DwarfEHPrepare.cpp revision efbf30610739d73d1f2dba9a8c29aa30c8c3daa4
1//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass mulches exception handling code into a form adapted to code 11// generation. Required if using dwarf exception handling. 12// 13//===----------------------------------------------------------------------===// 14 15#define DEBUG_TYPE "dwarfehprepare" 16#include "llvm/Function.h" 17#include "llvm/Instructions.h" 18#include "llvm/IntrinsicInst.h" 19#include "llvm/Module.h" 20#include "llvm/Pass.h" 21#include "llvm/ADT/Statistic.h" 22#include "llvm/Analysis/Dominators.h" 23#include "llvm/CodeGen/Passes.h" 24#include "llvm/MC/MCAsmInfo.h" 25#include "llvm/Target/TargetLowering.h" 26#include "llvm/Transforms/Utils/BasicBlockUtils.h" 27#include "llvm/Transforms/Utils/PromoteMemToReg.h" 28using namespace llvm; 29 30STATISTIC(NumLandingPadsSplit, "Number of landing pads split"); 31STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); 32STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); 33STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced"); 34 35namespace { 36 class DwarfEHPrepare : public FunctionPass { 37 const TargetMachine *TM; 38 const TargetLowering *TLI; 39 bool CompileFast; 40 41 // The eh.exception intrinsic. 42 Function *ExceptionValueIntrinsic; 43 44 // The eh.selector intrinsic. 45 Function *SelectorIntrinsic; 46 47 // _Unwind_Resume_or_Rethrow call. 48 Constant *URoR; 49 50 // The EH language-specific catch-all type. 51 GlobalVariable *EHCatchAllValue; 52 53 // _Unwind_Resume or the target equivalent. 54 Constant *RewindFunction; 55 56 // Dominator info is used when turning stack temporaries into registers. 57 DominatorTree *DT; 58 DominanceFrontier *DF; 59 60 // The function we are running on. 61 Function *F; 62 63 // The landing pads for this function. 64 typedef SmallPtrSet<BasicBlock*, 8> BBSet; 65 BBSet LandingPads; 66 67 // Stack temporary used to hold eh.exception values. 68 AllocaInst *ExceptionValueVar; 69 70 bool NormalizeLandingPads(); 71 bool LowerUnwinds(); 72 bool MoveExceptionValueCalls(); 73 bool FinishStackTemporaries(); 74 bool PromoteStackTemporaries(); 75 76 Instruction *CreateExceptionValueCall(BasicBlock *BB); 77 Instruction *CreateValueLoad(BasicBlock *BB); 78 79 /// CreateReadOfExceptionValue - Return the result of the eh.exception 80 /// intrinsic by calling the intrinsic if in a landing pad, or loading it 81 /// from the exception value variable otherwise. 82 Instruction *CreateReadOfExceptionValue(BasicBlock *BB) { 83 return LandingPads.count(BB) ? 84 CreateExceptionValueCall(BB) : CreateValueLoad(BB); 85 } 86 87 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still 88 /// use the ".llvm.eh.catch.all.value" call need to convert to using its 89 /// initializer instead. 90 bool CleanupSelectors(); 91 92 bool HasCatchAllInSelector(IntrinsicInst *); 93 94 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 95 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); 96 97 /// FindAllURoRInvokes - Find all URoR invokes in the function. 98 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); 99 100 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" 101 /// calls. The "unwind" part of these invokes jump to a landing pad within 102 /// the current function. This is a candidate to merge the selector 103 /// associated with the URoR invoke with the one from the URoR's landing 104 /// pad. 105 bool HandleURoRInvokes(); 106 107 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated 108 /// with the eh.exception call. This recursively looks past instructions 109 /// which don't change the EH pointer value, like casts or PHI nodes. 110 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 111 SmallPtrSet<IntrinsicInst*, 8> &SelCalls); 112 113 /// DoMem2RegPromotion - Take an alloca call and promote it from memory to a 114 /// register. 115 bool DoMem2RegPromotion(Value *V) { 116 AllocaInst *AI = dyn_cast<AllocaInst>(V); 117 if (!AI || !isAllocaPromotable(AI)) return false; 118 119 // Turn the alloca into a register. 120 std::vector<AllocaInst*> Allocas(1, AI); 121 PromoteMemToReg(Allocas, *DT, *DF); 122 return true; 123 } 124 125 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst. 126 bool PromoteStoreInst(StoreInst *SI) { 127 if (!SI || !DT || !DF) return false; 128 if (DoMem2RegPromotion(SI->getOperand(1))) 129 return true; 130 return false; 131 } 132 133 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a 134 /// register. This should get rid of the store and subsequent loads. 135 bool PromoteEHPtrStore(IntrinsicInst *II) { 136 if (!DT || !DF) return false; 137 138 bool Changed = false; 139 StoreInst *SI; 140 141 while (1) { 142 SI = 0; 143 for (Value::use_iterator 144 I = II->use_begin(), E = II->use_end(); I != E; ++I) { 145 SI = dyn_cast<StoreInst>(I); 146 if (SI) break; 147 } 148 149 if (!PromoteStoreInst(SI)) 150 break; 151 152 Changed = true; 153 } 154 155 return false; 156 } 157 158 public: 159 static char ID; // Pass identification, replacement for typeid. 160 DwarfEHPrepare(const TargetMachine *tm, bool fast) : 161 FunctionPass(&ID), TM(tm), TLI(TM->getTargetLowering()), 162 CompileFast(fast), 163 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 164 URoR(0), EHCatchAllValue(0), RewindFunction(0) {} 165 166 virtual bool runOnFunction(Function &Fn); 167 168 // getAnalysisUsage - We need dominance frontiers for memory promotion. 169 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 170 if (!CompileFast) 171 AU.addRequired<DominatorTree>(); 172 AU.addPreserved<DominatorTree>(); 173 if (!CompileFast) 174 AU.addRequired<DominanceFrontier>(); 175 AU.addPreserved<DominanceFrontier>(); 176 } 177 178 const char *getPassName() const { 179 return "Exception handling preparation"; 180 } 181 182 }; 183} // end anonymous namespace 184 185char DwarfEHPrepare::ID = 0; 186 187FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm, bool fast) { 188 return new DwarfEHPrepare(tm, fast); 189} 190 191/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 192/// catch-all. 193bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 194 if (!EHCatchAllValue) return false; 195 196 unsigned OpIdx = II->getNumOperands() - 1; 197 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getOperand(OpIdx)); 198 return GV == EHCatchAllValue; 199} 200 201/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 202void DwarfEHPrepare:: 203FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 204 for (Value::use_iterator 205 I = SelectorIntrinsic->use_begin(), 206 E = SelectorIntrinsic->use_end(); I != E; ++I) { 207 IntrinsicInst *II = cast<IntrinsicInst>(I); 208 209 if (II->getParent()->getParent() != F) 210 continue; 211 212 if (!HasCatchAllInSelector(II)) 213 Sels.insert(II); 214 } 215} 216 217/// FindAllURoRInvokes - Find all URoR invokes in the function. 218void DwarfEHPrepare:: 219FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 220 for (Value::use_iterator 221 I = URoR->use_begin(), 222 E = URoR->use_end(); I != E; ++I) { 223 if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 224 URoRInvokes.insert(II); 225 } 226} 227 228/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 229/// the ".llvm.eh.catch.all.value" call need to convert to using its 230/// initializer instead. 231bool DwarfEHPrepare::CleanupSelectors() { 232 if (!EHCatchAllValue) return false; 233 234 if (!SelectorIntrinsic) { 235 SelectorIntrinsic = 236 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 237 if (!SelectorIntrinsic) return false; 238 } 239 240 bool Changed = false; 241 for (Value::use_iterator 242 I = SelectorIntrinsic->use_begin(), 243 E = SelectorIntrinsic->use_end(); I != E; ++I) { 244 IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(I); 245 if (!Sel || Sel->getParent()->getParent() != F) continue; 246 247 // Index of the ".llvm.eh.catch.all.value" variable. 248 unsigned OpIdx = Sel->getNumOperands() - 1; 249 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getOperand(OpIdx)); 250 if (GV != EHCatchAllValue) continue; 251 Sel->setOperand(OpIdx, EHCatchAllValue->getInitializer()); 252 Changed = true; 253 } 254 255 return Changed; 256} 257 258/// FindSelectorAndURoR - Find the eh.selector call associated with the 259/// eh.exception call. And indicate if there is a URoR "invoke" associated with 260/// the eh.exception call. This recursively looks past instructions which don't 261/// change the EH pointer value, like casts or PHI nodes. 262bool 263DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 264 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) { 265 SmallPtrSet<PHINode*, 32> SeenPHIs; 266 bool Changed = false; 267 268 restart: 269 for (Value::use_iterator 270 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 271 Instruction *II = dyn_cast<Instruction>(I); 272 if (!II || II->getParent()->getParent() != F) continue; 273 274 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 275 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 276 SelCalls.insert(Sel); 277 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 278 if (Invoke->getCalledFunction() == URoR) 279 URoRInvoke = true; 280 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 281 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls); 282 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) { 283 if (!PromoteStoreInst(SI)) continue; 284 Changed = true; 285 SeenPHIs.clear(); 286 goto restart; // Uses may have changed, restart loop. 287 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 288 if (SeenPHIs.insert(PN)) 289 // Don't process a PHI node more than once. 290 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls); 291 } 292 } 293 294 return Changed; 295} 296 297/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The 298/// "unwind" part of these invokes jump to a landing pad within the current 299/// function. This is a candidate to merge the selector associated with the URoR 300/// invoke with the one from the URoR's landing pad. 301bool DwarfEHPrepare::HandleURoRInvokes() { 302 if (!DT) return CleanupSelectors(); // We require DominatorTree information. 303 304 if (!EHCatchAllValue) { 305 EHCatchAllValue = 306 F->getParent()->getNamedGlobal(".llvm.eh.catch.all.value"); 307 if (!EHCatchAllValue) return false; 308 } 309 310 if (!SelectorIntrinsic) { 311 SelectorIntrinsic = 312 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 313 if (!SelectorIntrinsic) return false; 314 } 315 316 if (!URoR) { 317 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 318 if (!URoR) return CleanupSelectors(); 319 } 320 321 SmallPtrSet<IntrinsicInst*, 32> Sels; 322 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 323 FindAllCleanupSelectors(Sels); 324 FindAllURoRInvokes(URoRInvokes); 325 326 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; 327 328 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 329 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { 330 const BasicBlock *SelBB = (*SI)->getParent(); 331 for (SmallPtrSet<InvokeInst*, 32>::iterator 332 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { 333 const BasicBlock *URoRBB = (*UI)->getParent(); 334 if (SelBB == URoRBB || DT->dominates(SelBB, URoRBB)) { 335 SelsToConvert.insert(*SI); 336 break; 337 } 338 } 339 } 340 341 bool Changed = false; 342 343 if (Sels.size() != SelsToConvert.size()) { 344 // If we haven't been able to convert all of the clean-up selectors, then 345 // loop through the slow way to see if they still need to be converted. 346 if (!ExceptionValueIntrinsic) { 347 ExceptionValueIntrinsic = 348 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); 349 if (!ExceptionValueIntrinsic) return CleanupSelectors(); 350 } 351 352 for (Value::use_iterator 353 I = ExceptionValueIntrinsic->use_begin(), 354 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 355 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(I); 356 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 357 358 Changed |= PromoteEHPtrStore(EHPtr); 359 360 bool URoRInvoke = false; 361 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 362 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls); 363 364 if (URoRInvoke) { 365 // This EH pointer is being used by an invoke of an URoR instruction and 366 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 367 // need to convert it to a 'catch-all'. 368 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 369 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 370 if (!HasCatchAllInSelector(*SI)) 371 SelsToConvert.insert(*SI); 372 } 373 } 374 } 375 376 if (!SelsToConvert.empty()) { 377 // Convert all clean-up eh.selectors, which are associated with "invokes" of 378 // URoR calls, into catch-all eh.selectors. 379 Changed = true; 380 381 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 382 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 383 SI != SE; ++SI) { 384 IntrinsicInst *II = *SI; 385 SmallVector<Value*, 8> Args; 386 387 // Use the exception object pointer and the personality function 388 // from the original selector. 389 Args.push_back(II->getOperand(1)); // Exception object pointer. 390 Args.push_back(II->getOperand(2)); // Personality function. 391 392 unsigned I = 3; 393 unsigned E = II->getNumOperands() - 394 (isa<ConstantInt>(II->getOperand(II->getNumOperands() - 1)) ? 1 : 0); 395 396 // Add in any filter IDs. 397 for (; I < E; ++I) 398 Args.push_back(II->getOperand(I)); 399 400 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 401 402 CallInst *NewSelector = 403 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 404 "eh.sel.catch.all", II); 405 406 NewSelector->setTailCall(II->isTailCall()); 407 NewSelector->setAttributes(II->getAttributes()); 408 NewSelector->setCallingConv(II->getCallingConv()); 409 410 II->replaceAllUsesWith(NewSelector); 411 II->eraseFromParent(); 412 } 413 } 414 415 Changed |= CleanupSelectors(); 416 return Changed; 417} 418 419/// NormalizeLandingPads - Normalize and discover landing pads, noting them 420/// in the LandingPads set. A landing pad is normal if the only CFG edges 421/// that end at it are unwind edges from invoke instructions. If we inlined 422/// through an invoke we could have a normal branch from the previous 423/// unwind block through to the landing pad for the original invoke. 424/// Abnormal landing pads are fixed up by redirecting all unwind edges to 425/// a new basic block which falls through to the original. 426bool DwarfEHPrepare::NormalizeLandingPads() { 427 bool Changed = false; 428 429 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 430 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 431 432 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 433 TerminatorInst *TI = I->getTerminator(); 434 if (!isa<InvokeInst>(TI)) 435 continue; 436 BasicBlock *LPad = TI->getSuccessor(1); 437 // Skip landing pads that have already been normalized. 438 if (LandingPads.count(LPad)) 439 continue; 440 441 // Check that only invoke unwind edges end at the landing pad. 442 bool OnlyUnwoundTo = true; 443 bool SwitchOK = usingSjLjEH; 444 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 445 PI != PE; ++PI) { 446 TerminatorInst *PT = (*PI)->getTerminator(); 447 // The SjLj dispatch block uses a switch instruction. This is effectively 448 // an unwind edge, so we can disregard it here. There will only ever 449 // be one dispatch, however, so if there are multiple switches, one 450 // of them truly is a normal edge, not an unwind edge. 451 if (SwitchOK && isa<SwitchInst>(PT)) { 452 SwitchOK = false; 453 continue; 454 } 455 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 456 OnlyUnwoundTo = false; 457 break; 458 } 459 } 460 461 if (OnlyUnwoundTo) { 462 // Only unwind edges lead to the landing pad. Remember the landing pad. 463 LandingPads.insert(LPad); 464 continue; 465 } 466 467 // At least one normal edge ends at the landing pad. Redirect the unwind 468 // edges to a new basic block which falls through into this one. 469 470 // Create the new basic block. 471 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 472 LPad->getName() + "_unwind_edge"); 473 474 // Insert it into the function right before the original landing pad. 475 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 476 477 // Redirect unwind edges from the original landing pad to NewBB. 478 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 479 TerminatorInst *PT = (*PI++)->getTerminator(); 480 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 481 // Unwind to the new block. 482 PT->setSuccessor(1, NewBB); 483 } 484 485 // If there are any PHI nodes in LPad, we need to update them so that they 486 // merge incoming values from NewBB instead. 487 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 488 PHINode *PN = cast<PHINode>(II); 489 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 490 491 // Check to see if all of the values coming in via unwind edges are the 492 // same. If so, we don't need to create a new PHI node. 493 Value *InVal = PN->getIncomingValueForBlock(*PB); 494 for (pred_iterator PI = PB; PI != PE; ++PI) { 495 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 496 InVal = 0; 497 break; 498 } 499 } 500 501 if (InVal == 0) { 502 // Different unwind edges have different values. Create a new PHI node 503 // in NewBB. 504 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", 505 NewBB); 506 // Add an entry for each unwind edge, using the value from the old PHI. 507 for (pred_iterator PI = PB; PI != PE; ++PI) 508 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 509 510 // Now use this new PHI as the common incoming value for NewBB in PN. 511 InVal = NewPN; 512 } 513 514 // Revector exactly one entry in the PHI node to come from NewBB 515 // and delete all other entries that come from unwind edges. If 516 // there are both normal and unwind edges from the same predecessor, 517 // this leaves an entry for the normal edge. 518 for (pred_iterator PI = PB; PI != PE; ++PI) 519 PN->removeIncomingValue(*PI); 520 PN->addIncoming(InVal, NewBB); 521 } 522 523 // Add a fallthrough from NewBB to the original landing pad. 524 BranchInst::Create(LPad, NewBB); 525 526 // Now update DominatorTree and DominanceFrontier analysis information. 527 if (DT) 528 DT->splitBlock(NewBB); 529 if (DF) 530 DF->splitBlock(NewBB); 531 532 // Remember the newly constructed landing pad. The original landing pad 533 // LPad is no longer a landing pad now that all unwind edges have been 534 // revectored to NewBB. 535 LandingPads.insert(NewBB); 536 ++NumLandingPadsSplit; 537 Changed = true; 538 } 539 540 return Changed; 541} 542 543/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 544/// rethrowing any previously caught exception. This will crash horribly 545/// at runtime if there is no such exception: using unwind to throw a new 546/// exception is currently not supported. 547bool DwarfEHPrepare::LowerUnwinds() { 548 SmallVector<TerminatorInst*, 16> UnwindInsts; 549 550 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 551 TerminatorInst *TI = I->getTerminator(); 552 if (isa<UnwindInst>(TI)) 553 UnwindInsts.push_back(TI); 554 } 555 556 if (UnwindInsts.empty()) return false; 557 558 // Find the rewind function if we didn't already. 559 if (!RewindFunction) { 560 LLVMContext &Ctx = UnwindInsts[0]->getContext(); 561 std::vector<const Type*> 562 Params(1, Type::getInt8PtrTy(Ctx)); 563 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 564 Params, false); 565 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 566 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 567 } 568 569 bool Changed = false; 570 571 for (SmallVectorImpl<TerminatorInst*>::iterator 572 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { 573 TerminatorInst *TI = *I; 574 575 // Replace the unwind instruction with a call to _Unwind_Resume (or the 576 // appropriate target equivalent) followed by an UnreachableInst. 577 578 // Create the call... 579 CallInst *CI = CallInst::Create(RewindFunction, 580 CreateReadOfExceptionValue(TI->getParent()), 581 "", TI); 582 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 583 // ...followed by an UnreachableInst. 584 new UnreachableInst(TI->getContext(), TI); 585 586 // Nuke the unwind instruction. 587 TI->eraseFromParent(); 588 ++NumUnwindsLowered; 589 Changed = true; 590 } 591 592 return Changed; 593} 594 595/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 596/// landing pads by replacing calls outside of landing pads with loads from a 597/// stack temporary. Move eh.exception calls inside landing pads to the start 598/// of the landing pad (optional, but may make things simpler for later passes). 599bool DwarfEHPrepare::MoveExceptionValueCalls() { 600 // If the eh.exception intrinsic is not declared in the module then there is 601 // nothing to do. Speed up compilation by checking for this common case. 602 if (!ExceptionValueIntrinsic && 603 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 604 return false; 605 606 bool Changed = false; 607 608 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { 609 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) 610 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) 611 if (CI->getIntrinsicID() == Intrinsic::eh_exception) { 612 if (!CI->use_empty()) { 613 Value *ExceptionValue = CreateReadOfExceptionValue(BB); 614 if (CI == ExceptionValue) { 615 // The call was at the start of a landing pad - leave it alone. 616 assert(LandingPads.count(BB) && 617 "Created eh.exception call outside landing pad!"); 618 continue; 619 } 620 CI->replaceAllUsesWith(ExceptionValue); 621 } 622 CI->eraseFromParent(); 623 ++NumExceptionValuesMoved; 624 Changed = true; 625 } 626 } 627 628 return Changed; 629} 630 631/// FinishStackTemporaries - If we introduced a stack variable to hold the 632/// exception value then initialize it in each landing pad. 633bool DwarfEHPrepare::FinishStackTemporaries() { 634 if (!ExceptionValueVar) 635 // Nothing to do. 636 return false; 637 638 bool Changed = false; 639 640 // Make sure that there is a store of the exception value at the start of 641 // each landing pad. 642 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 643 LI != LE; ++LI) { 644 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI); 645 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar); 646 Store->insertAfter(ExceptionValue); 647 Changed = true; 648 } 649 650 return Changed; 651} 652 653/// PromoteStackTemporaries - Turn any stack temporaries we introduced into 654/// registers if possible. 655bool DwarfEHPrepare::PromoteStackTemporaries() { 656 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) { 657 // Turn the exception temporary into registers and phi nodes if possible. 658 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar); 659 PromoteMemToReg(Allocas, *DT, *DF); 660 return true; 661 } 662 return false; 663} 664 665/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 666/// the start of the basic block (unless there already is one, in which case 667/// the existing call is returned). 668Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 669 Instruction *Start = BB->getFirstNonPHIOrDbg(); 670 // Is this a call to eh.exception? 671 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 672 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 673 // Reuse the existing call. 674 return Start; 675 676 // Find the eh.exception intrinsic if we didn't already. 677 if (!ExceptionValueIntrinsic) 678 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 679 Intrinsic::eh_exception); 680 681 // Create the call. 682 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 683} 684 685/// CreateValueLoad - Insert a load of the exception value stack variable 686/// (creating it if necessary) at the start of the basic block (unless 687/// there already is a load, in which case the existing load is returned). 688Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) { 689 Instruction *Start = BB->getFirstNonPHIOrDbg(); 690 // Is this a load of the exception temporary? 691 if (ExceptionValueVar) 692 if (LoadInst* LI = dyn_cast<LoadInst>(Start)) 693 if (LI->getPointerOperand() == ExceptionValueVar) 694 // Reuse the existing load. 695 return Start; 696 697 // Create the temporary if we didn't already. 698 if (!ExceptionValueVar) { 699 ExceptionValueVar = new AllocaInst(PointerType::getUnqual( 700 Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin()); 701 ++NumStackTempsIntroduced; 702 } 703 704 // Load the value. 705 return new LoadInst(ExceptionValueVar, "eh.value.load", Start); 706} 707 708bool DwarfEHPrepare::runOnFunction(Function &Fn) { 709 bool Changed = false; 710 711 // Initialize internal state. 712 DT = getAnalysisIfAvailable<DominatorTree>(); 713 DF = getAnalysisIfAvailable<DominanceFrontier>(); 714 ExceptionValueVar = 0; 715 F = &Fn; 716 717 // Ensure that only unwind edges end at landing pads (a landing pad is a 718 // basic block where an invoke unwind edge ends). 719 Changed |= NormalizeLandingPads(); 720 721 // Turn unwind instructions into libcalls. 722 Changed |= LowerUnwinds(); 723 724 // TODO: Move eh.selector calls to landing pads and combine them. 725 726 // Move eh.exception calls to landing pads. 727 Changed |= MoveExceptionValueCalls(); 728 729 // Initialize any stack temporaries we introduced. 730 Changed |= FinishStackTemporaries(); 731 732 // Turn any stack temporaries into registers if possible. 733 if (!CompileFast) 734 Changed |= PromoteStackTemporaries(); 735 736 Changed |= HandleURoRInvokes(); 737 738 LandingPads.clear(); 739 740 return Changed; 741} 742