1 //===- LoopStrengthReduce.cpp - Strength Reduce GEPs in Loops -------------===//
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 pass performs a strength reduction on array references inside loops that
11 // have as one or more of their components the loop induction variable. This is
12 // accomplished by creating a new Value to hold the initial value of the array
13 // access for the first iteration, and then creating a new GEP instruction in
14 // the loop to increment the value by the appropriate amount.
16 //===----------------------------------------------------------------------===//
18 #define DEBUG_TYPE "loop-reduce"
19 #include "llvm/Transforms/Scalar.h"
20 #include "llvm/Constants.h"
21 #include "llvm/Instructions.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/Type.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Analysis/Dominators.h"
26 #include "llvm/Analysis/LoopInfo.h"
27 #include "llvm/Analysis/LoopPass.h"
28 #include "llvm/Analysis/ScalarEvolutionExpander.h"
29 #include "llvm/Support/CFG.h"
30 #include "llvm/Support/GetElementPtrTypeIterator.h"
31 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
32 #include "llvm/Transforms/Utils/Local.h"
33 #include "llvm/Target/TargetData.h"
34 #include "llvm/ADT/SmallPtrSet.h"
35 #include "llvm/ADT/Statistic.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/Compiler.h"
38 #include "llvm/Target/TargetLowering.h"
43 STATISTIC(NumReduced , "Number of GEPs strength reduced");
44 STATISTIC(NumInserted, "Number of PHIs inserted");
45 STATISTIC(NumVariable, "Number of PHIs with variable strides");
46 STATISTIC(NumEliminated, "Number of strides eliminated");
47 STATISTIC(NumShadow, "Number of Shadow IVs optimized");
53 /// IVStrideUse - Keep track of one use of a strided induction variable, where
54 /// the stride is stored externally. The Offset member keeps track of the
55 /// offset from the IV, User is the actual user of the operand, and
56 /// 'OperandValToReplace' is the operand of the User that is the use.
57 struct VISIBILITY_HIDDEN IVStrideUse {
60 Value *OperandValToReplace;
62 // isUseOfPostIncrementedValue - True if this should use the
63 // post-incremented version of this IV, not the preincremented version.
64 // This can only be set in special cases, such as the terminating setcc
65 // instruction for a loop or uses dominated by the loop.
66 bool isUseOfPostIncrementedValue;
68 IVStrideUse(const SCEVHandle &Offs, Instruction *U, Value *O)
69 : Offset(Offs), User(U), OperandValToReplace(O),
70 isUseOfPostIncrementedValue(false) {}
73 /// IVUsersOfOneStride - This structure keeps track of all instructions that
74 /// have an operand that is based on the trip count multiplied by some stride.
75 /// The stride for all of these users is common and kept external to this
77 struct VISIBILITY_HIDDEN IVUsersOfOneStride {
78 /// Users - Keep track of all of the users of this stride as well as the
79 /// initial value and the operand that uses the IV.
80 std::vector<IVStrideUse> Users;
82 void addUser(const SCEVHandle &Offset,Instruction *User, Value *Operand) {
83 Users.push_back(IVStrideUse(Offset, User, Operand));
87 /// IVInfo - This structure keeps track of one IV expression inserted during
88 /// StrengthReduceStridedIVUsers. It contains the stride, the common base, as
89 /// well as the PHI node and increment value created for rewrite.
90 struct VISIBILITY_HIDDEN IVExpr {
96 IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
98 : Stride(stride), Base(base), PHI(phi), IncV(incv) {}
101 /// IVsOfOneStride - This structure keeps track of all IV expression inserted
102 /// during StrengthReduceStridedIVUsers for a particular stride of the IV.
103 struct VISIBILITY_HIDDEN IVsOfOneStride {
104 std::vector<IVExpr> IVs;
106 void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI,
108 IVs.push_back(IVExpr(Stride, Base, PHI, IncV));
112 class VISIBILITY_HIDDEN LoopStrengthReduce : public LoopPass {
116 const TargetData *TD;
117 const Type *UIntPtrTy;
120 /// IVUsesByStride - Keep track of all uses of induction variables that we
121 /// are interested in. The key of the map is the stride of the access.
122 std::map<SCEVHandle, IVUsersOfOneStride> IVUsesByStride;
124 /// IVsByStride - Keep track of all IVs that have been inserted for a
125 /// particular stride.
126 std::map<SCEVHandle, IVsOfOneStride> IVsByStride;
128 /// StrideOrder - An ordering of the keys in IVUsesByStride that is stable:
129 /// We use this to iterate over the IVUsesByStride collection without being
130 /// dependent on random ordering of pointers in the process.
131 SmallVector<SCEVHandle, 16> StrideOrder;
133 /// GEPlist - A list of the GEP's that have been remembered in the SCEV
134 /// data structures. SCEV does not know to update these when the operands
135 /// of the GEP are changed, which means we cannot leave them live across
137 SmallVector<GetElementPtrInst *, 16> GEPlist;
139 /// CastedValues - As we need to cast values to uintptr_t, this keeps track
140 /// of the casted version of each value. This is accessed by
141 /// getCastedVersionOf.
142 DenseMap<Value*, Value*> CastedPointers;
144 /// DeadInsts - Keep track of instructions we may have made dead, so that
145 /// we can remove them after we are done working.
146 SmallVector<Instruction*, 16> DeadInsts;
148 /// TLI - Keep a pointer of a TargetLowering to consult for determining
149 /// transformation profitability.
150 const TargetLowering *TLI;
153 static char ID; // Pass ID, replacement for typeid
154 explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
155 LoopPass(&ID), TLI(tli) {
158 bool runOnLoop(Loop *L, LPPassManager &LPM);
160 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
161 // We split critical edges, so we change the CFG. However, we do update
162 // many analyses if they are around.
163 AU.addPreservedID(LoopSimplifyID);
164 AU.addPreserved<LoopInfo>();
165 AU.addPreserved<DominanceFrontier>();
166 AU.addPreserved<DominatorTree>();
168 AU.addRequiredID(LoopSimplifyID);
169 AU.addRequired<LoopInfo>();
170 AU.addRequired<DominatorTree>();
171 AU.addRequired<TargetData>();
172 AU.addRequired<ScalarEvolution>();
173 AU.addPreserved<ScalarEvolution>();
176 /// getCastedVersionOf - Return the specified value casted to uintptr_t.
178 Value *getCastedVersionOf(Instruction::CastOps opcode, Value *V);
180 bool AddUsersIfInteresting(Instruction *I, Loop *L,
181 SmallPtrSet<Instruction*,16> &Processed);
182 SCEVHandle GetExpressionSCEV(Instruction *E);
183 ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
184 IVStrideUse* &CondUse,
185 const SCEVHandle* &CondStride);
186 void OptimizeIndvars(Loop *L);
188 /// OptimizeShadowIV - If IV is used in a int-to-float cast
189 /// inside the loop then try to eliminate the cast opeation.
190 void OptimizeShadowIV(Loop *L);
192 /// OptimizeSMax - Rewrite the loop's terminating condition
193 /// if it uses an smax computation.
194 ICmpInst *OptimizeSMax(Loop *L, ICmpInst *Cond,
195 IVStrideUse* &CondUse);
197 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
198 const SCEVHandle *&CondStride);
199 bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
200 SCEVHandle CheckForIVReuse(bool, bool, bool, const SCEVHandle&,
201 IVExpr&, const Type*,
202 const std::vector<BasedUser>& UsersToProcess);
203 bool ValidStride(bool, int64_t,
204 const std::vector<BasedUser>& UsersToProcess);
205 SCEVHandle CollectIVUsers(const SCEVHandle &Stride,
206 IVUsersOfOneStride &Uses,
208 bool &AllUsesAreAddresses,
209 bool &AllUsesAreOutsideLoop,
210 std::vector<BasedUser> &UsersToProcess);
211 void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
212 IVUsersOfOneStride &Uses,
213 Loop *L, bool isOnlyStride);
214 void DeleteTriviallyDeadInstructions();
218 char LoopStrengthReduce::ID = 0;
219 static RegisterPass<LoopStrengthReduce>
220 X("loop-reduce", "Loop Strength Reduction");
222 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
223 return new LoopStrengthReduce(TLI);
226 /// getCastedVersionOf - Return the specified value casted to uintptr_t. This
227 /// assumes that the Value* V is of integer or pointer type only.
229 Value *LoopStrengthReduce::getCastedVersionOf(Instruction::CastOps opcode,
231 if (V->getType() == UIntPtrTy) return V;
232 if (Constant *CB = dyn_cast<Constant>(V))
233 return ConstantExpr::getCast(opcode, CB, UIntPtrTy);
235 Value *&New = CastedPointers[V];
238 New = SCEVExpander::InsertCastOfTo(opcode, V, UIntPtrTy);
239 DeadInsts.push_back(cast<Instruction>(New));
244 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
245 /// specified set are trivially dead, delete them and see if this makes any of
246 /// their operands subsequently dead.
247 void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
248 if (DeadInsts.empty()) return;
250 // Sort the deadinsts list so that we can trivially eliminate duplicates as we
251 // go. The code below never adds a non-dead instruction to the worklist, but
252 // callers may not be so careful.
253 array_pod_sort(DeadInsts.begin(), DeadInsts.end());
255 // Drop duplicate instructions and those with uses.
256 for (unsigned i = 0, e = DeadInsts.size()-1; i < e; ++i) {
257 Instruction *I = DeadInsts[i];
258 if (!I->use_empty()) DeadInsts[i] = 0;
259 while (i != e && DeadInsts[i+1] == I)
263 while (!DeadInsts.empty()) {
264 Instruction *I = DeadInsts.back();
265 DeadInsts.pop_back();
267 if (I == 0 || !isInstructionTriviallyDead(I))
270 SE->deleteValueFromRecords(I);
272 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) {
273 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
276 DeadInsts.push_back(U);
280 I->eraseFromParent();
286 /// GetExpressionSCEV - Compute and return the SCEV for the specified
288 SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp) {
289 // Pointer to pointer bitcast instructions return the same value as their
291 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Exp)) {
292 if (SE->hasSCEV(BCI) || !isa<Instruction>(BCI->getOperand(0)))
293 return SE->getSCEV(BCI);
294 SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)));
299 // Scalar Evolutions doesn't know how to compute SCEV's for GEP instructions.
300 // If this is a GEP that SE doesn't know about, compute it now and insert it.
301 // If this is not a GEP, or if we have already done this computation, just let
303 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Exp);
304 if (!GEP || SE->hasSCEV(GEP))
305 return SE->getSCEV(Exp);
307 // Analyze all of the subscripts of this getelementptr instruction, looking
308 // for uses that are determined by the trip count of the loop. First, skip
309 // all operands the are not dependent on the IV.
311 // Build up the base expression. Insert an LLVM cast of the pointer to
313 SCEVHandle GEPVal = SE->getUnknown(
314 getCastedVersionOf(Instruction::PtrToInt, GEP->getOperand(0)));
316 gep_type_iterator GTI = gep_type_begin(GEP);
318 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
319 i != e; ++i, ++GTI) {
320 // If this is a use of a recurrence that we can analyze, and it comes before
321 // Op does in the GEP operand list, we will handle this when we process this
323 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
324 const StructLayout *SL = TD->getStructLayout(STy);
325 unsigned Idx = cast<ConstantInt>(*i)->getZExtValue();
326 uint64_t Offset = SL->getElementOffset(Idx);
327 GEPVal = SE->getAddExpr(GEPVal,
328 SE->getIntegerSCEV(Offset, UIntPtrTy));
330 unsigned GEPOpiBits =
331 (*i)->getType()->getPrimitiveSizeInBits();
332 unsigned IntPtrBits = UIntPtrTy->getPrimitiveSizeInBits();
333 Instruction::CastOps opcode = (GEPOpiBits < IntPtrBits ?
334 Instruction::SExt : (GEPOpiBits > IntPtrBits ? Instruction::Trunc :
335 Instruction::BitCast));
336 Value *OpVal = getCastedVersionOf(opcode, *i);
337 SCEVHandle Idx = SE->getSCEV(OpVal);
339 uint64_t TypeSize = TD->getTypePaddedSize(GTI.getIndexedType());
341 Idx = SE->getMulExpr(Idx,
342 SE->getConstant(ConstantInt::get(UIntPtrTy,
344 GEPVal = SE->getAddExpr(GEPVal, Idx);
348 SE->setSCEV(GEP, GEPVal);
349 GEPlist.push_back(GEP);
353 /// containsAddRecFromDifferentLoop - Determine whether expression S involves a
354 /// subexpression that is an AddRec from a loop other than L. An outer loop
355 /// of L is OK, but not an inner loop nor a disjoint loop.
356 static bool containsAddRecFromDifferentLoop(SCEVHandle S, Loop *L) {
357 // This is very common, put it first.
358 if (isa<SCEVConstant>(S))
360 if (SCEVCommutativeExpr *AE = dyn_cast<SCEVCommutativeExpr>(S)) {
361 for (unsigned int i=0; i< AE->getNumOperands(); i++)
362 if (containsAddRecFromDifferentLoop(AE->getOperand(i), L))
366 if (SCEVAddRecExpr *AE = dyn_cast<SCEVAddRecExpr>(S)) {
367 if (const Loop *newLoop = AE->getLoop()) {
370 // if newLoop is an outer loop of L, this is OK.
371 if (!LoopInfoBase<BasicBlock>::isNotAlreadyContainedIn(L, newLoop))
376 if (SCEVUDivExpr *DE = dyn_cast<SCEVUDivExpr>(S))
377 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
378 containsAddRecFromDifferentLoop(DE->getRHS(), L);
380 // SCEVSDivExpr has been backed out temporarily, but will be back; we'll
381 // need this when it is.
382 if (SCEVSDivExpr *DE = dyn_cast<SCEVSDivExpr>(S))
383 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
384 containsAddRecFromDifferentLoop(DE->getRHS(), L);
386 if (SCEVTruncateExpr *TE = dyn_cast<SCEVTruncateExpr>(S))
387 return containsAddRecFromDifferentLoop(TE->getOperand(), L);
388 if (SCEVZeroExtendExpr *ZE = dyn_cast<SCEVZeroExtendExpr>(S))
389 return containsAddRecFromDifferentLoop(ZE->getOperand(), L);
390 if (SCEVSignExtendExpr *SE = dyn_cast<SCEVSignExtendExpr>(S))
391 return containsAddRecFromDifferentLoop(SE->getOperand(), L);
395 /// getSCEVStartAndStride - Compute the start and stride of this expression,
396 /// returning false if the expression is not a start/stride pair, or true if it
397 /// is. The stride must be a loop invariant expression, but the start may be
398 /// a mix of loop invariant and loop variant expressions. The start cannot,
399 /// however, contain an AddRec from a different loop, unless that loop is an
400 /// outer loop of the current loop.
401 static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
402 SCEVHandle &Start, SCEVHandle &Stride,
403 ScalarEvolution *SE, DominatorTree *DT) {
404 SCEVHandle TheAddRec = Start; // Initialize to zero.
406 // If the outer level is an AddExpr, the operands are all start values except
407 // for a nested AddRecExpr.
408 if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
409 for (unsigned i = 0, e = AE->getNumOperands(); i != e; ++i)
410 if (SCEVAddRecExpr *AddRec =
411 dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
412 if (AddRec->getLoop() == L)
413 TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
415 return false; // Nested IV of some sort?
417 Start = SE->getAddExpr(Start, AE->getOperand(i));
420 } else if (isa<SCEVAddRecExpr>(SH)) {
423 return false; // not analyzable.
426 SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
427 if (!AddRec || AddRec->getLoop() != L) return false;
429 // FIXME: Generalize to non-affine IV's.
430 if (!AddRec->isAffine()) return false;
432 // If Start contains an SCEVAddRecExpr from a different loop, other than an
433 // outer loop of the current loop, reject it. SCEV has no concept of
434 // operating on one loop at a time so don't confuse it with such expressions.
435 if (containsAddRecFromDifferentLoop(AddRec->getOperand(0), L))
438 Start = SE->getAddExpr(Start, AddRec->getOperand(0));
440 if (!isa<SCEVConstant>(AddRec->getOperand(1))) {
441 // If stride is an instruction, make sure it dominates the loop preheader.
442 // Otherwise we could end up with a use before def situation.
443 BasicBlock *Preheader = L->getLoopPreheader();
444 if (!AddRec->getOperand(1)->dominates(Preheader, DT))
447 DOUT << "[" << L->getHeader()->getName()
448 << "] Variable stride: " << *AddRec << "\n";
451 Stride = AddRec->getOperand(1);
455 /// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
456 /// and now we need to decide whether the user should use the preinc or post-inc
457 /// value. If this user should use the post-inc version of the IV, return true.
459 /// Choosing wrong here can break dominance properties (if we choose to use the
460 /// post-inc value when we cannot) or it can end up adding extra live-ranges to
461 /// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
462 /// should use the post-inc value).
463 static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
464 Loop *L, DominatorTree *DT, Pass *P,
465 SmallVectorImpl<Instruction*> &DeadInsts){
466 // If the user is in the loop, use the preinc value.
467 if (L->contains(User->getParent())) return false;
469 BasicBlock *LatchBlock = L->getLoopLatch();
471 // Ok, the user is outside of the loop. If it is dominated by the latch
472 // block, use the post-inc value.
473 if (DT->dominates(LatchBlock, User->getParent()))
476 // There is one case we have to be careful of: PHI nodes. These little guys
477 // can live in blocks that do not dominate the latch block, but (since their
478 // uses occur in the predecessor block, not the block the PHI lives in) should
479 // still use the post-inc value. Check for this case now.
480 PHINode *PN = dyn_cast<PHINode>(User);
481 if (!PN) return false; // not a phi, not dominated by latch block.
483 // Look at all of the uses of IV by the PHI node. If any use corresponds to
484 // a block that is not dominated by the latch block, give up and use the
485 // preincremented value.
486 unsigned NumUses = 0;
487 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
488 if (PN->getIncomingValue(i) == IV) {
490 if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
494 // Okay, all uses of IV by PN are in predecessor blocks that really are
495 // dominated by the latch block. Split the critical edges and use the
496 // post-incremented value.
497 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
498 if (PN->getIncomingValue(i) == IV) {
499 SplitCriticalEdge(PN->getIncomingBlock(i), PN->getParent(), P, false);
500 // Splitting the critical edge can reduce the number of entries in this
502 e = PN->getNumIncomingValues();
503 if (--NumUses == 0) break;
506 // PHI node might have become a constant value after SplitCriticalEdge.
507 DeadInsts.push_back(User);
512 /// isAddressUse - Returns true if the specified instruction is using the
513 /// specified value as an address.
514 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
515 bool isAddress = isa<LoadInst>(Inst);
516 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
517 if (SI->getOperand(1) == OperandVal)
519 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
520 // Addressing modes can also be folded into prefetches and a variety
522 switch (II->getIntrinsicID()) {
524 case Intrinsic::prefetch:
525 case Intrinsic::x86_sse2_loadu_dq:
526 case Intrinsic::x86_sse2_loadu_pd:
527 case Intrinsic::x86_sse_loadu_ps:
528 case Intrinsic::x86_sse_storeu_ps:
529 case Intrinsic::x86_sse2_storeu_pd:
530 case Intrinsic::x86_sse2_storeu_dq:
531 case Intrinsic::x86_sse2_storel_dq:
532 if (II->getOperand(1) == OperandVal)
540 /// AddUsersIfInteresting - Inspect the specified instruction. If it is a
541 /// reducible SCEV, recursively add its users to the IVUsesByStride set and
542 /// return true. Otherwise, return false.
543 bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
544 SmallPtrSet<Instruction*,16> &Processed) {
545 if (!I->getType()->isInteger() && !isa<PointerType>(I->getType()))
546 return false; // Void and FP expressions cannot be reduced.
547 if (!Processed.insert(I))
548 return true; // Instruction already handled.
550 // Get the symbolic expression for this instruction.
551 SCEVHandle ISE = GetExpressionSCEV(I);
552 if (isa<SCEVCouldNotCompute>(ISE)) return false;
554 // Get the start and stride for this expression.
555 SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());
556 SCEVHandle Stride = Start;
557 if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE, DT))
558 return false; // Non-reducible symbolic expression, bail out.
560 std::vector<Instruction *> IUsers;
561 // Collect all I uses now because IVUseShouldUsePostIncValue may
562 // invalidate use_iterator.
563 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; ++UI)
564 IUsers.push_back(cast<Instruction>(*UI));
566 for (unsigned iused_index = 0, iused_size = IUsers.size();
567 iused_index != iused_size; ++iused_index) {
569 Instruction *User = IUsers[iused_index];
571 // Do not infinitely recurse on PHI nodes.
572 if (isa<PHINode>(User) && Processed.count(User))
575 // Descend recursively, but not into PHI nodes outside the current loop.
576 // It's important to see the entire expression outside the loop to get
577 // choices that depend on addressing mode use right, although we won't
578 // consider references ouside the loop in all cases.
579 // If User is already in Processed, we don't want to recurse into it again,
580 // but do want to record a second reference in the same instruction.
581 bool AddUserToIVUsers = false;
582 if (LI->getLoopFor(User->getParent()) != L) {
583 if (isa<PHINode>(User) || Processed.count(User) ||
584 !AddUsersIfInteresting(User, L, Processed)) {
585 DOUT << "FOUND USER in other loop: " << *User
586 << " OF SCEV: " << *ISE << "\n";
587 AddUserToIVUsers = true;
589 } else if (Processed.count(User) ||
590 !AddUsersIfInteresting(User, L, Processed)) {
591 DOUT << "FOUND USER: " << *User
592 << " OF SCEV: " << *ISE << "\n";
593 AddUserToIVUsers = true;
596 if (AddUserToIVUsers) {
597 IVUsersOfOneStride &StrideUses = IVUsesByStride[Stride];
598 if (StrideUses.Users.empty()) // First occurrence of this stride?
599 StrideOrder.push_back(Stride);
601 // Okay, we found a user that we cannot reduce. Analyze the instruction
602 // and decide what to do with it. If we are a use inside of the loop, use
603 // the value before incrementation, otherwise use it after incrementation.
604 if (IVUseShouldUsePostIncValue(User, I, L, DT, this, DeadInsts)) {
605 // The value used will be incremented by the stride more than we are
606 // expecting, so subtract this off.
607 SCEVHandle NewStart = SE->getMinusSCEV(Start, Stride);
608 StrideUses.addUser(NewStart, User, I);
609 StrideUses.Users.back().isUseOfPostIncrementedValue = true;
610 DOUT << " USING POSTINC SCEV, START=" << *NewStart<< "\n";
612 StrideUses.addUser(Start, User, I);
620 /// BasedUser - For a particular base value, keep information about how we've
621 /// partitioned the expression so far.
623 /// SE - The current ScalarEvolution object.
626 /// Base - The Base value for the PHI node that needs to be inserted for
627 /// this use. As the use is processed, information gets moved from this
628 /// field to the Imm field (below). BasedUser values are sorted by this
632 /// Inst - The instruction using the induction variable.
635 /// OperandValToReplace - The operand value of Inst to replace with the
637 Value *OperandValToReplace;
639 /// Imm - The immediate value that should be added to the base immediately
640 /// before Inst, because it will be folded into the imm field of the
644 // isUseOfPostIncrementedValue - True if this should use the
645 // post-incremented version of this IV, not the preincremented version.
646 // This can only be set in special cases, such as the terminating setcc
647 // instruction for a loop and uses outside the loop that are dominated by
649 bool isUseOfPostIncrementedValue;
651 BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
652 : SE(se), Base(IVSU.Offset), Inst(IVSU.User),
653 OperandValToReplace(IVSU.OperandValToReplace),
654 Imm(SE->getIntegerSCEV(0, Base->getType())),
655 isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue) {}
657 // Once we rewrite the code to insert the new IVs we want, update the
658 // operands of Inst to use the new expression 'NewBase', with 'Imm' added
660 void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
661 Instruction *InsertPt,
662 SCEVExpander &Rewriter, Loop *L, Pass *P,
663 SmallVectorImpl<Instruction*> &DeadInsts);
665 Value *InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
666 SCEVExpander &Rewriter,
667 Instruction *IP, Loop *L);
672 void BasedUser::dump() const {
673 cerr << " Base=" << *Base;
674 cerr << " Imm=" << *Imm;
675 cerr << " Inst: " << *Inst;
678 Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
679 SCEVExpander &Rewriter,
680 Instruction *IP, Loop *L) {
681 // Figure out where we *really* want to insert this code. In particular, if
682 // the user is inside of a loop that is nested inside of L, we really don't
683 // want to insert this expression before the user, we'd rather pull it out as
684 // many loops as possible.
685 LoopInfo &LI = Rewriter.getLoopInfo();
686 Instruction *BaseInsertPt = IP;
688 // Figure out the most-nested loop that IP is in.
689 Loop *InsertLoop = LI.getLoopFor(IP->getParent());
691 // If InsertLoop is not L, and InsertLoop is nested inside of L, figure out
692 // the preheader of the outer-most loop where NewBase is not loop invariant.
693 if (L->contains(IP->getParent()))
694 while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
695 BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
696 InsertLoop = InsertLoop->getParentLoop();
699 Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
701 // If there is no immediate value, skip the next part.
705 // If we are inserting the base and imm values in the same block, make sure to
706 // adjust the IP position if insertion reused a result.
707 if (IP == BaseInsertPt)
708 IP = Rewriter.getInsertionPoint();
710 // Always emit the immediate (if non-zero) into the same block as the user.
711 SCEVHandle NewValSCEV = SE->getAddExpr(SE->getUnknown(Base), Imm);
712 return Rewriter.expandCodeFor(NewValSCEV, IP);
717 // Once we rewrite the code to insert the new IVs we want, update the
718 // operands of Inst to use the new expression 'NewBase', with 'Imm' added
719 // to it. NewBasePt is the last instruction which contributes to the
720 // value of NewBase in the case that it's a diffferent instruction from
721 // the PHI that NewBase is computed from, or null otherwise.
723 void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
724 Instruction *NewBasePt,
725 SCEVExpander &Rewriter, Loop *L, Pass *P,
726 SmallVectorImpl<Instruction*> &DeadInsts){
727 if (!isa<PHINode>(Inst)) {
728 // By default, insert code at the user instruction.
729 BasicBlock::iterator InsertPt = Inst;
731 // However, if the Operand is itself an instruction, the (potentially
732 // complex) inserted code may be shared by many users. Because of this, we
733 // want to emit code for the computation of the operand right before its old
734 // computation. This is usually safe, because we obviously used to use the
735 // computation when it was computed in its current block. However, in some
736 // cases (e.g. use of a post-incremented induction variable) the NewBase
737 // value will be pinned to live somewhere after the original computation.
738 // In this case, we have to back off.
740 // If this is a use outside the loop (which means after, since it is based
741 // on a loop indvar) we use the post-incremented value, so that we don't
742 // artificially make the preinc value live out the bottom of the loop.
743 if (!isUseOfPostIncrementedValue && L->contains(Inst->getParent())) {
744 if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
745 InsertPt = NewBasePt;
747 } else if (Instruction *OpInst
748 = dyn_cast<Instruction>(OperandValToReplace)) {
750 while (isa<PHINode>(InsertPt)) ++InsertPt;
753 Value *NewVal = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
754 // Adjust the type back to match the Inst. Note that we can't use InsertPt
755 // here because the SCEVExpander may have inserted the instructions after
756 // that point, in its efforts to avoid inserting redundant expressions.
757 if (isa<PointerType>(OperandValToReplace->getType())) {
758 NewVal = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
760 OperandValToReplace->getType());
762 // Replace the use of the operand Value with the new Phi we just created.
763 Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
766 DOUT << " Replacing with ";
767 WriteAsOperand(*DOUT, NewVal, /*PrintType=*/false);
768 DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
773 // PHI nodes are more complex. We have to insert one copy of the NewBase+Imm
774 // expression into each operand block that uses it. Note that PHI nodes can
775 // have multiple entries for the same predecessor. We use a map to make sure
776 // that a PHI node only has a single Value* for each predecessor (which also
777 // prevents us from inserting duplicate code in some blocks).
778 DenseMap<BasicBlock*, Value*> InsertedCode;
779 PHINode *PN = cast<PHINode>(Inst);
780 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
781 if (PN->getIncomingValue(i) == OperandValToReplace) {
782 // If the original expression is outside the loop, put the replacement
783 // code in the same place as the original expression,
784 // which need not be an immediate predecessor of this PHI. This way we
785 // need only one copy of it even if it is referenced multiple times in
786 // the PHI. We don't do this when the original expression is inside the
787 // loop because multiple copies sometimes do useful sinking of code in
789 Instruction *OldLoc = dyn_cast<Instruction>(OperandValToReplace);
790 if (L->contains(OldLoc->getParent())) {
791 // If this is a critical edge, split the edge so that we do not insert
792 // the code on all predecessor/successor paths. We do this unless this
793 // is the canonical backedge for this loop, as this can make some
794 // inserted code be in an illegal position.
795 BasicBlock *PHIPred = PN->getIncomingBlock(i);
796 if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
797 (PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
799 // First step, split the critical edge.
800 SplitCriticalEdge(PHIPred, PN->getParent(), P, false);
802 // Next step: move the basic block. In particular, if the PHI node
803 // is outside of the loop, and PredTI is in the loop, we want to
804 // move the block to be immediately before the PHI block, not
805 // immediately after PredTI.
806 if (L->contains(PHIPred) && !L->contains(PN->getParent())) {
807 BasicBlock *NewBB = PN->getIncomingBlock(i);
808 NewBB->moveBefore(PN->getParent());
811 // Splitting the edge can reduce the number of PHI entries we have.
812 e = PN->getNumIncomingValues();
815 Value *&Code = InsertedCode[PN->getIncomingBlock(i)];
817 // Insert the code into the end of the predecessor block.
818 Instruction *InsertPt = (L->contains(OldLoc->getParent())) ?
819 PN->getIncomingBlock(i)->getTerminator() :
820 OldLoc->getParent()->getTerminator();
821 Code = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
823 // Adjust the type back to match the PHI. Note that we can't use
824 // InsertPt here because the SCEVExpander may have inserted its
825 // instructions after that point, in its efforts to avoid inserting
826 // redundant expressions.
827 if (isa<PointerType>(PN->getType())) {
828 Code = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
834 DOUT << " Changing PHI use to ";
835 WriteAsOperand(*DOUT, Code, /*PrintType=*/false);
836 DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
840 // Replace the use of the operand Value with the new Phi we just created.
841 PN->setIncomingValue(i, Code);
846 // PHI node might have become a constant value after SplitCriticalEdge.
847 DeadInsts.push_back(Inst);
851 /// fitsInAddressMode - Return true if V can be subsumed within an addressing
852 /// mode, and does not need to be put in a register first.
853 static bool fitsInAddressMode(const SCEVHandle &V, const Type *UseTy,
854 const TargetLowering *TLI, bool HasBaseReg) {
855 if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
856 int64_t VC = SC->getValue()->getSExtValue();
858 TargetLowering::AddrMode AM;
860 AM.HasBaseReg = HasBaseReg;
861 return TLI->isLegalAddressingMode(AM, UseTy);
863 // Defaults to PPC. PPC allows a sign-extended 16-bit immediate field.
864 return (VC > -(1 << 16) && VC < (1 << 16)-1);
868 if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
869 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(SU->getValue()))
870 if (TLI && CE->getOpcode() == Instruction::PtrToInt) {
871 Constant *Op0 = CE->getOperand(0);
872 if (GlobalValue *GV = dyn_cast<GlobalValue>(Op0)) {
873 TargetLowering::AddrMode AM;
875 AM.HasBaseReg = HasBaseReg;
876 return TLI->isLegalAddressingMode(AM, UseTy);
882 /// MoveLoopVariantsToImmediateField - Move any subexpressions from Val that are
883 /// loop varying to the Imm operand.
884 static void MoveLoopVariantsToImmediateField(SCEVHandle &Val, SCEVHandle &Imm,
885 Loop *L, ScalarEvolution *SE) {
886 if (Val->isLoopInvariant(L)) return; // Nothing to do.
888 if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
889 std::vector<SCEVHandle> NewOps;
890 NewOps.reserve(SAE->getNumOperands());
892 for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
893 if (!SAE->getOperand(i)->isLoopInvariant(L)) {
894 // If this is a loop-variant expression, it must stay in the immediate
895 // field of the expression.
896 Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
898 NewOps.push_back(SAE->getOperand(i));
902 Val = SE->getIntegerSCEV(0, Val->getType());
904 Val = SE->getAddExpr(NewOps);
905 } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
906 // Try to pull immediates out of the start value of nested addrec's.
907 SCEVHandle Start = SARE->getStart();
908 MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
910 std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
912 Val = SE->getAddRecExpr(Ops, SARE->getLoop());
914 // Otherwise, all of Val is variant, move the whole thing over.
915 Imm = SE->getAddExpr(Imm, Val);
916 Val = SE->getIntegerSCEV(0, Val->getType());
921 /// MoveImmediateValues - Look at Val, and pull out any additions of constants
922 /// that can fit into the immediate field of instructions in the target.
923 /// Accumulate these immediate values into the Imm value.
924 static void MoveImmediateValues(const TargetLowering *TLI,
926 SCEVHandle &Val, SCEVHandle &Imm,
927 bool isAddress, Loop *L,
928 ScalarEvolution *SE) {
929 const Type *UseTy = User->getType();
930 if (StoreInst *SI = dyn_cast<StoreInst>(User))
931 UseTy = SI->getOperand(0)->getType();
933 if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
934 std::vector<SCEVHandle> NewOps;
935 NewOps.reserve(SAE->getNumOperands());
937 for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
938 SCEVHandle NewOp = SAE->getOperand(i);
939 MoveImmediateValues(TLI, User, NewOp, Imm, isAddress, L, SE);
941 if (!NewOp->isLoopInvariant(L)) {
942 // If this is a loop-variant expression, it must stay in the immediate
943 // field of the expression.
944 Imm = SE->getAddExpr(Imm, NewOp);
946 NewOps.push_back(NewOp);
951 Val = SE->getIntegerSCEV(0, Val->getType());
953 Val = SE->getAddExpr(NewOps);
955 } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
956 // Try to pull immediates out of the start value of nested addrec's.
957 SCEVHandle Start = SARE->getStart();
958 MoveImmediateValues(TLI, User, Start, Imm, isAddress, L, SE);
960 if (Start != SARE->getStart()) {
961 std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
963 Val = SE->getAddRecExpr(Ops, SARE->getLoop());
966 } else if (SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
967 // Transform "8 * (4 + v)" -> "32 + 8*V" if "32" fits in the immed field.
968 if (isAddress && fitsInAddressMode(SME->getOperand(0), UseTy, TLI, false) &&
969 SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
971 SCEVHandle SubImm = SE->getIntegerSCEV(0, Val->getType());
972 SCEVHandle NewOp = SME->getOperand(1);
973 MoveImmediateValues(TLI, User, NewOp, SubImm, isAddress, L, SE);
975 // If we extracted something out of the subexpressions, see if we can
977 if (NewOp != SME->getOperand(1)) {
978 // Scale SubImm up by "8". If the result is a target constant, we are
980 SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
981 if (fitsInAddressMode(SubImm, UseTy, TLI, false)) {
982 // Accumulate the immediate.
983 Imm = SE->getAddExpr(Imm, SubImm);
985 // Update what is left of 'Val'.
986 Val = SE->getMulExpr(SME->getOperand(0), NewOp);
993 // Loop-variant expressions must stay in the immediate field of the
995 if ((isAddress && fitsInAddressMode(Val, UseTy, TLI, false)) ||
996 !Val->isLoopInvariant(L)) {
997 Imm = SE->getAddExpr(Imm, Val);
998 Val = SE->getIntegerSCEV(0, Val->getType());
1002 // Otherwise, no immediates to move.
1006 /// SeparateSubExprs - Decompose Expr into all of the subexpressions that are
1007 /// added together. This is used to reassociate common addition subexprs
1008 /// together for maximal sharing when rewriting bases.
1009 static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
1011 ScalarEvolution *SE) {
1012 if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
1013 for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
1014 SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
1015 } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
1016 SCEVHandle Zero = SE->getIntegerSCEV(0, Expr->getType());
1017 if (SARE->getOperand(0) == Zero) {
1018 SubExprs.push_back(Expr);
1020 // Compute the addrec with zero as its base.
1021 std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
1022 Ops[0] = Zero; // Start with zero base.
1023 SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
1026 SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
1028 } else if (!Expr->isZero()) {
1030 SubExprs.push_back(Expr);
1034 // This is logically local to the following function, but C++ says we have
1035 // to make it file scope.
1036 struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
1038 /// RemoveCommonExpressionsFromUseBases - Look through all of the Bases of all
1039 /// the Uses, removing any common subexpressions, except that if all such
1040 /// subexpressions can be folded into an addressing mode for all uses inside
1041 /// the loop (this case is referred to as "free" in comments herein) we do
1042 /// not remove anything. This looks for things like (a+b+c) and
1043 /// (a+c+d) and computes the common (a+c) subexpression. The common expression
1044 /// is *removed* from the Bases and returned.
1046 RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
1047 ScalarEvolution *SE, Loop *L,
1048 const TargetLowering *TLI) {
1049 unsigned NumUses = Uses.size();
1051 // Only one use? This is a very common case, so we handle it specially and
1053 SCEVHandle Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
1054 SCEVHandle Result = Zero;
1055 SCEVHandle FreeResult = Zero;
1057 // If the use is inside the loop, use its base, regardless of what it is:
1058 // it is clearly shared across all the IV's. If the use is outside the loop
1059 // (which means after it) we don't want to factor anything *into* the loop,
1060 // so just use 0 as the base.
1061 if (L->contains(Uses[0].Inst->getParent()))
1062 std::swap(Result, Uses[0].Base);
1066 // To find common subexpressions, count how many of Uses use each expression.
1067 // If any subexpressions are used Uses.size() times, they are common.
1068 // Also track whether all uses of each expression can be moved into an
1069 // an addressing mode "for free"; such expressions are left within the loop.
1070 // struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
1071 std::map<SCEVHandle, SubExprUseData> SubExpressionUseData;
1073 // UniqueSubExprs - Keep track of all of the subexpressions we see in the
1074 // order we see them.
1075 std::vector<SCEVHandle> UniqueSubExprs;
1077 std::vector<SCEVHandle> SubExprs;
1078 unsigned NumUsesInsideLoop = 0;
1079 for (unsigned i = 0; i != NumUses; ++i) {
1080 // If the user is outside the loop, just ignore it for base computation.
1081 // Since the user is outside the loop, it must be *after* the loop (if it
1082 // were before, it could not be based on the loop IV). We don't want users
1083 // after the loop to affect base computation of values *inside* the loop,
1084 // because we can always add their offsets to the result IV after the loop
1085 // is done, ensuring we get good code inside the loop.
1086 if (!L->contains(Uses[i].Inst->getParent()))
1088 NumUsesInsideLoop++;
1090 // If the base is zero (which is common), return zero now, there are no
1091 // CSEs we can find.
1092 if (Uses[i].Base == Zero) return Zero;
1094 // If this use is as an address we may be able to put CSEs in the addressing
1095 // mode rather than hoisting them.
1096 bool isAddrUse = isAddressUse(Uses[i].Inst, Uses[i].OperandValToReplace);
1097 // We may need the UseTy below, but only when isAddrUse, so compute it
1098 // only in that case.
1099 const Type *UseTy = 0;
1101 UseTy = Uses[i].Inst->getType();
1102 if (StoreInst *SI = dyn_cast<StoreInst>(Uses[i].Inst))
1103 UseTy = SI->getOperand(0)->getType();
1106 // Split the expression into subexprs.
1107 SeparateSubExprs(SubExprs, Uses[i].Base, SE);
1108 // Add one to SubExpressionUseData.Count for each subexpr present, and
1109 // if the subexpr is not a valid immediate within an addressing mode use,
1110 // set SubExpressionUseData.notAllUsesAreFree. We definitely want to
1111 // hoist these out of the loop (if they are common to all uses).
1112 for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
1113 if (++SubExpressionUseData[SubExprs[j]].Count == 1)
1114 UniqueSubExprs.push_back(SubExprs[j]);
1115 if (!isAddrUse || !fitsInAddressMode(SubExprs[j], UseTy, TLI, false))
1116 SubExpressionUseData[SubExprs[j]].notAllUsesAreFree = true;
1121 // Now that we know how many times each is used, build Result. Iterate over
1122 // UniqueSubexprs so that we have a stable ordering.
1123 for (unsigned i = 0, e = UniqueSubExprs.size(); i != e; ++i) {
1124 std::map<SCEVHandle, SubExprUseData>::iterator I =
1125 SubExpressionUseData.find(UniqueSubExprs[i]);
1126 assert(I != SubExpressionUseData.end() && "Entry not found?");
1127 if (I->second.Count == NumUsesInsideLoop) { // Found CSE!
1128 if (I->second.notAllUsesAreFree)
1129 Result = SE->getAddExpr(Result, I->first);
1131 FreeResult = SE->getAddExpr(FreeResult, I->first);
1133 // Remove non-cse's from SubExpressionUseData.
1134 SubExpressionUseData.erase(I);
1137 if (FreeResult != Zero) {
1138 // We have some subexpressions that can be subsumed into addressing
1139 // modes in every use inside the loop. However, it's possible that
1140 // there are so many of them that the combined FreeResult cannot
1141 // be subsumed, or that the target cannot handle both a FreeResult
1142 // and a Result in the same instruction (for example because it would
1143 // require too many registers). Check this.
1144 for (unsigned i=0; i<NumUses; ++i) {
1145 if (!L->contains(Uses[i].Inst->getParent()))
1147 // We know this is an addressing mode use; if there are any uses that
1148 // are not, FreeResult would be Zero.
1149 const Type *UseTy = Uses[i].Inst->getType();
1150 if (StoreInst *SI = dyn_cast<StoreInst>(Uses[i].Inst))
1151 UseTy = SI->getOperand(0)->getType();
1152 if (!fitsInAddressMode(FreeResult, UseTy, TLI, Result!=Zero)) {
1153 // FIXME: could split up FreeResult into pieces here, some hoisted
1154 // and some not. There is no obvious advantage to this.
1155 Result = SE->getAddExpr(Result, FreeResult);
1162 // If we found no CSE's, return now.
1163 if (Result == Zero) return Result;
1165 // If we still have a FreeResult, remove its subexpressions from
1166 // SubExpressionUseData. This means they will remain in the use Bases.
1167 if (FreeResult != Zero) {
1168 SeparateSubExprs(SubExprs, FreeResult, SE);
1169 for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
1170 std::map<SCEVHandle, SubExprUseData>::iterator I =
1171 SubExpressionUseData.find(SubExprs[j]);
1172 SubExpressionUseData.erase(I);
1177 // Otherwise, remove all of the CSE's we found from each of the base values.
1178 for (unsigned i = 0; i != NumUses; ++i) {
1179 // Uses outside the loop don't necessarily include the common base, but
1180 // the final IV value coming into those uses does. Instead of trying to
1181 // remove the pieces of the common base, which might not be there,
1182 // subtract off the base to compensate for this.
1183 if (!L->contains(Uses[i].Inst->getParent())) {
1184 Uses[i].Base = SE->getMinusSCEV(Uses[i].Base, Result);
1188 // Split the expression into subexprs.
1189 SeparateSubExprs(SubExprs, Uses[i].Base, SE);
1191 // Remove any common subexpressions.
1192 for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
1193 if (SubExpressionUseData.count(SubExprs[j])) {
1194 SubExprs.erase(SubExprs.begin()+j);
1198 // Finally, add the non-shared expressions together.
1199 if (SubExprs.empty())
1200 Uses[i].Base = Zero;
1202 Uses[i].Base = SE->getAddExpr(SubExprs);
1209 /// ValidStride - Check whether the given Scale is valid for all loads and
1210 /// stores in UsersToProcess.
1212 bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
1214 const std::vector<BasedUser>& UsersToProcess) {
1218 for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
1219 // If this is a load or other access, pass the type of the access in.
1220 const Type *AccessTy = Type::VoidTy;
1221 if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst))
1222 AccessTy = SI->getOperand(0)->getType();
1223 else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
1224 AccessTy = LI->getType();
1225 else if (isa<PHINode>(UsersToProcess[i].Inst))
1228 TargetLowering::AddrMode AM;
1229 if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
1230 AM.BaseOffs = SC->getValue()->getSExtValue();
1231 AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
1234 // If load[imm+r*scale] is illegal, bail out.
1235 if (!TLI->isLegalAddressingMode(AM, AccessTy))
1241 /// RequiresTypeConversion - Returns true if converting Ty1 to Ty2 is not
1243 bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
1247 if (Ty1->canLosslesslyBitCastTo(Ty2))
1249 if (TLI && TLI->isTruncateFree(Ty1, Ty2))
1251 if (isa<PointerType>(Ty2) && Ty1->canLosslesslyBitCastTo(UIntPtrTy))
1253 if (isa<PointerType>(Ty1) && Ty2->canLosslesslyBitCastTo(UIntPtrTy))
1258 /// CheckForIVReuse - Returns the multiple if the stride is the multiple
1259 /// of a previous stride and it is a legal value for the target addressing
1260 /// mode scale component and optional base reg. This allows the users of
1261 /// this stride to be rewritten as prev iv * factor. It returns 0 if no
1262 /// reuse is possible. Factors can be negative on same targets, e.g. ARM.
1264 /// If all uses are outside the loop, we don't require that all multiplies
1265 /// be folded into the addressing mode, nor even that the factor be constant;
1266 /// a multiply (executed once) outside the loop is better than another IV
1267 /// within. Well, usually.
1268 SCEVHandle LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
1269 bool AllUsesAreAddresses,
1270 bool AllUsesAreOutsideLoop,
1271 const SCEVHandle &Stride,
1272 IVExpr &IV, const Type *Ty,
1273 const std::vector<BasedUser>& UsersToProcess) {
1274 if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
1275 int64_t SInt = SC->getValue()->getSExtValue();
1276 for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
1278 std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
1279 IVsByStride.find(StrideOrder[NewStride]);
1280 if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
1282 int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
1283 if (SI->first != Stride &&
1284 (unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0))
1286 int64_t Scale = SInt / SSInt;
1287 // Check that this stride is valid for all the types used for loads and
1288 // stores; if it can be used for some and not others, we might as well use
1289 // the original stride everywhere, since we have to create the IV for it
1290 // anyway. If the scale is 1, then we don't need to worry about folding
1293 (AllUsesAreAddresses &&
1294 ValidStride(HasBaseReg, Scale, UsersToProcess)))
1295 for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
1296 IE = SI->second.IVs.end(); II != IE; ++II)
1297 // FIXME: Only handle base == 0 for now.
1298 // Only reuse previous IV if it would not require a type conversion.
1299 if (II->Base->isZero() &&
1300 !RequiresTypeConversion(II->Base->getType(), Ty)) {
1302 return SE->getIntegerSCEV(Scale, Stride->getType());
1305 } else if (AllUsesAreOutsideLoop) {
1306 // Accept nonconstant strides here; it is really really right to substitute
1307 // an existing IV if we can.
1308 for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
1310 std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
1311 IVsByStride.find(StrideOrder[NewStride]);
1312 if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
1314 int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
1315 if (SI->first != Stride && SSInt != 1)
1317 for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
1318 IE = SI->second.IVs.end(); II != IE; ++II)
1319 // Accept nonzero base here.
1320 // Only reuse previous IV if it would not require a type conversion.
1321 if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
1326 // Special case, old IV is -1*x and this one is x. Can treat this one as
1328 for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
1330 std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
1331 IVsByStride.find(StrideOrder[NewStride]);
1332 if (SI == IVsByStride.end())
1334 if (SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(SI->first))
1335 if (SCEVConstant *SC = dyn_cast<SCEVConstant>(ME->getOperand(0)))
1336 if (Stride == ME->getOperand(1) &&
1337 SC->getValue()->getSExtValue() == -1LL)
1338 for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
1339 IE = SI->second.IVs.end(); II != IE; ++II)
1340 // Accept nonzero base here.
1341 // Only reuse previous IV if it would not require type conversion.
1342 if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
1344 return SE->getIntegerSCEV(-1LL, Stride->getType());
1348 return SE->getIntegerSCEV(0, Stride->getType());
1351 /// PartitionByIsUseOfPostIncrementedValue - Simple boolean predicate that
1352 /// returns true if Val's isUseOfPostIncrementedValue is true.
1353 static bool PartitionByIsUseOfPostIncrementedValue(const BasedUser &Val) {
1354 return Val.isUseOfPostIncrementedValue;
1357 /// isNonConstantNegative - Return true if the specified scev is negated, but
1359 static bool isNonConstantNegative(const SCEVHandle &Expr) {
1360 SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
1361 if (!Mul) return false;
1363 // If there is a constant factor, it will be first.
1364 SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
1365 if (!SC) return false;
1367 // Return true if the value is negative, this matches things like (-42 * V).
1368 return SC->getValue()->getValue().isNegative();
1371 // CollectIVUsers - Transform our list of users and offsets to a bit more
1372 // complex table. In this new vector, each 'BasedUser' contains 'Base', the base
1373 // of the strided accesses, as well as the old information from Uses. We
1374 // progressively move information from the Base field to the Imm field, until
1375 // we eventually have the full access expression to rewrite the use.
1376 SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
1377 IVUsersOfOneStride &Uses,
1379 bool &AllUsesAreAddresses,
1380 bool &AllUsesAreOutsideLoop,
1381 std::vector<BasedUser> &UsersToProcess) {
1382 UsersToProcess.reserve(Uses.Users.size());
1383 for (unsigned i = 0, e = Uses.Users.size(); i != e; ++i) {
1384 UsersToProcess.push_back(BasedUser(Uses.Users[i], SE));
1386 // Move any loop variant operands from the offset field to the immediate
1387 // field of the use, so that we don't try to use something before it is
1389 MoveLoopVariantsToImmediateField(UsersToProcess.back().Base,
1390 UsersToProcess.back().Imm, L, SE);
1391 assert(UsersToProcess.back().Base->isLoopInvariant(L) &&
1392 "Base value is not loop invariant!");
1395 // We now have a whole bunch of uses of like-strided induction variables, but
1396 // they might all have different bases. We want to emit one PHI node for this
1397 // stride which we fold as many common expressions (between the IVs) into as
1398 // possible. Start by identifying the common expressions in the base values
1399 // for the strides (e.g. if we have "A+C+B" and "A+B+D" as our bases, find
1400 // "A+B"), emit it to the preheader, then remove the expression from the
1401 // UsersToProcess base values.
1402 SCEVHandle CommonExprs =
1403 RemoveCommonExpressionsFromUseBases(UsersToProcess, SE, L, TLI);
1405 // Next, figure out what we can represent in the immediate fields of
1406 // instructions. If we can represent anything there, move it to the imm
1407 // fields of the BasedUsers. We do this so that it increases the commonality
1408 // of the remaining uses.
1409 unsigned NumPHI = 0;
1410 for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
1411 // If the user is not in the current loop, this means it is using the exit
1412 // value of the IV. Do not put anything in the base, make sure it's all in
1413 // the immediate field to allow as much factoring as possible.
1414 if (!L->contains(UsersToProcess[i].Inst->getParent())) {
1415 UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
1416 UsersToProcess[i].Base);
1417 UsersToProcess[i].Base =
1418 SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
1421 // Addressing modes can be folded into loads and stores. Be careful that
1422 // the store is through the expression, not of the expression though.
1424 bool isAddress = isAddressUse(UsersToProcess[i].Inst,
1425 UsersToProcess[i].OperandValToReplace);
1426 if (isa<PHINode>(UsersToProcess[i].Inst)) {
1431 // Not all uses are outside the loop.
1432 AllUsesAreOutsideLoop = false;
1434 // If this use isn't an address, then not all uses are addresses.
1435 if (!isAddress && !isPHI)
1436 AllUsesAreAddresses = false;
1438 MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
1439 UsersToProcess[i].Imm, isAddress, L, SE);
1443 // If one of the use if a PHI node and all other uses are addresses, still
1444 // allow iv reuse. Essentially we are trading one constant multiplication
1445 // for one fewer iv.
1447 AllUsesAreAddresses = false;
1452 /// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
1453 /// stride of IV. All of the users may have different starting values, and this
1454 /// may not be the only stride (we know it is if isOnlyStride is true).
1455 void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
1456 IVUsersOfOneStride &Uses,
1458 bool isOnlyStride) {
1459 // If all the users are moved to another stride, then there is nothing to do.
1460 if (Uses.Users.empty())
1463 // Keep track if every use in UsersToProcess is an address. If they all are,
1464 // we may be able to rewrite the entire collection of them in terms of a
1465 // smaller-stride IV.
1466 bool AllUsesAreAddresses = true;
1468 // Keep track if every use of a single stride is outside the loop. If so,
1469 // we want to be more aggressive about reusing a smaller-stride IV; a
1470 // multiply outside the loop is better than another IV inside. Well, usually.
1471 bool AllUsesAreOutsideLoop = true;
1473 // Transform our list of users and offsets to a bit more complex table. In
1474 // this new vector, each 'BasedUser' contains 'Base' the base of the
1475 // strided accessas well as the old information from Uses. We progressively
1476 // move information from the Base field to the Imm field, until we eventually
1477 // have the full access expression to rewrite the use.
1478 std::vector<BasedUser> UsersToProcess;
1479 SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
1480 AllUsesAreOutsideLoop,
1483 // If we managed to find some expressions in common, we'll need to carry
1484 // their value in a register and add it in for each use. This will take up
1485 // a register operand, which potentially restricts what stride values are
1487 bool HaveCommonExprs = !CommonExprs->isZero();
1489 // If all uses are addresses, check if it is possible to reuse an IV with a
1490 // stride that is a factor of this stride. And that the multiple is a number
1491 // that can be encoded in the scale field of the target addressing mode. And
1492 // that we will have a valid instruction after this substition, including the
1493 // immediate field, if any.
1494 PHINode *NewPHI = NULL;
1496 IVExpr ReuseIV(SE->getIntegerSCEV(0, Type::Int32Ty),
1497 SE->getIntegerSCEV(0, Type::Int32Ty),
1499 SCEVHandle RewriteFactor =
1500 CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
1501 AllUsesAreOutsideLoop,
1502 Stride, ReuseIV, CommonExprs->getType(),
1504 const Type *ReplacedTy = CommonExprs->getType();
1506 // Now that we know what we need to do, insert the PHI node itself.
1508 DOUT << "LSR: Examining IVs of TYPE " << *ReplacedTy << " of STRIDE "
1510 << " Common base: " << *CommonExprs << "\n";
1512 SCEVExpander Rewriter(*SE, *LI);
1513 SCEVExpander PreheaderRewriter(*SE, *LI);
1515 BasicBlock *Preheader = L->getLoopPreheader();
1516 Instruction *PreInsertPt = Preheader->getTerminator();
1517 Instruction *PhiInsertBefore = L->getHeader()->begin();
1518 BasicBlock *LatchBlock = L->getLoopLatch();
1520 // Emit the initial base value into the loop preheader.
1522 = PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt);
1524 if (isa<SCEVConstant>(RewriteFactor) &&
1525 cast<SCEVConstant>(RewriteFactor)->isZero()) {
1526 // Create a new Phi for this base, and stick it in the loop header.
1527 NewPHI = PHINode::Create(ReplacedTy, "iv.", PhiInsertBefore);
1530 // Add common base to the new Phi node.
1531 NewPHI->addIncoming(CommonBaseV, Preheader);
1533 // If the stride is negative, insert a sub instead of an add for the
1535 bool isNegative = isNonConstantNegative(Stride);
1536 SCEVHandle IncAmount = Stride;
1538 IncAmount = SE->getNegativeSCEV(Stride);
1540 // Insert the stride into the preheader.
1541 Value *StrideV = PreheaderRewriter.expandCodeFor(IncAmount, PreInsertPt);
1542 if (!isa<ConstantInt>(StrideV)) ++NumVariable;
1544 // Emit the increment of the base value before the terminator of the loop
1545 // latch block, and add it to the Phi node.
1546 SCEVHandle IncExp = SE->getUnknown(StrideV);
1548 IncExp = SE->getNegativeSCEV(IncExp);
1549 IncExp = SE->getAddExpr(SE->getUnknown(NewPHI), IncExp);
1551 IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator());
1552 IncV->setName(NewPHI->getName()+".inc");
1553 NewPHI->addIncoming(IncV, LatchBlock);
1555 // Remember this in case a later stride is multiple of this.
1556 IVsByStride[Stride].addIV(Stride, CommonExprs, NewPHI, IncV);
1559 DOUT << " Inserted new PHI: IV=";
1560 WriteAsOperand(*DOUT, NewPHI, /*PrintType=*/false);
1562 WriteAsOperand(*DOUT, IncV, /*PrintType=*/false);
1566 DOUT << " Rewriting in terms of existing IV of STRIDE " << *ReuseIV.Stride
1567 << " and BASE " << *ReuseIV.Base << "\n";
1568 NewPHI = ReuseIV.PHI;
1569 IncV = ReuseIV.IncV;
1571 Constant *C = dyn_cast<Constant>(CommonBaseV);
1573 (!C->isNullValue() &&
1574 !fitsInAddressMode(SE->getUnknown(CommonBaseV), ReplacedTy,
1576 // We want the common base emitted into the preheader! This is just
1577 // using cast as a copy so BitCast (no-op cast) is appropriate
1578 CommonBaseV = new BitCastInst(CommonBaseV, CommonBaseV->getType(),
1579 "commonbase", PreInsertPt);
1582 // We want to emit code for users inside the loop first. To do this, we
1583 // rearrange BasedUser so that the entries at the end have
1584 // isUseOfPostIncrementedValue = false, because we pop off the end of the
1585 // vector (so we handle them first).
1586 std::partition(UsersToProcess.begin(), UsersToProcess.end(),
1587 PartitionByIsUseOfPostIncrementedValue);
1589 // Sort this by base, so that things with the same base are handled
1590 // together. By partitioning first and stable-sorting later, we are
1591 // guaranteed that within each base we will pop off users from within the
1592 // loop before users outside of the loop with a particular base.
1594 // We would like to use stable_sort here, but we can't. The problem is that
1595 // SCEVHandle's don't have a deterministic ordering w.r.t to each other, so
1596 // we don't have anything to do a '<' comparison on. Because we think the
1597 // number of uses is small, do a horrible bubble sort which just relies on
1599 for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
1600 // Get a base value.
1601 SCEVHandle Base = UsersToProcess[i].Base;
1603 // Compact everything with this base to be consecutive with this one.
1604 for (unsigned j = i+1; j != e; ++j) {
1605 if (UsersToProcess[j].Base == Base) {
1606 std::swap(UsersToProcess[i+1], UsersToProcess[j]);
1612 // Process all the users now. This outer loop handles all bases, the inner
1613 // loop handles all users of a particular base.
1614 while (!UsersToProcess.empty()) {
1615 SCEVHandle Base = UsersToProcess.back().Base;
1616 Instruction *Inst = UsersToProcess.back().Inst;
1618 // Emit the code for Base into the preheader.
1619 Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt);
1622 DOUT << " Examining uses with BASE ";
1623 WriteAsOperand(*DOUT, BaseV, /*PrintType=*/false);
1627 // If BaseV is a constant other than 0, make sure that it gets inserted into
1628 // the preheader, instead of being forward substituted into the uses. We do
1629 // this by forcing a BitCast (noop cast) to be inserted into the preheader
1631 if (Constant *C = dyn_cast<Constant>(BaseV)) {
1632 if (!C->isNullValue() && !fitsInAddressMode(Base, ReplacedTy,
1634 // We want this constant emitted into the preheader! This is just
1635 // using cast as a copy so BitCast (no-op cast) is appropriate
1636 BaseV = new BitCastInst(BaseV, BaseV->getType(), "preheaderinsert",
1641 // Emit the code to add the immediate offset to the Phi value, just before
1642 // the instructions that we identified as using this stride and base.
1644 // FIXME: Use emitted users to emit other users.
1645 BasedUser &User = UsersToProcess.back();
1648 DOUT << " Examining use ";
1649 WriteAsOperand(*DOUT, UsersToProcess.back().OperandValToReplace,
1650 /*PrintType=*/false);
1651 DOUT << " in Inst: " << *Inst;
1654 // If this instruction wants to use the post-incremented value, move it
1655 // after the post-inc and use its value instead of the PHI.
1656 Value *RewriteOp = NewPHI;
1657 if (User.isUseOfPostIncrementedValue) {
1660 // If this user is in the loop, make sure it is the last thing in the
1661 // loop to ensure it is dominated by the increment.
1662 if (L->contains(User.Inst->getParent()))
1663 User.Inst->moveBefore(LatchBlock->getTerminator());
1665 if (RewriteOp->getType() != ReplacedTy) {
1666 Instruction::CastOps opcode = Instruction::Trunc;
1667 if (ReplacedTy->getPrimitiveSizeInBits() ==
1668 RewriteOp->getType()->getPrimitiveSizeInBits())
1669 opcode = Instruction::BitCast;
1670 RewriteOp = SCEVExpander::InsertCastOfTo(opcode, RewriteOp, ReplacedTy);
1673 SCEVHandle RewriteExpr = SE->getUnknown(RewriteOp);
1675 // If we had to insert new instructions for RewriteOp, we have to
1676 // consider that they may not have been able to end up immediately
1677 // next to RewriteOp, because non-PHI instructions may never precede
1678 // PHI instructions in a block. In this case, remember where the last
1679 // instruction was inserted so that if we're replacing a different
1680 // PHI node, we can use the later point to expand the final
1682 Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
1683 if (RewriteOp == NewPHI) NewBasePt = 0;
1685 // Clear the SCEVExpander's expression map so that we are guaranteed
1686 // to have the code emitted where we expect it.
1689 // If we are reusing the iv, then it must be multiplied by a constant
1690 // factor to take advantage of the addressing mode scale component.
1691 if (!isa<SCEVConstant>(RewriteFactor) ||
1692 !cast<SCEVConstant>(RewriteFactor)->isZero()) {
1693 // If we're reusing an IV with a nonzero base (currently this happens
1694 // only when all reuses are outside the loop) subtract that base here.
1695 // The base has been used to initialize the PHI node but we don't want
1697 if (!ReuseIV.Base->isZero()) {
1698 SCEVHandle typedBase = ReuseIV.Base;
1699 if (RewriteExpr->getType()->getPrimitiveSizeInBits() !=
1700 ReuseIV.Base->getType()->getPrimitiveSizeInBits()) {
1701 // It's possible the original IV is a larger type than the new IV,
1702 // in which case we have to truncate the Base. We checked in
1703 // RequiresTypeConversion that this is valid.
1704 assert (RewriteExpr->getType()->getPrimitiveSizeInBits() <
1705 ReuseIV.Base->getType()->getPrimitiveSizeInBits() &&
1706 "Unexpected lengthening conversion!");
1707 typedBase = SE->getTruncateExpr(ReuseIV.Base,
1708 RewriteExpr->getType());
1710 RewriteExpr = SE->getMinusSCEV(RewriteExpr, typedBase);
1713 // Multiply old variable, with base removed, by new scale factor.
1714 RewriteExpr = SE->getMulExpr(RewriteFactor,
1717 // The common base is emitted in the loop preheader. But since we
1718 // are reusing an IV, it has not been used to initialize the PHI node.
1719 // Add it to the expression used to rewrite the uses.
1720 // When this use is outside the loop, we earlier subtracted the
1721 // common base, and are adding it back here. Use the same expression
1722 // as before, rather than CommonBaseV, so DAGCombiner will zap it.
1723 if (!isa<ConstantInt>(CommonBaseV) ||
1724 !cast<ConstantInt>(CommonBaseV)->isZero()) {
1725 if (L->contains(User.Inst->getParent()))
1726 RewriteExpr = SE->getAddExpr(RewriteExpr,
1727 SE->getUnknown(CommonBaseV));
1729 RewriteExpr = SE->getAddExpr(RewriteExpr, CommonExprs);
1733 // Now that we know what we need to do, insert code before User for the
1734 // immediate and any loop-variant expressions.
1735 if (!isa<ConstantInt>(BaseV) || !cast<ConstantInt>(BaseV)->isZero())
1736 // Add BaseV to the PHI value if needed.
1737 RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
1739 User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
1743 // Mark old value we replaced as possibly dead, so that it is eliminated
1744 // if we just replaced the last use of that value.
1745 DeadInsts.push_back(cast<Instruction>(User.OperandValToReplace));
1747 UsersToProcess.pop_back();
1750 // If there are any more users to process with the same base, process them
1751 // now. We sorted by base above, so we just have to check the last elt.
1752 } while (!UsersToProcess.empty() && UsersToProcess.back().Base == Base);
1753 // TODO: Next, find out which base index is the most common, pull it out.
1756 // IMPORTANT TODO: Figure out how to partition the IV's with this stride, but
1757 // different starting values, into different PHIs.
1760 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1761 /// set the IV user and stride information and return true, otherwise return
1763 bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
1764 const SCEVHandle *&CondStride) {
1765 for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e && !CondUse;
1767 std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
1768 IVUsesByStride.find(StrideOrder[Stride]);
1769 assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
1771 for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
1772 E = SI->second.Users.end(); UI != E; ++UI)
1773 if (UI->User == Cond) {
1774 // NOTE: we could handle setcc instructions with multiple uses here, but
1775 // InstCombine does it as well for simple uses, it's not clear that it
1776 // occurs enough in real life to handle.
1778 CondStride = &SI->first;
1786 // Constant strides come first which in turns are sorted by their absolute
1787 // values. If absolute values are the same, then positive strides comes first.
1789 // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
1790 struct StrideCompare {
1791 bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
1792 SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
1793 SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
1795 int64_t LV = LHSC->getValue()->getSExtValue();
1796 int64_t RV = RHSC->getValue()->getSExtValue();
1797 uint64_t ALV = (LV < 0) ? -LV : LV;
1798 uint64_t ARV = (RV < 0) ? -RV : RV;
1806 // If it's the same value but different type, sort by bit width so
1807 // that we emit larger induction variables before smaller
1808 // ones, letting the smaller be re-written in terms of larger ones.
1809 return RHS->getBitWidth() < LHS->getBitWidth();
1811 return LHSC && !RHSC;
1816 /// ChangeCompareStride - If a loop termination compare instruction is the
1817 /// only use of its stride, and the compaison is against a constant value,
1818 /// try eliminate the stride by moving the compare instruction to another
1819 /// stride and change its constant operand accordingly. e.g.
1825 /// if (v2 < 10) goto loop
1830 /// if (v1 < 30) goto loop
1831 ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
1832 IVStrideUse* &CondUse,
1833 const SCEVHandle* &CondStride) {
1834 if (StrideOrder.size() < 2 ||
1835 IVUsesByStride[*CondStride].Users.size() != 1)
1837 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
1838 if (!SC) return Cond;
1839 ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1));
1840 if (!C) return Cond;
1842 ICmpInst::Predicate Predicate = Cond->getPredicate();
1843 int64_t CmpSSInt = SC->getValue()->getSExtValue();
1844 int64_t CmpVal = C->getValue().getSExtValue();
1845 unsigned BitWidth = C->getValue().getBitWidth();
1846 uint64_t SignBit = 1ULL << (BitWidth-1);
1847 const Type *CmpTy = C->getType();
1848 const Type *NewCmpTy = NULL;
1849 unsigned TyBits = CmpTy->getPrimitiveSizeInBits();
1850 unsigned NewTyBits = 0;
1851 int64_t NewCmpVal = CmpVal;
1852 SCEVHandle *NewStride = NULL;
1853 Value *NewIncV = NULL;
1856 // Check stride constant and the comparision constant signs to detect
1858 if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
1861 // Look for a suitable stride / iv as replacement.
1862 std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
1863 for (unsigned i = 0, e = StrideOrder.size(); i != e; ++i) {
1864 std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
1865 IVUsesByStride.find(StrideOrder[i]);
1866 if (!isa<SCEVConstant>(SI->first))
1868 int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
1869 if (abs(SSInt) <= abs(CmpSSInt) || (SSInt % CmpSSInt) != 0)
1872 Scale = SSInt / CmpSSInt;
1873 NewCmpVal = CmpVal * Scale;
1874 APInt Mul = APInt(BitWidth, NewCmpVal);
1875 // Check for overflow.
1876 if (Mul.getSExtValue() != NewCmpVal) {
1881 // Watch out for overflow.
1882 if (ICmpInst::isSignedPredicate(Predicate) &&
1883 (CmpVal & SignBit) != (NewCmpVal & SignBit))
1886 if (NewCmpVal != CmpVal) {
1887 // Pick the best iv to use trying to avoid a cast.
1889 for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
1890 E = SI->second.Users.end(); UI != E; ++UI) {
1891 NewIncV = UI->OperandValToReplace;
1892 if (NewIncV->getType() == CmpTy)
1900 NewCmpTy = NewIncV->getType();
1901 NewTyBits = isa<PointerType>(NewCmpTy)
1902 ? UIntPtrTy->getPrimitiveSizeInBits()
1903 : NewCmpTy->getPrimitiveSizeInBits();
1904 if (RequiresTypeConversion(NewCmpTy, CmpTy)) {
1905 // Check if it is possible to rewrite it using
1906 // an iv / stride of a smaller integer type.
1907 bool TruncOk = false;
1908 if (NewCmpTy->isInteger()) {
1909 unsigned Bits = NewTyBits;
1910 if (ICmpInst::isSignedPredicate(Predicate))
1912 uint64_t Mask = (1ULL << Bits) - 1;
1913 if (((uint64_t)NewCmpVal & Mask) == (uint64_t)NewCmpVal)
1922 // Don't rewrite if use offset is non-constant and the new type is
1923 // of a different type.
1924 // FIXME: too conservative?
1925 if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->Offset)) {
1930 bool AllUsesAreAddresses = true;
1931 bool AllUsesAreOutsideLoop = true;
1932 std::vector<BasedUser> UsersToProcess;
1933 SCEVHandle CommonExprs = CollectIVUsers(SI->first, SI->second, L,
1934 AllUsesAreAddresses,
1935 AllUsesAreOutsideLoop,
1937 // Avoid rewriting the compare instruction with an iv of new stride
1938 // if it's likely the new stride uses will be rewritten using the
1939 // stride of the compare instruction.
1940 if (AllUsesAreAddresses &&
1941 ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess)) {
1946 // If scale is negative, use swapped predicate unless it's testing
1948 if (Scale < 0 && !Cond->isEquality())
1949 Predicate = ICmpInst::getSwappedPredicate(Predicate);
1951 NewStride = &StrideOrder[i];
1956 // Forgo this transformation if it the increment happens to be
1957 // unfortunately positioned after the condition, and the condition
1958 // has multiple uses which prevent it from being moved immediately
1959 // before the branch. See
1960 // test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
1961 // for an example of this situation.
1962 if (!Cond->hasOneUse()) {
1963 for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
1969 if (NewCmpVal != CmpVal) {
1970 // Create a new compare instruction using new stride / iv.
1971 ICmpInst *OldCond = Cond;
1973 if (!isa<PointerType>(NewCmpTy))
1974 RHS = ConstantInt::get(NewCmpTy, NewCmpVal);
1976 RHS = ConstantInt::get(UIntPtrTy, NewCmpVal);
1977 RHS = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr, RHS, NewCmpTy);
1979 // Insert new compare instruction.
1980 Cond = new ICmpInst(Predicate, NewIncV, RHS,
1981 L->getHeader()->getName() + ".termcond",
1984 // Remove the old compare instruction. The old indvar is probably dead too.
1985 DeadInsts.push_back(cast<Instruction>(CondUse->OperandValToReplace));
1986 SE->deleteValueFromRecords(OldCond);
1987 OldCond->replaceAllUsesWith(Cond);
1988 OldCond->eraseFromParent();
1990 IVUsesByStride[*CondStride].Users.pop_back();
1991 SCEVHandle NewOffset = TyBits == NewTyBits
1992 ? SE->getMulExpr(CondUse->Offset,
1993 SE->getConstant(ConstantInt::get(CmpTy, Scale)))
1994 : SE->getConstant(ConstantInt::get(NewCmpTy,
1995 cast<SCEVConstant>(CondUse->Offset)->getValue()->getSExtValue()*Scale));
1996 IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewIncV);
1997 CondUse = &IVUsesByStride[*NewStride].Users.back();
1998 CondStride = NewStride;
2005 /// OptimizeSMax - Rewrite the loop's terminating condition if it uses
2006 /// an smax computation.
2008 /// This is a narrow solution to a specific, but acute, problem. For loops
2014 /// } while (++i < n);
2016 /// where the comparison is signed, the trip count isn't just 'n', because
2017 /// 'n' could be negative. And unfortunately this can come up even for loops
2018 /// where the user didn't use a C do-while loop. For example, seemingly
2019 /// well-behaved top-test loops will commonly be lowered like this:
2025 /// } while (++i < n);
2028 /// and then it's possible for subsequent optimization to obscure the if
2029 /// test in such a way that indvars can't find it.
2031 /// When indvars can't find the if test in loops like this, it creates a
2032 /// signed-max expression, which allows it to give the loop a canonical
2033 /// induction variable:
2036 /// smax = n < 1 ? 1 : n;
2039 /// } while (++i != smax);
2041 /// Canonical induction variables are necessary because the loop passes
2042 /// are designed around them. The most obvious example of this is the
2043 /// LoopInfo analysis, which doesn't remember trip count values. It
2044 /// expects to be able to rediscover the trip count each time it is
2045 /// needed, and it does this using a simple analyis that only succeeds if
2046 /// the loop has a canonical induction variable.
2048 /// However, when it comes time to generate code, the maximum operation
2049 /// can be quite costly, especially if it's inside of an outer loop.
2051 /// This function solves this problem by detecting this type of loop and
2052 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2053 /// the instructions for the maximum computation.
2055 ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
2056 IVStrideUse* &CondUse) {
2057 // Check that the loop matches the pattern we're looking for.
2058 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2059 Cond->getPredicate() != CmpInst::ICMP_NE)
2062 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2063 if (!Sel || !Sel->hasOneUse()) return Cond;
2065 SCEVHandle IterationCount = SE->getIterationCount(L);
2066 if (isa<SCEVCouldNotCompute>(IterationCount))
2068 SCEVHandle One = SE->getIntegerSCEV(1, IterationCount->getType());
2070 // Adjust for an annoying getIterationCount quirk.
2071 IterationCount = SE->getAddExpr(IterationCount, One);
2073 // Check for a max calculation that matches the pattern.
2074 SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(IterationCount);
2075 if (!SMax || SMax != SE->getSCEV(Sel)) return Cond;
2077 SCEVHandle SMaxLHS = SMax->getOperand(0);
2078 SCEVHandle SMaxRHS = SMax->getOperand(1);
2079 if (!SMaxLHS || SMaxLHS != One) return Cond;
2081 // Check the relevant induction variable for conformance to
2083 SCEVHandle IV = SE->getSCEV(Cond->getOperand(0));
2084 SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2085 if (!AR || !AR->isAffine() ||
2086 AR->getStart() != One ||
2087 AR->getStepRecurrence(*SE) != One)
2090 // Check the right operand of the select, and remember it, as it will
2091 // be used in the new comparison instruction.
2093 if (SE->getSCEV(Sel->getOperand(1)) == SMaxRHS)
2094 NewRHS = Sel->getOperand(1);
2095 else if (SE->getSCEV(Sel->getOperand(2)) == SMaxRHS)
2096 NewRHS = Sel->getOperand(2);
2097 if (!NewRHS) return Cond;
2099 // Ok, everything looks ok to change the condition into an SLT or SGE and
2100 // delete the max calculation.
2102 new ICmpInst(Cond->getPredicate() == CmpInst::ICMP_NE ?
2105 Cond->getOperand(0), NewRHS, "scmp", Cond);
2107 // Delete the max calculation instructions.
2108 SE->deleteValueFromRecords(Cond);
2109 Cond->replaceAllUsesWith(NewCond);
2110 Cond->eraseFromParent();
2111 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2112 SE->deleteValueFromRecords(Sel);
2113 Sel->eraseFromParent();
2114 if (Cmp->use_empty()) {
2115 SE->deleteValueFromRecords(Cmp);
2116 Cmp->eraseFromParent();
2118 CondUse->User = NewCond;
2122 /// OptimizeShadowIV - If IV is used in a int-to-float cast
2123 /// inside the loop then try to eliminate the cast opeation.
2124 void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
2126 SCEVHandle IterationCount = SE->getIterationCount(L);
2127 if (isa<SCEVCouldNotCompute>(IterationCount))
2130 for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
2132 std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
2133 IVUsesByStride.find(StrideOrder[Stride]);
2134 assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
2135 if (!isa<SCEVConstant>(SI->first))
2138 for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
2139 E = SI->second.Users.end(); UI != E; /* empty */) {
2140 std::vector<IVStrideUse>::iterator CandidateUI = UI;
2142 Instruction *ShadowUse = CandidateUI->User;
2143 const Type *DestTy = NULL;
2145 /* If shadow use is a int->float cast then insert a second IV
2146 to eliminate this cast.
2148 for (unsigned i = 0; i < n; ++i)
2154 for (unsigned i = 0; i < n; ++i, ++d)
2157 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User))
2158 DestTy = UCast->getDestTy();
2159 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User))
2160 DestTy = SCast->getDestTy();
2161 if (!DestTy) continue;
2164 /* If target does not support DestTy natively then do not apply
2165 this transformation. */
2166 MVT DVT = TLI->getValueType(DestTy);
2167 if (!TLI->isTypeLegal(DVT)) continue;
2170 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2172 if (PH->getNumIncomingValues() != 2) continue;
2174 const Type *SrcTy = PH->getType();
2175 int Mantissa = DestTy->getFPMantissaWidth();
2176 if (Mantissa == -1) continue;
2177 if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa)
2180 unsigned Entry, Latch;
2181 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2189 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2190 if (!Init) continue;
2191 ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
2193 BinaryOperator *Incr =
2194 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2195 if (!Incr) continue;
2196 if (Incr->getOpcode() != Instruction::Add
2197 && Incr->getOpcode() != Instruction::Sub)
2200 /* Initialize new IV, double d = 0.0 in above example. */
2201 ConstantInt *C = NULL;
2202 if (Incr->getOperand(0) == PH)
2203 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2204 else if (Incr->getOperand(1) == PH)
2205 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2211 /* Add new PHINode. */
2212 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
2214 /* create new increment. '++d' in above example. */
2215 ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2216 BinaryOperator *NewIncr =
2217 BinaryOperator::Create(Incr->getOpcode(),
2218 NewPH, CFP, "IV.S.next.", Incr);
2220 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2221 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2223 /* Remove cast operation */
2224 SE->deleteValueFromRecords(ShadowUse);
2225 ShadowUse->replaceAllUsesWith(NewPH);
2226 ShadowUse->eraseFromParent();
2227 SI->second.Users.erase(CandidateUI);
2234 // OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
2235 // uses in the loop, look to see if we can eliminate some, in favor of using
2236 // common indvars for the different uses.
2237 void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
2238 // TODO: implement optzns here.
2240 OptimizeShadowIV(L);
2242 // Finally, get the terminating condition for the loop if possible. If we
2243 // can, we want to change it to use a post-incremented version of its
2244 // induction variable, to allow coalescing the live ranges for the IV into
2245 // one register value.
2246 PHINode *SomePHI = cast<PHINode>(L->getHeader()->begin());
2247 BasicBlock *Preheader = L->getLoopPreheader();
2248 BasicBlock *LatchBlock =
2249 SomePHI->getIncomingBlock(SomePHI->getIncomingBlock(0) == Preheader);
2250 BranchInst *TermBr = dyn_cast<BranchInst>(LatchBlock->getTerminator());
2251 if (!TermBr || TermBr->isUnconditional() ||
2252 !isa<ICmpInst>(TermBr->getCondition()))
2254 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2256 // Search IVUsesByStride to find Cond's IVUse if there is one.
2257 IVStrideUse *CondUse = 0;
2258 const SCEVHandle *CondStride = 0;
2260 if (!FindIVUserForCond(Cond, CondUse, CondStride))
2261 return; // setcc doesn't use the IV.
2263 // If the trip count is computed in terms of an smax (due to ScalarEvolution
2264 // being unable to find a sufficient guard, for example), change the loop
2265 // comparison to use SLT instead of NE.
2266 Cond = OptimizeSMax(L, Cond, CondUse);
2268 // If possible, change stride and operands of the compare instruction to
2269 // eliminate one stride.
2270 Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
2272 // It's possible for the setcc instruction to be anywhere in the loop, and
2273 // possible for it to have multiple users. If it is not immediately before
2274 // the latch block branch, move it.
2275 if (&*++BasicBlock::iterator(Cond) != (Instruction*)TermBr) {
2276 if (Cond->hasOneUse()) { // Condition has a single use, just move it.
2277 Cond->moveBefore(TermBr);
2279 // Otherwise, clone the terminating condition and insert into the loopend.
2280 Cond = cast<ICmpInst>(Cond->clone());
2281 Cond->setName(L->getHeader()->getName() + ".termcond");
2282 LatchBlock->getInstList().insert(TermBr, Cond);
2284 // Clone the IVUse, as the old use still exists!
2285 IVUsesByStride[*CondStride].addUser(CondUse->Offset, Cond,
2286 CondUse->OperandValToReplace);
2287 CondUse = &IVUsesByStride[*CondStride].Users.back();
2291 // If we get to here, we know that we can transform the setcc instruction to
2292 // use the post-incremented version of the IV, allowing us to coalesce the
2293 // live ranges for the IV correctly.
2294 CondUse->Offset = SE->getMinusSCEV(CondUse->Offset, *CondStride);
2295 CondUse->isUseOfPostIncrementedValue = true;
2299 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
2301 LI = &getAnalysis<LoopInfo>();
2302 DT = &getAnalysis<DominatorTree>();
2303 SE = &getAnalysis<ScalarEvolution>();
2304 TD = &getAnalysis<TargetData>();
2305 UIntPtrTy = TD->getIntPtrType();
2308 // Find all uses of induction variables in this loop, and categorize
2309 // them by stride. Start by finding all of the PHI nodes in the header for
2310 // this loop. If they are induction variables, inspect their uses.
2311 SmallPtrSet<Instruction*,16> Processed; // Don't reprocess instructions.
2312 for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
2313 AddUsersIfInteresting(I, L, Processed);
2315 if (!IVUsesByStride.empty()) {
2316 // Optimize induction variables. Some indvar uses can be transformed to use
2317 // strides that will be needed for other purposes. A common example of this
2318 // is the exit test for the loop, which can often be rewritten to use the
2319 // computation of some other indvar to decide when to terminate the loop.
2322 // FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
2323 // doing computation in byte values, promote to 32-bit values if safe.
2325 // FIXME: Attempt to reuse values across multiple IV's. In particular, we
2326 // could have something like "for(i) { foo(i*8); bar(i*16) }", which should
2327 // be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
2328 // Need to be careful that IV's are all the same type. Only works for
2329 // intptr_t indvars.
2331 // If we only have one stride, we can more aggressively eliminate some
2333 bool HasOneStride = IVUsesByStride.size() == 1;
2336 DOUT << "\nLSR on ";
2340 // IVsByStride keeps IVs for one particular loop.
2341 assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
2343 // Sort the StrideOrder so we process larger strides first.
2344 std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
2346 // Note: this processes each stride/type pair individually. All users
2347 // passed into StrengthReduceStridedIVUsers have the same type AND stride.
2348 // Also, note that we iterate over IVUsesByStride indirectly by using
2349 // StrideOrder. This extra layer of indirection makes the ordering of
2350 // strides deterministic - not dependent on map order.
2351 for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
2352 std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
2353 IVUsesByStride.find(StrideOrder[Stride]);
2354 assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
2355 StrengthReduceStridedIVUsers(SI->first, SI->second, L, HasOneStride);
2359 // We're done analyzing this loop; release all the state we built up for it.
2360 CastedPointers.clear();
2361 IVUsesByStride.clear();
2362 IVsByStride.clear();
2363 StrideOrder.clear();
2364 for (unsigned i=0; i<GEPlist.size(); i++)
2365 SE->deleteValueFromRecords(GEPlist[i]);
2368 // Clean up after ourselves
2369 if (!DeadInsts.empty()) {
2370 DeleteTriviallyDeadInstructions();
2372 BasicBlock::iterator I = L->getHeader()->begin();
2373 while (PHINode *PN = dyn_cast<PHINode>(I++)) {
2374 // At this point, we know that we have killed one or more IV users.
2375 // It is worth checking to see if the cannonical indvar is also
2376 // dead, so that we can remove it as well.
2378 // We can remove a PHI if it is on a cycle in the def-use graph
2379 // where each node in the cycle has degree one, i.e. only one use,
2380 // and is an instruction with no side effects.
2382 // FIXME: this needs to eliminate an induction variable even if it's being
2383 // compared against some value to decide loop termination.
2384 if (!PN->hasOneUse())
2387 SmallPtrSet<PHINode *, 4> PHIs;
2388 for (Instruction *J = dyn_cast<Instruction>(*PN->use_begin());
2389 J && J->hasOneUse() && !J->mayWriteToMemory();
2390 J = dyn_cast<Instruction>(*J->use_begin())) {
2391 // If we find the original PHI, we've discovered a cycle.
2393 // Break the cycle and mark the PHI for deletion.
2394 SE->deleteValueFromRecords(PN);
2395 PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
2396 DeadInsts.push_back(PN);
2400 // If we find a PHI more than once, we're on a cycle that
2401 // won't prove fruitful.
2402 if (isa<PHINode>(J) && !PHIs.insert(cast<PHINode>(J)))
2406 DeleteTriviallyDeadInstructions();