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/Pass.h"
24 #include "llvm/Target/TargetAsmInfo.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Target/TargetLowering.h"
27 #include "llvm/Target/TargetMachine.h"
28 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
29 #include "llvm/Transforms/Utils/Local.h"
30 #include "llvm/ADT/DenseMap.h"
31 #include "llvm/ADT/SmallSet.h"
32 #include "llvm/Support/CallSite.h"
33 #include "llvm/Support/Compiler.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 class VISIBILITY_HIDDEN CodeGenPrepare : public FunctionPass {
40 /// TLI - Keep a pointer of a TargetLowering to consult for determining
41 /// transformation profitability.
42 const TargetLowering *TLI;
44 static char ID; // Pass identification, replacement for typeid
45 explicit CodeGenPrepare(const TargetLowering *tli = 0)
46 : FunctionPass(&ID), TLI(tli) {}
47 bool runOnFunction(Function &F);
50 bool EliminateMostlyEmptyBlocks(Function &F);
51 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
52 void EliminateMostlyEmptyBlock(BasicBlock *BB);
53 bool OptimizeBlock(BasicBlock &BB);
54 bool OptimizeLoadStoreInst(Instruction *I, Value *Addr,
56 DenseMap<Value*,Value*> &SunkAddrs);
57 bool OptimizeInlineAsmInst(Instruction *I, CallSite CS,
58 DenseMap<Value*,Value*> &SunkAddrs);
59 bool OptimizeExtUses(Instruction *I);
63 char CodeGenPrepare::ID = 0;
64 static RegisterPass<CodeGenPrepare> X("codegenprepare",
65 "Optimize for code generation");
67 FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
68 return new CodeGenPrepare(TLI);
72 bool CodeGenPrepare::runOnFunction(Function &F) {
73 bool EverMadeChange = false;
75 // First pass, eliminate blocks that contain only PHI nodes and an
76 // unconditional branch.
77 EverMadeChange |= EliminateMostlyEmptyBlocks(F);
79 bool MadeChange = true;
82 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
83 MadeChange |= OptimizeBlock(*BB);
84 EverMadeChange |= MadeChange;
86 return EverMadeChange;
89 /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes
90 /// and an unconditional branch. Passes before isel (e.g. LSR/loopsimplify)
91 /// often split edges in ways that are non-optimal for isel. Start by
92 /// eliminating these blocks so we can split them the way we want them.
93 bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
94 bool MadeChange = false;
95 // Note that this intentionally skips the entry block.
96 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
99 // If this block doesn't end with an uncond branch, ignore it.
100 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
101 if (!BI || !BI->isUnconditional())
104 // If the instruction before the branch isn't a phi node, then other stuff
105 // is happening here.
106 BasicBlock::iterator BBI = BI;
107 if (BBI != BB->begin()) {
109 if (!isa<PHINode>(BBI)) continue;
112 // Do not break infinite loops.
113 BasicBlock *DestBB = BI->getSuccessor(0);
117 if (!CanMergeBlocks(BB, DestBB))
120 EliminateMostlyEmptyBlock(BB);
126 /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
127 /// single uncond branch between them, and BB contains no other non-phi
129 bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
130 const BasicBlock *DestBB) const {
131 // We only want to eliminate blocks whose phi nodes are used by phi nodes in
132 // the successor. If there are more complex condition (e.g. preheaders),
133 // don't mess around with them.
134 BasicBlock::const_iterator BBI = BB->begin();
135 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
136 for (Value::use_const_iterator UI = PN->use_begin(), E = PN->use_end();
138 const Instruction *User = cast<Instruction>(*UI);
139 if (User->getParent() != DestBB || !isa<PHINode>(User))
141 // If User is inside DestBB block and it is a PHINode then check
142 // incoming value. If incoming value is not from BB then this is
143 // a complex condition (e.g. preheaders) we want to avoid here.
144 if (User->getParent() == DestBB) {
145 if (const PHINode *UPN = dyn_cast<PHINode>(User))
146 for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
147 Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
148 if (Insn && Insn->getParent() == BB &&
149 Insn->getParent() != UPN->getIncomingBlock(I))
156 // If BB and DestBB contain any common predecessors, then the phi nodes in BB
157 // and DestBB may have conflicting incoming values for the block. If so, we
158 // can't merge the block.
159 const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
160 if (!DestBBPN) return true; // no conflict.
162 // Collect the preds of BB.
163 SmallPtrSet<const BasicBlock*, 16> BBPreds;
164 if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
165 // It is faster to get preds from a PHI than with pred_iterator.
166 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
167 BBPreds.insert(BBPN->getIncomingBlock(i));
169 BBPreds.insert(pred_begin(BB), pred_end(BB));
172 // Walk the preds of DestBB.
173 for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
174 BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
175 if (BBPreds.count(Pred)) { // Common predecessor?
176 BBI = DestBB->begin();
177 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
178 const Value *V1 = PN->getIncomingValueForBlock(Pred);
179 const Value *V2 = PN->getIncomingValueForBlock(BB);
181 // If V2 is a phi node in BB, look up what the mapped value will be.
182 if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
183 if (V2PN->getParent() == BB)
184 V2 = V2PN->getIncomingValueForBlock(Pred);
186 // If there is a conflict, bail out.
187 if (V1 != V2) return false;
196 /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
197 /// an unconditional branch in it.
198 void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
199 BranchInst *BI = cast<BranchInst>(BB->getTerminator());
200 BasicBlock *DestBB = BI->getSuccessor(0);
202 DOUT << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB;
204 // If the destination block has a single pred, then this is a trivial edge,
206 if (DestBB->getSinglePredecessor()) {
207 // If DestBB has single-entry PHI nodes, fold them.
208 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
209 PN->replaceAllUsesWith(PN->getIncomingValue(0));
210 PN->eraseFromParent();
213 // Splice all the PHI nodes from BB over to DestBB.
214 DestBB->getInstList().splice(DestBB->begin(), BB->getInstList(),
217 // Anything that branched to BB now branches to DestBB.
218 BB->replaceAllUsesWith(DestBB);
221 BB->eraseFromParent();
223 DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
227 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
228 // to handle the new incoming edges it is about to have.
230 for (BasicBlock::iterator BBI = DestBB->begin();
231 (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
232 // Remove the incoming value for BB, and remember it.
233 Value *InVal = PN->removeIncomingValue(BB, false);
235 // Two options: either the InVal is a phi node defined in BB or it is some
236 // value that dominates BB.
237 PHINode *InValPhi = dyn_cast<PHINode>(InVal);
238 if (InValPhi && InValPhi->getParent() == BB) {
239 // Add all of the input values of the input PHI as inputs of this phi.
240 for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
241 PN->addIncoming(InValPhi->getIncomingValue(i),
242 InValPhi->getIncomingBlock(i));
244 // Otherwise, add one instance of the dominating value for each edge that
245 // we will be adding.
246 if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
247 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
248 PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
250 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
251 PN->addIncoming(InVal, *PI);
256 // The PHIs are now updated, change everything that refers to BB to use
257 // DestBB and remove BB.
258 BB->replaceAllUsesWith(DestBB);
259 BB->eraseFromParent();
261 DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
265 /// SplitEdgeNicely - Split the critical edge from TI to its specified
266 /// successor if it will improve codegen. We only do this if the successor has
267 /// phi nodes (otherwise critical edges are ok). If there is already another
268 /// predecessor of the succ that is empty (and thus has no phi nodes), use it
269 /// instead of introducing a new block.
270 static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
271 BasicBlock *TIBB = TI->getParent();
272 BasicBlock *Dest = TI->getSuccessor(SuccNum);
273 assert(isa<PHINode>(Dest->begin()) &&
274 "This should only be called if Dest has a PHI!");
276 // As a hack, never split backedges of loops. Even though the copy for any
277 // PHIs inserted on the backedge would be dead for exits from the loop, we
278 // assume that the cost of *splitting* the backedge would be too high.
282 /// TIPHIValues - This array is lazily computed to determine the values of
283 /// PHIs in Dest that TI would provide.
284 SmallVector<Value*, 32> TIPHIValues;
286 // Check to see if Dest has any blocks that can be used as a split edge for
288 for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
289 BasicBlock *Pred = *PI;
290 // To be usable, the pred has to end with an uncond branch to the dest.
291 BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
292 if (!PredBr || !PredBr->isUnconditional() ||
293 // Must be empty other than the branch.
294 &Pred->front() != PredBr ||
295 // Cannot be the entry block; its label does not get emitted.
296 Pred == &(Dest->getParent()->getEntryBlock()))
299 // Finally, since we know that Dest has phi nodes in it, we have to make
300 // sure that jumping to Pred will have the same affect as going to Dest in
301 // terms of PHI values.
304 bool FoundMatch = true;
305 for (BasicBlock::iterator I = Dest->begin();
306 (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
307 if (PHINo == TIPHIValues.size())
308 TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
310 // If the PHI entry doesn't work, we can't use this pred.
311 if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
317 // If we found a workable predecessor, change TI to branch to Succ.
319 Dest->removePredecessor(TIBB);
320 TI->setSuccessor(SuccNum, Pred);
325 SplitCriticalEdge(TI, SuccNum, P, true);
328 /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
329 /// copy (e.g. it's casting from one pointer type to another, int->uint, or
330 /// int->sbyte on PPC), sink it into user blocks to reduce the number of virtual
331 /// registers that must be created and coalesced.
333 /// Return true if any changes are made.
334 static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
335 // If this is a noop copy,
336 MVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
337 MVT DstVT = TLI.getValueType(CI->getType());
339 // This is an fp<->int conversion?
340 if (SrcVT.isInteger() != DstVT.isInteger())
343 // If this is an extension, it will be a zero or sign extension, which
345 if (SrcVT.bitsLT(DstVT)) return false;
347 // If these values will be promoted, find out what they will be promoted
348 // to. This helps us consider truncates on PPC as noop copies when they
350 if (TLI.getTypeAction(SrcVT) == TargetLowering::Promote)
351 SrcVT = TLI.getTypeToTransformTo(SrcVT);
352 if (TLI.getTypeAction(DstVT) == TargetLowering::Promote)
353 DstVT = TLI.getTypeToTransformTo(DstVT);
355 // If, after promotion, these are the same types, this is a noop copy.
359 BasicBlock *DefBB = CI->getParent();
361 /// InsertedCasts - Only insert a cast in each block once.
362 DenseMap<BasicBlock*, CastInst*> InsertedCasts;
364 bool MadeChange = false;
365 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
367 Use &TheUse = UI.getUse();
368 Instruction *User = cast<Instruction>(*UI);
370 // Figure out which BB this cast is used in. For PHI's this is the
371 // appropriate predecessor block.
372 BasicBlock *UserBB = User->getParent();
373 if (PHINode *PN = dyn_cast<PHINode>(User)) {
374 unsigned OpVal = UI.getOperandNo()/2;
375 UserBB = PN->getIncomingBlock(OpVal);
378 // Preincrement use iterator so we don't invalidate it.
381 // If this user is in the same block as the cast, don't change the cast.
382 if (UserBB == DefBB) continue;
384 // If we have already inserted a cast into this block, use it.
385 CastInst *&InsertedCast = InsertedCasts[UserBB];
388 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
391 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
396 // Replace a use of the cast with a use of the new cast.
397 TheUse = InsertedCast;
400 // If we removed all uses, nuke the cast.
401 if (CI->use_empty()) {
402 CI->eraseFromParent();
409 /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
410 /// the number of virtual registers that must be created and coalesced. This is
411 /// a clear win except on targets with multiple condition code registers
412 /// (PowerPC), where it might lose; some adjustment may be wanted there.
414 /// Return true if any changes are made.
415 static bool OptimizeCmpExpression(CmpInst *CI){
417 BasicBlock *DefBB = CI->getParent();
419 /// InsertedCmp - Only insert a cmp in each block once.
420 DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
422 bool MadeChange = false;
423 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
425 Use &TheUse = UI.getUse();
426 Instruction *User = cast<Instruction>(*UI);
428 // Preincrement use iterator so we don't invalidate it.
431 // Don't bother for PHI nodes.
432 if (isa<PHINode>(User))
435 // Figure out which BB this cmp is used in.
436 BasicBlock *UserBB = User->getParent();
438 // If this user is in the same block as the cmp, don't change the cmp.
439 if (UserBB == DefBB) continue;
441 // If we have already inserted a cmp into this block, use it.
442 CmpInst *&InsertedCmp = InsertedCmps[UserBB];
445 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
448 CmpInst::Create(CI->getOpcode(), CI->getPredicate(), CI->getOperand(0),
449 CI->getOperand(1), "", InsertPt);
453 // Replace a use of the cmp with a use of the new cmp.
454 TheUse = InsertedCmp;
457 // If we removed all uses, nuke the cmp.
459 CI->eraseFromParent();
464 /// EraseDeadInstructions - Erase any dead instructions
465 static void EraseDeadInstructions(Value *V) {
466 Instruction *I = dyn_cast<Instruction>(V);
467 if (!I || !I->use_empty()) return;
469 SmallPtrSet<Instruction*, 16> Insts;
472 while (!Insts.empty()) {
475 if (isInstructionTriviallyDead(I)) {
476 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
477 if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
479 I->eraseFromParent();
486 /// ExtAddrMode - This is an extended version of TargetLowering::AddrMode which
487 /// holds actual Value*'s for register values.
488 struct ExtAddrMode : public TargetLowering::AddrMode {
491 ExtAddrMode() : BaseReg(0), ScaledReg(0) {}
495 static std::ostream &operator<<(std::ostream &OS, const ExtAddrMode &AM) {
496 bool NeedPlus = false;
499 OS << (NeedPlus ? " + " : "")
500 << "GV:%" << AM.BaseGV->getName(), NeedPlus = true;
503 OS << (NeedPlus ? " + " : "") << AM.BaseOffs, NeedPlus = true;
506 OS << (NeedPlus ? " + " : "")
507 << "Base:%" << AM.BaseReg->getName(), NeedPlus = true;
509 OS << (NeedPlus ? " + " : "")
510 << AM.Scale << "*%" << AM.ScaledReg->getName(), NeedPlus = true;
515 void ExtAddrMode::dump() const {
516 cerr << *this << "\n";
521 static bool TryMatchingScaledValue(Value *ScaleReg, int64_t Scale,
522 const Type *AccessTy, ExtAddrMode &AddrMode,
523 SmallVector<Instruction*, 16> &AddrModeInsts,
524 const TargetLowering &TLI, unsigned Depth);
526 /// FindMaximalLegalAddressingMode - If we can, try to merge the computation of
527 /// Addr into the specified addressing mode. If Addr can't be added to AddrMode
528 /// this returns false. This assumes that Addr is either a pointer type or
529 /// intptr_t for the target.
530 static bool FindMaximalLegalAddressingMode(Value *Addr, const Type *AccessTy,
531 ExtAddrMode &AddrMode,
532 SmallVector<Instruction*, 16> &AddrModeInsts,
533 const TargetLowering &TLI,
536 // If this is a global variable, fold it into the addressing mode if possible.
537 if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
538 if (AddrMode.BaseGV == 0) {
539 AddrMode.BaseGV = GV;
540 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
544 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
545 AddrMode.BaseOffs += CI->getSExtValue();
546 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
548 AddrMode.BaseOffs -= CI->getSExtValue();
549 } else if (isa<ConstantPointerNull>(Addr)) {
553 // Look through constant exprs and instructions.
554 unsigned Opcode = ~0U;
556 if (Instruction *I = dyn_cast<Instruction>(Addr)) {
557 Opcode = I->getOpcode();
559 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
560 Opcode = CE->getOpcode();
564 // Limit recursion to avoid exponential behavior.
565 if (Depth == 5) { AddrInst = 0; Opcode = ~0U; }
567 // If this is really an instruction, add it to our list of related
569 if (Instruction *I = dyn_cast_or_null<Instruction>(AddrInst))
570 AddrModeInsts.push_back(I);
573 case Instruction::PtrToInt:
574 // PtrToInt is always a noop, as we know that the int type is pointer sized.
575 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
576 AddrMode, AddrModeInsts, TLI, Depth))
579 case Instruction::IntToPtr:
580 // This inttoptr is a no-op if the integer type is pointer sized.
581 if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
582 TLI.getPointerTy()) {
583 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
584 AddrMode, AddrModeInsts, TLI, Depth))
588 case Instruction::Add: {
589 // Check to see if we can merge in the RHS then the LHS. If so, we win.
590 ExtAddrMode BackupAddrMode = AddrMode;
591 unsigned OldSize = AddrModeInsts.size();
592 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(1), AccessTy,
593 AddrMode, AddrModeInsts, TLI, Depth+1) &&
594 FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
595 AddrMode, AddrModeInsts, TLI, Depth+1))
598 // Restore the old addr mode info.
599 AddrMode = BackupAddrMode;
600 AddrModeInsts.resize(OldSize);
602 // Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
603 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
604 AddrMode, AddrModeInsts, TLI, Depth+1) &&
605 FindMaximalLegalAddressingMode(AddrInst->getOperand(1), AccessTy,
606 AddrMode, AddrModeInsts, TLI, Depth+1))
609 // Otherwise we definitely can't merge the ADD in.
610 AddrMode = BackupAddrMode;
611 AddrModeInsts.resize(OldSize);
614 case Instruction::Or: {
615 ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
617 // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
620 case Instruction::Mul:
621 case Instruction::Shl: {
622 // Can only handle X*C and X << C, and can only handle this when the scale
623 // field is available.
624 ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
626 int64_t Scale = RHS->getSExtValue();
627 if (Opcode == Instruction::Shl)
630 if (TryMatchingScaledValue(AddrInst->getOperand(0), Scale, AccessTy,
631 AddrMode, AddrModeInsts, TLI, Depth))
635 case Instruction::GetElementPtr: {
636 // Scan the GEP. We check it if it contains constant offsets and at most
637 // one variable offset.
638 int VariableOperand = -1;
639 unsigned VariableScale = 0;
641 int64_t ConstantOffset = 0;
642 const TargetData *TD = TLI.getTargetData();
643 gep_type_iterator GTI = gep_type_begin(AddrInst);
644 for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
645 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
646 const StructLayout *SL = TD->getStructLayout(STy);
648 cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
649 ConstantOffset += SL->getElementOffset(Idx);
651 uint64_t TypeSize = TD->getABITypeSize(GTI.getIndexedType());
652 if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
653 ConstantOffset += CI->getSExtValue()*TypeSize;
654 } else if (TypeSize) { // Scales of zero don't do anything.
655 // We only allow one variable index at the moment.
656 if (VariableOperand != -1) {
657 VariableOperand = -2;
661 // Remember the variable index.
663 VariableScale = TypeSize;
668 // If the GEP had multiple variable indices, punt.
669 if (VariableOperand == -2)
672 // A common case is for the GEP to only do a constant offset. In this case,
673 // just add it to the disp field and check validity.
674 if (VariableOperand == -1) {
675 AddrMode.BaseOffs += ConstantOffset;
676 if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
677 // Check to see if we can fold the base pointer in too.
678 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
679 AddrMode, AddrModeInsts, TLI,
683 AddrMode.BaseOffs -= ConstantOffset;
685 // Check that this has no base reg yet. If so, we won't have a place to
686 // put the base of the GEP (assuming it is not a null ptr).
687 bool SetBaseReg = false;
688 if (AddrMode.HasBaseReg) {
689 if (!isa<ConstantPointerNull>(AddrInst->getOperand(0)))
692 AddrMode.HasBaseReg = true;
693 AddrMode.BaseReg = AddrInst->getOperand(0);
697 // See if the scale amount is valid for this target.
698 AddrMode.BaseOffs += ConstantOffset;
699 if (TryMatchingScaledValue(AddrInst->getOperand(VariableOperand),
700 VariableScale, AccessTy, AddrMode,
701 AddrModeInsts, TLI, Depth)) {
702 if (!SetBaseReg) return true;
704 // If this match succeeded, we know that we can form an address with the
705 // GepBase as the basereg. See if we can match *more*.
706 AddrMode.HasBaseReg = false;
707 AddrMode.BaseReg = 0;
708 if (FindMaximalLegalAddressingMode(AddrInst->getOperand(0), AccessTy,
709 AddrMode, AddrModeInsts, TLI,
712 // Strange, shouldn't happen. Restore the base reg and succeed the easy
714 AddrMode.HasBaseReg = true;
715 AddrMode.BaseReg = AddrInst->getOperand(0);
719 AddrMode.BaseOffs -= ConstantOffset;
721 AddrMode.HasBaseReg = false;
722 AddrMode.BaseReg = 0;
729 if (Instruction *I = dyn_cast_or_null<Instruction>(AddrInst)) {
730 assert(AddrModeInsts.back() == I && "Stack imbalance"); I = I;
731 AddrModeInsts.pop_back();
734 // Worse case, the target should support [reg] addressing modes. :)
735 if (!AddrMode.HasBaseReg) {
736 AddrMode.HasBaseReg = true;
737 // Still check for legality in case the target supports [imm] but not [i+r].
738 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) {
739 AddrMode.BaseReg = Addr;
742 AddrMode.HasBaseReg = false;
745 // If the base register is already taken, see if we can do [r+r].
746 if (AddrMode.Scale == 0) {
748 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) {
749 AddrMode.ScaledReg = Addr;
758 /// TryMatchingScaledValue - Try adding ScaleReg*Scale to the specified
759 /// addressing mode. Return true if this addr mode is legal for the target,
761 static bool TryMatchingScaledValue(Value *ScaleReg, int64_t Scale,
762 const Type *AccessTy, ExtAddrMode &AddrMode,
763 SmallVector<Instruction*, 16> &AddrModeInsts,
764 const TargetLowering &TLI, unsigned Depth) {
765 // If we already have a scale of this value, we can add to it, otherwise, we
766 // need an available scale field.
767 if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
770 ExtAddrMode InputAddrMode = AddrMode;
772 // Add scale to turn X*4+X*3 -> X*7. This could also do things like
773 // [A+B + A*7] -> [B+A*8].
774 AddrMode.Scale += Scale;
775 AddrMode.ScaledReg = ScaleReg;
777 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) {
778 // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
779 // to see if ScaleReg is actually X+C. If so, we can turn this into adding
780 // X*Scale + C*Scale to addr mode.
781 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(ScaleReg);
782 if (BinOp && BinOp->getOpcode() == Instruction::Add &&
783 isa<ConstantInt>(BinOp->getOperand(1)) && InputAddrMode.ScaledReg ==0) {
785 InputAddrMode.Scale = Scale;
786 InputAddrMode.ScaledReg = BinOp->getOperand(0);
787 InputAddrMode.BaseOffs +=
788 cast<ConstantInt>(BinOp->getOperand(1))->getSExtValue()*Scale;
789 if (TLI.isLegalAddressingMode(InputAddrMode, AccessTy)) {
790 AddrModeInsts.push_back(BinOp);
791 AddrMode = InputAddrMode;
796 // Otherwise, not (x+c)*scale, just return what we have.
800 // Otherwise, back this attempt out.
801 AddrMode.Scale -= Scale;
802 if (AddrMode.Scale == 0) AddrMode.ScaledReg = 0;
808 /// IsNonLocalValue - Return true if the specified values are defined in a
809 /// different basic block than BB.
810 static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
811 if (Instruction *I = dyn_cast<Instruction>(V))
812 return I->getParent() != BB;
816 /// OptimizeLoadStoreInst - Load and Store Instructions have often have
817 /// addressing modes that can do significant amounts of computation. As such,
818 /// instruction selection will try to get the load or store to do as much
819 /// computation as possible for the program. The problem is that isel can only
820 /// see within a single block. As such, we sink as much legal addressing mode
821 /// stuff into the block as possible.
822 bool CodeGenPrepare::OptimizeLoadStoreInst(Instruction *LdStInst, Value *Addr,
823 const Type *AccessTy,
824 DenseMap<Value*,Value*> &SunkAddrs) {
825 // Figure out what addressing mode will be built up for this operation.
826 SmallVector<Instruction*, 16> AddrModeInsts;
827 ExtAddrMode AddrMode;
828 bool Success = FindMaximalLegalAddressingMode(Addr, AccessTy, AddrMode,
829 AddrModeInsts, *TLI, 0);
830 Success = Success; assert(Success && "Couldn't select *anything*?");
832 // Check to see if any of the instructions supersumed by this addr mode are
833 // non-local to I's BB.
834 bool AnyNonLocal = false;
835 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
836 if (IsNonLocalValue(AddrModeInsts[i], LdStInst->getParent())) {
842 // If all the instructions matched are already in this BB, don't do anything.
844 DEBUG(cerr << "CGP: Found local addrmode: " << AddrMode << "\n");
848 // Insert this computation right after this user. Since our caller is
849 // scanning from the top of the BB to the bottom, reuse of the expr are
850 // guaranteed to happen later.
851 BasicBlock::iterator InsertPt = LdStInst;
853 // Now that we determined the addressing expression we want to use and know
854 // that we have to sink it into this block. Check to see if we have already
855 // done this for some other load/store instr in this block. If so, reuse the
857 Value *&SunkAddr = SunkAddrs[Addr];
859 DEBUG(cerr << "CGP: Reusing nonlocal addrmode: " << AddrMode << "\n");
860 if (SunkAddr->getType() != Addr->getType())
861 SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt);
863 DEBUG(cerr << "CGP: SINKING nonlocal addrmode: " << AddrMode << "\n");
864 const Type *IntPtrTy = TLI->getTargetData()->getIntPtrType();
867 // Start with the scale value.
868 if (AddrMode.Scale) {
869 Value *V = AddrMode.ScaledReg;
870 if (V->getType() == IntPtrTy) {
872 } else if (isa<PointerType>(V->getType())) {
873 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
874 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
875 cast<IntegerType>(V->getType())->getBitWidth()) {
876 V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt);
878 V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt);
880 if (AddrMode.Scale != 1)
881 V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
883 "sunkaddr", InsertPt);
887 // Add in the base register.
888 if (AddrMode.BaseReg) {
889 Value *V = AddrMode.BaseReg;
890 if (V->getType() != IntPtrTy)
891 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
893 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
898 // Add in the BaseGV if present.
899 if (AddrMode.BaseGV) {
900 Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr",
903 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
908 // Add in the Base Offset if present.
909 if (AddrMode.BaseOffs) {
910 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
912 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
918 SunkAddr = Constant::getNullValue(Addr->getType());
920 SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt);
923 LdStInst->replaceUsesOfWith(Addr, SunkAddr);
925 if (Addr->use_empty())
926 EraseDeadInstructions(Addr);
930 /// OptimizeInlineAsmInst - If there are any memory operands, use
931 /// OptimizeLoadStoreInt to sink their address computing into the block when
932 /// possible / profitable.
933 bool CodeGenPrepare::OptimizeInlineAsmInst(Instruction *I, CallSite CS,
934 DenseMap<Value*,Value*> &SunkAddrs) {
935 bool MadeChange = false;
936 InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue());
938 // Do a prepass over the constraints, canonicalizing them, and building up the
939 // ConstraintOperands list.
940 std::vector<InlineAsm::ConstraintInfo>
941 ConstraintInfos = IA->ParseConstraints();
943 /// ConstraintOperands - Information about all of the constraints.
944 std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands;
945 unsigned ArgNo = 0; // ArgNo - The argument of the CallInst.
946 for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) {
948 push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i]));
949 TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back();
951 // Compute the value type for each operand.
952 switch (OpInfo.Type) {
953 case InlineAsm::isOutput:
954 if (OpInfo.isIndirect)
955 OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
957 case InlineAsm::isInput:
958 OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
960 case InlineAsm::isClobber:
965 // Compute the constraint code and ConstraintType to use.
966 TLI->ComputeConstraintToUse(OpInfo, SDValue());
968 if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
970 Value *OpVal = OpInfo.CallOperandVal;
971 MadeChange |= OptimizeLoadStoreInst(I, OpVal, OpVal->getType(),
979 bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
980 BasicBlock *DefBB = I->getParent();
982 // If both result of the {s|z}xt and its source are live out, rewrite all
983 // other uses of the source with result of extension.
984 Value *Src = I->getOperand(0);
985 if (Src->hasOneUse())
988 // Only do this xform if truncating is free.
989 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
992 // Only safe to perform the optimization if the source is also defined in
994 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
997 bool DefIsLiveOut = false;
998 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
1000 Instruction *User = cast<Instruction>(*UI);
1002 // Figure out which BB this ext is used in.
1003 BasicBlock *UserBB = User->getParent();
1004 if (UserBB == DefBB) continue;
1005 DefIsLiveOut = true;
1011 // Make sure non of the uses are PHI nodes.
1012 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
1014 Instruction *User = cast<Instruction>(*UI);
1015 BasicBlock *UserBB = User->getParent();
1016 if (UserBB == DefBB) continue;
1017 // Be conservative. We don't want this xform to end up introducing
1018 // reloads just before load / store instructions.
1019 if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
1023 // InsertedTruncs - Only insert one trunc in each block once.
1024 DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
1026 bool MadeChange = false;
1027 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
1029 Use &TheUse = UI.getUse();
1030 Instruction *User = cast<Instruction>(*UI);
1032 // Figure out which BB this ext is used in.
1033 BasicBlock *UserBB = User->getParent();
1034 if (UserBB == DefBB) continue;
1036 // Both src and def are live in this block. Rewrite the use.
1037 Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
1039 if (!InsertedTrunc) {
1040 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
1042 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
1045 // Replace a use of the {s|z}ext source with a use of the result.
1046 TheUse = InsertedTrunc;
1054 // In this pass we look for GEP and cast instructions that are used
1055 // across basic blocks and rewrite them to improve basic-block-at-a-time
1057 bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
1058 bool MadeChange = false;
1060 // Split all critical edges where the dest block has a PHI and where the phi
1061 // has shared immediate operands.
1062 TerminatorInst *BBTI = BB.getTerminator();
1063 if (BBTI->getNumSuccessors() > 1) {
1064 for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i)
1065 if (isa<PHINode>(BBTI->getSuccessor(i)->begin()) &&
1066 isCriticalEdge(BBTI, i, true))
1067 SplitEdgeNicely(BBTI, i, this);
1071 // Keep track of non-local addresses that have been sunk into this block.
1072 // This allows us to avoid inserting duplicate code for blocks with multiple
1073 // load/stores of the same address.
1074 DenseMap<Value*, Value*> SunkAddrs;
1076 for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) {
1077 Instruction *I = BBI++;
1079 if (CastInst *CI = dyn_cast<CastInst>(I)) {
1080 // If the source of the cast is a constant, then this should have
1081 // already been constant folded. The only reason NOT to constant fold
1082 // it is if something (e.g. LSR) was careful to place the constant
1083 // evaluation in a block other than then one that uses it (e.g. to hoist
1084 // the address of globals out of a loop). If this is the case, we don't
1085 // want to forward-subst the cast.
1086 if (isa<Constant>(CI->getOperand(0)))
1089 bool Change = false;
1091 Change = OptimizeNoopCopyExpression(CI, *TLI);
1092 MadeChange |= Change;
1095 if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I)))
1096 MadeChange |= OptimizeExtUses(I);
1097 } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
1098 MadeChange |= OptimizeCmpExpression(CI);
1099 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
1101 MadeChange |= OptimizeLoadStoreInst(I, I->getOperand(0), LI->getType(),
1103 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
1105 MadeChange |= OptimizeLoadStoreInst(I, SI->getOperand(1),
1106 SI->getOperand(0)->getType(),
1108 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
1109 if (GEPI->hasAllZeroIndices()) {
1110 /// The GEP operand must be a pointer, so must its result -> BitCast
1111 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
1112 GEPI->getName(), GEPI);
1113 GEPI->replaceAllUsesWith(NC);
1114 GEPI->eraseFromParent();
1118 } else if (CallInst *CI = dyn_cast<CallInst>(I)) {
1119 // If we found an inline asm expession, and if the target knows how to
1120 // lower it to normal LLVM code, do so now.
1121 if (TLI && isa<InlineAsm>(CI->getCalledValue()))
1122 if (const TargetAsmInfo *TAI =
1123 TLI->getTargetMachine().getTargetAsmInfo()) {
1124 if (TAI->ExpandInlineAsm(CI))
1127 // Sink address computing for memory operands into the block.
1128 MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs);