IndVarSimplify.cpp revision 6934a04a8c15e9971cd1ea4d5c8df2d7afdd5be5
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 makes 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#define DEBUG_TYPE "indvars" 41#include "llvm/Transforms/Scalar.h" 42#include "llvm/BasicBlock.h" 43#include "llvm/Constants.h" 44#include "llvm/Instructions.h" 45#include "llvm/Type.h" 46#include "llvm/Analysis/ScalarEvolutionExpander.h" 47#include "llvm/Analysis/LoopInfo.h" 48#include "llvm/Support/CFG.h" 49#include "llvm/Support/Compiler.h" 50#include "llvm/Support/Debug.h" 51#include "llvm/Support/GetElementPtrTypeIterator.h" 52#include "llvm/Transforms/Utils/Local.h" 53#include "llvm/Support/CommandLine.h" 54#include "llvm/ADT/SmallVector.h" 55#include "llvm/ADT/Statistic.h" 56using namespace llvm; 57 58STATISTIC(NumRemoved , "Number of aux indvars removed"); 59STATISTIC(NumPointer , "Number of pointer indvars promoted"); 60STATISTIC(NumInserted, "Number of canonical indvars added"); 61STATISTIC(NumReplaced, "Number of exit values replaced"); 62STATISTIC(NumLFTR , "Number of loop exit tests replaced"); 63 64namespace { 65 class VISIBILITY_HIDDEN IndVarSimplify : public FunctionPass { 66 LoopInfo *LI; 67 ScalarEvolution *SE; 68 bool Changed; 69 public: 70 virtual bool runOnFunction(Function &) { 71 LI = &getAnalysis<LoopInfo>(); 72 SE = &getAnalysis<ScalarEvolution>(); 73 Changed = false; 74 75 // Induction Variables live in the header nodes of loops 76 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 77 runOnLoop(*I); 78 return Changed; 79 } 80 81 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 82 AU.addRequiredID(LoopSimplifyID); 83 AU.addRequired<ScalarEvolution>(); 84 AU.addRequired<LoopInfo>(); 85 AU.addPreservedID(LoopSimplifyID); 86 AU.addPreservedID(LCSSAID); 87 AU.setPreservesCFG(); 88 } 89 private: 90 void runOnLoop(Loop *L); 91 void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader, 92 std::set<Instruction*> &DeadInsts); 93 Instruction *LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, 94 SCEVExpander &RW); 95 void RewriteLoopExitValues(Loop *L); 96 97 void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts); 98 }; 99 RegisterPass<IndVarSimplify> X("indvars", "Canonicalize Induction Variables"); 100} 101 102FunctionPass *llvm::createIndVarSimplifyPass() { 103 return new IndVarSimplify(); 104} 105 106/// DeleteTriviallyDeadInstructions - If any of the instructions is the 107/// specified set are trivially dead, delete them and see if this makes any of 108/// their operands subsequently dead. 109void IndVarSimplify:: 110DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) { 111 while (!Insts.empty()) { 112 Instruction *I = *Insts.begin(); 113 Insts.erase(Insts.begin()); 114 if (isInstructionTriviallyDead(I)) { 115 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 116 if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i))) 117 Insts.insert(U); 118 SE->deleteInstructionFromRecords(I); 119 DOUT << "INDVARS: Deleting: " << *I; 120 I->eraseFromParent(); 121 Changed = true; 122 } 123 } 124} 125 126 127/// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer 128/// recurrence. If so, change it into an integer recurrence, permitting 129/// analysis by the SCEV routines. 130void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN, 131 BasicBlock *Preheader, 132 std::set<Instruction*> &DeadInsts) { 133 assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!"); 134 unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader); 135 unsigned BackedgeIdx = PreheaderIdx^1; 136 if (GetElementPtrInst *GEPI = 137 dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx))) 138 if (GEPI->getOperand(0) == PN) { 139 assert(GEPI->getNumOperands() == 2 && "GEP types must match!"); 140 DOUT << "INDVARS: Eliminating pointer recurrence: " << *GEPI; 141 142 // Okay, we found a pointer recurrence. Transform this pointer 143 // recurrence into an integer recurrence. Compute the value that gets 144 // added to the pointer at every iteration. 145 Value *AddedVal = GEPI->getOperand(1); 146 147 // Insert a new integer PHI node into the top of the block. 148 PHINode *NewPhi = new PHINode(AddedVal->getType(), 149 PN->getName()+".rec", PN); 150 NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), Preheader); 151 152 // Create the new add instruction. 153 Value *NewAdd = BinaryOperator::createAdd(NewPhi, AddedVal, 154 GEPI->getName()+".rec", GEPI); 155 NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx)); 156 157 // Update the existing GEP to use the recurrence. 158 GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx)); 159 160 // Update the GEP to use the new recurrence we just inserted. 161 GEPI->setOperand(1, NewAdd); 162 163 // If the incoming value is a constant expr GEP, try peeling out the array 164 // 0 index if possible to make things simpler. 165 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEPI->getOperand(0))) 166 if (CE->getOpcode() == Instruction::GetElementPtr) { 167 unsigned NumOps = CE->getNumOperands(); 168 assert(NumOps > 1 && "CE folding didn't work!"); 169 if (CE->getOperand(NumOps-1)->isNullValue()) { 170 // Check to make sure the last index really is an array index. 171 gep_type_iterator GTI = gep_type_begin(CE); 172 for (unsigned i = 1, e = CE->getNumOperands()-1; 173 i != e; ++i, ++GTI) 174 /*empty*/; 175 if (isa<SequentialType>(*GTI)) { 176 // Pull the last index out of the constant expr GEP. 177 SmallVector<Value*, 8> CEIdxs(CE->op_begin()+1, CE->op_end()-1); 178 Constant *NCE = ConstantExpr::getGetElementPtr(CE->getOperand(0), 179 &CEIdxs[0], 180 CEIdxs.size()); 181 GetElementPtrInst *NGEPI = 182 new GetElementPtrInst(NCE, Constant::getNullValue(Type::Int32Ty), 183 NewAdd, GEPI->getName(), GEPI); 184 GEPI->replaceAllUsesWith(NGEPI); 185 GEPI->eraseFromParent(); 186 GEPI = NGEPI; 187 } 188 } 189 } 190 191 192 // Finally, if there are any other users of the PHI node, we must 193 // insert a new GEP instruction that uses the pre-incremented version 194 // of the induction amount. 195 if (!PN->use_empty()) { 196 BasicBlock::iterator InsertPos = PN; ++InsertPos; 197 while (isa<PHINode>(InsertPos)) ++InsertPos; 198 Value *PreInc = 199 new GetElementPtrInst(PN->getIncomingValue(PreheaderIdx), 200 NewPhi, "", InsertPos); 201 PreInc->takeName(PN); 202 PN->replaceAllUsesWith(PreInc); 203 } 204 205 // Delete the old PHI for sure, and the GEP if its otherwise unused. 206 DeadInsts.insert(PN); 207 208 ++NumPointer; 209 Changed = true; 210 } 211} 212 213/// LinearFunctionTestReplace - This method rewrites the exit condition of the 214/// loop to be a canonical != comparison against the incremented loop induction 215/// variable. This pass is able to rewrite the exit tests of any loop where the 216/// SCEV analysis can determine a loop-invariant trip count of the loop, which 217/// is actually a much broader range than just linear tests. 218/// 219/// This method returns a "potentially dead" instruction whose computation chain 220/// should be deleted when convenient. 221Instruction *IndVarSimplify::LinearFunctionTestReplace(Loop *L, 222 SCEV *IterationCount, 223 SCEVExpander &RW) { 224 // Find the exit block for the loop. We can currently only handle loops with 225 // a single exit. 226 std::vector<BasicBlock*> ExitBlocks; 227 L->getExitBlocks(ExitBlocks); 228 if (ExitBlocks.size() != 1) return 0; 229 BasicBlock *ExitBlock = ExitBlocks[0]; 230 231 // Make sure there is only one predecessor block in the loop. 232 BasicBlock *ExitingBlock = 0; 233 for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock); 234 PI != PE; ++PI) 235 if (L->contains(*PI)) { 236 if (ExitingBlock == 0) 237 ExitingBlock = *PI; 238 else 239 return 0; // Multiple exits from loop to this block. 240 } 241 assert(ExitingBlock && "Loop info is broken"); 242 243 if (!isa<BranchInst>(ExitingBlock->getTerminator())) 244 return 0; // Can't rewrite non-branch yet 245 BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator()); 246 assert(BI->isConditional() && "Must be conditional to be part of loop!"); 247 248 Instruction *PotentiallyDeadInst = dyn_cast<Instruction>(BI->getCondition()); 249 250 // If the exiting block is not the same as the backedge block, we must compare 251 // against the preincremented value, otherwise we prefer to compare against 252 // the post-incremented value. 253 BasicBlock *Header = L->getHeader(); 254 pred_iterator HPI = pred_begin(Header); 255 assert(HPI != pred_end(Header) && "Loop with zero preds???"); 256 if (!L->contains(*HPI)) ++HPI; 257 assert(HPI != pred_end(Header) && L->contains(*HPI) && 258 "No backedge in loop?"); 259 260 SCEVHandle TripCount = IterationCount; 261 Value *IndVar; 262 if (*HPI == ExitingBlock) { 263 // The IterationCount expression contains the number of times that the 264 // backedge actually branches to the loop header. This is one less than the 265 // number of times the loop executes, so add one to it. 266 Constant *OneC = ConstantInt::get(IterationCount->getType(), 1); 267 TripCount = SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC)); 268 IndVar = L->getCanonicalInductionVariableIncrement(); 269 } else { 270 // We have to use the preincremented value... 271 IndVar = L->getCanonicalInductionVariable(); 272 } 273 274 DOUT << "INDVARS: LFTR: TripCount = " << *TripCount 275 << " IndVar = " << *IndVar << "\n"; 276 277 // Expand the code for the iteration count into the preheader of the loop. 278 BasicBlock *Preheader = L->getLoopPreheader(); 279 Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(), 280 IndVar->getType()); 281 282 // Insert a new icmp_ne or icmp_eq instruction before the branch. 283 ICmpInst::Predicate Opcode; 284 if (L->contains(BI->getSuccessor(0))) 285 Opcode = ICmpInst::ICMP_NE; 286 else 287 Opcode = ICmpInst::ICMP_EQ; 288 289 Value *Cond = new ICmpInst(Opcode, IndVar, ExitCnt, "exitcond", BI); 290 BI->setCondition(Cond); 291 ++NumLFTR; 292 Changed = true; 293 return PotentiallyDeadInst; 294} 295 296 297/// RewriteLoopExitValues - Check to see if this loop has a computable 298/// loop-invariant execution count. If so, this means that we can compute the 299/// final value of any expressions that are recurrent in the loop, and 300/// substitute the exit values from the loop into any instructions outside of 301/// the loop that use the final values of the current expressions. 302void IndVarSimplify::RewriteLoopExitValues(Loop *L) { 303 BasicBlock *Preheader = L->getLoopPreheader(); 304 305 // Scan all of the instructions in the loop, looking at those that have 306 // extra-loop users and which are recurrences. 307 SCEVExpander Rewriter(*SE, *LI); 308 309 // We insert the code into the preheader of the loop if the loop contains 310 // multiple exit blocks, or in the exit block if there is exactly one. 311 BasicBlock *BlockToInsertInto; 312 std::vector<BasicBlock*> ExitBlocks; 313 L->getExitBlocks(ExitBlocks); 314 if (ExitBlocks.size() == 1) 315 BlockToInsertInto = ExitBlocks[0]; 316 else 317 BlockToInsertInto = Preheader; 318 BasicBlock::iterator InsertPt = BlockToInsertInto->begin(); 319 while (isa<PHINode>(InsertPt)) ++InsertPt; 320 321 bool HasConstantItCount = isa<SCEVConstant>(SE->getIterationCount(L)); 322 323 std::set<Instruction*> InstructionsToDelete; 324 325 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 326 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 327 BasicBlock *BB = L->getBlocks()[i]; 328 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) { 329 if (I->getType()->isInteger()) { // Is an integer instruction 330 SCEVHandle SH = SE->getSCEV(I); 331 if (SH->hasComputableLoopEvolution(L) || // Varies predictably 332 HasConstantItCount) { 333 // Find out if this predictably varying value is actually used 334 // outside of the loop. "extra" as opposed to "intra". 335 std::vector<Instruction*> ExtraLoopUsers; 336 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 337 UI != E; ++UI) { 338 Instruction *User = cast<Instruction>(*UI); 339 if (!L->contains(User->getParent())) { 340 // If this is a PHI node in the exit block and we're inserting, 341 // into the exit block, it must have a single entry. In this 342 // case, we can't insert the code after the PHI and have the PHI 343 // still use it. Instead, don't insert the the PHI. 344 if (PHINode *PN = dyn_cast<PHINode>(User)) { 345 // FIXME: This is a case where LCSSA pessimizes code, this 346 // should be fixed better. 347 if (PN->getNumOperands() == 2 && 348 PN->getParent() == BlockToInsertInto) 349 continue; 350 } 351 ExtraLoopUsers.push_back(User); 352 } 353 } 354 355 if (!ExtraLoopUsers.empty()) { 356 // Okay, this instruction has a user outside of the current loop 357 // and varies predictably in this loop. Evaluate the value it 358 // contains when the loop exits, and insert code for it. 359 SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop()); 360 if (!isa<SCEVCouldNotCompute>(ExitValue)) { 361 Changed = true; 362 ++NumReplaced; 363 // Remember the next instruction. The rewriter can move code 364 // around in some cases. 365 BasicBlock::iterator NextI = I; ++NextI; 366 367 Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt, 368 I->getType()); 369 370 DOUT << "INDVARS: RLEV: AfterLoopVal = " << *NewVal 371 << " LoopVal = " << *I << "\n"; 372 373 // Rewrite any users of the computed value outside of the loop 374 // with the newly computed value. 375 for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) { 376 PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]); 377 if (PN && PN->getNumOperands() == 2 && 378 !L->contains(PN->getParent())) { 379 // We're dealing with an LCSSA Phi. Handle it specially. 380 Instruction* LCSSAInsertPt = BlockToInsertInto->begin(); 381 382 Instruction* NewInstr = dyn_cast<Instruction>(NewVal); 383 if (NewInstr && !isa<PHINode>(NewInstr) && 384 !L->contains(NewInstr->getParent())) 385 for (unsigned j = 0; j < NewInstr->getNumOperands(); ++j){ 386 Instruction* PredI = 387 dyn_cast<Instruction>(NewInstr->getOperand(j)); 388 if (PredI && L->contains(PredI->getParent())) { 389 PHINode* NewLCSSA = new PHINode(PredI->getType(), 390 PredI->getName() + ".lcssa", 391 LCSSAInsertPt); 392 NewLCSSA->addIncoming(PredI, 393 BlockToInsertInto->getSinglePredecessor()); 394 395 NewInstr->replaceUsesOfWith(PredI, NewLCSSA); 396 } 397 } 398 399 PN->replaceAllUsesWith(NewVal); 400 PN->eraseFromParent(); 401 } else { 402 ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal); 403 } 404 } 405 406 // If this instruction is dead now, schedule it to be removed. 407 if (I->use_empty()) 408 InstructionsToDelete.insert(I); 409 I = NextI; 410 continue; // Skip the ++I 411 } 412 } 413 } 414 } 415 416 // Next instruction. Continue instruction skips this. 417 ++I; 418 } 419 } 420 421 DeleteTriviallyDeadInstructions(InstructionsToDelete); 422} 423 424 425void IndVarSimplify::runOnLoop(Loop *L) { 426 // First step. Check to see if there are any trivial GEP pointer recurrences. 427 // If there are, change them into integer recurrences, permitting analysis by 428 // the SCEV routines. 429 // 430 BasicBlock *Header = L->getHeader(); 431 BasicBlock *Preheader = L->getLoopPreheader(); 432 433 std::set<Instruction*> DeadInsts; 434 for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 435 PHINode *PN = cast<PHINode>(I); 436 if (isa<PointerType>(PN->getType())) 437 EliminatePointerRecurrence(PN, Preheader, DeadInsts); 438 } 439 440 if (!DeadInsts.empty()) 441 DeleteTriviallyDeadInstructions(DeadInsts); 442 443 444 // Next, transform all loops nesting inside of this loop. 445 for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I) 446 runOnLoop(*I); 447 448 // Check to see if this loop has a computable loop-invariant execution count. 449 // If so, this means that we can compute the final value of any expressions 450 // that are recurrent in the loop, and substitute the exit values from the 451 // loop into any instructions outside of the loop that use the final values of 452 // the current expressions. 453 // 454 SCEVHandle IterationCount = SE->getIterationCount(L); 455 if (!isa<SCEVCouldNotCompute>(IterationCount)) 456 RewriteLoopExitValues(L); 457 458 // Next, analyze all of the induction variables in the loop, canonicalizing 459 // auxillary induction variables. 460 std::vector<std::pair<PHINode*, SCEVHandle> > IndVars; 461 462 for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 463 PHINode *PN = cast<PHINode>(I); 464 if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable! 465 SCEVHandle SCEV = SE->getSCEV(PN); 466 if (SCEV->hasComputableLoopEvolution(L)) 467 // FIXME: It is an extremely bad idea to indvar substitute anything more 468 // complex than affine induction variables. Doing so will put expensive 469 // polynomial evaluations inside of the loop, and the str reduction pass 470 // currently can only reduce affine polynomials. For now just disable 471 // indvar subst on anything more complex than an affine addrec. 472 if (SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SCEV)) 473 if (AR->isAffine()) 474 IndVars.push_back(std::make_pair(PN, SCEV)); 475 } 476 } 477 478 // If there are no induction variables in the loop, there is nothing more to 479 // do. 480 if (IndVars.empty()) { 481 // Actually, if we know how many times the loop iterates, lets insert a 482 // canonical induction variable to help subsequent passes. 483 if (!isa<SCEVCouldNotCompute>(IterationCount)) { 484 SCEVExpander Rewriter(*SE, *LI); 485 Rewriter.getOrInsertCanonicalInductionVariable(L, 486 IterationCount->getType()); 487 if (Instruction *I = LinearFunctionTestReplace(L, IterationCount, 488 Rewriter)) { 489 std::set<Instruction*> InstructionsToDelete; 490 InstructionsToDelete.insert(I); 491 DeleteTriviallyDeadInstructions(InstructionsToDelete); 492 } 493 } 494 return; 495 } 496 497 // Compute the type of the largest recurrence expression. 498 // 499 const Type *LargestType = IndVars[0].first->getType(); 500 bool DifferingSizes = false; 501 for (unsigned i = 1, e = IndVars.size(); i != e; ++i) { 502 const Type *Ty = IndVars[i].first->getType(); 503 DifferingSizes |= 504 Ty->getPrimitiveSizeInBits() != LargestType->getPrimitiveSizeInBits(); 505 if (Ty->getPrimitiveSizeInBits() > LargestType->getPrimitiveSizeInBits()) 506 LargestType = Ty; 507 } 508 509 // Create a rewriter object which we'll use to transform the code with. 510 SCEVExpander Rewriter(*SE, *LI); 511 512 // Now that we know the largest of of the induction variables in this loop, 513 // insert a canonical induction variable of the largest size. 514 Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType); 515 ++NumInserted; 516 Changed = true; 517 DOUT << "INDVARS: New CanIV: " << *IndVar; 518 519 if (!isa<SCEVCouldNotCompute>(IterationCount)) 520 if (Instruction *DI = LinearFunctionTestReplace(L, IterationCount,Rewriter)) 521 DeadInsts.insert(DI); 522 523 // Now that we have a canonical induction variable, we can rewrite any 524 // recurrences in terms of the induction variable. Start with the auxillary 525 // induction variables, and recursively rewrite any of their uses. 526 BasicBlock::iterator InsertPt = Header->begin(); 527 while (isa<PHINode>(InsertPt)) ++InsertPt; 528 529 // If there were induction variables of other sizes, cast the primary 530 // induction variable to the right size for them, avoiding the need for the 531 // code evaluation methods to insert induction variables of different sizes. 532 if (DifferingSizes) { 533 SmallVector<unsigned,4> InsertedSizes; 534 InsertedSizes.push_back(LargestType->getPrimitiveSizeInBits()); 535 for (unsigned i = 0, e = IndVars.size(); i != e; ++i) { 536 unsigned ithSize = IndVars[i].first->getType()->getPrimitiveSizeInBits(); 537 if (std::find(InsertedSizes.begin(), InsertedSizes.end(), ithSize) 538 == InsertedSizes.end()) { 539 PHINode *PN = IndVars[i].first; 540 InsertedSizes.push_back(ithSize); 541 Instruction *New = new TruncInst(IndVar, PN->getType(), "indvar", 542 InsertPt); 543 Rewriter.addInsertedValue(New, SE->getSCEV(New)); 544 DOUT << "INDVARS: Made trunc IV for " << *PN 545 << " NewVal = " << *New << "\n"; 546 } 547 } 548 } 549 550 // Rewrite all induction variables in terms of the canonical induction 551 // variable. 552 std::map<unsigned, Value*> InsertedSizes; 553 while (!IndVars.empty()) { 554 PHINode *PN = IndVars.back().first; 555 Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt, 556 PN->getType()); 557 DOUT << "INDVARS: Rewrote IV '" << *IndVars.back().second << "' " << *PN 558 << " into = " << *NewVal << "\n"; 559 NewVal->takeName(PN); 560 561 // Replace the old PHI Node with the inserted computation. 562 PN->replaceAllUsesWith(NewVal); 563 DeadInsts.insert(PN); 564 IndVars.pop_back(); 565 ++NumRemoved; 566 Changed = true; 567 } 568 569#if 0 570 // Now replace all derived expressions in the loop body with simpler 571 // expressions. 572 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 573 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 574 BasicBlock *BB = L->getBlocks()[i]; 575 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 576 if (I->getType()->isInteger() && // Is an integer instruction 577 !I->use_empty() && 578 !Rewriter.isInsertedInstruction(I)) { 579 SCEVHandle SH = SE->getSCEV(I); 580 Value *V = Rewriter.expandCodeFor(SH, I, I->getType()); 581 if (V != I) { 582 if (isa<Instruction>(V)) 583 V->takeName(I); 584 I->replaceAllUsesWith(V); 585 DeadInsts.insert(I); 586 ++NumRemoved; 587 Changed = true; 588 } 589 } 590 } 591#endif 592 593 DeleteTriviallyDeadInstructions(DeadInsts); 594 595 if (mustPreserveAnalysisID(LCSSAID)) assert(L->isLCSSAForm()); 596} 597