DwarfEHPrepare.cpp revision d8b4fb4aab4d6fedb2b14bed1b846451b17bde7c
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/SSAUpdater.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"); 34 35namespace { 36 class DwarfEHPrepare : public FunctionPass { 37 const TargetMachine *TM; 38 const TargetLowering *TLI; 39 40 // The eh.exception intrinsic. 41 Function *ExceptionValueIntrinsic; 42 43 // The eh.selector intrinsic. 44 Function *SelectorIntrinsic; 45 46 // _Unwind_Resume_or_Rethrow or _Unwind_SjLj_Resume call. 47 Constant *URoR; 48 49 // The EH language-specific catch-all type. 50 GlobalVariable *EHCatchAllValue; 51 52 // _Unwind_Resume or the target equivalent. 53 Constant *RewindFunction; 54 55 // We both use and preserve dominator info. 56 DominatorTree *DT; 57 58 // The function we are running on. 59 Function *F; 60 61 // The landing pads for this function. 62 typedef SmallPtrSet<BasicBlock*, 8> BBSet; 63 BBSet LandingPads; 64 65 bool NormalizeLandingPads(); 66 bool LowerUnwinds(); 67 bool MoveExceptionValueCalls(); 68 69 Instruction *CreateExceptionValueCall(BasicBlock *BB); 70 71 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still 72 /// use the "llvm.eh.catch.all.value" call need to convert to using its 73 /// initializer instead. 74 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); 75 76 bool HasCatchAllInSelector(IntrinsicInst *); 77 78 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 79 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 80 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels); 81 82 /// FindAllURoRInvokes - Find all URoR invokes in the function. 83 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); 84 85 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 86 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to 87 /// a landing pad within the current function. This is a candidate to merge 88 /// the selector associated with the URoR invoke with the one from the 89 /// URoR's landing pad. 90 bool HandleURoRInvokes(); 91 92 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated 93 /// with the eh.exception call. This recursively looks past instructions 94 /// which don't change the EH pointer value, like casts or PHI nodes. 95 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 96 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 97 SmallPtrSet<PHINode*, 32> &SeenPHIs); 98 99 public: 100 static char ID; // Pass identification, replacement for typeid. 101 DwarfEHPrepare(const TargetMachine *tm) : 102 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), 103 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 104 URoR(0), EHCatchAllValue(0), RewindFunction(0) { 105 initializeDominatorTreePass(*PassRegistry::getPassRegistry()); 106 } 107 108 virtual bool runOnFunction(Function &Fn); 109 110 // getAnalysisUsage - We need the dominator tree for handling URoR. 111 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 112 AU.addRequired<DominatorTree>(); 113 AU.addPreserved<DominatorTree>(); 114 } 115 116 const char *getPassName() const { 117 return "Exception handling preparation"; 118 } 119 120 }; 121} // end anonymous namespace 122 123char DwarfEHPrepare::ID = 0; 124 125FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { 126 return new DwarfEHPrepare(tm); 127} 128 129/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 130/// catch-all. 131bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 132 if (!EHCatchAllValue) return false; 133 134 unsigned ArgIdx = II->getNumArgOperands() - 1; 135 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 136 return GV == EHCatchAllValue; 137} 138 139/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 140void DwarfEHPrepare:: 141FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 142 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 143 for (Value::use_iterator 144 I = SelectorIntrinsic->use_begin(), 145 E = SelectorIntrinsic->use_end(); I != E; ++I) { 146 IntrinsicInst *II = cast<IntrinsicInst>(*I); 147 148 if (II->getParent()->getParent() != F) 149 continue; 150 151 if (!HasCatchAllInSelector(II)) 152 Sels.insert(II); 153 else 154 CatchAllSels.insert(II); 155 } 156} 157 158/// FindAllURoRInvokes - Find all URoR invokes in the function. 159void DwarfEHPrepare:: 160FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 161 for (Value::use_iterator 162 I = URoR->use_begin(), 163 E = URoR->use_end(); I != E; ++I) { 164 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 165 URoRInvokes.insert(II); 166 } 167} 168 169/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 170/// the "llvm.eh.catch.all.value" call need to convert to using its 171/// initializer instead. 172bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 173 if (!EHCatchAllValue) return false; 174 175 if (!SelectorIntrinsic) { 176 SelectorIntrinsic = 177 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 178 if (!SelectorIntrinsic) return false; 179 } 180 181 bool Changed = false; 182 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 183 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 184 IntrinsicInst *Sel = *I; 185 186 // Index of the "llvm.eh.catch.all.value" variable. 187 unsigned OpIdx = Sel->getNumArgOperands() - 1; 188 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 189 if (GV != EHCatchAllValue) continue; 190 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 191 Changed = true; 192 } 193 194 return Changed; 195} 196 197/// FindSelectorAndURoR - Find the eh.selector call associated with the 198/// eh.exception call. And indicate if there is a URoR "invoke" associated with 199/// the eh.exception call. This recursively looks past instructions which don't 200/// change the EH pointer value, like casts or PHI nodes. 201bool 202DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 203 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 204 SmallPtrSet<PHINode*, 32> &SeenPHIs) { 205 bool Changed = false; 206 207 for (Value::use_iterator 208 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 209 Instruction *II = dyn_cast<Instruction>(*I); 210 if (!II || II->getParent()->getParent() != F) continue; 211 212 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 213 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 214 SelCalls.insert(Sel); 215 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 216 if (Invoke->getCalledFunction() == URoR) 217 URoRInvoke = true; 218 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 219 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls, SeenPHIs); 220 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 221 if (SeenPHIs.insert(PN)) 222 // Don't process a PHI node more than once. 223 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls, SeenPHIs); 224 } 225 } 226 227 return Changed; 228} 229 230/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 231/// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to a 232/// landing pad within the current function. This is a candidate to merge the 233/// selector associated with the URoR invoke with the one from the URoR's 234/// landing pad. 235bool DwarfEHPrepare::HandleURoRInvokes() { 236 if (!EHCatchAllValue) { 237 EHCatchAllValue = 238 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 239 if (!EHCatchAllValue) return false; 240 } 241 242 if (!SelectorIntrinsic) { 243 SelectorIntrinsic = 244 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 245 if (!SelectorIntrinsic) return false; 246 } 247 248 SmallPtrSet<IntrinsicInst*, 32> Sels; 249 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 250 FindAllCleanupSelectors(Sels, CatchAllSels); 251 252 if (!URoR) { 253 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 254 if (!URoR) { 255 URoR = F->getParent()->getFunction("_Unwind_SjLj_Resume"); 256 if (!URoR) return CleanupSelectors(CatchAllSels); 257 } 258 } 259 260 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 261 FindAllURoRInvokes(URoRInvokes); 262 263 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; 264 265 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 266 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { 267 const BasicBlock *SelBB = (*SI)->getParent(); 268 for (SmallPtrSet<InvokeInst*, 32>::iterator 269 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { 270 const BasicBlock *URoRBB = (*UI)->getParent(); 271 if (DT->dominates(SelBB, URoRBB)) { 272 SelsToConvert.insert(*SI); 273 break; 274 } 275 } 276 } 277 278 bool Changed = false; 279 280 if (Sels.size() != SelsToConvert.size()) { 281 // If we haven't been able to convert all of the clean-up selectors, then 282 // loop through the slow way to see if they still need to be converted. 283 if (!ExceptionValueIntrinsic) { 284 ExceptionValueIntrinsic = 285 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); 286 if (!ExceptionValueIntrinsic) 287 return CleanupSelectors(CatchAllSels); 288 } 289 290 for (Value::use_iterator 291 I = ExceptionValueIntrinsic->use_begin(), 292 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 293 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); 294 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 295 296 bool URoRInvoke = false; 297 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 298 SmallPtrSet<PHINode*, 32> SeenPHIs; 299 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls, SeenPHIs); 300 301 if (URoRInvoke) { 302 // This EH pointer is being used by an invoke of an URoR instruction and 303 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 304 // need to convert it to a 'catch-all'. 305 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 306 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 307 if (!HasCatchAllInSelector(*SI)) 308 SelsToConvert.insert(*SI); 309 } 310 } 311 } 312 313 if (!SelsToConvert.empty()) { 314 // Convert all clean-up eh.selectors, which are associated with "invokes" of 315 // URoR calls, into catch-all eh.selectors. 316 Changed = true; 317 318 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 319 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 320 SI != SE; ++SI) { 321 IntrinsicInst *II = *SI; 322 323 // Use the exception object pointer and the personality function 324 // from the original selector. 325 CallSite CS(II); 326 IntrinsicInst::op_iterator I = CS.arg_begin(); 327 IntrinsicInst::op_iterator E = CS.arg_end(); 328 IntrinsicInst::op_iterator B = prior(E); 329 330 // Exclude last argument if it is an integer. 331 if (isa<ConstantInt>(B)) E = B; 332 333 // Add exception object pointer (front). 334 // Add personality function (next). 335 // Add in any filter IDs (rest). 336 SmallVector<Value*, 8> Args(I, E); 337 338 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 339 340 CallInst *NewSelector = 341 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 342 "eh.sel.catch.all", II); 343 344 NewSelector->setTailCall(II->isTailCall()); 345 NewSelector->setAttributes(II->getAttributes()); 346 NewSelector->setCallingConv(II->getCallingConv()); 347 348 II->replaceAllUsesWith(NewSelector); 349 II->eraseFromParent(); 350 } 351 } 352 353 Changed |= CleanupSelectors(CatchAllSels); 354 return Changed; 355} 356 357/// NormalizeLandingPads - Normalize and discover landing pads, noting them 358/// in the LandingPads set. A landing pad is normal if the only CFG edges 359/// that end at it are unwind edges from invoke instructions. If we inlined 360/// through an invoke we could have a normal branch from the previous 361/// unwind block through to the landing pad for the original invoke. 362/// Abnormal landing pads are fixed up by redirecting all unwind edges to 363/// a new basic block which falls through to the original. 364bool DwarfEHPrepare::NormalizeLandingPads() { 365 bool Changed = false; 366 367 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 368 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 369 370 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 371 TerminatorInst *TI = I->getTerminator(); 372 if (!isa<InvokeInst>(TI)) 373 continue; 374 BasicBlock *LPad = TI->getSuccessor(1); 375 // Skip landing pads that have already been normalized. 376 if (LandingPads.count(LPad)) 377 continue; 378 379 // Check that only invoke unwind edges end at the landing pad. 380 bool OnlyUnwoundTo = true; 381 bool SwitchOK = usingSjLjEH; 382 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 383 PI != PE; ++PI) { 384 TerminatorInst *PT = (*PI)->getTerminator(); 385 // The SjLj dispatch block uses a switch instruction. This is effectively 386 // an unwind edge, so we can disregard it here. There will only ever 387 // be one dispatch, however, so if there are multiple switches, one 388 // of them truly is a normal edge, not an unwind edge. 389 if (SwitchOK && isa<SwitchInst>(PT)) { 390 SwitchOK = false; 391 continue; 392 } 393 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 394 OnlyUnwoundTo = false; 395 break; 396 } 397 } 398 399 if (OnlyUnwoundTo) { 400 // Only unwind edges lead to the landing pad. Remember the landing pad. 401 LandingPads.insert(LPad); 402 continue; 403 } 404 405 // At least one normal edge ends at the landing pad. Redirect the unwind 406 // edges to a new basic block which falls through into this one. 407 408 // Create the new basic block. 409 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 410 LPad->getName() + "_unwind_edge"); 411 412 // Insert it into the function right before the original landing pad. 413 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 414 415 // Redirect unwind edges from the original landing pad to NewBB. 416 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 417 TerminatorInst *PT = (*PI++)->getTerminator(); 418 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 419 // Unwind to the new block. 420 PT->setSuccessor(1, NewBB); 421 } 422 423 // If there are any PHI nodes in LPad, we need to update them so that they 424 // merge incoming values from NewBB instead. 425 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 426 PHINode *PN = cast<PHINode>(II); 427 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 428 429 // Check to see if all of the values coming in via unwind edges are the 430 // same. If so, we don't need to create a new PHI node. 431 Value *InVal = PN->getIncomingValueForBlock(*PB); 432 for (pred_iterator PI = PB; PI != PE; ++PI) { 433 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 434 InVal = 0; 435 break; 436 } 437 } 438 439 if (InVal == 0) { 440 // Different unwind edges have different values. Create a new PHI node 441 // in NewBB. 442 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", 443 NewBB); 444 NewPN->reserveOperandSpace(PN->getNumIncomingValues()); 445 // Add an entry for each unwind edge, using the value from the old PHI. 446 for (pred_iterator PI = PB; PI != PE; ++PI) 447 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 448 449 // Now use this new PHI as the common incoming value for NewBB in PN. 450 InVal = NewPN; 451 } 452 453 // Revector exactly one entry in the PHI node to come from NewBB 454 // and delete all other entries that come from unwind edges. If 455 // there are both normal and unwind edges from the same predecessor, 456 // this leaves an entry for the normal edge. 457 for (pred_iterator PI = PB; PI != PE; ++PI) 458 PN->removeIncomingValue(*PI); 459 PN->addIncoming(InVal, NewBB); 460 } 461 462 // Add a fallthrough from NewBB to the original landing pad. 463 BranchInst::Create(LPad, NewBB); 464 465 // Now update DominatorTree analysis information. 466 DT->splitBlock(NewBB); 467 468 // Remember the newly constructed landing pad. The original landing pad 469 // LPad is no longer a landing pad now that all unwind edges have been 470 // revectored to NewBB. 471 LandingPads.insert(NewBB); 472 ++NumLandingPadsSplit; 473 Changed = true; 474 } 475 476 return Changed; 477} 478 479/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 480/// rethrowing any previously caught exception. This will crash horribly 481/// at runtime if there is no such exception: using unwind to throw a new 482/// exception is currently not supported. 483bool DwarfEHPrepare::LowerUnwinds() { 484 SmallVector<TerminatorInst*, 16> UnwindInsts; 485 486 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 487 TerminatorInst *TI = I->getTerminator(); 488 if (isa<UnwindInst>(TI)) 489 UnwindInsts.push_back(TI); 490 } 491 492 if (UnwindInsts.empty()) return false; 493 494 // Find the rewind function if we didn't already. 495 if (!RewindFunction) { 496 LLVMContext &Ctx = UnwindInsts[0]->getContext(); 497 std::vector<const Type*> 498 Params(1, Type::getInt8PtrTy(Ctx)); 499 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 500 Params, false); 501 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 502 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 503 } 504 505 bool Changed = false; 506 507 for (SmallVectorImpl<TerminatorInst*>::iterator 508 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { 509 TerminatorInst *TI = *I; 510 511 // Replace the unwind instruction with a call to _Unwind_Resume (or the 512 // appropriate target equivalent) followed by an UnreachableInst. 513 514 // Create the call... 515 CallInst *CI = CallInst::Create(RewindFunction, 516 CreateExceptionValueCall(TI->getParent()), 517 "", TI); 518 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 519 // ...followed by an UnreachableInst. 520 new UnreachableInst(TI->getContext(), TI); 521 522 // Nuke the unwind instruction. 523 TI->eraseFromParent(); 524 ++NumUnwindsLowered; 525 Changed = true; 526 } 527 528 return Changed; 529} 530 531/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 532/// landing pads by replacing calls outside of landing pads with direct use of 533/// a register holding the appropriate value; this requires adding calls inside 534/// all landing pads to initialize the register. Also, move eh.exception calls 535/// inside landing pads to the start of the landing pad (optional, but may make 536/// things simpler for later passes). 537bool DwarfEHPrepare::MoveExceptionValueCalls() { 538 // If the eh.exception intrinsic is not declared in the module then there is 539 // nothing to do. Speed up compilation by checking for this common case. 540 if (!ExceptionValueIntrinsic && 541 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 542 return false; 543 544 bool Changed = false; 545 546 // Move calls to eh.exception that are inside a landing pad to the start of 547 // the landing pad. 548 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end(); 549 LI != LE; ++LI) { 550 BasicBlock *LP = *LI; 551 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end(); 552 II != IE;) 553 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 554 // Found a call to eh.exception. 555 if (!EI->use_empty()) { 556 // If there is already a call to eh.exception at the start of the 557 // landing pad, then get hold of it; otherwise create such a call. 558 Value *CallAtStart = CreateExceptionValueCall(LP); 559 560 // If the call was at the start of a landing pad then leave it alone. 561 if (EI == CallAtStart) 562 continue; 563 EI->replaceAllUsesWith(CallAtStart); 564 } 565 EI->eraseFromParent(); 566 ++NumExceptionValuesMoved; 567 Changed = true; 568 } 569 } 570 571 // Look for calls to eh.exception that are not in a landing pad. If one is 572 // found, then a register that holds the exception value will be created in 573 // each landing pad, and the SSAUpdater will be used to compute the values 574 // returned by eh.exception calls outside of landing pads. 575 SSAUpdater SSA; 576 577 // Remember where we found the eh.exception call, to avoid rescanning earlier 578 // basic blocks which we already know contain no eh.exception calls. 579 bool FoundCallOutsideLandingPad = false; 580 Function::iterator BB = F->begin(); 581 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 582 // Skip over landing pads. 583 if (LandingPads.count(BB)) 584 continue; 585 586 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 587 II != IE; ++II) 588 if (isa<EHExceptionInst>(II)) { 589 SSA.Initialize(II->getType(), II->getName()); 590 FoundCallOutsideLandingPad = true; 591 break; 592 } 593 594 if (FoundCallOutsideLandingPad) 595 break; 596 } 597 598 // If all calls to eh.exception are in landing pads then we are done. 599 if (!FoundCallOutsideLandingPad) 600 return Changed; 601 602 // Add a call to eh.exception at the start of each landing pad, and tell the 603 // SSAUpdater that this is the value produced by the landing pad. 604 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 605 LI != LE; ++LI) 606 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI)); 607 608 // Now turn all calls to eh.exception that are not in a landing pad into a use 609 // of the appropriate register. 610 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 611 // Skip over landing pads. 612 if (LandingPads.count(BB)) 613 continue; 614 615 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 616 II != IE;) 617 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 618 // Found a call to eh.exception, replace it with the value from any 619 // upstream landing pad(s). 620 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB)); 621 EI->eraseFromParent(); 622 ++NumExceptionValuesMoved; 623 } 624 } 625 626 return true; 627} 628 629/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 630/// the start of the basic block (unless there already is one, in which case 631/// the existing call is returned). 632Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 633 Instruction *Start = BB->getFirstNonPHIOrDbg(); 634 // Is this a call to eh.exception? 635 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 636 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 637 // Reuse the existing call. 638 return Start; 639 640 // Find the eh.exception intrinsic if we didn't already. 641 if (!ExceptionValueIntrinsic) 642 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 643 Intrinsic::eh_exception); 644 645 // Create the call. 646 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 647} 648 649bool DwarfEHPrepare::runOnFunction(Function &Fn) { 650 bool Changed = false; 651 652 // Initialize internal state. 653 DT = &getAnalysis<DominatorTree>(); 654 F = &Fn; 655 656 // Ensure that only unwind edges end at landing pads (a landing pad is a 657 // basic block where an invoke unwind edge ends). 658 Changed |= NormalizeLandingPads(); 659 660 // Turn unwind instructions into libcalls. 661 Changed |= LowerUnwinds(); 662 663 // TODO: Move eh.selector calls to landing pads and combine them. 664 665 // Move eh.exception calls to landing pads. 666 Changed |= MoveExceptionValueCalls(); 667 668 Changed |= HandleURoRInvokes(); 669 670 LandingPads.clear(); 671 672 return Changed; 673} 674