DwarfEHPrepare.cpp revision c34c2200a8077f98cf5cac9fe6f8a6d69b89b54c
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 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst. 116 bool PromoteStoreInst(StoreInst *SI) { 117 if (!SI || !DT || !DF) return false; 118 119 AllocaInst *AI = dyn_cast<AllocaInst>(SI->getOperand(1)); 120 if (!AI || !isAllocaPromotable(AI)) return false; 121 122 // Turn the alloca into a register. 123 std::vector<AllocaInst*> Allocas(1, AI); 124 PromoteMemToReg(Allocas, *DT, *DF); 125 return true; 126 } 127 128 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a 129 /// register. This should get rid of the store and subsequent loads. 130 bool PromoteEHPtrStore(IntrinsicInst *II) { 131 if (!DT || !DF) return false; 132 133 bool Changed = false; 134 StoreInst *SI; 135 136 while (1) { 137 SI = 0; 138 for (Value::use_iterator 139 I = II->use_begin(), E = II->use_end(); I != E; ++I) { 140 SI = dyn_cast<StoreInst>(*I); 141 if (SI) break; 142 } 143 144 if (!PromoteStoreInst(SI)) 145 break; 146 147 Changed = true; 148 } 149 150 return Changed; 151 } 152 153 public: 154 static char ID; // Pass identification, replacement for typeid. 155 DwarfEHPrepare(const TargetMachine *tm, bool fast) : 156 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), 157 CompileFast(fast), 158 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 159 URoR(0), EHCatchAllValue(0), RewindFunction(0) {} 160 161 virtual bool runOnFunction(Function &Fn); 162 163 // getAnalysisUsage - We need dominance frontiers for memory promotion. 164 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 165 if (!CompileFast) 166 AU.addRequired<DominatorTree>(); 167 AU.addPreserved<DominatorTree>(); 168 if (!CompileFast) 169 AU.addRequired<DominanceFrontier>(); 170 AU.addPreserved<DominanceFrontier>(); 171 } 172 173 const char *getPassName() const { 174 return "Exception handling preparation"; 175 } 176 177 }; 178} // end anonymous namespace 179 180char DwarfEHPrepare::ID = 0; 181 182FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm, bool fast) { 183 return new DwarfEHPrepare(tm, fast); 184} 185 186/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 187/// catch-all. 188bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 189 if (!EHCatchAllValue) return false; 190 191 unsigned ArgIdx = II->getNumArgOperands() - 1; 192 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 193 return GV == EHCatchAllValue; 194} 195 196/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 197void DwarfEHPrepare:: 198FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 199 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 200 for (Value::use_iterator 201 I = SelectorIntrinsic->use_begin(), 202 E = SelectorIntrinsic->use_end(); I != E; ++I) { 203 IntrinsicInst *II = cast<IntrinsicInst>(*I); 204 205 if (II->getParent()->getParent() != F) 206 continue; 207 208 if (!HasCatchAllInSelector(II)) 209 Sels.insert(II); 210 else 211 CatchAllSels.insert(II); 212 } 213} 214 215/// FindAllURoRInvokes - Find all URoR invokes in the function. 216void DwarfEHPrepare:: 217FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 218 for (Value::use_iterator 219 I = URoR->use_begin(), 220 E = URoR->use_end(); I != E; ++I) { 221 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 222 URoRInvokes.insert(II); 223 } 224} 225 226/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 227/// the "llvm.eh.catch.all.value" call need to convert to using its 228/// initializer instead. 229bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 230 if (!EHCatchAllValue) return false; 231 232 if (!SelectorIntrinsic) { 233 SelectorIntrinsic = 234 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 235 if (!SelectorIntrinsic) return false; 236 } 237 238 bool Changed = false; 239 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 240 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 241 IntrinsicInst *Sel = *I; 242 243 // Index of the "llvm.eh.catch.all.value" variable. 244 unsigned OpIdx = Sel->getNumArgOperands() - 1; 245 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 246 if (GV != EHCatchAllValue) continue; 247 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 248 Changed = true; 249 } 250 251 return Changed; 252} 253 254/// FindSelectorAndURoR - Find the eh.selector call associated with the 255/// eh.exception call. And indicate if there is a URoR "invoke" associated with 256/// the eh.exception call. This recursively looks past instructions which don't 257/// change the EH pointer value, like casts or PHI nodes. 258bool 259DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 260 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) { 261 SmallPtrSet<PHINode*, 32> SeenPHIs; 262 bool Changed = false; 263 264 restart: 265 for (Value::use_iterator 266 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 267 Instruction *II = dyn_cast<Instruction>(*I); 268 if (!II || II->getParent()->getParent() != F) continue; 269 270 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 271 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 272 SelCalls.insert(Sel); 273 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 274 if (Invoke->getCalledFunction() == URoR) 275 URoRInvoke = true; 276 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 277 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls); 278 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) { 279 if (!PromoteStoreInst(SI)) continue; 280 Changed = true; 281 SeenPHIs.clear(); 282 goto restart; // Uses may have changed, restart loop. 283 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 284 if (SeenPHIs.insert(PN)) 285 // Don't process a PHI node more than once. 286 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls); 287 } 288 } 289 290 return Changed; 291} 292 293/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The 294/// "unwind" part of these invokes jump to a landing pad within the current 295/// function. This is a candidate to merge the selector associated with the URoR 296/// invoke with the one from the URoR's landing pad. 297bool DwarfEHPrepare::HandleURoRInvokes() { 298 if (!EHCatchAllValue) { 299 EHCatchAllValue = 300 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 301 if (!EHCatchAllValue) return false; 302 } 303 304 if (!SelectorIntrinsic) { 305 SelectorIntrinsic = 306 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 307 if (!SelectorIntrinsic) return false; 308 } 309 310 SmallPtrSet<IntrinsicInst*, 32> Sels; 311 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 312 FindAllCleanupSelectors(Sels, CatchAllSels); 313 314 if (!DT) 315 // We require DominatorTree information. 316 return CleanupSelectors(CatchAllSels); 317 318 if (!URoR) { 319 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 320 if (!URoR) return CleanupSelectors(CatchAllSels); 321 } 322 323 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 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 (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) 350 return CleanupSelectors(CatchAllSels); 351 } 352 353 for (Value::use_iterator 354 I = ExceptionValueIntrinsic->use_begin(), 355 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 356 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); 357 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 358 359 Changed |= PromoteEHPtrStore(EHPtr); 360 361 bool URoRInvoke = false; 362 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 363 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls); 364 365 if (URoRInvoke) { 366 // This EH pointer is being used by an invoke of an URoR instruction and 367 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 368 // need to convert it to a 'catch-all'. 369 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 370 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 371 if (!HasCatchAllInSelector(*SI)) 372 SelsToConvert.insert(*SI); 373 } 374 } 375 } 376 377 if (!SelsToConvert.empty()) { 378 // Convert all clean-up eh.selectors, which are associated with "invokes" of 379 // URoR calls, into catch-all eh.selectors. 380 Changed = true; 381 382 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 383 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 384 SI != SE; ++SI) { 385 IntrinsicInst *II = *SI; 386 387 // Use the exception object pointer and the personality function 388 // from the original selector. 389 CallSite CS(II); 390 IntrinsicInst::op_iterator I = CS.arg_begin(); 391 IntrinsicInst::op_iterator E = CS.arg_end(); 392 IntrinsicInst::op_iterator B = prior(E); 393 394 // Exclude last argument if it is an integer. 395 if (isa<ConstantInt>(B)) E = B; 396 397 // Add exception object pointer (front). 398 // Add personality function (next). 399 // Add in any filter IDs (rest). 400 SmallVector<Value*, 8> Args(I, E); 401 402 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 403 404 CallInst *NewSelector = 405 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 406 "eh.sel.catch.all", II); 407 408 NewSelector->setTailCall(II->isTailCall()); 409 NewSelector->setAttributes(II->getAttributes()); 410 NewSelector->setCallingConv(II->getCallingConv()); 411 412 II->replaceAllUsesWith(NewSelector); 413 II->eraseFromParent(); 414 } 415 } 416 417 Changed |= CleanupSelectors(CatchAllSels); 418 return Changed; 419} 420 421/// NormalizeLandingPads - Normalize and discover landing pads, noting them 422/// in the LandingPads set. A landing pad is normal if the only CFG edges 423/// that end at it are unwind edges from invoke instructions. If we inlined 424/// through an invoke we could have a normal branch from the previous 425/// unwind block through to the landing pad for the original invoke. 426/// Abnormal landing pads are fixed up by redirecting all unwind edges to 427/// a new basic block which falls through to the original. 428bool DwarfEHPrepare::NormalizeLandingPads() { 429 bool Changed = false; 430 431 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 432 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 433 434 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 435 TerminatorInst *TI = I->getTerminator(); 436 if (!isa<InvokeInst>(TI)) 437 continue; 438 BasicBlock *LPad = TI->getSuccessor(1); 439 // Skip landing pads that have already been normalized. 440 if (LandingPads.count(LPad)) 441 continue; 442 443 // Check that only invoke unwind edges end at the landing pad. 444 bool OnlyUnwoundTo = true; 445 bool SwitchOK = usingSjLjEH; 446 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 447 PI != PE; ++PI) { 448 TerminatorInst *PT = (*PI)->getTerminator(); 449 // The SjLj dispatch block uses a switch instruction. This is effectively 450 // an unwind edge, so we can disregard it here. There will only ever 451 // be one dispatch, however, so if there are multiple switches, one 452 // of them truly is a normal edge, not an unwind edge. 453 if (SwitchOK && isa<SwitchInst>(PT)) { 454 SwitchOK = false; 455 continue; 456 } 457 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 458 OnlyUnwoundTo = false; 459 break; 460 } 461 } 462 463 if (OnlyUnwoundTo) { 464 // Only unwind edges lead to the landing pad. Remember the landing pad. 465 LandingPads.insert(LPad); 466 continue; 467 } 468 469 // At least one normal edge ends at the landing pad. Redirect the unwind 470 // edges to a new basic block which falls through into this one. 471 472 // Create the new basic block. 473 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 474 LPad->getName() + "_unwind_edge"); 475 476 // Insert it into the function right before the original landing pad. 477 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 478 479 // Redirect unwind edges from the original landing pad to NewBB. 480 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 481 TerminatorInst *PT = (*PI++)->getTerminator(); 482 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 483 // Unwind to the new block. 484 PT->setSuccessor(1, NewBB); 485 } 486 487 // If there are any PHI nodes in LPad, we need to update them so that they 488 // merge incoming values from NewBB instead. 489 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 490 PHINode *PN = cast<PHINode>(II); 491 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 492 493 // Check to see if all of the values coming in via unwind edges are the 494 // same. If so, we don't need to create a new PHI node. 495 Value *InVal = PN->getIncomingValueForBlock(*PB); 496 for (pred_iterator PI = PB; PI != PE; ++PI) { 497 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 498 InVal = 0; 499 break; 500 } 501 } 502 503 if (InVal == 0) { 504 // Different unwind edges have different values. Create a new PHI node 505 // in NewBB. 506 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", 507 NewBB); 508 // Add an entry for each unwind edge, using the value from the old PHI. 509 for (pred_iterator PI = PB; PI != PE; ++PI) 510 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 511 512 // Now use this new PHI as the common incoming value for NewBB in PN. 513 InVal = NewPN; 514 } 515 516 // Revector exactly one entry in the PHI node to come from NewBB 517 // and delete all other entries that come from unwind edges. If 518 // there are both normal and unwind edges from the same predecessor, 519 // this leaves an entry for the normal edge. 520 for (pred_iterator PI = PB; PI != PE; ++PI) 521 PN->removeIncomingValue(*PI); 522 PN->addIncoming(InVal, NewBB); 523 } 524 525 // Add a fallthrough from NewBB to the original landing pad. 526 BranchInst::Create(LPad, NewBB); 527 528 // Now update DominatorTree and DominanceFrontier analysis information. 529 if (DT) 530 DT->splitBlock(NewBB); 531 if (DF) 532 DF->splitBlock(NewBB); 533 534 // Remember the newly constructed landing pad. The original landing pad 535 // LPad is no longer a landing pad now that all unwind edges have been 536 // revectored to NewBB. 537 LandingPads.insert(NewBB); 538 ++NumLandingPadsSplit; 539 Changed = true; 540 } 541 542 return Changed; 543} 544 545/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 546/// rethrowing any previously caught exception. This will crash horribly 547/// at runtime if there is no such exception: using unwind to throw a new 548/// exception is currently not supported. 549bool DwarfEHPrepare::LowerUnwinds() { 550 SmallVector<TerminatorInst*, 16> UnwindInsts; 551 552 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 553 TerminatorInst *TI = I->getTerminator(); 554 if (isa<UnwindInst>(TI)) 555 UnwindInsts.push_back(TI); 556 } 557 558 if (UnwindInsts.empty()) return false; 559 560 // Find the rewind function if we didn't already. 561 if (!RewindFunction) { 562 LLVMContext &Ctx = UnwindInsts[0]->getContext(); 563 std::vector<const Type*> 564 Params(1, Type::getInt8PtrTy(Ctx)); 565 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 566 Params, false); 567 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 568 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 569 } 570 571 bool Changed = false; 572 573 for (SmallVectorImpl<TerminatorInst*>::iterator 574 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { 575 TerminatorInst *TI = *I; 576 577 // Replace the unwind instruction with a call to _Unwind_Resume (or the 578 // appropriate target equivalent) followed by an UnreachableInst. 579 580 // Create the call... 581 CallInst *CI = CallInst::Create(RewindFunction, 582 CreateReadOfExceptionValue(TI->getParent()), 583 "", TI); 584 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 585 // ...followed by an UnreachableInst. 586 new UnreachableInst(TI->getContext(), TI); 587 588 // Nuke the unwind instruction. 589 TI->eraseFromParent(); 590 ++NumUnwindsLowered; 591 Changed = true; 592 } 593 594 return Changed; 595} 596 597/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 598/// landing pads by replacing calls outside of landing pads with loads from a 599/// stack temporary. Move eh.exception calls inside landing pads to the start 600/// of the landing pad (optional, but may make things simpler for later passes). 601bool DwarfEHPrepare::MoveExceptionValueCalls() { 602 // If the eh.exception intrinsic is not declared in the module then there is 603 // nothing to do. Speed up compilation by checking for this common case. 604 if (!ExceptionValueIntrinsic && 605 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 606 return false; 607 608 bool Changed = false; 609 610 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { 611 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) 612 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) 613 if (CI->getIntrinsicID() == Intrinsic::eh_exception) { 614 if (!CI->use_empty()) { 615 Value *ExceptionValue = CreateReadOfExceptionValue(BB); 616 if (CI == ExceptionValue) { 617 // The call was at the start of a landing pad - leave it alone. 618 assert(LandingPads.count(BB) && 619 "Created eh.exception call outside landing pad!"); 620 continue; 621 } 622 CI->replaceAllUsesWith(ExceptionValue); 623 } 624 CI->eraseFromParent(); 625 ++NumExceptionValuesMoved; 626 Changed = true; 627 } 628 } 629 630 return Changed; 631} 632 633/// FinishStackTemporaries - If we introduced a stack variable to hold the 634/// exception value then initialize it in each landing pad. 635bool DwarfEHPrepare::FinishStackTemporaries() { 636 if (!ExceptionValueVar) 637 // Nothing to do. 638 return false; 639 640 bool Changed = false; 641 642 // Make sure that there is a store of the exception value at the start of 643 // each landing pad. 644 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 645 LI != LE; ++LI) { 646 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI); 647 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar); 648 Store->insertAfter(ExceptionValue); 649 Changed = true; 650 } 651 652 return Changed; 653} 654 655/// PromoteStackTemporaries - Turn any stack temporaries we introduced into 656/// registers if possible. 657bool DwarfEHPrepare::PromoteStackTemporaries() { 658 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) { 659 // Turn the exception temporary into registers and phi nodes if possible. 660 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar); 661 PromoteMemToReg(Allocas, *DT, *DF); 662 return true; 663 } 664 return false; 665} 666 667/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 668/// the start of the basic block (unless there already is one, in which case 669/// the existing call is returned). 670Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 671 Instruction *Start = BB->getFirstNonPHIOrDbg(); 672 // Is this a call to eh.exception? 673 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 674 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 675 // Reuse the existing call. 676 return Start; 677 678 // Find the eh.exception intrinsic if we didn't already. 679 if (!ExceptionValueIntrinsic) 680 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 681 Intrinsic::eh_exception); 682 683 // Create the call. 684 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 685} 686 687/// CreateValueLoad - Insert a load of the exception value stack variable 688/// (creating it if necessary) at the start of the basic block (unless 689/// there already is a load, in which case the existing load is returned). 690Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) { 691 Instruction *Start = BB->getFirstNonPHIOrDbg(); 692 // Is this a load of the exception temporary? 693 if (ExceptionValueVar) 694 if (LoadInst* LI = dyn_cast<LoadInst>(Start)) 695 if (LI->getPointerOperand() == ExceptionValueVar) 696 // Reuse the existing load. 697 return Start; 698 699 // Create the temporary if we didn't already. 700 if (!ExceptionValueVar) { 701 ExceptionValueVar = new AllocaInst(PointerType::getUnqual( 702 Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin()); 703 ++NumStackTempsIntroduced; 704 } 705 706 // Load the value. 707 return new LoadInst(ExceptionValueVar, "eh.value.load", Start); 708} 709 710bool DwarfEHPrepare::runOnFunction(Function &Fn) { 711 bool Changed = false; 712 713 // Initialize internal state. 714 DT = getAnalysisIfAvailable<DominatorTree>(); 715 DF = getAnalysisIfAvailable<DominanceFrontier>(); 716 ExceptionValueVar = 0; 717 F = &Fn; 718 719 // Ensure that only unwind edges end at landing pads (a landing pad is a 720 // basic block where an invoke unwind edge ends). 721 Changed |= NormalizeLandingPads(); 722 723 // Turn unwind instructions into libcalls. 724 Changed |= LowerUnwinds(); 725 726 // TODO: Move eh.selector calls to landing pads and combine them. 727 728 // Move eh.exception calls to landing pads. 729 Changed |= MoveExceptionValueCalls(); 730 731 // Initialize any stack temporaries we introduced. 732 Changed |= FinishStackTemporaries(); 733 734 // Turn any stack temporaries into registers if possible. 735 if (!CompileFast) 736 Changed |= PromoteStackTemporaries(); 737 738 Changed |= HandleURoRInvokes(); 739 740 LandingPads.clear(); 741 742 return Changed; 743} 744