CodeGenPrepare.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f
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#include "llvm/CodeGen/Passes.h" 17#include "llvm/ADT/DenseMap.h" 18#include "llvm/ADT/SmallSet.h" 19#include "llvm/ADT/Statistic.h" 20#include "llvm/Analysis/InstructionSimplify.h" 21#include "llvm/IR/CallSite.h" 22#include "llvm/IR/Constants.h" 23#include "llvm/IR/DataLayout.h" 24#include "llvm/IR/DerivedTypes.h" 25#include "llvm/IR/Dominators.h" 26#include "llvm/IR/Function.h" 27#include "llvm/IR/GetElementPtrTypeIterator.h" 28#include "llvm/IR/IRBuilder.h" 29#include "llvm/IR/InlineAsm.h" 30#include "llvm/IR/Instructions.h" 31#include "llvm/IR/IntrinsicInst.h" 32#include "llvm/IR/PatternMatch.h" 33#include "llvm/IR/ValueHandle.h" 34#include "llvm/IR/ValueMap.h" 35#include "llvm/Pass.h" 36#include "llvm/Support/CommandLine.h" 37#include "llvm/Support/Debug.h" 38#include "llvm/Support/raw_ostream.h" 39#include "llvm/Target/TargetLibraryInfo.h" 40#include "llvm/Target/TargetLowering.h" 41#include "llvm/Target/TargetSubtargetInfo.h" 42#include "llvm/Transforms/Utils/BasicBlockUtils.h" 43#include "llvm/Transforms/Utils/BuildLibCalls.h" 44#include "llvm/Transforms/Utils/BypassSlowDivision.h" 45#include "llvm/Transforms/Utils/Local.h" 46using namespace llvm; 47using namespace llvm::PatternMatch; 48 49#define DEBUG_TYPE "codegenprepare" 50 51STATISTIC(NumBlocksElim, "Number of blocks eliminated"); 52STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated"); 53STATISTIC(NumGEPsElim, "Number of GEPs converted to casts"); 54STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of " 55 "sunken Cmps"); 56STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses " 57 "of sunken Casts"); 58STATISTIC(NumMemoryInsts, "Number of memory instructions whose address " 59 "computations were sunk"); 60STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads"); 61STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized"); 62STATISTIC(NumRetsDup, "Number of return instructions duplicated"); 63STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved"); 64STATISTIC(NumSelectsExpanded, "Number of selects turned into branches"); 65STATISTIC(NumAndCmpsMoved, "Number of and/cmp's pushed into branches"); 66 67static cl::opt<bool> DisableBranchOpts( 68 "disable-cgp-branch-opts", cl::Hidden, cl::init(false), 69 cl::desc("Disable branch optimizations in CodeGenPrepare")); 70 71static cl::opt<bool> DisableSelectToBranch( 72 "disable-cgp-select2branch", cl::Hidden, cl::init(false), 73 cl::desc("Disable select to branch conversion.")); 74 75static cl::opt<bool> AddrSinkUsingGEPs( 76 "addr-sink-using-gep", cl::Hidden, cl::init(false), 77 cl::desc("Address sinking in CGP using GEPs.")); 78 79static cl::opt<bool> EnableAndCmpSinking( 80 "enable-andcmp-sinking", cl::Hidden, cl::init(true), 81 cl::desc("Enable sinkinig and/cmp into branches.")); 82 83namespace { 84typedef SmallPtrSet<Instruction *, 16> SetOfInstrs; 85typedef DenseMap<Instruction *, Type *> InstrToOrigTy; 86 87 class CodeGenPrepare : public FunctionPass { 88 /// TLI - Keep a pointer of a TargetLowering to consult for determining 89 /// transformation profitability. 90 const TargetMachine *TM; 91 const TargetLowering *TLI; 92 const TargetLibraryInfo *TLInfo; 93 DominatorTree *DT; 94 95 /// CurInstIterator - As we scan instructions optimizing them, this is the 96 /// next instruction to optimize. Xforms that can invalidate this should 97 /// update it. 98 BasicBlock::iterator CurInstIterator; 99 100 /// Keeps track of non-local addresses that have been sunk into a block. 101 /// This allows us to avoid inserting duplicate code for blocks with 102 /// multiple load/stores of the same address. 103 ValueMap<Value*, Value*> SunkAddrs; 104 105 /// Keeps track of all truncates inserted for the current function. 106 SetOfInstrs InsertedTruncsSet; 107 /// Keeps track of the type of the related instruction before their 108 /// promotion for the current function. 109 InstrToOrigTy PromotedInsts; 110 111 /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to 112 /// be updated. 113 bool ModifiedDT; 114 115 /// OptSize - True if optimizing for size. 116 bool OptSize; 117 118 public: 119 static char ID; // Pass identification, replacement for typeid 120 explicit CodeGenPrepare(const TargetMachine *TM = nullptr) 121 : FunctionPass(ID), TM(TM), TLI(nullptr) { 122 initializeCodeGenPreparePass(*PassRegistry::getPassRegistry()); 123 } 124 bool runOnFunction(Function &F) override; 125 126 const char *getPassName() const override { return "CodeGen Prepare"; } 127 128 void getAnalysisUsage(AnalysisUsage &AU) const override { 129 AU.addPreserved<DominatorTreeWrapperPass>(); 130 AU.addRequired<TargetLibraryInfo>(); 131 } 132 133 private: 134 bool EliminateFallThrough(Function &F); 135 bool EliminateMostlyEmptyBlocks(Function &F); 136 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const; 137 void EliminateMostlyEmptyBlock(BasicBlock *BB); 138 bool OptimizeBlock(BasicBlock &BB); 139 bool OptimizeInst(Instruction *I); 140 bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy); 141 bool OptimizeInlineAsmInst(CallInst *CS); 142 bool OptimizeCallInst(CallInst *CI); 143 bool MoveExtToFormExtLoad(Instruction *I); 144 bool OptimizeExtUses(Instruction *I); 145 bool OptimizeSelectInst(SelectInst *SI); 146 bool OptimizeShuffleVectorInst(ShuffleVectorInst *SI); 147 bool DupRetToEnableTailCallOpts(BasicBlock *BB); 148 bool PlaceDbgValues(Function &F); 149 bool sinkAndCmp(Function &F); 150 }; 151} 152 153char CodeGenPrepare::ID = 0; 154static void *initializeCodeGenPreparePassOnce(PassRegistry &Registry) { 155 initializeTargetLibraryInfoPass(Registry); 156 PassInfo *PI = new PassInfo( 157 "Optimize for code generation", "codegenprepare", &CodeGenPrepare::ID, 158 PassInfo::NormalCtor_t(callDefaultCtor<CodeGenPrepare>), false, false, 159 PassInfo::TargetMachineCtor_t(callTargetMachineCtor<CodeGenPrepare>)); 160 Registry.registerPass(*PI, true); 161 return PI; 162} 163 164void llvm::initializeCodeGenPreparePass(PassRegistry &Registry) { 165 CALL_ONCE_INITIALIZATION(initializeCodeGenPreparePassOnce) 166} 167 168FunctionPass *llvm::createCodeGenPreparePass(const TargetMachine *TM) { 169 return new CodeGenPrepare(TM); 170} 171 172bool CodeGenPrepare::runOnFunction(Function &F) { 173 if (skipOptnoneFunction(F)) 174 return false; 175 176 bool EverMadeChange = false; 177 // Clear per function information. 178 InsertedTruncsSet.clear(); 179 PromotedInsts.clear(); 180 181 ModifiedDT = false; 182 if (TM) TLI = TM->getTargetLowering(); 183 TLInfo = &getAnalysis<TargetLibraryInfo>(); 184 DominatorTreeWrapperPass *DTWP = 185 getAnalysisIfAvailable<DominatorTreeWrapperPass>(); 186 DT = DTWP ? &DTWP->getDomTree() : nullptr; 187 OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex, 188 Attribute::OptimizeForSize); 189 190 /// This optimization identifies DIV instructions that can be 191 /// profitably bypassed and carried out with a shorter, faster divide. 192 if (!OptSize && TLI && TLI->isSlowDivBypassed()) { 193 const DenseMap<unsigned int, unsigned int> &BypassWidths = 194 TLI->getBypassSlowDivWidths(); 195 for (Function::iterator I = F.begin(); I != F.end(); I++) 196 EverMadeChange |= bypassSlowDivision(F, I, BypassWidths); 197 } 198 199 // Eliminate blocks that contain only PHI nodes and an 200 // unconditional branch. 201 EverMadeChange |= EliminateMostlyEmptyBlocks(F); 202 203 // llvm.dbg.value is far away from the value then iSel may not be able 204 // handle it properly. iSel will drop llvm.dbg.value if it can not 205 // find a node corresponding to the value. 206 EverMadeChange |= PlaceDbgValues(F); 207 208 // If there is a mask, compare against zero, and branch that can be combined 209 // into a single target instruction, push the mask and compare into branch 210 // users. Do this before OptimizeBlock -> OptimizeInst -> 211 // OptimizeCmpExpression, which perturbs the pattern being searched for. 212 if (!DisableBranchOpts) 213 EverMadeChange |= sinkAndCmp(F); 214 215 bool MadeChange = true; 216 while (MadeChange) { 217 MadeChange = false; 218 for (Function::iterator I = F.begin(); I != F.end(); ) { 219 BasicBlock *BB = I++; 220 MadeChange |= OptimizeBlock(*BB); 221 } 222 EverMadeChange |= MadeChange; 223 } 224 225 SunkAddrs.clear(); 226 227 if (!DisableBranchOpts) { 228 MadeChange = false; 229 SmallPtrSet<BasicBlock*, 8> WorkList; 230 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 231 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB)); 232 MadeChange |= ConstantFoldTerminator(BB, true); 233 if (!MadeChange) continue; 234 235 for (SmallVectorImpl<BasicBlock*>::iterator 236 II = Successors.begin(), IE = Successors.end(); II != IE; ++II) 237 if (pred_begin(*II) == pred_end(*II)) 238 WorkList.insert(*II); 239 } 240 241 // Delete the dead blocks and any of their dead successors. 242 MadeChange |= !WorkList.empty(); 243 while (!WorkList.empty()) { 244 BasicBlock *BB = *WorkList.begin(); 245 WorkList.erase(BB); 246 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB)); 247 248 DeleteDeadBlock(BB); 249 250 for (SmallVectorImpl<BasicBlock*>::iterator 251 II = Successors.begin(), IE = Successors.end(); II != IE; ++II) 252 if (pred_begin(*II) == pred_end(*II)) 253 WorkList.insert(*II); 254 } 255 256 // Merge pairs of basic blocks with unconditional branches, connected by 257 // a single edge. 258 if (EverMadeChange || MadeChange) 259 MadeChange |= EliminateFallThrough(F); 260 261 if (MadeChange) 262 ModifiedDT = true; 263 EverMadeChange |= MadeChange; 264 } 265 266 if (ModifiedDT && DT) 267 DT->recalculate(F); 268 269 return EverMadeChange; 270} 271 272/// EliminateFallThrough - Merge basic blocks which are connected 273/// by a single edge, where one of the basic blocks has a single successor 274/// pointing to the other basic block, which has a single predecessor. 275bool CodeGenPrepare::EliminateFallThrough(Function &F) { 276 bool Changed = false; 277 // Scan all of the blocks in the function, except for the entry block. 278 for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) { 279 BasicBlock *BB = I++; 280 // If the destination block has a single pred, then this is a trivial 281 // edge, just collapse it. 282 BasicBlock *SinglePred = BB->getSinglePredecessor(); 283 284 // Don't merge if BB's address is taken. 285 if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue; 286 287 BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator()); 288 if (Term && !Term->isConditional()) { 289 Changed = true; 290 DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n"); 291 // Remember if SinglePred was the entry block of the function. 292 // If so, we will need to move BB back to the entry position. 293 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock(); 294 MergeBasicBlockIntoOnlyPred(BB, this); 295 296 if (isEntry && BB != &BB->getParent()->getEntryBlock()) 297 BB->moveBefore(&BB->getParent()->getEntryBlock()); 298 299 // We have erased a block. Update the iterator. 300 I = BB; 301 } 302 } 303 return Changed; 304} 305 306/// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes, 307/// debug info directives, and an unconditional branch. Passes before isel 308/// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for 309/// isel. Start by eliminating these blocks so we can split them the way we 310/// want them. 311bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) { 312 bool MadeChange = false; 313 // Note that this intentionally skips the entry block. 314 for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) { 315 BasicBlock *BB = I++; 316 317 // If this block doesn't end with an uncond branch, ignore it. 318 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()); 319 if (!BI || !BI->isUnconditional()) 320 continue; 321 322 // If the instruction before the branch (skipping debug info) isn't a phi 323 // node, then other stuff is happening here. 324 BasicBlock::iterator BBI = BI; 325 if (BBI != BB->begin()) { 326 --BBI; 327 while (isa<DbgInfoIntrinsic>(BBI)) { 328 if (BBI == BB->begin()) 329 break; 330 --BBI; 331 } 332 if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI)) 333 continue; 334 } 335 336 // Do not break infinite loops. 337 BasicBlock *DestBB = BI->getSuccessor(0); 338 if (DestBB == BB) 339 continue; 340 341 if (!CanMergeBlocks(BB, DestBB)) 342 continue; 343 344 EliminateMostlyEmptyBlock(BB); 345 MadeChange = true; 346 } 347 return MadeChange; 348} 349 350/// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a 351/// single uncond branch between them, and BB contains no other non-phi 352/// instructions. 353bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB, 354 const BasicBlock *DestBB) const { 355 // We only want to eliminate blocks whose phi nodes are used by phi nodes in 356 // the successor. If there are more complex condition (e.g. preheaders), 357 // don't mess around with them. 358 BasicBlock::const_iterator BBI = BB->begin(); 359 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) { 360 for (const User *U : PN->users()) { 361 const Instruction *UI = cast<Instruction>(U); 362 if (UI->getParent() != DestBB || !isa<PHINode>(UI)) 363 return false; 364 // If User is inside DestBB block and it is a PHINode then check 365 // incoming value. If incoming value is not from BB then this is 366 // a complex condition (e.g. preheaders) we want to avoid here. 367 if (UI->getParent() == DestBB) { 368 if (const PHINode *UPN = dyn_cast<PHINode>(UI)) 369 for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) { 370 Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I)); 371 if (Insn && Insn->getParent() == BB && 372 Insn->getParent() != UPN->getIncomingBlock(I)) 373 return false; 374 } 375 } 376 } 377 } 378 379 // If BB and DestBB contain any common predecessors, then the phi nodes in BB 380 // and DestBB may have conflicting incoming values for the block. If so, we 381 // can't merge the block. 382 const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin()); 383 if (!DestBBPN) return true; // no conflict. 384 385 // Collect the preds of BB. 386 SmallPtrSet<const BasicBlock*, 16> BBPreds; 387 if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) { 388 // It is faster to get preds from a PHI than with pred_iterator. 389 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i) 390 BBPreds.insert(BBPN->getIncomingBlock(i)); 391 } else { 392 BBPreds.insert(pred_begin(BB), pred_end(BB)); 393 } 394 395 // Walk the preds of DestBB. 396 for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) { 397 BasicBlock *Pred = DestBBPN->getIncomingBlock(i); 398 if (BBPreds.count(Pred)) { // Common predecessor? 399 BBI = DestBB->begin(); 400 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) { 401 const Value *V1 = PN->getIncomingValueForBlock(Pred); 402 const Value *V2 = PN->getIncomingValueForBlock(BB); 403 404 // If V2 is a phi node in BB, look up what the mapped value will be. 405 if (const PHINode *V2PN = dyn_cast<PHINode>(V2)) 406 if (V2PN->getParent() == BB) 407 V2 = V2PN->getIncomingValueForBlock(Pred); 408 409 // If there is a conflict, bail out. 410 if (V1 != V2) return false; 411 } 412 } 413 } 414 415 return true; 416} 417 418 419/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and 420/// an unconditional branch in it. 421void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) { 422 BranchInst *BI = cast<BranchInst>(BB->getTerminator()); 423 BasicBlock *DestBB = BI->getSuccessor(0); 424 425 DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB); 426 427 // If the destination block has a single pred, then this is a trivial edge, 428 // just collapse it. 429 if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) { 430 if (SinglePred != DestBB) { 431 // Remember if SinglePred was the entry block of the function. If so, we 432 // will need to move BB back to the entry position. 433 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock(); 434 MergeBasicBlockIntoOnlyPred(DestBB, this); 435 436 if (isEntry && BB != &BB->getParent()->getEntryBlock()) 437 BB->moveBefore(&BB->getParent()->getEntryBlock()); 438 439 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); 440 return; 441 } 442 } 443 444 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB 445 // to handle the new incoming edges it is about to have. 446 PHINode *PN; 447 for (BasicBlock::iterator BBI = DestBB->begin(); 448 (PN = dyn_cast<PHINode>(BBI)); ++BBI) { 449 // Remove the incoming value for BB, and remember it. 450 Value *InVal = PN->removeIncomingValue(BB, false); 451 452 // Two options: either the InVal is a phi node defined in BB or it is some 453 // value that dominates BB. 454 PHINode *InValPhi = dyn_cast<PHINode>(InVal); 455 if (InValPhi && InValPhi->getParent() == BB) { 456 // Add all of the input values of the input PHI as inputs of this phi. 457 for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i) 458 PN->addIncoming(InValPhi->getIncomingValue(i), 459 InValPhi->getIncomingBlock(i)); 460 } else { 461 // Otherwise, add one instance of the dominating value for each edge that 462 // we will be adding. 463 if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) { 464 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i) 465 PN->addIncoming(InVal, BBPN->getIncomingBlock(i)); 466 } else { 467 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 468 PN->addIncoming(InVal, *PI); 469 } 470 } 471 } 472 473 // The PHIs are now updated, change everything that refers to BB to use 474 // DestBB and remove BB. 475 BB->replaceAllUsesWith(DestBB); 476 if (DT && !ModifiedDT) { 477 BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock(); 478 BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock(); 479 BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom); 480 DT->changeImmediateDominator(DestBB, NewIDom); 481 DT->eraseNode(BB); 482 } 483 BB->eraseFromParent(); 484 ++NumBlocksElim; 485 486 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); 487} 488 489/// SinkCast - Sink the specified cast instruction into its user blocks 490static bool SinkCast(CastInst *CI) { 491 BasicBlock *DefBB = CI->getParent(); 492 493 /// InsertedCasts - Only insert a cast in each block once. 494 DenseMap<BasicBlock*, CastInst*> InsertedCasts; 495 496 bool MadeChange = false; 497 for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end(); 498 UI != E; ) { 499 Use &TheUse = UI.getUse(); 500 Instruction *User = cast<Instruction>(*UI); 501 502 // Figure out which BB this cast is used in. For PHI's this is the 503 // appropriate predecessor block. 504 BasicBlock *UserBB = User->getParent(); 505 if (PHINode *PN = dyn_cast<PHINode>(User)) { 506 UserBB = PN->getIncomingBlock(TheUse); 507 } 508 509 // Preincrement use iterator so we don't invalidate it. 510 ++UI; 511 512 // If this user is in the same block as the cast, don't change the cast. 513 if (UserBB == DefBB) continue; 514 515 // If we have already inserted a cast into this block, use it. 516 CastInst *&InsertedCast = InsertedCasts[UserBB]; 517 518 if (!InsertedCast) { 519 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); 520 InsertedCast = 521 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "", 522 InsertPt); 523 MadeChange = true; 524 } 525 526 // Replace a use of the cast with a use of the new cast. 527 TheUse = InsertedCast; 528 ++NumCastUses; 529 } 530 531 // If we removed all uses, nuke the cast. 532 if (CI->use_empty()) { 533 CI->eraseFromParent(); 534 MadeChange = true; 535 } 536 537 return MadeChange; 538} 539 540/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop 541/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC), 542/// sink it into user blocks to reduce the number of virtual 543/// registers that must be created and coalesced. 544/// 545/// Return true if any changes are made. 546/// 547static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){ 548 // If this is a noop copy, 549 EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType()); 550 EVT DstVT = TLI.getValueType(CI->getType()); 551 552 // This is an fp<->int conversion? 553 if (SrcVT.isInteger() != DstVT.isInteger()) 554 return false; 555 556 // If this is an extension, it will be a zero or sign extension, which 557 // isn't a noop. 558 if (SrcVT.bitsLT(DstVT)) return false; 559 560 // If these values will be promoted, find out what they will be promoted 561 // to. This helps us consider truncates on PPC as noop copies when they 562 // are. 563 if (TLI.getTypeAction(CI->getContext(), SrcVT) == 564 TargetLowering::TypePromoteInteger) 565 SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT); 566 if (TLI.getTypeAction(CI->getContext(), DstVT) == 567 TargetLowering::TypePromoteInteger) 568 DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT); 569 570 // If, after promotion, these are the same types, this is a noop copy. 571 if (SrcVT != DstVT) 572 return false; 573 574 return SinkCast(CI); 575} 576 577/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce 578/// the number of virtual registers that must be created and coalesced. This is 579/// a clear win except on targets with multiple condition code registers 580/// (PowerPC), where it might lose; some adjustment may be wanted there. 581/// 582/// Return true if any changes are made. 583static bool OptimizeCmpExpression(CmpInst *CI) { 584 BasicBlock *DefBB = CI->getParent(); 585 586 /// InsertedCmp - Only insert a cmp in each block once. 587 DenseMap<BasicBlock*, CmpInst*> InsertedCmps; 588 589 bool MadeChange = false; 590 for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end(); 591 UI != E; ) { 592 Use &TheUse = UI.getUse(); 593 Instruction *User = cast<Instruction>(*UI); 594 595 // Preincrement use iterator so we don't invalidate it. 596 ++UI; 597 598 // Don't bother for PHI nodes. 599 if (isa<PHINode>(User)) 600 continue; 601 602 // Figure out which BB this cmp is used in. 603 BasicBlock *UserBB = User->getParent(); 604 605 // If this user is in the same block as the cmp, don't change the cmp. 606 if (UserBB == DefBB) continue; 607 608 // If we have already inserted a cmp into this block, use it. 609 CmpInst *&InsertedCmp = InsertedCmps[UserBB]; 610 611 if (!InsertedCmp) { 612 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); 613 InsertedCmp = 614 CmpInst::Create(CI->getOpcode(), 615 CI->getPredicate(), CI->getOperand(0), 616 CI->getOperand(1), "", InsertPt); 617 MadeChange = true; 618 } 619 620 // Replace a use of the cmp with a use of the new cmp. 621 TheUse = InsertedCmp; 622 ++NumCmpUses; 623 } 624 625 // If we removed all uses, nuke the cmp. 626 if (CI->use_empty()) 627 CI->eraseFromParent(); 628 629 return MadeChange; 630} 631 632/// isExtractBitsCandidateUse - Check if the candidates could 633/// be combined with shift instruction, which includes: 634/// 1. Truncate instruction 635/// 2. And instruction and the imm is a mask of the low bits: 636/// imm & (imm+1) == 0 637static bool isExtractBitsCandidateUse(Instruction *User) { 638 if (!isa<TruncInst>(User)) { 639 if (User->getOpcode() != Instruction::And || 640 !isa<ConstantInt>(User->getOperand(1))) 641 return false; 642 643 const APInt &Cimm = cast<ConstantInt>(User->getOperand(1))->getValue(); 644 645 if ((Cimm & (Cimm + 1)).getBoolValue()) 646 return false; 647 } 648 return true; 649} 650 651/// SinkShiftAndTruncate - sink both shift and truncate instruction 652/// to the use of truncate's BB. 653static bool 654SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI, 655 DenseMap<BasicBlock *, BinaryOperator *> &InsertedShifts, 656 const TargetLowering &TLI) { 657 BasicBlock *UserBB = User->getParent(); 658 DenseMap<BasicBlock *, CastInst *> InsertedTruncs; 659 TruncInst *TruncI = dyn_cast<TruncInst>(User); 660 bool MadeChange = false; 661 662 for (Value::user_iterator TruncUI = TruncI->user_begin(), 663 TruncE = TruncI->user_end(); 664 TruncUI != TruncE;) { 665 666 Use &TruncTheUse = TruncUI.getUse(); 667 Instruction *TruncUser = cast<Instruction>(*TruncUI); 668 // Preincrement use iterator so we don't invalidate it. 669 670 ++TruncUI; 671 672 int ISDOpcode = TLI.InstructionOpcodeToISD(TruncUser->getOpcode()); 673 if (!ISDOpcode) 674 continue; 675 676 // If the use is actually a legal node, there will not be an implicit 677 // truncate. 678 if (TLI.isOperationLegalOrCustom(ISDOpcode, 679 EVT::getEVT(TruncUser->getType()))) 680 continue; 681 682 // Don't bother for PHI nodes. 683 if (isa<PHINode>(TruncUser)) 684 continue; 685 686 BasicBlock *TruncUserBB = TruncUser->getParent(); 687 688 if (UserBB == TruncUserBB) 689 continue; 690 691 BinaryOperator *&InsertedShift = InsertedShifts[TruncUserBB]; 692 CastInst *&InsertedTrunc = InsertedTruncs[TruncUserBB]; 693 694 if (!InsertedShift && !InsertedTrunc) { 695 BasicBlock::iterator InsertPt = TruncUserBB->getFirstInsertionPt(); 696 // Sink the shift 697 if (ShiftI->getOpcode() == Instruction::AShr) 698 InsertedShift = 699 BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt); 700 else 701 InsertedShift = 702 BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt); 703 704 // Sink the trunc 705 BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt(); 706 TruncInsertPt++; 707 708 InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift, 709 TruncI->getType(), "", TruncInsertPt); 710 711 MadeChange = true; 712 713 TruncTheUse = InsertedTrunc; 714 } 715 } 716 return MadeChange; 717} 718 719/// OptimizeExtractBits - sink the shift *right* instruction into user blocks if 720/// the uses could potentially be combined with this shift instruction and 721/// generate BitExtract instruction. It will only be applied if the architecture 722/// supports BitExtract instruction. Here is an example: 723/// BB1: 724/// %x.extract.shift = lshr i64 %arg1, 32 725/// BB2: 726/// %x.extract.trunc = trunc i64 %x.extract.shift to i16 727/// ==> 728/// 729/// BB2: 730/// %x.extract.shift.1 = lshr i64 %arg1, 32 731/// %x.extract.trunc = trunc i64 %x.extract.shift.1 to i16 732/// 733/// CodeGen will recoginze the pattern in BB2 and generate BitExtract 734/// instruction. 735/// Return true if any changes are made. 736static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI, 737 const TargetLowering &TLI) { 738 BasicBlock *DefBB = ShiftI->getParent(); 739 740 /// Only insert instructions in each block once. 741 DenseMap<BasicBlock *, BinaryOperator *> InsertedShifts; 742 743 bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(ShiftI->getType())); 744 745 bool MadeChange = false; 746 for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end(); 747 UI != E;) { 748 Use &TheUse = UI.getUse(); 749 Instruction *User = cast<Instruction>(*UI); 750 // Preincrement use iterator so we don't invalidate it. 751 ++UI; 752 753 // Don't bother for PHI nodes. 754 if (isa<PHINode>(User)) 755 continue; 756 757 if (!isExtractBitsCandidateUse(User)) 758 continue; 759 760 BasicBlock *UserBB = User->getParent(); 761 762 if (UserBB == DefBB) { 763 // If the shift and truncate instruction are in the same BB. The use of 764 // the truncate(TruncUse) may still introduce another truncate if not 765 // legal. In this case, we would like to sink both shift and truncate 766 // instruction to the BB of TruncUse. 767 // for example: 768 // BB1: 769 // i64 shift.result = lshr i64 opnd, imm 770 // trunc.result = trunc shift.result to i16 771 // 772 // BB2: 773 // ----> We will have an implicit truncate here if the architecture does 774 // not have i16 compare. 775 // cmp i16 trunc.result, opnd2 776 // 777 if (isa<TruncInst>(User) && shiftIsLegal 778 // If the type of the truncate is legal, no trucate will be 779 // introduced in other basic blocks. 780 && (!TLI.isTypeLegal(TLI.getValueType(User->getType())))) 781 MadeChange = 782 SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI); 783 784 continue; 785 } 786 // If we have already inserted a shift into this block, use it. 787 BinaryOperator *&InsertedShift = InsertedShifts[UserBB]; 788 789 if (!InsertedShift) { 790 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); 791 792 if (ShiftI->getOpcode() == Instruction::AShr) 793 InsertedShift = 794 BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt); 795 else 796 InsertedShift = 797 BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt); 798 799 MadeChange = true; 800 } 801 802 // Replace a use of the shift with a use of the new shift. 803 TheUse = InsertedShift; 804 } 805 806 // If we removed all uses, nuke the shift. 807 if (ShiftI->use_empty()) 808 ShiftI->eraseFromParent(); 809 810 return MadeChange; 811} 812 813namespace { 814class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls { 815protected: 816 void replaceCall(Value *With) override { 817 CI->replaceAllUsesWith(With); 818 CI->eraseFromParent(); 819 } 820 bool isFoldable(unsigned SizeCIOp, unsigned, bool) const override { 821 if (ConstantInt *SizeCI = 822 dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp))) 823 return SizeCI->isAllOnesValue(); 824 return false; 825 } 826}; 827} // end anonymous namespace 828 829bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) { 830 BasicBlock *BB = CI->getParent(); 831 832 // Lower inline assembly if we can. 833 // If we found an inline asm expession, and if the target knows how to 834 // lower it to normal LLVM code, do so now. 835 if (TLI && isa<InlineAsm>(CI->getCalledValue())) { 836 if (TLI->ExpandInlineAsm(CI)) { 837 // Avoid invalidating the iterator. 838 CurInstIterator = BB->begin(); 839 // Avoid processing instructions out of order, which could cause 840 // reuse before a value is defined. 841 SunkAddrs.clear(); 842 return true; 843 } 844 // Sink address computing for memory operands into the block. 845 if (OptimizeInlineAsmInst(CI)) 846 return true; 847 } 848 849 // Lower all uses of llvm.objectsize.* 850 IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI); 851 if (II && II->getIntrinsicID() == Intrinsic::objectsize) { 852 bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1); 853 Type *ReturnTy = CI->getType(); 854 Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL); 855 856 // Substituting this can cause recursive simplifications, which can 857 // invalidate our iterator. Use a WeakVH to hold onto it in case this 858 // happens. 859 WeakVH IterHandle(CurInstIterator); 860 861 replaceAndRecursivelySimplify(CI, RetVal, 862 TLI ? TLI->getDataLayout() : nullptr, 863 TLInfo, ModifiedDT ? nullptr : DT); 864 865 // If the iterator instruction was recursively deleted, start over at the 866 // start of the block. 867 if (IterHandle != CurInstIterator) { 868 CurInstIterator = BB->begin(); 869 SunkAddrs.clear(); 870 } 871 return true; 872 } 873 874 if (II && TLI) { 875 SmallVector<Value*, 2> PtrOps; 876 Type *AccessTy; 877 if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy)) 878 while (!PtrOps.empty()) 879 if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy)) 880 return true; 881 } 882 883 // From here on out we're working with named functions. 884 if (!CI->getCalledFunction()) return false; 885 886 // We'll need DataLayout from here on out. 887 const DataLayout *TD = TLI ? TLI->getDataLayout() : nullptr; 888 if (!TD) return false; 889 890 // Lower all default uses of _chk calls. This is very similar 891 // to what InstCombineCalls does, but here we are only lowering calls 892 // that have the default "don't know" as the objectsize. Anything else 893 // should be left alone. 894 CodeGenPrepareFortifiedLibCalls Simplifier; 895 return Simplifier.fold(CI, TD, TLInfo); 896} 897 898/// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return 899/// instructions to the predecessor to enable tail call optimizations. The 900/// case it is currently looking for is: 901/// @code 902/// bb0: 903/// %tmp0 = tail call i32 @f0() 904/// br label %return 905/// bb1: 906/// %tmp1 = tail call i32 @f1() 907/// br label %return 908/// bb2: 909/// %tmp2 = tail call i32 @f2() 910/// br label %return 911/// return: 912/// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ] 913/// ret i32 %retval 914/// @endcode 915/// 916/// => 917/// 918/// @code 919/// bb0: 920/// %tmp0 = tail call i32 @f0() 921/// ret i32 %tmp0 922/// bb1: 923/// %tmp1 = tail call i32 @f1() 924/// ret i32 %tmp1 925/// bb2: 926/// %tmp2 = tail call i32 @f2() 927/// ret i32 %tmp2 928/// @endcode 929bool CodeGenPrepare::DupRetToEnableTailCallOpts(BasicBlock *BB) { 930 if (!TLI) 931 return false; 932 933 ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()); 934 if (!RI) 935 return false; 936 937 PHINode *PN = nullptr; 938 BitCastInst *BCI = nullptr; 939 Value *V = RI->getReturnValue(); 940 if (V) { 941 BCI = dyn_cast<BitCastInst>(V); 942 if (BCI) 943 V = BCI->getOperand(0); 944 945 PN = dyn_cast<PHINode>(V); 946 if (!PN) 947 return false; 948 } 949 950 if (PN && PN->getParent() != BB) 951 return false; 952 953 // It's not safe to eliminate the sign / zero extension of the return value. 954 // See llvm::isInTailCallPosition(). 955 const Function *F = BB->getParent(); 956 AttributeSet CallerAttrs = F->getAttributes(); 957 if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) || 958 CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt)) 959 return false; 960 961 // Make sure there are no instructions between the PHI and return, or that the 962 // return is the first instruction in the block. 963 if (PN) { 964 BasicBlock::iterator BI = BB->begin(); 965 do { ++BI; } while (isa<DbgInfoIntrinsic>(BI)); 966 if (&*BI == BCI) 967 // Also skip over the bitcast. 968 ++BI; 969 if (&*BI != RI) 970 return false; 971 } else { 972 BasicBlock::iterator BI = BB->begin(); 973 while (isa<DbgInfoIntrinsic>(BI)) ++BI; 974 if (&*BI != RI) 975 return false; 976 } 977 978 /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail 979 /// call. 980 SmallVector<CallInst*, 4> TailCalls; 981 if (PN) { 982 for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) { 983 CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I)); 984 // Make sure the phi value is indeed produced by the tail call. 985 if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) && 986 TLI->mayBeEmittedAsTailCall(CI)) 987 TailCalls.push_back(CI); 988 } 989 } else { 990 SmallPtrSet<BasicBlock*, 4> VisitedBBs; 991 for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) { 992 if (!VisitedBBs.insert(*PI)) 993 continue; 994 995 BasicBlock::InstListType &InstList = (*PI)->getInstList(); 996 BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin(); 997 BasicBlock::InstListType::reverse_iterator RE = InstList.rend(); 998 do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI)); 999 if (RI == RE) 1000 continue; 1001 1002 CallInst *CI = dyn_cast<CallInst>(&*RI); 1003 if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI)) 1004 TailCalls.push_back(CI); 1005 } 1006 } 1007 1008 bool Changed = false; 1009 for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) { 1010 CallInst *CI = TailCalls[i]; 1011 CallSite CS(CI); 1012 1013 // Conservatively require the attributes of the call to match those of the 1014 // return. Ignore noalias because it doesn't affect the call sequence. 1015 AttributeSet CalleeAttrs = CS.getAttributes(); 1016 if (AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex). 1017 removeAttribute(Attribute::NoAlias) != 1018 AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex). 1019 removeAttribute(Attribute::NoAlias)) 1020 continue; 1021 1022 // Make sure the call instruction is followed by an unconditional branch to 1023 // the return block. 1024 BasicBlock *CallBB = CI->getParent(); 1025 BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator()); 1026 if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB) 1027 continue; 1028 1029 // Duplicate the return into CallBB. 1030 (void)FoldReturnIntoUncondBranch(RI, BB, CallBB); 1031 ModifiedDT = Changed = true; 1032 ++NumRetsDup; 1033 } 1034 1035 // If we eliminated all predecessors of the block, delete the block now. 1036 if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB)) 1037 BB->eraseFromParent(); 1038 1039 return Changed; 1040} 1041 1042//===----------------------------------------------------------------------===// 1043// Memory Optimization 1044//===----------------------------------------------------------------------===// 1045 1046namespace { 1047 1048/// ExtAddrMode - This is an extended version of TargetLowering::AddrMode 1049/// which holds actual Value*'s for register values. 1050struct ExtAddrMode : public TargetLowering::AddrMode { 1051 Value *BaseReg; 1052 Value *ScaledReg; 1053 ExtAddrMode() : BaseReg(nullptr), ScaledReg(nullptr) {} 1054 void print(raw_ostream &OS) const; 1055 void dump() const; 1056 1057 bool operator==(const ExtAddrMode& O) const { 1058 return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) && 1059 (BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) && 1060 (HasBaseReg == O.HasBaseReg) && (Scale == O.Scale); 1061 } 1062}; 1063 1064#ifndef NDEBUG 1065static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) { 1066 AM.print(OS); 1067 return OS; 1068} 1069#endif 1070 1071void ExtAddrMode::print(raw_ostream &OS) const { 1072 bool NeedPlus = false; 1073 OS << "["; 1074 if (BaseGV) { 1075 OS << (NeedPlus ? " + " : "") 1076 << "GV:"; 1077 BaseGV->printAsOperand(OS, /*PrintType=*/false); 1078 NeedPlus = true; 1079 } 1080 1081 if (BaseOffs) 1082 OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true; 1083 1084 if (BaseReg) { 1085 OS << (NeedPlus ? " + " : "") 1086 << "Base:"; 1087 BaseReg->printAsOperand(OS, /*PrintType=*/false); 1088 NeedPlus = true; 1089 } 1090 if (Scale) { 1091 OS << (NeedPlus ? " + " : "") 1092 << Scale << "*"; 1093 ScaledReg->printAsOperand(OS, /*PrintType=*/false); 1094 } 1095 1096 OS << ']'; 1097} 1098 1099#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1100void ExtAddrMode::dump() const { 1101 print(dbgs()); 1102 dbgs() << '\n'; 1103} 1104#endif 1105 1106/// \brief This class provides transaction based operation on the IR. 1107/// Every change made through this class is recorded in the internal state and 1108/// can be undone (rollback) until commit is called. 1109class TypePromotionTransaction { 1110 1111 /// \brief This represents the common interface of the individual transaction. 1112 /// Each class implements the logic for doing one specific modification on 1113 /// the IR via the TypePromotionTransaction. 1114 class TypePromotionAction { 1115 protected: 1116 /// The Instruction modified. 1117 Instruction *Inst; 1118 1119 public: 1120 /// \brief Constructor of the action. 1121 /// The constructor performs the related action on the IR. 1122 TypePromotionAction(Instruction *Inst) : Inst(Inst) {} 1123 1124 virtual ~TypePromotionAction() {} 1125 1126 /// \brief Undo the modification done by this action. 1127 /// When this method is called, the IR must be in the same state as it was 1128 /// before this action was applied. 1129 /// \pre Undoing the action works if and only if the IR is in the exact same 1130 /// state as it was directly after this action was applied. 1131 virtual void undo() = 0; 1132 1133 /// \brief Advocate every change made by this action. 1134 /// When the results on the IR of the action are to be kept, it is important 1135 /// to call this function, otherwise hidden information may be kept forever. 1136 virtual void commit() { 1137 // Nothing to be done, this action is not doing anything. 1138 } 1139 }; 1140 1141 /// \brief Utility to remember the position of an instruction. 1142 class InsertionHandler { 1143 /// Position of an instruction. 1144 /// Either an instruction: 1145 /// - Is the first in a basic block: BB is used. 1146 /// - Has a previous instructon: PrevInst is used. 1147 union { 1148 Instruction *PrevInst; 1149 BasicBlock *BB; 1150 } Point; 1151 /// Remember whether or not the instruction had a previous instruction. 1152 bool HasPrevInstruction; 1153 1154 public: 1155 /// \brief Record the position of \p Inst. 1156 InsertionHandler(Instruction *Inst) { 1157 BasicBlock::iterator It = Inst; 1158 HasPrevInstruction = (It != (Inst->getParent()->begin())); 1159 if (HasPrevInstruction) 1160 Point.PrevInst = --It; 1161 else 1162 Point.BB = Inst->getParent(); 1163 } 1164 1165 /// \brief Insert \p Inst at the recorded position. 1166 void insert(Instruction *Inst) { 1167 if (HasPrevInstruction) { 1168 if (Inst->getParent()) 1169 Inst->removeFromParent(); 1170 Inst->insertAfter(Point.PrevInst); 1171 } else { 1172 Instruction *Position = Point.BB->getFirstInsertionPt(); 1173 if (Inst->getParent()) 1174 Inst->moveBefore(Position); 1175 else 1176 Inst->insertBefore(Position); 1177 } 1178 } 1179 }; 1180 1181 /// \brief Move an instruction before another. 1182 class InstructionMoveBefore : public TypePromotionAction { 1183 /// Original position of the instruction. 1184 InsertionHandler Position; 1185 1186 public: 1187 /// \brief Move \p Inst before \p Before. 1188 InstructionMoveBefore(Instruction *Inst, Instruction *Before) 1189 : TypePromotionAction(Inst), Position(Inst) { 1190 DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n"); 1191 Inst->moveBefore(Before); 1192 } 1193 1194 /// \brief Move the instruction back to its original position. 1195 void undo() override { 1196 DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n"); 1197 Position.insert(Inst); 1198 } 1199 }; 1200 1201 /// \brief Set the operand of an instruction with a new value. 1202 class OperandSetter : public TypePromotionAction { 1203 /// Original operand of the instruction. 1204 Value *Origin; 1205 /// Index of the modified instruction. 1206 unsigned Idx; 1207 1208 public: 1209 /// \brief Set \p Idx operand of \p Inst with \p NewVal. 1210 OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal) 1211 : TypePromotionAction(Inst), Idx(Idx) { 1212 DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n" 1213 << "for:" << *Inst << "\n" 1214 << "with:" << *NewVal << "\n"); 1215 Origin = Inst->getOperand(Idx); 1216 Inst->setOperand(Idx, NewVal); 1217 } 1218 1219 /// \brief Restore the original value of the instruction. 1220 void undo() override { 1221 DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n" 1222 << "for: " << *Inst << "\n" 1223 << "with: " << *Origin << "\n"); 1224 Inst->setOperand(Idx, Origin); 1225 } 1226 }; 1227 1228 /// \brief Hide the operands of an instruction. 1229 /// Do as if this instruction was not using any of its operands. 1230 class OperandsHider : public TypePromotionAction { 1231 /// The list of original operands. 1232 SmallVector<Value *, 4> OriginalValues; 1233 1234 public: 1235 /// \brief Remove \p Inst from the uses of the operands of \p Inst. 1236 OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) { 1237 DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n"); 1238 unsigned NumOpnds = Inst->getNumOperands(); 1239 OriginalValues.reserve(NumOpnds); 1240 for (unsigned It = 0; It < NumOpnds; ++It) { 1241 // Save the current operand. 1242 Value *Val = Inst->getOperand(It); 1243 OriginalValues.push_back(Val); 1244 // Set a dummy one. 1245 // We could use OperandSetter here, but that would implied an overhead 1246 // that we are not willing to pay. 1247 Inst->setOperand(It, UndefValue::get(Val->getType())); 1248 } 1249 } 1250 1251 /// \brief Restore the original list of uses. 1252 void undo() override { 1253 DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n"); 1254 for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It) 1255 Inst->setOperand(It, OriginalValues[It]); 1256 } 1257 }; 1258 1259 /// \brief Build a truncate instruction. 1260 class TruncBuilder : public TypePromotionAction { 1261 public: 1262 /// \brief Build a truncate instruction of \p Opnd producing a \p Ty 1263 /// result. 1264 /// trunc Opnd to Ty. 1265 TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) { 1266 IRBuilder<> Builder(Opnd); 1267 Inst = cast<Instruction>(Builder.CreateTrunc(Opnd, Ty, "promoted")); 1268 DEBUG(dbgs() << "Do: TruncBuilder: " << *Inst << "\n"); 1269 } 1270 1271 /// \brief Get the built instruction. 1272 Instruction *getBuiltInstruction() { return Inst; } 1273 1274 /// \brief Remove the built instruction. 1275 void undo() override { 1276 DEBUG(dbgs() << "Undo: TruncBuilder: " << *Inst << "\n"); 1277 Inst->eraseFromParent(); 1278 } 1279 }; 1280 1281 /// \brief Build a sign extension instruction. 1282 class SExtBuilder : public TypePromotionAction { 1283 public: 1284 /// \brief Build a sign extension instruction of \p Opnd producing a \p Ty 1285 /// result. 1286 /// sext Opnd to Ty. 1287 SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty) 1288 : TypePromotionAction(Inst) { 1289 IRBuilder<> Builder(InsertPt); 1290 Inst = cast<Instruction>(Builder.CreateSExt(Opnd, Ty, "promoted")); 1291 DEBUG(dbgs() << "Do: SExtBuilder: " << *Inst << "\n"); 1292 } 1293 1294 /// \brief Get the built instruction. 1295 Instruction *getBuiltInstruction() { return Inst; } 1296 1297 /// \brief Remove the built instruction. 1298 void undo() override { 1299 DEBUG(dbgs() << "Undo: SExtBuilder: " << *Inst << "\n"); 1300 Inst->eraseFromParent(); 1301 } 1302 }; 1303 1304 /// \brief Mutate an instruction to another type. 1305 class TypeMutator : public TypePromotionAction { 1306 /// Record the original type. 1307 Type *OrigTy; 1308 1309 public: 1310 /// \brief Mutate the type of \p Inst into \p NewTy. 1311 TypeMutator(Instruction *Inst, Type *NewTy) 1312 : TypePromotionAction(Inst), OrigTy(Inst->getType()) { 1313 DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy 1314 << "\n"); 1315 Inst->mutateType(NewTy); 1316 } 1317 1318 /// \brief Mutate the instruction back to its original type. 1319 void undo() override { 1320 DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy 1321 << "\n"); 1322 Inst->mutateType(OrigTy); 1323 } 1324 }; 1325 1326 /// \brief Replace the uses of an instruction by another instruction. 1327 class UsesReplacer : public TypePromotionAction { 1328 /// Helper structure to keep track of the replaced uses. 1329 struct InstructionAndIdx { 1330 /// The instruction using the instruction. 1331 Instruction *Inst; 1332 /// The index where this instruction is used for Inst. 1333 unsigned Idx; 1334 InstructionAndIdx(Instruction *Inst, unsigned Idx) 1335 : Inst(Inst), Idx(Idx) {} 1336 }; 1337 1338 /// Keep track of the original uses (pair Instruction, Index). 1339 SmallVector<InstructionAndIdx, 4> OriginalUses; 1340 typedef SmallVectorImpl<InstructionAndIdx>::iterator use_iterator; 1341 1342 public: 1343 /// \brief Replace all the use of \p Inst by \p New. 1344 UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) { 1345 DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New 1346 << "\n"); 1347 // Record the original uses. 1348 for (Use &U : Inst->uses()) { 1349 Instruction *UserI = cast<Instruction>(U.getUser()); 1350 OriginalUses.push_back(InstructionAndIdx(UserI, U.getOperandNo())); 1351 } 1352 // Now, we can replace the uses. 1353 Inst->replaceAllUsesWith(New); 1354 } 1355 1356 /// \brief Reassign the original uses of Inst to Inst. 1357 void undo() override { 1358 DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n"); 1359 for (use_iterator UseIt = OriginalUses.begin(), 1360 EndIt = OriginalUses.end(); 1361 UseIt != EndIt; ++UseIt) { 1362 UseIt->Inst->setOperand(UseIt->Idx, Inst); 1363 } 1364 } 1365 }; 1366 1367 /// \brief Remove an instruction from the IR. 1368 class InstructionRemover : public TypePromotionAction { 1369 /// Original position of the instruction. 1370 InsertionHandler Inserter; 1371 /// Helper structure to hide all the link to the instruction. In other 1372 /// words, this helps to do as if the instruction was removed. 1373 OperandsHider Hider; 1374 /// Keep track of the uses replaced, if any. 1375 UsesReplacer *Replacer; 1376 1377 public: 1378 /// \brief Remove all reference of \p Inst and optinally replace all its 1379 /// uses with New. 1380 /// \pre If !Inst->use_empty(), then New != nullptr 1381 InstructionRemover(Instruction *Inst, Value *New = nullptr) 1382 : TypePromotionAction(Inst), Inserter(Inst), Hider(Inst), 1383 Replacer(nullptr) { 1384 if (New) 1385 Replacer = new UsesReplacer(Inst, New); 1386 DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n"); 1387 Inst->removeFromParent(); 1388 } 1389 1390 ~InstructionRemover() { delete Replacer; } 1391 1392 /// \brief Really remove the instruction. 1393 void commit() override { delete Inst; } 1394 1395 /// \brief Resurrect the instruction and reassign it to the proper uses if 1396 /// new value was provided when build this action. 1397 void undo() override { 1398 DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n"); 1399 Inserter.insert(Inst); 1400 if (Replacer) 1401 Replacer->undo(); 1402 Hider.undo(); 1403 } 1404 }; 1405 1406public: 1407 /// Restoration point. 1408 /// The restoration point is a pointer to an action instead of an iterator 1409 /// because the iterator may be invalidated but not the pointer. 1410 typedef const TypePromotionAction *ConstRestorationPt; 1411 /// Advocate every changes made in that transaction. 1412 void commit(); 1413 /// Undo all the changes made after the given point. 1414 void rollback(ConstRestorationPt Point); 1415 /// Get the current restoration point. 1416 ConstRestorationPt getRestorationPoint() const; 1417 1418 /// \name API for IR modification with state keeping to support rollback. 1419 /// @{ 1420 /// Same as Instruction::setOperand. 1421 void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal); 1422 /// Same as Instruction::eraseFromParent. 1423 void eraseInstruction(Instruction *Inst, Value *NewVal = nullptr); 1424 /// Same as Value::replaceAllUsesWith. 1425 void replaceAllUsesWith(Instruction *Inst, Value *New); 1426 /// Same as Value::mutateType. 1427 void mutateType(Instruction *Inst, Type *NewTy); 1428 /// Same as IRBuilder::createTrunc. 1429 Instruction *createTrunc(Instruction *Opnd, Type *Ty); 1430 /// Same as IRBuilder::createSExt. 1431 Instruction *createSExt(Instruction *Inst, Value *Opnd, Type *Ty); 1432 /// Same as Instruction::moveBefore. 1433 void moveBefore(Instruction *Inst, Instruction *Before); 1434 /// @} 1435 1436private: 1437 /// The ordered list of actions made so far. 1438 SmallVector<std::unique_ptr<TypePromotionAction>, 16> Actions; 1439 typedef SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator CommitPt; 1440}; 1441 1442void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx, 1443 Value *NewVal) { 1444 Actions.push_back( 1445 make_unique<TypePromotionTransaction::OperandSetter>(Inst, Idx, NewVal)); 1446} 1447 1448void TypePromotionTransaction::eraseInstruction(Instruction *Inst, 1449 Value *NewVal) { 1450 Actions.push_back( 1451 make_unique<TypePromotionTransaction::InstructionRemover>(Inst, NewVal)); 1452} 1453 1454void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst, 1455 Value *New) { 1456 Actions.push_back(make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New)); 1457} 1458 1459void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) { 1460 Actions.push_back(make_unique<TypePromotionTransaction::TypeMutator>(Inst, NewTy)); 1461} 1462 1463Instruction *TypePromotionTransaction::createTrunc(Instruction *Opnd, 1464 Type *Ty) { 1465 std::unique_ptr<TruncBuilder> Ptr(new TruncBuilder(Opnd, Ty)); 1466 Instruction *I = Ptr->getBuiltInstruction(); 1467 Actions.push_back(std::move(Ptr)); 1468 return I; 1469} 1470 1471Instruction *TypePromotionTransaction::createSExt(Instruction *Inst, 1472 Value *Opnd, Type *Ty) { 1473 std::unique_ptr<SExtBuilder> Ptr(new SExtBuilder(Inst, Opnd, Ty)); 1474 Instruction *I = Ptr->getBuiltInstruction(); 1475 Actions.push_back(std::move(Ptr)); 1476 return I; 1477} 1478 1479void TypePromotionTransaction::moveBefore(Instruction *Inst, 1480 Instruction *Before) { 1481 Actions.push_back( 1482 make_unique<TypePromotionTransaction::InstructionMoveBefore>(Inst, Before)); 1483} 1484 1485TypePromotionTransaction::ConstRestorationPt 1486TypePromotionTransaction::getRestorationPoint() const { 1487 return !Actions.empty() ? Actions.back().get() : nullptr; 1488} 1489 1490void TypePromotionTransaction::commit() { 1491 for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt; 1492 ++It) 1493 (*It)->commit(); 1494 Actions.clear(); 1495} 1496 1497void TypePromotionTransaction::rollback( 1498 TypePromotionTransaction::ConstRestorationPt Point) { 1499 while (!Actions.empty() && Point != Actions.back().get()) { 1500 std::unique_ptr<TypePromotionAction> Curr = Actions.pop_back_val(); 1501 Curr->undo(); 1502 } 1503} 1504 1505/// \brief A helper class for matching addressing modes. 1506/// 1507/// This encapsulates the logic for matching the target-legal addressing modes. 1508class AddressingModeMatcher { 1509 SmallVectorImpl<Instruction*> &AddrModeInsts; 1510 const TargetLowering &TLI; 1511 1512 /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and 1513 /// the memory instruction that we're computing this address for. 1514 Type *AccessTy; 1515 Instruction *MemoryInst; 1516 1517 /// AddrMode - This is the addressing mode that we're building up. This is 1518 /// part of the return value of this addressing mode matching stuff. 1519 ExtAddrMode &AddrMode; 1520 1521 /// The truncate instruction inserted by other CodeGenPrepare optimizations. 1522 const SetOfInstrs &InsertedTruncs; 1523 /// A map from the instructions to their type before promotion. 1524 InstrToOrigTy &PromotedInsts; 1525 /// The ongoing transaction where every action should be registered. 1526 TypePromotionTransaction &TPT; 1527 1528 /// IgnoreProfitability - This is set to true when we should not do 1529 /// profitability checks. When true, IsProfitableToFoldIntoAddressingMode 1530 /// always returns true. 1531 bool IgnoreProfitability; 1532 1533 AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI, 1534 const TargetLowering &T, Type *AT, 1535 Instruction *MI, ExtAddrMode &AM, 1536 const SetOfInstrs &InsertedTruncs, 1537 InstrToOrigTy &PromotedInsts, 1538 TypePromotionTransaction &TPT) 1539 : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM), 1540 InsertedTruncs(InsertedTruncs), PromotedInsts(PromotedInsts), TPT(TPT) { 1541 IgnoreProfitability = false; 1542 } 1543public: 1544 1545 /// Match - Find the maximal addressing mode that a load/store of V can fold, 1546 /// give an access type of AccessTy. This returns a list of involved 1547 /// instructions in AddrModeInsts. 1548 /// \p InsertedTruncs The truncate instruction inserted by other 1549 /// CodeGenPrepare 1550 /// optimizations. 1551 /// \p PromotedInsts maps the instructions to their type before promotion. 1552 /// \p The ongoing transaction where every action should be registered. 1553 static ExtAddrMode Match(Value *V, Type *AccessTy, 1554 Instruction *MemoryInst, 1555 SmallVectorImpl<Instruction*> &AddrModeInsts, 1556 const TargetLowering &TLI, 1557 const SetOfInstrs &InsertedTruncs, 1558 InstrToOrigTy &PromotedInsts, 1559 TypePromotionTransaction &TPT) { 1560 ExtAddrMode Result; 1561 1562 bool Success = AddressingModeMatcher(AddrModeInsts, TLI, AccessTy, 1563 MemoryInst, Result, InsertedTruncs, 1564 PromotedInsts, TPT).MatchAddr(V, 0); 1565 (void)Success; assert(Success && "Couldn't select *anything*?"); 1566 return Result; 1567 } 1568private: 1569 bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth); 1570 bool MatchAddr(Value *V, unsigned Depth); 1571 bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth, 1572 bool *MovedAway = nullptr); 1573 bool IsProfitableToFoldIntoAddressingMode(Instruction *I, 1574 ExtAddrMode &AMBefore, 1575 ExtAddrMode &AMAfter); 1576 bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2); 1577 bool IsPromotionProfitable(unsigned MatchedSize, unsigned SizeWithPromotion, 1578 Value *PromotedOperand) const; 1579}; 1580 1581/// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode. 1582/// Return true and update AddrMode if this addr mode is legal for the target, 1583/// false if not. 1584bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale, 1585 unsigned Depth) { 1586 // If Scale is 1, then this is the same as adding ScaleReg to the addressing 1587 // mode. Just process that directly. 1588 if (Scale == 1) 1589 return MatchAddr(ScaleReg, Depth); 1590 1591 // If the scale is 0, it takes nothing to add this. 1592 if (Scale == 0) 1593 return true; 1594 1595 // If we already have a scale of this value, we can add to it, otherwise, we 1596 // need an available scale field. 1597 if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg) 1598 return false; 1599 1600 ExtAddrMode TestAddrMode = AddrMode; 1601 1602 // Add scale to turn X*4+X*3 -> X*7. This could also do things like 1603 // [A+B + A*7] -> [B+A*8]. 1604 TestAddrMode.Scale += Scale; 1605 TestAddrMode.ScaledReg = ScaleReg; 1606 1607 // If the new address isn't legal, bail out. 1608 if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) 1609 return false; 1610 1611 // It was legal, so commit it. 1612 AddrMode = TestAddrMode; 1613 1614 // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now 1615 // to see if ScaleReg is actually X+C. If so, we can turn this into adding 1616 // X*Scale + C*Scale to addr mode. 1617 ConstantInt *CI = nullptr; Value *AddLHS = nullptr; 1618 if (isa<Instruction>(ScaleReg) && // not a constant expr. 1619 match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) { 1620 TestAddrMode.ScaledReg = AddLHS; 1621 TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale; 1622 1623 // If this addressing mode is legal, commit it and remember that we folded 1624 // this instruction. 1625 if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) { 1626 AddrModeInsts.push_back(cast<Instruction>(ScaleReg)); 1627 AddrMode = TestAddrMode; 1628 return true; 1629 } 1630 } 1631 1632 // Otherwise, not (x+c)*scale, just return what we have. 1633 return true; 1634} 1635 1636/// MightBeFoldableInst - This is a little filter, which returns true if an 1637/// addressing computation involving I might be folded into a load/store 1638/// accessing it. This doesn't need to be perfect, but needs to accept at least 1639/// the set of instructions that MatchOperationAddr can. 1640static bool MightBeFoldableInst(Instruction *I) { 1641 switch (I->getOpcode()) { 1642 case Instruction::BitCast: 1643 case Instruction::AddrSpaceCast: 1644 // Don't touch identity bitcasts. 1645 if (I->getType() == I->getOperand(0)->getType()) 1646 return false; 1647 return I->getType()->isPointerTy() || I->getType()->isIntegerTy(); 1648 case Instruction::PtrToInt: 1649 // PtrToInt is always a noop, as we know that the int type is pointer sized. 1650 return true; 1651 case Instruction::IntToPtr: 1652 // We know the input is intptr_t, so this is foldable. 1653 return true; 1654 case Instruction::Add: 1655 return true; 1656 case Instruction::Mul: 1657 case Instruction::Shl: 1658 // Can only handle X*C and X << C. 1659 return isa<ConstantInt>(I->getOperand(1)); 1660 case Instruction::GetElementPtr: 1661 return true; 1662 default: 1663 return false; 1664 } 1665} 1666 1667/// \brief Hepler class to perform type promotion. 1668class TypePromotionHelper { 1669 /// \brief Utility function to check whether or not a sign extension of 1670 /// \p Inst with \p ConsideredSExtType can be moved through \p Inst by either 1671 /// using the operands of \p Inst or promoting \p Inst. 1672 /// In other words, check if: 1673 /// sext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredSExtType. 1674 /// #1 Promotion applies: 1675 /// ConsideredSExtType Inst (sext opnd1 to ConsideredSExtType, ...). 1676 /// #2 Operand reuses: 1677 /// sext opnd1 to ConsideredSExtType. 1678 /// \p PromotedInsts maps the instructions to their type before promotion. 1679 static bool canGetThrough(const Instruction *Inst, Type *ConsideredSExtType, 1680 const InstrToOrigTy &PromotedInsts); 1681 1682 /// \brief Utility function to determine if \p OpIdx should be promoted when 1683 /// promoting \p Inst. 1684 static bool shouldSExtOperand(const Instruction *Inst, int OpIdx) { 1685 if (isa<SelectInst>(Inst) && OpIdx == 0) 1686 return false; 1687 return true; 1688 } 1689 1690 /// \brief Utility function to promote the operand of \p SExt when this 1691 /// operand is a promotable trunc or sext. 1692 /// \p PromotedInsts maps the instructions to their type before promotion. 1693 /// \p CreatedInsts[out] contains how many non-free instructions have been 1694 /// created to promote the operand of SExt. 1695 /// Should never be called directly. 1696 /// \return The promoted value which is used instead of SExt. 1697 static Value *promoteOperandForTruncAndSExt(Instruction *SExt, 1698 TypePromotionTransaction &TPT, 1699 InstrToOrigTy &PromotedInsts, 1700 unsigned &CreatedInsts); 1701 1702 /// \brief Utility function to promote the operand of \p SExt when this 1703 /// operand is promotable and is not a supported trunc or sext. 1704 /// \p PromotedInsts maps the instructions to their type before promotion. 1705 /// \p CreatedInsts[out] contains how many non-free instructions have been 1706 /// created to promote the operand of SExt. 1707 /// Should never be called directly. 1708 /// \return The promoted value which is used instead of SExt. 1709 static Value *promoteOperandForOther(Instruction *SExt, 1710 TypePromotionTransaction &TPT, 1711 InstrToOrigTy &PromotedInsts, 1712 unsigned &CreatedInsts); 1713 1714public: 1715 /// Type for the utility function that promotes the operand of SExt. 1716 typedef Value *(*Action)(Instruction *SExt, TypePromotionTransaction &TPT, 1717 InstrToOrigTy &PromotedInsts, 1718 unsigned &CreatedInsts); 1719 /// \brief Given a sign extend instruction \p SExt, return the approriate 1720 /// action to promote the operand of \p SExt instead of using SExt. 1721 /// \return NULL if no promotable action is possible with the current 1722 /// sign extension. 1723 /// \p InsertedTruncs keeps track of all the truncate instructions inserted by 1724 /// the others CodeGenPrepare optimizations. This information is important 1725 /// because we do not want to promote these instructions as CodeGenPrepare 1726 /// will reinsert them later. Thus creating an infinite loop: create/remove. 1727 /// \p PromotedInsts maps the instructions to their type before promotion. 1728 static Action getAction(Instruction *SExt, const SetOfInstrs &InsertedTruncs, 1729 const TargetLowering &TLI, 1730 const InstrToOrigTy &PromotedInsts); 1731}; 1732 1733bool TypePromotionHelper::canGetThrough(const Instruction *Inst, 1734 Type *ConsideredSExtType, 1735 const InstrToOrigTy &PromotedInsts) { 1736 // We can always get through sext. 1737 if (isa<SExtInst>(Inst)) 1738 return true; 1739 1740 // We can get through binary operator, if it is legal. In other words, the 1741 // binary operator must have a nuw or nsw flag. 1742 const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst); 1743 if (BinOp && isa<OverflowingBinaryOperator>(BinOp) && 1744 (BinOp->hasNoUnsignedWrap() || BinOp->hasNoSignedWrap())) 1745 return true; 1746 1747 // Check if we can do the following simplification. 1748 // sext(trunc(sext)) --> sext 1749 if (!isa<TruncInst>(Inst)) 1750 return false; 1751 1752 Value *OpndVal = Inst->getOperand(0); 1753 // Check if we can use this operand in the sext. 1754 // If the type is larger than the result type of the sign extension, 1755 // we cannot. 1756 if (OpndVal->getType()->getIntegerBitWidth() > 1757 ConsideredSExtType->getIntegerBitWidth()) 1758 return false; 1759 1760 // If the operand of the truncate is not an instruction, we will not have 1761 // any information on the dropped bits. 1762 // (Actually we could for constant but it is not worth the extra logic). 1763 Instruction *Opnd = dyn_cast<Instruction>(OpndVal); 1764 if (!Opnd) 1765 return false; 1766 1767 // Check if the source of the type is narrow enough. 1768 // I.e., check that trunc just drops sign extended bits. 1769 // #1 get the type of the operand. 1770 const Type *OpndType; 1771 InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd); 1772 if (It != PromotedInsts.end()) 1773 OpndType = It->second; 1774 else if (isa<SExtInst>(Opnd)) 1775 OpndType = cast<Instruction>(Opnd)->getOperand(0)->getType(); 1776 else 1777 return false; 1778 1779 // #2 check that the truncate just drop sign extended bits. 1780 if (Inst->getType()->getIntegerBitWidth() >= OpndType->getIntegerBitWidth()) 1781 return true; 1782 1783 return false; 1784} 1785 1786TypePromotionHelper::Action TypePromotionHelper::getAction( 1787 Instruction *SExt, const SetOfInstrs &InsertedTruncs, 1788 const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) { 1789 Instruction *SExtOpnd = dyn_cast<Instruction>(SExt->getOperand(0)); 1790 Type *SExtTy = SExt->getType(); 1791 // If the operand of the sign extension is not an instruction, we cannot 1792 // get through. 1793 // If it, check we can get through. 1794 if (!SExtOpnd || !canGetThrough(SExtOpnd, SExtTy, PromotedInsts)) 1795 return nullptr; 1796 1797 // Do not promote if the operand has been added by codegenprepare. 1798 // Otherwise, it means we are undoing an optimization that is likely to be 1799 // redone, thus causing potential infinite loop. 1800 if (isa<TruncInst>(SExtOpnd) && InsertedTruncs.count(SExtOpnd)) 1801 return nullptr; 1802 1803 // SExt or Trunc instructions. 1804 // Return the related handler. 1805 if (isa<SExtInst>(SExtOpnd) || isa<TruncInst>(SExtOpnd)) 1806 return promoteOperandForTruncAndSExt; 1807 1808 // Regular instruction. 1809 // Abort early if we will have to insert non-free instructions. 1810 if (!SExtOpnd->hasOneUse() && 1811 !TLI.isTruncateFree(SExtTy, SExtOpnd->getType())) 1812 return nullptr; 1813 return promoteOperandForOther; 1814} 1815 1816Value *TypePromotionHelper::promoteOperandForTruncAndSExt( 1817 llvm::Instruction *SExt, TypePromotionTransaction &TPT, 1818 InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts) { 1819 // By construction, the operand of SExt is an instruction. Otherwise we cannot 1820 // get through it and this method should not be called. 1821 Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0)); 1822 // Replace sext(trunc(opnd)) or sext(sext(opnd)) 1823 // => sext(opnd). 1824 TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0)); 1825 CreatedInsts = 0; 1826 1827 // Remove dead code. 1828 if (SExtOpnd->use_empty()) 1829 TPT.eraseInstruction(SExtOpnd); 1830 1831 // Check if the sext is still needed. 1832 if (SExt->getType() != SExt->getOperand(0)->getType()) 1833 return SExt; 1834 1835 // At this point we have: sext ty opnd to ty. 1836 // Reassign the uses of SExt to the opnd and remove SExt. 1837 Value *NextVal = SExt->getOperand(0); 1838 TPT.eraseInstruction(SExt, NextVal); 1839 return NextVal; 1840} 1841 1842Value * 1843TypePromotionHelper::promoteOperandForOther(Instruction *SExt, 1844 TypePromotionTransaction &TPT, 1845 InstrToOrigTy &PromotedInsts, 1846 unsigned &CreatedInsts) { 1847 // By construction, the operand of SExt is an instruction. Otherwise we cannot 1848 // get through it and this method should not be called. 1849 Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0)); 1850 CreatedInsts = 0; 1851 if (!SExtOpnd->hasOneUse()) { 1852 // SExtOpnd will be promoted. 1853 // All its uses, but SExt, will need to use a truncated value of the 1854 // promoted version. 1855 // Create the truncate now. 1856 Instruction *Trunc = TPT.createTrunc(SExt, SExtOpnd->getType()); 1857 Trunc->removeFromParent(); 1858 // Insert it just after the definition. 1859 Trunc->insertAfter(SExtOpnd); 1860 1861 TPT.replaceAllUsesWith(SExtOpnd, Trunc); 1862 // Restore the operand of SExt (which has been replace by the previous call 1863 // to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext. 1864 TPT.setOperand(SExt, 0, SExtOpnd); 1865 } 1866 1867 // Get through the Instruction: 1868 // 1. Update its type. 1869 // 2. Replace the uses of SExt by Inst. 1870 // 3. Sign extend each operand that needs to be sign extended. 1871 1872 // Remember the original type of the instruction before promotion. 1873 // This is useful to know that the high bits are sign extended bits. 1874 PromotedInsts.insert( 1875 std::pair<Instruction *, Type *>(SExtOpnd, SExtOpnd->getType())); 1876 // Step #1. 1877 TPT.mutateType(SExtOpnd, SExt->getType()); 1878 // Step #2. 1879 TPT.replaceAllUsesWith(SExt, SExtOpnd); 1880 // Step #3. 1881 Instruction *SExtForOpnd = SExt; 1882 1883 DEBUG(dbgs() << "Propagate SExt to operands\n"); 1884 for (int OpIdx = 0, EndOpIdx = SExtOpnd->getNumOperands(); OpIdx != EndOpIdx; 1885 ++OpIdx) { 1886 DEBUG(dbgs() << "Operand:\n" << *(SExtOpnd->getOperand(OpIdx)) << '\n'); 1887 if (SExtOpnd->getOperand(OpIdx)->getType() == SExt->getType() || 1888 !shouldSExtOperand(SExtOpnd, OpIdx)) { 1889 DEBUG(dbgs() << "No need to propagate\n"); 1890 continue; 1891 } 1892 // Check if we can statically sign extend the operand. 1893 Value *Opnd = SExtOpnd->getOperand(OpIdx); 1894 if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) { 1895 DEBUG(dbgs() << "Statically sign extend\n"); 1896 TPT.setOperand( 1897 SExtOpnd, OpIdx, 1898 ConstantInt::getSigned(SExt->getType(), Cst->getSExtValue())); 1899 continue; 1900 } 1901 // UndefValue are typed, so we have to statically sign extend them. 1902 if (isa<UndefValue>(Opnd)) { 1903 DEBUG(dbgs() << "Statically sign extend\n"); 1904 TPT.setOperand(SExtOpnd, OpIdx, UndefValue::get(SExt->getType())); 1905 continue; 1906 } 1907 1908 // Otherwise we have to explicity sign extend the operand. 1909 // Check if SExt was reused to sign extend an operand. 1910 if (!SExtForOpnd) { 1911 // If yes, create a new one. 1912 DEBUG(dbgs() << "More operands to sext\n"); 1913 SExtForOpnd = TPT.createSExt(SExt, Opnd, SExt->getType()); 1914 ++CreatedInsts; 1915 } 1916 1917 TPT.setOperand(SExtForOpnd, 0, Opnd); 1918 1919 // Move the sign extension before the insertion point. 1920 TPT.moveBefore(SExtForOpnd, SExtOpnd); 1921 TPT.setOperand(SExtOpnd, OpIdx, SExtForOpnd); 1922 // If more sext are required, new instructions will have to be created. 1923 SExtForOpnd = nullptr; 1924 } 1925 if (SExtForOpnd == SExt) { 1926 DEBUG(dbgs() << "Sign extension is useless now\n"); 1927 TPT.eraseInstruction(SExt); 1928 } 1929 return SExtOpnd; 1930} 1931 1932/// IsPromotionProfitable - Check whether or not promoting an instruction 1933/// to a wider type was profitable. 1934/// \p MatchedSize gives the number of instructions that have been matched 1935/// in the addressing mode after the promotion was applied. 1936/// \p SizeWithPromotion gives the number of created instructions for 1937/// the promotion plus the number of instructions that have been 1938/// matched in the addressing mode before the promotion. 1939/// \p PromotedOperand is the value that has been promoted. 1940/// \return True if the promotion is profitable, false otherwise. 1941bool 1942AddressingModeMatcher::IsPromotionProfitable(unsigned MatchedSize, 1943 unsigned SizeWithPromotion, 1944 Value *PromotedOperand) const { 1945 // We folded less instructions than what we created to promote the operand. 1946 // This is not profitable. 1947 if (MatchedSize < SizeWithPromotion) 1948 return false; 1949 if (MatchedSize > SizeWithPromotion) 1950 return true; 1951 // The promotion is neutral but it may help folding the sign extension in 1952 // loads for instance. 1953 // Check that we did not create an illegal instruction. 1954 Instruction *PromotedInst = dyn_cast<Instruction>(PromotedOperand); 1955 if (!PromotedInst) 1956 return false; 1957 int ISDOpcode = TLI.InstructionOpcodeToISD(PromotedInst->getOpcode()); 1958 // If the ISDOpcode is undefined, it was undefined before the promotion. 1959 if (!ISDOpcode) 1960 return true; 1961 // Otherwise, check if the promoted instruction is legal or not. 1962 return TLI.isOperationLegalOrCustom(ISDOpcode, 1963 EVT::getEVT(PromotedInst->getType())); 1964} 1965 1966/// MatchOperationAddr - Given an instruction or constant expr, see if we can 1967/// fold the operation into the addressing mode. If so, update the addressing 1968/// mode and return true, otherwise return false without modifying AddrMode. 1969/// If \p MovedAway is not NULL, it contains the information of whether or 1970/// not AddrInst has to be folded into the addressing mode on success. 1971/// If \p MovedAway == true, \p AddrInst will not be part of the addressing 1972/// because it has been moved away. 1973/// Thus AddrInst must not be added in the matched instructions. 1974/// This state can happen when AddrInst is a sext, since it may be moved away. 1975/// Therefore, AddrInst may not be valid when MovedAway is true and it must 1976/// not be referenced anymore. 1977bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode, 1978 unsigned Depth, 1979 bool *MovedAway) { 1980 // Avoid exponential behavior on extremely deep expression trees. 1981 if (Depth >= 5) return false; 1982 1983 // By default, all matched instructions stay in place. 1984 if (MovedAway) 1985 *MovedAway = false; 1986 1987 switch (Opcode) { 1988 case Instruction::PtrToInt: 1989 // PtrToInt is always a noop, as we know that the int type is pointer sized. 1990 return MatchAddr(AddrInst->getOperand(0), Depth); 1991 case Instruction::IntToPtr: 1992 // This inttoptr is a no-op if the integer type is pointer sized. 1993 if (TLI.getValueType(AddrInst->getOperand(0)->getType()) == 1994 TLI.getPointerTy(AddrInst->getType()->getPointerAddressSpace())) 1995 return MatchAddr(AddrInst->getOperand(0), Depth); 1996 return false; 1997 case Instruction::BitCast: 1998 case Instruction::AddrSpaceCast: 1999 // BitCast is always a noop, and we can handle it as long as it is 2000 // int->int or pointer->pointer (we don't want int<->fp or something). 2001 if ((AddrInst->getOperand(0)->getType()->isPointerTy() || 2002 AddrInst->getOperand(0)->getType()->isIntegerTy()) && 2003 // Don't touch identity bitcasts. These were probably put here by LSR, 2004 // and we don't want to mess around with them. Assume it knows what it 2005 // is doing. 2006 AddrInst->getOperand(0)->getType() != AddrInst->getType()) 2007 return MatchAddr(AddrInst->getOperand(0), Depth); 2008 return false; 2009 case Instruction::Add: { 2010 // Check to see if we can merge in the RHS then the LHS. If so, we win. 2011 ExtAddrMode BackupAddrMode = AddrMode; 2012 unsigned OldSize = AddrModeInsts.size(); 2013 // Start a transaction at this point. 2014 // The LHS may match but not the RHS. 2015 // Therefore, we need a higher level restoration point to undo partially 2016 // matched operation. 2017 TypePromotionTransaction::ConstRestorationPt LastKnownGood = 2018 TPT.getRestorationPoint(); 2019 2020 if (MatchAddr(AddrInst->getOperand(1), Depth+1) && 2021 MatchAddr(AddrInst->getOperand(0), Depth+1)) 2022 return true; 2023 2024 // Restore the old addr mode info. 2025 AddrMode = BackupAddrMode; 2026 AddrModeInsts.resize(OldSize); 2027 TPT.rollback(LastKnownGood); 2028 2029 // Otherwise this was over-aggressive. Try merging in the LHS then the RHS. 2030 if (MatchAddr(AddrInst->getOperand(0), Depth+1) && 2031 MatchAddr(AddrInst->getOperand(1), Depth+1)) 2032 return true; 2033 2034 // Otherwise we definitely can't merge the ADD in. 2035 AddrMode = BackupAddrMode; 2036 AddrModeInsts.resize(OldSize); 2037 TPT.rollback(LastKnownGood); 2038 break; 2039 } 2040 //case Instruction::Or: 2041 // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD. 2042 //break; 2043 case Instruction::Mul: 2044 case Instruction::Shl: { 2045 // Can only handle X*C and X << C. 2046 ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1)); 2047 if (!RHS) return false; 2048 int64_t Scale = RHS->getSExtValue(); 2049 if (Opcode == Instruction::Shl) 2050 Scale = 1LL << Scale; 2051 2052 return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth); 2053 } 2054 case Instruction::GetElementPtr: { 2055 // Scan the GEP. We check it if it contains constant offsets and at most 2056 // one variable offset. 2057 int VariableOperand = -1; 2058 unsigned VariableScale = 0; 2059 2060 int64_t ConstantOffset = 0; 2061 const DataLayout *TD = TLI.getDataLayout(); 2062 gep_type_iterator GTI = gep_type_begin(AddrInst); 2063 for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) { 2064 if (StructType *STy = dyn_cast<StructType>(*GTI)) { 2065 const StructLayout *SL = TD->getStructLayout(STy); 2066 unsigned Idx = 2067 cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue(); 2068 ConstantOffset += SL->getElementOffset(Idx); 2069 } else { 2070 uint64_t TypeSize = TD->getTypeAllocSize(GTI.getIndexedType()); 2071 if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) { 2072 ConstantOffset += CI->getSExtValue()*TypeSize; 2073 } else if (TypeSize) { // Scales of zero don't do anything. 2074 // We only allow one variable index at the moment. 2075 if (VariableOperand != -1) 2076 return false; 2077 2078 // Remember the variable index. 2079 VariableOperand = i; 2080 VariableScale = TypeSize; 2081 } 2082 } 2083 } 2084 2085 // A common case is for the GEP to only do a constant offset. In this case, 2086 // just add it to the disp field and check validity. 2087 if (VariableOperand == -1) { 2088 AddrMode.BaseOffs += ConstantOffset; 2089 if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){ 2090 // Check to see if we can fold the base pointer in too. 2091 if (MatchAddr(AddrInst->getOperand(0), Depth+1)) 2092 return true; 2093 } 2094 AddrMode.BaseOffs -= ConstantOffset; 2095 return false; 2096 } 2097 2098 // Save the valid addressing mode in case we can't match. 2099 ExtAddrMode BackupAddrMode = AddrMode; 2100 unsigned OldSize = AddrModeInsts.size(); 2101 2102 // See if the scale and offset amount is valid for this target. 2103 AddrMode.BaseOffs += ConstantOffset; 2104 2105 // Match the base operand of the GEP. 2106 if (!MatchAddr(AddrInst->getOperand(0), Depth+1)) { 2107 // If it couldn't be matched, just stuff the value in a register. 2108 if (AddrMode.HasBaseReg) { 2109 AddrMode = BackupAddrMode; 2110 AddrModeInsts.resize(OldSize); 2111 return false; 2112 } 2113 AddrMode.HasBaseReg = true; 2114 AddrMode.BaseReg = AddrInst->getOperand(0); 2115 } 2116 2117 // Match the remaining variable portion of the GEP. 2118 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale, 2119 Depth)) { 2120 // If it couldn't be matched, try stuffing the base into a register 2121 // instead of matching it, and retrying the match of the scale. 2122 AddrMode = BackupAddrMode; 2123 AddrModeInsts.resize(OldSize); 2124 if (AddrMode.HasBaseReg) 2125 return false; 2126 AddrMode.HasBaseReg = true; 2127 AddrMode.BaseReg = AddrInst->getOperand(0); 2128 AddrMode.BaseOffs += ConstantOffset; 2129 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), 2130 VariableScale, Depth)) { 2131 // If even that didn't work, bail. 2132 AddrMode = BackupAddrMode; 2133 AddrModeInsts.resize(OldSize); 2134 return false; 2135 } 2136 } 2137 2138 return true; 2139 } 2140 case Instruction::SExt: { 2141 // Try to move this sext out of the way of the addressing mode. 2142 Instruction *SExt = cast<Instruction>(AddrInst); 2143 // Ask for a method for doing so. 2144 TypePromotionHelper::Action TPH = TypePromotionHelper::getAction( 2145 SExt, InsertedTruncs, TLI, PromotedInsts); 2146 if (!TPH) 2147 return false; 2148 2149 TypePromotionTransaction::ConstRestorationPt LastKnownGood = 2150 TPT.getRestorationPoint(); 2151 unsigned CreatedInsts = 0; 2152 Value *PromotedOperand = TPH(SExt, TPT, PromotedInsts, CreatedInsts); 2153 // SExt has been moved away. 2154 // Thus either it will be rematched later in the recursive calls or it is 2155 // gone. Anyway, we must not fold it into the addressing mode at this point. 2156 // E.g., 2157 // op = add opnd, 1 2158 // idx = sext op 2159 // addr = gep base, idx 2160 // is now: 2161 // promotedOpnd = sext opnd <- no match here 2162 // op = promoted_add promotedOpnd, 1 <- match (later in recursive calls) 2163 // addr = gep base, op <- match 2164 if (MovedAway) 2165 *MovedAway = true; 2166 2167 assert(PromotedOperand && 2168 "TypePromotionHelper should have filtered out those cases"); 2169 2170 ExtAddrMode BackupAddrMode = AddrMode; 2171 unsigned OldSize = AddrModeInsts.size(); 2172 2173 if (!MatchAddr(PromotedOperand, Depth) || 2174 !IsPromotionProfitable(AddrModeInsts.size(), OldSize + CreatedInsts, 2175 PromotedOperand)) { 2176 AddrMode = BackupAddrMode; 2177 AddrModeInsts.resize(OldSize); 2178 DEBUG(dbgs() << "Sign extension does not pay off: rollback\n"); 2179 TPT.rollback(LastKnownGood); 2180 return false; 2181 } 2182 return true; 2183 } 2184 } 2185 return false; 2186} 2187 2188/// MatchAddr - If we can, try to add the value of 'Addr' into the current 2189/// addressing mode. If Addr can't be added to AddrMode this returns false and 2190/// leaves AddrMode unmodified. This assumes that Addr is either a pointer type 2191/// or intptr_t for the target. 2192/// 2193bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) { 2194 // Start a transaction at this point that we will rollback if the matching 2195 // fails. 2196 TypePromotionTransaction::ConstRestorationPt LastKnownGood = 2197 TPT.getRestorationPoint(); 2198 if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) { 2199 // Fold in immediates if legal for the target. 2200 AddrMode.BaseOffs += CI->getSExtValue(); 2201 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) 2202 return true; 2203 AddrMode.BaseOffs -= CI->getSExtValue(); 2204 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) { 2205 // If this is a global variable, try to fold it into the addressing mode. 2206 if (!AddrMode.BaseGV) { 2207 AddrMode.BaseGV = GV; 2208 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) 2209 return true; 2210 AddrMode.BaseGV = nullptr; 2211 } 2212 } else if (Instruction *I = dyn_cast<Instruction>(Addr)) { 2213 ExtAddrMode BackupAddrMode = AddrMode; 2214 unsigned OldSize = AddrModeInsts.size(); 2215 2216 // Check to see if it is possible to fold this operation. 2217 bool MovedAway = false; 2218 if (MatchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) { 2219 // This instruction may have been move away. If so, there is nothing 2220 // to check here. 2221 if (MovedAway) 2222 return true; 2223 // Okay, it's possible to fold this. Check to see if it is actually 2224 // *profitable* to do so. We use a simple cost model to avoid increasing 2225 // register pressure too much. 2226 if (I->hasOneUse() || 2227 IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) { 2228 AddrModeInsts.push_back(I); 2229 return true; 2230 } 2231 2232 // It isn't profitable to do this, roll back. 2233 //cerr << "NOT FOLDING: " << *I; 2234 AddrMode = BackupAddrMode; 2235 AddrModeInsts.resize(OldSize); 2236 TPT.rollback(LastKnownGood); 2237 } 2238 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) { 2239 if (MatchOperationAddr(CE, CE->getOpcode(), Depth)) 2240 return true; 2241 TPT.rollback(LastKnownGood); 2242 } else if (isa<ConstantPointerNull>(Addr)) { 2243 // Null pointer gets folded without affecting the addressing mode. 2244 return true; 2245 } 2246 2247 // Worse case, the target should support [reg] addressing modes. :) 2248 if (!AddrMode.HasBaseReg) { 2249 AddrMode.HasBaseReg = true; 2250 AddrMode.BaseReg = Addr; 2251 // Still check for legality in case the target supports [imm] but not [i+r]. 2252 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) 2253 return true; 2254 AddrMode.HasBaseReg = false; 2255 AddrMode.BaseReg = nullptr; 2256 } 2257 2258 // If the base register is already taken, see if we can do [r+r]. 2259 if (AddrMode.Scale == 0) { 2260 AddrMode.Scale = 1; 2261 AddrMode.ScaledReg = Addr; 2262 if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) 2263 return true; 2264 AddrMode.Scale = 0; 2265 AddrMode.ScaledReg = nullptr; 2266 } 2267 // Couldn't match. 2268 TPT.rollback(LastKnownGood); 2269 return false; 2270} 2271 2272/// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified 2273/// inline asm call are due to memory operands. If so, return true, otherwise 2274/// return false. 2275static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal, 2276 const TargetLowering &TLI) { 2277 TargetLowering::AsmOperandInfoVector TargetConstraints = TLI.ParseConstraints(ImmutableCallSite(CI)); 2278 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) { 2279 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i]; 2280 2281 // Compute the constraint code and ConstraintType to use. 2282 TLI.ComputeConstraintToUse(OpInfo, SDValue()); 2283 2284 // If this asm operand is our Value*, and if it isn't an indirect memory 2285 // operand, we can't fold it! 2286 if (OpInfo.CallOperandVal == OpVal && 2287 (OpInfo.ConstraintType != TargetLowering::C_Memory || 2288 !OpInfo.isIndirect)) 2289 return false; 2290 } 2291 2292 return true; 2293} 2294 2295/// FindAllMemoryUses - Recursively walk all the uses of I until we find a 2296/// memory use. If we find an obviously non-foldable instruction, return true. 2297/// Add the ultimately found memory instructions to MemoryUses. 2298static bool FindAllMemoryUses(Instruction *I, 2299 SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses, 2300 SmallPtrSet<Instruction*, 16> &ConsideredInsts, 2301 const TargetLowering &TLI) { 2302 // If we already considered this instruction, we're done. 2303 if (!ConsideredInsts.insert(I)) 2304 return false; 2305 2306 // If this is an obviously unfoldable instruction, bail out. 2307 if (!MightBeFoldableInst(I)) 2308 return true; 2309 2310 // Loop over all the uses, recursively processing them. 2311 for (Use &U : I->uses()) { 2312 Instruction *UserI = cast<Instruction>(U.getUser()); 2313 2314 if (LoadInst *LI = dyn_cast<LoadInst>(UserI)) { 2315 MemoryUses.push_back(std::make_pair(LI, U.getOperandNo())); 2316 continue; 2317 } 2318 2319 if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) { 2320 unsigned opNo = U.getOperandNo(); 2321 if (opNo == 0) return true; // Storing addr, not into addr. 2322 MemoryUses.push_back(std::make_pair(SI, opNo)); 2323 continue; 2324 } 2325 2326 if (CallInst *CI = dyn_cast<CallInst>(UserI)) { 2327 InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue()); 2328 if (!IA) return true; 2329 2330 // If this is a memory operand, we're cool, otherwise bail out. 2331 if (!IsOperandAMemoryOperand(CI, IA, I, TLI)) 2332 return true; 2333 continue; 2334 } 2335 2336 if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI)) 2337 return true; 2338 } 2339 2340 return false; 2341} 2342 2343/// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at 2344/// the use site that we're folding it into. If so, there is no cost to 2345/// include it in the addressing mode. KnownLive1 and KnownLive2 are two values 2346/// that we know are live at the instruction already. 2347bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1, 2348 Value *KnownLive2) { 2349 // If Val is either of the known-live values, we know it is live! 2350 if (Val == nullptr || Val == KnownLive1 || Val == KnownLive2) 2351 return true; 2352 2353 // All values other than instructions and arguments (e.g. constants) are live. 2354 if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true; 2355 2356 // If Val is a constant sized alloca in the entry block, it is live, this is 2357 // true because it is just a reference to the stack/frame pointer, which is 2358 // live for the whole function. 2359 if (AllocaInst *AI = dyn_cast<AllocaInst>(Val)) 2360 if (AI->isStaticAlloca()) 2361 return true; 2362 2363 // Check to see if this value is already used in the memory instruction's 2364 // block. If so, it's already live into the block at the very least, so we 2365 // can reasonably fold it. 2366 return Val->isUsedInBasicBlock(MemoryInst->getParent()); 2367} 2368 2369/// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing 2370/// mode of the machine to fold the specified instruction into a load or store 2371/// that ultimately uses it. However, the specified instruction has multiple 2372/// uses. Given this, it may actually increase register pressure to fold it 2373/// into the load. For example, consider this code: 2374/// 2375/// X = ... 2376/// Y = X+1 2377/// use(Y) -> nonload/store 2378/// Z = Y+1 2379/// load Z 2380/// 2381/// In this case, Y has multiple uses, and can be folded into the load of Z 2382/// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to 2383/// be live at the use(Y) line. If we don't fold Y into load Z, we use one 2384/// fewer register. Since Y can't be folded into "use(Y)" we don't increase the 2385/// number of computations either. 2386/// 2387/// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If 2388/// X was live across 'load Z' for other reasons, we actually *would* want to 2389/// fold the addressing mode in the Z case. This would make Y die earlier. 2390bool AddressingModeMatcher:: 2391IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore, 2392 ExtAddrMode &AMAfter) { 2393 if (IgnoreProfitability) return true; 2394 2395 // AMBefore is the addressing mode before this instruction was folded into it, 2396 // and AMAfter is the addressing mode after the instruction was folded. Get 2397 // the set of registers referenced by AMAfter and subtract out those 2398 // referenced by AMBefore: this is the set of values which folding in this 2399 // address extends the lifetime of. 2400 // 2401 // Note that there are only two potential values being referenced here, 2402 // BaseReg and ScaleReg (global addresses are always available, as are any 2403 // folded immediates). 2404 Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg; 2405 2406 // If the BaseReg or ScaledReg was referenced by the previous addrmode, their 2407 // lifetime wasn't extended by adding this instruction. 2408 if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg)) 2409 BaseReg = nullptr; 2410 if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg)) 2411 ScaledReg = nullptr; 2412 2413 // If folding this instruction (and it's subexprs) didn't extend any live 2414 // ranges, we're ok with it. 2415 if (!BaseReg && !ScaledReg) 2416 return true; 2417 2418 // If all uses of this instruction are ultimately load/store/inlineasm's, 2419 // check to see if their addressing modes will include this instruction. If 2420 // so, we can fold it into all uses, so it doesn't matter if it has multiple 2421 // uses. 2422 SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses; 2423 SmallPtrSet<Instruction*, 16> ConsideredInsts; 2424 if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI)) 2425 return false; // Has a non-memory, non-foldable use! 2426 2427 // Now that we know that all uses of this instruction are part of a chain of 2428 // computation involving only operations that could theoretically be folded 2429 // into a memory use, loop over each of these uses and see if they could 2430 // *actually* fold the instruction. 2431 SmallVector<Instruction*, 32> MatchedAddrModeInsts; 2432 for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) { 2433 Instruction *User = MemoryUses[i].first; 2434 unsigned OpNo = MemoryUses[i].second; 2435 2436 // Get the access type of this use. If the use isn't a pointer, we don't 2437 // know what it accesses. 2438 Value *Address = User->getOperand(OpNo); 2439 if (!Address->getType()->isPointerTy()) 2440 return false; 2441 Type *AddressAccessTy = Address->getType()->getPointerElementType(); 2442 2443 // Do a match against the root of this address, ignoring profitability. This 2444 // will tell us if the addressing mode for the memory operation will 2445 // *actually* cover the shared instruction. 2446 ExtAddrMode Result; 2447 TypePromotionTransaction::ConstRestorationPt LastKnownGood = 2448 TPT.getRestorationPoint(); 2449 AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy, 2450 MemoryInst, Result, InsertedTruncs, 2451 PromotedInsts, TPT); 2452 Matcher.IgnoreProfitability = true; 2453 bool Success = Matcher.MatchAddr(Address, 0); 2454 (void)Success; assert(Success && "Couldn't select *anything*?"); 2455 2456 // The match was to check the profitability, the changes made are not 2457 // part of the original matcher. Therefore, they should be dropped 2458 // otherwise the original matcher will not present the right state. 2459 TPT.rollback(LastKnownGood); 2460 2461 // If the match didn't cover I, then it won't be shared by it. 2462 if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(), 2463 I) == MatchedAddrModeInsts.end()) 2464 return false; 2465 2466 MatchedAddrModeInsts.clear(); 2467 } 2468 2469 return true; 2470} 2471 2472} // end anonymous namespace 2473 2474/// IsNonLocalValue - Return true if the specified values are defined in a 2475/// different basic block than BB. 2476static bool IsNonLocalValue(Value *V, BasicBlock *BB) { 2477 if (Instruction *I = dyn_cast<Instruction>(V)) 2478 return I->getParent() != BB; 2479 return false; 2480} 2481 2482/// OptimizeMemoryInst - Load and Store Instructions often have 2483/// addressing modes that can do significant amounts of computation. As such, 2484/// instruction selection will try to get the load or store to do as much 2485/// computation as possible for the program. The problem is that isel can only 2486/// see within a single block. As such, we sink as much legal addressing mode 2487/// stuff into the block as possible. 2488/// 2489/// This method is used to optimize both load/store and inline asms with memory 2490/// operands. 2491bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr, 2492 Type *AccessTy) { 2493 Value *Repl = Addr; 2494 2495 // Try to collapse single-value PHI nodes. This is necessary to undo 2496 // unprofitable PRE transformations. 2497 SmallVector<Value*, 8> worklist; 2498 SmallPtrSet<Value*, 16> Visited; 2499 worklist.push_back(Addr); 2500 2501 // Use a worklist to iteratively look through PHI nodes, and ensure that 2502 // the addressing mode obtained from the non-PHI roots of the graph 2503 // are equivalent. 2504 Value *Consensus = nullptr; 2505 unsigned NumUsesConsensus = 0; 2506 bool IsNumUsesConsensusValid = false; 2507 SmallVector<Instruction*, 16> AddrModeInsts; 2508 ExtAddrMode AddrMode; 2509 TypePromotionTransaction TPT; 2510 TypePromotionTransaction::ConstRestorationPt LastKnownGood = 2511 TPT.getRestorationPoint(); 2512 while (!worklist.empty()) { 2513 Value *V = worklist.back(); 2514 worklist.pop_back(); 2515 2516 // Break use-def graph loops. 2517 if (!Visited.insert(V)) { 2518 Consensus = nullptr; 2519 break; 2520 } 2521 2522 // For a PHI node, push all of its incoming values. 2523 if (PHINode *P = dyn_cast<PHINode>(V)) { 2524 for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) 2525 worklist.push_back(P->getIncomingValue(i)); 2526 continue; 2527 } 2528 2529 // For non-PHIs, determine the addressing mode being computed. 2530 SmallVector<Instruction*, 16> NewAddrModeInsts; 2531 ExtAddrMode NewAddrMode = AddressingModeMatcher::Match( 2532 V, AccessTy, MemoryInst, NewAddrModeInsts, *TLI, InsertedTruncsSet, 2533 PromotedInsts, TPT); 2534 2535 // This check is broken into two cases with very similar code to avoid using 2536 // getNumUses() as much as possible. Some values have a lot of uses, so 2537 // calling getNumUses() unconditionally caused a significant compile-time 2538 // regression. 2539 if (!Consensus) { 2540 Consensus = V; 2541 AddrMode = NewAddrMode; 2542 AddrModeInsts = NewAddrModeInsts; 2543 continue; 2544 } else if (NewAddrMode == AddrMode) { 2545 if (!IsNumUsesConsensusValid) { 2546 NumUsesConsensus = Consensus->getNumUses(); 2547 IsNumUsesConsensusValid = true; 2548 } 2549 2550 // Ensure that the obtained addressing mode is equivalent to that obtained 2551 // for all other roots of the PHI traversal. Also, when choosing one 2552 // such root as representative, select the one with the most uses in order 2553 // to keep the cost modeling heuristics in AddressingModeMatcher 2554 // applicable. 2555 unsigned NumUses = V->getNumUses(); 2556 if (NumUses > NumUsesConsensus) { 2557 Consensus = V; 2558 NumUsesConsensus = NumUses; 2559 AddrModeInsts = NewAddrModeInsts; 2560 } 2561 continue; 2562 } 2563 2564 Consensus = nullptr; 2565 break; 2566 } 2567 2568 // If the addressing mode couldn't be determined, or if multiple different 2569 // ones were determined, bail out now. 2570 if (!Consensus) { 2571 TPT.rollback(LastKnownGood); 2572 return false; 2573 } 2574 TPT.commit(); 2575 2576 // Check to see if any of the instructions supersumed by this addr mode are 2577 // non-local to I's BB. 2578 bool AnyNonLocal = false; 2579 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) { 2580 if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) { 2581 AnyNonLocal = true; 2582 break; 2583 } 2584 } 2585 2586 // If all the instructions matched are already in this BB, don't do anything. 2587 if (!AnyNonLocal) { 2588 DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n"); 2589 return false; 2590 } 2591 2592 // Insert this computation right after this user. Since our caller is 2593 // scanning from the top of the BB to the bottom, reuse of the expr are 2594 // guaranteed to happen later. 2595 IRBuilder<> Builder(MemoryInst); 2596 2597 // Now that we determined the addressing expression we want to use and know 2598 // that we have to sink it into this block. Check to see if we have already 2599 // done this for some other load/store instr in this block. If so, reuse the 2600 // computation. 2601 Value *&SunkAddr = SunkAddrs[Addr]; 2602 if (SunkAddr) { 2603 DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for " 2604 << *MemoryInst << "\n"); 2605 if (SunkAddr->getType() != Addr->getType()) 2606 SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType()); 2607 } else if (AddrSinkUsingGEPs || (!AddrSinkUsingGEPs.getNumOccurrences() && 2608 TM && TM->getSubtarget<TargetSubtargetInfo>().useAA())) { 2609 // By default, we use the GEP-based method when AA is used later. This 2610 // prevents new inttoptr/ptrtoint pairs from degrading AA capabilities. 2611 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for " 2612 << *MemoryInst << "\n"); 2613 Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType()); 2614 Value *ResultPtr = nullptr, *ResultIndex = nullptr; 2615 2616 // First, find the pointer. 2617 if (AddrMode.BaseReg && AddrMode.BaseReg->getType()->isPointerTy()) { 2618 ResultPtr = AddrMode.BaseReg; 2619 AddrMode.BaseReg = nullptr; 2620 } 2621 2622 if (AddrMode.Scale && AddrMode.ScaledReg->getType()->isPointerTy()) { 2623 // We can't add more than one pointer together, nor can we scale a 2624 // pointer (both of which seem meaningless). 2625 if (ResultPtr || AddrMode.Scale != 1) 2626 return false; 2627 2628 ResultPtr = AddrMode.ScaledReg; 2629 AddrMode.Scale = 0; 2630 } 2631 2632 if (AddrMode.BaseGV) { 2633 if (ResultPtr) 2634 return false; 2635 2636 ResultPtr = AddrMode.BaseGV; 2637 } 2638 2639 // If the real base value actually came from an inttoptr, then the matcher 2640 // will look through it and provide only the integer value. In that case, 2641 // use it here. 2642 if (!ResultPtr && AddrMode.BaseReg) { 2643 ResultPtr = 2644 Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(), "sunkaddr"); 2645 AddrMode.BaseReg = nullptr; 2646 } else if (!ResultPtr && AddrMode.Scale == 1) { 2647 ResultPtr = 2648 Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(), "sunkaddr"); 2649 AddrMode.Scale = 0; 2650 } 2651 2652 if (!ResultPtr && 2653 !AddrMode.BaseReg && !AddrMode.Scale && !AddrMode.BaseOffs) { 2654 SunkAddr = Constant::getNullValue(Addr->getType()); 2655 } else if (!ResultPtr) { 2656 return false; 2657 } else { 2658 Type *I8PtrTy = 2659 Builder.getInt8PtrTy(Addr->getType()->getPointerAddressSpace()); 2660 2661 // Start with the base register. Do this first so that subsequent address 2662 // matching finds it last, which will prevent it from trying to match it 2663 // as the scaled value in case it happens to be a mul. That would be 2664 // problematic if we've sunk a different mul for the scale, because then 2665 // we'd end up sinking both muls. 2666 if (AddrMode.BaseReg) { 2667 Value *V = AddrMode.BaseReg; 2668 if (V->getType() != IntPtrTy) 2669 V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr"); 2670 2671 ResultIndex = V; 2672 } 2673 2674 // Add the scale value. 2675 if (AddrMode.Scale) { 2676 Value *V = AddrMode.ScaledReg; 2677 if (V->getType() == IntPtrTy) { 2678 // done. 2679 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() < 2680 cast<IntegerType>(V->getType())->getBitWidth()) { 2681 V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr"); 2682 } else { 2683 // It is only safe to sign extend the BaseReg if we know that the math 2684 // required to create it did not overflow before we extend it. Since 2685 // the original IR value was tossed in favor of a constant back when 2686 // the AddrMode was created we need to bail out gracefully if widths 2687 // do not match instead of extending it. 2688 Instruction *I = dyn_cast_or_null<Instruction>(ResultIndex); 2689 if (I && (ResultIndex != AddrMode.BaseReg)) 2690 I->eraseFromParent(); 2691 return false; 2692 } 2693 2694 if (AddrMode.Scale != 1) 2695 V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale), 2696 "sunkaddr"); 2697 if (ResultIndex) 2698 ResultIndex = Builder.CreateAdd(ResultIndex, V, "sunkaddr"); 2699 else 2700 ResultIndex = V; 2701 } 2702 2703 // Add in the Base Offset if present. 2704 if (AddrMode.BaseOffs) { 2705 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs); 2706 if (ResultIndex) { 2707 // We need to add this separately from the scale above to help with 2708 // SDAG consecutive load/store merging. 2709 if (ResultPtr->getType() != I8PtrTy) 2710 ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy); 2711 ResultPtr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr"); 2712 } 2713 2714 ResultIndex = V; 2715 } 2716 2717 if (!ResultIndex) { 2718 SunkAddr = ResultPtr; 2719 } else { 2720 if (ResultPtr->getType() != I8PtrTy) 2721 ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy); 2722 SunkAddr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr"); 2723 } 2724 2725 if (SunkAddr->getType() != Addr->getType()) 2726 SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType()); 2727 } 2728 } else { 2729 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for " 2730 << *MemoryInst << "\n"); 2731 Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType()); 2732 Value *Result = nullptr; 2733 2734 // Start with the base register. Do this first so that subsequent address 2735 // matching finds it last, which will prevent it from trying to match it 2736 // as the scaled value in case it happens to be a mul. That would be 2737 // problematic if we've sunk a different mul for the scale, because then 2738 // we'd end up sinking both muls. 2739 if (AddrMode.BaseReg) { 2740 Value *V = AddrMode.BaseReg; 2741 if (V->getType()->isPointerTy()) 2742 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr"); 2743 if (V->getType() != IntPtrTy) 2744 V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr"); 2745 Result = V; 2746 } 2747 2748 // Add the scale value. 2749 if (AddrMode.Scale) { 2750 Value *V = AddrMode.ScaledReg; 2751 if (V->getType() == IntPtrTy) { 2752 // done. 2753 } else if (V->getType()->isPointerTy()) { 2754 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr"); 2755 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() < 2756 cast<IntegerType>(V->getType())->getBitWidth()) { 2757 V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr"); 2758 } else { 2759 // It is only safe to sign extend the BaseReg if we know that the math 2760 // required to create it did not overflow before we extend it. Since 2761 // the original IR value was tossed in favor of a constant back when 2762 // the AddrMode was created we need to bail out gracefully if widths 2763 // do not match instead of extending it. 2764 Instruction *I = dyn_cast_or_null<Instruction>(Result); 2765 if (I && (Result != AddrMode.BaseReg)) 2766 I->eraseFromParent(); 2767 return false; 2768 } 2769 if (AddrMode.Scale != 1) 2770 V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale), 2771 "sunkaddr"); 2772 if (Result) 2773 Result = Builder.CreateAdd(Result, V, "sunkaddr"); 2774 else 2775 Result = V; 2776 } 2777 2778 // Add in the BaseGV if present. 2779 if (AddrMode.BaseGV) { 2780 Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr"); 2781 if (Result) 2782 Result = Builder.CreateAdd(Result, V, "sunkaddr"); 2783 else 2784 Result = V; 2785 } 2786 2787 // Add in the Base Offset if present. 2788 if (AddrMode.BaseOffs) { 2789 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs); 2790 if (Result) 2791 Result = Builder.CreateAdd(Result, V, "sunkaddr"); 2792 else 2793 Result = V; 2794 } 2795 2796 if (!Result) 2797 SunkAddr = Constant::getNullValue(Addr->getType()); 2798 else 2799 SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr"); 2800 } 2801 2802 MemoryInst->replaceUsesOfWith(Repl, SunkAddr); 2803 2804 // If we have no uses, recursively delete the value and all dead instructions 2805 // using it. 2806 if (Repl->use_empty()) { 2807 // This can cause recursive deletion, which can invalidate our iterator. 2808 // Use a WeakVH to hold onto it in case this happens. 2809 WeakVH IterHandle(CurInstIterator); 2810 BasicBlock *BB = CurInstIterator->getParent(); 2811 2812 RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo); 2813 2814 if (IterHandle != CurInstIterator) { 2815 // If the iterator instruction was recursively deleted, start over at the 2816 // start of the block. 2817 CurInstIterator = BB->begin(); 2818 SunkAddrs.clear(); 2819 } 2820 } 2821 ++NumMemoryInsts; 2822 return true; 2823} 2824 2825/// OptimizeInlineAsmInst - If there are any memory operands, use 2826/// OptimizeMemoryInst to sink their address computing into the block when 2827/// possible / profitable. 2828bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) { 2829 bool MadeChange = false; 2830 2831 TargetLowering::AsmOperandInfoVector 2832 TargetConstraints = TLI->ParseConstraints(CS); 2833 unsigned ArgNo = 0; 2834 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) { 2835 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i]; 2836 2837 // Compute the constraint code and ConstraintType to use. 2838 TLI->ComputeConstraintToUse(OpInfo, SDValue()); 2839 2840 if (OpInfo.ConstraintType == TargetLowering::C_Memory && 2841 OpInfo.isIndirect) { 2842 Value *OpVal = CS->getArgOperand(ArgNo++); 2843 MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType()); 2844 } else if (OpInfo.Type == InlineAsm::isInput) 2845 ArgNo++; 2846 } 2847 2848 return MadeChange; 2849} 2850 2851/// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same 2852/// basic block as the load, unless conditions are unfavorable. This allows 2853/// SelectionDAG to fold the extend into the load. 2854/// 2855bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) { 2856 // Look for a load being extended. 2857 LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0)); 2858 if (!LI) return false; 2859 2860 // If they're already in the same block, there's nothing to do. 2861 if (LI->getParent() == I->getParent()) 2862 return false; 2863 2864 // If the load has other users and the truncate is not free, this probably 2865 // isn't worthwhile. 2866 if (!LI->hasOneUse() && 2867 TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) || 2868 !TLI->isTypeLegal(TLI->getValueType(I->getType()))) && 2869 !TLI->isTruncateFree(I->getType(), LI->getType())) 2870 return false; 2871 2872 // Check whether the target supports casts folded into loads. 2873 unsigned LType; 2874 if (isa<ZExtInst>(I)) 2875 LType = ISD::ZEXTLOAD; 2876 else { 2877 assert(isa<SExtInst>(I) && "Unexpected ext type!"); 2878 LType = ISD::SEXTLOAD; 2879 } 2880 if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType()))) 2881 return false; 2882 2883 // Move the extend into the same block as the load, so that SelectionDAG 2884 // can fold it. 2885 I->removeFromParent(); 2886 I->insertAfter(LI); 2887 ++NumExtsMoved; 2888 return true; 2889} 2890 2891bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { 2892 BasicBlock *DefBB = I->getParent(); 2893 2894 // If the result of a {s|z}ext and its source are both live out, rewrite all 2895 // other uses of the source with result of extension. 2896 Value *Src = I->getOperand(0); 2897 if (Src->hasOneUse()) 2898 return false; 2899 2900 // Only do this xform if truncating is free. 2901 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType())) 2902 return false; 2903 2904 // Only safe to perform the optimization if the source is also defined in 2905 // this block. 2906 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent()) 2907 return false; 2908 2909 bool DefIsLiveOut = false; 2910 for (User *U : I->users()) { 2911 Instruction *UI = cast<Instruction>(U); 2912 2913 // Figure out which BB this ext is used in. 2914 BasicBlock *UserBB = UI->getParent(); 2915 if (UserBB == DefBB) continue; 2916 DefIsLiveOut = true; 2917 break; 2918 } 2919 if (!DefIsLiveOut) 2920 return false; 2921 2922 // Make sure none of the uses are PHI nodes. 2923 for (User *U : Src->users()) { 2924 Instruction *UI = cast<Instruction>(U); 2925 BasicBlock *UserBB = UI->getParent(); 2926 if (UserBB == DefBB) continue; 2927 // Be conservative. We don't want this xform to end up introducing 2928 // reloads just before load / store instructions. 2929 if (isa<PHINode>(UI) || isa<LoadInst>(UI) || isa<StoreInst>(UI)) 2930 return false; 2931 } 2932 2933 // InsertedTruncs - Only insert one trunc in each block once. 2934 DenseMap<BasicBlock*, Instruction*> InsertedTruncs; 2935 2936 bool MadeChange = false; 2937 for (Use &U : Src->uses()) { 2938 Instruction *User = cast<Instruction>(U.getUser()); 2939 2940 // Figure out which BB this ext is used in. 2941 BasicBlock *UserBB = User->getParent(); 2942 if (UserBB == DefBB) continue; 2943 2944 // Both src and def are live in this block. Rewrite the use. 2945 Instruction *&InsertedTrunc = InsertedTruncs[UserBB]; 2946 2947 if (!InsertedTrunc) { 2948 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); 2949 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt); 2950 InsertedTruncsSet.insert(InsertedTrunc); 2951 } 2952 2953 // Replace a use of the {s|z}ext source with a use of the result. 2954 U = InsertedTrunc; 2955 ++NumExtUses; 2956 MadeChange = true; 2957 } 2958 2959 return MadeChange; 2960} 2961 2962/// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be 2963/// turned into an explicit branch. 2964static bool isFormingBranchFromSelectProfitable(SelectInst *SI) { 2965 // FIXME: This should use the same heuristics as IfConversion to determine 2966 // whether a select is better represented as a branch. This requires that 2967 // branch probability metadata is preserved for the select, which is not the 2968 // case currently. 2969 2970 CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition()); 2971 2972 // If the branch is predicted right, an out of order CPU can avoid blocking on 2973 // the compare. Emit cmovs on compares with a memory operand as branches to 2974 // avoid stalls on the load from memory. If the compare has more than one use 2975 // there's probably another cmov or setcc around so it's not worth emitting a 2976 // branch. 2977 if (!Cmp) 2978 return false; 2979 2980 Value *CmpOp0 = Cmp->getOperand(0); 2981 Value *CmpOp1 = Cmp->getOperand(1); 2982 2983 // We check that the memory operand has one use to avoid uses of the loaded 2984 // value directly after the compare, making branches unprofitable. 2985 return Cmp->hasOneUse() && 2986 ((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) || 2987 (isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse())); 2988} 2989 2990 2991/// If we have a SelectInst that will likely profit from branch prediction, 2992/// turn it into a branch. 2993bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) { 2994 bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1); 2995 2996 // Can we convert the 'select' to CF ? 2997 if (DisableSelectToBranch || OptSize || !TLI || VectorCond) 2998 return false; 2999 3000 TargetLowering::SelectSupportKind SelectKind; 3001 if (VectorCond) 3002 SelectKind = TargetLowering::VectorMaskSelect; 3003 else if (SI->getType()->isVectorTy()) 3004 SelectKind = TargetLowering::ScalarCondVectorVal; 3005 else 3006 SelectKind = TargetLowering::ScalarValSelect; 3007 3008 // Do we have efficient codegen support for this kind of 'selects' ? 3009 if (TLI->isSelectSupported(SelectKind)) { 3010 // We have efficient codegen support for the select instruction. 3011 // Check if it is profitable to keep this 'select'. 3012 if (!TLI->isPredictableSelectExpensive() || 3013 !isFormingBranchFromSelectProfitable(SI)) 3014 return false; 3015 } 3016 3017 ModifiedDT = true; 3018 3019 // First, we split the block containing the select into 2 blocks. 3020 BasicBlock *StartBlock = SI->getParent(); 3021 BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI)); 3022 BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end"); 3023 3024 // Create a new block serving as the landing pad for the branch. 3025 BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid", 3026 NextBlock->getParent(), NextBlock); 3027 3028 // Move the unconditional branch from the block with the select in it into our 3029 // landing pad block. 3030 StartBlock->getTerminator()->eraseFromParent(); 3031 BranchInst::Create(NextBlock, SmallBlock); 3032 3033 // Insert the real conditional branch based on the original condition. 3034 BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI); 3035 3036 // The select itself is replaced with a PHI Node. 3037 PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin()); 3038 PN->takeName(SI); 3039 PN->addIncoming(SI->getTrueValue(), StartBlock); 3040 PN->addIncoming(SI->getFalseValue(), SmallBlock); 3041 SI->replaceAllUsesWith(PN); 3042 SI->eraseFromParent(); 3043 3044 // Instruct OptimizeBlock to skip to the next block. 3045 CurInstIterator = StartBlock->end(); 3046 ++NumSelectsExpanded; 3047 return true; 3048} 3049 3050static bool isBroadcastShuffle(ShuffleVectorInst *SVI) { 3051 SmallVector<int, 16> Mask(SVI->getShuffleMask()); 3052 int SplatElem = -1; 3053 for (unsigned i = 0; i < Mask.size(); ++i) { 3054 if (SplatElem != -1 && Mask[i] != -1 && Mask[i] != SplatElem) 3055 return false; 3056 SplatElem = Mask[i]; 3057 } 3058 3059 return true; 3060} 3061 3062/// Some targets have expensive vector shifts if the lanes aren't all the same 3063/// (e.g. x86 only introduced "vpsllvd" and friends with AVX2). In these cases 3064/// it's often worth sinking a shufflevector splat down to its use so that 3065/// codegen can spot all lanes are identical. 3066bool CodeGenPrepare::OptimizeShuffleVectorInst(ShuffleVectorInst *SVI) { 3067 BasicBlock *DefBB = SVI->getParent(); 3068 3069 // Only do this xform if variable vector shifts are particularly expensive. 3070 if (!TLI || !TLI->isVectorShiftByScalarCheap(SVI->getType())) 3071 return false; 3072 3073 // We only expect better codegen by sinking a shuffle if we can recognise a 3074 // constant splat. 3075 if (!isBroadcastShuffle(SVI)) 3076 return false; 3077 3078 // InsertedShuffles - Only insert a shuffle in each block once. 3079 DenseMap<BasicBlock*, Instruction*> InsertedShuffles; 3080 3081 bool MadeChange = false; 3082 for (User *U : SVI->users()) { 3083 Instruction *UI = cast<Instruction>(U); 3084 3085 // Figure out which BB this ext is used in. 3086 BasicBlock *UserBB = UI->getParent(); 3087 if (UserBB == DefBB) continue; 3088 3089 // For now only apply this when the splat is used by a shift instruction. 3090 if (!UI->isShift()) continue; 3091 3092 // Everything checks out, sink the shuffle if the user's block doesn't 3093 // already have a copy. 3094 Instruction *&InsertedShuffle = InsertedShuffles[UserBB]; 3095 3096 if (!InsertedShuffle) { 3097 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); 3098 InsertedShuffle = new ShuffleVectorInst(SVI->getOperand(0), 3099 SVI->getOperand(1), 3100 SVI->getOperand(2), "", InsertPt); 3101 } 3102 3103 UI->replaceUsesOfWith(SVI, InsertedShuffle); 3104 MadeChange = true; 3105 } 3106 3107 // If we removed all uses, nuke the shuffle. 3108 if (SVI->use_empty()) { 3109 SVI->eraseFromParent(); 3110 MadeChange = true; 3111 } 3112 3113 return MadeChange; 3114} 3115 3116bool CodeGenPrepare::OptimizeInst(Instruction *I) { 3117 if (PHINode *P = dyn_cast<PHINode>(I)) { 3118 // It is possible for very late stage optimizations (such as SimplifyCFG) 3119 // to introduce PHI nodes too late to be cleaned up. If we detect such a 3120 // trivial PHI, go ahead and zap it here. 3121 if (Value *V = SimplifyInstruction(P, TLI ? TLI->getDataLayout() : nullptr, 3122 TLInfo, DT)) { 3123 P->replaceAllUsesWith(V); 3124 P->eraseFromParent(); 3125 ++NumPHIsElim; 3126 return true; 3127 } 3128 return false; 3129 } 3130 3131 if (CastInst *CI = dyn_cast<CastInst>(I)) { 3132 // If the source of the cast is a constant, then this should have 3133 // already been constant folded. The only reason NOT to constant fold 3134 // it is if something (e.g. LSR) was careful to place the constant 3135 // evaluation in a block other than then one that uses it (e.g. to hoist 3136 // the address of globals out of a loop). If this is the case, we don't 3137 // want to forward-subst the cast. 3138 if (isa<Constant>(CI->getOperand(0))) 3139 return false; 3140 3141 if (TLI && OptimizeNoopCopyExpression(CI, *TLI)) 3142 return true; 3143 3144 if (isa<ZExtInst>(I) || isa<SExtInst>(I)) { 3145 /// Sink a zext or sext into its user blocks if the target type doesn't 3146 /// fit in one register 3147 if (TLI && TLI->getTypeAction(CI->getContext(), 3148 TLI->getValueType(CI->getType())) == 3149 TargetLowering::TypeExpandInteger) { 3150 return SinkCast(CI); 3151 } else { 3152 bool MadeChange = MoveExtToFormExtLoad(I); 3153 return MadeChange | OptimizeExtUses(I); 3154 } 3155 } 3156 return false; 3157 } 3158 3159 if (CmpInst *CI = dyn_cast<CmpInst>(I)) 3160 if (!TLI || !TLI->hasMultipleConditionRegisters()) 3161 return OptimizeCmpExpression(CI); 3162 3163 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 3164 if (TLI) 3165 return OptimizeMemoryInst(I, I->getOperand(0), LI->getType()); 3166 return false; 3167 } 3168 3169 if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 3170 if (TLI) 3171 return OptimizeMemoryInst(I, SI->getOperand(1), 3172 SI->getOperand(0)->getType()); 3173 return false; 3174 } 3175 3176 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I); 3177 3178 if (BinOp && (BinOp->getOpcode() == Instruction::AShr || 3179 BinOp->getOpcode() == Instruction::LShr)) { 3180 ConstantInt *CI = dyn_cast<ConstantInt>(BinOp->getOperand(1)); 3181 if (TLI && CI && TLI->hasExtractBitsInsn()) 3182 return OptimizeExtractBits(BinOp, CI, *TLI); 3183 3184 return false; 3185 } 3186 3187 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 3188 if (GEPI->hasAllZeroIndices()) { 3189 /// The GEP operand must be a pointer, so must its result -> BitCast 3190 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(), 3191 GEPI->getName(), GEPI); 3192 GEPI->replaceAllUsesWith(NC); 3193 GEPI->eraseFromParent(); 3194 ++NumGEPsElim; 3195 OptimizeInst(NC); 3196 return true; 3197 } 3198 return false; 3199 } 3200 3201 if (CallInst *CI = dyn_cast<CallInst>(I)) 3202 return OptimizeCallInst(CI); 3203 3204 if (SelectInst *SI = dyn_cast<SelectInst>(I)) 3205 return OptimizeSelectInst(SI); 3206 3207 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) 3208 return OptimizeShuffleVectorInst(SVI); 3209 3210 return false; 3211} 3212 3213// In this pass we look for GEP and cast instructions that are used 3214// across basic blocks and rewrite them to improve basic-block-at-a-time 3215// selection. 3216bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) { 3217 SunkAddrs.clear(); 3218 bool MadeChange = false; 3219 3220 CurInstIterator = BB.begin(); 3221 while (CurInstIterator != BB.end()) 3222 MadeChange |= OptimizeInst(CurInstIterator++); 3223 3224 MadeChange |= DupRetToEnableTailCallOpts(&BB); 3225 3226 return MadeChange; 3227} 3228 3229// llvm.dbg.value is far away from the value then iSel may not be able 3230// handle it properly. iSel will drop llvm.dbg.value if it can not 3231// find a node corresponding to the value. 3232bool CodeGenPrepare::PlaceDbgValues(Function &F) { 3233 bool MadeChange = false; 3234 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { 3235 Instruction *PrevNonDbgInst = nullptr; 3236 for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) { 3237 Instruction *Insn = BI; ++BI; 3238 DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn); 3239 // Leave dbg.values that refer to an alloca alone. These 3240 // instrinsics describe the address of a variable (= the alloca) 3241 // being taken. They should not be moved next to the alloca 3242 // (and to the beginning of the scope), but rather stay close to 3243 // where said address is used. 3244 if (!DVI || (DVI->getValue() && isa<AllocaInst>(DVI->getValue()))) { 3245 PrevNonDbgInst = Insn; 3246 continue; 3247 } 3248 3249 Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue()); 3250 if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) { 3251 DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI); 3252 DVI->removeFromParent(); 3253 if (isa<PHINode>(VI)) 3254 DVI->insertBefore(VI->getParent()->getFirstInsertionPt()); 3255 else 3256 DVI->insertAfter(VI); 3257 MadeChange = true; 3258 ++NumDbgValueMoved; 3259 } 3260 } 3261 } 3262 return MadeChange; 3263} 3264 3265// If there is a sequence that branches based on comparing a single bit 3266// against zero that can be combined into a single instruction, and the 3267// target supports folding these into a single instruction, sink the 3268// mask and compare into the branch uses. Do this before OptimizeBlock -> 3269// OptimizeInst -> OptimizeCmpExpression, which perturbs the pattern being 3270// searched for. 3271bool CodeGenPrepare::sinkAndCmp(Function &F) { 3272 if (!EnableAndCmpSinking) 3273 return false; 3274 if (!TLI || !TLI->isMaskAndBranchFoldingLegal()) 3275 return false; 3276 bool MadeChange = false; 3277 for (Function::iterator I = F.begin(), E = F.end(); I != E; ) { 3278 BasicBlock *BB = I++; 3279 3280 // Does this BB end with the following? 3281 // %andVal = and %val, #single-bit-set 3282 // %icmpVal = icmp %andResult, 0 3283 // br i1 %cmpVal label %dest1, label %dest2" 3284 BranchInst *Brcc = dyn_cast<BranchInst>(BB->getTerminator()); 3285 if (!Brcc || !Brcc->isConditional()) 3286 continue; 3287 ICmpInst *Cmp = dyn_cast<ICmpInst>(Brcc->getOperand(0)); 3288 if (!Cmp || Cmp->getParent() != BB) 3289 continue; 3290 ConstantInt *Zero = dyn_cast<ConstantInt>(Cmp->getOperand(1)); 3291 if (!Zero || !Zero->isZero()) 3292 continue; 3293 Instruction *And = dyn_cast<Instruction>(Cmp->getOperand(0)); 3294 if (!And || And->getOpcode() != Instruction::And || And->getParent() != BB) 3295 continue; 3296 ConstantInt* Mask = dyn_cast<ConstantInt>(And->getOperand(1)); 3297 if (!Mask || !Mask->getUniqueInteger().isPowerOf2()) 3298 continue; 3299 DEBUG(dbgs() << "found and; icmp ?,0; brcc\n"); DEBUG(BB->dump()); 3300 3301 // Push the "and; icmp" for any users that are conditional branches. 3302 // Since there can only be one branch use per BB, we don't need to keep 3303 // track of which BBs we insert into. 3304 for (Value::use_iterator UI = Cmp->use_begin(), E = Cmp->use_end(); 3305 UI != E; ) { 3306 Use &TheUse = *UI; 3307 // Find brcc use. 3308 BranchInst *BrccUser = dyn_cast<BranchInst>(*UI); 3309 ++UI; 3310 if (!BrccUser || !BrccUser->isConditional()) 3311 continue; 3312 BasicBlock *UserBB = BrccUser->getParent(); 3313 if (UserBB == BB) continue; 3314 DEBUG(dbgs() << "found Brcc use\n"); 3315 3316 // Sink the "and; icmp" to use. 3317 MadeChange = true; 3318 BinaryOperator *NewAnd = 3319 BinaryOperator::CreateAnd(And->getOperand(0), And->getOperand(1), "", 3320 BrccUser); 3321 CmpInst *NewCmp = 3322 CmpInst::Create(Cmp->getOpcode(), Cmp->getPredicate(), NewAnd, Zero, 3323 "", BrccUser); 3324 TheUse = NewCmp; 3325 ++NumAndCmpsMoved; 3326 DEBUG(BrccUser->getParent()->dump()); 3327 } 3328 } 3329 return MadeChange; 3330} 3331