DwarfEHPrepare.cpp revision 619acdc63ab0a47d125dca0591285c8ac4c9ed20
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/Support/CallSite.h" 26#include "llvm/Target/TargetLowering.h" 27#include "llvm/Transforms/Utils/BasicBlockUtils.h" 28#include "llvm/Transforms/Utils/PromoteMemToReg.h" 29using namespace llvm; 30 31STATISTIC(NumLandingPadsSplit, "Number of landing pads split"); 32STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); 33STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); 34STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced"); 35 36namespace { 37 class DwarfEHPrepare : public FunctionPass { 38 const TargetMachine *TM; 39 const TargetLowering *TLI; 40 bool CompileFast; 41 42 // The eh.exception intrinsic. 43 Function *ExceptionValueIntrinsic; 44 45 // The eh.selector intrinsic. 46 Function *SelectorIntrinsic; 47 48 // _Unwind_Resume_or_Rethrow call. 49 Constant *URoR; 50 51 // The EH language-specific catch-all type. 52 GlobalVariable *EHCatchAllValue; 53 54 // _Unwind_Resume or the target equivalent. 55 Constant *RewindFunction; 56 57 // Dominator info is used when turning stack temporaries into registers. 58 DominatorTree *DT; 59 DominanceFrontier *DF; 60 61 // The function we are running on. 62 Function *F; 63 64 // The landing pads for this function. 65 typedef SmallPtrSet<BasicBlock*, 8> BBSet; 66 BBSet LandingPads; 67 68 // Stack temporary used to hold eh.exception values. 69 AllocaInst *ExceptionValueVar; 70 71 bool NormalizeLandingPads(); 72 bool LowerUnwinds(); 73 bool MoveExceptionValueCalls(); 74 bool FinishStackTemporaries(); 75 bool PromoteStackTemporaries(); 76 77 Instruction *CreateExceptionValueCall(BasicBlock *BB); 78 Instruction *CreateValueLoad(BasicBlock *BB); 79 80 /// CreateReadOfExceptionValue - Return the result of the eh.exception 81 /// intrinsic by calling the intrinsic if in a landing pad, or loading it 82 /// from the exception value variable otherwise. 83 Instruction *CreateReadOfExceptionValue(BasicBlock *BB) { 84 return LandingPads.count(BB) ? 85 CreateExceptionValueCall(BB) : CreateValueLoad(BB); 86 } 87 88 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still 89 /// use the "llvm.eh.catch.all.value" call need to convert to using its 90 /// initializer instead. 91 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); 92 93 bool HasCatchAllInSelector(IntrinsicInst *); 94 95 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 96 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 97 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels); 98 99 /// FindAllURoRInvokes - Find all URoR invokes in the function. 100 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); 101 102 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" 103 /// calls. The "unwind" part of these invokes jump to a landing pad within 104 /// the current function. This is a candidate to merge the selector 105 /// associated with the URoR invoke with the one from the URoR's landing 106 /// pad. 107 bool HandleURoRInvokes(); 108 109 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated 110 /// with the eh.exception call. This recursively looks past instructions 111 /// which don't change the EH pointer value, like casts or PHI nodes. 112 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 113 SmallPtrSet<IntrinsicInst*, 8> &SelCalls); 114 115 /// DoMem2RegPromotion - Take an alloca call and promote it from memory to a 116 /// register. 117 bool DoMem2RegPromotion(Value *V) { 118 AllocaInst *AI = dyn_cast<AllocaInst>(V); 119 if (!AI || !isAllocaPromotable(AI)) return false; 120 121 // Turn the alloca into a register. 122 std::vector<AllocaInst*> Allocas(1, AI); 123 PromoteMemToReg(Allocas, *DT, *DF); 124 return true; 125 } 126 127 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst. 128 bool PromoteStoreInst(StoreInst *SI) { 129 if (!SI || !DT || !DF) return false; 130 if (DoMem2RegPromotion(SI->getOperand(1))) 131 return true; 132 return false; 133 } 134 135 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a 136 /// register. This should get rid of the store and subsequent loads. 137 bool PromoteEHPtrStore(IntrinsicInst *II) { 138 if (!DT || !DF) return false; 139 140 bool Changed = false; 141 StoreInst *SI; 142 143 while (1) { 144 SI = 0; 145 for (Value::use_iterator 146 I = II->use_begin(), E = II->use_end(); I != E; ++I) { 147 SI = dyn_cast<StoreInst>(*I); 148 if (SI) break; 149 } 150 151 if (!PromoteStoreInst(SI)) 152 break; 153 154 Changed = true; 155 } 156 157 return Changed; 158 } 159 160 public: 161 static char ID; // Pass identification, replacement for typeid. 162 DwarfEHPrepare(const TargetMachine *tm, bool fast) : 163 FunctionPass(&ID), TM(tm), TLI(TM->getTargetLowering()), 164 CompileFast(fast), 165 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 166 URoR(0), EHCatchAllValue(0), RewindFunction(0) {} 167 168 virtual bool runOnFunction(Function &Fn); 169 170 // getAnalysisUsage - We need dominance frontiers for memory promotion. 171 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 172 if (!CompileFast) 173 AU.addRequired<DominatorTree>(); 174 AU.addPreserved<DominatorTree>(); 175 if (!CompileFast) 176 AU.addRequired<DominanceFrontier>(); 177 AU.addPreserved<DominanceFrontier>(); 178 } 179 180 const char *getPassName() const { 181 return "Exception handling preparation"; 182 } 183 184 }; 185} // end anonymous namespace 186 187char DwarfEHPrepare::ID = 0; 188 189FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm, bool fast) { 190 return new DwarfEHPrepare(tm, fast); 191} 192 193/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 194/// catch-all. 195bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 196 if (!EHCatchAllValue) return false; 197 198 unsigned ArgIdx = II->getNumArgOperands() - 1; 199 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 200 return GV == EHCatchAllValue; 201} 202 203/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 204void DwarfEHPrepare:: 205FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 206 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 207 for (Value::use_iterator 208 I = SelectorIntrinsic->use_begin(), 209 E = SelectorIntrinsic->use_end(); I != E; ++I) { 210 IntrinsicInst *II = cast<IntrinsicInst>(*I); 211 212 if (II->getParent()->getParent() != F) 213 continue; 214 215 if (!HasCatchAllInSelector(II)) 216 Sels.insert(II); 217 else 218 CatchAllSels.insert(II); 219 } 220} 221 222/// FindAllURoRInvokes - Find all URoR invokes in the function. 223void DwarfEHPrepare:: 224FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 225 for (Value::use_iterator 226 I = URoR->use_begin(), 227 E = URoR->use_end(); I != E; ++I) { 228 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 229 URoRInvokes.insert(II); 230 } 231} 232 233/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 234/// the "llvm.eh.catch.all.value" call need to convert to using its 235/// initializer instead. 236bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 237 if (!EHCatchAllValue) return false; 238 239 if (!SelectorIntrinsic) { 240 SelectorIntrinsic = 241 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 242 if (!SelectorIntrinsic) return false; 243 } 244 245 bool Changed = false; 246 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 247 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 248 IntrinsicInst *Sel = *I; 249 250 // Index of the "llvm.eh.catch.all.value" variable. 251 unsigned OpIdx = Sel->getNumArgOperands() - 1; 252 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 253 if (GV != EHCatchAllValue) continue; 254 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 255 Changed = true; 256 } 257 258 return Changed; 259} 260 261/// FindSelectorAndURoR - Find the eh.selector call associated with the 262/// eh.exception call. And indicate if there is a URoR "invoke" associated with 263/// the eh.exception call. This recursively looks past instructions which don't 264/// change the EH pointer value, like casts or PHI nodes. 265bool 266DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 267 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) { 268 SmallPtrSet<PHINode*, 32> SeenPHIs; 269 bool Changed = false; 270 271 restart: 272 for (Value::use_iterator 273 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 274 Instruction *II = dyn_cast<Instruction>(*I); 275 if (!II || II->getParent()->getParent() != F) continue; 276 277 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 278 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 279 SelCalls.insert(Sel); 280 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 281 if (Invoke->getCalledFunction() == URoR) 282 URoRInvoke = true; 283 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 284 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls); 285 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) { 286 if (!PromoteStoreInst(SI)) continue; 287 Changed = true; 288 SeenPHIs.clear(); 289 goto restart; // Uses may have changed, restart loop. 290 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 291 if (SeenPHIs.insert(PN)) 292 // Don't process a PHI node more than once. 293 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls); 294 } 295 } 296 297 return Changed; 298} 299 300/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The 301/// "unwind" part of these invokes jump to a landing pad within the current 302/// function. This is a candidate to merge the selector associated with the URoR 303/// invoke with the one from the URoR's landing pad. 304bool DwarfEHPrepare::HandleURoRInvokes() { 305 if (!EHCatchAllValue) { 306 EHCatchAllValue = 307 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 308 if (!EHCatchAllValue) return false; 309 } 310 311 if (!SelectorIntrinsic) { 312 SelectorIntrinsic = 313 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 314 if (!SelectorIntrinsic) return false; 315 } 316 317 SmallPtrSet<IntrinsicInst*, 32> Sels; 318 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 319 FindAllCleanupSelectors(Sels, CatchAllSels); 320 321 if (!DT) 322 // We require DominatorTree information. 323 return CleanupSelectors(CatchAllSels); 324 325 if (!URoR) { 326 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 327 if (!URoR) return CleanupSelectors(CatchAllSels); 328 } 329 330 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 331 FindAllURoRInvokes(URoRInvokes); 332 333 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; 334 335 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 336 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { 337 const BasicBlock *SelBB = (*SI)->getParent(); 338 for (SmallPtrSet<InvokeInst*, 32>::iterator 339 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { 340 const BasicBlock *URoRBB = (*UI)->getParent(); 341 if (DT->dominates(SelBB, URoRBB)) { 342 SelsToConvert.insert(*SI); 343 break; 344 } 345 } 346 } 347 348 bool Changed = false; 349 350 if (Sels.size() != SelsToConvert.size()) { 351 // If we haven't been able to convert all of the clean-up selectors, then 352 // loop through the slow way to see if they still need to be converted. 353 if (!ExceptionValueIntrinsic) { 354 ExceptionValueIntrinsic = 355 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); 356 if (!ExceptionValueIntrinsic) 357 return CleanupSelectors(CatchAllSels); 358 } 359 360 for (Value::use_iterator 361 I = ExceptionValueIntrinsic->use_begin(), 362 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 363 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); 364 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 365 366 Changed |= PromoteEHPtrStore(EHPtr); 367 368 bool URoRInvoke = false; 369 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 370 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls); 371 372 if (URoRInvoke) { 373 // This EH pointer is being used by an invoke of an URoR instruction and 374 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 375 // need to convert it to a 'catch-all'. 376 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 377 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 378 if (!HasCatchAllInSelector(*SI)) 379 SelsToConvert.insert(*SI); 380 } 381 } 382 } 383 384 if (!SelsToConvert.empty()) { 385 // Convert all clean-up eh.selectors, which are associated with "invokes" of 386 // URoR calls, into catch-all eh.selectors. 387 Changed = true; 388 389 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 390 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 391 SI != SE; ++SI) { 392 IntrinsicInst *II = *SI; 393 394 // Use the exception object pointer and the personality function 395 // from the original selector. 396 CallSite CS(II); 397 IntrinsicInst::op_iterator I = CS.arg_begin(); 398 IntrinsicInst::op_iterator E = CS.arg_end(); 399 IntrinsicInst::op_iterator B = prior(E); 400 401 // Exclude last argument if it is an integer. 402 if (isa<ConstantInt>(B)) E = B; 403 404 // Add exception object pointer (front). 405 // Add personality function (next). 406 // Add in any filter IDs (rest). 407 SmallVector<Value*, 8> Args(I, E); 408 409 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 410 411 CallInst *NewSelector = 412 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 413 "eh.sel.catch.all", II); 414 415 NewSelector->setTailCall(II->isTailCall()); 416 NewSelector->setAttributes(II->getAttributes()); 417 NewSelector->setCallingConv(II->getCallingConv()); 418 419 II->replaceAllUsesWith(NewSelector); 420 II->eraseFromParent(); 421 } 422 } 423 424 Changed |= CleanupSelectors(CatchAllSels); 425 return Changed; 426} 427 428/// NormalizeLandingPads - Normalize and discover landing pads, noting them 429/// in the LandingPads set. A landing pad is normal if the only CFG edges 430/// that end at it are unwind edges from invoke instructions. If we inlined 431/// through an invoke we could have a normal branch from the previous 432/// unwind block through to the landing pad for the original invoke. 433/// Abnormal landing pads are fixed up by redirecting all unwind edges to 434/// a new basic block which falls through to the original. 435bool DwarfEHPrepare::NormalizeLandingPads() { 436 bool Changed = false; 437 438 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 439 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 440 441 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 442 TerminatorInst *TI = I->getTerminator(); 443 if (!isa<InvokeInst>(TI)) 444 continue; 445 BasicBlock *LPad = TI->getSuccessor(1); 446 // Skip landing pads that have already been normalized. 447 if (LandingPads.count(LPad)) 448 continue; 449 450 // Check that only invoke unwind edges end at the landing pad. 451 bool OnlyUnwoundTo = true; 452 bool SwitchOK = usingSjLjEH; 453 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 454 PI != PE; ++PI) { 455 TerminatorInst *PT = (*PI)->getTerminator(); 456 // The SjLj dispatch block uses a switch instruction. This is effectively 457 // an unwind edge, so we can disregard it here. There will only ever 458 // be one dispatch, however, so if there are multiple switches, one 459 // of them truly is a normal edge, not an unwind edge. 460 if (SwitchOK && isa<SwitchInst>(PT)) { 461 SwitchOK = false; 462 continue; 463 } 464 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 465 OnlyUnwoundTo = false; 466 break; 467 } 468 } 469 470 if (OnlyUnwoundTo) { 471 // Only unwind edges lead to the landing pad. Remember the landing pad. 472 LandingPads.insert(LPad); 473 continue; 474 } 475 476 // At least one normal edge ends at the landing pad. Redirect the unwind 477 // edges to a new basic block which falls through into this one. 478 479 // Create the new basic block. 480 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 481 LPad->getName() + "_unwind_edge"); 482 483 // Insert it into the function right before the original landing pad. 484 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 485 486 // Redirect unwind edges from the original landing pad to NewBB. 487 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 488 TerminatorInst *PT = (*PI++)->getTerminator(); 489 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 490 // Unwind to the new block. 491 PT->setSuccessor(1, NewBB); 492 } 493 494 // If there are any PHI nodes in LPad, we need to update them so that they 495 // merge incoming values from NewBB instead. 496 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 497 PHINode *PN = cast<PHINode>(II); 498 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 499 500 // Check to see if all of the values coming in via unwind edges are the 501 // same. If so, we don't need to create a new PHI node. 502 Value *InVal = PN->getIncomingValueForBlock(*PB); 503 for (pred_iterator PI = PB; PI != PE; ++PI) { 504 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 505 InVal = 0; 506 break; 507 } 508 } 509 510 if (InVal == 0) { 511 // Different unwind edges have different values. Create a new PHI node 512 // in NewBB. 513 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", 514 NewBB); 515 // Add an entry for each unwind edge, using the value from the old PHI. 516 for (pred_iterator PI = PB; PI != PE; ++PI) 517 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 518 519 // Now use this new PHI as the common incoming value for NewBB in PN. 520 InVal = NewPN; 521 } 522 523 // Revector exactly one entry in the PHI node to come from NewBB 524 // and delete all other entries that come from unwind edges. If 525 // there are both normal and unwind edges from the same predecessor, 526 // this leaves an entry for the normal edge. 527 for (pred_iterator PI = PB; PI != PE; ++PI) 528 PN->removeIncomingValue(*PI); 529 PN->addIncoming(InVal, NewBB); 530 } 531 532 // Add a fallthrough from NewBB to the original landing pad. 533 BranchInst::Create(LPad, NewBB); 534 535 // Now update DominatorTree and DominanceFrontier analysis information. 536 if (DT) 537 DT->splitBlock(NewBB); 538 if (DF) 539 DF->splitBlock(NewBB); 540 541 // Remember the newly constructed landing pad. The original landing pad 542 // LPad is no longer a landing pad now that all unwind edges have been 543 // revectored to NewBB. 544 LandingPads.insert(NewBB); 545 ++NumLandingPadsSplit; 546 Changed = true; 547 } 548 549 return Changed; 550} 551 552/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 553/// rethrowing any previously caught exception. This will crash horribly 554/// at runtime if there is no such exception: using unwind to throw a new 555/// exception is currently not supported. 556bool DwarfEHPrepare::LowerUnwinds() { 557 SmallVector<TerminatorInst*, 16> UnwindInsts; 558 559 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 560 TerminatorInst *TI = I->getTerminator(); 561 if (isa<UnwindInst>(TI)) 562 UnwindInsts.push_back(TI); 563 } 564 565 if (UnwindInsts.empty()) return false; 566 567 // Find the rewind function if we didn't already. 568 if (!RewindFunction) { 569 LLVMContext &Ctx = UnwindInsts[0]->getContext(); 570 std::vector<const Type*> 571 Params(1, Type::getInt8PtrTy(Ctx)); 572 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 573 Params, false); 574 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 575 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 576 } 577 578 bool Changed = false; 579 580 for (SmallVectorImpl<TerminatorInst*>::iterator 581 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { 582 TerminatorInst *TI = *I; 583 584 // Replace the unwind instruction with a call to _Unwind_Resume (or the 585 // appropriate target equivalent) followed by an UnreachableInst. 586 587 // Create the call... 588 CallInst *CI = CallInst::Create(RewindFunction, 589 CreateReadOfExceptionValue(TI->getParent()), 590 "", TI); 591 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 592 // ...followed by an UnreachableInst. 593 new UnreachableInst(TI->getContext(), TI); 594 595 // Nuke the unwind instruction. 596 TI->eraseFromParent(); 597 ++NumUnwindsLowered; 598 Changed = true; 599 } 600 601 return Changed; 602} 603 604/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 605/// landing pads by replacing calls outside of landing pads with loads from a 606/// stack temporary. Move eh.exception calls inside landing pads to the start 607/// of the landing pad (optional, but may make things simpler for later passes). 608bool DwarfEHPrepare::MoveExceptionValueCalls() { 609 // If the eh.exception intrinsic is not declared in the module then there is 610 // nothing to do. Speed up compilation by checking for this common case. 611 if (!ExceptionValueIntrinsic && 612 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 613 return false; 614 615 bool Changed = false; 616 617 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { 618 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) 619 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) 620 if (CI->getIntrinsicID() == Intrinsic::eh_exception) { 621 if (!CI->use_empty()) { 622 Value *ExceptionValue = CreateReadOfExceptionValue(BB); 623 if (CI == ExceptionValue) { 624 // The call was at the start of a landing pad - leave it alone. 625 assert(LandingPads.count(BB) && 626 "Created eh.exception call outside landing pad!"); 627 continue; 628 } 629 CI->replaceAllUsesWith(ExceptionValue); 630 } 631 CI->eraseFromParent(); 632 ++NumExceptionValuesMoved; 633 Changed = true; 634 } 635 } 636 637 return Changed; 638} 639 640/// FinishStackTemporaries - If we introduced a stack variable to hold the 641/// exception value then initialize it in each landing pad. 642bool DwarfEHPrepare::FinishStackTemporaries() { 643 if (!ExceptionValueVar) 644 // Nothing to do. 645 return false; 646 647 bool Changed = false; 648 649 // Make sure that there is a store of the exception value at the start of 650 // each landing pad. 651 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 652 LI != LE; ++LI) { 653 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI); 654 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar); 655 Store->insertAfter(ExceptionValue); 656 Changed = true; 657 } 658 659 return Changed; 660} 661 662/// PromoteStackTemporaries - Turn any stack temporaries we introduced into 663/// registers if possible. 664bool DwarfEHPrepare::PromoteStackTemporaries() { 665 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) { 666 // Turn the exception temporary into registers and phi nodes if possible. 667 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar); 668 PromoteMemToReg(Allocas, *DT, *DF); 669 return true; 670 } 671 return false; 672} 673 674/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 675/// the start of the basic block (unless there already is one, in which case 676/// the existing call is returned). 677Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 678 Instruction *Start = BB->getFirstNonPHIOrDbg(); 679 // Is this a call to eh.exception? 680 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 681 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 682 // Reuse the existing call. 683 return Start; 684 685 // Find the eh.exception intrinsic if we didn't already. 686 if (!ExceptionValueIntrinsic) 687 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 688 Intrinsic::eh_exception); 689 690 // Create the call. 691 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 692} 693 694/// CreateValueLoad - Insert a load of the exception value stack variable 695/// (creating it if necessary) at the start of the basic block (unless 696/// there already is a load, in which case the existing load is returned). 697Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) { 698 Instruction *Start = BB->getFirstNonPHIOrDbg(); 699 // Is this a load of the exception temporary? 700 if (ExceptionValueVar) 701 if (LoadInst* LI = dyn_cast<LoadInst>(Start)) 702 if (LI->getPointerOperand() == ExceptionValueVar) 703 // Reuse the existing load. 704 return Start; 705 706 // Create the temporary if we didn't already. 707 if (!ExceptionValueVar) { 708 ExceptionValueVar = new AllocaInst(PointerType::getUnqual( 709 Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin()); 710 ++NumStackTempsIntroduced; 711 } 712 713 // Load the value. 714 return new LoadInst(ExceptionValueVar, "eh.value.load", Start); 715} 716 717bool DwarfEHPrepare::runOnFunction(Function &Fn) { 718 bool Changed = false; 719 720 // Initialize internal state. 721 DT = getAnalysisIfAvailable<DominatorTree>(); 722 DF = getAnalysisIfAvailable<DominanceFrontier>(); 723 ExceptionValueVar = 0; 724 F = &Fn; 725 726 // Ensure that only unwind edges end at landing pads (a landing pad is a 727 // basic block where an invoke unwind edge ends). 728 Changed |= NormalizeLandingPads(); 729 730 // Turn unwind instructions into libcalls. 731 Changed |= LowerUnwinds(); 732 733 // TODO: Move eh.selector calls to landing pads and combine them. 734 735 // Move eh.exception calls to landing pads. 736 Changed |= MoveExceptionValueCalls(); 737 738 // Initialize any stack temporaries we introduced. 739 Changed |= FinishStackTemporaries(); 740 741 // Turn any stack temporaries into registers if possible. 742 if (!CompileFast) 743 Changed |= PromoteStackTemporaries(); 744 745 Changed |= HandleURoRInvokes(); 746 747 LandingPads.clear(); 748 749 return Changed; 750} 751