IndVarSimplify.cpp revision bcfb913df0def0cb9f866e7811229768334144f3
1//===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This transformation analyzes and transforms the induction variables (and 11// computations derived from them) into simpler forms suitable for subsequent 12// analysis and transformation. 13// 14// This transformation make the following changes to each loop with an 15// identifiable induction variable: 16// 1. All loops are transformed to have a SINGLE canonical induction variable 17// which starts at zero and steps by one. 18// 2. The canonical induction variable is guaranteed to be the first PHI node 19// in the loop header block. 20// 3. Any pointer arithmetic recurrences are raised to use array subscripts. 21// 22// If the trip count of a loop is computable, this pass also makes the following 23// changes: 24// 1. The exit condition for the loop is canonicalized to compare the 25// induction value against the exit value. This turns loops like: 26// 'for (i = 7; i*i < 1000; ++i)' into 'for (i = 0; i != 25; ++i)' 27// 2. Any use outside of the loop of an expression derived from the indvar 28// is changed to compute the derived value outside of the loop, eliminating 29// the dependence on the exit value of the induction variable. If the only 30// purpose of the loop is to compute the exit value of some derived 31// expression, this transformation will make the loop dead. 32// 33// This transformation should be followed by strength reduction after all of the 34// desired loop transformations have been performed. Additionally, on targets 35// where it is profitable, the loop could be transformed to count down to zero 36// (the "do loop" optimization). 37// 38//===----------------------------------------------------------------------===// 39 40#include "llvm/Transforms/Scalar.h" 41#include "llvm/BasicBlock.h" 42#include "llvm/Constants.h" 43#include "llvm/Instructions.h" 44#include "llvm/Type.h" 45#include "llvm/Analysis/ScalarEvolutionExpander.h" 46#include "llvm/Analysis/LoopInfo.h" 47#include "llvm/Support/CFG.h" 48#include "llvm/Support/GetElementPtrTypeIterator.h" 49#include "llvm/Transforms/Utils/Local.h" 50#include "llvm/Support/CommandLine.h" 51#include "llvm/ADT/Statistic.h" 52using namespace llvm; 53 54namespace { 55 Statistic<> NumRemoved ("indvars", "Number of aux indvars removed"); 56 Statistic<> NumPointer ("indvars", "Number of pointer indvars promoted"); 57 Statistic<> NumInserted("indvars", "Number of canonical indvars added"); 58 Statistic<> NumReplaced("indvars", "Number of exit values replaced"); 59 Statistic<> NumLFTR ("indvars", "Number of loop exit tests replaced"); 60 61 class IndVarSimplify : public FunctionPass { 62 LoopInfo *LI; 63 ScalarEvolution *SE; 64 bool Changed; 65 public: 66 virtual bool runOnFunction(Function &) { 67 LI = &getAnalysis<LoopInfo>(); 68 SE = &getAnalysis<ScalarEvolution>(); 69 Changed = false; 70 71 // Induction Variables live in the header nodes of loops 72 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 73 runOnLoop(*I); 74 return Changed; 75 } 76 77 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 78 AU.addRequiredID(LoopSimplifyID); 79 AU.addRequired<ScalarEvolution>(); 80 AU.addRequired<LoopInfo>(); 81 AU.addPreservedID(LoopSimplifyID); 82 AU.addPreservedID(LCSSAID); 83 AU.setPreservesCFG(); 84 } 85 private: 86 void runOnLoop(Loop *L); 87 void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader, 88 std::set<Instruction*> &DeadInsts); 89 void LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, 90 SCEVExpander &RW); 91 void RewriteLoopExitValues(Loop *L); 92 93 void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts); 94 }; 95 RegisterOpt<IndVarSimplify> X("indvars", "Canonicalize Induction Variables"); 96} 97 98FunctionPass *llvm::createIndVarSimplifyPass() { 99 return new IndVarSimplify(); 100} 101 102/// DeleteTriviallyDeadInstructions - If any of the instructions is the 103/// specified set are trivially dead, delete them and see if this makes any of 104/// their operands subsequently dead. 105void IndVarSimplify:: 106DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) { 107 while (!Insts.empty()) { 108 Instruction *I = *Insts.begin(); 109 Insts.erase(Insts.begin()); 110 if (isInstructionTriviallyDead(I)) { 111 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 112 if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i))) 113 Insts.insert(U); 114 SE->deleteInstructionFromRecords(I); 115 I->eraseFromParent(); 116 Changed = true; 117 } 118 } 119} 120 121 122/// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer 123/// recurrence. If so, change it into an integer recurrence, permitting 124/// analysis by the SCEV routines. 125void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN, 126 BasicBlock *Preheader, 127 std::set<Instruction*> &DeadInsts) { 128 assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!"); 129 unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader); 130 unsigned BackedgeIdx = PreheaderIdx^1; 131 if (GetElementPtrInst *GEPI = 132 dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx))) 133 if (GEPI->getOperand(0) == PN) { 134 assert(GEPI->getNumOperands() == 2 && "GEP types must match!"); 135 136 // Okay, we found a pointer recurrence. Transform this pointer 137 // recurrence into an integer recurrence. Compute the value that gets 138 // added to the pointer at every iteration. 139 Value *AddedVal = GEPI->getOperand(1); 140 141 // Insert a new integer PHI node into the top of the block. 142 PHINode *NewPhi = new PHINode(AddedVal->getType(), 143 PN->getName()+".rec", PN); 144 NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), Preheader); 145 146 // Create the new add instruction. 147 Value *NewAdd = BinaryOperator::createAdd(NewPhi, AddedVal, 148 GEPI->getName()+".rec", GEPI); 149 NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx)); 150 151 // Update the existing GEP to use the recurrence. 152 GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx)); 153 154 // Update the GEP to use the new recurrence we just inserted. 155 GEPI->setOperand(1, NewAdd); 156 157 // If the incoming value is a constant expr GEP, try peeling out the array 158 // 0 index if possible to make things simpler. 159 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEPI->getOperand(0))) 160 if (CE->getOpcode() == Instruction::GetElementPtr) { 161 unsigned NumOps = CE->getNumOperands(); 162 assert(NumOps > 1 && "CE folding didn't work!"); 163 if (CE->getOperand(NumOps-1)->isNullValue()) { 164 // Check to make sure the last index really is an array index. 165 gep_type_iterator GTI = gep_type_begin(CE); 166 for (unsigned i = 1, e = CE->getNumOperands()-1; 167 i != e; ++i, ++GTI) 168 /*empty*/; 169 if (isa<SequentialType>(*GTI)) { 170 // Pull the last index out of the constant expr GEP. 171 std::vector<Value*> CEIdxs(CE->op_begin()+1, CE->op_end()-1); 172 Constant *NCE = ConstantExpr::getGetElementPtr(CE->getOperand(0), 173 CEIdxs); 174 GetElementPtrInst *NGEPI = 175 new GetElementPtrInst(NCE, Constant::getNullValue(Type::IntTy), 176 NewAdd, GEPI->getName(), GEPI); 177 GEPI->replaceAllUsesWith(NGEPI); 178 GEPI->eraseFromParent(); 179 GEPI = NGEPI; 180 } 181 } 182 } 183 184 185 // Finally, if there are any other users of the PHI node, we must 186 // insert a new GEP instruction that uses the pre-incremented version 187 // of the induction amount. 188 if (!PN->use_empty()) { 189 BasicBlock::iterator InsertPos = PN; ++InsertPos; 190 while (isa<PHINode>(InsertPos)) ++InsertPos; 191 std::string Name = PN->getName(); PN->setName(""); 192 Value *PreInc = 193 new GetElementPtrInst(PN->getIncomingValue(PreheaderIdx), 194 std::vector<Value*>(1, NewPhi), Name, 195 InsertPos); 196 PN->replaceAllUsesWith(PreInc); 197 } 198 199 // Delete the old PHI for sure, and the GEP if its otherwise unused. 200 DeadInsts.insert(PN); 201 202 ++NumPointer; 203 Changed = true; 204 } 205} 206 207/// LinearFunctionTestReplace - This method rewrites the exit condition of the 208/// loop to be a canonical != comparison against the incremented loop induction 209/// variable. This pass is able to rewrite the exit tests of any loop where the 210/// SCEV analysis can determine a loop-invariant trip count of the loop, which 211/// is actually a much broader range than just linear tests. 212void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, 213 SCEVExpander &RW) { 214 // Find the exit block for the loop. We can currently only handle loops with 215 // a single exit. 216 std::vector<BasicBlock*> ExitBlocks; 217 L->getExitBlocks(ExitBlocks); 218 if (ExitBlocks.size() != 1) return; 219 BasicBlock *ExitBlock = ExitBlocks[0]; 220 221 // Make sure there is only one predecessor block in the loop. 222 BasicBlock *ExitingBlock = 0; 223 for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock); 224 PI != PE; ++PI) 225 if (L->contains(*PI)) { 226 if (ExitingBlock == 0) 227 ExitingBlock = *PI; 228 else 229 return; // Multiple exits from loop to this block. 230 } 231 assert(ExitingBlock && "Loop info is broken"); 232 233 if (!isa<BranchInst>(ExitingBlock->getTerminator())) 234 return; // Can't rewrite non-branch yet 235 BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator()); 236 assert(BI->isConditional() && "Must be conditional to be part of loop!"); 237 238 std::set<Instruction*> InstructionsToDelete; 239 if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) 240 InstructionsToDelete.insert(Cond); 241 242 // If the exiting block is not the same as the backedge block, we must compare 243 // against the preincremented value, otherwise we prefer to compare against 244 // the post-incremented value. 245 BasicBlock *Header = L->getHeader(); 246 pred_iterator HPI = pred_begin(Header); 247 assert(HPI != pred_end(Header) && "Loop with zero preds???"); 248 if (!L->contains(*HPI)) ++HPI; 249 assert(HPI != pred_end(Header) && L->contains(*HPI) && 250 "No backedge in loop?"); 251 252 SCEVHandle TripCount = IterationCount; 253 Value *IndVar; 254 if (*HPI == ExitingBlock) { 255 // The IterationCount expression contains the number of times that the 256 // backedge actually branches to the loop header. This is one less than the 257 // number of times the loop executes, so add one to it. 258 Constant *OneC = ConstantInt::get(IterationCount->getType(), 1); 259 TripCount = SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC)); 260 IndVar = L->getCanonicalInductionVariableIncrement(); 261 } else { 262 // We have to use the preincremented value... 263 IndVar = L->getCanonicalInductionVariable(); 264 } 265 266 // Expand the code for the iteration count into the preheader of the loop. 267 BasicBlock *Preheader = L->getLoopPreheader(); 268 Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(), 269 IndVar->getType()); 270 271 // Insert a new setne or seteq instruction before the branch. 272 Instruction::BinaryOps Opcode; 273 if (L->contains(BI->getSuccessor(0))) 274 Opcode = Instruction::SetNE; 275 else 276 Opcode = Instruction::SetEQ; 277 278 Value *Cond = new SetCondInst(Opcode, IndVar, ExitCnt, "exitcond", BI); 279 BI->setCondition(Cond); 280 ++NumLFTR; 281 Changed = true; 282 283 DeleteTriviallyDeadInstructions(InstructionsToDelete); 284} 285 286 287/// RewriteLoopExitValues - Check to see if this loop has a computable 288/// loop-invariant execution count. If so, this means that we can compute the 289/// final value of any expressions that are recurrent in the loop, and 290/// substitute the exit values from the loop into any instructions outside of 291/// the loop that use the final values of the current expressions. 292void IndVarSimplify::RewriteLoopExitValues(Loop *L) { 293 BasicBlock *Preheader = L->getLoopPreheader(); 294 295 // Scan all of the instructions in the loop, looking at those that have 296 // extra-loop users and which are recurrences. 297 SCEVExpander Rewriter(*SE, *LI); 298 299 // We insert the code into the preheader of the loop if the loop contains 300 // multiple exit blocks, or in the exit block if there is exactly one. 301 BasicBlock *BlockToInsertInto; 302 std::vector<BasicBlock*> ExitBlocks; 303 L->getExitBlocks(ExitBlocks); 304 if (ExitBlocks.size() == 1) 305 BlockToInsertInto = ExitBlocks[0]; 306 else 307 BlockToInsertInto = Preheader; 308 BasicBlock::iterator InsertPt = BlockToInsertInto->begin(); 309 while (isa<PHINode>(InsertPt)) ++InsertPt; 310 311 bool HasConstantItCount = isa<SCEVConstant>(SE->getIterationCount(L)); 312 313 std::set<Instruction*> InstructionsToDelete; 314 315 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 316 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 317 BasicBlock *BB = L->getBlocks()[i]; 318 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) { 319 if (I->getType()->isInteger()) { // Is an integer instruction 320 SCEVHandle SH = SE->getSCEV(I); 321 if (SH->hasComputableLoopEvolution(L) || // Varies predictably 322 HasConstantItCount) { 323 // Find out if this predictably varying value is actually used 324 // outside of the loop. "extra" as opposed to "intra". 325 std::vector<Instruction*> ExtraLoopUsers; 326 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 327 UI != E; ++UI) { 328 Instruction *User = cast<Instruction>(*UI); 329 if (!L->contains(User->getParent())) 330 ExtraLoopUsers.push_back(User); 331 } 332 333 if (!ExtraLoopUsers.empty()) { 334 // Okay, this instruction has a user outside of the current loop 335 // and varies predictably in this loop. Evaluate the value it 336 // contains when the loop exits, and insert code for it. 337 SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop()); 338 if (!isa<SCEVCouldNotCompute>(ExitValue)) { 339 Changed = true; 340 ++NumReplaced; 341 // Remember the next instruction. The rewriter can move code 342 // around in some cases. 343 BasicBlock::iterator NextI = I; ++NextI; 344 345 Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt, 346 I->getType()); 347 348 // Rewrite any users of the computed value outside of the loop 349 // with the newly computed value. 350 for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) { 351 PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]); 352 if (PN && !L->contains(PN->getParent())) { 353 // We're dealing with an LCSSA Phi. Handle it specially. 354 Instruction* LCSSAInsertPt = BlockToInsertInto->begin(); 355 356 Instruction* NewInstr = dyn_cast<Instruction>(NewVal); 357 if (NewInstr && !isa<PHINode>(NewInstr) && 358 !L->contains(NewInstr->getParent())) 359 for (unsigned j = 0; j < NewInstr->getNumOperands(); ++j){ 360 Instruction* PredI = 361 dyn_cast<Instruction>(NewInstr->getOperand(j)); 362 if (PredI && L->contains(PredI->getParent())) { 363 PHINode* NewLCSSA = new PHINode(PredI->getType(), 364 PredI->getName() + ".lcssa", 365 LCSSAInsertPt); 366 NewLCSSA->addIncoming(PredI, 367 BlockToInsertInto->getSinglePredecessor()); 368 369 NewInstr->replaceUsesOfWith(PredI, NewLCSSA); 370 } 371 } 372 373 PN->replaceAllUsesWith(NewVal); 374 PN->eraseFromParent(); 375 } else { 376 ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal); 377 } 378 } 379 380 // If this instruction is dead now, schedule it to be removed. 381 if (I->use_empty()) 382 InstructionsToDelete.insert(I); 383 I = NextI; 384 continue; // Skip the ++I 385 } 386 } 387 } 388 } 389 390 // Next instruction. Continue instruction skips this. 391 ++I; 392 } 393 } 394 395 DeleteTriviallyDeadInstructions(InstructionsToDelete); 396} 397 398 399void IndVarSimplify::runOnLoop(Loop *L) { 400 // First step. Check to see if there are any trivial GEP pointer recurrences. 401 // If there are, change them into integer recurrences, permitting analysis by 402 // the SCEV routines. 403 // 404 BasicBlock *Header = L->getHeader(); 405 BasicBlock *Preheader = L->getLoopPreheader(); 406 407 std::set<Instruction*> DeadInsts; 408 for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 409 PHINode *PN = cast<PHINode>(I); 410 if (isa<PointerType>(PN->getType())) 411 EliminatePointerRecurrence(PN, Preheader, DeadInsts); 412 } 413 414 if (!DeadInsts.empty()) 415 DeleteTriviallyDeadInstructions(DeadInsts); 416 417 418 // Next, transform all loops nesting inside of this loop. 419 for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I) 420 runOnLoop(*I); 421 422 // Check to see if this loop has a computable loop-invariant execution count. 423 // If so, this means that we can compute the final value of any expressions 424 // that are recurrent in the loop, and substitute the exit values from the 425 // loop into any instructions outside of the loop that use the final values of 426 // the current expressions. 427 // 428 SCEVHandle IterationCount = SE->getIterationCount(L); 429 if (!isa<SCEVCouldNotCompute>(IterationCount)) 430 RewriteLoopExitValues(L); 431 432 // Next, analyze all of the induction variables in the loop, canonicalizing 433 // auxillary induction variables. 434 std::vector<std::pair<PHINode*, SCEVHandle> > IndVars; 435 436 for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 437 PHINode *PN = cast<PHINode>(I); 438 if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable! 439 SCEVHandle SCEV = SE->getSCEV(PN); 440 if (SCEV->hasComputableLoopEvolution(L)) 441 // FIXME: It is an extremely bad idea to indvar substitute anything more 442 // complex than affine induction variables. Doing so will put expensive 443 // polynomial evaluations inside of the loop, and the str reduction pass 444 // currently can only reduce affine polynomials. For now just disable 445 // indvar subst on anything more complex than an affine addrec. 446 if (SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SCEV)) 447 if (AR->isAffine()) 448 IndVars.push_back(std::make_pair(PN, SCEV)); 449 } 450 } 451 452 // If there are no induction variables in the loop, there is nothing more to 453 // do. 454 if (IndVars.empty()) { 455 // Actually, if we know how many times the loop iterates, lets insert a 456 // canonical induction variable to help subsequent passes. 457 if (!isa<SCEVCouldNotCompute>(IterationCount)) { 458 SCEVExpander Rewriter(*SE, *LI); 459 Rewriter.getOrInsertCanonicalInductionVariable(L, 460 IterationCount->getType()); 461 LinearFunctionTestReplace(L, IterationCount, Rewriter); 462 } 463 return; 464 } 465 466 // Compute the type of the largest recurrence expression. 467 // 468 const Type *LargestType = IndVars[0].first->getType(); 469 bool DifferingSizes = false; 470 for (unsigned i = 1, e = IndVars.size(); i != e; ++i) { 471 const Type *Ty = IndVars[i].first->getType(); 472 DifferingSizes |= Ty->getPrimitiveSize() != LargestType->getPrimitiveSize(); 473 if (Ty->getPrimitiveSize() > LargestType->getPrimitiveSize()) 474 LargestType = Ty; 475 } 476 477 // Create a rewriter object which we'll use to transform the code with. 478 SCEVExpander Rewriter(*SE, *LI); 479 480 // Now that we know the largest of of the induction variables in this loop, 481 // insert a canonical induction variable of the largest size. 482 LargestType = LargestType->getUnsignedVersion(); 483 Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType); 484 ++NumInserted; 485 Changed = true; 486 487 if (!isa<SCEVCouldNotCompute>(IterationCount)) 488 LinearFunctionTestReplace(L, IterationCount, Rewriter); 489 490 // Now that we have a canonical induction variable, we can rewrite any 491 // recurrences in terms of the induction variable. Start with the auxillary 492 // induction variables, and recursively rewrite any of their uses. 493 BasicBlock::iterator InsertPt = Header->begin(); 494 while (isa<PHINode>(InsertPt)) ++InsertPt; 495 496 // If there were induction variables of other sizes, cast the primary 497 // induction variable to the right size for them, avoiding the need for the 498 // code evaluation methods to insert induction variables of different sizes. 499 if (DifferingSizes) { 500 bool InsertedSizes[17] = { false }; 501 InsertedSizes[LargestType->getPrimitiveSize()] = true; 502 for (unsigned i = 0, e = IndVars.size(); i != e; ++i) 503 if (!InsertedSizes[IndVars[i].first->getType()->getPrimitiveSize()]) { 504 PHINode *PN = IndVars[i].first; 505 InsertedSizes[PN->getType()->getPrimitiveSize()] = true; 506 Instruction *New = new CastInst(IndVar, 507 PN->getType()->getUnsignedVersion(), 508 "indvar", InsertPt); 509 Rewriter.addInsertedValue(New, SE->getSCEV(New)); 510 } 511 } 512 513 // If there were induction variables of other sizes, cast the primary 514 // induction variable to the right size for them, avoiding the need for the 515 // code evaluation methods to insert induction variables of different sizes. 516 std::map<unsigned, Value*> InsertedSizes; 517 while (!IndVars.empty()) { 518 PHINode *PN = IndVars.back().first; 519 Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt, 520 PN->getType()); 521 std::string Name = PN->getName(); 522 PN->setName(""); 523 NewVal->setName(Name); 524 525 // Replace the old PHI Node with the inserted computation. 526 PN->replaceAllUsesWith(NewVal); 527 DeadInsts.insert(PN); 528 IndVars.pop_back(); 529 ++NumRemoved; 530 Changed = true; 531 } 532 533#if 0 534 // Now replace all derived expressions in the loop body with simpler 535 // expressions. 536 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 537 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 538 BasicBlock *BB = L->getBlocks()[i]; 539 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 540 if (I->getType()->isInteger() && // Is an integer instruction 541 !I->use_empty() && 542 !Rewriter.isInsertedInstruction(I)) { 543 SCEVHandle SH = SE->getSCEV(I); 544 Value *V = Rewriter.expandCodeFor(SH, I, I->getType()); 545 if (V != I) { 546 if (isa<Instruction>(V)) { 547 std::string Name = I->getName(); 548 I->setName(""); 549 V->setName(Name); 550 } 551 I->replaceAllUsesWith(V); 552 DeadInsts.insert(I); 553 ++NumRemoved; 554 Changed = true; 555 } 556 } 557 } 558#endif 559 560 DeleteTriviallyDeadInstructions(DeadInsts); 561} 562