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