstantInt*> Indexes;
3906 unsigned VarIdxNum = 0;
3907 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
3908 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
3909 Indexes.push_back(CI);
3910 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
3911 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
3912 VarIdx = GEP->getOperand(i);
3914 Indexes.push_back(0);
3917 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
3918 // Check to see if X is a loop variant variable value now.
3919 const SCEV *Idx = getSCEV(VarIdx);
3920 Idx = getSCEVAtScope(Idx, L);
3922 // We can only recognize very limited forms of loop index expressions, in
3923 // particular, only affine AddRec's like {C1,+,C2}.
3924 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
3925 if (!IdxExpr || !IdxExpr->isAffine() || IdxExpr->isLoopInvariant(L) ||
3926 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
3927 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
3928 return getCouldNotCompute();
3930 unsigned MaxSteps = MaxBruteForceIterations;
3931 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
3932 ConstantInt *ItCst = ConstantInt::get(
3933 cast<IntegerType>(IdxExpr->getType()), IterationNum);
3934 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
3936 // Form the GEP offset.
3937 Indexes[VarIdxNum] = Val;
3939 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
3940 if (Result == 0) break; // Cannot compute!
3942 // Evaluate the condition for this iteration.
3943 Result = ConstantExpr::getICmp(predicate, Result, RHS);
3944 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
3945 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
3947 dbgs() << "\n***\n*** Computed loop count " << *ItCst
3948 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
3951 ++NumArrayLenItCounts;
3952 return getConstant(ItCst); // Found terminating iteration!
3955 return getCouldNotCompute();
3959 /// CanConstantFold - Return true if we can constant fold an instruction of the
3960 /// specified type, assuming that all operands were constants.
3961 static bool CanConstantFold(const Instruction *I) {
3962 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
3963 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
3966 if (const CallInst *CI = dyn_cast<CallInst>(I))
3967 if (const Function *F = CI->getCalledFunction())
3968 return canConstantFoldCallTo(F);
3972 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
3973 /// in the loop that V is derived from. We allow arbitrary operations along the
3974 /// way, but the operands of an operation must either be constants or a value
3975 /// derived from a constant PHI. If this expression does not fit with these
3976 /// constraints, return null.
3977 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
3978 // If this is not an instruction, or if this is an instruction outside of the
3979 // loop, it can't be derived from a loop PHI.
3980 Instruction *I = dyn_cast<Instruction>(V);
3981 if (I == 0 || !L->contains(I)) return 0;
3983 if (PHINode *PN = dyn_cast<PHINode>(I)) {
3984 if (L->getHeader() == I->getParent())
3987 // We don't currently keep track of the control flow needed to evaluate
3988 // PHIs, so we cannot handle PHIs inside of loops.
3992 // If we won't be able to constant fold this expression even if the operands
3993 // are constants, return early.
3994 if (!CanConstantFold(I)) return 0;
3996 // Otherwise, we can evaluate this instruction if all of its operands are
3997 // constant or derived from a PHI node themselves.
3999 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4000 if (!(isa<Constant>(I->getOperand(Op)) ||
4001 isa<GlobalValue>(I->getOperand(Op)))) {
4002 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4003 if (P == 0) return 0; // Not evolving from PHI
4007 return 0; // Evolving from multiple different PHIs.
4010 // This is a expression evolving from a constant PHI!
4014 /// EvaluateExpression - Given an expression that passes the
4015 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4016 /// in the loop has the value PHIVal. If we can't fold this expression for some
4017 /// reason, return null.
4018 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4019 const TargetData *TD) {
4020 if (isa<PHINode>(V)) return PHIVal;
4021 if (Constant *C = dyn_cast<Constant>(V)) return C;
4022 if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) return GV;
4023 Instruction *I = cast<Instruction>(V);
4025 std::vector<Constant*> Operands;
4026 Operands.resize(I->getNumOperands());
4028 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4029 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4030 if (Operands[i] == 0) return 0;
4033 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4034 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4036 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4037 &Operands[0], Operands.size(), TD);
4040 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4041 /// in the header of its containing loop, we know the loop executes a
4042 /// constant number of times, and the PHI node is just a recurrence
4043 /// involving constants, fold it.
4045 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4048 std::map<PHINode*, Constant*>::iterator I =
4049 ConstantEvolutionLoopExitValue.find(PN);
4050 if (I != ConstantEvolutionLoopExitValue.end())
4053 if (BEs.ugt(APInt(BEs.getBitWidth(),MaxBruteForceIterations)))
4054 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4056 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4058 // Since the loop is canonicalized, the PHI node must have two entries. One
4059 // entry must be a constant (coming in from outside of the loop), and the
4060 // second must be derived from the same PHI.
4061 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4062 Constant *StartCST =
4063 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4065 return RetVal = 0; // Must be a constant.
4067 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4068 PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
4070 return RetVal = 0; // Not derived from same PHI.
4072 // Execute the loop symbolically to determine the exit value.
4073 if (BEs.getActiveBits() >= 32)
4074 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4076 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4077 unsigned IterationNum = 0;
4078 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4079 if (IterationNum == NumIterations)
4080 return RetVal = PHIVal; // Got exit value!
4082 // Compute the value of the PHI node for the next iteration.
4083 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4084 if (NextPHI == PHIVal)
4085 return RetVal = NextPHI; // Stopped evolving!
4087 return 0; // Couldn't evaluate!
4092 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute a
4093 /// constant number of times (the condition evolves only from constants),
4094 /// try to evaluate a few iterations of the loop until we get the exit
4095 /// condition gets a value of ExitWhen (true or false). If we cannot
4096 /// evaluate the trip count of the loop, return getCouldNotCompute().
4098 ScalarEvolution::ComputeBackedgeTakenCountExhaustively(const Loop *L,
4101 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4102 if (PN == 0) return getCouldNotCompute();
4104 // Since the loop is canonicalized, the PHI node must have two entries. One
4105 // entry must be a constant (coming in from outside of the loop), and the
4106 // second must be derived from the same PHI.
4107 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4108 Constant *StartCST =
4109 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4110 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4112 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4113 PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
4114 if (PN2 != PN) return getCouldNotCompute(); // Not derived from same PHI.
4116 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4117 // the loop symbolically to determine when the condition gets a value of
4119 unsigned IterationNum = 0;
4120 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4121 for (Constant *PHIVal = StartCST;
4122 IterationNum != MaxIterations; ++IterationNum) {
4123 ConstantInt *CondVal =
4124 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4126 // Couldn't symbolically evaluate.
4127 if (!CondVal) return getCouldNotCompute();
4129 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4130 ++NumBruteForceTripCountsComputed;
4131 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4134 // Compute the value of the PHI node for the next iteration.
4135 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4136 if (NextPHI == 0 || NextPHI == PHIVal)
4137 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4141 // Too many iterations were needed to evaluate.
4142 return getCouldNotCompute();
4145 /// getSCEVAtScope - Return a SCEV expression for the specified value
4146 /// at the specified scope in the program. The L value specifies a loop
4147 /// nest to evaluate the expression at, where null is the top-level or a
4148 /// specified loop is immediately inside of the loop.
4150 /// This method can be used to compute the exit value for a variable defined
4151 /// in a loop by querying what the value will hold in the parent loop.
4153 /// In the case that a relevant loop exit value cannot be computed, the
4154 /// original value V is returned.
4155 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4156 // Check to see if we've folded this expression at this loop before.
4157 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4158 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4159 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4161 return Pair.first->second ? Pair.first->second : V;
4163 // Otherwise compute it.
4164 const SCEV *C = computeSCEVAtScope(V, L);
4165 ValuesAtScopes[V][L] = C;
4169 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4170 if (isa<SCEVConstant>(V)) return V;
4172 // If this instruction is evolved from a constant-evolving PHI, compute the
4173 // exit value from the loop without using SCEVs.
4174 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4175 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4176 const Loop *LI = (*this->LI)[I->getParent()];
4177 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4178 if (PHINode *PN = dyn_cast<PHINode>(I))
4179 if (PN->getParent() == LI->getHeader()) {
4180 // Okay, there is no closed form solution for the PHI node. Check
4181 // to see if the loop that contains it has a known backedge-taken
4182 // count. If so, we may be able to force computation of the exit
4184 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4185 if (const SCEVConstant *BTCC =
4186 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4187 // Okay, we know how many times the containing loop executes. If
4188 // this is a constant evolving PHI node, get the final value at
4189 // the specified iteration number.
4190 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4191 BTCC->getValue()->getValue(),
4193 if (RV) return getSCEV(RV);
4197 // Okay, this is an expression that we cannot symbolically evaluate
4198 // into a SCEV. Check to see if it's possible to symbolically evaluate
4199 // the arguments into constants, and if so, try to constant propagate the
4200 // result. This is particularly useful for computing loop exit values.
4201 if (CanConstantFold(I)) {
4202 std::vector<Constant*> Operands;
4203 Operands.reserve(I->getNumOperands());
4204 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4205 Value *Op = I->getOperand(i);
4206 if (Constant *C = dyn_cast<Constant>(Op)) {
4207 Operands.push_back(C);
4209 // If any of the operands is non-constant and if they are
4210 // non-integer and non-pointer, don't even try to analyze them
4211 // with scev techniques.
4212 if (!isSCEVable(Op->getType()))
4215 const SCEV *OpV = getSCEVAtScope(Op, L);
4216 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV)) {
4217 Constant *C = SC->getValue();
4218 if (C->getType() != Op->getType())
4219 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4223 Operands.push_back(C);
4224 } else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV)) {
4225 if (Constant *C = dyn_cast<Constant>(SU->getValue())) {
4226 if (C->getType() != Op->getType())
4228 ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4232 Operands.push_back(C);
4242 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4243 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4244 Operands[0], Operands[1], TD);
4246 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4247 &Operands[0], Operands.size(), TD);
4252 // This is some other type of SCEVUnknown, just return it.
4256 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4257 // Avoid performing the look-up in the common case where the specified
4258 // expression has no loop-variant portions.
4259 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4260 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4261 if (OpAtScope != Comm->getOperand(i)) {
4262 // Okay, at least one of these operands is loop variant but might be
4263 // foldable. Build a new instance of the folded commutative expression.
4264 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4265 Comm->op_begin()+i);
4266 NewOps.push_back(OpAtScope);
4268 for (++i; i != e; ++i) {
4269 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4270 NewOps.push_back(OpAtScope);
4272 if (isa<SCEVAddExpr>(Comm))
4273 return getAddExpr(NewOps);
4274 if (isa<SCEVMulExpr>(Comm))
4275 return getMulExpr(NewOps);
4276 if (isa<SCEVSMaxExpr>(Comm))
4277 return getSMaxExpr(NewOps);
4278 if (isa<SCEVUMaxExpr>(Comm))
4279 return getUMaxExpr(NewOps);
4280 llvm_unreachable("Unknown commutative SCEV type!");
4283 // If we got here, all operands are loop invariant.
4287 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4288 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4289 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4290 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4291 return Div; // must be loop invariant
4292 return getUDivExpr(LHS, RHS);
4295 // If this is a loop recurrence for a loop that does not contain L, then we
4296 // are dealing with the final value computed by the loop.
4297 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4298 if (!L || !AddRec->getLoop()->contains(L)) {
4299 // To evaluate this recurrence, we need to know how many times the AddRec
4300 // loop iterates. Compute this now.
4301 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4302 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4304 // Then, evaluate the AddRec.
4305 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4310 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4311 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4312 if (Op == Cast->getOperand())
4313 return Cast; // must be loop invariant
4314 return getZeroExtendExpr(Op, Cast->getType());
4317 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4318 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4319 if (Op == Cast->getOperand())
4320 return Cast; // must be loop invariant
4321 return getSignExtendExpr(Op, Cast->getType());
4324 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4325 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4326 if (Op == Cast->getOperand())
4327 return Cast; // must be loop invariant
4328 return getTruncateExpr(Op, Cast->getType());
4331 llvm_unreachable("Unknown SCEV type!");
4335 /// getSCEVAtScope - This is a convenience function which does
4336 /// getSCEVAtScope(getSCEV(V), L).
4337 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4338 return getSCEVAtScope(getSCEV(V), L);
4341 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4342 /// following equation:
4344 /// A * X = B (mod N)
4346 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4347 /// A and B isn't important.
4349 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
4350 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4351 ScalarEvolution &SE) {
4352 uint32_t BW = A.getBitWidth();
4353 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4354 assert(A != 0 && "A must be non-zero.");
4358 // The gcd of A and N may have only one prime factor: 2. The number of
4359 // trailing zeros in A is its multiplicity
4360 uint32_t Mult2 = A.countTrailingZeros();
4363 // 2. Check if B is divisible by D.
4365 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4366 // is not less than multiplicity of this prime factor for D.
4367 if (B.countTrailingZeros() < Mult2)
4368 return SE.getCouldNotCompute();
4370 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4373 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4374 // bit width during computations.
4375 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4376 APInt Mod(BW + 1, 0);
4377 Mod.set(BW - Mult2); // Mod = N / D
4378 APInt I = AD.multiplicativeInverse(Mod);
4380 // 4. Compute the minimum unsigned root of the equation:
4381 // I * (B / D) mod (N / D)
4382 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4384 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4386 return SE.getConstant(Result.trunc(BW));
4389 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4390 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4391 /// might be the same) or two SCEVCouldNotCompute objects.
4393 static std::pair<const SCEV *,const SCEV *>
4394 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4395 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4396 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4397 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4398 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4400 // We currently can only solve this if the coefficients are constants.
4401 if (!LC || !MC || !NC) {
4402 const SCEV *CNC = SE.getCouldNotCompute();
4403 return std::make_pair(CNC, CNC);
4406 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4407 const APInt &L = LC->getValue()->getValue();
4408 const APInt &M = MC->getValue()->getValue();
4409 const APInt &N = NC->getValue()->getValue();
4410 APInt Two(BitWidth, 2);
4411 APInt Four(BitWidth, 4);
4414 using namespace APIntOps;
4416 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4417 // The B coefficient is M-N/2
4421 // The A coefficient is N/2
4422 APInt A(N.sdiv(Two));
4424 // Compute the B^2-4ac term.
4427 SqrtTerm -= Four * (A * C);
4429 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4430 // integer value or else APInt::sqrt() will assert.
4431 APInt SqrtVal(SqrtTerm.sqrt());
4433 // Compute the two solutions for the quadratic formula.
4434 // The divisions must be performed as signed divisions.
4436 APInt TwoA( A << 1 );
4437 if (TwoA.isMinValue()) {
4438 const SCEV *CNC = SE.getCouldNotCompute();
4439 return std::make_pair(CNC, CNC);
4442 LLVMContext &Context = SE.getContext();
4444 ConstantInt *Solution1 =
4445 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
4446 ConstantInt *Solution2 =
4447 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
4449 return std::make_pair(SE.getConstant(Solution1),
4450 SE.getConstant(Solution2));
4451 } // end APIntOps namespace
4454 /// HowFarToZero - Return the number of times a backedge comparing the specified
4455 /// value to zero will execute. If not computable, return CouldNotCompute.
4456 const SCEV *ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
4457 // If the value is a constant
4458 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4459 // If the value is already zero, the branch will execute zero times.
4460 if (C->getValue()->isZero()) return C;
4461 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4464 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
4465 if (!AddRec || AddRec->getLoop() != L)
4466 return getCouldNotCompute();
4468 if (AddRec->isAffine()) {
4469 // If this is an affine expression, the execution count of this branch is
4470 // the minimum unsigned root of the following equation:
4472 // Start + Step*N = 0 (mod 2^BW)
4476 // Step*N = -Start (mod 2^BW)
4478 // where BW is the common bit width of Start and Step.
4480 // Get the initial value for the loop.
4481 const SCEV *Start = getSCEVAtScope(AddRec->getStart(),
4482 L->getParentLoop());
4483 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1),
4484 L->getParentLoop());
4486 if (const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step)) {
4487 // For now we handle only constant steps.
4489 // First, handle unitary steps.
4490 if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
4491 return getNegativeSCEV(Start); // N = -Start (as unsigned)
4492 if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
4493 return Start; // N = Start (as unsigned)
4495 // Then, try to solve the above equation provided that Start is constant.
4496 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
4497 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
4498 -StartC->getValue()->getValue(),
4501 } else if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
4502 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
4503 // the quadratic equation to solve it.
4504 std::pair<const SCEV *,const SCEV *> Roots = SolveQuadraticEquation(AddRec,
4506 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
4507 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
4510 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
4511 << " sol#2: " << *R2 << "\n";
4513 // Pick the smallest positive root value.
4514 if (ConstantInt *CB =
4515 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
4516 R1->getValue(), R2->getValue()))) {
4517 if (CB->getZExtValue() == false)
4518 std::swap(R1, R2); // R1 is the minimum root now.
4520 // We can only use this value if the chrec ends up with an exact zero
4521 // value at this index. When solving for "X*X != 5", for example, we
4522 // should not accept a root of 2.
4523 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
4525 return R1; // We found a quadratic root!
4530 return getCouldNotCompute();
4533 /// HowFarToNonZero - Return the number of times a backedge checking the
4534 /// specified value for nonzero will execute. If not computable, return
4536 const SCEV *ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
4537 // Loops that look like: while (X == 0) are very strange indeed. We don't
4538 // handle them yet except for the trivial case. This could be expanded in the
4539 // future as needed.
4541 // If the value is a constant, check to see if it is known to be non-zero
4542 // already. If so, the backedge will execute zero times.
4543 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4544 if (!C->getValue()->isNullValue())
4545 return getIntegerSCEV(0, C->getType());
4546 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4549 // We could implement others, but I really doubt anyone writes loops like
4550 // this, and if they did, they would already be constant folded.
4551 return getCouldNotCompute();
4554 /// getLoopPredecessor - If the given loop's header has exactly one unique
4555 /// predecessor outside the loop, return it. Otherwise return null.
4557 BasicBlock *ScalarEvolution::getLoopPredecessor(const Loop *L) {
4558 BasicBlock *Header = L->getHeader();
4559 BasicBlock *Pred = 0;
4560 for (pred_iterator PI = pred_begin(Header), E = pred_end(Header);
4562 if (!L->contains(*PI)) {
4563 if (Pred && Pred != *PI) return 0; // Multiple predecessors.
4569 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
4570 /// (which may not be an immediate predecessor) which has exactly one
4571 /// successor from which BB is reachable, or null if no such block is
4575 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
4576 // If the block has a unique predecessor, then there is no path from the
4577 // predecessor to the block that does not go through the direct edge
4578 // from the predecessor to the block.
4579 if (BasicBlock *Pred = BB->getSinglePredecessor())
4582 // A loop's header is defined to be a block that dominates the loop.
4583 // If the header has a unique predecessor outside the loop, it must be
4584 // a block that has exactly one successor that can reach the loop.
4585 if (Loop *L = LI->getLoopFor(BB))
4586 return getLoopPredecessor(L);
4591 /// HasSameValue - SCEV structural equivalence is usually sufficient for
4592 /// testing whether two expressions are equal, however for the purposes of
4593 /// looking for a condition guarding a loop, it can be useful to be a little
4594 /// more general, since a front-end may have replicated the controlling
4597 static bool HasSameValue(const SCEV *A, const SCEV *B) {
4598 // Quick check to see if they are the same SCEV.
4599 if (A == B) return true;
4601 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
4602 // two different instructions with the same value. Check for this case.
4603 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
4604 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
4605 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
4606 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
4607 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
4610 // Otherwise assume they may have a different value.
4614 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
4615 return getSignedRange(S).getSignedMax().isNegative();
4618 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
4619 return getSignedRange(S).getSignedMin().isStrictlyPositive();
4622 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
4623 return !getSignedRange(S).getSignedMin().isNegative();
4626 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
4627 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
4630 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
4631 return isKnownNegative(S) || isKnownPositive(S);
4634 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
4635 const SCEV *LHS, const SCEV *RHS) {
4637 if (HasSameValue(LHS, RHS))
4638 return ICmpInst::isTrueWhenEqual(Pred);
4642 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
4644 case ICmpInst::ICMP_SGT:
4645 Pred = ICmpInst::ICMP_SLT;
4646 std::swap(LHS, RHS);
4647 case ICmpInst::ICMP_SLT: {
4648 ConstantRange LHSRange = getSignedRange(LHS);
4649 ConstantRange RHSRange = getSignedRange(RHS);
4650 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
4652 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
4656 case ICmpInst::ICMP_SGE:
4657 Pred = ICmpInst::ICMP_SLE;
4658 std::swap(LHS, RHS);
4659 case ICmpInst::ICMP_SLE: {
4660 ConstantRange LHSRange = getSignedRange(LHS);
4661 ConstantRange RHSRange = getSignedRange(RHS);
4662 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
4664 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
4668 case ICmpInst::ICMP_UGT:
4669 Pred = ICmpInst::ICMP_ULT;
4670 std::swap(LHS, RHS);
4671 case ICmpInst::ICMP_ULT: {
4672 ConstantRange LHSRange = getUnsignedRange(LHS);
4673 ConstantRange RHSRange = getUnsignedRange(RHS);
4674 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
4676 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
4680 case ICmpInst::ICMP_UGE:
4681 Pred = ICmpInst::ICMP_ULE;
4682 std::swap(LHS, RHS);
4683 case ICmpInst::ICMP_ULE: {
4684 ConstantRange LHSRange = getUnsignedRange(LHS);
4685 ConstantRange RHSRange = getUnsignedRange(RHS);
4686 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
4688 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
4692 case ICmpInst::ICMP_NE: {
4693 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
4695 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
4698 const SCEV *Diff = getMinusSCEV(LHS, RHS);
4699 if (isKnownNonZero(Diff))
4703 case ICmpInst::ICMP_EQ:
4704 // The check at the top of the function catches the case where
4705 // the values are known to be equal.
4711 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
4712 /// protected by a conditional between LHS and RHS. This is used to
4713 /// to eliminate casts.
4715 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
4716 ICmpInst::Predicate Pred,
4717 const SCEV *LHS, const SCEV *RHS) {
4718 // Interpret a null as meaning no loop, where there is obviously no guard
4719 // (interprocedural conditions notwithstanding).
4720 if (!L) return true;
4722 BasicBlock *Latch = L->getLoopLatch();
4726 BranchInst *LoopContinuePredicate =
4727 dyn_cast<BranchInst>(Latch->getTerminator());
4728 if (!LoopContinuePredicate ||
4729 LoopContinuePredicate->isUnconditional())
4732 return isImpliedCond(LoopContinuePredicate->getCondition(), Pred, LHS, RHS,
4733 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
4736 /// isLoopGuardedByCond - Test whether entry to the loop is protected
4737 /// by a conditional between LHS and RHS. This is used to help avoid max
4738 /// expressions in loop trip counts, and to eliminate casts.
4740 ScalarEvolution::isLoopGuardedByCond(const Loop *L,
4741 ICmpInst::Predicate Pred,
4742 const SCEV *LHS, const SCEV *RHS) {
4743 // Interpret a null as meaning no loop, where there is obviously no guard
4744 // (interprocedural conditions notwithstanding).
4745 if (!L) return false;
4747 BasicBlock *Predecessor = getLoopPredecessor(L);
4748 BasicBlock *PredecessorDest = L->getHeader();
4750 // Starting at the loop predecessor, climb up the predecessor chain, as long
4751 // as there are predecessors that can be found that have unique successors
4752 // leading to the original header.
4754 PredecessorDest = Predecessor,
4755 Predecessor = getPredecessorWithUniqueSuccessorForBB(Predecessor)) {
4757 BranchInst *LoopEntryPredicate =
4758 dyn_cast<BranchInst>(Predecessor->getTerminator());
4759 if (!LoopEntryPredicate ||
4760 LoopEntryPredicate->isUnconditional())
4763 if (isImpliedCond(LoopEntryPredicate->getCondition(), Pred, LHS, RHS,
4764 LoopEntryPredicate->getSuccessor(0) != PredecessorDest))
4771 /// isImpliedCond - Test whether the condition described by Pred, LHS,
4772 /// and RHS is true whenever the given Cond value evaluates to true.
4773 bool ScalarEvolution::isImpliedCond(Value *CondValue,
4774 ICmpInst::Predicate Pred,
4775 const SCEV *LHS, const SCEV *RHS,
4777 // Recursivly handle And and Or conditions.
4778 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CondValue)) {
4779 if (BO->getOpcode() == Instruction::And) {
4781 return isImpliedCond(BO->getOperand(0), Pred, LHS, RHS, Inverse) ||
4782 isImpliedCond(BO->getOperand(1), Pred, LHS, RHS, Inverse);
4783 } else if (BO->getOpcode() == Instruction::Or) {
4785 return isImpliedCond(BO->getOperand(0), Pred, LHS, RHS, Inverse) ||
4786 isImpliedCond(BO->getOperand(1), Pred, LHS, RHS, Inverse);
4790 ICmpInst *ICI = dyn_cast<ICmpInst>(CondValue);
4791 if (!ICI) return false;
4793 // Bail if the ICmp's operands' types are wider than the needed type
4794 // before attempting to call getSCEV on them. This avoids infinite
4795 // recursion, since the analysis of widening casts can require loop
4796 // exit condition information for overflow checking, which would
4798 if (getTypeSizeInBits(LHS->getType()) <
4799 getTypeSizeInBits(ICI->getOperand(0)->getType()))
4802 // Now that we found a conditional branch that dominates the loop, check to
4803 // see if it is the comparison we are looking for.
4804 ICmpInst::Predicate FoundPred;
4806 FoundPred = ICI->getInversePredicate();
4808 FoundPred = ICI->getPredicate();
4810 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
4811 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
4813 // Balance the types. The case where FoundLHS' type is wider than
4814 // LHS' type is checked for above.
4815 if (getTypeSizeInBits(LHS->getType()) >
4816 getTypeSizeInBits(FoundLHS->getType())) {
4817 if (CmpInst::isSigned(Pred)) {
4818 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
4819 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
4821 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
4822 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
4826 // Canonicalize the query to match the way instcombine will have
4827 // canonicalized the comparison.
4828 // First, put a constant operand on the right.
4829 if (isa<SCEVConstant>(LHS)) {
4830 std::swap(LHS, RHS);
4831 Pred = ICmpInst::getSwappedPredicate(Pred);
4833 // Then, canonicalize comparisons with boundary cases.
4834 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
4835 const APInt &RA = RC->getValue()->getValue();
4837 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
4838 case ICmpInst::ICMP_EQ:
4839 case ICmpInst::ICMP_NE:
4841 case ICmpInst::ICMP_UGE:
4842 if ((RA - 1).isMinValue()) {
4843 Pred = ICmpInst::ICMP_NE;
4844 RHS = getConstant(RA - 1);
4847 if (RA.isMaxValue()) {
4848 Pred = ICmpInst::ICMP_EQ;
4851 if (RA.isMinValue()) return true;
4853 case ICmpInst::ICMP_ULE:
4854 if ((RA + 1).isMaxValue()) {
4855 Pred = ICmpInst::ICMP_NE;
4856 RHS = getConstant(RA + 1);
4859 if (RA.isMinValue()) {
4860 Pred = ICmpInst::ICMP_EQ;
4863 if (RA.isMaxValue()) return true;
4865 case ICmpInst::ICMP_SGE:
4866 if ((RA - 1).isMinSignedValue()) {
4867 Pred = ICmpInst::ICMP_NE;
4868 RHS = getConstant(RA - 1);
4871 if (RA.isMaxSignedValue()) {
4872 Pred = ICmpInst::ICMP_EQ;
4875 if (RA.isMinSignedValue()) return true;
4877 case ICmpInst::ICMP_SLE:
4878 if ((RA + 1).isMaxSignedValue()) {
4879 Pred = ICmpInst::ICMP_NE;
4880 RHS = getConstant(RA + 1);
4883 if (RA.isMinSignedValue()) {
4884 Pred = ICmpInst::ICMP_EQ;
4887 if (RA.isMaxSignedValue()) return true;
4889 case ICmpInst::ICMP_UGT:
4890 if (RA.isMinValue()) {
4891 Pred = ICmpInst::ICMP_NE;
4894 if ((RA + 1).isMaxValue()) {
4895 Pred = ICmpInst::ICMP_EQ;
4896 RHS = getConstant(RA + 1);
4899 if (RA.isMaxValue()) return false;
4901 case ICmpInst::ICMP_ULT:
4902 if (RA.isMaxValue()) {
4903 Pred = ICmpInst::ICMP_NE;
4906 if ((RA - 1).isMinValue()) {
4907 Pred = ICmpInst::ICMP_EQ;
4908 RHS = getConstant(RA - 1);
4911 if (RA.isMinValue()) return false;
4913 case ICmpInst::ICMP_SGT:
4914 if (RA.isMinSignedValue()) {
4915 Pred = ICmpInst::ICMP_NE;
4918 if ((RA + 1).isMaxSignedValue()) {
4919 Pred = ICmpInst::ICMP_EQ;
4920 RHS = getConstant(RA + 1);
4923 if (RA.isMaxSignedValue()) return false;
4925 case ICmpInst::ICMP_SLT:
4926 if (RA.isMaxSignedValue()) {
4927 Pred = ICmpInst::ICMP_NE;
4930 if ((RA - 1).isMinSignedValue()) {
4931 Pred = ICmpInst::ICMP_EQ;
4932 RHS = getConstant(RA - 1);
4935 if (RA.isMinSignedValue()) return false;
4940 // Check to see if we can make the LHS or RHS match.
4941 if (LHS == FoundRHS || RHS == FoundLHS) {
4942 if (isa<SCEVConstant>(RHS)) {
4943 std::swap(FoundLHS, FoundRHS);
4944 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
4946 std::swap(LHS, RHS);
4947 Pred = ICmpInst::getSwappedPredicate(Pred);
4951 // Check whether the found predicate is the same as the desired predicate.
4952 if (FoundPred == Pred)
4953 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
4955 // Check whether swapping the found predicate makes it the same as the
4956 // desired predicate.
4957 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
4958 if (isa<SCEVConstant>(RHS))
4959 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
4961 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
4962 RHS, LHS, FoundLHS, FoundRHS);
4965 // Check whether the actual condition is beyond sufficient.
4966 if (FoundPred == ICmpInst::ICMP_EQ)
4967 if (ICmpInst::isTrueWhenEqual(Pred))
4968 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
4970 if (Pred == ICmpInst::ICMP_NE)
4971 if (!ICmpInst::isTrueWhenEqual(FoundPred))
4972 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
4975 // Otherwise assume the worst.
4979 /// isImpliedCondOperands - Test whether the condition described by Pred,
4980 /// LHS, and RHS is true whenever the condition desribed by Pred, FoundLHS,
4981 /// and FoundRHS is true.
4982 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
4983 const SCEV *LHS, const SCEV *RHS,
4984 const SCEV *FoundLHS,
4985 const SCEV *FoundRHS) {
4986 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
4987 FoundLHS, FoundRHS) ||
4988 // ~x < ~y --> x > y
4989 isImpliedCondOperandsHelper(Pred, LHS, RHS,
4990 getNotSCEV(FoundRHS),
4991 getNotSCEV(FoundLHS));
4994 /// isImpliedCondOperandsHelper - Test whether the condition described by
4995 /// Pred, LHS, and RHS is true whenever the condition desribed by Pred,
4996 /// FoundLHS, and FoundRHS is true.
4998 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
4999 const SCEV *LHS, const SCEV *RHS,
5000 const SCEV *FoundLHS,
5001 const SCEV *FoundRHS) {
5003 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5004 case ICmpInst::ICMP_EQ:
5005 case ICmpInst::ICMP_NE:
5006 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5009 case ICmpInst::ICMP_SLT:
5010 case ICmpInst::ICMP_SLE:
5011 if (isKnownPredicate(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5012 isKnownPredicate(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5015 case ICmpInst::ICMP_SGT:
5016 case ICmpInst::ICMP_SGE:
5017 if (isKnownPredicate(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5018 isKnownPredicate(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5021 case ICmpInst::ICMP_ULT:
5022 case ICmpInst::ICMP_ULE:
5023 if (isKnownPredicate(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5024 isKnownPredicate(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5027 case ICmpInst::ICMP_UGT:
5028 case ICmpInst::ICMP_UGE:
5029 if (isKnownPredicate(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5030 isKnownPredicate(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5038 /// getBECount - Subtract the end and start values and divide by the step,
5039 /// rounding up, to get the number of times the backedge is executed. Return
5040 /// CouldNotCompute if an intermediate computation overflows.
5041 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5045 assert(!isKnownNegative(Step) &&
5046 "This code doesn't handle negative strides yet!");
5048 const Type *Ty = Start->getType();
5049 const SCEV *NegOne = getIntegerSCEV(-1, Ty);
5050 const SCEV *Diff = getMinusSCEV(End, Start);
5051 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5053 // Add an adjustment to the difference between End and Start so that
5054 // the division will effectively round up.
5055 const SCEV *Add = getAddExpr(Diff, RoundUp);
5058 // Check Add for unsigned overflow.
5059 // TODO: More sophisticated things could be done here.
5060 const Type *WideTy = IntegerType::get(getContext(),
5061 getTypeSizeInBits(Ty) + 1);
5062 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5063 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5064 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5065 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5066 return getCouldNotCompute();
5069 return getUDivExpr(Add, Step);
5072 /// HowManyLessThans - Return the number of times a backedge containing the
5073 /// specified less-than comparison will execute. If not computable, return
5074 /// CouldNotCompute.
5075 ScalarEvolution::BackedgeTakenInfo
5076 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5077 const Loop *L, bool isSigned) {
5078 // Only handle: "ADDREC < LoopInvariant".
5079 if (!RHS->isLoopInvariant(L)) return getCouldNotCompute();
5081 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5082 if (!AddRec || AddRec->getLoop() != L)
5083 return getCouldNotCompute();
5085 // Check to see if we have a flag which makes analysis easy.
5086 bool NoWrap = isSigned ? AddRec->hasNoSignedWrap() :
5087 AddRec->hasNoUnsignedWrap();
5089 if (AddRec->isAffine()) {
5090 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5091 const SCEV *Step = AddRec->getStepRecurrence(*this);
5094 return getCouldNotCompute();
5095 if (Step->isOne()) {
5096 // With unit stride, the iteration never steps past the limit value.
5097 } else if (isKnownPositive(Step)) {
5098 // Test whether a positive iteration can step past the limit
5099 // value and past the maximum value for its type in a single step.
5100 // Note that it's not sufficient to check NoWrap here, because even
5101 // though the value after a wrap is undefined, it's not undefined
5102 // behavior, so if wrap does occur, the loop could either terminate or
5103 // loop infinitely, but in either case, the loop is guaranteed to
5104 // iterate at least until the iteration where the wrapping occurs.
5105 const SCEV *One = getIntegerSCEV(1, Step->getType());
5107 APInt Max = APInt::getSignedMaxValue(BitWidth);
5108 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5109 .slt(getSignedRange(RHS).getSignedMax()))
5110 return getCouldNotCompute();
5112 APInt Max = APInt::getMaxValue(BitWidth);
5113 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5114 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5115 return getCouldNotCompute();
5118 // TODO: Handle negative strides here and below.
5119 return getCouldNotCompute();
5121 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5122 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5123 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5124 // treat m-n as signed nor unsigned due to overflow possibility.
5126 // First, we get the value of the LHS in the first iteration: n
5127 const SCEV *Start = AddRec->getOperand(0);
5129 // Determine the minimum constant start value.
5130 const SCEV *MinStart = getConstant(isSigned ?
5131 getSignedRange(Start).getSignedMin() :
5132 getUnsignedRange(Start).getUnsignedMin());
5134 // If we know that the condition is true in order to enter the loop,
5135 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5136 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5137 // the division must round up.
5138 const SCEV *End = RHS;
5139 if (!isLoopGuardedByCond(L,
5140 isSigned ? ICmpInst::ICMP_SLT :
5142 getMinusSCEV(Start, Step), RHS))
5143 End = isSigned ? getSMaxExpr(RHS, Start)
5144 : getUMaxExpr(RHS, Start);
5146 // Determine the maximum constant end value.
5147 const SCEV *MaxEnd = getConstant(isSigned ?
5148 getSignedRange(End).getSignedMax() :
5149 getUnsignedRange(End).getUnsignedMax());
5151 // If MaxEnd is within a step of the maximum integer value in its type,
5152 // adjust it down to the minimum value which would produce the same effect.
5153 // This allows the subsequent ceiling divison of (N+(step-1))/step to
5154 // compute the correct value.
5155 const SCEV *StepMinusOne = getMinusSCEV(Step,
5156 getIntegerSCEV(1, Step->getType()));
5159 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5162 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5165 // Finally, we subtract these two values and divide, rounding up, to get
5166 // the number of times the backedge is executed.
5167 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5169 // The maximum backedge count is similar, except using the minimum start
5170 // value and the maximum end value.
5171 const SCEV *MaxBECount = getBECount(MinStart, MaxEnd, Step, NoWrap);
5173 return BackedgeTakenInfo(BECount, MaxBECount);
5176 return getCouldNotCompute();
5179 /// getNumIterationsInRange - Return the number of iterations of this loop that
5180 /// produce values in the specified constant range. Another way of looking at
5181 /// this is that it returns the first iteration number where the value is not in
5182 /// the condition, thus computing the exit count. If the iteration count can't
5183 /// be computed, an instance of SCEVCouldNotCompute is returned.
5184 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5185 ScalarEvolution &SE) const {
5186 if (Range.isFullSet()) // Infinite loop.
5187 return SE.getCouldNotCompute();
5189 // If the start is a non-zero constant, shift the range to simplify things.
5190 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5191 if (!SC->getValue()->isZero()) {
5192 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5193 Operands[0] = SE.getIntegerSCEV(0, SC->getType());
5194 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop());
5195 if (const SCEVAddRecExpr *ShiftedAddRec =
5196 dyn_cast<SCEVAddRecExpr>(Shifted))
5197 return ShiftedAddRec->getNumIterationsInRange(
5198 Range.subtract(SC->getValue()->getValue()), SE);
5199 // This is strange and shouldn't happen.
5200 return SE.getCouldNotCompute();
5203 // The only time we can solve this is when we have all constant indices.
5204 // Otherwise, we cannot determine the overflow conditions.
5205 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5206 if (!isa<SCEVConstant>(getOperand(i)))
5207 return SE.getCouldNotCompute();
5210 // Okay at this point we know that all elements of the chrec are constants and
5211 // that the start element is zero.
5213 // First check to see if the range contains zero. If not, the first
5215 unsigned BitWidth = SE.getTypeSizeInBits(getType());
5216 if (!Range.contains(APInt(BitWidth, 0)))
5217 return SE.getIntegerSCEV(0, getType());
5220 // If this is an affine expression then we have this situation:
5221 // Solve {0,+,A} in Range === Ax in Range
5223 // We know that zero is in the range. If A is positive then we know that
5224 // the upper value of the range must be the first possible exit value.
5225 // If A is negative then the lower of the range is the last possible loop
5226 // value. Also note that we already checked for a full range.
5227 APInt One(BitWidth,1);
5228 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
5229 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
5231 // The exit value should be (End+A)/A.
5232 APInt ExitVal = (End + A).udiv(A);
5233 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
5235 // Evaluate at the exit value. If we really did fall out of the valid
5236 // range, then we computed our trip count, otherwise wrap around or other
5237 // things must have happened.
5238 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
5239 if (Range.contains(Val->getValue()))
5240 return SE.getCouldNotCompute(); // Something strange happened
5242 // Ensure that the previous value is in the range. This is a sanity check.
5243 assert(Range.contains(
5244 EvaluateConstantChrecAtConstant(this,
5245 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
5246 "Linear scev computation is off in a bad way!");
5247 return SE.getConstant(ExitValue);
5248 } else if (isQuadratic()) {
5249 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
5250 // quadratic equation to solve it. To do this, we must frame our problem in
5251 // terms of figuring out when zero is crossed, instead of when
5252 // Range.getUpper() is crossed.
5253 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
5254 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
5255 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
5257 // Next, solve the constructed addrec
5258 std::pair<const SCEV *,const SCEV *> Roots =
5259 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
5260 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5261 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5263 // Pick the smallest positive root value.
5264 if (ConstantInt *CB =
5265 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
5266 R1->getValue(), R2->getValue()))) {
5267 if (CB->getZExtValue() == false)
5268 std::swap(R1, R2); // R1 is the minimum root now.
5270 // Make sure the root is not off by one. The returned iteration should
5271 // not be in the range, but the previous one should be. When solving
5272 // for "X*X < 5", for example, we should not return a root of 2.
5273 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
5276 if (Range.contains(R1Val->getValue())) {
5277 // The next iteration must be out of the range...
5278 ConstantInt *NextVal =
5279 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
5281 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5282 if (!Range.contains(R1Val->getValue()))
5283 return SE.getConstant(NextVal);
5284 return SE.getCouldNotCompute(); // Something strange happened
5287 // If R1 was not in the range, then it is a good return value. Make
5288 // sure that R1-1 WAS in the range though, just in case.
5289 ConstantInt *NextVal =
5290 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
5291 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5292 if (Range.contains(R1Val->getValue()))
5294 return SE.getCouldNotCompute(); // Something strange happened
5299 return SE.getCouldNotCompute();
5304 //===----------------------------------------------------------------------===//
5305 // SCEVCallbackVH Class Implementation
5306 //===----------------------------------------------------------------------===//
5308 void ScalarEvolution::SCEVCallbackVH::deleted() {
5309 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5310 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
5311 SE->ConstantEvolutionLoopExitValue.erase(PN);
5312 SE->Scalars.erase(getValPtr());
5313 // this now dangles!
5316 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *) {
5317 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5319 // Forget all the expressions associated with users of the old value,
5320 // so that future queries will recompute the expressions using the new
5322 SmallVector<User *, 16> Worklist;
5323 SmallPtrSet<User *, 8> Visited;
5324 Value *Old = getValPtr();
5325 bool DeleteOld = false;
5326 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
5328 Worklist.push_back(*UI);
5329 while (!Worklist.empty()) {
5330 User *U = Worklist.pop_back_val();
5331 // Deleting the Old value will cause this to dangle. Postpone
5332 // that until everything else is done.
5337 if (!Visited.insert(U))
5339 if (PHINode *PN = dyn_cast<PHINode>(U))
5340 SE->ConstantEvolutionLoopExitValue.erase(PN);
5341 SE->Scalars.erase(U);
5342 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
5344 Worklist.push_back(*UI);
5346 // Delete the Old value if it (indirectly) references itself.
5348 if (PHINode *PN = dyn_cast<PHINode>(Old))
5349 SE->ConstantEvolutionLoopExitValue.erase(PN);
5350 SE->Scalars.erase(Old);
5351 // this now dangles!
5356 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
5357 : CallbackVH(V), SE(se) {}
5359 //===----------------------------------------------------------------------===//
5360 // ScalarEvolution Class Implementation
5361 //===----------------------------------------------------------------------===//
5363 ScalarEvolution::ScalarEvolution()
5364 : FunctionPass(&ID) {
5367 bool ScalarEvolution::runOnFunction(Function &F) {
5369 LI = &getAnalysis<LoopInfo>();
5370 DT = &getAnalysis<DominatorTree>();
5371 TD = getAnalysisIfAvailable<TargetData>();
5375 void ScalarEvolution::releaseMemory() {
5377 BackedgeTakenCounts.clear();
5378 ConstantEvolutionLoopExitValue.clear();
5379 ValuesAtScopes.clear();
5380 UniqueSCEVs.clear();
5381 SCEVAllocator.Reset();
5384 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
5385 AU.setPreservesAll();
5386 AU.addRequiredTransitive<LoopInfo>();
5387 AU.addRequiredTransitive<DominatorTree>();
5390 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
5391 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
5394 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
5396 // Print all inner loops first
5397 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
5398 PrintLoopInfo(OS, SE, *I);
5401 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5404 SmallVector<BasicBlock *, 8> ExitBlocks;
5405 L->getExitBlocks(ExitBlocks);
5406 if (ExitBlocks.size() != 1)
5407 OS << "<multiple exits> ";
5409 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
5410 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
5412 OS << "Unpredictable backedge-taken count. ";
5417 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5420 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
5421 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
5423 OS << "Unpredictable max backedge-taken count. ";
5429 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
5430 // ScalarEvolution's implementaiton of the print method is to print
5431 // out SCEV values of all instructions that are interesting. Doing
5432 // this potentially causes it to create new SCEV objects though,
5433 // which technically conflicts with the const qualifier. This isn't
5434 // observable from outside the class though, so casting away the
5435 // const isn't dangerous.
5436 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
5438 OS << "Classifying expressions for: ";
5439 WriteAsOperand(OS, F, /*PrintType=*/false);
5441 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
5442 if (isSCEVable(I->getType())) {
5445 const SCEV *SV = SE.getSCEV(&*I);
5448 const Loop *L = LI->getLoopFor((*I).getParent());
5450 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
5457 OS << "\t\t" "Exits: ";
5458 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
5459 if (!ExitValue->isLoopInvariant(L)) {
5460 OS << "<<Unknown>>";
5469 OS << "Determining loop execution counts for: ";
5470 WriteAsOperand(OS, F, /*PrintType=*/false);
5472 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
5473 PrintLoopInfo(OS, &SE, *I);