1 //===- Local.cpp - Functions to perform local transformations -------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This family of functions perform various local transformations to the 10 // program. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Transforms/Utils/Local.h" 15 #include "llvm/ADT/APInt.h" 16 #include "llvm/ADT/DenseMap.h" 17 #include "llvm/ADT/DenseMapInfo.h" 18 #include "llvm/ADT/DenseSet.h" 19 #include "llvm/ADT/Hashing.h" 20 #include "llvm/ADT/None.h" 21 #include "llvm/ADT/Optional.h" 22 #include "llvm/ADT/STLExtras.h" 23 #include "llvm/ADT/SetVector.h" 24 #include "llvm/ADT/SmallPtrSet.h" 25 #include "llvm/ADT/SmallVector.h" 26 #include "llvm/ADT/Statistic.h" 27 #include "llvm/Analysis/AssumeBundleQueries.h" 28 #include "llvm/Analysis/ConstantFolding.h" 29 #include "llvm/Analysis/DomTreeUpdater.h" 30 #include "llvm/Analysis/EHPersonalities.h" 31 #include "llvm/Analysis/InstructionSimplify.h" 32 #include "llvm/Analysis/MemoryBuiltins.h" 33 #include "llvm/Analysis/MemorySSAUpdater.h" 34 #include "llvm/Analysis/TargetLibraryInfo.h" 35 #include "llvm/Analysis/ValueTracking.h" 36 #include "llvm/Analysis/VectorUtils.h" 37 #include "llvm/BinaryFormat/Dwarf.h" 38 #include "llvm/IR/Argument.h" 39 #include "llvm/IR/Attributes.h" 40 #include "llvm/IR/BasicBlock.h" 41 #include "llvm/IR/CFG.h" 42 #include "llvm/IR/Constant.h" 43 #include "llvm/IR/ConstantRange.h" 44 #include "llvm/IR/Constants.h" 45 #include "llvm/IR/DIBuilder.h" 46 #include "llvm/IR/DataLayout.h" 47 #include "llvm/IR/DebugInfo.h" 48 #include "llvm/IR/DebugInfoMetadata.h" 49 #include "llvm/IR/DebugLoc.h" 50 #include "llvm/IR/DerivedTypes.h" 51 #include "llvm/IR/Dominators.h" 52 #include "llvm/IR/Function.h" 53 #include "llvm/IR/GetElementPtrTypeIterator.h" 54 #include "llvm/IR/GlobalObject.h" 55 #include "llvm/IR/IRBuilder.h" 56 #include "llvm/IR/InstrTypes.h" 57 #include "llvm/IR/Instruction.h" 58 #include "llvm/IR/Instructions.h" 59 #include "llvm/IR/IntrinsicInst.h" 60 #include "llvm/IR/Intrinsics.h" 61 #include "llvm/IR/LLVMContext.h" 62 #include "llvm/IR/MDBuilder.h" 63 #include "llvm/IR/Metadata.h" 64 #include "llvm/IR/Module.h" 65 #include "llvm/IR/PatternMatch.h" 66 #include "llvm/IR/Type.h" 67 #include "llvm/IR/Use.h" 68 #include "llvm/IR/User.h" 69 #include "llvm/IR/Value.h" 70 #include "llvm/IR/ValueHandle.h" 71 #include "llvm/Support/Casting.h" 72 #include "llvm/Support/Debug.h" 73 #include "llvm/Support/ErrorHandling.h" 74 #include "llvm/Support/KnownBits.h" 75 #include "llvm/Support/raw_ostream.h" 76 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 77 #include "llvm/Transforms/Utils/ValueMapper.h" 78 #include <algorithm> 79 #include <cassert> 80 #include <cstdint> 81 #include <iterator> 82 #include <map> 83 #include <utility> 84 85 using namespace llvm; 86 using namespace llvm::PatternMatch; 87 88 #define DEBUG_TYPE "local" 89 90 STATISTIC(NumRemoved, "Number of unreachable basic blocks removed"); 91 STATISTIC(NumPHICSEs, "Number of PHI's that got CSE'd"); 92 93 static cl::opt<bool> PHICSEDebugHash( 94 "phicse-debug-hash", 95 #ifdef EXPENSIVE_CHECKS 96 cl::init(true), 97 #else 98 cl::init(false), 99 #endif 100 cl::Hidden, 101 cl::desc("Perform extra assertion checking to verify that PHINodes's hash " 102 "function is well-behaved w.r.t. its isEqual predicate")); 103 104 static cl::opt<unsigned> PHICSENumPHISmallSize( 105 "phicse-num-phi-smallsize", cl::init(32), cl::Hidden, 106 cl::desc( 107 "When the basic block contains not more than this number of PHI nodes, " 108 "perform a (faster!) exhaustive search instead of set-driven one.")); 109 110 // Max recursion depth for collectBitParts used when detecting bswap and 111 // bitreverse idioms. 112 static const unsigned BitPartRecursionMaxDepth = 48; 113 114 //===----------------------------------------------------------------------===// 115 // Local constant propagation. 116 // 117 118 /// ConstantFoldTerminator - If a terminator instruction is predicated on a 119 /// constant value, convert it into an unconditional branch to the constant 120 /// destination. This is a nontrivial operation because the successors of this 121 /// basic block must have their PHI nodes updated. 122 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch 123 /// conditions and indirectbr addresses this might make dead if 124 /// DeleteDeadConditions is true. 125 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, 126 const TargetLibraryInfo *TLI, 127 DomTreeUpdater *DTU) { 128 Instruction *T = BB->getTerminator(); 129 IRBuilder<> Builder(T); 130 131 // Branch - See if we are conditional jumping on constant 132 if (auto *BI = dyn_cast<BranchInst>(T)) { 133 if (BI->isUnconditional()) return false; // Can't optimize uncond branch 134 135 BasicBlock *Dest1 = BI->getSuccessor(0); 136 BasicBlock *Dest2 = BI->getSuccessor(1); 137 138 if (Dest2 == Dest1) { // Conditional branch to same location? 139 // This branch matches something like this: 140 // br bool %cond, label %Dest, label %Dest 141 // and changes it into: br label %Dest 142 143 // Let the basic block know that we are letting go of one copy of it. 144 assert(BI->getParent() && "Terminator not inserted in block!"); 145 Dest1->removePredecessor(BI->getParent()); 146 147 // Replace the conditional branch with an unconditional one. 148 BranchInst *NewBI = Builder.CreateBr(Dest1); 149 150 // Transfer the metadata to the new branch instruction. 151 NewBI->copyMetadata(*BI, {LLVMContext::MD_loop, LLVMContext::MD_dbg, 152 LLVMContext::MD_annotation}); 153 154 Value *Cond = BI->getCondition(); 155 BI->eraseFromParent(); 156 if (DeleteDeadConditions) 157 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); 158 return true; 159 } 160 161 if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) { 162 // Are we branching on constant? 163 // YES. Change to unconditional branch... 164 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2; 165 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1; 166 167 // Let the basic block know that we are letting go of it. Based on this, 168 // it will adjust it's PHI nodes. 169 OldDest->removePredecessor(BB); 170 171 // Replace the conditional branch with an unconditional one. 172 BranchInst *NewBI = Builder.CreateBr(Destination); 173 174 // Transfer the metadata to the new branch instruction. 175 NewBI->copyMetadata(*BI, {LLVMContext::MD_loop, LLVMContext::MD_dbg, 176 LLVMContext::MD_annotation}); 177 178 BI->eraseFromParent(); 179 if (DTU) 180 DTU->applyUpdates({{DominatorTree::Delete, BB, OldDest}}); 181 return true; 182 } 183 184 return false; 185 } 186 187 if (auto *SI = dyn_cast<SwitchInst>(T)) { 188 // If we are switching on a constant, we can convert the switch to an 189 // unconditional branch. 190 auto *CI = dyn_cast<ConstantInt>(SI->getCondition()); 191 BasicBlock *DefaultDest = SI->getDefaultDest(); 192 BasicBlock *TheOnlyDest = DefaultDest; 193 194 // If the default is unreachable, ignore it when searching for TheOnlyDest. 195 if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) && 196 SI->getNumCases() > 0) { 197 TheOnlyDest = SI->case_begin()->getCaseSuccessor(); 198 } 199 200 bool Changed = false; 201 202 // Figure out which case it goes to. 203 for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) { 204 // Found case matching a constant operand? 205 if (i->getCaseValue() == CI) { 206 TheOnlyDest = i->getCaseSuccessor(); 207 break; 208 } 209 210 // Check to see if this branch is going to the same place as the default 211 // dest. If so, eliminate it as an explicit compare. 212 if (i->getCaseSuccessor() == DefaultDest) { 213 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); 214 unsigned NCases = SI->getNumCases(); 215 // Fold the case metadata into the default if there will be any branches 216 // left, unless the metadata doesn't match the switch. 217 if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) { 218 // Collect branch weights into a vector. 219 SmallVector<uint32_t, 8> Weights; 220 for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; 221 ++MD_i) { 222 auto *CI = mdconst::extract<ConstantInt>(MD->getOperand(MD_i)); 223 Weights.push_back(CI->getValue().getZExtValue()); 224 } 225 // Merge weight of this case to the default weight. 226 unsigned idx = i->getCaseIndex(); 227 Weights[0] += Weights[idx+1]; 228 // Remove weight for this case. 229 std::swap(Weights[idx+1], Weights.back()); 230 Weights.pop_back(); 231 SI->setMetadata(LLVMContext::MD_prof, 232 MDBuilder(BB->getContext()). 233 createBranchWeights(Weights)); 234 } 235 // Remove this entry. 236 BasicBlock *ParentBB = SI->getParent(); 237 DefaultDest->removePredecessor(ParentBB); 238 i = SI->removeCase(i); 239 e = SI->case_end(); 240 Changed = true; 241 continue; 242 } 243 244 // Otherwise, check to see if the switch only branches to one destination. 245 // We do this by reseting "TheOnlyDest" to null when we find two non-equal 246 // destinations. 247 if (i->getCaseSuccessor() != TheOnlyDest) 248 TheOnlyDest = nullptr; 249 250 // Increment this iterator as we haven't removed the case. 251 ++i; 252 } 253 254 if (CI && !TheOnlyDest) { 255 // Branching on a constant, but not any of the cases, go to the default 256 // successor. 257 TheOnlyDest = SI->getDefaultDest(); 258 } 259 260 // If we found a single destination that we can fold the switch into, do so 261 // now. 262 if (TheOnlyDest) { 263 // Insert the new branch. 264 Builder.CreateBr(TheOnlyDest); 265 BasicBlock *BB = SI->getParent(); 266 267 SmallSet<BasicBlock *, 8> RemovedSuccessors; 268 269 // Remove entries from PHI nodes which we no longer branch to... 270 BasicBlock *SuccToKeep = TheOnlyDest; 271 for (BasicBlock *Succ : successors(SI)) { 272 if (DTU && Succ != TheOnlyDest) 273 RemovedSuccessors.insert(Succ); 274 // Found case matching a constant operand? 275 if (Succ == SuccToKeep) { 276 SuccToKeep = nullptr; // Don't modify the first branch to TheOnlyDest 277 } else { 278 Succ->removePredecessor(BB); 279 } 280 } 281 282 // Delete the old switch. 283 Value *Cond = SI->getCondition(); 284 SI->eraseFromParent(); 285 if (DeleteDeadConditions) 286 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); 287 if (DTU) { 288 std::vector<DominatorTree::UpdateType> Updates; 289 Updates.reserve(RemovedSuccessors.size()); 290 for (auto *RemovedSuccessor : RemovedSuccessors) 291 Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor}); 292 DTU->applyUpdates(Updates); 293 } 294 return true; 295 } 296 297 if (SI->getNumCases() == 1) { 298 // Otherwise, we can fold this switch into a conditional branch 299 // instruction if it has only one non-default destination. 300 auto FirstCase = *SI->case_begin(); 301 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(), 302 FirstCase.getCaseValue(), "cond"); 303 304 // Insert the new branch. 305 BranchInst *NewBr = Builder.CreateCondBr(Cond, 306 FirstCase.getCaseSuccessor(), 307 SI->getDefaultDest()); 308 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); 309 if (MD && MD->getNumOperands() == 3) { 310 ConstantInt *SICase = 311 mdconst::dyn_extract<ConstantInt>(MD->getOperand(2)); 312 ConstantInt *SIDef = 313 mdconst::dyn_extract<ConstantInt>(MD->getOperand(1)); 314 assert(SICase && SIDef); 315 // The TrueWeight should be the weight for the single case of SI. 316 NewBr->setMetadata(LLVMContext::MD_prof, 317 MDBuilder(BB->getContext()). 318 createBranchWeights(SICase->getValue().getZExtValue(), 319 SIDef->getValue().getZExtValue())); 320 } 321 322 // Update make.implicit metadata to the newly-created conditional branch. 323 MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit); 324 if (MakeImplicitMD) 325 NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD); 326 327 // Delete the old switch. 328 SI->eraseFromParent(); 329 return true; 330 } 331 return Changed; 332 } 333 334 if (auto *IBI = dyn_cast<IndirectBrInst>(T)) { 335 // indirectbr blockaddress(@F, @BB) -> br label @BB 336 if (auto *BA = 337 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) { 338 BasicBlock *TheOnlyDest = BA->getBasicBlock(); 339 SmallSet<BasicBlock *, 8> RemovedSuccessors; 340 341 // Insert the new branch. 342 Builder.CreateBr(TheOnlyDest); 343 344 BasicBlock *SuccToKeep = TheOnlyDest; 345 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { 346 BasicBlock *DestBB = IBI->getDestination(i); 347 if (DTU && DestBB != TheOnlyDest) 348 RemovedSuccessors.insert(DestBB); 349 if (IBI->getDestination(i) == SuccToKeep) { 350 SuccToKeep = nullptr; 351 } else { 352 DestBB->removePredecessor(BB); 353 } 354 } 355 Value *Address = IBI->getAddress(); 356 IBI->eraseFromParent(); 357 if (DeleteDeadConditions) 358 // Delete pointer cast instructions. 359 RecursivelyDeleteTriviallyDeadInstructions(Address, TLI); 360 361 // Also zap the blockaddress constant if there are no users remaining, 362 // otherwise the destination is still marked as having its address taken. 363 if (BA->use_empty()) 364 BA->destroyConstant(); 365 366 // If we didn't find our destination in the IBI successor list, then we 367 // have undefined behavior. Replace the unconditional branch with an 368 // 'unreachable' instruction. 369 if (SuccToKeep) { 370 BB->getTerminator()->eraseFromParent(); 371 new UnreachableInst(BB->getContext(), BB); 372 } 373 374 if (DTU) { 375 std::vector<DominatorTree::UpdateType> Updates; 376 Updates.reserve(RemovedSuccessors.size()); 377 for (auto *RemovedSuccessor : RemovedSuccessors) 378 Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor}); 379 DTU->applyUpdates(Updates); 380 } 381 return true; 382 } 383 } 384 385 return false; 386 } 387 388 //===----------------------------------------------------------------------===// 389 // Local dead code elimination. 390 // 391 392 /// isInstructionTriviallyDead - Return true if the result produced by the 393 /// instruction is not used, and the instruction has no side effects. 394 /// 395 bool llvm::isInstructionTriviallyDead(Instruction *I, 396 const TargetLibraryInfo *TLI) { 397 if (!I->use_empty()) 398 return false; 399 return wouldInstructionBeTriviallyDead(I, TLI); 400 } 401 402 bool llvm::wouldInstructionBeTriviallyDeadOnUnusedPaths( 403 Instruction *I, const TargetLibraryInfo *TLI) { 404 // Instructions that are "markers" and have implied meaning on code around 405 // them (without explicit uses), are not dead on unused paths. 406 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) 407 if (II->getIntrinsicID() == Intrinsic::stacksave || 408 II->getIntrinsicID() == Intrinsic::launder_invariant_group || 409 II->isLifetimeStartOrEnd()) 410 return false; 411 return wouldInstructionBeTriviallyDead(I, TLI); 412 } 413 414 bool llvm::wouldInstructionBeTriviallyDead(Instruction *I, 415 const TargetLibraryInfo *TLI) { 416 if (I->isTerminator()) 417 return false; 418 419 // We don't want the landingpad-like instructions removed by anything this 420 // general. 421 if (I->isEHPad()) 422 return false; 423 424 // We don't want debug info removed by anything this general, unless 425 // debug info is empty. 426 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) { 427 if (DDI->getAddress()) 428 return false; 429 return true; 430 } 431 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) { 432 if (DVI->hasArgList() || DVI->getValue(0)) 433 return false; 434 return true; 435 } 436 if (DbgLabelInst *DLI = dyn_cast<DbgLabelInst>(I)) { 437 if (DLI->getLabel()) 438 return false; 439 return true; 440 } 441 442 if (!I->willReturn()) 443 return false; 444 445 if (!I->mayHaveSideEffects()) 446 return true; 447 448 // Special case intrinsics that "may have side effects" but can be deleted 449 // when dead. 450 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 451 // Safe to delete llvm.stacksave and launder.invariant.group if dead. 452 if (II->getIntrinsicID() == Intrinsic::stacksave || 453 II->getIntrinsicID() == Intrinsic::launder_invariant_group) 454 return true; 455 456 if (II->isLifetimeStartOrEnd()) { 457 auto *Arg = II->getArgOperand(1); 458 // Lifetime intrinsics are dead when their right-hand is undef. 459 if (isa<UndefValue>(Arg)) 460 return true; 461 // If the right-hand is an alloc, global, or argument and the only uses 462 // are lifetime intrinsics then the intrinsics are dead. 463 if (isa<AllocaInst>(Arg) || isa<GlobalValue>(Arg) || isa<Argument>(Arg)) 464 return llvm::all_of(Arg->uses(), [](Use &Use) { 465 if (IntrinsicInst *IntrinsicUse = 466 dyn_cast<IntrinsicInst>(Use.getUser())) 467 return IntrinsicUse->isLifetimeStartOrEnd(); 468 return false; 469 }); 470 return false; 471 } 472 473 // Assumptions are dead if their condition is trivially true. Guards on 474 // true are operationally no-ops. In the future we can consider more 475 // sophisticated tradeoffs for guards considering potential for check 476 // widening, but for now we keep things simple. 477 if ((II->getIntrinsicID() == Intrinsic::assume && 478 isAssumeWithEmptyBundle(cast<AssumeInst>(*II))) || 479 II->getIntrinsicID() == Intrinsic::experimental_guard) { 480 if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0))) 481 return !Cond->isZero(); 482 483 return false; 484 } 485 486 if (auto *FPI = dyn_cast<ConstrainedFPIntrinsic>(I)) { 487 Optional<fp::ExceptionBehavior> ExBehavior = FPI->getExceptionBehavior(); 488 return *ExBehavior != fp::ebStrict; 489 } 490 } 491 492 if (isAllocationFn(I, TLI) && isAllocRemovable(cast<CallBase>(I), TLI)) 493 return true; 494 495 if (CallInst *CI = isFreeCall(I, TLI)) 496 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0))) 497 return C->isNullValue() || isa<UndefValue>(C); 498 499 if (auto *Call = dyn_cast<CallBase>(I)) 500 if (isMathLibCallNoop(Call, TLI)) 501 return true; 502 503 // Non-volatile atomic loads from constants can be removed. 504 if (auto *LI = dyn_cast<LoadInst>(I)) 505 if (auto *GV = dyn_cast<GlobalVariable>( 506 LI->getPointerOperand()->stripPointerCasts())) 507 if (!LI->isVolatile() && GV->isConstant()) 508 return true; 509 510 return false; 511 } 512 513 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a 514 /// trivially dead instruction, delete it. If that makes any of its operands 515 /// trivially dead, delete them too, recursively. Return true if any 516 /// instructions were deleted. 517 bool llvm::RecursivelyDeleteTriviallyDeadInstructions( 518 Value *V, const TargetLibraryInfo *TLI, MemorySSAUpdater *MSSAU, 519 std::function<void(Value *)> AboutToDeleteCallback) { 520 Instruction *I = dyn_cast<Instruction>(V); 521 if (!I || !isInstructionTriviallyDead(I, TLI)) 522 return false; 523 524 SmallVector<WeakTrackingVH, 16> DeadInsts; 525 DeadInsts.push_back(I); 526 RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU, 527 AboutToDeleteCallback); 528 529 return true; 530 } 531 532 bool llvm::RecursivelyDeleteTriviallyDeadInstructionsPermissive( 533 SmallVectorImpl<WeakTrackingVH> &DeadInsts, const TargetLibraryInfo *TLI, 534 MemorySSAUpdater *MSSAU, 535 std::function<void(Value *)> AboutToDeleteCallback) { 536 unsigned S = 0, E = DeadInsts.size(), Alive = 0; 537 for (; S != E; ++S) { 538 auto *I = dyn_cast<Instruction>(DeadInsts[S]); 539 if (!I || !isInstructionTriviallyDead(I)) { 540 DeadInsts[S] = nullptr; 541 ++Alive; 542 } 543 } 544 if (Alive == E) 545 return false; 546 RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU, 547 AboutToDeleteCallback); 548 return true; 549 } 550 551 void llvm::RecursivelyDeleteTriviallyDeadInstructions( 552 SmallVectorImpl<WeakTrackingVH> &DeadInsts, const TargetLibraryInfo *TLI, 553 MemorySSAUpdater *MSSAU, 554 std::function<void(Value *)> AboutToDeleteCallback) { 555 // Process the dead instruction list until empty. 556 while (!DeadInsts.empty()) { 557 Value *V = DeadInsts.pop_back_val(); 558 Instruction *I = cast_or_null<Instruction>(V); 559 if (!I) 560 continue; 561 assert(isInstructionTriviallyDead(I, TLI) && 562 "Live instruction found in dead worklist!"); 563 assert(I->use_empty() && "Instructions with uses are not dead."); 564 565 // Don't lose the debug info while deleting the instructions. 566 salvageDebugInfo(*I); 567 568 if (AboutToDeleteCallback) 569 AboutToDeleteCallback(I); 570 571 // Null out all of the instruction's operands to see if any operand becomes 572 // dead as we go. 573 for (Use &OpU : I->operands()) { 574 Value *OpV = OpU.get(); 575 OpU.set(nullptr); 576 577 if (!OpV->use_empty()) 578 continue; 579 580 // If the operand is an instruction that became dead as we nulled out the 581 // operand, and if it is 'trivially' dead, delete it in a future loop 582 // iteration. 583 if (Instruction *OpI = dyn_cast<Instruction>(OpV)) 584 if (isInstructionTriviallyDead(OpI, TLI)) 585 DeadInsts.push_back(OpI); 586 } 587 if (MSSAU) 588 MSSAU->removeMemoryAccess(I); 589 590 I->eraseFromParent(); 591 } 592 } 593 594 bool llvm::replaceDbgUsesWithUndef(Instruction *I) { 595 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; 596 findDbgUsers(DbgUsers, I); 597 for (auto *DII : DbgUsers) { 598 Value *Undef = UndefValue::get(I->getType()); 599 DII->replaceVariableLocationOp(I, Undef); 600 } 601 return !DbgUsers.empty(); 602 } 603 604 /// areAllUsesEqual - Check whether the uses of a value are all the same. 605 /// This is similar to Instruction::hasOneUse() except this will also return 606 /// true when there are no uses or multiple uses that all refer to the same 607 /// value. 608 static bool areAllUsesEqual(Instruction *I) { 609 Value::user_iterator UI = I->user_begin(); 610 Value::user_iterator UE = I->user_end(); 611 if (UI == UE) 612 return true; 613 614 User *TheUse = *UI; 615 for (++UI; UI != UE; ++UI) { 616 if (*UI != TheUse) 617 return false; 618 } 619 return true; 620 } 621 622 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively 623 /// dead PHI node, due to being a def-use chain of single-use nodes that 624 /// either forms a cycle or is terminated by a trivially dead instruction, 625 /// delete it. If that makes any of its operands trivially dead, delete them 626 /// too, recursively. Return true if a change was made. 627 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN, 628 const TargetLibraryInfo *TLI, 629 llvm::MemorySSAUpdater *MSSAU) { 630 SmallPtrSet<Instruction*, 4> Visited; 631 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects(); 632 I = cast<Instruction>(*I->user_begin())) { 633 if (I->use_empty()) 634 return RecursivelyDeleteTriviallyDeadInstructions(I, TLI, MSSAU); 635 636 // If we find an instruction more than once, we're on a cycle that 637 // won't prove fruitful. 638 if (!Visited.insert(I).second) { 639 // Break the cycle and delete the instruction and its operands. 640 I->replaceAllUsesWith(UndefValue::get(I->getType())); 641 (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI, MSSAU); 642 return true; 643 } 644 } 645 return false; 646 } 647 648 static bool 649 simplifyAndDCEInstruction(Instruction *I, 650 SmallSetVector<Instruction *, 16> &WorkList, 651 const DataLayout &DL, 652 const TargetLibraryInfo *TLI) { 653 if (isInstructionTriviallyDead(I, TLI)) { 654 salvageDebugInfo(*I); 655 656 // Null out all of the instruction's operands to see if any operand becomes 657 // dead as we go. 658 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { 659 Value *OpV = I->getOperand(i); 660 I->setOperand(i, nullptr); 661 662 if (!OpV->use_empty() || I == OpV) 663 continue; 664 665 // If the operand is an instruction that became dead as we nulled out the 666 // operand, and if it is 'trivially' dead, delete it in a future loop 667 // iteration. 668 if (Instruction *OpI = dyn_cast<Instruction>(OpV)) 669 if (isInstructionTriviallyDead(OpI, TLI)) 670 WorkList.insert(OpI); 671 } 672 673 I->eraseFromParent(); 674 675 return true; 676 } 677 678 if (Value *SimpleV = simplifyInstruction(I, DL)) { 679 // Add the users to the worklist. CAREFUL: an instruction can use itself, 680 // in the case of a phi node. 681 for (User *U : I->users()) { 682 if (U != I) { 683 WorkList.insert(cast<Instruction>(U)); 684 } 685 } 686 687 // Replace the instruction with its simplified value. 688 bool Changed = false; 689 if (!I->use_empty()) { 690 I->replaceAllUsesWith(SimpleV); 691 Changed = true; 692 } 693 if (isInstructionTriviallyDead(I, TLI)) { 694 I->eraseFromParent(); 695 Changed = true; 696 } 697 return Changed; 698 } 699 return false; 700 } 701 702 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to 703 /// simplify any instructions in it and recursively delete dead instructions. 704 /// 705 /// This returns true if it changed the code, note that it can delete 706 /// instructions in other blocks as well in this block. 707 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, 708 const TargetLibraryInfo *TLI) { 709 bool MadeChange = false; 710 const DataLayout &DL = BB->getModule()->getDataLayout(); 711 712 #ifndef NDEBUG 713 // In debug builds, ensure that the terminator of the block is never replaced 714 // or deleted by these simplifications. The idea of simplification is that it 715 // cannot introduce new instructions, and there is no way to replace the 716 // terminator of a block without introducing a new instruction. 717 AssertingVH<Instruction> TerminatorVH(&BB->back()); 718 #endif 719 720 SmallSetVector<Instruction *, 16> WorkList; 721 // Iterate over the original function, only adding insts to the worklist 722 // if they actually need to be revisited. This avoids having to pre-init 723 // the worklist with the entire function's worth of instructions. 724 for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end()); 725 BI != E;) { 726 assert(!BI->isTerminator()); 727 Instruction *I = &*BI; 728 ++BI; 729 730 // We're visiting this instruction now, so make sure it's not in the 731 // worklist from an earlier visit. 732 if (!WorkList.count(I)) 733 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI); 734 } 735 736 while (!WorkList.empty()) { 737 Instruction *I = WorkList.pop_back_val(); 738 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI); 739 } 740 return MadeChange; 741 } 742 743 //===----------------------------------------------------------------------===// 744 // Control Flow Graph Restructuring. 745 // 746 747 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, 748 DomTreeUpdater *DTU) { 749 750 // If BB has single-entry PHI nodes, fold them. 751 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) { 752 Value *NewVal = PN->getIncomingValue(0); 753 // Replace self referencing PHI with undef, it must be dead. 754 if (NewVal == PN) NewVal = UndefValue::get(PN->getType()); 755 PN->replaceAllUsesWith(NewVal); 756 PN->eraseFromParent(); 757 } 758 759 BasicBlock *PredBB = DestBB->getSinglePredecessor(); 760 assert(PredBB && "Block doesn't have a single predecessor!"); 761 762 bool ReplaceEntryBB = PredBB->isEntryBlock(); 763 764 // DTU updates: Collect all the edges that enter 765 // PredBB. These dominator edges will be redirected to DestBB. 766 SmallVector<DominatorTree::UpdateType, 32> Updates; 767 768 if (DTU) { 769 // To avoid processing the same predecessor more than once. 770 SmallPtrSet<BasicBlock *, 2> SeenPreds; 771 Updates.reserve(Updates.size() + 2 * pred_size(PredBB) + 1); 772 for (BasicBlock *PredOfPredBB : predecessors(PredBB)) 773 // This predecessor of PredBB may already have DestBB as a successor. 774 if (PredOfPredBB != PredBB) 775 if (SeenPreds.insert(PredOfPredBB).second) 776 Updates.push_back({DominatorTree::Insert, PredOfPredBB, DestBB}); 777 SeenPreds.clear(); 778 for (BasicBlock *PredOfPredBB : predecessors(PredBB)) 779 if (SeenPreds.insert(PredOfPredBB).second) 780 Updates.push_back({DominatorTree::Delete, PredOfPredBB, PredBB}); 781 Updates.push_back({DominatorTree::Delete, PredBB, DestBB}); 782 } 783 784 // Zap anything that took the address of DestBB. Not doing this will give the 785 // address an invalid value. 786 if (DestBB->hasAddressTaken()) { 787 BlockAddress *BA = BlockAddress::get(DestBB); 788 Constant *Replacement = 789 ConstantInt::get(Type::getInt32Ty(BA->getContext()), 1); 790 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, 791 BA->getType())); 792 BA->destroyConstant(); 793 } 794 795 // Anything that branched to PredBB now branches to DestBB. 796 PredBB->replaceAllUsesWith(DestBB); 797 798 // Splice all the instructions from PredBB to DestBB. 799 PredBB->getTerminator()->eraseFromParent(); 800 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList()); 801 new UnreachableInst(PredBB->getContext(), PredBB); 802 803 // If the PredBB is the entry block of the function, move DestBB up to 804 // become the entry block after we erase PredBB. 805 if (ReplaceEntryBB) 806 DestBB->moveAfter(PredBB); 807 808 if (DTU) { 809 assert(PredBB->getInstList().size() == 1 && 810 isa<UnreachableInst>(PredBB->getTerminator()) && 811 "The successor list of PredBB isn't empty before " 812 "applying corresponding DTU updates."); 813 DTU->applyUpdatesPermissive(Updates); 814 DTU->deleteBB(PredBB); 815 // Recalculation of DomTree is needed when updating a forward DomTree and 816 // the Entry BB is replaced. 817 if (ReplaceEntryBB && DTU->hasDomTree()) { 818 // The entry block was removed and there is no external interface for 819 // the dominator tree to be notified of this change. In this corner-case 820 // we recalculate the entire tree. 821 DTU->recalculate(*(DestBB->getParent())); 822 } 823 } 824 825 else { 826 PredBB->eraseFromParent(); // Nuke BB if DTU is nullptr. 827 } 828 } 829 830 /// Return true if we can choose one of these values to use in place of the 831 /// other. Note that we will always choose the non-undef value to keep. 832 static bool CanMergeValues(Value *First, Value *Second) { 833 return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second); 834 } 835 836 /// Return true if we can fold BB, an almost-empty BB ending in an unconditional 837 /// branch to Succ, into Succ. 838 /// 839 /// Assumption: Succ is the single successor for BB. 840 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) { 841 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!"); 842 843 LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into " 844 << Succ->getName() << "\n"); 845 // Shortcut, if there is only a single predecessor it must be BB and merging 846 // is always safe 847 if (Succ->getSinglePredecessor()) return true; 848 849 // Make a list of the predecessors of BB 850 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB)); 851 852 // Look at all the phi nodes in Succ, to see if they present a conflict when 853 // merging these blocks 854 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { 855 PHINode *PN = cast<PHINode>(I); 856 857 // If the incoming value from BB is again a PHINode in 858 // BB which has the same incoming value for *PI as PN does, we can 859 // merge the phi nodes and then the blocks can still be merged 860 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB)); 861 if (BBPN && BBPN->getParent() == BB) { 862 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { 863 BasicBlock *IBB = PN->getIncomingBlock(PI); 864 if (BBPreds.count(IBB) && 865 !CanMergeValues(BBPN->getIncomingValueForBlock(IBB), 866 PN->getIncomingValue(PI))) { 867 LLVM_DEBUG(dbgs() 868 << "Can't fold, phi node " << PN->getName() << " in " 869 << Succ->getName() << " is conflicting with " 870 << BBPN->getName() << " with regard to common predecessor " 871 << IBB->getName() << "\n"); 872 return false; 873 } 874 } 875 } else { 876 Value* Val = PN->getIncomingValueForBlock(BB); 877 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { 878 // See if the incoming value for the common predecessor is equal to the 879 // one for BB, in which case this phi node will not prevent the merging 880 // of the block. 881 BasicBlock *IBB = PN->getIncomingBlock(PI); 882 if (BBPreds.count(IBB) && 883 !CanMergeValues(Val, PN->getIncomingValue(PI))) { 884 LLVM_DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() 885 << " in " << Succ->getName() 886 << " is conflicting with regard to common " 887 << "predecessor " << IBB->getName() << "\n"); 888 return false; 889 } 890 } 891 } 892 } 893 894 return true; 895 } 896 897 using PredBlockVector = SmallVector<BasicBlock *, 16>; 898 using IncomingValueMap = DenseMap<BasicBlock *, Value *>; 899 900 /// Determines the value to use as the phi node input for a block. 901 /// 902 /// Select between \p OldVal any value that we know flows from \p BB 903 /// to a particular phi on the basis of which one (if either) is not 904 /// undef. Update IncomingValues based on the selected value. 905 /// 906 /// \param OldVal The value we are considering selecting. 907 /// \param BB The block that the value flows in from. 908 /// \param IncomingValues A map from block-to-value for other phi inputs 909 /// that we have examined. 910 /// 911 /// \returns the selected value. 912 static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB, 913 IncomingValueMap &IncomingValues) { 914 if (!isa<UndefValue>(OldVal)) { 915 assert((!IncomingValues.count(BB) || 916 IncomingValues.find(BB)->second == OldVal) && 917 "Expected OldVal to match incoming value from BB!"); 918 919 IncomingValues.insert(std::make_pair(BB, OldVal)); 920 return OldVal; 921 } 922 923 IncomingValueMap::const_iterator It = IncomingValues.find(BB); 924 if (It != IncomingValues.end()) return It->second; 925 926 return OldVal; 927 } 928 929 /// Create a map from block to value for the operands of a 930 /// given phi. 931 /// 932 /// Create a map from block to value for each non-undef value flowing 933 /// into \p PN. 934 /// 935 /// \param PN The phi we are collecting the map for. 936 /// \param IncomingValues [out] The map from block to value for this phi. 937 static void gatherIncomingValuesToPhi(PHINode *PN, 938 IncomingValueMap &IncomingValues) { 939 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 940 BasicBlock *BB = PN->getIncomingBlock(i); 941 Value *V = PN->getIncomingValue(i); 942 943 if (!isa<UndefValue>(V)) 944 IncomingValues.insert(std::make_pair(BB, V)); 945 } 946 } 947 948 /// Replace the incoming undef values to a phi with the values 949 /// from a block-to-value map. 950 /// 951 /// \param PN The phi we are replacing the undefs in. 952 /// \param IncomingValues A map from block to value. 953 static void replaceUndefValuesInPhi(PHINode *PN, 954 const IncomingValueMap &IncomingValues) { 955 SmallVector<unsigned> TrueUndefOps; 956 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 957 Value *V = PN->getIncomingValue(i); 958 959 if (!isa<UndefValue>(V)) continue; 960 961 BasicBlock *BB = PN->getIncomingBlock(i); 962 IncomingValueMap::const_iterator It = IncomingValues.find(BB); 963 964 // Keep track of undef/poison incoming values. Those must match, so we fix 965 // them up below if needed. 966 // Note: this is conservatively correct, but we could try harder and group 967 // the undef values per incoming basic block. 968 if (It == IncomingValues.end()) { 969 TrueUndefOps.push_back(i); 970 continue; 971 } 972 973 // There is a defined value for this incoming block, so map this undef 974 // incoming value to the defined value. 975 PN->setIncomingValue(i, It->second); 976 } 977 978 // If there are both undef and poison values incoming, then convert those 979 // values to undef. It is invalid to have different values for the same 980 // incoming block. 981 unsigned PoisonCount = count_if(TrueUndefOps, [&](unsigned i) { 982 return isa<PoisonValue>(PN->getIncomingValue(i)); 983 }); 984 if (PoisonCount != 0 && PoisonCount != TrueUndefOps.size()) { 985 for (unsigned i : TrueUndefOps) 986 PN->setIncomingValue(i, UndefValue::get(PN->getType())); 987 } 988 } 989 990 /// Replace a value flowing from a block to a phi with 991 /// potentially multiple instances of that value flowing from the 992 /// block's predecessors to the phi. 993 /// 994 /// \param BB The block with the value flowing into the phi. 995 /// \param BBPreds The predecessors of BB. 996 /// \param PN The phi that we are updating. 997 static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB, 998 const PredBlockVector &BBPreds, 999 PHINode *PN) { 1000 Value *OldVal = PN->removeIncomingValue(BB, false); 1001 assert(OldVal && "No entry in PHI for Pred BB!"); 1002 1003 IncomingValueMap IncomingValues; 1004 1005 // We are merging two blocks - BB, and the block containing PN - and 1006 // as a result we need to redirect edges from the predecessors of BB 1007 // to go to the block containing PN, and update PN 1008 // accordingly. Since we allow merging blocks in the case where the 1009 // predecessor and successor blocks both share some predecessors, 1010 // and where some of those common predecessors might have undef 1011 // values flowing into PN, we want to rewrite those values to be 1012 // consistent with the non-undef values. 1013 1014 gatherIncomingValuesToPhi(PN, IncomingValues); 1015 1016 // If this incoming value is one of the PHI nodes in BB, the new entries 1017 // in the PHI node are the entries from the old PHI. 1018 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) { 1019 PHINode *OldValPN = cast<PHINode>(OldVal); 1020 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) { 1021 // Note that, since we are merging phi nodes and BB and Succ might 1022 // have common predecessors, we could end up with a phi node with 1023 // identical incoming branches. This will be cleaned up later (and 1024 // will trigger asserts if we try to clean it up now, without also 1025 // simplifying the corresponding conditional branch). 1026 BasicBlock *PredBB = OldValPN->getIncomingBlock(i); 1027 Value *PredVal = OldValPN->getIncomingValue(i); 1028 Value *Selected = selectIncomingValueForBlock(PredVal, PredBB, 1029 IncomingValues); 1030 1031 // And add a new incoming value for this predecessor for the 1032 // newly retargeted branch. 1033 PN->addIncoming(Selected, PredBB); 1034 } 1035 } else { 1036 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) { 1037 // Update existing incoming values in PN for this 1038 // predecessor of BB. 1039 BasicBlock *PredBB = BBPreds[i]; 1040 Value *Selected = selectIncomingValueForBlock(OldVal, PredBB, 1041 IncomingValues); 1042 1043 // And add a new incoming value for this predecessor for the 1044 // newly retargeted branch. 1045 PN->addIncoming(Selected, PredBB); 1046 } 1047 } 1048 1049 replaceUndefValuesInPhi(PN, IncomingValues); 1050 } 1051 1052 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB, 1053 DomTreeUpdater *DTU) { 1054 assert(BB != &BB->getParent()->getEntryBlock() && 1055 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!"); 1056 1057 // We can't eliminate infinite loops. 1058 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0); 1059 if (BB == Succ) return false; 1060 1061 // Check to see if merging these blocks would cause conflicts for any of the 1062 // phi nodes in BB or Succ. If not, we can safely merge. 1063 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false; 1064 1065 // Check for cases where Succ has multiple predecessors and a PHI node in BB 1066 // has uses which will not disappear when the PHI nodes are merged. It is 1067 // possible to handle such cases, but difficult: it requires checking whether 1068 // BB dominates Succ, which is non-trivial to calculate in the case where 1069 // Succ has multiple predecessors. Also, it requires checking whether 1070 // constructing the necessary self-referential PHI node doesn't introduce any 1071 // conflicts; this isn't too difficult, but the previous code for doing this 1072 // was incorrect. 1073 // 1074 // Note that if this check finds a live use, BB dominates Succ, so BB is 1075 // something like a loop pre-header (or rarely, a part of an irreducible CFG); 1076 // folding the branch isn't profitable in that case anyway. 1077 if (!Succ->getSinglePredecessor()) { 1078 BasicBlock::iterator BBI = BB->begin(); 1079 while (isa<PHINode>(*BBI)) { 1080 for (Use &U : BBI->uses()) { 1081 if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) { 1082 if (PN->getIncomingBlock(U) != BB) 1083 return false; 1084 } else { 1085 return false; 1086 } 1087 } 1088 ++BBI; 1089 } 1090 } 1091 1092 // We cannot fold the block if it's a branch to an already present callbr 1093 // successor because that creates duplicate successors. 1094 for (BasicBlock *PredBB : predecessors(BB)) { 1095 if (auto *CBI = dyn_cast<CallBrInst>(PredBB->getTerminator())) { 1096 if (Succ == CBI->getDefaultDest()) 1097 return false; 1098 for (unsigned i = 0, e = CBI->getNumIndirectDests(); i != e; ++i) 1099 if (Succ == CBI->getIndirectDest(i)) 1100 return false; 1101 } 1102 } 1103 1104 LLVM_DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB); 1105 1106 SmallVector<DominatorTree::UpdateType, 32> Updates; 1107 if (DTU) { 1108 // To avoid processing the same predecessor more than once. 1109 SmallPtrSet<BasicBlock *, 8> SeenPreds; 1110 // All predecessors of BB will be moved to Succ. 1111 SmallPtrSet<BasicBlock *, 8> PredsOfSucc(pred_begin(Succ), pred_end(Succ)); 1112 Updates.reserve(Updates.size() + 2 * pred_size(BB) + 1); 1113 for (auto *PredOfBB : predecessors(BB)) 1114 // This predecessor of BB may already have Succ as a successor. 1115 if (!PredsOfSucc.contains(PredOfBB)) 1116 if (SeenPreds.insert(PredOfBB).second) 1117 Updates.push_back({DominatorTree::Insert, PredOfBB, Succ}); 1118 SeenPreds.clear(); 1119 for (auto *PredOfBB : predecessors(BB)) 1120 if (SeenPreds.insert(PredOfBB).second) 1121 Updates.push_back({DominatorTree::Delete, PredOfBB, BB}); 1122 Updates.push_back({DominatorTree::Delete, BB, Succ}); 1123 } 1124 1125 if (isa<PHINode>(Succ->begin())) { 1126 // If there is more than one pred of succ, and there are PHI nodes in 1127 // the successor, then we need to add incoming edges for the PHI nodes 1128 // 1129 const PredBlockVector BBPreds(predecessors(BB)); 1130 1131 // Loop over all of the PHI nodes in the successor of BB. 1132 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { 1133 PHINode *PN = cast<PHINode>(I); 1134 1135 redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN); 1136 } 1137 } 1138 1139 if (Succ->getSinglePredecessor()) { 1140 // BB is the only predecessor of Succ, so Succ will end up with exactly 1141 // the same predecessors BB had. 1142 1143 // Copy over any phi, debug or lifetime instruction. 1144 BB->getTerminator()->eraseFromParent(); 1145 Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(), 1146 BB->getInstList()); 1147 } else { 1148 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) { 1149 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs. 1150 assert(PN->use_empty() && "There shouldn't be any uses here!"); 1151 PN->eraseFromParent(); 1152 } 1153 } 1154 1155 // If the unconditional branch we replaced contains llvm.loop metadata, we 1156 // add the metadata to the branch instructions in the predecessors. 1157 unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop"); 1158 Instruction *TI = BB->getTerminator(); 1159 if (TI) 1160 if (MDNode *LoopMD = TI->getMetadata(LoopMDKind)) 1161 for (BasicBlock *Pred : predecessors(BB)) 1162 Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD); 1163 1164 // Everything that jumped to BB now goes to Succ. 1165 BB->replaceAllUsesWith(Succ); 1166 if (!Succ->hasName()) Succ->takeName(BB); 1167 1168 // Clear the successor list of BB to match updates applying to DTU later. 1169 if (BB->getTerminator()) 1170 BB->getInstList().pop_back(); 1171 new UnreachableInst(BB->getContext(), BB); 1172 assert(succ_empty(BB) && "The successor list of BB isn't empty before " 1173 "applying corresponding DTU updates."); 1174 1175 if (DTU) 1176 DTU->applyUpdates(Updates); 1177 1178 DeleteDeadBlock(BB, DTU); 1179 1180 return true; 1181 } 1182 1183 static bool EliminateDuplicatePHINodesNaiveImpl(BasicBlock *BB) { 1184 // This implementation doesn't currently consider undef operands 1185 // specially. Theoretically, two phis which are identical except for 1186 // one having an undef where the other doesn't could be collapsed. 1187 1188 bool Changed = false; 1189 1190 // Examine each PHI. 1191 // Note that increment of I must *NOT* be in the iteration_expression, since 1192 // we don't want to immediately advance when we restart from the beginning. 1193 for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I);) { 1194 ++I; 1195 // Is there an identical PHI node in this basic block? 1196 // Note that we only look in the upper square's triangle, 1197 // we already checked that the lower triangle PHI's aren't identical. 1198 for (auto J = I; PHINode *DuplicatePN = dyn_cast<PHINode>(J); ++J) { 1199 if (!DuplicatePN->isIdenticalToWhenDefined(PN)) 1200 continue; 1201 // A duplicate. Replace this PHI with the base PHI. 1202 ++NumPHICSEs; 1203 DuplicatePN->replaceAllUsesWith(PN); 1204 DuplicatePN->eraseFromParent(); 1205 Changed = true; 1206 1207 // The RAUW can change PHIs that we already visited. 1208 I = BB->begin(); 1209 break; // Start over from the beginning. 1210 } 1211 } 1212 return Changed; 1213 } 1214 1215 static bool EliminateDuplicatePHINodesSetBasedImpl(BasicBlock *BB) { 1216 // This implementation doesn't currently consider undef operands 1217 // specially. Theoretically, two phis which are identical except for 1218 // one having an undef where the other doesn't could be collapsed. 1219 1220 struct PHIDenseMapInfo { 1221 static PHINode *getEmptyKey() { 1222 return DenseMapInfo<PHINode *>::getEmptyKey(); 1223 } 1224 1225 static PHINode *getTombstoneKey() { 1226 return DenseMapInfo<PHINode *>::getTombstoneKey(); 1227 } 1228 1229 static bool isSentinel(PHINode *PN) { 1230 return PN == getEmptyKey() || PN == getTombstoneKey(); 1231 } 1232 1233 // WARNING: this logic must be kept in sync with 1234 // Instruction::isIdenticalToWhenDefined()! 1235 static unsigned getHashValueImpl(PHINode *PN) { 1236 // Compute a hash value on the operands. Instcombine will likely have 1237 // sorted them, which helps expose duplicates, but we have to check all 1238 // the operands to be safe in case instcombine hasn't run. 1239 return static_cast<unsigned>(hash_combine( 1240 hash_combine_range(PN->value_op_begin(), PN->value_op_end()), 1241 hash_combine_range(PN->block_begin(), PN->block_end()))); 1242 } 1243 1244 static unsigned getHashValue(PHINode *PN) { 1245 #ifndef NDEBUG 1246 // If -phicse-debug-hash was specified, return a constant -- this 1247 // will force all hashing to collide, so we'll exhaustively search 1248 // the table for a match, and the assertion in isEqual will fire if 1249 // there's a bug causing equal keys to hash differently. 1250 if (PHICSEDebugHash) 1251 return 0; 1252 #endif 1253 return getHashValueImpl(PN); 1254 } 1255 1256 static bool isEqualImpl(PHINode *LHS, PHINode *RHS) { 1257 if (isSentinel(LHS) || isSentinel(RHS)) 1258 return LHS == RHS; 1259 return LHS->isIdenticalTo(RHS); 1260 } 1261 1262 static bool isEqual(PHINode *LHS, PHINode *RHS) { 1263 // These comparisons are nontrivial, so assert that equality implies 1264 // hash equality (DenseMap demands this as an invariant). 1265 bool Result = isEqualImpl(LHS, RHS); 1266 assert(!Result || (isSentinel(LHS) && LHS == RHS) || 1267 getHashValueImpl(LHS) == getHashValueImpl(RHS)); 1268 return Result; 1269 } 1270 }; 1271 1272 // Set of unique PHINodes. 1273 DenseSet<PHINode *, PHIDenseMapInfo> PHISet; 1274 PHISet.reserve(4 * PHICSENumPHISmallSize); 1275 1276 // Examine each PHI. 1277 bool Changed = false; 1278 for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) { 1279 auto Inserted = PHISet.insert(PN); 1280 if (!Inserted.second) { 1281 // A duplicate. Replace this PHI with its duplicate. 1282 ++NumPHICSEs; 1283 PN->replaceAllUsesWith(*Inserted.first); 1284 PN->eraseFromParent(); 1285 Changed = true; 1286 1287 // The RAUW can change PHIs that we already visited. Start over from the 1288 // beginning. 1289 PHISet.clear(); 1290 I = BB->begin(); 1291 } 1292 } 1293 1294 return Changed; 1295 } 1296 1297 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) { 1298 if ( 1299 #ifndef NDEBUG 1300 !PHICSEDebugHash && 1301 #endif 1302 hasNItemsOrLess(BB->phis(), PHICSENumPHISmallSize)) 1303 return EliminateDuplicatePHINodesNaiveImpl(BB); 1304 return EliminateDuplicatePHINodesSetBasedImpl(BB); 1305 } 1306 1307 /// If the specified pointer points to an object that we control, try to modify 1308 /// the object's alignment to PrefAlign. Returns a minimum known alignment of 1309 /// the value after the operation, which may be lower than PrefAlign. 1310 /// 1311 /// Increating value alignment isn't often possible though. If alignment is 1312 /// important, a more reliable approach is to simply align all global variables 1313 /// and allocation instructions to their preferred alignment from the beginning. 1314 static Align tryEnforceAlignment(Value *V, Align PrefAlign, 1315 const DataLayout &DL) { 1316 V = V->stripPointerCasts(); 1317 1318 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) { 1319 // TODO: Ideally, this function would not be called if PrefAlign is smaller 1320 // than the current alignment, as the known bits calculation should have 1321 // already taken it into account. However, this is not always the case, 1322 // as computeKnownBits() has a depth limit, while stripPointerCasts() 1323 // doesn't. 1324 Align CurrentAlign = AI->getAlign(); 1325 if (PrefAlign <= CurrentAlign) 1326 return CurrentAlign; 1327 1328 // If the preferred alignment is greater than the natural stack alignment 1329 // then don't round up. This avoids dynamic stack realignment. 1330 if (DL.exceedsNaturalStackAlignment(PrefAlign)) 1331 return CurrentAlign; 1332 AI->setAlignment(PrefAlign); 1333 return PrefAlign; 1334 } 1335 1336 if (auto *GO = dyn_cast<GlobalObject>(V)) { 1337 // TODO: as above, this shouldn't be necessary. 1338 Align CurrentAlign = GO->getPointerAlignment(DL); 1339 if (PrefAlign <= CurrentAlign) 1340 return CurrentAlign; 1341 1342 // If there is a large requested alignment and we can, bump up the alignment 1343 // of the global. If the memory we set aside for the global may not be the 1344 // memory used by the final program then it is impossible for us to reliably 1345 // enforce the preferred alignment. 1346 if (!GO->canIncreaseAlignment()) 1347 return CurrentAlign; 1348 1349 GO->setAlignment(PrefAlign); 1350 return PrefAlign; 1351 } 1352 1353 return Align(1); 1354 } 1355 1356 Align llvm::getOrEnforceKnownAlignment(Value *V, MaybeAlign PrefAlign, 1357 const DataLayout &DL, 1358 const Instruction *CxtI, 1359 AssumptionCache *AC, 1360 const DominatorTree *DT) { 1361 assert(V->getType()->isPointerTy() && 1362 "getOrEnforceKnownAlignment expects a pointer!"); 1363 1364 KnownBits Known = computeKnownBits(V, DL, 0, AC, CxtI, DT); 1365 unsigned TrailZ = Known.countMinTrailingZeros(); 1366 1367 // Avoid trouble with ridiculously large TrailZ values, such as 1368 // those computed from a null pointer. 1369 // LLVM doesn't support alignments larger than (1 << MaxAlignmentExponent). 1370 TrailZ = std::min(TrailZ, +Value::MaxAlignmentExponent); 1371 1372 Align Alignment = Align(1ull << std::min(Known.getBitWidth() - 1, TrailZ)); 1373 1374 if (PrefAlign && *PrefAlign > Alignment) 1375 Alignment = std::max(Alignment, tryEnforceAlignment(V, *PrefAlign, DL)); 1376 1377 // We don't need to make any adjustment. 1378 return Alignment; 1379 } 1380 1381 ///===---------------------------------------------------------------------===// 1382 /// Dbg Intrinsic utilities 1383 /// 1384 1385 /// See if there is a dbg.value intrinsic for DIVar for the PHI node. 1386 static bool PhiHasDebugValue(DILocalVariable *DIVar, 1387 DIExpression *DIExpr, 1388 PHINode *APN) { 1389 // Since we can't guarantee that the original dbg.declare intrinsic 1390 // is removed by LowerDbgDeclare(), we need to make sure that we are 1391 // not inserting the same dbg.value intrinsic over and over. 1392 SmallVector<DbgValueInst *, 1> DbgValues; 1393 findDbgValues(DbgValues, APN); 1394 for (auto *DVI : DbgValues) { 1395 assert(is_contained(DVI->getValues(), APN)); 1396 if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr)) 1397 return true; 1398 } 1399 return false; 1400 } 1401 1402 /// Check if the alloc size of \p ValTy is large enough to cover the variable 1403 /// (or fragment of the variable) described by \p DII. 1404 /// 1405 /// This is primarily intended as a helper for the different 1406 /// ConvertDebugDeclareToDebugValue functions. The dbg.declare/dbg.addr that is 1407 /// converted describes an alloca'd variable, so we need to use the 1408 /// alloc size of the value when doing the comparison. E.g. an i1 value will be 1409 /// identified as covering an n-bit fragment, if the store size of i1 is at 1410 /// least n bits. 1411 static bool valueCoversEntireFragment(Type *ValTy, DbgVariableIntrinsic *DII) { 1412 const DataLayout &DL = DII->getModule()->getDataLayout(); 1413 TypeSize ValueSize = DL.getTypeAllocSizeInBits(ValTy); 1414 if (Optional<uint64_t> FragmentSize = DII->getFragmentSizeInBits()) { 1415 assert(!ValueSize.isScalable() && 1416 "Fragments don't work on scalable types."); 1417 return ValueSize.getFixedSize() >= *FragmentSize; 1418 } 1419 // We can't always calculate the size of the DI variable (e.g. if it is a 1420 // VLA). Try to use the size of the alloca that the dbg intrinsic describes 1421 // intead. 1422 if (DII->isAddressOfVariable()) { 1423 // DII should have exactly 1 location when it is an address. 1424 assert(DII->getNumVariableLocationOps() == 1 && 1425 "address of variable must have exactly 1 location operand."); 1426 if (auto *AI = 1427 dyn_cast_or_null<AllocaInst>(DII->getVariableLocationOp(0))) { 1428 if (Optional<TypeSize> FragmentSize = AI->getAllocationSizeInBits(DL)) { 1429 return TypeSize::isKnownGE(ValueSize, *FragmentSize); 1430 } 1431 } 1432 } 1433 // Could not determine size of variable. Conservatively return false. 1434 return false; 1435 } 1436 1437 /// Produce a DebugLoc to use for each dbg.declare/inst pair that are promoted 1438 /// to a dbg.value. Because no machine insts can come from debug intrinsics, 1439 /// only the scope and inlinedAt is significant. Zero line numbers are used in 1440 /// case this DebugLoc leaks into any adjacent instructions. 1441 static DebugLoc getDebugValueLoc(DbgVariableIntrinsic *DII, Instruction *Src) { 1442 // Original dbg.declare must have a location. 1443 const DebugLoc &DeclareLoc = DII->getDebugLoc(); 1444 MDNode *Scope = DeclareLoc.getScope(); 1445 DILocation *InlinedAt = DeclareLoc.getInlinedAt(); 1446 // Produce an unknown location with the correct scope / inlinedAt fields. 1447 return DILocation::get(DII->getContext(), 0, 0, Scope, InlinedAt); 1448 } 1449 1450 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value 1451 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic. 1452 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, 1453 StoreInst *SI, DIBuilder &Builder) { 1454 assert(DII->isAddressOfVariable()); 1455 auto *DIVar = DII->getVariable(); 1456 assert(DIVar && "Missing variable"); 1457 auto *DIExpr = DII->getExpression(); 1458 Value *DV = SI->getValueOperand(); 1459 1460 DebugLoc NewLoc = getDebugValueLoc(DII, SI); 1461 1462 if (!valueCoversEntireFragment(DV->getType(), DII)) { 1463 // FIXME: If storing to a part of the variable described by the dbg.declare, 1464 // then we want to insert a dbg.value for the corresponding fragment. 1465 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " 1466 << *DII << '\n'); 1467 // For now, when there is a store to parts of the variable (but we do not 1468 // know which part) we insert an dbg.value intrinsic to indicate that we 1469 // know nothing about the variable's content. 1470 DV = UndefValue::get(DV->getType()); 1471 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI); 1472 return; 1473 } 1474 1475 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI); 1476 } 1477 1478 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value 1479 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic. 1480 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, 1481 LoadInst *LI, DIBuilder &Builder) { 1482 auto *DIVar = DII->getVariable(); 1483 auto *DIExpr = DII->getExpression(); 1484 assert(DIVar && "Missing variable"); 1485 1486 if (!valueCoversEntireFragment(LI->getType(), DII)) { 1487 // FIXME: If only referring to a part of the variable described by the 1488 // dbg.declare, then we want to insert a dbg.value for the corresponding 1489 // fragment. 1490 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " 1491 << *DII << '\n'); 1492 return; 1493 } 1494 1495 DebugLoc NewLoc = getDebugValueLoc(DII, nullptr); 1496 1497 // We are now tracking the loaded value instead of the address. In the 1498 // future if multi-location support is added to the IR, it might be 1499 // preferable to keep tracking both the loaded value and the original 1500 // address in case the alloca can not be elided. 1501 Instruction *DbgValue = Builder.insertDbgValueIntrinsic( 1502 LI, DIVar, DIExpr, NewLoc, (Instruction *)nullptr); 1503 DbgValue->insertAfter(LI); 1504 } 1505 1506 /// Inserts a llvm.dbg.value intrinsic after a phi that has an associated 1507 /// llvm.dbg.declare or llvm.dbg.addr intrinsic. 1508 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII, 1509 PHINode *APN, DIBuilder &Builder) { 1510 auto *DIVar = DII->getVariable(); 1511 auto *DIExpr = DII->getExpression(); 1512 assert(DIVar && "Missing variable"); 1513 1514 if (PhiHasDebugValue(DIVar, DIExpr, APN)) 1515 return; 1516 1517 if (!valueCoversEntireFragment(APN->getType(), DII)) { 1518 // FIXME: If only referring to a part of the variable described by the 1519 // dbg.declare, then we want to insert a dbg.value for the corresponding 1520 // fragment. 1521 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " 1522 << *DII << '\n'); 1523 return; 1524 } 1525 1526 BasicBlock *BB = APN->getParent(); 1527 auto InsertionPt = BB->getFirstInsertionPt(); 1528 1529 DebugLoc NewLoc = getDebugValueLoc(DII, nullptr); 1530 1531 // The block may be a catchswitch block, which does not have a valid 1532 // insertion point. 1533 // FIXME: Insert dbg.value markers in the successors when appropriate. 1534 if (InsertionPt != BB->end()) 1535 Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, NewLoc, &*InsertionPt); 1536 } 1537 1538 /// Determine whether this alloca is either a VLA or an array. 1539 static bool isArray(AllocaInst *AI) { 1540 return AI->isArrayAllocation() || 1541 (AI->getAllocatedType() && AI->getAllocatedType()->isArrayTy()); 1542 } 1543 1544 /// Determine whether this alloca is a structure. 1545 static bool isStructure(AllocaInst *AI) { 1546 return AI->getAllocatedType() && AI->getAllocatedType()->isStructTy(); 1547 } 1548 1549 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set 1550 /// of llvm.dbg.value intrinsics. 1551 bool llvm::LowerDbgDeclare(Function &F) { 1552 bool Changed = false; 1553 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false); 1554 SmallVector<DbgDeclareInst *, 4> Dbgs; 1555 for (auto &FI : F) 1556 for (Instruction &BI : FI) 1557 if (auto DDI = dyn_cast<DbgDeclareInst>(&BI)) 1558 Dbgs.push_back(DDI); 1559 1560 if (Dbgs.empty()) 1561 return Changed; 1562 1563 for (auto &I : Dbgs) { 1564 DbgDeclareInst *DDI = I; 1565 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress()); 1566 // If this is an alloca for a scalar variable, insert a dbg.value 1567 // at each load and store to the alloca and erase the dbg.declare. 1568 // The dbg.values allow tracking a variable even if it is not 1569 // stored on the stack, while the dbg.declare can only describe 1570 // the stack slot (and at a lexical-scope granularity). Later 1571 // passes will attempt to elide the stack slot. 1572 if (!AI || isArray(AI) || isStructure(AI)) 1573 continue; 1574 1575 // A volatile load/store means that the alloca can't be elided anyway. 1576 if (llvm::any_of(AI->users(), [](User *U) -> bool { 1577 if (LoadInst *LI = dyn_cast<LoadInst>(U)) 1578 return LI->isVolatile(); 1579 if (StoreInst *SI = dyn_cast<StoreInst>(U)) 1580 return SI->isVolatile(); 1581 return false; 1582 })) 1583 continue; 1584 1585 SmallVector<const Value *, 8> WorkList; 1586 WorkList.push_back(AI); 1587 while (!WorkList.empty()) { 1588 const Value *V = WorkList.pop_back_val(); 1589 for (auto &AIUse : V->uses()) { 1590 User *U = AIUse.getUser(); 1591 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1592 if (AIUse.getOperandNo() == 1) 1593 ConvertDebugDeclareToDebugValue(DDI, SI, DIB); 1594 } else if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1595 ConvertDebugDeclareToDebugValue(DDI, LI, DIB); 1596 } else if (CallInst *CI = dyn_cast<CallInst>(U)) { 1597 // This is a call by-value or some other instruction that takes a 1598 // pointer to the variable. Insert a *value* intrinsic that describes 1599 // the variable by dereferencing the alloca. 1600 if (!CI->isLifetimeStartOrEnd()) { 1601 DebugLoc NewLoc = getDebugValueLoc(DDI, nullptr); 1602 auto *DerefExpr = 1603 DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref); 1604 DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr, 1605 NewLoc, CI); 1606 } 1607 } else if (BitCastInst *BI = dyn_cast<BitCastInst>(U)) { 1608 if (BI->getType()->isPointerTy()) 1609 WorkList.push_back(BI); 1610 } 1611 } 1612 } 1613 DDI->eraseFromParent(); 1614 Changed = true; 1615 } 1616 1617 if (Changed) 1618 for (BasicBlock &BB : F) 1619 RemoveRedundantDbgInstrs(&BB); 1620 1621 return Changed; 1622 } 1623 1624 /// Propagate dbg.value intrinsics through the newly inserted PHIs. 1625 void llvm::insertDebugValuesForPHIs(BasicBlock *BB, 1626 SmallVectorImpl<PHINode *> &InsertedPHIs) { 1627 assert(BB && "No BasicBlock to clone dbg.value(s) from."); 1628 if (InsertedPHIs.size() == 0) 1629 return; 1630 1631 // Map existing PHI nodes to their dbg.values. 1632 ValueToValueMapTy DbgValueMap; 1633 for (auto &I : *BB) { 1634 if (auto DbgII = dyn_cast<DbgVariableIntrinsic>(&I)) { 1635 for (Value *V : DbgII->location_ops()) 1636 if (auto *Loc = dyn_cast_or_null<PHINode>(V)) 1637 DbgValueMap.insert({Loc, DbgII}); 1638 } 1639 } 1640 if (DbgValueMap.size() == 0) 1641 return; 1642 1643 // Map a pair of the destination BB and old dbg.value to the new dbg.value, 1644 // so that if a dbg.value is being rewritten to use more than one of the 1645 // inserted PHIs in the same destination BB, we can update the same dbg.value 1646 // with all the new PHIs instead of creating one copy for each. 1647 MapVector<std::pair<BasicBlock *, DbgVariableIntrinsic *>, 1648 DbgVariableIntrinsic *> 1649 NewDbgValueMap; 1650 // Then iterate through the new PHIs and look to see if they use one of the 1651 // previously mapped PHIs. If so, create a new dbg.value intrinsic that will 1652 // propagate the info through the new PHI. If we use more than one new PHI in 1653 // a single destination BB with the same old dbg.value, merge the updates so 1654 // that we get a single new dbg.value with all the new PHIs. 1655 for (auto PHI : InsertedPHIs) { 1656 BasicBlock *Parent = PHI->getParent(); 1657 // Avoid inserting an intrinsic into an EH block. 1658 if (Parent->getFirstNonPHI()->isEHPad()) 1659 continue; 1660 for (auto VI : PHI->operand_values()) { 1661 auto V = DbgValueMap.find(VI); 1662 if (V != DbgValueMap.end()) { 1663 auto *DbgII = cast<DbgVariableIntrinsic>(V->second); 1664 auto NewDI = NewDbgValueMap.find({Parent, DbgII}); 1665 if (NewDI == NewDbgValueMap.end()) { 1666 auto *NewDbgII = cast<DbgVariableIntrinsic>(DbgII->clone()); 1667 NewDI = NewDbgValueMap.insert({{Parent, DbgII}, NewDbgII}).first; 1668 } 1669 DbgVariableIntrinsic *NewDbgII = NewDI->second; 1670 // If PHI contains VI as an operand more than once, we may 1671 // replaced it in NewDbgII; confirm that it is present. 1672 if (is_contained(NewDbgII->location_ops(), VI)) 1673 NewDbgII->replaceVariableLocationOp(VI, PHI); 1674 } 1675 } 1676 } 1677 // Insert thew new dbg.values into their destination blocks. 1678 for (auto DI : NewDbgValueMap) { 1679 BasicBlock *Parent = DI.first.first; 1680 auto *NewDbgII = DI.second; 1681 auto InsertionPt = Parent->getFirstInsertionPt(); 1682 assert(InsertionPt != Parent->end() && "Ill-formed basic block"); 1683 NewDbgII->insertBefore(&*InsertionPt); 1684 } 1685 } 1686 1687 bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress, 1688 DIBuilder &Builder, uint8_t DIExprFlags, 1689 int Offset) { 1690 auto DbgAddrs = FindDbgAddrUses(Address); 1691 for (DbgVariableIntrinsic *DII : DbgAddrs) { 1692 const DebugLoc &Loc = DII->getDebugLoc(); 1693 auto *DIVar = DII->getVariable(); 1694 auto *DIExpr = DII->getExpression(); 1695 assert(DIVar && "Missing variable"); 1696 DIExpr = DIExpression::prepend(DIExpr, DIExprFlags, Offset); 1697 // Insert llvm.dbg.declare immediately before DII, and remove old 1698 // llvm.dbg.declare. 1699 Builder.insertDeclare(NewAddress, DIVar, DIExpr, Loc, DII); 1700 DII->eraseFromParent(); 1701 } 1702 return !DbgAddrs.empty(); 1703 } 1704 1705 static void replaceOneDbgValueForAlloca(DbgValueInst *DVI, Value *NewAddress, 1706 DIBuilder &Builder, int Offset) { 1707 const DebugLoc &Loc = DVI->getDebugLoc(); 1708 auto *DIVar = DVI->getVariable(); 1709 auto *DIExpr = DVI->getExpression(); 1710 assert(DIVar && "Missing variable"); 1711 1712 // This is an alloca-based llvm.dbg.value. The first thing it should do with 1713 // the alloca pointer is dereference it. Otherwise we don't know how to handle 1714 // it and give up. 1715 if (!DIExpr || DIExpr->getNumElements() < 1 || 1716 DIExpr->getElement(0) != dwarf::DW_OP_deref) 1717 return; 1718 1719 // Insert the offset before the first deref. 1720 // We could just change the offset argument of dbg.value, but it's unsigned... 1721 if (Offset) 1722 DIExpr = DIExpression::prepend(DIExpr, 0, Offset); 1723 1724 Builder.insertDbgValueIntrinsic(NewAddress, DIVar, DIExpr, Loc, DVI); 1725 DVI->eraseFromParent(); 1726 } 1727 1728 void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress, 1729 DIBuilder &Builder, int Offset) { 1730 if (auto *L = LocalAsMetadata::getIfExists(AI)) 1731 if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L)) 1732 for (Use &U : llvm::make_early_inc_range(MDV->uses())) 1733 if (auto *DVI = dyn_cast<DbgValueInst>(U.getUser())) 1734 replaceOneDbgValueForAlloca(DVI, NewAllocaAddress, Builder, Offset); 1735 } 1736 1737 /// Where possible to salvage debug information for \p I do so 1738 /// and return True. If not possible mark undef and return False. 1739 void llvm::salvageDebugInfo(Instruction &I) { 1740 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; 1741 findDbgUsers(DbgUsers, &I); 1742 salvageDebugInfoForDbgValues(I, DbgUsers); 1743 } 1744 1745 void llvm::salvageDebugInfoForDbgValues( 1746 Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) { 1747 // These are arbitrary chosen limits on the maximum number of values and the 1748 // maximum size of a debug expression we can salvage up to, used for 1749 // performance reasons. 1750 const unsigned MaxDebugArgs = 16; 1751 const unsigned MaxExpressionSize = 128; 1752 bool Salvaged = false; 1753 1754 for (auto *DII : DbgUsers) { 1755 // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they 1756 // are implicitly pointing out the value as a DWARF memory location 1757 // description. 1758 bool StackValue = isa<DbgValueInst>(DII); 1759 auto DIILocation = DII->location_ops(); 1760 assert( 1761 is_contained(DIILocation, &I) && 1762 "DbgVariableIntrinsic must use salvaged instruction as its location"); 1763 SmallVector<Value *, 4> AdditionalValues; 1764 // `I` may appear more than once in DII's location ops, and each use of `I` 1765 // must be updated in the DIExpression and potentially have additional 1766 // values added; thus we call salvageDebugInfoImpl for each `I` instance in 1767 // DIILocation. 1768 Value *Op0 = nullptr; 1769 DIExpression *SalvagedExpr = DII->getExpression(); 1770 auto LocItr = find(DIILocation, &I); 1771 while (SalvagedExpr && LocItr != DIILocation.end()) { 1772 SmallVector<uint64_t, 16> Ops; 1773 unsigned LocNo = std::distance(DIILocation.begin(), LocItr); 1774 uint64_t CurrentLocOps = SalvagedExpr->getNumLocationOperands(); 1775 Op0 = salvageDebugInfoImpl(I, CurrentLocOps, Ops, AdditionalValues); 1776 if (!Op0) 1777 break; 1778 SalvagedExpr = 1779 DIExpression::appendOpsToArg(SalvagedExpr, Ops, LocNo, StackValue); 1780 LocItr = std::find(++LocItr, DIILocation.end(), &I); 1781 } 1782 // salvageDebugInfoImpl should fail on examining the first element of 1783 // DbgUsers, or none of them. 1784 if (!Op0) 1785 break; 1786 1787 DII->replaceVariableLocationOp(&I, Op0); 1788 bool IsValidSalvageExpr = SalvagedExpr->getNumElements() <= MaxExpressionSize; 1789 if (AdditionalValues.empty() && IsValidSalvageExpr) { 1790 DII->setExpression(SalvagedExpr); 1791 } else if (isa<DbgValueInst>(DII) && IsValidSalvageExpr && 1792 DII->getNumVariableLocationOps() + AdditionalValues.size() <= 1793 MaxDebugArgs) { 1794 DII->addVariableLocationOps(AdditionalValues, SalvagedExpr); 1795 } else { 1796 // Do not salvage using DIArgList for dbg.addr/dbg.declare, as it is 1797 // currently only valid for stack value expressions. 1798 // Also do not salvage if the resulting DIArgList would contain an 1799 // unreasonably large number of values. 1800 Value *Undef = UndefValue::get(I.getOperand(0)->getType()); 1801 DII->replaceVariableLocationOp(I.getOperand(0), Undef); 1802 } 1803 LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n'); 1804 Salvaged = true; 1805 } 1806 1807 if (Salvaged) 1808 return; 1809 1810 for (auto *DII : DbgUsers) { 1811 Value *Undef = UndefValue::get(I.getType()); 1812 DII->replaceVariableLocationOp(&I, Undef); 1813 } 1814 } 1815 1816 Value *getSalvageOpsForGEP(GetElementPtrInst *GEP, const DataLayout &DL, 1817 uint64_t CurrentLocOps, 1818 SmallVectorImpl<uint64_t> &Opcodes, 1819 SmallVectorImpl<Value *> &AdditionalValues) { 1820 unsigned BitWidth = DL.getIndexSizeInBits(GEP->getPointerAddressSpace()); 1821 // Rewrite a GEP into a DIExpression. 1822 MapVector<Value *, APInt> VariableOffsets; 1823 APInt ConstantOffset(BitWidth, 0); 1824 if (!GEP->collectOffset(DL, BitWidth, VariableOffsets, ConstantOffset)) 1825 return nullptr; 1826 if (!VariableOffsets.empty() && !CurrentLocOps) { 1827 Opcodes.insert(Opcodes.begin(), {dwarf::DW_OP_LLVM_arg, 0}); 1828 CurrentLocOps = 1; 1829 } 1830 for (auto Offset : VariableOffsets) { 1831 AdditionalValues.push_back(Offset.first); 1832 assert(Offset.second.isStrictlyPositive() && 1833 "Expected strictly positive multiplier for offset."); 1834 Opcodes.append({dwarf::DW_OP_LLVM_arg, CurrentLocOps++, dwarf::DW_OP_constu, 1835 Offset.second.getZExtValue(), dwarf::DW_OP_mul, 1836 dwarf::DW_OP_plus}); 1837 } 1838 DIExpression::appendOffset(Opcodes, ConstantOffset.getSExtValue()); 1839 return GEP->getOperand(0); 1840 } 1841 1842 uint64_t getDwarfOpForBinOp(Instruction::BinaryOps Opcode) { 1843 switch (Opcode) { 1844 case Instruction::Add: 1845 return dwarf::DW_OP_plus; 1846 case Instruction::Sub: 1847 return dwarf::DW_OP_minus; 1848 case Instruction::Mul: 1849 return dwarf::DW_OP_mul; 1850 case Instruction::SDiv: 1851 return dwarf::DW_OP_div; 1852 case Instruction::SRem: 1853 return dwarf::DW_OP_mod; 1854 case Instruction::Or: 1855 return dwarf::DW_OP_or; 1856 case Instruction::And: 1857 return dwarf::DW_OP_and; 1858 case Instruction::Xor: 1859 return dwarf::DW_OP_xor; 1860 case Instruction::Shl: 1861 return dwarf::DW_OP_shl; 1862 case Instruction::LShr: 1863 return dwarf::DW_OP_shr; 1864 case Instruction::AShr: 1865 return dwarf::DW_OP_shra; 1866 default: 1867 // TODO: Salvage from each kind of binop we know about. 1868 return 0; 1869 } 1870 } 1871 1872 Value *getSalvageOpsForBinOp(BinaryOperator *BI, uint64_t CurrentLocOps, 1873 SmallVectorImpl<uint64_t> &Opcodes, 1874 SmallVectorImpl<Value *> &AdditionalValues) { 1875 // Handle binary operations with constant integer operands as a special case. 1876 auto *ConstInt = dyn_cast<ConstantInt>(BI->getOperand(1)); 1877 // Values wider than 64 bits cannot be represented within a DIExpression. 1878 if (ConstInt && ConstInt->getBitWidth() > 64) 1879 return nullptr; 1880 1881 Instruction::BinaryOps BinOpcode = BI->getOpcode(); 1882 // Push any Constant Int operand onto the expression stack. 1883 if (ConstInt) { 1884 uint64_t Val = ConstInt->getSExtValue(); 1885 // Add or Sub Instructions with a constant operand can potentially be 1886 // simplified. 1887 if (BinOpcode == Instruction::Add || BinOpcode == Instruction::Sub) { 1888 uint64_t Offset = BinOpcode == Instruction::Add ? Val : -int64_t(Val); 1889 DIExpression::appendOffset(Opcodes, Offset); 1890 return BI->getOperand(0); 1891 } 1892 Opcodes.append({dwarf::DW_OP_constu, Val}); 1893 } else { 1894 if (!CurrentLocOps) { 1895 Opcodes.append({dwarf::DW_OP_LLVM_arg, 0}); 1896 CurrentLocOps = 1; 1897 } 1898 Opcodes.append({dwarf::DW_OP_LLVM_arg, CurrentLocOps}); 1899 AdditionalValues.push_back(BI->getOperand(1)); 1900 } 1901 1902 // Add salvaged binary operator to expression stack, if it has a valid 1903 // representation in a DIExpression. 1904 uint64_t DwarfBinOp = getDwarfOpForBinOp(BinOpcode); 1905 if (!DwarfBinOp) 1906 return nullptr; 1907 Opcodes.push_back(DwarfBinOp); 1908 return BI->getOperand(0); 1909 } 1910 1911 Value *llvm::salvageDebugInfoImpl(Instruction &I, uint64_t CurrentLocOps, 1912 SmallVectorImpl<uint64_t> &Ops, 1913 SmallVectorImpl<Value *> &AdditionalValues) { 1914 auto &M = *I.getModule(); 1915 auto &DL = M.getDataLayout(); 1916 1917 if (auto *CI = dyn_cast<CastInst>(&I)) { 1918 Value *FromValue = CI->getOperand(0); 1919 // No-op casts are irrelevant for debug info. 1920 if (CI->isNoopCast(DL)) { 1921 return FromValue; 1922 } 1923 1924 Type *Type = CI->getType(); 1925 if (Type->isPointerTy()) 1926 Type = DL.getIntPtrType(Type); 1927 // Casts other than Trunc, SExt, or ZExt to scalar types cannot be salvaged. 1928 if (Type->isVectorTy() || 1929 !(isa<TruncInst>(&I) || isa<SExtInst>(&I) || isa<ZExtInst>(&I) || 1930 isa<IntToPtrInst>(&I) || isa<PtrToIntInst>(&I))) 1931 return nullptr; 1932 1933 llvm::Type *FromType = FromValue->getType(); 1934 if (FromType->isPointerTy()) 1935 FromType = DL.getIntPtrType(FromType); 1936 1937 unsigned FromTypeBitSize = FromType->getScalarSizeInBits(); 1938 unsigned ToTypeBitSize = Type->getScalarSizeInBits(); 1939 1940 auto ExtOps = DIExpression::getExtOps(FromTypeBitSize, ToTypeBitSize, 1941 isa<SExtInst>(&I)); 1942 Ops.append(ExtOps.begin(), ExtOps.end()); 1943 return FromValue; 1944 } 1945 1946 if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) 1947 return getSalvageOpsForGEP(GEP, DL, CurrentLocOps, Ops, AdditionalValues); 1948 if (auto *BI = dyn_cast<BinaryOperator>(&I)) 1949 return getSalvageOpsForBinOp(BI, CurrentLocOps, Ops, AdditionalValues); 1950 1951 // *Not* to do: we should not attempt to salvage load instructions, 1952 // because the validity and lifetime of a dbg.value containing 1953 // DW_OP_deref becomes difficult to analyze. See PR40628 for examples. 1954 return nullptr; 1955 } 1956 1957 /// A replacement for a dbg.value expression. 1958 using DbgValReplacement = Optional<DIExpression *>; 1959 1960 /// Point debug users of \p From to \p To using exprs given by \p RewriteExpr, 1961 /// possibly moving/undefing users to prevent use-before-def. Returns true if 1962 /// changes are made. 1963 static bool rewriteDebugUsers( 1964 Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT, 1965 function_ref<DbgValReplacement(DbgVariableIntrinsic &DII)> RewriteExpr) { 1966 // Find debug users of From. 1967 SmallVector<DbgVariableIntrinsic *, 1> Users; 1968 findDbgUsers(Users, &From); 1969 if (Users.empty()) 1970 return false; 1971 1972 // Prevent use-before-def of To. 1973 bool Changed = false; 1974 SmallPtrSet<DbgVariableIntrinsic *, 1> UndefOrSalvage; 1975 if (isa<Instruction>(&To)) { 1976 bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint; 1977 1978 for (auto *DII : Users) { 1979 // It's common to see a debug user between From and DomPoint. Move it 1980 // after DomPoint to preserve the variable update without any reordering. 1981 if (DomPointAfterFrom && DII->getNextNonDebugInstruction() == &DomPoint) { 1982 LLVM_DEBUG(dbgs() << "MOVE: " << *DII << '\n'); 1983 DII->moveAfter(&DomPoint); 1984 Changed = true; 1985 1986 // Users which otherwise aren't dominated by the replacement value must 1987 // be salvaged or deleted. 1988 } else if (!DT.dominates(&DomPoint, DII)) { 1989 UndefOrSalvage.insert(DII); 1990 } 1991 } 1992 } 1993 1994 // Update debug users without use-before-def risk. 1995 for (auto *DII : Users) { 1996 if (UndefOrSalvage.count(DII)) 1997 continue; 1998 1999 DbgValReplacement DVR = RewriteExpr(*DII); 2000 if (!DVR) 2001 continue; 2002 2003 DII->replaceVariableLocationOp(&From, &To); 2004 DII->setExpression(*DVR); 2005 LLVM_DEBUG(dbgs() << "REWRITE: " << *DII << '\n'); 2006 Changed = true; 2007 } 2008 2009 if (!UndefOrSalvage.empty()) { 2010 // Try to salvage the remaining debug users. 2011 salvageDebugInfo(From); 2012 Changed = true; 2013 } 2014 2015 return Changed; 2016 } 2017 2018 /// Check if a bitcast between a value of type \p FromTy to type \p ToTy would 2019 /// losslessly preserve the bits and semantics of the value. This predicate is 2020 /// symmetric, i.e swapping \p FromTy and \p ToTy should give the same result. 2021 /// 2022 /// Note that Type::canLosslesslyBitCastTo is not suitable here because it 2023 /// allows semantically unequivalent bitcasts, such as <2 x i64> -> <4 x i32>, 2024 /// and also does not allow lossless pointer <-> integer conversions. 2025 static bool isBitCastSemanticsPreserving(const DataLayout &DL, Type *FromTy, 2026 Type *ToTy) { 2027 // Trivially compatible types. 2028 if (FromTy == ToTy) 2029 return true; 2030 2031 // Handle compatible pointer <-> integer conversions. 2032 if (FromTy->isIntOrPtrTy() && ToTy->isIntOrPtrTy()) { 2033 bool SameSize = DL.getTypeSizeInBits(FromTy) == DL.getTypeSizeInBits(ToTy); 2034 bool LosslessConversion = !DL.isNonIntegralPointerType(FromTy) && 2035 !DL.isNonIntegralPointerType(ToTy); 2036 return SameSize && LosslessConversion; 2037 } 2038 2039 // TODO: This is not exhaustive. 2040 return false; 2041 } 2042 2043 bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To, 2044 Instruction &DomPoint, DominatorTree &DT) { 2045 // Exit early if From has no debug users. 2046 if (!From.isUsedByMetadata()) 2047 return false; 2048 2049 assert(&From != &To && "Can't replace something with itself"); 2050 2051 Type *FromTy = From.getType(); 2052 Type *ToTy = To.getType(); 2053 2054 auto Identity = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement { 2055 return DII.getExpression(); 2056 }; 2057 2058 // Handle no-op conversions. 2059 Module &M = *From.getModule(); 2060 const DataLayout &DL = M.getDataLayout(); 2061 if (isBitCastSemanticsPreserving(DL, FromTy, ToTy)) 2062 return rewriteDebugUsers(From, To, DomPoint, DT, Identity); 2063 2064 // Handle integer-to-integer widening and narrowing. 2065 // FIXME: Use DW_OP_convert when it's available everywhere. 2066 if (FromTy->isIntegerTy() && ToTy->isIntegerTy()) { 2067 uint64_t FromBits = FromTy->getPrimitiveSizeInBits(); 2068 uint64_t ToBits = ToTy->getPrimitiveSizeInBits(); 2069 assert(FromBits != ToBits && "Unexpected no-op conversion"); 2070 2071 // When the width of the result grows, assume that a debugger will only 2072 // access the low `FromBits` bits when inspecting the source variable. 2073 if (FromBits < ToBits) 2074 return rewriteDebugUsers(From, To, DomPoint, DT, Identity); 2075 2076 // The width of the result has shrunk. Use sign/zero extension to describe 2077 // the source variable's high bits. 2078 auto SignOrZeroExt = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement { 2079 DILocalVariable *Var = DII.getVariable(); 2080 2081 // Without knowing signedness, sign/zero extension isn't possible. 2082 auto Signedness = Var->getSignedness(); 2083 if (!Signedness) 2084 return None; 2085 2086 bool Signed = *Signedness == DIBasicType::Signedness::Signed; 2087 return DIExpression::appendExt(DII.getExpression(), ToBits, FromBits, 2088 Signed); 2089 }; 2090 return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt); 2091 } 2092 2093 // TODO: Floating-point conversions, vectors. 2094 return false; 2095 } 2096 2097 std::pair<unsigned, unsigned> 2098 llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) { 2099 unsigned NumDeadInst = 0; 2100 unsigned NumDeadDbgInst = 0; 2101 // Delete the instructions backwards, as it has a reduced likelihood of 2102 // having to update as many def-use and use-def chains. 2103 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. 2104 while (EndInst != &BB->front()) { 2105 // Delete the next to last instruction. 2106 Instruction *Inst = &*--EndInst->getIterator(); 2107 if (!Inst->use_empty() && !Inst->getType()->isTokenTy()) 2108 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); 2109 if (Inst->isEHPad() || Inst->getType()->isTokenTy()) { 2110 EndInst = Inst; 2111 continue; 2112 } 2113 if (isa<DbgInfoIntrinsic>(Inst)) 2114 ++NumDeadDbgInst; 2115 else 2116 ++NumDeadInst; 2117 Inst->eraseFromParent(); 2118 } 2119 return {NumDeadInst, NumDeadDbgInst}; 2120 } 2121 2122 unsigned llvm::changeToUnreachable(Instruction *I, bool PreserveLCSSA, 2123 DomTreeUpdater *DTU, 2124 MemorySSAUpdater *MSSAU) { 2125 BasicBlock *BB = I->getParent(); 2126 2127 if (MSSAU) 2128 MSSAU->changeToUnreachable(I); 2129 2130 SmallSet<BasicBlock *, 8> UniqueSuccessors; 2131 2132 // Loop over all of the successors, removing BB's entry from any PHI 2133 // nodes. 2134 for (BasicBlock *Successor : successors(BB)) { 2135 Successor->removePredecessor(BB, PreserveLCSSA); 2136 if (DTU) 2137 UniqueSuccessors.insert(Successor); 2138 } 2139 auto *UI = new UnreachableInst(I->getContext(), I); 2140 UI->setDebugLoc(I->getDebugLoc()); 2141 2142 // All instructions after this are dead. 2143 unsigned NumInstrsRemoved = 0; 2144 BasicBlock::iterator BBI = I->getIterator(), BBE = BB->end(); 2145 while (BBI != BBE) { 2146 if (!BBI->use_empty()) 2147 BBI->replaceAllUsesWith(UndefValue::get(BBI->getType())); 2148 BB->getInstList().erase(BBI++); 2149 ++NumInstrsRemoved; 2150 } 2151 if (DTU) { 2152 SmallVector<DominatorTree::UpdateType, 8> Updates; 2153 Updates.reserve(UniqueSuccessors.size()); 2154 for (BasicBlock *UniqueSuccessor : UniqueSuccessors) 2155 Updates.push_back({DominatorTree::Delete, BB, UniqueSuccessor}); 2156 DTU->applyUpdates(Updates); 2157 } 2158 return NumInstrsRemoved; 2159 } 2160 2161 CallInst *llvm::createCallMatchingInvoke(InvokeInst *II) { 2162 SmallVector<Value *, 8> Args(II->args()); 2163 SmallVector<OperandBundleDef, 1> OpBundles; 2164 II->getOperandBundlesAsDefs(OpBundles); 2165 CallInst *NewCall = CallInst::Create(II->getFunctionType(), 2166 II->getCalledOperand(), Args, OpBundles); 2167 NewCall->setCallingConv(II->getCallingConv()); 2168 NewCall->setAttributes(II->getAttributes()); 2169 NewCall->setDebugLoc(II->getDebugLoc()); 2170 NewCall->copyMetadata(*II); 2171 2172 // If the invoke had profile metadata, try converting them for CallInst. 2173 uint64_t TotalWeight; 2174 if (NewCall->extractProfTotalWeight(TotalWeight)) { 2175 // Set the total weight if it fits into i32, otherwise reset. 2176 MDBuilder MDB(NewCall->getContext()); 2177 auto NewWeights = uint32_t(TotalWeight) != TotalWeight 2178 ? nullptr 2179 : MDB.createBranchWeights({uint32_t(TotalWeight)}); 2180 NewCall->setMetadata(LLVMContext::MD_prof, NewWeights); 2181 } 2182 2183 return NewCall; 2184 } 2185 2186 // changeToCall - Convert the specified invoke into a normal call. 2187 CallInst *llvm::changeToCall(InvokeInst *II, DomTreeUpdater *DTU) { 2188 CallInst *NewCall = createCallMatchingInvoke(II); 2189 NewCall->takeName(II); 2190 NewCall->insertBefore(II); 2191 II->replaceAllUsesWith(NewCall); 2192 2193 // Follow the call by a branch to the normal destination. 2194 BasicBlock *NormalDestBB = II->getNormalDest(); 2195 BranchInst::Create(NormalDestBB, II); 2196 2197 // Update PHI nodes in the unwind destination 2198 BasicBlock *BB = II->getParent(); 2199 BasicBlock *UnwindDestBB = II->getUnwindDest(); 2200 UnwindDestBB->removePredecessor(BB); 2201 II->eraseFromParent(); 2202 if (DTU) 2203 DTU->applyUpdates({{DominatorTree::Delete, BB, UnwindDestBB}}); 2204 return NewCall; 2205 } 2206 2207 BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI, 2208 BasicBlock *UnwindEdge, 2209 DomTreeUpdater *DTU) { 2210 BasicBlock *BB = CI->getParent(); 2211 2212 // Convert this function call into an invoke instruction. First, split the 2213 // basic block. 2214 BasicBlock *Split = SplitBlock(BB, CI, DTU, /*LI=*/nullptr, /*MSSAU*/ nullptr, 2215 CI->getName() + ".noexc"); 2216 2217 // Delete the unconditional branch inserted by SplitBlock 2218 BB->getInstList().pop_back(); 2219 2220 // Create the new invoke instruction. 2221 SmallVector<Value *, 8> InvokeArgs(CI->args()); 2222 SmallVector<OperandBundleDef, 1> OpBundles; 2223 2224 CI->getOperandBundlesAsDefs(OpBundles); 2225 2226 // Note: we're round tripping operand bundles through memory here, and that 2227 // can potentially be avoided with a cleverer API design that we do not have 2228 // as of this time. 2229 2230 InvokeInst *II = 2231 InvokeInst::Create(CI->getFunctionType(), CI->getCalledOperand(), Split, 2232 UnwindEdge, InvokeArgs, OpBundles, CI->getName(), BB); 2233 II->setDebugLoc(CI->getDebugLoc()); 2234 II->setCallingConv(CI->getCallingConv()); 2235 II->setAttributes(CI->getAttributes()); 2236 II->setMetadata(LLVMContext::MD_prof, CI->getMetadata(LLVMContext::MD_prof)); 2237 2238 if (DTU) 2239 DTU->applyUpdates({{DominatorTree::Insert, BB, UnwindEdge}}); 2240 2241 // Make sure that anything using the call now uses the invoke! This also 2242 // updates the CallGraph if present, because it uses a WeakTrackingVH. 2243 CI->replaceAllUsesWith(II); 2244 2245 // Delete the original call 2246 Split->getInstList().pop_front(); 2247 return Split; 2248 } 2249 2250 static bool markAliveBlocks(Function &F, 2251 SmallPtrSetImpl<BasicBlock *> &Reachable, 2252 DomTreeUpdater *DTU = nullptr) { 2253 SmallVector<BasicBlock*, 128> Worklist; 2254 BasicBlock *BB = &F.front(); 2255 Worklist.push_back(BB); 2256 Reachable.insert(BB); 2257 bool Changed = false; 2258 do { 2259 BB = Worklist.pop_back_val(); 2260 2261 // Do a quick scan of the basic block, turning any obviously unreachable 2262 // instructions into LLVM unreachable insts. The instruction combining pass 2263 // canonicalizes unreachable insts into stores to null or undef. 2264 for (Instruction &I : *BB) { 2265 if (auto *CI = dyn_cast<CallInst>(&I)) { 2266 Value *Callee = CI->getCalledOperand(); 2267 // Handle intrinsic calls. 2268 if (Function *F = dyn_cast<Function>(Callee)) { 2269 auto IntrinsicID = F->getIntrinsicID(); 2270 // Assumptions that are known to be false are equivalent to 2271 // unreachable. Also, if the condition is undefined, then we make the 2272 // choice most beneficial to the optimizer, and choose that to also be 2273 // unreachable. 2274 if (IntrinsicID == Intrinsic::assume) { 2275 if (match(CI->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) { 2276 // Don't insert a call to llvm.trap right before the unreachable. 2277 changeToUnreachable(CI, false, DTU); 2278 Changed = true; 2279 break; 2280 } 2281 } else if (IntrinsicID == Intrinsic::experimental_guard) { 2282 // A call to the guard intrinsic bails out of the current 2283 // compilation unit if the predicate passed to it is false. If the 2284 // predicate is a constant false, then we know the guard will bail 2285 // out of the current compile unconditionally, so all code following 2286 // it is dead. 2287 // 2288 // Note: unlike in llvm.assume, it is not "obviously profitable" for 2289 // guards to treat `undef` as `false` since a guard on `undef` can 2290 // still be useful for widening. 2291 if (match(CI->getArgOperand(0), m_Zero())) 2292 if (!isa<UnreachableInst>(CI->getNextNode())) { 2293 changeToUnreachable(CI->getNextNode(), false, DTU); 2294 Changed = true; 2295 break; 2296 } 2297 } 2298 } else if ((isa<ConstantPointerNull>(Callee) && 2299 !NullPointerIsDefined(CI->getFunction())) || 2300 isa<UndefValue>(Callee)) { 2301 changeToUnreachable(CI, false, DTU); 2302 Changed = true; 2303 break; 2304 } 2305 if (CI->doesNotReturn() && !CI->isMustTailCall()) { 2306 // If we found a call to a no-return function, insert an unreachable 2307 // instruction after it. Make sure there isn't *already* one there 2308 // though. 2309 if (!isa<UnreachableInst>(CI->getNextNode())) { 2310 // Don't insert a call to llvm.trap right before the unreachable. 2311 changeToUnreachable(CI->getNextNode(), false, DTU); 2312 Changed = true; 2313 } 2314 break; 2315 } 2316 } else if (auto *SI = dyn_cast<StoreInst>(&I)) { 2317 // Store to undef and store to null are undefined and used to signal 2318 // that they should be changed to unreachable by passes that can't 2319 // modify the CFG. 2320 2321 // Don't touch volatile stores. 2322 if (SI->isVolatile()) continue; 2323 2324 Value *Ptr = SI->getOperand(1); 2325 2326 if (isa<UndefValue>(Ptr) || 2327 (isa<ConstantPointerNull>(Ptr) && 2328 !NullPointerIsDefined(SI->getFunction(), 2329 SI->getPointerAddressSpace()))) { 2330 changeToUnreachable(SI, false, DTU); 2331 Changed = true; 2332 break; 2333 } 2334 } 2335 } 2336 2337 Instruction *Terminator = BB->getTerminator(); 2338 if (auto *II = dyn_cast<InvokeInst>(Terminator)) { 2339 // Turn invokes that call 'nounwind' functions into ordinary calls. 2340 Value *Callee = II->getCalledOperand(); 2341 if ((isa<ConstantPointerNull>(Callee) && 2342 !NullPointerIsDefined(BB->getParent())) || 2343 isa<UndefValue>(Callee)) { 2344 changeToUnreachable(II, false, DTU); 2345 Changed = true; 2346 } else { 2347 if (II->doesNotReturn() && 2348 !isa<UnreachableInst>(II->getNormalDest()->front())) { 2349 // If we found an invoke of a no-return function, 2350 // create a new empty basic block with an `unreachable` terminator, 2351 // and set it as the normal destination for the invoke, 2352 // unless that is already the case. 2353 // Note that the original normal destination could have other uses. 2354 BasicBlock *OrigNormalDest = II->getNormalDest(); 2355 OrigNormalDest->removePredecessor(II->getParent()); 2356 LLVMContext &Ctx = II->getContext(); 2357 BasicBlock *UnreachableNormalDest = BasicBlock::Create( 2358 Ctx, OrigNormalDest->getName() + ".unreachable", 2359 II->getFunction(), OrigNormalDest); 2360 new UnreachableInst(Ctx, UnreachableNormalDest); 2361 II->setNormalDest(UnreachableNormalDest); 2362 if (DTU) 2363 DTU->applyUpdates( 2364 {{DominatorTree::Delete, BB, OrigNormalDest}, 2365 {DominatorTree::Insert, BB, UnreachableNormalDest}}); 2366 Changed = true; 2367 } 2368 if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) { 2369 if (II->use_empty() && !II->mayHaveSideEffects()) { 2370 // jump to the normal destination branch. 2371 BasicBlock *NormalDestBB = II->getNormalDest(); 2372 BasicBlock *UnwindDestBB = II->getUnwindDest(); 2373 BranchInst::Create(NormalDestBB, II); 2374 UnwindDestBB->removePredecessor(II->getParent()); 2375 II->eraseFromParent(); 2376 if (DTU) 2377 DTU->applyUpdates({{DominatorTree::Delete, BB, UnwindDestBB}}); 2378 } else 2379 changeToCall(II, DTU); 2380 Changed = true; 2381 } 2382 } 2383 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) { 2384 // Remove catchpads which cannot be reached. 2385 struct CatchPadDenseMapInfo { 2386 static CatchPadInst *getEmptyKey() { 2387 return DenseMapInfo<CatchPadInst *>::getEmptyKey(); 2388 } 2389 2390 static CatchPadInst *getTombstoneKey() { 2391 return DenseMapInfo<CatchPadInst *>::getTombstoneKey(); 2392 } 2393 2394 static unsigned getHashValue(CatchPadInst *CatchPad) { 2395 return static_cast<unsigned>(hash_combine_range( 2396 CatchPad->value_op_begin(), CatchPad->value_op_end())); 2397 } 2398 2399 static bool isEqual(CatchPadInst *LHS, CatchPadInst *RHS) { 2400 if (LHS == getEmptyKey() || LHS == getTombstoneKey() || 2401 RHS == getEmptyKey() || RHS == getTombstoneKey()) 2402 return LHS == RHS; 2403 return LHS->isIdenticalTo(RHS); 2404 } 2405 }; 2406 2407 SmallDenseMap<BasicBlock *, int, 8> NumPerSuccessorCases; 2408 // Set of unique CatchPads. 2409 SmallDenseMap<CatchPadInst *, detail::DenseSetEmpty, 4, 2410 CatchPadDenseMapInfo, detail::DenseSetPair<CatchPadInst *>> 2411 HandlerSet; 2412 detail::DenseSetEmpty Empty; 2413 for (CatchSwitchInst::handler_iterator I = CatchSwitch->handler_begin(), 2414 E = CatchSwitch->handler_end(); 2415 I != E; ++I) { 2416 BasicBlock *HandlerBB = *I; 2417 if (DTU) 2418 ++NumPerSuccessorCases[HandlerBB]; 2419 auto *CatchPad = cast<CatchPadInst>(HandlerBB->getFirstNonPHI()); 2420 if (!HandlerSet.insert({CatchPad, Empty}).second) { 2421 if (DTU) 2422 --NumPerSuccessorCases[HandlerBB]; 2423 CatchSwitch->removeHandler(I); 2424 --I; 2425 --E; 2426 Changed = true; 2427 } 2428 } 2429 if (DTU) { 2430 std::vector<DominatorTree::UpdateType> Updates; 2431 for (const std::pair<BasicBlock *, int> &I : NumPerSuccessorCases) 2432 if (I.second == 0) 2433 Updates.push_back({DominatorTree::Delete, BB, I.first}); 2434 DTU->applyUpdates(Updates); 2435 } 2436 } 2437 2438 Changed |= ConstantFoldTerminator(BB, true, nullptr, DTU); 2439 for (BasicBlock *Successor : successors(BB)) 2440 if (Reachable.insert(Successor).second) 2441 Worklist.push_back(Successor); 2442 } while (!Worklist.empty()); 2443 return Changed; 2444 } 2445 2446 void llvm::removeUnwindEdge(BasicBlock *BB, DomTreeUpdater *DTU) { 2447 Instruction *TI = BB->getTerminator(); 2448 2449 if (auto *II = dyn_cast<InvokeInst>(TI)) { 2450 changeToCall(II, DTU); 2451 return; 2452 } 2453 2454 Instruction *NewTI; 2455 BasicBlock *UnwindDest; 2456 2457 if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) { 2458 NewTI = CleanupReturnInst::Create(CRI->getCleanupPad(), nullptr, CRI); 2459 UnwindDest = CRI->getUnwindDest(); 2460 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(TI)) { 2461 auto *NewCatchSwitch = CatchSwitchInst::Create( 2462 CatchSwitch->getParentPad(), nullptr, CatchSwitch->getNumHandlers(), 2463 CatchSwitch->getName(), CatchSwitch); 2464 for (BasicBlock *PadBB : CatchSwitch->handlers()) 2465 NewCatchSwitch->addHandler(PadBB); 2466 2467 NewTI = NewCatchSwitch; 2468 UnwindDest = CatchSwitch->getUnwindDest(); 2469 } else { 2470 llvm_unreachable("Could not find unwind successor"); 2471 } 2472 2473 NewTI->takeName(TI); 2474 NewTI->setDebugLoc(TI->getDebugLoc()); 2475 UnwindDest->removePredecessor(BB); 2476 TI->replaceAllUsesWith(NewTI); 2477 TI->eraseFromParent(); 2478 if (DTU) 2479 DTU->applyUpdates({{DominatorTree::Delete, BB, UnwindDest}}); 2480 } 2481 2482 /// removeUnreachableBlocks - Remove blocks that are not reachable, even 2483 /// if they are in a dead cycle. Return true if a change was made, false 2484 /// otherwise. 2485 bool llvm::removeUnreachableBlocks(Function &F, DomTreeUpdater *DTU, 2486 MemorySSAUpdater *MSSAU) { 2487 SmallPtrSet<BasicBlock *, 16> Reachable; 2488 bool Changed = markAliveBlocks(F, Reachable, DTU); 2489 2490 // If there are unreachable blocks in the CFG... 2491 if (Reachable.size() == F.size()) 2492 return Changed; 2493 2494 assert(Reachable.size() < F.size()); 2495 2496 // Are there any blocks left to actually delete? 2497 SmallSetVector<BasicBlock *, 8> BlocksToRemove; 2498 for (BasicBlock &BB : F) { 2499 // Skip reachable basic blocks 2500 if (Reachable.count(&BB)) 2501 continue; 2502 // Skip already-deleted blocks 2503 if (DTU && DTU->isBBPendingDeletion(&BB)) 2504 continue; 2505 BlocksToRemove.insert(&BB); 2506 } 2507 2508 if (BlocksToRemove.empty()) 2509 return Changed; 2510 2511 Changed = true; 2512 NumRemoved += BlocksToRemove.size(); 2513 2514 if (MSSAU) 2515 MSSAU->removeBlocks(BlocksToRemove); 2516 2517 DeleteDeadBlocks(BlocksToRemove.takeVector(), DTU); 2518 2519 return Changed; 2520 } 2521 2522 void llvm::combineMetadata(Instruction *K, const Instruction *J, 2523 ArrayRef<unsigned> KnownIDs, bool DoesKMove) { 2524 SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata; 2525 K->dropUnknownNonDebugMetadata(KnownIDs); 2526 K->getAllMetadataOtherThanDebugLoc(Metadata); 2527 for (const auto &MD : Metadata) { 2528 unsigned Kind = MD.first; 2529 MDNode *JMD = J->getMetadata(Kind); 2530 MDNode *KMD = MD.second; 2531 2532 switch (Kind) { 2533 default: 2534 K->setMetadata(Kind, nullptr); // Remove unknown metadata 2535 break; 2536 case LLVMContext::MD_dbg: 2537 llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg"); 2538 case LLVMContext::MD_tbaa: 2539 K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD)); 2540 break; 2541 case LLVMContext::MD_alias_scope: 2542 K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD)); 2543 break; 2544 case LLVMContext::MD_noalias: 2545 case LLVMContext::MD_mem_parallel_loop_access: 2546 K->setMetadata(Kind, MDNode::intersect(JMD, KMD)); 2547 break; 2548 case LLVMContext::MD_access_group: 2549 K->setMetadata(LLVMContext::MD_access_group, 2550 intersectAccessGroups(K, J)); 2551 break; 2552 case LLVMContext::MD_range: 2553 2554 // If K does move, use most generic range. Otherwise keep the range of 2555 // K. 2556 if (DoesKMove) 2557 // FIXME: If K does move, we should drop the range info and nonnull. 2558 // Currently this function is used with DoesKMove in passes 2559 // doing hoisting/sinking and the current behavior of using the 2560 // most generic range is correct in those cases. 2561 K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD)); 2562 break; 2563 case LLVMContext::MD_fpmath: 2564 K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD)); 2565 break; 2566 case LLVMContext::MD_invariant_load: 2567 // Only set the !invariant.load if it is present in both instructions. 2568 K->setMetadata(Kind, JMD); 2569 break; 2570 case LLVMContext::MD_nonnull: 2571 // If K does move, keep nonull if it is present in both instructions. 2572 if (DoesKMove) 2573 K->setMetadata(Kind, JMD); 2574 break; 2575 case LLVMContext::MD_invariant_group: 2576 // Preserve !invariant.group in K. 2577 break; 2578 case LLVMContext::MD_align: 2579 K->setMetadata(Kind, 2580 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD)); 2581 break; 2582 case LLVMContext::MD_dereferenceable: 2583 case LLVMContext::MD_dereferenceable_or_null: 2584 K->setMetadata(Kind, 2585 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD)); 2586 break; 2587 case LLVMContext::MD_preserve_access_index: 2588 // Preserve !preserve.access.index in K. 2589 break; 2590 } 2591 } 2592 // Set !invariant.group from J if J has it. If both instructions have it 2593 // then we will just pick it from J - even when they are different. 2594 // Also make sure that K is load or store - f.e. combining bitcast with load 2595 // could produce bitcast with invariant.group metadata, which is invalid. 2596 // FIXME: we should try to preserve both invariant.group md if they are 2597 // different, but right now instruction can only have one invariant.group. 2598 if (auto *JMD = J->getMetadata(LLVMContext::MD_invariant_group)) 2599 if (isa<LoadInst>(K) || isa<StoreInst>(K)) 2600 K->setMetadata(LLVMContext::MD_invariant_group, JMD); 2601 } 2602 2603 void llvm::combineMetadataForCSE(Instruction *K, const Instruction *J, 2604 bool KDominatesJ) { 2605 unsigned KnownIDs[] = { 2606 LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope, 2607 LLVMContext::MD_noalias, LLVMContext::MD_range, 2608 LLVMContext::MD_invariant_load, LLVMContext::MD_nonnull, 2609 LLVMContext::MD_invariant_group, LLVMContext::MD_align, 2610 LLVMContext::MD_dereferenceable, 2611 LLVMContext::MD_dereferenceable_or_null, 2612 LLVMContext::MD_access_group, LLVMContext::MD_preserve_access_index}; 2613 combineMetadata(K, J, KnownIDs, KDominatesJ); 2614 } 2615 2616 void llvm::copyMetadataForLoad(LoadInst &Dest, const LoadInst &Source) { 2617 SmallVector<std::pair<unsigned, MDNode *>, 8> MD; 2618 Source.getAllMetadata(MD); 2619 MDBuilder MDB(Dest.getContext()); 2620 Type *NewType = Dest.getType(); 2621 const DataLayout &DL = Source.getModule()->getDataLayout(); 2622 for (const auto &MDPair : MD) { 2623 unsigned ID = MDPair.first; 2624 MDNode *N = MDPair.second; 2625 // Note, essentially every kind of metadata should be preserved here! This 2626 // routine is supposed to clone a load instruction changing *only its type*. 2627 // The only metadata it makes sense to drop is metadata which is invalidated 2628 // when the pointer type changes. This should essentially never be the case 2629 // in LLVM, but we explicitly switch over only known metadata to be 2630 // conservatively correct. If you are adding metadata to LLVM which pertains 2631 // to loads, you almost certainly want to add it here. 2632 switch (ID) { 2633 case LLVMContext::MD_dbg: 2634 case LLVMContext::MD_tbaa: 2635 case LLVMContext::MD_prof: 2636 case LLVMContext::MD_fpmath: 2637 case LLVMContext::MD_tbaa_struct: 2638 case LLVMContext::MD_invariant_load: 2639 case LLVMContext::MD_alias_scope: 2640 case LLVMContext::MD_noalias: 2641 case LLVMContext::MD_nontemporal: 2642 case LLVMContext::MD_mem_parallel_loop_access: 2643 case LLVMContext::MD_access_group: 2644 // All of these directly apply. 2645 Dest.setMetadata(ID, N); 2646 break; 2647 2648 case LLVMContext::MD_nonnull: 2649 copyNonnullMetadata(Source, N, Dest); 2650 break; 2651 2652 case LLVMContext::MD_align: 2653 case LLVMContext::MD_dereferenceable: 2654 case LLVMContext::MD_dereferenceable_or_null: 2655 // These only directly apply if the new type is also a pointer. 2656 if (NewType->isPointerTy()) 2657 Dest.setMetadata(ID, N); 2658 break; 2659 2660 case LLVMContext::MD_range: 2661 copyRangeMetadata(DL, Source, N, Dest); 2662 break; 2663 } 2664 } 2665 } 2666 2667 void llvm::patchReplacementInstruction(Instruction *I, Value *Repl) { 2668 auto *ReplInst = dyn_cast<Instruction>(Repl); 2669 if (!ReplInst) 2670 return; 2671 2672 // Patch the replacement so that it is not more restrictive than the value 2673 // being replaced. 2674 // Note that if 'I' is a load being replaced by some operation, 2675 // for example, by an arithmetic operation, then andIRFlags() 2676 // would just erase all math flags from the original arithmetic 2677 // operation, which is clearly not wanted and not needed. 2678 if (!isa<LoadInst>(I)) 2679 ReplInst->andIRFlags(I); 2680 2681 // FIXME: If both the original and replacement value are part of the 2682 // same control-flow region (meaning that the execution of one 2683 // guarantees the execution of the other), then we can combine the 2684 // noalias scopes here and do better than the general conservative 2685 // answer used in combineMetadata(). 2686 2687 // In general, GVN unifies expressions over different control-flow 2688 // regions, and so we need a conservative combination of the noalias 2689 // scopes. 2690 static const unsigned KnownIDs[] = { 2691 LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope, 2692 LLVMContext::MD_noalias, LLVMContext::MD_range, 2693 LLVMContext::MD_fpmath, LLVMContext::MD_invariant_load, 2694 LLVMContext::MD_invariant_group, LLVMContext::MD_nonnull, 2695 LLVMContext::MD_access_group, LLVMContext::MD_preserve_access_index}; 2696 combineMetadata(ReplInst, I, KnownIDs, false); 2697 } 2698 2699 template <typename RootType, typename DominatesFn> 2700 static unsigned replaceDominatedUsesWith(Value *From, Value *To, 2701 const RootType &Root, 2702 const DominatesFn &Dominates) { 2703 assert(From->getType() == To->getType()); 2704 2705 unsigned Count = 0; 2706 for (Use &U : llvm::make_early_inc_range(From->uses())) { 2707 if (!Dominates(Root, U)) 2708 continue; 2709 U.set(To); 2710 LLVM_DEBUG(dbgs() << "Replace dominated use of '" << From->getName() 2711 << "' as " << *To << " in " << *U << "\n"); 2712 ++Count; 2713 } 2714 return Count; 2715 } 2716 2717 unsigned llvm::replaceNonLocalUsesWith(Instruction *From, Value *To) { 2718 assert(From->getType() == To->getType()); 2719 auto *BB = From->getParent(); 2720 unsigned Count = 0; 2721 2722 for (Use &U : llvm::make_early_inc_range(From->uses())) { 2723 auto *I = cast<Instruction>(U.getUser()); 2724 if (I->getParent() == BB) 2725 continue; 2726 U.set(To); 2727 ++Count; 2728 } 2729 return Count; 2730 } 2731 2732 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To, 2733 DominatorTree &DT, 2734 const BasicBlockEdge &Root) { 2735 auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) { 2736 return DT.dominates(Root, U); 2737 }; 2738 return ::replaceDominatedUsesWith(From, To, Root, Dominates); 2739 } 2740 2741 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To, 2742 DominatorTree &DT, 2743 const BasicBlock *BB) { 2744 auto Dominates = [&DT](const BasicBlock *BB, const Use &U) { 2745 return DT.dominates(BB, U); 2746 }; 2747 return ::replaceDominatedUsesWith(From, To, BB, Dominates); 2748 } 2749 2750 bool llvm::callsGCLeafFunction(const CallBase *Call, 2751 const TargetLibraryInfo &TLI) { 2752 // Check if the function is specifically marked as a gc leaf function. 2753 if (Call->hasFnAttr("gc-leaf-function")) 2754 return true; 2755 if (const Function *F = Call->getCalledFunction()) { 2756 if (F->hasFnAttribute("gc-leaf-function")) 2757 return true; 2758 2759 if (auto IID = F->getIntrinsicID()) { 2760 // Most LLVM intrinsics do not take safepoints. 2761 return IID != Intrinsic::experimental_gc_statepoint && 2762 IID != Intrinsic::experimental_deoptimize && 2763 IID != Intrinsic::memcpy_element_unordered_atomic && 2764 IID != Intrinsic::memmove_element_unordered_atomic; 2765 } 2766 } 2767 2768 // Lib calls can be materialized by some passes, and won't be 2769 // marked as 'gc-leaf-function.' All available Libcalls are 2770 // GC-leaf. 2771 LibFunc LF; 2772 if (TLI.getLibFunc(*Call, LF)) { 2773 return TLI.has(LF); 2774 } 2775 2776 return false; 2777 } 2778 2779 void llvm::copyNonnullMetadata(const LoadInst &OldLI, MDNode *N, 2780 LoadInst &NewLI) { 2781 auto *NewTy = NewLI.getType(); 2782 2783 // This only directly applies if the new type is also a pointer. 2784 if (NewTy->isPointerTy()) { 2785 NewLI.setMetadata(LLVMContext::MD_nonnull, N); 2786 return; 2787 } 2788 2789 // The only other translation we can do is to integral loads with !range 2790 // metadata. 2791 if (!NewTy->isIntegerTy()) 2792 return; 2793 2794 MDBuilder MDB(NewLI.getContext()); 2795 const Value *Ptr = OldLI.getPointerOperand(); 2796 auto *ITy = cast<IntegerType>(NewTy); 2797 auto *NullInt = ConstantExpr::getPtrToInt( 2798 ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy); 2799 auto *NonNullInt = ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1)); 2800 NewLI.setMetadata(LLVMContext::MD_range, 2801 MDB.createRange(NonNullInt, NullInt)); 2802 } 2803 2804 void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI, 2805 MDNode *N, LoadInst &NewLI) { 2806 auto *NewTy = NewLI.getType(); 2807 2808 // Give up unless it is converted to a pointer where there is a single very 2809 // valuable mapping we can do reliably. 2810 // FIXME: It would be nice to propagate this in more ways, but the type 2811 // conversions make it hard. 2812 if (!NewTy->isPointerTy()) 2813 return; 2814 2815 unsigned BitWidth = DL.getPointerTypeSizeInBits(NewTy); 2816 if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) { 2817 MDNode *NN = MDNode::get(OldLI.getContext(), None); 2818 NewLI.setMetadata(LLVMContext::MD_nonnull, NN); 2819 } 2820 } 2821 2822 void llvm::dropDebugUsers(Instruction &I) { 2823 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; 2824 findDbgUsers(DbgUsers, &I); 2825 for (auto *DII : DbgUsers) 2826 DII->eraseFromParent(); 2827 } 2828 2829 void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt, 2830 BasicBlock *BB) { 2831 // Since we are moving the instructions out of its basic block, we do not 2832 // retain their original debug locations (DILocations) and debug intrinsic 2833 // instructions. 2834 // 2835 // Doing so would degrade the debugging experience and adversely affect the 2836 // accuracy of profiling information. 2837 // 2838 // Currently, when hoisting the instructions, we take the following actions: 2839 // - Remove their debug intrinsic instructions. 2840 // - Set their debug locations to the values from the insertion point. 2841 // 2842 // As per PR39141 (comment #8), the more fundamental reason why the dbg.values 2843 // need to be deleted, is because there will not be any instructions with a 2844 // DILocation in either branch left after performing the transformation. We 2845 // can only insert a dbg.value after the two branches are joined again. 2846 // 2847 // See PR38762, PR39243 for more details. 2848 // 2849 // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to 2850 // encode predicated DIExpressions that yield different results on different 2851 // code paths. 2852 2853 for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) { 2854 Instruction *I = &*II; 2855 I->dropUndefImplyingAttrsAndUnknownMetadata(); 2856 if (I->isUsedByMetadata()) 2857 dropDebugUsers(*I); 2858 if (I->isDebugOrPseudoInst()) { 2859 // Remove DbgInfo and pseudo probe Intrinsics. 2860 II = I->eraseFromParent(); 2861 continue; 2862 } 2863 I->setDebugLoc(InsertPt->getDebugLoc()); 2864 ++II; 2865 } 2866 DomBlock->getInstList().splice(InsertPt->getIterator(), BB->getInstList(), 2867 BB->begin(), 2868 BB->getTerminator()->getIterator()); 2869 } 2870 2871 namespace { 2872 2873 /// A potential constituent of a bitreverse or bswap expression. See 2874 /// collectBitParts for a fuller explanation. 2875 struct BitPart { 2876 BitPart(Value *P, unsigned BW) : Provider(P) { 2877 Provenance.resize(BW); 2878 } 2879 2880 /// The Value that this is a bitreverse/bswap of. 2881 Value *Provider; 2882 2883 /// The "provenance" of each bit. Provenance[A] = B means that bit A 2884 /// in Provider becomes bit B in the result of this expression. 2885 SmallVector<int8_t, 32> Provenance; // int8_t means max size is i128. 2886 2887 enum { Unset = -1 }; 2888 }; 2889 2890 } // end anonymous namespace 2891 2892 /// Analyze the specified subexpression and see if it is capable of providing 2893 /// pieces of a bswap or bitreverse. The subexpression provides a potential 2894 /// piece of a bswap or bitreverse if it can be proved that each non-zero bit in 2895 /// the output of the expression came from a corresponding bit in some other 2896 /// value. This function is recursive, and the end result is a mapping of 2897 /// bitnumber to bitnumber. It is the caller's responsibility to validate that 2898 /// the bitnumber to bitnumber mapping is correct for a bswap or bitreverse. 2899 /// 2900 /// For example, if the current subexpression if "(shl i32 %X, 24)" then we know 2901 /// that the expression deposits the low byte of %X into the high byte of the 2902 /// result and that all other bits are zero. This expression is accepted and a 2903 /// BitPart is returned with Provider set to %X and Provenance[24-31] set to 2904 /// [0-7]. 2905 /// 2906 /// For vector types, all analysis is performed at the per-element level. No 2907 /// cross-element analysis is supported (shuffle/insertion/reduction), and all 2908 /// constant masks must be splatted across all elements. 2909 /// 2910 /// To avoid revisiting values, the BitPart results are memoized into the 2911 /// provided map. To avoid unnecessary copying of BitParts, BitParts are 2912 /// constructed in-place in the \c BPS map. Because of this \c BPS needs to 2913 /// store BitParts objects, not pointers. As we need the concept of a nullptr 2914 /// BitParts (Value has been analyzed and the analysis failed), we an Optional 2915 /// type instead to provide the same functionality. 2916 /// 2917 /// Because we pass around references into \c BPS, we must use a container that 2918 /// does not invalidate internal references (std::map instead of DenseMap). 2919 static const Optional<BitPart> & 2920 collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals, 2921 std::map<Value *, Optional<BitPart>> &BPS, int Depth, 2922 bool &FoundRoot) { 2923 auto I = BPS.find(V); 2924 if (I != BPS.end()) 2925 return I->second; 2926 2927 auto &Result = BPS[V] = None; 2928 auto BitWidth = V->getType()->getScalarSizeInBits(); 2929 2930 // Can't do integer/elements > 128 bits. 2931 if (BitWidth > 128) 2932 return Result; 2933 2934 // Prevent stack overflow by limiting the recursion depth 2935 if (Depth == BitPartRecursionMaxDepth) { 2936 LLVM_DEBUG(dbgs() << "collectBitParts max recursion depth reached.\n"); 2937 return Result; 2938 } 2939 2940 if (auto *I = dyn_cast<Instruction>(V)) { 2941 Value *X, *Y; 2942 const APInt *C; 2943 2944 // If this is an or instruction, it may be an inner node of the bswap. 2945 if (match(V, m_Or(m_Value(X), m_Value(Y)))) { 2946 // Check we have both sources and they are from the same provider. 2947 const auto &A = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 2948 Depth + 1, FoundRoot); 2949 if (!A || !A->Provider) 2950 return Result; 2951 2952 const auto &B = collectBitParts(Y, MatchBSwaps, MatchBitReversals, BPS, 2953 Depth + 1, FoundRoot); 2954 if (!B || A->Provider != B->Provider) 2955 return Result; 2956 2957 // Try and merge the two together. 2958 Result = BitPart(A->Provider, BitWidth); 2959 for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx) { 2960 if (A->Provenance[BitIdx] != BitPart::Unset && 2961 B->Provenance[BitIdx] != BitPart::Unset && 2962 A->Provenance[BitIdx] != B->Provenance[BitIdx]) 2963 return Result = None; 2964 2965 if (A->Provenance[BitIdx] == BitPart::Unset) 2966 Result->Provenance[BitIdx] = B->Provenance[BitIdx]; 2967 else 2968 Result->Provenance[BitIdx] = A->Provenance[BitIdx]; 2969 } 2970 2971 return Result; 2972 } 2973 2974 // If this is a logical shift by a constant, recurse then shift the result. 2975 if (match(V, m_LogicalShift(m_Value(X), m_APInt(C)))) { 2976 const APInt &BitShift = *C; 2977 2978 // Ensure the shift amount is defined. 2979 if (BitShift.uge(BitWidth)) 2980 return Result; 2981 2982 // For bswap-only, limit shift amounts to whole bytes, for an early exit. 2983 if (!MatchBitReversals && (BitShift.getZExtValue() % 8) != 0) 2984 return Result; 2985 2986 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 2987 Depth + 1, FoundRoot); 2988 if (!Res) 2989 return Result; 2990 Result = Res; 2991 2992 // Perform the "shift" on BitProvenance. 2993 auto &P = Result->Provenance; 2994 if (I->getOpcode() == Instruction::Shl) { 2995 P.erase(std::prev(P.end(), BitShift.getZExtValue()), P.end()); 2996 P.insert(P.begin(), BitShift.getZExtValue(), BitPart::Unset); 2997 } else { 2998 P.erase(P.begin(), std::next(P.begin(), BitShift.getZExtValue())); 2999 P.insert(P.end(), BitShift.getZExtValue(), BitPart::Unset); 3000 } 3001 3002 return Result; 3003 } 3004 3005 // If this is a logical 'and' with a mask that clears bits, recurse then 3006 // unset the appropriate bits. 3007 if (match(V, m_And(m_Value(X), m_APInt(C)))) { 3008 const APInt &AndMask = *C; 3009 3010 // Check that the mask allows a multiple of 8 bits for a bswap, for an 3011 // early exit. 3012 unsigned NumMaskedBits = AndMask.countPopulation(); 3013 if (!MatchBitReversals && (NumMaskedBits % 8) != 0) 3014 return Result; 3015 3016 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3017 Depth + 1, FoundRoot); 3018 if (!Res) 3019 return Result; 3020 Result = Res; 3021 3022 for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx) 3023 // If the AndMask is zero for this bit, clear the bit. 3024 if (AndMask[BitIdx] == 0) 3025 Result->Provenance[BitIdx] = BitPart::Unset; 3026 return Result; 3027 } 3028 3029 // If this is a zext instruction zero extend the result. 3030 if (match(V, m_ZExt(m_Value(X)))) { 3031 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3032 Depth + 1, FoundRoot); 3033 if (!Res) 3034 return Result; 3035 3036 Result = BitPart(Res->Provider, BitWidth); 3037 auto NarrowBitWidth = X->getType()->getScalarSizeInBits(); 3038 for (unsigned BitIdx = 0; BitIdx < NarrowBitWidth; ++BitIdx) 3039 Result->Provenance[BitIdx] = Res->Provenance[BitIdx]; 3040 for (unsigned BitIdx = NarrowBitWidth; BitIdx < BitWidth; ++BitIdx) 3041 Result->Provenance[BitIdx] = BitPart::Unset; 3042 return Result; 3043 } 3044 3045 // If this is a truncate instruction, extract the lower bits. 3046 if (match(V, m_Trunc(m_Value(X)))) { 3047 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3048 Depth + 1, FoundRoot); 3049 if (!Res) 3050 return Result; 3051 3052 Result = BitPart(Res->Provider, BitWidth); 3053 for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx) 3054 Result->Provenance[BitIdx] = Res->Provenance[BitIdx]; 3055 return Result; 3056 } 3057 3058 // BITREVERSE - most likely due to us previous matching a partial 3059 // bitreverse. 3060 if (match(V, m_BitReverse(m_Value(X)))) { 3061 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3062 Depth + 1, FoundRoot); 3063 if (!Res) 3064 return Result; 3065 3066 Result = BitPart(Res->Provider, BitWidth); 3067 for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx) 3068 Result->Provenance[(BitWidth - 1) - BitIdx] = Res->Provenance[BitIdx]; 3069 return Result; 3070 } 3071 3072 // BSWAP - most likely due to us previous matching a partial bswap. 3073 if (match(V, m_BSwap(m_Value(X)))) { 3074 const auto &Res = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3075 Depth + 1, FoundRoot); 3076 if (!Res) 3077 return Result; 3078 3079 unsigned ByteWidth = BitWidth / 8; 3080 Result = BitPart(Res->Provider, BitWidth); 3081 for (unsigned ByteIdx = 0; ByteIdx < ByteWidth; ++ByteIdx) { 3082 unsigned ByteBitOfs = ByteIdx * 8; 3083 for (unsigned BitIdx = 0; BitIdx < 8; ++BitIdx) 3084 Result->Provenance[(BitWidth - 8 - ByteBitOfs) + BitIdx] = 3085 Res->Provenance[ByteBitOfs + BitIdx]; 3086 } 3087 return Result; 3088 } 3089 3090 // Funnel 'double' shifts take 3 operands, 2 inputs and the shift 3091 // amount (modulo). 3092 // fshl(X,Y,Z): (X << (Z % BW)) | (Y >> (BW - (Z % BW))) 3093 // fshr(X,Y,Z): (X << (BW - (Z % BW))) | (Y >> (Z % BW)) 3094 if (match(V, m_FShl(m_Value(X), m_Value(Y), m_APInt(C))) || 3095 match(V, m_FShr(m_Value(X), m_Value(Y), m_APInt(C)))) { 3096 // We can treat fshr as a fshl by flipping the modulo amount. 3097 unsigned ModAmt = C->urem(BitWidth); 3098 if (cast<IntrinsicInst>(I)->getIntrinsicID() == Intrinsic::fshr) 3099 ModAmt = BitWidth - ModAmt; 3100 3101 // For bswap-only, limit shift amounts to whole bytes, for an early exit. 3102 if (!MatchBitReversals && (ModAmt % 8) != 0) 3103 return Result; 3104 3105 // Check we have both sources and they are from the same provider. 3106 const auto &LHS = collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, 3107 Depth + 1, FoundRoot); 3108 if (!LHS || !LHS->Provider) 3109 return Result; 3110 3111 const auto &RHS = collectBitParts(Y, MatchBSwaps, MatchBitReversals, BPS, 3112 Depth + 1, FoundRoot); 3113 if (!RHS || LHS->Provider != RHS->Provider) 3114 return Result; 3115 3116 unsigned StartBitRHS = BitWidth - ModAmt; 3117 Result = BitPart(LHS->Provider, BitWidth); 3118 for (unsigned BitIdx = 0; BitIdx < StartBitRHS; ++BitIdx) 3119 Result->Provenance[BitIdx + ModAmt] = LHS->Provenance[BitIdx]; 3120 for (unsigned BitIdx = 0; BitIdx < ModAmt; ++BitIdx) 3121 Result->Provenance[BitIdx] = RHS->Provenance[BitIdx + StartBitRHS]; 3122 return Result; 3123 } 3124 } 3125 3126 // If we've already found a root input value then we're never going to merge 3127 // these back together. 3128 if (FoundRoot) 3129 return Result; 3130 3131 // Okay, we got to something that isn't a shift, 'or', 'and', etc. This must 3132 // be the root input value to the bswap/bitreverse. 3133 FoundRoot = true; 3134 Result = BitPart(V, BitWidth); 3135 for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx) 3136 Result->Provenance[BitIdx] = BitIdx; 3137 return Result; 3138 } 3139 3140 static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To, 3141 unsigned BitWidth) { 3142 if (From % 8 != To % 8) 3143 return false; 3144 // Convert from bit indices to byte indices and check for a byte reversal. 3145 From >>= 3; 3146 To >>= 3; 3147 BitWidth >>= 3; 3148 return From == BitWidth - To - 1; 3149 } 3150 3151 static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To, 3152 unsigned BitWidth) { 3153 return From == BitWidth - To - 1; 3154 } 3155 3156 bool llvm::recognizeBSwapOrBitReverseIdiom( 3157 Instruction *I, bool MatchBSwaps, bool MatchBitReversals, 3158 SmallVectorImpl<Instruction *> &InsertedInsts) { 3159 if (!match(I, m_Or(m_Value(), m_Value())) && 3160 !match(I, m_FShl(m_Value(), m_Value(), m_Value())) && 3161 !match(I, m_FShr(m_Value(), m_Value(), m_Value()))) 3162 return false; 3163 if (!MatchBSwaps && !MatchBitReversals) 3164 return false; 3165 Type *ITy = I->getType(); 3166 if (!ITy->isIntOrIntVectorTy() || ITy->getScalarSizeInBits() > 128) 3167 return false; // Can't do integer/elements > 128 bits. 3168 3169 // Try to find all the pieces corresponding to the bswap. 3170 bool FoundRoot = false; 3171 std::map<Value *, Optional<BitPart>> BPS; 3172 const auto &Res = 3173 collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS, 0, FoundRoot); 3174 if (!Res) 3175 return false; 3176 ArrayRef<int8_t> BitProvenance = Res->Provenance; 3177 assert(all_of(BitProvenance, 3178 [](int8_t I) { return I == BitPart::Unset || 0 <= I; }) && 3179 "Illegal bit provenance index"); 3180 3181 // If the upper bits are zero, then attempt to perform as a truncated op. 3182 Type *DemandedTy = ITy; 3183 if (BitProvenance.back() == BitPart::Unset) { 3184 while (!BitProvenance.empty() && BitProvenance.back() == BitPart::Unset) 3185 BitProvenance = BitProvenance.drop_back(); 3186 if (BitProvenance.empty()) 3187 return false; // TODO - handle null value? 3188 DemandedTy = Type::getIntNTy(I->getContext(), BitProvenance.size()); 3189 if (auto *IVecTy = dyn_cast<VectorType>(ITy)) 3190 DemandedTy = VectorType::get(DemandedTy, IVecTy); 3191 } 3192 3193 // Check BitProvenance hasn't found a source larger than the result type. 3194 unsigned DemandedBW = DemandedTy->getScalarSizeInBits(); 3195 if (DemandedBW > ITy->getScalarSizeInBits()) 3196 return false; 3197 3198 // Now, is the bit permutation correct for a bswap or a bitreverse? We can 3199 // only byteswap values with an even number of bytes. 3200 APInt DemandedMask = APInt::getAllOnes(DemandedBW); 3201 bool OKForBSwap = MatchBSwaps && (DemandedBW % 16) == 0; 3202 bool OKForBitReverse = MatchBitReversals; 3203 for (unsigned BitIdx = 0; 3204 (BitIdx < DemandedBW) && (OKForBSwap || OKForBitReverse); ++BitIdx) { 3205 if (BitProvenance[BitIdx] == BitPart::Unset) { 3206 DemandedMask.clearBit(BitIdx); 3207 continue; 3208 } 3209 OKForBSwap &= bitTransformIsCorrectForBSwap(BitProvenance[BitIdx], BitIdx, 3210 DemandedBW); 3211 OKForBitReverse &= bitTransformIsCorrectForBitReverse(BitProvenance[BitIdx], 3212 BitIdx, DemandedBW); 3213 } 3214 3215 Intrinsic::ID Intrin; 3216 if (OKForBSwap) 3217 Intrin = Intrinsic::bswap; 3218 else if (OKForBitReverse) 3219 Intrin = Intrinsic::bitreverse; 3220 else 3221 return false; 3222 3223 Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, DemandedTy); 3224 Value *Provider = Res->Provider; 3225 3226 // We may need to truncate the provider. 3227 if (DemandedTy != Provider->getType()) { 3228 auto *Trunc = 3229 CastInst::CreateIntegerCast(Provider, DemandedTy, false, "trunc", I); 3230 InsertedInsts.push_back(Trunc); 3231 Provider = Trunc; 3232 } 3233 3234 Instruction *Result = CallInst::Create(F, Provider, "rev", I); 3235 InsertedInsts.push_back(Result); 3236 3237 if (!DemandedMask.isAllOnes()) { 3238 auto *Mask = ConstantInt::get(DemandedTy, DemandedMask); 3239 Result = BinaryOperator::Create(Instruction::And, Result, Mask, "mask", I); 3240 InsertedInsts.push_back(Result); 3241 } 3242 3243 // We may need to zeroextend back to the result type. 3244 if (ITy != Result->getType()) { 3245 auto *ExtInst = CastInst::CreateIntegerCast(Result, ITy, false, "zext", I); 3246 InsertedInsts.push_back(ExtInst); 3247 } 3248 3249 return true; 3250 } 3251 3252 // CodeGen has special handling for some string functions that may replace 3253 // them with target-specific intrinsics. Since that'd skip our interceptors 3254 // in ASan/MSan/TSan/DFSan, and thus make us miss some memory accesses, 3255 // we mark affected calls as NoBuiltin, which will disable optimization 3256 // in CodeGen. 3257 void llvm::maybeMarkSanitizerLibraryCallNoBuiltin( 3258 CallInst *CI, const TargetLibraryInfo *TLI) { 3259 Function *F = CI->getCalledFunction(); 3260 LibFunc Func; 3261 if (F && !F->hasLocalLinkage() && F->hasName() && 3262 TLI->getLibFunc(F->getName(), Func) && TLI->hasOptimizedCodeGen(Func) && 3263 !F->doesNotAccessMemory()) 3264 CI->addFnAttr(Attribute::NoBuiltin); 3265 } 3266 3267 bool llvm::canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx) { 3268 // We can't have a PHI with a metadata type. 3269 if (I->getOperand(OpIdx)->getType()->isMetadataTy()) 3270 return false; 3271 3272 // Early exit. 3273 if (!isa<Constant>(I->getOperand(OpIdx))) 3274 return true; 3275 3276 switch (I->getOpcode()) { 3277 default: 3278 return true; 3279 case Instruction::Call: 3280 case Instruction::Invoke: { 3281 const auto &CB = cast<CallBase>(*I); 3282 3283 // Can't handle inline asm. Skip it. 3284 if (CB.isInlineAsm()) 3285 return false; 3286 3287 // Constant bundle operands may need to retain their constant-ness for 3288 // correctness. 3289 if (CB.isBundleOperand(OpIdx)) 3290 return false; 3291 3292 if (OpIdx < CB.arg_size()) { 3293 // Some variadic intrinsics require constants in the variadic arguments, 3294 // which currently aren't markable as immarg. 3295 if (isa<IntrinsicInst>(CB) && 3296 OpIdx >= CB.getFunctionType()->getNumParams()) { 3297 // This is known to be OK for stackmap. 3298 return CB.getIntrinsicID() == Intrinsic::experimental_stackmap; 3299 } 3300 3301 // gcroot is a special case, since it requires a constant argument which 3302 // isn't also required to be a simple ConstantInt. 3303 if (CB.getIntrinsicID() == Intrinsic::gcroot) 3304 return false; 3305 3306 // Some intrinsic operands are required to be immediates. 3307 return !CB.paramHasAttr(OpIdx, Attribute::ImmArg); 3308 } 3309 3310 // It is never allowed to replace the call argument to an intrinsic, but it 3311 // may be possible for a call. 3312 return !isa<IntrinsicInst>(CB); 3313 } 3314 case Instruction::ShuffleVector: 3315 // Shufflevector masks are constant. 3316 return OpIdx != 2; 3317 case Instruction::Switch: 3318 case Instruction::ExtractValue: 3319 // All operands apart from the first are constant. 3320 return OpIdx == 0; 3321 case Instruction::InsertValue: 3322 // All operands apart from the first and the second are constant. 3323 return OpIdx < 2; 3324 case Instruction::Alloca: 3325 // Static allocas (constant size in the entry block) are handled by 3326 // prologue/epilogue insertion so they're free anyway. We definitely don't 3327 // want to make them non-constant. 3328 return !cast<AllocaInst>(I)->isStaticAlloca(); 3329 case Instruction::GetElementPtr: 3330 if (OpIdx == 0) 3331 return true; 3332 gep_type_iterator It = gep_type_begin(I); 3333 for (auto E = std::next(It, OpIdx); It != E; ++It) 3334 if (It.isStruct()) 3335 return false; 3336 return true; 3337 } 3338 } 3339 3340 Value *llvm::invertCondition(Value *Condition) { 3341 // First: Check if it's a constant 3342 if (Constant *C = dyn_cast<Constant>(Condition)) 3343 return ConstantExpr::getNot(C); 3344 3345 // Second: If the condition is already inverted, return the original value 3346 Value *NotCondition; 3347 if (match(Condition, m_Not(m_Value(NotCondition)))) 3348 return NotCondition; 3349 3350 BasicBlock *Parent = nullptr; 3351 Instruction *Inst = dyn_cast<Instruction>(Condition); 3352 if (Inst) 3353 Parent = Inst->getParent(); 3354 else if (Argument *Arg = dyn_cast<Argument>(Condition)) 3355 Parent = &Arg->getParent()->getEntryBlock(); 3356 assert(Parent && "Unsupported condition to invert"); 3357 3358 // Third: Check all the users for an invert 3359 for (User *U : Condition->users()) 3360 if (Instruction *I = dyn_cast<Instruction>(U)) 3361 if (I->getParent() == Parent && match(I, m_Not(m_Specific(Condition)))) 3362 return I; 3363 3364 // Last option: Create a new instruction 3365 auto *Inverted = 3366 BinaryOperator::CreateNot(Condition, Condition->getName() + ".inv"); 3367 if (Inst && !isa<PHINode>(Inst)) 3368 Inverted->insertAfter(Inst); 3369 else 3370 Inverted->insertBefore(&*Parent->getFirstInsertionPt()); 3371 return Inverted; 3372 } 3373 3374 bool llvm::inferAttributesFromOthers(Function &F) { 3375 // Note: We explicitly check for attributes rather than using cover functions 3376 // because some of the cover functions include the logic being implemented. 3377 3378 bool Changed = false; 3379 // readnone + not convergent implies nosync 3380 if (!F.hasFnAttribute(Attribute::NoSync) && 3381 F.doesNotAccessMemory() && !F.isConvergent()) { 3382 F.setNoSync(); 3383 Changed = true; 3384 } 3385 3386 // readonly implies nofree 3387 if (!F.hasFnAttribute(Attribute::NoFree) && F.onlyReadsMemory()) { 3388 F.setDoesNotFreeMemory(); 3389 Changed = true; 3390 } 3391 3392 // willreturn implies mustprogress 3393 if (!F.hasFnAttribute(Attribute::MustProgress) && F.willReturn()) { 3394 F.setMustProgress(); 3395 Changed = true; 3396 } 3397 3398 // TODO: There are a bunch of cases of restrictive memory effects we 3399 // can infer by inspecting arguments of argmemonly-ish functions. 3400 3401 return Changed; 3402 } 3403