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/Constants.h"
19 #include "llvm/DerivedTypes.h"
20 #include "llvm/Function.h"
21 #include "llvm/InlineAsm.h"
22 #include "llvm/Instructions.h"
23 #include "llvm/IntrinsicInst.h"
24 #include "llvm/Pass.h"
25 #include "llvm/Analysis/ProfileInfo.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Target/TargetLowering.h"
28 #include "llvm/Transforms/Utils/AddrModeMatcher.h"
29 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
30 #include "llvm/Transforms/Utils/Local.h"
31 #include "llvm/ADT/DenseMap.h"
32 #include "llvm/ADT/SmallSet.h"
33 #include "llvm/Assembly/Writer.h"
34 #include "llvm/Support/CallSite.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/GetElementPtrTypeIterator.h"
38 #include "llvm/Support/PatternMatch.h"
39 #include "llvm/Support/raw_ostream.h"
41 using namespace llvm::PatternMatch;
43 static cl::opt<bool> FactorCommonPreds("split-critical-paths-tweak",
44 cl::init(false), cl::Hidden);
47 class CodeGenPrepare : public FunctionPass {
48 /// TLI - Keep a pointer of a TargetLowering to consult for determining
49 /// transformation profitability.
50 const TargetLowering *TLI;
53 /// BackEdges - Keep a set of all the loop back edges.
55 SmallSet<std::pair<const BasicBlock*, const BasicBlock*>, 8> BackEdges;
57 static char ID; // Pass identification, replacement for typeid
58 explicit CodeGenPrepare(const TargetLowering *tli = 0)
59 : FunctionPass(&ID), TLI(tli) {}
60 bool runOnFunction(Function &F);
62 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
63 AU.addPreserved<ProfileInfo>();
67 bool EliminateMostlyEmptyBlocks(Function &F);
68 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
69 void EliminateMostlyEmptyBlock(BasicBlock *BB);
70 bool OptimizeBlock(BasicBlock &BB);
71 bool OptimizeMemoryInst(Instruction *I, Value *Addr, const Type *AccessTy,
72 DenseMap<Value*,Value*> &SunkAddrs);
73 bool OptimizeInlineAsmInst(Instruction *I, CallSite CS,
74 DenseMap<Value*,Value*> &SunkAddrs);
75 bool MoveExtToFormExtLoad(Instruction *I);
76 bool OptimizeExtUses(Instruction *I);
77 void findLoopBackEdges(const Function &F);
81 char CodeGenPrepare::ID = 0;
82 static RegisterPass<CodeGenPrepare> X("codegenprepare",
83 "Optimize for code generation");
85 FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
86 return new CodeGenPrepare(TLI);
89 /// findLoopBackEdges - Do a DFS walk to find loop back edges.
91 void CodeGenPrepare::findLoopBackEdges(const Function &F) {
92 SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges;
93 FindFunctionBackedges(F, Edges);
95 BackEdges.insert(Edges.begin(), Edges.end());
99 bool CodeGenPrepare::runOnFunction(Function &F) {
100 bool EverMadeChange = false;
102 PFI = getAnalysisIfAvailable<ProfileInfo>();
103 // First pass, eliminate blocks that contain only PHI nodes and an
104 // unconditional branch.
105 EverMadeChange |= EliminateMostlyEmptyBlocks(F);
107 // Now find loop back edges.
108 findLoopBackEdges(F);
110 bool MadeChange = true;
113 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
114 MadeChange |= OptimizeBlock(*BB);
115 EverMadeChange |= MadeChange;
117 return EverMadeChange;
120 /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
121 /// debug info directives, and an unconditional branch. Passes before isel
122 /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
123 /// isel. Start by eliminating these blocks so we can split them the way we
125 bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
126 bool MadeChange = false;
127 // Note that this intentionally skips the entry block.
128 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
129 BasicBlock *BB = I++;
131 // If this block doesn't end with an uncond branch, ignore it.
132 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
133 if (!BI || !BI->isUnconditional())
136 // If the instruction before the branch (skipping debug info) isn't a phi
137 // node, then other stuff is happening here.
138 BasicBlock::iterator BBI = BI;
139 if (BBI != BB->begin()) {
141 while (isa<DbgInfoIntrinsic>(BBI)) {
142 if (BBI == BB->begin())
146 if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
150 // Do not break infinite loops.
151 BasicBlock *DestBB = BI->getSuccessor(0);
155 if (!CanMergeBlocks(BB, DestBB))
158 EliminateMostlyEmptyBlock(BB);
164 /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
165 /// single uncond branch between them, and BB contains no other non-phi
167 bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
168 const BasicBlock *DestBB) const {
169 // We only want to eliminate blocks whose phi nodes are used by phi nodes in
170 // the successor. If there are more complex condition (e.g. preheaders),
171 // don't mess around with them.
172 BasicBlock::const_iterator BBI = BB->begin();
173 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
174 for (Value::use_const_iterator UI = PN->use_begin(), E = PN->use_end();
176 const Instruction *User = cast<Instruction>(*UI);
177 if (User->getParent() != DestBB || !isa<PHINode>(User))
179 // If User is inside DestBB block and it is a PHINode then check
180 // incoming value. If incoming value is not from BB then this is
181 // a complex condition (e.g. preheaders) we want to avoid here.
182 if (User->getParent() == DestBB) {
183 if (const PHINode *UPN = dyn_cast<PHINode>(User))
184 for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
185 Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
186 if (Insn && Insn->getParent() == BB &&
187 Insn->getParent() != UPN->getIncomingBlock(I))
194 // If BB and DestBB contain any common predecessors, then the phi nodes in BB
195 // and DestBB may have conflicting incoming values for the block. If so, we
196 // can't merge the block.
197 const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
198 if (!DestBBPN) return true; // no conflict.
200 // Collect the preds of BB.
201 SmallPtrSet<const BasicBlock*, 16> BBPreds;
202 if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
203 // It is faster to get preds from a PHI than with pred_iterator.
204 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
205 BBPreds.insert(BBPN->getIncomingBlock(i));
207 BBPreds.insert(pred_begin(BB), pred_end(BB));
210 // Walk the preds of DestBB.
211 for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
212 BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
213 if (BBPreds.count(Pred)) { // Common predecessor?
214 BBI = DestBB->begin();
215 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
216 const Value *V1 = PN->getIncomingValueForBlock(Pred);
217 const Value *V2 = PN->getIncomingValueForBlock(BB);
219 // If V2 is a phi node in BB, look up what the mapped value will be.
220 if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
221 if (V2PN->getParent() == BB)
222 V2 = V2PN->getIncomingValueForBlock(Pred);
224 // If there is a conflict, bail out.
225 if (V1 != V2) return false;
234 /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
235 /// an unconditional branch in it.
236 void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
237 BranchInst *BI = cast<BranchInst>(BB->getTerminator());
238 BasicBlock *DestBB = BI->getSuccessor(0);
240 DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
242 // If the destination block has a single pred, then this is a trivial edge,
244 if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
245 if (SinglePred != DestBB) {
246 // Remember if SinglePred was the entry block of the function. If so, we
247 // will need to move BB back to the entry position.
248 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
249 MergeBasicBlockIntoOnlyPred(DestBB, this);
251 if (isEntry && BB != &BB->getParent()->getEntryBlock())
252 BB->moveBefore(&BB->getParent()->getEntryBlock());
254 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
259 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
260 // to handle the new incoming edges it is about to have.
262 for (BasicBlock::iterator BBI = DestBB->begin();
263 (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
264 // Remove the incoming value for BB, and remember it.
265 Value *InVal = PN->removeIncomingValue(BB, false);
267 // Two options: either the InVal is a phi node defined in BB or it is some
268 // value that dominates BB.
269 PHINode *InValPhi = dyn_cast<PHINode>(InVal);
270 if (InValPhi && InValPhi->getParent() == BB) {
271 // Add all of the input values of the input PHI as inputs of this phi.
272 for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
273 PN->addIncoming(InValPhi->getIncomingValue(i),
274 InValPhi->getIncomingBlock(i));
276 // Otherwise, add one instance of the dominating value for each edge that
277 // we will be adding.
278 if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
279 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
280 PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
282 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
283 PN->addIncoming(InVal, *PI);
288 // The PHIs are now updated, change everything that refers to BB to use
289 // DestBB and remove BB.
290 BB->replaceAllUsesWith(DestBB);
292 PFI->replaceAllUses(BB, DestBB);
293 PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
295 BB->eraseFromParent();
297 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
301 /// SplitEdgeNicely - Split the critical edge from TI to its specified
302 /// successor if it will improve codegen. We only do this if the successor has
303 /// phi nodes (otherwise critical edges are ok). If there is already another
304 /// predecessor of the succ that is empty (and thus has no phi nodes), use it
305 /// instead of introducing a new block.
306 static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum,
307 SmallSet<std::pair<const BasicBlock*,
308 const BasicBlock*>, 8> &BackEdges,
310 BasicBlock *TIBB = TI->getParent();
311 BasicBlock *Dest = TI->getSuccessor(SuccNum);
312 assert(isa<PHINode>(Dest->begin()) &&
313 "This should only be called if Dest has a PHI!");
315 // Do not split edges to EH landing pads.
316 if (InvokeInst *Invoke = dyn_cast<InvokeInst>(TI)) {
317 if (Invoke->getSuccessor(1) == Dest)
322 // As a hack, never split backedges of loops. Even though the copy for any
323 // PHIs inserted on the backedge would be dead for exits from the loop, we
324 // assume that the cost of *splitting* the backedge would be too high.
325 if (BackEdges.count(std::make_pair(TIBB, Dest)))
328 if (!FactorCommonPreds) {
329 /// TIPHIValues - This array is lazily computed to determine the values of
330 /// PHIs in Dest that TI would provide.
331 SmallVector<Value*, 32> TIPHIValues;
333 // Check to see if Dest has any blocks that can be used as a split edge for
335 for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
336 BasicBlock *Pred = *PI;
337 // To be usable, the pred has to end with an uncond branch to the dest.
338 BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
339 if (!PredBr || !PredBr->isUnconditional())
341 // Must be empty other than the branch and debug info.
342 BasicBlock::iterator I = Pred->begin();
343 while (isa<DbgInfoIntrinsic>(I))
345 if (dyn_cast<Instruction>(I) != PredBr)
347 // Cannot be the entry block; its label does not get emitted.
348 if (Pred == &(Dest->getParent()->getEntryBlock()))
351 // Finally, since we know that Dest has phi nodes in it, we have to make
352 // sure that jumping to Pred will have the same effect as going to Dest in
353 // terms of PHI values.
356 bool FoundMatch = true;
357 for (BasicBlock::iterator I = Dest->begin();
358 (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
359 if (PHINo == TIPHIValues.size())
360 TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
362 // If the PHI entry doesn't work, we can't use this pred.
363 if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
369 // If we found a workable predecessor, change TI to branch to Succ.
371 ProfileInfo *PFI = P->getAnalysisIfAvailable<ProfileInfo>();
373 PFI->splitEdge(TIBB, Dest, Pred);
374 Dest->removePredecessor(TIBB);
375 TI->setSuccessor(SuccNum, Pred);
380 SplitCriticalEdge(TI, SuccNum, P, true);
385 SmallVector<Value*, 8> TIPHIValues;
386 for (BasicBlock::iterator I = Dest->begin();
387 (PN = dyn_cast<PHINode>(I)); ++I)
388 TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
390 SmallVector<BasicBlock*, 8> IdenticalPreds;
391 for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
392 BasicBlock *Pred = *PI;
393 if (BackEdges.count(std::make_pair(Pred, Dest)))
396 IdenticalPreds.push_back(Pred);
398 bool Identical = true;
400 for (BasicBlock::iterator I = Dest->begin();
401 (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo)
402 if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
407 IdenticalPreds.push_back(Pred);
411 assert(!IdenticalPreds.empty());
412 SplitBlockPredecessors(Dest, &IdenticalPreds[0], IdenticalPreds.size(),
417 /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
418 /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
419 /// sink it into user blocks to reduce the number of virtual
420 /// registers that must be created and coalesced.
422 /// Return true if any changes are made.
424 static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
425 // If this is a noop copy,
426 EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
427 EVT DstVT = TLI.getValueType(CI->getType());
429 // This is an fp<->int conversion?
430 if (SrcVT.isInteger() != DstVT.isInteger())
433 // If this is an extension, it will be a zero or sign extension, which
435 if (SrcVT.bitsLT(DstVT)) return false;
437 // If these values will be promoted, find out what they will be promoted
438 // to. This helps us consider truncates on PPC as noop copies when they
440 if (TLI.getTypeAction(CI->getContext(), SrcVT) == TargetLowering::Promote)
441 SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
442 if (TLI.getTypeAction(CI->getContext(), DstVT) == TargetLowering::Promote)
443 DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
445 // If, after promotion, these are the same types, this is a noop copy.
449 BasicBlock *DefBB = CI->getParent();
451 /// InsertedCasts - Only insert a cast in each block once.
452 DenseMap<BasicBlock*, CastInst*> InsertedCasts;
454 bool MadeChange = false;
455 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
457 Use &TheUse = UI.getUse();
458 Instruction *User = cast<Instruction>(*UI);
460 // Figure out which BB this cast is used in. For PHI's this is the
461 // appropriate predecessor block.
462 BasicBlock *UserBB = User->getParent();
463 if (PHINode *PN = dyn_cast<PHINode>(User)) {
464 UserBB = PN->getIncomingBlock(UI);
467 // Preincrement use iterator so we don't invalidate it.
470 // If this user is in the same block as the cast, don't change the cast.
471 if (UserBB == DefBB) continue;
473 // If we have already inserted a cast into this block, use it.
474 CastInst *&InsertedCast = InsertedCasts[UserBB];
477 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
480 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
485 // Replace a use of the cast with a use of the new cast.
486 TheUse = InsertedCast;
489 // If we removed all uses, nuke the cast.
490 if (CI->use_empty()) {
491 CI->eraseFromParent();
498 /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
499 /// the number of virtual registers that must be created and coalesced. This is
500 /// a clear win except on targets with multiple condition code registers
501 /// (PowerPC), where it might lose; some adjustment may be wanted there.
503 /// Return true if any changes are made.
504 static bool OptimizeCmpExpression(CmpInst *CI) {
505 BasicBlock *DefBB = CI->getParent();
507 /// InsertedCmp - Only insert a cmp in each block once.
508 DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
510 bool MadeChange = false;
511 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
513 Use &TheUse = UI.getUse();
514 Instruction *User = cast<Instruction>(*UI);
516 // Preincrement use iterator so we don't invalidate it.
519 // Don't bother for PHI nodes.
520 if (isa<PHINode>(User))
523 // Figure out which BB this cmp is used in.
524 BasicBlock *UserBB = User->getParent();
526 // If this user is in the same block as the cmp, don't change the cmp.
527 if (UserBB == DefBB) continue;
529 // If we have already inserted a cmp into this block, use it.
530 CmpInst *&InsertedCmp = InsertedCmps[UserBB];
533 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
536 CmpInst::Create(CI->getOpcode(),
537 CI->getPredicate(), CI->getOperand(0),
538 CI->getOperand(1), "", InsertPt);
542 // Replace a use of the cmp with a use of the new cmp.
543 TheUse = InsertedCmp;
546 // If we removed all uses, nuke the cmp.
548 CI->eraseFromParent();
553 //===----------------------------------------------------------------------===//
554 // Memory Optimization
555 //===----------------------------------------------------------------------===//
557 /// IsNonLocalValue - Return true if the specified values are defined in a
558 /// different basic block than BB.
559 static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
560 if (Instruction *I = dyn_cast<Instruction>(V))
561 return I->getParent() != BB;
565 /// OptimizeMemoryInst - Load and Store Instructions often have
566 /// addressing modes that can do significant amounts of computation. As such,
567 /// instruction selection will try to get the load or store to do as much
568 /// computation as possible for the program. The problem is that isel can only
569 /// see within a single block. As such, we sink as much legal addressing mode
570 /// stuff into the block as possible.
572 /// This method is used to optimize both load/store and inline asms with memory
574 bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
575 const Type *AccessTy,
576 DenseMap<Value*,Value*> &SunkAddrs) {
577 // Figure out what addressing mode will be built up for this operation.
578 SmallVector<Instruction*, 16> AddrModeInsts;
579 ExtAddrMode AddrMode = AddressingModeMatcher::Match(Addr, AccessTy,MemoryInst,
580 AddrModeInsts, *TLI);
582 // Check to see if any of the instructions supersumed by this addr mode are
583 // non-local to I's BB.
584 bool AnyNonLocal = false;
585 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
586 if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
592 // If all the instructions matched are already in this BB, don't do anything.
594 DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
598 // Insert this computation right after this user. Since our caller is
599 // scanning from the top of the BB to the bottom, reuse of the expr are
600 // guaranteed to happen later.
601 BasicBlock::iterator InsertPt = MemoryInst;
603 // Now that we determined the addressing expression we want to use and know
604 // that we have to sink it into this block. Check to see if we have already
605 // done this for some other load/store instr in this block. If so, reuse the
607 Value *&SunkAddr = SunkAddrs[Addr];
609 DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
611 if (SunkAddr->getType() != Addr->getType())
612 SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt);
614 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
616 const Type *IntPtrTy =
617 TLI->getTargetData()->getIntPtrType(AccessTy->getContext());
621 // Start with the base register. Do this first so that subsequent address
622 // matching finds it last, which will prevent it from trying to match it
623 // as the scaled value in case it happens to be a mul. That would be
624 // problematic if we've sunk a different mul for the scale, because then
625 // we'd end up sinking both muls.
626 if (AddrMode.BaseReg) {
627 Value *V = AddrMode.BaseReg;
628 if (isa<PointerType>(V->getType()))
629 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
630 if (V->getType() != IntPtrTy)
631 V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true,
632 "sunkaddr", InsertPt);
636 // Add the scale value.
637 if (AddrMode.Scale) {
638 Value *V = AddrMode.ScaledReg;
639 if (V->getType() == IntPtrTy) {
641 } else if (isa<PointerType>(V->getType())) {
642 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
643 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
644 cast<IntegerType>(V->getType())->getBitWidth()) {
645 V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt);
647 V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt);
649 if (AddrMode.Scale != 1)
650 V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
652 "sunkaddr", InsertPt);
654 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
659 // Add in the BaseGV if present.
660 if (AddrMode.BaseGV) {
661 Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr",
664 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
669 // Add in the Base Offset if present.
670 if (AddrMode.BaseOffs) {
671 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
673 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
679 SunkAddr = Constant::getNullValue(Addr->getType());
681 SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt);
684 MemoryInst->replaceUsesOfWith(Addr, SunkAddr);
686 if (Addr->use_empty())
687 RecursivelyDeleteTriviallyDeadInstructions(Addr);
691 /// OptimizeInlineAsmInst - If there are any memory operands, use
692 /// OptimizeMemoryInst to sink their address computing into the block when
693 /// possible / profitable.
694 bool CodeGenPrepare::OptimizeInlineAsmInst(Instruction *I, CallSite CS,
695 DenseMap<Value*,Value*> &SunkAddrs) {
696 bool MadeChange = false;
697 InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue());
699 // Do a prepass over the constraints, canonicalizing them, and building up the
700 // ConstraintOperands list.
701 std::vector<InlineAsm::ConstraintInfo>
702 ConstraintInfos = IA->ParseConstraints();
704 /// ConstraintOperands - Information about all of the constraints.
705 std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands;
706 unsigned ArgNo = 0; // ArgNo - The argument of the CallInst.
707 for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) {
709 push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i]));
710 TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back();
712 // Compute the value type for each operand.
713 switch (OpInfo.Type) {
714 case InlineAsm::isOutput:
715 if (OpInfo.isIndirect)
716 OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
718 case InlineAsm::isInput:
719 OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
721 case InlineAsm::isClobber:
726 // Compute the constraint code and ConstraintType to use.
727 TLI->ComputeConstraintToUse(OpInfo, SDValue(),
728 OpInfo.ConstraintType == TargetLowering::C_Memory);
730 if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
732 Value *OpVal = OpInfo.CallOperandVal;
733 MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs);
740 /// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
741 /// basic block as the load, unless conditions are unfavorable. This allows
742 /// SelectionDAG to fold the extend into the load.
744 bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
745 // Look for a load being extended.
746 LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
747 if (!LI) return false;
749 // If they're already in the same block, there's nothing to do.
750 if (LI->getParent() == I->getParent())
753 // If the load has other users and the truncate is not free, this probably
755 if (!LI->hasOneUse() &&
756 TLI && !TLI->isTruncateFree(I->getType(), LI->getType()))
759 // Check whether the target supports casts folded into loads.
761 if (isa<ZExtInst>(I))
762 LType = ISD::ZEXTLOAD;
764 assert(isa<SExtInst>(I) && "Unexpected ext type!");
765 LType = ISD::SEXTLOAD;
767 if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
770 // Move the extend into the same block as the load, so that SelectionDAG
772 I->removeFromParent();
777 bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
778 BasicBlock *DefBB = I->getParent();
780 // If both result of the {s|z}xt and its source are live out, rewrite all
781 // other uses of the source with result of extension.
782 Value *Src = I->getOperand(0);
783 if (Src->hasOneUse())
786 // Only do this xform if truncating is free.
787 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
790 // Only safe to perform the optimization if the source is also defined in
792 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
795 bool DefIsLiveOut = false;
796 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
798 Instruction *User = cast<Instruction>(*UI);
800 // Figure out which BB this ext is used in.
801 BasicBlock *UserBB = User->getParent();
802 if (UserBB == DefBB) continue;
809 // Make sure non of the uses are PHI nodes.
810 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
812 Instruction *User = cast<Instruction>(*UI);
813 BasicBlock *UserBB = User->getParent();
814 if (UserBB == DefBB) continue;
815 // Be conservative. We don't want this xform to end up introducing
816 // reloads just before load / store instructions.
817 if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
821 // InsertedTruncs - Only insert one trunc in each block once.
822 DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
824 bool MadeChange = false;
825 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
827 Use &TheUse = UI.getUse();
828 Instruction *User = cast<Instruction>(*UI);
830 // Figure out which BB this ext is used in.
831 BasicBlock *UserBB = User->getParent();
832 if (UserBB == DefBB) continue;
834 // Both src and def are live in this block. Rewrite the use.
835 Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
837 if (!InsertedTrunc) {
838 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
840 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
843 // Replace a use of the {s|z}ext source with a use of the result.
844 TheUse = InsertedTrunc;
852 // In this pass we look for GEP and cast instructions that are used
853 // across basic blocks and rewrite them to improve basic-block-at-a-time
855 bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
856 bool MadeChange = false;
858 // Split all critical edges where the dest block has a PHI.
859 TerminatorInst *BBTI = BB.getTerminator();
860 if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
861 for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
862 BasicBlock *SuccBB = BBTI->getSuccessor(i);
863 if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
864 SplitEdgeNicely(BBTI, i, BackEdges, this);
868 // Keep track of non-local addresses that have been sunk into this block.
869 // This allows us to avoid inserting duplicate code for blocks with multiple
870 // load/stores of the same address.
871 DenseMap<Value*, Value*> SunkAddrs;
873 for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) {
874 Instruction *I = BBI++;
876 if (CastInst *CI = dyn_cast<CastInst>(I)) {
877 // If the source of the cast is a constant, then this should have
878 // already been constant folded. The only reason NOT to constant fold
879 // it is if something (e.g. LSR) was careful to place the constant
880 // evaluation in a block other than then one that uses it (e.g. to hoist
881 // the address of globals out of a loop). If this is the case, we don't
882 // want to forward-subst the cast.
883 if (isa<Constant>(CI->getOperand(0)))
888 Change = OptimizeNoopCopyExpression(CI, *TLI);
889 MadeChange |= Change;
892 if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I))) {
893 MadeChange |= MoveExtToFormExtLoad(I);
894 MadeChange |= OptimizeExtUses(I);
896 } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
897 MadeChange |= OptimizeCmpExpression(CI);
898 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
900 MadeChange |= OptimizeMemoryInst(I, I->getOperand(0), LI->getType(),
902 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
904 MadeChange |= OptimizeMemoryInst(I, SI->getOperand(1),
905 SI->getOperand(0)->getType(),
907 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
908 if (GEPI->hasAllZeroIndices()) {
909 /// The GEP operand must be a pointer, so must its result -> BitCast
910 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
911 GEPI->getName(), GEPI);
912 GEPI->replaceAllUsesWith(NC);
913 GEPI->eraseFromParent();
917 } else if (CallInst *CI = dyn_cast<CallInst>(I)) {
918 // If we found an inline asm expession, and if the target knows how to
919 // lower it to normal LLVM code, do so now.
920 if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
921 if (TLI->ExpandInlineAsm(CI)) {
923 // Avoid processing instructions out of order, which could cause
924 // reuse before a value is defined.
927 // Sink address computing for memory operands into the block.
928 MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs);