CodeGenPrepare.cpp revision ad80981a106c9d0ec83351e63ee3ac75ed646bf4
1//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 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. 13// 14//===----------------------------------------------------------------------===// 15 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/LLVMContext.h" 25#include "llvm/Pass.h" 26#include "llvm/Analysis/ProfileInfo.h" 27#include "llvm/Target/TargetData.h" 28#include "llvm/Target/TargetLowering.h" 29#include "llvm/Transforms/Utils/AddrModeMatcher.h" 30#include "llvm/Transforms/Utils/BasicBlockUtils.h" 31#include "llvm/Transforms/Utils/Local.h" 32#include "llvm/ADT/DenseMap.h" 33#include "llvm/ADT/SmallSet.h" 34#include "llvm/Assembly/Writer.h" 35#include "llvm/Support/CallSite.h" 36#include "llvm/Support/CommandLine.h" 37#include "llvm/Support/Debug.h" 38#include "llvm/Support/GetElementPtrTypeIterator.h" 39#include "llvm/Support/PatternMatch.h" 40#include "llvm/Support/raw_ostream.h" 41using namespace llvm; 42using namespace llvm::PatternMatch; 43 44static cl::opt<bool> FactorCommonPreds("split-critical-paths-tweak", 45 cl::init(false), cl::Hidden); 46 47namespace { 48 class CodeGenPrepare : public FunctionPass { 49 /// TLI - Keep a pointer of a TargetLowering to consult for determining 50 /// transformation profitability. 51 const TargetLowering *TLI; 52 ProfileInfo *PI; 53 54 /// BackEdges - Keep a set of all the loop back edges. 55 /// 56 SmallSet<std::pair<const BasicBlock*, const BasicBlock*>, 8> BackEdges; 57 public: 58 static char ID; // Pass identification, replacement for typeid 59 explicit CodeGenPrepare(const TargetLowering *tli = 0) 60 : FunctionPass(&ID), TLI(tli) {} 61 bool runOnFunction(Function &F); 62 63 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 64 AU.addPreserved<ProfileInfo>(); 65 } 66 67 private: 68 bool EliminateMostlyEmptyBlocks(Function &F); 69 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const; 70 void EliminateMostlyEmptyBlock(BasicBlock *BB); 71 bool OptimizeBlock(BasicBlock &BB); 72 bool OptimizeMemoryInst(Instruction *I, Value *Addr, const Type *AccessTy, 73 DenseMap<Value*,Value*> &SunkAddrs); 74 bool OptimizeInlineAsmInst(Instruction *I, CallSite CS, 75 DenseMap<Value*,Value*> &SunkAddrs); 76 bool OptimizeExtUses(Instruction *I); 77 void findLoopBackEdges(const Function &F); 78 }; 79} 80 81char CodeGenPrepare::ID = 0; 82static RegisterPass<CodeGenPrepare> X("codegenprepare", 83 "Optimize for code generation"); 84 85FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) { 86 return new CodeGenPrepare(TLI); 87} 88 89/// findLoopBackEdges - Do a DFS walk to find loop back edges. 90/// 91void CodeGenPrepare::findLoopBackEdges(const Function &F) { 92 SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges; 93 FindFunctionBackedges(F, Edges); 94 95 BackEdges.insert(Edges.begin(), Edges.end()); 96} 97 98 99bool CodeGenPrepare::runOnFunction(Function &F) { 100 bool EverMadeChange = false; 101 102 PI = getAnalysisIfAvailable<ProfileInfo>(); 103 // First pass, eliminate blocks that contain only PHI nodes and an 104 // unconditional branch. 105 EverMadeChange |= EliminateMostlyEmptyBlocks(F); 106 107 // Now find loop back edges. 108 findLoopBackEdges(F); 109 110 bool MadeChange = true; 111 while (MadeChange) { 112 MadeChange = false; 113 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 114 MadeChange |= OptimizeBlock(*BB); 115 EverMadeChange |= MadeChange; 116 } 117 return EverMadeChange; 118} 119 120/// 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 124/// want them. 125bool 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++; 130 131 // 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()) 134 continue; 135 136 // 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()) { 140 --BBI; 141 while (isa<DbgInfoIntrinsic>(BBI)) { 142 if (BBI == BB->begin()) 143 break; 144 --BBI; 145 } 146 if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI)) 147 continue; 148 } 149 150 // Do not break infinite loops. 151 BasicBlock *DestBB = BI->getSuccessor(0); 152 if (DestBB == BB) 153 continue; 154 155 if (!CanMergeBlocks(BB, DestBB)) 156 continue; 157 158 EliminateMostlyEmptyBlock(BB); 159 MadeChange = true; 160 } 161 return MadeChange; 162} 163 164/// 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 166/// instructions. 167bool 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(); 175 UI != E; ++UI) { 176 const Instruction *User = cast<Instruction>(*UI); 177 if (User->getParent() != DestBB || !isa<PHINode>(User)) 178 return false; 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)) 188 return false; 189 } 190 } 191 } 192 } 193 194 // 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. 199 200 // 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)); 206 } else { 207 BBPreds.insert(pred_begin(BB), pred_end(BB)); 208 } 209 210 // 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); 218 219 // 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); 223 224 // If there is a conflict, bail out. 225 if (V1 != V2) return false; 226 } 227 } 228 } 229 230 return true; 231} 232 233 234/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and 235/// an unconditional branch in it. 236void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) { 237 BranchInst *BI = cast<BranchInst>(BB->getTerminator()); 238 BasicBlock *DestBB = BI->getSuccessor(0); 239 240 DEBUG(errs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB); 241 242 // If the destination block has a single pred, then this is a trivial edge, 243 // just collapse it. 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); 250 251 if (isEntry && BB != &BB->getParent()->getEntryBlock()) 252 BB->moveBefore(&BB->getParent()->getEntryBlock()); 253 254 DEBUG(errs() << "AFTER:\n" << *DestBB << "\n\n\n"); 255 return; 256 } 257 } 258 259 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB 260 // to handle the new incoming edges it is about to have. 261 PHINode *PN; 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); 266 267 // 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)); 275 } else { 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)); 281 } else { 282 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 283 PN->addIncoming(InVal, *PI); 284 } 285 } 286 } 287 288 // The PHIs are now updated, change everything that refers to BB to use 289 // DestBB and remove BB. 290 BB->replaceAllUsesWith(DestBB); 291 if (PI) { 292 PI->replaceAllUses(BB, DestBB); 293 PI->removeEdge(ProfileInfo::getEdge(BB, DestBB)); 294 } 295 BB->eraseFromParent(); 296 297 DEBUG(errs() << "AFTER:\n" << *DestBB << "\n\n\n"); 298} 299 300 301/// 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. 306static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, 307 SmallSet<std::pair<const BasicBlock*, 308 const BasicBlock*>, 8> &BackEdges, 309 Pass *P) { 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!"); 314 315 // Do not split edges to EH landing pads. 316 if (InvokeInst *Invoke = dyn_cast<InvokeInst>(TI)) { 317 if (Invoke->getSuccessor(1) == Dest) 318 return; 319 } 320 321 // As a hack, never split backedges of loops. Even though the copy for any 322 // PHIs inserted on the backedge would be dead for exits from the loop, we 323 // assume that the cost of *splitting* the backedge would be too high. 324 if (BackEdges.count(std::make_pair(TIBB, Dest))) 325 return; 326 327 if (!FactorCommonPreds) { 328 /// TIPHIValues - This array is lazily computed to determine the values of 329 /// PHIs in Dest that TI would provide. 330 SmallVector<Value*, 32> TIPHIValues; 331 332 // Check to see if Dest has any blocks that can be used as a split edge for 333 // this terminator. 334 for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) { 335 BasicBlock *Pred = *PI; 336 // To be usable, the pred has to end with an uncond branch to the dest. 337 BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator()); 338 if (!PredBr || !PredBr->isUnconditional()) 339 continue; 340 // Must be empty other than the branch and debug info. 341 BasicBlock::iterator I = Pred->begin(); 342 while (isa<DbgInfoIntrinsic>(I)) 343 I++; 344 if (dyn_cast<Instruction>(I) != PredBr) 345 continue; 346 // Cannot be the entry block; its label does not get emitted. 347 if (Pred == &(Dest->getParent()->getEntryBlock())) 348 continue; 349 350 // Finally, since we know that Dest has phi nodes in it, we have to make 351 // sure that jumping to Pred will have the same effect as going to Dest in 352 // terms of PHI values. 353 PHINode *PN; 354 unsigned PHINo = 0; 355 bool FoundMatch = true; 356 for (BasicBlock::iterator I = Dest->begin(); 357 (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) { 358 if (PHINo == TIPHIValues.size()) 359 TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB)); 360 361 // If the PHI entry doesn't work, we can't use this pred. 362 if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) { 363 FoundMatch = false; 364 break; 365 } 366 } 367 368 // If we found a workable predecessor, change TI to branch to Succ. 369 if (FoundMatch) { 370 ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>(); 371 if (PI) 372 PI->splitEdge(TIBB, Dest, Pred); 373 Dest->removePredecessor(TIBB); 374 TI->setSuccessor(SuccNum, Pred); 375 return; 376 } 377 } 378 379 SplitCriticalEdge(TI, SuccNum, P, true); 380 return; 381 } 382 383 PHINode *PN; 384 SmallVector<Value*, 8> TIPHIValues; 385 for (BasicBlock::iterator I = Dest->begin(); 386 (PN = dyn_cast<PHINode>(I)); ++I) 387 TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB)); 388 389 SmallVector<BasicBlock*, 8> IdenticalPreds; 390 for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) { 391 BasicBlock *Pred = *PI; 392 if (BackEdges.count(std::make_pair(Pred, Dest))) 393 continue; 394 if (PI == TIBB) 395 IdenticalPreds.push_back(Pred); 396 else { 397 bool Identical = true; 398 unsigned PHINo = 0; 399 for (BasicBlock::iterator I = Dest->begin(); 400 (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) 401 if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) { 402 Identical = false; 403 break; 404 } 405 if (Identical) 406 IdenticalPreds.push_back(Pred); 407 } 408 } 409 410 assert(!IdenticalPreds.empty()); 411 SplitBlockPredecessors(Dest, &IdenticalPreds[0], IdenticalPreds.size(), 412 ".critedge", P); 413} 414 415 416/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop 417/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC), 418/// sink it into user blocks to reduce the number of virtual 419/// registers that must be created and coalesced. 420/// 421/// Return true if any changes are made. 422/// 423static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){ 424 // If this is a noop copy, 425 EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType()); 426 EVT DstVT = TLI.getValueType(CI->getType()); 427 428 // This is an fp<->int conversion? 429 if (SrcVT.isInteger() != DstVT.isInteger()) 430 return false; 431 432 // If this is an extension, it will be a zero or sign extension, which 433 // isn't a noop. 434 if (SrcVT.bitsLT(DstVT)) return false; 435 436 // If these values will be promoted, find out what they will be promoted 437 // to. This helps us consider truncates on PPC as noop copies when they 438 // are. 439 if (TLI.getTypeAction(CI->getContext(), SrcVT) == TargetLowering::Promote) 440 SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT); 441 if (TLI.getTypeAction(CI->getContext(), DstVT) == TargetLowering::Promote) 442 DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT); 443 444 // If, after promotion, these are the same types, this is a noop copy. 445 if (SrcVT != DstVT) 446 return false; 447 448 BasicBlock *DefBB = CI->getParent(); 449 450 /// InsertedCasts - Only insert a cast in each block once. 451 DenseMap<BasicBlock*, CastInst*> InsertedCasts; 452 453 bool MadeChange = false; 454 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end(); 455 UI != E; ) { 456 Use &TheUse = UI.getUse(); 457 Instruction *User = cast<Instruction>(*UI); 458 459 // Figure out which BB this cast is used in. For PHI's this is the 460 // appropriate predecessor block. 461 BasicBlock *UserBB = User->getParent(); 462 if (PHINode *PN = dyn_cast<PHINode>(User)) { 463 UserBB = PN->getIncomingBlock(UI); 464 } 465 466 // Preincrement use iterator so we don't invalidate it. 467 ++UI; 468 469 // If this user is in the same block as the cast, don't change the cast. 470 if (UserBB == DefBB) continue; 471 472 // If we have already inserted a cast into this block, use it. 473 CastInst *&InsertedCast = InsertedCasts[UserBB]; 474 475 if (!InsertedCast) { 476 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI(); 477 478 InsertedCast = 479 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "", 480 InsertPt); 481 MadeChange = true; 482 } 483 484 // Replace a use of the cast with a use of the new cast. 485 TheUse = InsertedCast; 486 } 487 488 // If we removed all uses, nuke the cast. 489 if (CI->use_empty()) { 490 CI->eraseFromParent(); 491 MadeChange = true; 492 } 493 494 return MadeChange; 495} 496 497/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce 498/// the number of virtual registers that must be created and coalesced. This is 499/// a clear win except on targets with multiple condition code registers 500/// (PowerPC), where it might lose; some adjustment may be wanted there. 501/// 502/// Return true if any changes are made. 503static bool OptimizeCmpExpression(CmpInst *CI) { 504 BasicBlock *DefBB = CI->getParent(); 505 506 /// InsertedCmp - Only insert a cmp in each block once. 507 DenseMap<BasicBlock*, CmpInst*> InsertedCmps; 508 509 bool MadeChange = false; 510 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end(); 511 UI != E; ) { 512 Use &TheUse = UI.getUse(); 513 Instruction *User = cast<Instruction>(*UI); 514 515 // Preincrement use iterator so we don't invalidate it. 516 ++UI; 517 518 // Don't bother for PHI nodes. 519 if (isa<PHINode>(User)) 520 continue; 521 522 // Figure out which BB this cmp is used in. 523 BasicBlock *UserBB = User->getParent(); 524 525 // If this user is in the same block as the cmp, don't change the cmp. 526 if (UserBB == DefBB) continue; 527 528 // If we have already inserted a cmp into this block, use it. 529 CmpInst *&InsertedCmp = InsertedCmps[UserBB]; 530 531 if (!InsertedCmp) { 532 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI(); 533 534 InsertedCmp = 535 CmpInst::Create(CI->getOpcode(), 536 CI->getPredicate(), CI->getOperand(0), 537 CI->getOperand(1), "", InsertPt); 538 MadeChange = true; 539 } 540 541 // Replace a use of the cmp with a use of the new cmp. 542 TheUse = InsertedCmp; 543 } 544 545 // If we removed all uses, nuke the cmp. 546 if (CI->use_empty()) 547 CI->eraseFromParent(); 548 549 return MadeChange; 550} 551 552//===----------------------------------------------------------------------===// 553// Memory Optimization 554//===----------------------------------------------------------------------===// 555 556/// IsNonLocalValue - Return true if the specified values are defined in a 557/// different basic block than BB. 558static bool IsNonLocalValue(Value *V, BasicBlock *BB) { 559 if (Instruction *I = dyn_cast<Instruction>(V)) 560 return I->getParent() != BB; 561 return false; 562} 563 564/// OptimizeMemoryInst - Load and Store Instructions have often have 565/// addressing modes that can do significant amounts of computation. As such, 566/// instruction selection will try to get the load or store to do as much 567/// computation as possible for the program. The problem is that isel can only 568/// see within a single block. As such, we sink as much legal addressing mode 569/// stuff into the block as possible. 570/// 571/// This method is used to optimize both load/store and inline asms with memory 572/// operands. 573bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr, 574 const Type *AccessTy, 575 DenseMap<Value*,Value*> &SunkAddrs) { 576 // Figure out what addressing mode will be built up for this operation. 577 SmallVector<Instruction*, 16> AddrModeInsts; 578 ExtAddrMode AddrMode = AddressingModeMatcher::Match(Addr, AccessTy,MemoryInst, 579 AddrModeInsts, *TLI); 580 581 // Check to see if any of the instructions supersumed by this addr mode are 582 // non-local to I's BB. 583 bool AnyNonLocal = false; 584 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) { 585 if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) { 586 AnyNonLocal = true; 587 break; 588 } 589 } 590 591 // If all the instructions matched are already in this BB, don't do anything. 592 if (!AnyNonLocal) { 593 DEBUG(errs() << "CGP: Found local addrmode: " << AddrMode << "\n"); 594 return false; 595 } 596 597 // Insert this computation right after this user. Since our caller is 598 // scanning from the top of the BB to the bottom, reuse of the expr are 599 // guaranteed to happen later. 600 BasicBlock::iterator InsertPt = MemoryInst; 601 602 // Now that we determined the addressing expression we want to use and know 603 // that we have to sink it into this block. Check to see if we have already 604 // done this for some other load/store instr in this block. If so, reuse the 605 // computation. 606 Value *&SunkAddr = SunkAddrs[Addr]; 607 if (SunkAddr) { 608 DEBUG(errs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for " 609 << *MemoryInst); 610 if (SunkAddr->getType() != Addr->getType()) 611 SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt); 612 } else { 613 DEBUG(errs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for " 614 << *MemoryInst); 615 const Type *IntPtrTy = 616 TLI->getTargetData()->getIntPtrType(AccessTy->getContext()); 617 618 Value *Result = 0; 619 // Start with the scale value. 620 if (AddrMode.Scale) { 621 Value *V = AddrMode.ScaledReg; 622 if (V->getType() == IntPtrTy) { 623 // done. 624 } else if (isa<PointerType>(V->getType())) { 625 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt); 626 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() < 627 cast<IntegerType>(V->getType())->getBitWidth()) { 628 V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt); 629 } else { 630 V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt); 631 } 632 if (AddrMode.Scale != 1) 633 V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy, 634 AddrMode.Scale), 635 "sunkaddr", InsertPt); 636 Result = V; 637 } 638 639 // Add in the base register. 640 if (AddrMode.BaseReg) { 641 Value *V = AddrMode.BaseReg; 642 if (isa<PointerType>(V->getType())) 643 V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt); 644 if (V->getType() != IntPtrTy) 645 V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true, 646 "sunkaddr", InsertPt); 647 if (Result) 648 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); 649 else 650 Result = V; 651 } 652 653 // Add in the BaseGV if present. 654 if (AddrMode.BaseGV) { 655 Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr", 656 InsertPt); 657 if (Result) 658 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); 659 else 660 Result = V; 661 } 662 663 // Add in the Base Offset if present. 664 if (AddrMode.BaseOffs) { 665 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs); 666 if (Result) 667 Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); 668 else 669 Result = V; 670 } 671 672 if (Result == 0) 673 SunkAddr = Constant::getNullValue(Addr->getType()); 674 else 675 SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt); 676 } 677 678 MemoryInst->replaceUsesOfWith(Addr, SunkAddr); 679 680 if (Addr->use_empty()) 681 RecursivelyDeleteTriviallyDeadInstructions(Addr); 682 return true; 683} 684 685/// OptimizeInlineAsmInst - If there are any memory operands, use 686/// OptimizeMemoryInst to sink their address computing into the block when 687/// possible / profitable. 688bool CodeGenPrepare::OptimizeInlineAsmInst(Instruction *I, CallSite CS, 689 DenseMap<Value*,Value*> &SunkAddrs) { 690 bool MadeChange = false; 691 InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue()); 692 693 // Do a prepass over the constraints, canonicalizing them, and building up the 694 // ConstraintOperands list. 695 std::vector<InlineAsm::ConstraintInfo> 696 ConstraintInfos = IA->ParseConstraints(); 697 698 /// ConstraintOperands - Information about all of the constraints. 699 std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands; 700 unsigned ArgNo = 0; // ArgNo - The argument of the CallInst. 701 for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) { 702 ConstraintOperands. 703 push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i])); 704 TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back(); 705 706 // Compute the value type for each operand. 707 switch (OpInfo.Type) { 708 case InlineAsm::isOutput: 709 if (OpInfo.isIndirect) 710 OpInfo.CallOperandVal = CS.getArgument(ArgNo++); 711 break; 712 case InlineAsm::isInput: 713 OpInfo.CallOperandVal = CS.getArgument(ArgNo++); 714 break; 715 case InlineAsm::isClobber: 716 // Nothing to do. 717 break; 718 } 719 720 // Compute the constraint code and ConstraintType to use. 721 TLI->ComputeConstraintToUse(OpInfo, SDValue(), 722 OpInfo.ConstraintType == TargetLowering::C_Memory); 723 724 if (OpInfo.ConstraintType == TargetLowering::C_Memory && 725 OpInfo.isIndirect) { 726 Value *OpVal = OpInfo.CallOperandVal; 727 MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs); 728 } 729 } 730 731 return MadeChange; 732} 733 734bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { 735 BasicBlock *DefBB = I->getParent(); 736 737 // If both result of the {s|z}xt and its source are live out, rewrite all 738 // other uses of the source with result of extension. 739 Value *Src = I->getOperand(0); 740 if (Src->hasOneUse()) 741 return false; 742 743 // Only do this xform if truncating is free. 744 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType())) 745 return false; 746 747 // Only safe to perform the optimization if the source is also defined in 748 // this block. 749 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent()) 750 return false; 751 752 bool DefIsLiveOut = false; 753 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 754 UI != E; ++UI) { 755 Instruction *User = cast<Instruction>(*UI); 756 757 // Figure out which BB this ext is used in. 758 BasicBlock *UserBB = User->getParent(); 759 if (UserBB == DefBB) continue; 760 DefIsLiveOut = true; 761 break; 762 } 763 if (!DefIsLiveOut) 764 return false; 765 766 // Make sure non of the uses are PHI nodes. 767 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); 768 UI != E; ++UI) { 769 Instruction *User = cast<Instruction>(*UI); 770 BasicBlock *UserBB = User->getParent(); 771 if (UserBB == DefBB) continue; 772 // Be conservative. We don't want this xform to end up introducing 773 // reloads just before load / store instructions. 774 if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User)) 775 return false; 776 } 777 778 // InsertedTruncs - Only insert one trunc in each block once. 779 DenseMap<BasicBlock*, Instruction*> InsertedTruncs; 780 781 bool MadeChange = false; 782 for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); 783 UI != E; ++UI) { 784 Use &TheUse = UI.getUse(); 785 Instruction *User = cast<Instruction>(*UI); 786 787 // Figure out which BB this ext is used in. 788 BasicBlock *UserBB = User->getParent(); 789 if (UserBB == DefBB) continue; 790 791 // Both src and def are live in this block. Rewrite the use. 792 Instruction *&InsertedTrunc = InsertedTruncs[UserBB]; 793 794 if (!InsertedTrunc) { 795 BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI(); 796 797 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt); 798 } 799 800 // Replace a use of the {s|z}ext source with a use of the result. 801 TheUse = InsertedTrunc; 802 803 MadeChange = true; 804 } 805 806 return MadeChange; 807} 808 809// In this pass we look for GEP and cast instructions that are used 810// across basic blocks and rewrite them to improve basic-block-at-a-time 811// selection. 812bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) { 813 bool MadeChange = false; 814 815 // Split all critical edges where the dest block has a PHI. 816 TerminatorInst *BBTI = BB.getTerminator(); 817 if (BBTI->getNumSuccessors() > 1) { 818 for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) { 819 BasicBlock *SuccBB = BBTI->getSuccessor(i); 820 if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true)) 821 SplitEdgeNicely(BBTI, i, BackEdges, this); 822 } 823 } 824 825 // Keep track of non-local addresses that have been sunk into this block. 826 // This allows us to avoid inserting duplicate code for blocks with multiple 827 // load/stores of the same address. 828 DenseMap<Value*, Value*> SunkAddrs; 829 830 for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) { 831 Instruction *I = BBI++; 832 833 if (CastInst *CI = dyn_cast<CastInst>(I)) { 834 // If the source of the cast is a constant, then this should have 835 // already been constant folded. The only reason NOT to constant fold 836 // it is if something (e.g. LSR) was careful to place the constant 837 // evaluation in a block other than then one that uses it (e.g. to hoist 838 // the address of globals out of a loop). If this is the case, we don't 839 // want to forward-subst the cast. 840 if (isa<Constant>(CI->getOperand(0))) 841 continue; 842 843 bool Change = false; 844 if (TLI) { 845 Change = OptimizeNoopCopyExpression(CI, *TLI); 846 MadeChange |= Change; 847 } 848 849 if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I))) 850 MadeChange |= OptimizeExtUses(I); 851 } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) { 852 MadeChange |= OptimizeCmpExpression(CI); 853 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 854 if (TLI) 855 MadeChange |= OptimizeMemoryInst(I, I->getOperand(0), LI->getType(), 856 SunkAddrs); 857 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 858 if (TLI) 859 MadeChange |= OptimizeMemoryInst(I, SI->getOperand(1), 860 SI->getOperand(0)->getType(), 861 SunkAddrs); 862 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 863 if (GEPI->hasAllZeroIndices()) { 864 /// The GEP operand must be a pointer, so must its result -> BitCast 865 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(), 866 GEPI->getName(), GEPI); 867 GEPI->replaceAllUsesWith(NC); 868 GEPI->eraseFromParent(); 869 MadeChange = true; 870 BBI = NC; 871 } 872 } else if (CallInst *CI = dyn_cast<CallInst>(I)) { 873 // If we found an inline asm expession, and if the target knows how to 874 // lower it to normal LLVM code, do so now. 875 if (TLI && isa<InlineAsm>(CI->getCalledValue())) { 876 if (TLI->ExpandInlineAsm(CI)) { 877 BBI = BB.begin(); 878 // Avoid processing instructions out of order, which could cause 879 // reuse before a value is defined. 880 SunkAddrs.clear(); 881 } else 882 // Sink address computing for memory operands into the block. 883 MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs); 884 } 885 } 886 } 887 888 return MadeChange; 889} 890