1 //===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
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 munges the code in the input function to better prepare it for
11 // SelectionDAG-based code generation. This works around limitations in it's
12 // basic-block-at-a-time approach. It should eventually be removed.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "codegenprepare"
17 #include "llvm/Transforms/Scalar.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallSet.h"
20 #include "llvm/ADT/Statistic.h"
21 #include "llvm/Analysis/DominatorInternals.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/Analysis/InstructionSimplify.h"
24 #include "llvm/Analysis/ProfileInfo.h"
25 #include "llvm/Assembly/Writer.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/DataLayout.h"
28 #include "llvm/IR/DerivedTypes.h"
29 #include "llvm/IR/Function.h"
30 #include "llvm/IR/IRBuilder.h"
31 #include "llvm/IR/InlineAsm.h"
32 #include "llvm/IR/Instructions.h"
33 #include "llvm/IR/IntrinsicInst.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/CallSite.h"
36 #include "llvm/Support/CommandLine.h"
37 #include "llvm/Support/Debug.h"
38 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 #include "llvm/Support/PatternMatch.h"
40 #include "llvm/Support/ValueHandle.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/Target/TargetLibraryInfo.h"
43 #include "llvm/Target/TargetLowering.h"
44 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
45 #include "llvm/Transforms/Utils/BuildLibCalls.h"
46 #include "llvm/Transforms/Utils/BypassSlowDivision.h"
47 #include "llvm/Transforms/Utils/Local.h"
49 using namespace llvm::PatternMatch;
51 STATISTIC(NumBlocksElim, "Number of blocks eliminated");
52 STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated");
53 STATISTIC(NumGEPsElim, "Number of GEPs converted to casts");
54 STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
56 STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
58 STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
59 "computations were sunk");
60 STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
61 STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
62 STATISTIC(NumRetsDup, "Number of return instructions duplicated");
63 STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
64 STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
66 static cl::opt<bool> DisableBranchOpts(
67 "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
68 cl::desc("Disable branch optimizations in CodeGenPrepare"));
70 static cl::opt<bool> DisableSelectToBranch(
71 "disable-cgp-select2branch", cl::Hidden, cl::init(false),
72 cl::desc("Disable select to branch conversion."));
75 class CodeGenPrepare : public FunctionPass {
76 /// TLI - Keep a pointer of a TargetLowering to consult for determining
77 /// transformation profitability.
78 const TargetLowering *TLI;
79 const TargetLibraryInfo *TLInfo;
83 /// CurInstIterator - As we scan instructions optimizing them, this is the
84 /// next instruction to optimize. Xforms that can invalidate this should
86 BasicBlock::iterator CurInstIterator;
88 /// Keeps track of non-local addresses that have been sunk into a block.
89 /// This allows us to avoid inserting duplicate code for blocks with
90 /// multiple load/stores of the same address.
91 DenseMap<Value*, Value*> SunkAddrs;
93 /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
97 /// OptSize - True if optimizing for size.
101 static char ID; // Pass identification, replacement for typeid
102 explicit CodeGenPrepare(const TargetLowering *tli = 0)
103 : FunctionPass(ID), TLI(tli) {
104 initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
106 bool runOnFunction(Function &F);
108 const char *getPassName() const { return "CodeGen Prepare"; }
110 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
111 AU.addPreserved<DominatorTree>();
112 AU.addPreserved<ProfileInfo>();
113 AU.addRequired<TargetLibraryInfo>();
117 bool EliminateFallThrough(Function &F);
118 bool EliminateMostlyEmptyBlocks(Function &F);
119 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
120 void EliminateMostlyEmptyBlock(BasicBlock *BB);
121 bool OptimizeBlock(BasicBlock &BB);
122 bool OptimizeInst(Instruction *I);
123 bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy);
124 bool OptimizeInlineAsmInst(CallInst *CS);
125 bool OptimizeCallInst(CallInst *CI);
126 bool MoveExtToFormExtLoad(Instruction *I);
127 bool OptimizeExtUses(Instruction *I);
128 bool OptimizeSelectInst(SelectInst *SI);
129 bool DupRetToEnableTailCallOpts(BasicBlock *BB);
130 bool PlaceDbgValues(Function &F);
134 char CodeGenPrepare::ID = 0;
135 INITIALIZE_PASS_BEGIN(CodeGenPrepare, "codegenprepare",
136 "Optimize for code generation", false, false)
137 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
138 INITIALIZE_PASS_END(CodeGenPrepare, "codegenprepare",
139 "Optimize for code generation", false, false)
141 FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
142 return new CodeGenPrepare(TLI);
145 bool CodeGenPrepare::runOnFunction(Function &F) {
146 bool EverMadeChange = false;
149 TLInfo = &getAnalysis<TargetLibraryInfo>();
150 DT = getAnalysisIfAvailable<DominatorTree>();
151 PFI = getAnalysisIfAvailable<ProfileInfo>();
152 OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
153 Attribute::OptimizeForSize);
155 /// This optimization identifies DIV instructions that can be
156 /// profitably bypassed and carried out with a shorter, faster divide.
157 if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
158 const DenseMap<unsigned int, unsigned int> &BypassWidths =
159 TLI->getBypassSlowDivWidths();
160 for (Function::iterator I = F.begin(); I != F.end(); I++)
161 EverMadeChange |= bypassSlowDivision(F, I, BypassWidths);
164 // Eliminate blocks that contain only PHI nodes and an
165 // unconditional branch.
166 EverMadeChange |= EliminateMostlyEmptyBlocks(F);
168 // llvm.dbg.value is far away from the value then iSel may not be able
169 // handle it properly. iSel will drop llvm.dbg.value if it can not
170 // find a node corresponding to the value.
171 EverMadeChange |= PlaceDbgValues(F);
173 bool MadeChange = true;
176 for (Function::iterator I = F.begin(); I != F.end(); ) {
177 BasicBlock *BB = I++;
178 MadeChange |= OptimizeBlock(*BB);
180 EverMadeChange |= MadeChange;
185 if (!DisableBranchOpts) {
187 SmallPtrSet<BasicBlock*, 8> WorkList;
188 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
189 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
190 MadeChange |= ConstantFoldTerminator(BB, true);
191 if (!MadeChange) continue;
193 for (SmallVectorImpl<BasicBlock*>::iterator
194 II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
195 if (pred_begin(*II) == pred_end(*II))
196 WorkList.insert(*II);
199 // Delete the dead blocks and any of their dead successors.
200 MadeChange |= !WorkList.empty();
201 while (!WorkList.empty()) {
202 BasicBlock *BB = *WorkList.begin();
204 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
208 for (SmallVectorImpl<BasicBlock*>::iterator
209 II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
210 if (pred_begin(*II) == pred_end(*II))
211 WorkList.insert(*II);
214 // Merge pairs of basic blocks with unconditional branches, connected by
216 if (EverMadeChange || MadeChange)
217 MadeChange |= EliminateFallThrough(F);
221 EverMadeChange |= MadeChange;
224 if (ModifiedDT && DT)
225 DT->DT->recalculate(F);
227 return EverMadeChange;
230 /// EliminateFallThrough - Merge basic blocks which are connected
231 /// by a single edge, where one of the basic blocks has a single successor
232 /// pointing to the other basic block, which has a single predecessor.
233 bool CodeGenPrepare::EliminateFallThrough(Function &F) {
234 bool Changed = false;
235 // Scan all of the blocks in the function, except for the entry block.
236 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
237 BasicBlock *BB = I++;
238 // If the destination block has a single pred, then this is a trivial
239 // edge, just collapse it.
240 BasicBlock *SinglePred = BB->getSinglePredecessor();
242 // Don't merge if BB's address is taken.
243 if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue;
245 BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
246 if (Term && !Term->isConditional()) {
248 DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
249 // Remember if SinglePred was the entry block of the function.
250 // If so, we will need to move BB back to the entry position.
251 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
252 MergeBasicBlockIntoOnlyPred(BB, this);
254 if (isEntry && BB != &BB->getParent()->getEntryBlock())
255 BB->moveBefore(&BB->getParent()->getEntryBlock());
257 // We have erased a block. Update the iterator.
264 /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
265 /// debug info directives, and an unconditional branch. Passes before isel
266 /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
267 /// isel. Start by eliminating these blocks so we can split them the way we
269 bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
270 bool MadeChange = false;
271 // Note that this intentionally skips the entry block.
272 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
273 BasicBlock *BB = I++;
275 // If this block doesn't end with an uncond branch, ignore it.
276 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
277 if (!BI || !BI->isUnconditional())
280 // If the instruction before the branch (skipping debug info) isn't a phi
281 // node, then other stuff is happening here.
282 BasicBlock::iterator BBI = BI;
283 if (BBI != BB->begin()) {
285 while (isa<DbgInfoIntrinsic>(BBI)) {
286 if (BBI == BB->begin())
290 if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
294 // Do not break infinite loops.
295 BasicBlock *DestBB = BI->getSuccessor(0);
299 if (!CanMergeBlocks(BB, DestBB))
302 EliminateMostlyEmptyBlock(BB);
308 /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
309 /// single uncond branch between them, and BB contains no other non-phi
311 bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
312 const BasicBlock *DestBB) const {
313 // We only want to eliminate blocks whose phi nodes are used by phi nodes in
314 // the successor. If there are more complex condition (e.g. preheaders),
315 // don't mess around with them.
316 BasicBlock::const_iterator BBI = BB->begin();
317 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
318 for (Value::const_use_iterator UI = PN->use_begin(), E = PN->use_end();
320 const Instruction *User = cast<Instruction>(*UI);
321 if (User->getParent() != DestBB || !isa<PHINode>(User))
323 // If User is inside DestBB block and it is a PHINode then check
324 // incoming value. If incoming value is not from BB then this is
325 // a complex condition (e.g. preheaders) we want to avoid here.
326 if (User->getParent() == DestBB) {
327 if (const PHINode *UPN = dyn_cast<PHINode>(User))
328 for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
329 Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
330 if (Insn && Insn->getParent() == BB &&
331 Insn->getParent() != UPN->getIncomingBlock(I))
338 // If BB and DestBB contain any common predecessors, then the phi nodes in BB
339 // and DestBB may have conflicting incoming values for the block. If so, we
340 // can't merge the block.
341 const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
342 if (!DestBBPN) return true; // no conflict.
344 // Collect the preds of BB.
345 SmallPtrSet<const BasicBlock*, 16> BBPreds;
346 if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
347 // It is faster to get preds from a PHI than with pred_iterator.
348 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
349 BBPreds.insert(BBPN->getIncomingBlock(i));
351 BBPreds.insert(pred_begin(BB), pred_end(BB));
354 // Walk the preds of DestBB.
355 for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
356 BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
357 if (BBPreds.count(Pred)) { // Common predecessor?
358 BBI = DestBB->begin();
359 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
360 const Value *V1 = PN->getIncomingValueForBlock(Pred);
361 const Value *V2 = PN->getIncomingValueForBlock(BB);
363 // If V2 is a phi node in BB, look up what the mapped value will be.
364 if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
365 if (V2PN->getParent() == BB)
366 V2 = V2PN->getIncomingValueForBlock(Pred);
368 // If there is a conflict, bail out.
369 if (V1 != V2) return false;
378 /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
379 /// an unconditional branch in it.
380 void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
381 BranchInst *BI = cast<BranchInst>(BB->getTerminator());
382 BasicBlock *DestBB = BI->getSuccessor(0);
384 DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
386 // If the destination block has a single pred, then this is a trivial edge,
388 if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
389 if (SinglePred != DestBB) {
390 // Remember if SinglePred was the entry block of the function. If so, we
391 // will need to move BB back to the entry position.
392 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
393 MergeBasicBlockIntoOnlyPred(DestBB, this);
395 if (isEntry && BB != &BB->getParent()->getEntryBlock())
396 BB->moveBefore(&BB->getParent()->getEntryBlock());
398 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
403 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
404 // to handle the new incoming edges it is about to have.
406 for (BasicBlock::iterator BBI = DestBB->begin();
407 (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
408 // Remove the incoming value for BB, and remember it.
409 Value *InVal = PN->removeIncomingValue(BB, false);
411 // Two options: either the InVal is a phi node defined in BB or it is some
412 // value that dominates BB.
413 PHINode *InValPhi = dyn_cast<PHINode>(InVal);
414 if (InValPhi && InValPhi->getParent() == BB) {
415 // Add all of the input values of the input PHI as inputs of this phi.
416 for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
417 PN->addIncoming(InValPhi->getIncomingValue(i),
418 InValPhi->getIncomingBlock(i));
420 // Otherwise, add one instance of the dominating value for each edge that
421 // we will be adding.
422 if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
423 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
424 PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
426 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
427 PN->addIncoming(InVal, *PI);
432 // The PHIs are now updated, change everything that refers to BB to use
433 // DestBB and remove BB.
434 BB->replaceAllUsesWith(DestBB);
435 if (DT && !ModifiedDT) {
436 BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock();
437 BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
438 BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
439 DT->changeImmediateDominator(DestBB, NewIDom);
443 PFI->replaceAllUses(BB, DestBB);
444 PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
446 BB->eraseFromParent();
449 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
452 /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
453 /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
454 /// sink it into user blocks to reduce the number of virtual
455 /// registers that must be created and coalesced.
457 /// Return true if any changes are made.
459 static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
460 // If this is a noop copy,
461 EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
462 EVT DstVT = TLI.getValueType(CI->getType());
464 // This is an fp<->int conversion?
465 if (SrcVT.isInteger() != DstVT.isInteger())
468 // If this is an extension, it will be a zero or sign extension, which
470 if (SrcVT.bitsLT(DstVT)) return false;
472 // If these values will be promoted, find out what they will be promoted
473 // to. This helps us consider truncates on PPC as noop copies when they
475 if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
476 TargetLowering::TypePromoteInteger)
477 SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
478 if (TLI.getTypeAction(CI->getContext(), DstVT) ==
479 TargetLowering::TypePromoteInteger)
480 DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
482 // If, after promotion, these are the same types, this is a noop copy.
486 BasicBlock *DefBB = CI->getParent();
488 /// InsertedCasts - Only insert a cast in each block once.
489 DenseMap<BasicBlock*, CastInst*> InsertedCasts;
491 bool MadeChange = false;
492 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
494 Use &TheUse = UI.getUse();
495 Instruction *User = cast<Instruction>(*UI);
497 // Figure out which BB this cast is used in. For PHI's this is the
498 // appropriate predecessor block.
499 BasicBlock *UserBB = User->getParent();
500 if (PHINode *PN = dyn_cast<PHINode>(User)) {
501 UserBB = PN->getIncomingBlock(UI);
504 // Preincrement use iterator so we don't invalidate it.
507 // If this user is in the same block as the cast, don't change the cast.
508 if (UserBB == DefBB) continue;
510 // If we have already inserted a cast into this block, use it.
511 CastInst *&InsertedCast = InsertedCasts[UserBB];
514 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
516 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
521 // Replace a use of the cast with a use of the new cast.
522 TheUse = InsertedCast;
526 // If we removed all uses, nuke the cast.
527 if (CI->use_empty()) {
528 CI->eraseFromParent();
535 /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
536 /// the number of virtual registers that must be created and coalesced. This is
537 /// a clear win except on targets with multiple condition code registers
538 /// (PowerPC), where it might lose; some adjustment may be wanted there.
540 /// Return true if any changes are made.
541 static bool OptimizeCmpExpression(CmpInst *CI) {
542 BasicBlock *DefBB = CI->getParent();
544 /// InsertedCmp - Only insert a cmp in each block once.
545 DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
547 bool MadeChange = false;
548 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
550 Use &TheUse = UI.getUse();
551 Instruction *User = cast<Instruction>(*UI);
553 // Preincrement use iterator so we don't invalidate it.
556 // Don't bother for PHI nodes.
557 if (isa<PHINode>(User))
560 // Figure out which BB this cmp is used in.
561 BasicBlock *UserBB = User->getParent();
563 // If this user is in the same block as the cmp, don't change the cmp.
564 if (UserBB == DefBB) continue;
566 // If we have already inserted a cmp into this block, use it.
567 CmpInst *&InsertedCmp = InsertedCmps[UserBB];
570 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
572 CmpInst::Create(CI->getOpcode(),
573 CI->getPredicate(), CI->getOperand(0),
574 CI->getOperand(1), "", InsertPt);
578 // Replace a use of the cmp with a use of the new cmp.
579 TheUse = InsertedCmp;
583 // If we removed all uses, nuke the cmp.
585 CI->eraseFromParent();
591 class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls {
593 void replaceCall(Value *With) {
594 CI->replaceAllUsesWith(With);
595 CI->eraseFromParent();
597 bool isFoldable(unsigned SizeCIOp, unsigned, bool) const {
598 if (ConstantInt *SizeCI =
599 dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp)))
600 return SizeCI->isAllOnesValue();
604 } // end anonymous namespace
606 bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
607 BasicBlock *BB = CI->getParent();
609 // Lower inline assembly if we can.
610 // If we found an inline asm expession, and if the target knows how to
611 // lower it to normal LLVM code, do so now.
612 if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
613 if (TLI->ExpandInlineAsm(CI)) {
614 // Avoid invalidating the iterator.
615 CurInstIterator = BB->begin();
616 // Avoid processing instructions out of order, which could cause
617 // reuse before a value is defined.
621 // Sink address computing for memory operands into the block.
622 if (OptimizeInlineAsmInst(CI))
626 // Lower all uses of llvm.objectsize.*
627 IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
628 if (II && II->getIntrinsicID() == Intrinsic::objectsize) {
629 bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
630 Type *ReturnTy = CI->getType();
631 Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
633 // Substituting this can cause recursive simplifications, which can
634 // invalidate our iterator. Use a WeakVH to hold onto it in case this
636 WeakVH IterHandle(CurInstIterator);
638 replaceAndRecursivelySimplify(CI, RetVal, TLI ? TLI->getDataLayout() : 0,
639 TLInfo, ModifiedDT ? 0 : DT);
641 // If the iterator instruction was recursively deleted, start over at the
642 // start of the block.
643 if (IterHandle != CurInstIterator) {
644 CurInstIterator = BB->begin();
651 SmallVector<Value*, 2> PtrOps;
653 if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy))
654 while (!PtrOps.empty())
655 if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy))
659 // From here on out we're working with named functions.
660 if (CI->getCalledFunction() == 0) return false;
662 // We'll need DataLayout from here on out.
663 const DataLayout *TD = TLI ? TLI->getDataLayout() : 0;
664 if (!TD) return false;
666 // Lower all default uses of _chk calls. This is very similar
667 // to what InstCombineCalls does, but here we are only lowering calls
668 // that have the default "don't know" as the objectsize. Anything else
669 // should be left alone.
670 CodeGenPrepareFortifiedLibCalls Simplifier;
671 return Simplifier.fold(CI, TD, TLInfo);
674 /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
675 /// instructions to the predecessor to enable tail call optimizations. The
676 /// case it is currently looking for is:
679 /// %tmp0 = tail call i32 @f0()
682 /// %tmp1 = tail call i32 @f1()
685 /// %tmp2 = tail call i32 @f2()
688 /// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
696 /// %tmp0 = tail call i32 @f0()
699 /// %tmp1 = tail call i32 @f1()
702 /// %tmp2 = tail call i32 @f2()
705 bool CodeGenPrepare::DupRetToEnableTailCallOpts(BasicBlock *BB) {
709 ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
714 BitCastInst *BCI = 0;
715 Value *V = RI->getReturnValue();
717 BCI = dyn_cast<BitCastInst>(V);
719 V = BCI->getOperand(0);
721 PN = dyn_cast<PHINode>(V);
726 if (PN && PN->getParent() != BB)
729 // It's not safe to eliminate the sign / zero extension of the return value.
730 // See llvm::isInTailCallPosition().
731 const Function *F = BB->getParent();
732 AttributeSet CallerAttrs = F->getAttributes();
733 if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
734 CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
737 // Make sure there are no instructions between the PHI and return, or that the
738 // return is the first instruction in the block.
740 BasicBlock::iterator BI = BB->begin();
741 do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
743 // Also skip over the bitcast.
748 BasicBlock::iterator BI = BB->begin();
749 while (isa<DbgInfoIntrinsic>(BI)) ++BI;
754 /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
756 SmallVector<CallInst*, 4> TailCalls;
758 for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
759 CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
760 // Make sure the phi value is indeed produced by the tail call.
761 if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
762 TLI->mayBeEmittedAsTailCall(CI))
763 TailCalls.push_back(CI);
766 SmallPtrSet<BasicBlock*, 4> VisitedBBs;
767 for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
768 if (!VisitedBBs.insert(*PI))
771 BasicBlock::InstListType &InstList = (*PI)->getInstList();
772 BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
773 BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
774 do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
778 CallInst *CI = dyn_cast<CallInst>(&*RI);
779 if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
780 TailCalls.push_back(CI);
784 bool Changed = false;
785 for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
786 CallInst *CI = TailCalls[i];
789 // Conservatively require the attributes of the call to match those of the
790 // return. Ignore noalias because it doesn't affect the call sequence.
791 AttributeSet CalleeAttrs = CS.getAttributes();
792 if (AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
793 removeAttribute(Attribute::NoAlias) !=
794 AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
795 removeAttribute(Attribute::NoAlias))
798 // Make sure the call instruction is followed by an unconditional branch to
800 BasicBlock *CallBB = CI->getParent();
801 BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
802 if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
805 // Duplicate the return into CallBB.
806 (void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
807 ModifiedDT = Changed = true;
811 // If we eliminated all predecessors of the block, delete the block now.
812 if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
813 BB->eraseFromParent();
818 //===----------------------------------------------------------------------===//
819 // Memory Optimization
820 //===----------------------------------------------------------------------===//
824 /// ExtAddrMode - This is an extended version of TargetLowering::AddrMode
825 /// which holds actual Value*'s for register values.
826 struct ExtAddrMode : public TargetLowering::AddrMode {
829 ExtAddrMode() : BaseReg(0), ScaledReg(0) {}
830 void print(raw_ostream &OS) const;
833 bool operator==(const ExtAddrMode& O) const {
834 return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) &&
835 (BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) &&
836 (HasBaseReg == O.HasBaseReg) && (Scale == O.Scale);
840 static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
845 void ExtAddrMode::print(raw_ostream &OS) const {
846 bool NeedPlus = false;
849 OS << (NeedPlus ? " + " : "")
851 WriteAsOperand(OS, BaseGV, /*PrintType=*/false);
856 OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true;
859 OS << (NeedPlus ? " + " : "")
861 WriteAsOperand(OS, BaseReg, /*PrintType=*/false);
865 OS << (NeedPlus ? " + " : "")
867 WriteAsOperand(OS, ScaledReg, /*PrintType=*/false);
874 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
875 void ExtAddrMode::dump() const {
882 /// \brief A helper class for matching addressing modes.
884 /// This encapsulates the logic for matching the target-legal addressing modes.
885 class AddressingModeMatcher {
886 SmallVectorImpl<Instruction*> &AddrModeInsts;
887 const TargetLowering &TLI;
889 /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
890 /// the memory instruction that we're computing this address for.
892 Instruction *MemoryInst;
894 /// AddrMode - This is the addressing mode that we're building up. This is
895 /// part of the return value of this addressing mode matching stuff.
896 ExtAddrMode &AddrMode;
898 /// IgnoreProfitability - This is set to true when we should not do
899 /// profitability checks. When true, IsProfitableToFoldIntoAddressingMode
900 /// always returns true.
901 bool IgnoreProfitability;
903 AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI,
904 const TargetLowering &T, Type *AT,
905 Instruction *MI, ExtAddrMode &AM)
906 : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM) {
907 IgnoreProfitability = false;
911 /// Match - Find the maximal addressing mode that a load/store of V can fold,
912 /// give an access type of AccessTy. This returns a list of involved
913 /// instructions in AddrModeInsts.
914 static ExtAddrMode Match(Value *V, Type *AccessTy,
915 Instruction *MemoryInst,
916 SmallVectorImpl<Instruction*> &AddrModeInsts,
917 const TargetLowering &TLI) {
921 AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
922 MemoryInst, Result).MatchAddr(V, 0);
923 (void)Success; assert(Success && "Couldn't select *anything*?");
927 bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
928 bool MatchAddr(Value *V, unsigned Depth);
929 bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth);
930 bool IsProfitableToFoldIntoAddressingMode(Instruction *I,
931 ExtAddrMode &AMBefore,
932 ExtAddrMode &AMAfter);
933 bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
936 /// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode.
937 /// Return true and update AddrMode if this addr mode is legal for the target,
939 bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale,
941 // If Scale is 1, then this is the same as adding ScaleReg to the addressing
942 // mode. Just process that directly.
944 return MatchAddr(ScaleReg, Depth);
946 // If the scale is 0, it takes nothing to add this.
950 // If we already have a scale of this value, we can add to it, otherwise, we
951 // need an available scale field.
952 if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
955 ExtAddrMode TestAddrMode = AddrMode;
957 // Add scale to turn X*4+X*3 -> X*7. This could also do things like
958 // [A+B + A*7] -> [B+A*8].
959 TestAddrMode.Scale += Scale;
960 TestAddrMode.ScaledReg = ScaleReg;
962 // If the new address isn't legal, bail out.
963 if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy))
966 // It was legal, so commit it.
967 AddrMode = TestAddrMode;
969 // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
970 // to see if ScaleReg is actually X+C. If so, we can turn this into adding
971 // X*Scale + C*Scale to addr mode.
972 ConstantInt *CI = 0; Value *AddLHS = 0;
973 if (isa<Instruction>(ScaleReg) && // not a constant expr.
974 match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
975 TestAddrMode.ScaledReg = AddLHS;
976 TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
978 // If this addressing mode is legal, commit it and remember that we folded
980 if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) {
981 AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
982 AddrMode = TestAddrMode;
987 // Otherwise, not (x+c)*scale, just return what we have.
991 /// MightBeFoldableInst - This is a little filter, which returns true if an
992 /// addressing computation involving I might be folded into a load/store
993 /// accessing it. This doesn't need to be perfect, but needs to accept at least
994 /// the set of instructions that MatchOperationAddr can.
995 static bool MightBeFoldableInst(Instruction *I) {
996 switch (I->getOpcode()) {
997 case Instruction::BitCast:
998 // Don't touch identity bitcasts.
999 if (I->getType() == I->getOperand(0)->getType())
1001 return I->getType()->isPointerTy() || I->getType()->isIntegerTy();
1002 case Instruction::PtrToInt:
1003 // PtrToInt is always a noop, as we know that the int type is pointer sized.
1005 case Instruction::IntToPtr:
1006 // We know the input is intptr_t, so this is foldable.
1008 case Instruction::Add:
1010 case Instruction::Mul:
1011 case Instruction::Shl:
1012 // Can only handle X*C and X << C.
1013 return isa<ConstantInt>(I->getOperand(1));
1014 case Instruction::GetElementPtr:
1021 /// MatchOperationAddr - Given an instruction or constant expr, see if we can
1022 /// fold the operation into the addressing mode. If so, update the addressing
1023 /// mode and return true, otherwise return false without modifying AddrMode.
1024 bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
1026 // Avoid exponential behavior on extremely deep expression trees.
1027 if (Depth >= 5) return false;
1030 case Instruction::PtrToInt:
1031 // PtrToInt is always a noop, as we know that the int type is pointer sized.
1032 return MatchAddr(AddrInst->getOperand(0), Depth);
1033 case Instruction::IntToPtr:
1034 // This inttoptr is a no-op if the integer type is pointer sized.
1035 if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
1037 return MatchAddr(AddrInst->getOperand(0), Depth);
1039 case Instruction::BitCast:
1040 // BitCast is always a noop, and we can handle it as long as it is
1041 // int->int or pointer->pointer (we don't want int<->fp or something).
1042 if ((AddrInst->getOperand(0)->getType()->isPointerTy() ||
1043 AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
1044 // Don't touch identity bitcasts. These were probably put here by LSR,
1045 // and we don't want to mess around with them. Assume it knows what it
1047 AddrInst->getOperand(0)->getType() != AddrInst->getType())
1048 return MatchAddr(AddrInst->getOperand(0), Depth);
1050 case Instruction::Add: {
1051 // Check to see if we can merge in the RHS then the LHS. If so, we win.
1052 ExtAddrMode BackupAddrMode = AddrMode;
1053 unsigned OldSize = AddrModeInsts.size();
1054 if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
1055 MatchAddr(AddrInst->getOperand(0), Depth+1))
1058 // Restore the old addr mode info.
1059 AddrMode = BackupAddrMode;
1060 AddrModeInsts.resize(OldSize);
1062 // Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
1063 if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
1064 MatchAddr(AddrInst->getOperand(1), Depth+1))
1067 // Otherwise we definitely can't merge the ADD in.
1068 AddrMode = BackupAddrMode;
1069 AddrModeInsts.resize(OldSize);
1072 //case Instruction::Or:
1073 // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
1075 case Instruction::Mul:
1076 case Instruction::Shl: {
1077 // Can only handle X*C and X << C.
1078 ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
1079 if (!RHS) return false;
1080 int64_t Scale = RHS->getSExtValue();
1081 if (Opcode == Instruction::Shl)
1082 Scale = 1LL << Scale;
1084 return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth);
1086 case Instruction::GetElementPtr: {
1087 // Scan the GEP. We check it if it contains constant offsets and at most
1088 // one variable offset.
1089 int VariableOperand = -1;
1090 unsigned VariableScale = 0;
1092 int64_t ConstantOffset = 0;
1093 const DataLayout *TD = TLI.getDataLayout();
1094 gep_type_iterator GTI = gep_type_begin(AddrInst);
1095 for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
1096 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
1097 const StructLayout *SL = TD->getStructLayout(STy);
1099 cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
1100 ConstantOffset += SL->getElementOffset(Idx);
1102 uint64_t TypeSize = TD->getTypeAllocSize(GTI.getIndexedType());
1103 if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
1104 ConstantOffset += CI->getSExtValue()*TypeSize;
1105 } else if (TypeSize) { // Scales of zero don't do anything.
1106 // We only allow one variable index at the moment.
1107 if (VariableOperand != -1)
1110 // Remember the variable index.
1111 VariableOperand = i;
1112 VariableScale = TypeSize;
1117 // A common case is for the GEP to only do a constant offset. In this case,
1118 // just add it to the disp field and check validity.
1119 if (VariableOperand == -1) {
1120 AddrMode.BaseOffs += ConstantOffset;
1121 if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
1122 // Check to see if we can fold the base pointer in too.
1123 if (MatchAddr(AddrInst->getOperand(0), Depth+1))
1126 AddrMode.BaseOffs -= ConstantOffset;
1130 // Save the valid addressing mode in case we can't match.
1131 ExtAddrMode BackupAddrMode = AddrMode;
1132 unsigned OldSize = AddrModeInsts.size();
1134 // See if the scale and offset amount is valid for this target.
1135 AddrMode.BaseOffs += ConstantOffset;
1137 // Match the base operand of the GEP.
1138 if (!MatchAddr(AddrInst->getOperand(0), Depth+1)) {
1139 // If it couldn't be matched, just stuff the value in a register.
1140 if (AddrMode.HasBaseReg) {
1141 AddrMode = BackupAddrMode;
1142 AddrModeInsts.resize(OldSize);
1145 AddrMode.HasBaseReg = true;
1146 AddrMode.BaseReg = AddrInst->getOperand(0);
1149 // Match the remaining variable portion of the GEP.
1150 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
1152 // If it couldn't be matched, try stuffing the base into a register
1153 // instead of matching it, and retrying the match of the scale.
1154 AddrMode = BackupAddrMode;
1155 AddrModeInsts.resize(OldSize);
1156 if (AddrMode.HasBaseReg)
1158 AddrMode.HasBaseReg = true;
1159 AddrMode.BaseReg = AddrInst->getOperand(0);
1160 AddrMode.BaseOffs += ConstantOffset;
1161 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand),
1162 VariableScale, Depth)) {
1163 // If even that didn't work, bail.
1164 AddrMode = BackupAddrMode;
1165 AddrModeInsts.resize(OldSize);
1176 /// MatchAddr - If we can, try to add the value of 'Addr' into the current
1177 /// addressing mode. If Addr can't be added to AddrMode this returns false and
1178 /// leaves AddrMode unmodified. This assumes that Addr is either a pointer type
1179 /// or intptr_t for the target.
1181 bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
1182 if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
1183 // Fold in immediates if legal for the target.
1184 AddrMode.BaseOffs += CI->getSExtValue();
1185 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
1187 AddrMode.BaseOffs -= CI->getSExtValue();
1188 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
1189 // If this is a global variable, try to fold it into the addressing mode.
1190 if (AddrMode.BaseGV == 0) {
1191 AddrMode.BaseGV = GV;
1192 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
1194 AddrMode.BaseGV = 0;
1196 } else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
1197 ExtAddrMode BackupAddrMode = AddrMode;
1198 unsigned OldSize = AddrModeInsts.size();
1200 // Check to see if it is possible to fold this operation.
1201 if (MatchOperationAddr(I, I->getOpcode(), Depth)) {
1202 // Okay, it's possible to fold this. Check to see if it is actually
1203 // *profitable* to do so. We use a simple cost model to avoid increasing
1204 // register pressure too much.
1205 if (I->hasOneUse() ||
1206 IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
1207 AddrModeInsts.push_back(I);
1211 // It isn't profitable to do this, roll back.
1212 //cerr << "NOT FOLDING: " << *I;
1213 AddrMode = BackupAddrMode;
1214 AddrModeInsts.resize(OldSize);
1216 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
1217 if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
1219 } else if (isa<ConstantPointerNull>(Addr)) {
1220 // Null pointer gets folded without affecting the addressing mode.
1224 // Worse case, the target should support [reg] addressing modes. :)
1225 if (!AddrMode.HasBaseReg) {
1226 AddrMode.HasBaseReg = true;
1227 AddrMode.BaseReg = Addr;
1228 // Still check for legality in case the target supports [imm] but not [i+r].
1229 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
1231 AddrMode.HasBaseReg = false;
1232 AddrMode.BaseReg = 0;
1235 // If the base register is already taken, see if we can do [r+r].
1236 if (AddrMode.Scale == 0) {
1238 AddrMode.ScaledReg = Addr;
1239 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
1242 AddrMode.ScaledReg = 0;
1248 /// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified
1249 /// inline asm call are due to memory operands. If so, return true, otherwise
1251 static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
1252 const TargetLowering &TLI) {
1253 TargetLowering::AsmOperandInfoVector TargetConstraints = TLI.ParseConstraints(ImmutableCallSite(CI));
1254 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
1255 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
1257 // Compute the constraint code and ConstraintType to use.
1258 TLI.ComputeConstraintToUse(OpInfo, SDValue());
1260 // If this asm operand is our Value*, and if it isn't an indirect memory
1261 // operand, we can't fold it!
1262 if (OpInfo.CallOperandVal == OpVal &&
1263 (OpInfo.ConstraintType != TargetLowering::C_Memory ||
1264 !OpInfo.isIndirect))
1271 /// FindAllMemoryUses - Recursively walk all the uses of I until we find a
1272 /// memory use. If we find an obviously non-foldable instruction, return true.
1273 /// Add the ultimately found memory instructions to MemoryUses.
1274 static bool FindAllMemoryUses(Instruction *I,
1275 SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
1276 SmallPtrSet<Instruction*, 16> &ConsideredInsts,
1277 const TargetLowering &TLI) {
1278 // If we already considered this instruction, we're done.
1279 if (!ConsideredInsts.insert(I))
1282 // If this is an obviously unfoldable instruction, bail out.
1283 if (!MightBeFoldableInst(I))
1286 // Loop over all the uses, recursively processing them.
1287 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
1291 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1292 MemoryUses.push_back(std::make_pair(LI, UI.getOperandNo()));
1296 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1297 unsigned opNo = UI.getOperandNo();
1298 if (opNo == 0) return true; // Storing addr, not into addr.
1299 MemoryUses.push_back(std::make_pair(SI, opNo));
1303 if (CallInst *CI = dyn_cast<CallInst>(U)) {
1304 InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
1305 if (!IA) return true;
1307 // If this is a memory operand, we're cool, otherwise bail out.
1308 if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
1313 if (FindAllMemoryUses(cast<Instruction>(U), MemoryUses, ConsideredInsts,
1321 /// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at
1322 /// the use site that we're folding it into. If so, there is no cost to
1323 /// include it in the addressing mode. KnownLive1 and KnownLive2 are two values
1324 /// that we know are live at the instruction already.
1325 bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
1326 Value *KnownLive2) {
1327 // If Val is either of the known-live values, we know it is live!
1328 if (Val == 0 || Val == KnownLive1 || Val == KnownLive2)
1331 // All values other than instructions and arguments (e.g. constants) are live.
1332 if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
1334 // If Val is a constant sized alloca in the entry block, it is live, this is
1335 // true because it is just a reference to the stack/frame pointer, which is
1336 // live for the whole function.
1337 if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
1338 if (AI->isStaticAlloca())
1341 // Check to see if this value is already used in the memory instruction's
1342 // block. If so, it's already live into the block at the very least, so we
1343 // can reasonably fold it.
1344 return Val->isUsedInBasicBlock(MemoryInst->getParent());
1347 /// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing
1348 /// mode of the machine to fold the specified instruction into a load or store
1349 /// that ultimately uses it. However, the specified instruction has multiple
1350 /// uses. Given this, it may actually increase register pressure to fold it
1351 /// into the load. For example, consider this code:
1355 /// use(Y) -> nonload/store
1359 /// In this case, Y has multiple uses, and can be folded into the load of Z
1360 /// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
1361 /// be live at the use(Y) line. If we don't fold Y into load Z, we use one
1362 /// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
1363 /// number of computations either.
1365 /// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
1366 /// X was live across 'load Z' for other reasons, we actually *would* want to
1367 /// fold the addressing mode in the Z case. This would make Y die earlier.
1368 bool AddressingModeMatcher::
1369 IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
1370 ExtAddrMode &AMAfter) {
1371 if (IgnoreProfitability) return true;
1373 // AMBefore is the addressing mode before this instruction was folded into it,
1374 // and AMAfter is the addressing mode after the instruction was folded. Get
1375 // the set of registers referenced by AMAfter and subtract out those
1376 // referenced by AMBefore: this is the set of values which folding in this
1377 // address extends the lifetime of.
1379 // Note that there are only two potential values being referenced here,
1380 // BaseReg and ScaleReg (global addresses are always available, as are any
1381 // folded immediates).
1382 Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
1384 // If the BaseReg or ScaledReg was referenced by the previous addrmode, their
1385 // lifetime wasn't extended by adding this instruction.
1386 if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
1388 if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
1391 // If folding this instruction (and it's subexprs) didn't extend any live
1392 // ranges, we're ok with it.
1393 if (BaseReg == 0 && ScaledReg == 0)
1396 // If all uses of this instruction are ultimately load/store/inlineasm's,
1397 // check to see if their addressing modes will include this instruction. If
1398 // so, we can fold it into all uses, so it doesn't matter if it has multiple
1400 SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
1401 SmallPtrSet<Instruction*, 16> ConsideredInsts;
1402 if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
1403 return false; // Has a non-memory, non-foldable use!
1405 // Now that we know that all uses of this instruction are part of a chain of
1406 // computation involving only operations that could theoretically be folded
1407 // into a memory use, loop over each of these uses and see if they could
1408 // *actually* fold the instruction.
1409 SmallVector<Instruction*, 32> MatchedAddrModeInsts;
1410 for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
1411 Instruction *User = MemoryUses[i].first;
1412 unsigned OpNo = MemoryUses[i].second;
1414 // Get the access type of this use. If the use isn't a pointer, we don't
1415 // know what it accesses.
1416 Value *Address = User->getOperand(OpNo);
1417 if (!Address->getType()->isPointerTy())
1419 Type *AddressAccessTy =
1420 cast<PointerType>(Address->getType())->getElementType();
1422 // Do a match against the root of this address, ignoring profitability. This
1423 // will tell us if the addressing mode for the memory operation will
1424 // *actually* cover the shared instruction.
1426 AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
1427 MemoryInst, Result);
1428 Matcher.IgnoreProfitability = true;
1429 bool Success = Matcher.MatchAddr(Address, 0);
1430 (void)Success; assert(Success && "Couldn't select *anything*?");
1432 // If the match didn't cover I, then it won't be shared by it.
1433 if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
1434 I) == MatchedAddrModeInsts.end())
1437 MatchedAddrModeInsts.clear();
1443 } // end anonymous namespace
1445 /// IsNonLocalValue - Return true if the specified values are defined in a
1446 /// different basic block than BB.
1447 static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
1448 if (Instruction *I = dyn_cast<Instruction>(V))
1449 return I->getParent() != BB;
1453 /// OptimizeMemoryInst - Load and Store Instructions often have
1454 /// addressing modes that can do significant amounts of computation. As such,
1455 /// instruction selection will try to get the load or store to do as much
1456 /// computation as possible for the program. The problem is that isel can only
1457 /// see within a single block. As such, we sink as much legal addressing mode
1458 /// stuff into the block as possible.
1460 /// This method is used to optimize both load/store and inline asms with memory
1462 bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
1466 // Try to collapse single-value PHI nodes. This is necessary to undo
1467 // unprofitable PRE transformations.
1468 SmallVector<Value*, 8> worklist;
1469 SmallPtrSet<Value*, 16> Visited;
1470 worklist.push_back(Addr);
1472 // Use a worklist to iteratively look through PHI nodes, and ensure that
1473 // the addressing mode obtained from the non-PHI roots of the graph
1475 Value *Consensus = 0;
1476 unsigned NumUsesConsensus = 0;
1477 bool IsNumUsesConsensusValid = false;
1478 SmallVector<Instruction*, 16> AddrModeInsts;
1479 ExtAddrMode AddrMode;
1480 while (!worklist.empty()) {
1481 Value *V = worklist.back();
1482 worklist.pop_back();
1484 // Break use-def graph loops.
1485 if (!Visited.insert(V)) {
1490 // For a PHI node, push all of its incoming values.
1491 if (PHINode *P = dyn_cast<PHINode>(V)) {
1492 for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
1493 worklist.push_back(P->getIncomingValue(i));
1497 // For non-PHIs, determine the addressing mode being computed.
1498 SmallVector<Instruction*, 16> NewAddrModeInsts;
1499 ExtAddrMode NewAddrMode =
1500 AddressingModeMatcher::Match(V, AccessTy, MemoryInst,
1501 NewAddrModeInsts, *TLI);
1503 // This check is broken into two cases with very similar code to avoid using
1504 // getNumUses() as much as possible. Some values have a lot of uses, so
1505 // calling getNumUses() unconditionally caused a significant compile-time
1509 AddrMode = NewAddrMode;
1510 AddrModeInsts = NewAddrModeInsts;
1512 } else if (NewAddrMode == AddrMode) {
1513 if (!IsNumUsesConsensusValid) {
1514 NumUsesConsensus = Consensus->getNumUses();
1515 IsNumUsesConsensusValid = true;
1518 // Ensure that the obtained addressing mode is equivalent to that obtained
1519 // for all other roots of the PHI traversal. Also, when choosing one
1520 // such root as representative, select the one with the most uses in order
1521 // to keep the cost modeling heuristics in AddressingModeMatcher
1523 unsigned NumUses = V->getNumUses();
1524 if (NumUses > NumUsesConsensus) {
1526 NumUsesConsensus = NumUses;
1527 AddrModeInsts = NewAddrModeInsts;
1536 // If the addressing mode couldn't be determined, or if multiple different
1537 // ones were determined, bail out now.
1538 if (!Consensus) return false;
1540 // Check to see if any of the instructions supersumed by this addr mode are
1541 // non-local to I's BB.
1542 bool AnyNonLocal = false;
1543 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
1544 if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
1550 // If all the instructions matched are already in this BB, don't do anything.
1552 DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
1556 // Insert this computation right after this user. Since our caller is
1557 // scanning from the top of the BB to the bottom, reuse of the expr are
1558 // guaranteed to happen later.
1559 IRBuilder<> Builder(MemoryInst);
1561 // Now that we determined the addressing expression we want to use and know
1562 // that we have to sink it into this block. Check to see if we have already
1563 // done this for some other load/store instr in this block. If so, reuse the
1565 Value *&SunkAddr = SunkAddrs[Addr];
1567 DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
1569 if (SunkAddr->getType() != Addr->getType())
1570 SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
1572 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
1575 TLI->getDataLayout()->getIntPtrType(AccessTy->getContext());
1579 // Start with the base register. Do this first so that subsequent address
1580 // matching finds it last, which will prevent it from trying to match it
1581 // as the scaled value in case it happens to be a mul. That would be
1582 // problematic if we've sunk a different mul for the scale, because then
1583 // we'd end up sinking both muls.
1584 if (AddrMode.BaseReg) {
1585 Value *V = AddrMode.BaseReg;
1586 if (V->getType()->isPointerTy())
1587 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
1588 if (V->getType() != IntPtrTy)
1589 V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
1593 // Add the scale value.
1594 if (AddrMode.Scale) {
1595 Value *V = AddrMode.ScaledReg;
1596 if (V->getType() == IntPtrTy) {
1598 } else if (V->getType()->isPointerTy()) {
1599 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
1600 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
1601 cast<IntegerType>(V->getType())->getBitWidth()) {
1602 V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
1604 V = Builder.CreateSExt(V, IntPtrTy, "sunkaddr");
1606 if (AddrMode.Scale != 1)
1607 V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
1610 Result = Builder.CreateAdd(Result, V, "sunkaddr");
1615 // Add in the BaseGV if present.
1616 if (AddrMode.BaseGV) {
1617 Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr");
1619 Result = Builder.CreateAdd(Result, V, "sunkaddr");
1624 // Add in the Base Offset if present.
1625 if (AddrMode.BaseOffs) {
1626 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
1628 Result = Builder.CreateAdd(Result, V, "sunkaddr");
1634 SunkAddr = Constant::getNullValue(Addr->getType());
1636 SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr");
1639 MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
1641 // If we have no uses, recursively delete the value and all dead instructions
1643 if (Repl->use_empty()) {
1644 // This can cause recursive deletion, which can invalidate our iterator.
1645 // Use a WeakVH to hold onto it in case this happens.
1646 WeakVH IterHandle(CurInstIterator);
1647 BasicBlock *BB = CurInstIterator->getParent();
1649 RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo);
1651 if (IterHandle != CurInstIterator) {
1652 // If the iterator instruction was recursively deleted, start over at the
1653 // start of the block.
1654 CurInstIterator = BB->begin();
1657 // This address is now available for reassignment, so erase the table
1658 // entry; we don't want to match some completely different instruction.
1659 SunkAddrs[Addr] = 0;
1666 /// OptimizeInlineAsmInst - If there are any memory operands, use
1667 /// OptimizeMemoryInst to sink their address computing into the block when
1668 /// possible / profitable.
1669 bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) {
1670 bool MadeChange = false;
1672 TargetLowering::AsmOperandInfoVector
1673 TargetConstraints = TLI->ParseConstraints(CS);
1675 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
1676 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
1678 // Compute the constraint code and ConstraintType to use.
1679 TLI->ComputeConstraintToUse(OpInfo, SDValue());
1681 if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
1682 OpInfo.isIndirect) {
1683 Value *OpVal = CS->getArgOperand(ArgNo++);
1684 MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType());
1685 } else if (OpInfo.Type == InlineAsm::isInput)
1692 /// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
1693 /// basic block as the load, unless conditions are unfavorable. This allows
1694 /// SelectionDAG to fold the extend into the load.
1696 bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
1697 // Look for a load being extended.
1698 LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
1699 if (!LI) return false;
1701 // If they're already in the same block, there's nothing to do.
1702 if (LI->getParent() == I->getParent())
1705 // If the load has other users and the truncate is not free, this probably
1706 // isn't worthwhile.
1707 if (!LI->hasOneUse() &&
1708 TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) ||
1709 !TLI->isTypeLegal(TLI->getValueType(I->getType()))) &&
1710 !TLI->isTruncateFree(I->getType(), LI->getType()))
1713 // Check whether the target supports casts folded into loads.
1715 if (isa<ZExtInst>(I))
1716 LType = ISD::ZEXTLOAD;
1718 assert(isa<SExtInst>(I) && "Unexpected ext type!");
1719 LType = ISD::SEXTLOAD;
1721 if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
1724 // Move the extend into the same block as the load, so that SelectionDAG
1726 I->removeFromParent();
1732 bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
1733 BasicBlock *DefBB = I->getParent();
1735 // If the result of a {s|z}ext and its source are both live out, rewrite all
1736 // other uses of the source with result of extension.
1737 Value *Src = I->getOperand(0);
1738 if (Src->hasOneUse())
1741 // Only do this xform if truncating is free.
1742 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
1745 // Only safe to perform the optimization if the source is also defined in
1747 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
1750 bool DefIsLiveOut = false;
1751 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
1753 Instruction *User = cast<Instruction>(*UI);
1755 // Figure out which BB this ext is used in.
1756 BasicBlock *UserBB = User->getParent();
1757 if (UserBB == DefBB) continue;
1758 DefIsLiveOut = true;
1764 // Make sure non of the uses are PHI nodes.
1765 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
1767 Instruction *User = cast<Instruction>(*UI);
1768 BasicBlock *UserBB = User->getParent();
1769 if (UserBB == DefBB) continue;
1770 // Be conservative. We don't want this xform to end up introducing
1771 // reloads just before load / store instructions.
1772 if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
1776 // InsertedTruncs - Only insert one trunc in each block once.
1777 DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
1779 bool MadeChange = false;
1780 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
1782 Use &TheUse = UI.getUse();
1783 Instruction *User = cast<Instruction>(*UI);
1785 // Figure out which BB this ext is used in.
1786 BasicBlock *UserBB = User->getParent();
1787 if (UserBB == DefBB) continue;
1789 // Both src and def are live in this block. Rewrite the use.
1790 Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
1792 if (!InsertedTrunc) {
1793 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
1794 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
1797 // Replace a use of the {s|z}ext source with a use of the result.
1798 TheUse = InsertedTrunc;
1806 /// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be
1807 /// turned into an explicit branch.
1808 static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
1809 // FIXME: This should use the same heuristics as IfConversion to determine
1810 // whether a select is better represented as a branch. This requires that
1811 // branch probability metadata is preserved for the select, which is not the
1814 CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
1816 // If the branch is predicted right, an out of order CPU can avoid blocking on
1817 // the compare. Emit cmovs on compares with a memory operand as branches to
1818 // avoid stalls on the load from memory. If the compare has more than one use
1819 // there's probably another cmov or setcc around so it's not worth emitting a
1824 Value *CmpOp0 = Cmp->getOperand(0);
1825 Value *CmpOp1 = Cmp->getOperand(1);
1827 // We check that the memory operand has one use to avoid uses of the loaded
1828 // value directly after the compare, making branches unprofitable.
1829 return Cmp->hasOneUse() &&
1830 ((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) ||
1831 (isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse()));
1835 /// If we have a SelectInst that will likely profit from branch prediction,
1836 /// turn it into a branch.
1837 bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) {
1838 bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
1840 // Can we convert the 'select' to CF ?
1841 if (DisableSelectToBranch || OptSize || !TLI || VectorCond)
1844 TargetLowering::SelectSupportKind SelectKind;
1846 SelectKind = TargetLowering::VectorMaskSelect;
1847 else if (SI->getType()->isVectorTy())
1848 SelectKind = TargetLowering::ScalarCondVectorVal;
1850 SelectKind = TargetLowering::ScalarValSelect;
1852 // Do we have efficient codegen support for this kind of 'selects' ?
1853 if (TLI->isSelectSupported(SelectKind)) {
1854 // We have efficient codegen support for the select instruction.
1855 // Check if it is profitable to keep this 'select'.
1856 if (!TLI->isPredictableSelectExpensive() ||
1857 !isFormingBranchFromSelectProfitable(SI))
1863 // First, we split the block containing the select into 2 blocks.
1864 BasicBlock *StartBlock = SI->getParent();
1865 BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI));
1866 BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
1868 // Create a new block serving as the landing pad for the branch.
1869 BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid",
1870 NextBlock->getParent(), NextBlock);
1872 // Move the unconditional branch from the block with the select in it into our
1873 // landing pad block.
1874 StartBlock->getTerminator()->eraseFromParent();
1875 BranchInst::Create(NextBlock, SmallBlock);
1877 // Insert the real conditional branch based on the original condition.
1878 BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI);
1880 // The select itself is replaced with a PHI Node.
1881 PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin());
1883 PN->addIncoming(SI->getTrueValue(), StartBlock);
1884 PN->addIncoming(SI->getFalseValue(), SmallBlock);
1885 SI->replaceAllUsesWith(PN);
1886 SI->eraseFromParent();
1888 // Instruct OptimizeBlock to skip to the next block.
1889 CurInstIterator = StartBlock->end();
1890 ++NumSelectsExpanded;
1894 bool CodeGenPrepare::OptimizeInst(Instruction *I) {
1895 if (PHINode *P = dyn_cast<PHINode>(I)) {
1896 // It is possible for very late stage optimizations (such as SimplifyCFG)
1897 // to introduce PHI nodes too late to be cleaned up. If we detect such a
1898 // trivial PHI, go ahead and zap it here.
1899 if (Value *V = SimplifyInstruction(P)) {
1900 P->replaceAllUsesWith(V);
1901 P->eraseFromParent();
1908 if (CastInst *CI = dyn_cast<CastInst>(I)) {
1909 // If the source of the cast is a constant, then this should have
1910 // already been constant folded. The only reason NOT to constant fold
1911 // it is if something (e.g. LSR) was careful to place the constant
1912 // evaluation in a block other than then one that uses it (e.g. to hoist
1913 // the address of globals out of a loop). If this is the case, we don't
1914 // want to forward-subst the cast.
1915 if (isa<Constant>(CI->getOperand(0)))
1918 if (TLI && OptimizeNoopCopyExpression(CI, *TLI))
1921 if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
1922 bool MadeChange = MoveExtToFormExtLoad(I);
1923 return MadeChange | OptimizeExtUses(I);
1928 if (CmpInst *CI = dyn_cast<CmpInst>(I))
1929 return OptimizeCmpExpression(CI);
1931 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
1933 return OptimizeMemoryInst(I, I->getOperand(0), LI->getType());
1937 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
1939 return OptimizeMemoryInst(I, SI->getOperand(1),
1940 SI->getOperand(0)->getType());
1944 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
1945 if (GEPI->hasAllZeroIndices()) {
1946 /// The GEP operand must be a pointer, so must its result -> BitCast
1947 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
1948 GEPI->getName(), GEPI);
1949 GEPI->replaceAllUsesWith(NC);
1950 GEPI->eraseFromParent();
1958 if (CallInst *CI = dyn_cast<CallInst>(I))
1959 return OptimizeCallInst(CI);
1961 if (SelectInst *SI = dyn_cast<SelectInst>(I))
1962 return OptimizeSelectInst(SI);
1967 // In this pass we look for GEP and cast instructions that are used
1968 // across basic blocks and rewrite them to improve basic-block-at-a-time
1970 bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
1972 bool MadeChange = false;
1974 CurInstIterator = BB.begin();
1975 while (CurInstIterator != BB.end())
1976 MadeChange |= OptimizeInst(CurInstIterator++);
1978 MadeChange |= DupRetToEnableTailCallOpts(&BB);
1983 // llvm.dbg.value is far away from the value then iSel may not be able
1984 // handle it properly. iSel will drop llvm.dbg.value if it can not
1985 // find a node corresponding to the value.
1986 bool CodeGenPrepare::PlaceDbgValues(Function &F) {
1987 bool MadeChange = false;
1988 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
1989 Instruction *PrevNonDbgInst = NULL;
1990 for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
1991 Instruction *Insn = BI; ++BI;
1992 DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn);
1994 PrevNonDbgInst = Insn;
1998 Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue());
1999 if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) {
2000 DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
2001 DVI->removeFromParent();
2002 if (isa<PHINode>(VI))
2003 DVI->insertBefore(VI->getParent()->getFirstInsertionPt());
2005 DVI->insertAfter(VI);