DwarfEHPrepare.cpp revision 212904
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 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" 86 /// calls. The "unwind" part of these invokes jump to a landing pad within 87 /// the current function. This is a candidate to merge the selector 88 /// associated with the URoR invoke with the one from the URoR's landing 89 /// 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 98 public: 99 static char ID; // Pass identification, replacement for typeid. 100 DwarfEHPrepare(const TargetMachine *tm) : 101 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), 102 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 103 URoR(0), EHCatchAllValue(0), RewindFunction(0) {} 104 105 virtual bool runOnFunction(Function &Fn); 106 107 // getAnalysisUsage - We need the dominator tree for handling URoR. 108 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 109 AU.addRequired<DominatorTree>(); 110 AU.addPreserved<DominatorTree>(); 111 } 112 113 const char *getPassName() const { 114 return "Exception handling preparation"; 115 } 116 117 }; 118} // end anonymous namespace 119 120char DwarfEHPrepare::ID = 0; 121 122FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { 123 return new DwarfEHPrepare(tm); 124} 125 126/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 127/// catch-all. 128bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 129 if (!EHCatchAllValue) return false; 130 131 unsigned ArgIdx = II->getNumArgOperands() - 1; 132 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 133 return GV == EHCatchAllValue; 134} 135 136/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 137void DwarfEHPrepare:: 138FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 139 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 140 for (Value::use_iterator 141 I = SelectorIntrinsic->use_begin(), 142 E = SelectorIntrinsic->use_end(); I != E; ++I) { 143 IntrinsicInst *II = cast<IntrinsicInst>(*I); 144 145 if (II->getParent()->getParent() != F) 146 continue; 147 148 if (!HasCatchAllInSelector(II)) 149 Sels.insert(II); 150 else 151 CatchAllSels.insert(II); 152 } 153} 154 155/// FindAllURoRInvokes - Find all URoR invokes in the function. 156void DwarfEHPrepare:: 157FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 158 for (Value::use_iterator 159 I = URoR->use_begin(), 160 E = URoR->use_end(); I != E; ++I) { 161 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 162 URoRInvokes.insert(II); 163 } 164} 165 166/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 167/// the "llvm.eh.catch.all.value" call need to convert to using its 168/// initializer instead. 169bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 170 if (!EHCatchAllValue) return false; 171 172 if (!SelectorIntrinsic) { 173 SelectorIntrinsic = 174 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 175 if (!SelectorIntrinsic) return false; 176 } 177 178 bool Changed = false; 179 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 180 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 181 IntrinsicInst *Sel = *I; 182 183 // Index of the "llvm.eh.catch.all.value" variable. 184 unsigned OpIdx = Sel->getNumArgOperands() - 1; 185 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 186 if (GV != EHCatchAllValue) continue; 187 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 188 Changed = true; 189 } 190 191 return Changed; 192} 193 194/// FindSelectorAndURoR - Find the eh.selector call associated with the 195/// eh.exception call. And indicate if there is a URoR "invoke" associated with 196/// the eh.exception call. This recursively looks past instructions which don't 197/// change the EH pointer value, like casts or PHI nodes. 198bool 199DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 200 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) { 201 SmallPtrSet<PHINode*, 32> SeenPHIs; 202 bool Changed = false; 203 204 for (Value::use_iterator 205 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 206 Instruction *II = dyn_cast<Instruction>(*I); 207 if (!II || II->getParent()->getParent() != F) continue; 208 209 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 210 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 211 SelCalls.insert(Sel); 212 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 213 if (Invoke->getCalledFunction() == URoR) 214 URoRInvoke = true; 215 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 216 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls); 217 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 218 if (SeenPHIs.insert(PN)) 219 // Don't process a PHI node more than once. 220 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls); 221 } 222 } 223 224 return Changed; 225} 226 227/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The 228/// "unwind" part of these invokes jump to a landing pad within the current 229/// function. This is a candidate to merge the selector associated with the URoR 230/// invoke with the one from the URoR's landing pad. 231bool DwarfEHPrepare::HandleURoRInvokes() { 232 if (!EHCatchAllValue) { 233 EHCatchAllValue = 234 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 235 if (!EHCatchAllValue) return false; 236 } 237 238 if (!SelectorIntrinsic) { 239 SelectorIntrinsic = 240 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 241 if (!SelectorIntrinsic) return false; 242 } 243 244 SmallPtrSet<IntrinsicInst*, 32> Sels; 245 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 246 FindAllCleanupSelectors(Sels, CatchAllSels); 247 248 if (!URoR) { 249 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 250 if (!URoR) return CleanupSelectors(CatchAllSels); 251 } 252 253 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 254 FindAllURoRInvokes(URoRInvokes); 255 256 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; 257 258 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 259 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { 260 const BasicBlock *SelBB = (*SI)->getParent(); 261 for (SmallPtrSet<InvokeInst*, 32>::iterator 262 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { 263 const BasicBlock *URoRBB = (*UI)->getParent(); 264 if (DT->dominates(SelBB, URoRBB)) { 265 SelsToConvert.insert(*SI); 266 break; 267 } 268 } 269 } 270 271 bool Changed = false; 272 273 if (Sels.size() != SelsToConvert.size()) { 274 // If we haven't been able to convert all of the clean-up selectors, then 275 // loop through the slow way to see if they still need to be converted. 276 if (!ExceptionValueIntrinsic) { 277 ExceptionValueIntrinsic = 278 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); 279 if (!ExceptionValueIntrinsic) 280 return CleanupSelectors(CatchAllSels); 281 } 282 283 for (Value::use_iterator 284 I = ExceptionValueIntrinsic->use_begin(), 285 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 286 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); 287 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 288 289 bool URoRInvoke = false; 290 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 291 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls); 292 293 if (URoRInvoke) { 294 // This EH pointer is being used by an invoke of an URoR instruction and 295 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 296 // need to convert it to a 'catch-all'. 297 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 298 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 299 if (!HasCatchAllInSelector(*SI)) 300 SelsToConvert.insert(*SI); 301 } 302 } 303 } 304 305 if (!SelsToConvert.empty()) { 306 // Convert all clean-up eh.selectors, which are associated with "invokes" of 307 // URoR calls, into catch-all eh.selectors. 308 Changed = true; 309 310 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 311 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 312 SI != SE; ++SI) { 313 IntrinsicInst *II = *SI; 314 315 // Use the exception object pointer and the personality function 316 // from the original selector. 317 CallSite CS(II); 318 IntrinsicInst::op_iterator I = CS.arg_begin(); 319 IntrinsicInst::op_iterator E = CS.arg_end(); 320 IntrinsicInst::op_iterator B = prior(E); 321 322 // Exclude last argument if it is an integer. 323 if (isa<ConstantInt>(B)) E = B; 324 325 // Add exception object pointer (front). 326 // Add personality function (next). 327 // Add in any filter IDs (rest). 328 SmallVector<Value*, 8> Args(I, E); 329 330 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 331 332 CallInst *NewSelector = 333 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 334 "eh.sel.catch.all", II); 335 336 NewSelector->setTailCall(II->isTailCall()); 337 NewSelector->setAttributes(II->getAttributes()); 338 NewSelector->setCallingConv(II->getCallingConv()); 339 340 II->replaceAllUsesWith(NewSelector); 341 II->eraseFromParent(); 342 } 343 } 344 345 Changed |= CleanupSelectors(CatchAllSels); 346 return Changed; 347} 348 349/// NormalizeLandingPads - Normalize and discover landing pads, noting them 350/// in the LandingPads set. A landing pad is normal if the only CFG edges 351/// that end at it are unwind edges from invoke instructions. If we inlined 352/// through an invoke we could have a normal branch from the previous 353/// unwind block through to the landing pad for the original invoke. 354/// Abnormal landing pads are fixed up by redirecting all unwind edges to 355/// a new basic block which falls through to the original. 356bool DwarfEHPrepare::NormalizeLandingPads() { 357 bool Changed = false; 358 359 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 360 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 361 362 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 363 TerminatorInst *TI = I->getTerminator(); 364 if (!isa<InvokeInst>(TI)) 365 continue; 366 BasicBlock *LPad = TI->getSuccessor(1); 367 // Skip landing pads that have already been normalized. 368 if (LandingPads.count(LPad)) 369 continue; 370 371 // Check that only invoke unwind edges end at the landing pad. 372 bool OnlyUnwoundTo = true; 373 bool SwitchOK = usingSjLjEH; 374 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 375 PI != PE; ++PI) { 376 TerminatorInst *PT = (*PI)->getTerminator(); 377 // The SjLj dispatch block uses a switch instruction. This is effectively 378 // an unwind edge, so we can disregard it here. There will only ever 379 // be one dispatch, however, so if there are multiple switches, one 380 // of them truly is a normal edge, not an unwind edge. 381 if (SwitchOK && isa<SwitchInst>(PT)) { 382 SwitchOK = false; 383 continue; 384 } 385 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 386 OnlyUnwoundTo = false; 387 break; 388 } 389 } 390 391 if (OnlyUnwoundTo) { 392 // Only unwind edges lead to the landing pad. Remember the landing pad. 393 LandingPads.insert(LPad); 394 continue; 395 } 396 397 // At least one normal edge ends at the landing pad. Redirect the unwind 398 // edges to a new basic block which falls through into this one. 399 400 // Create the new basic block. 401 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 402 LPad->getName() + "_unwind_edge"); 403 404 // Insert it into the function right before the original landing pad. 405 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 406 407 // Redirect unwind edges from the original landing pad to NewBB. 408 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 409 TerminatorInst *PT = (*PI++)->getTerminator(); 410 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 411 // Unwind to the new block. 412 PT->setSuccessor(1, NewBB); 413 } 414 415 // If there are any PHI nodes in LPad, we need to update them so that they 416 // merge incoming values from NewBB instead. 417 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 418 PHINode *PN = cast<PHINode>(II); 419 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 420 421 // Check to see if all of the values coming in via unwind edges are the 422 // same. If so, we don't need to create a new PHI node. 423 Value *InVal = PN->getIncomingValueForBlock(*PB); 424 for (pred_iterator PI = PB; PI != PE; ++PI) { 425 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 426 InVal = 0; 427 break; 428 } 429 } 430 431 if (InVal == 0) { 432 // Different unwind edges have different values. Create a new PHI node 433 // in NewBB. 434 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", 435 NewBB); 436 // Add an entry for each unwind edge, using the value from the old PHI. 437 for (pred_iterator PI = PB; PI != PE; ++PI) 438 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 439 440 // Now use this new PHI as the common incoming value for NewBB in PN. 441 InVal = NewPN; 442 } 443 444 // Revector exactly one entry in the PHI node to come from NewBB 445 // and delete all other entries that come from unwind edges. If 446 // there are both normal and unwind edges from the same predecessor, 447 // this leaves an entry for the normal edge. 448 for (pred_iterator PI = PB; PI != PE; ++PI) 449 PN->removeIncomingValue(*PI); 450 PN->addIncoming(InVal, NewBB); 451 } 452 453 // Add a fallthrough from NewBB to the original landing pad. 454 BranchInst::Create(LPad, NewBB); 455 456 // Now update DominatorTree analysis information. 457 DT->splitBlock(NewBB); 458 459 // Remember the newly constructed landing pad. The original landing pad 460 // LPad is no longer a landing pad now that all unwind edges have been 461 // revectored to NewBB. 462 LandingPads.insert(NewBB); 463 ++NumLandingPadsSplit; 464 Changed = true; 465 } 466 467 return Changed; 468} 469 470/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 471/// rethrowing any previously caught exception. This will crash horribly 472/// at runtime if there is no such exception: using unwind to throw a new 473/// exception is currently not supported. 474bool DwarfEHPrepare::LowerUnwinds() { 475 SmallVector<TerminatorInst*, 16> UnwindInsts; 476 477 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 478 TerminatorInst *TI = I->getTerminator(); 479 if (isa<UnwindInst>(TI)) 480 UnwindInsts.push_back(TI); 481 } 482 483 if (UnwindInsts.empty()) return false; 484 485 // Find the rewind function if we didn't already. 486 if (!RewindFunction) { 487 LLVMContext &Ctx = UnwindInsts[0]->getContext(); 488 std::vector<const Type*> 489 Params(1, Type::getInt8PtrTy(Ctx)); 490 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 491 Params, false); 492 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 493 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 494 } 495 496 bool Changed = false; 497 498 for (SmallVectorImpl<TerminatorInst*>::iterator 499 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { 500 TerminatorInst *TI = *I; 501 502 // Replace the unwind instruction with a call to _Unwind_Resume (or the 503 // appropriate target equivalent) followed by an UnreachableInst. 504 505 // Create the call... 506 CallInst *CI = CallInst::Create(RewindFunction, 507 CreateExceptionValueCall(TI->getParent()), 508 "", TI); 509 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 510 // ...followed by an UnreachableInst. 511 new UnreachableInst(TI->getContext(), TI); 512 513 // Nuke the unwind instruction. 514 TI->eraseFromParent(); 515 ++NumUnwindsLowered; 516 Changed = true; 517 } 518 519 return Changed; 520} 521 522/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 523/// landing pads by replacing calls outside of landing pads with direct use of 524/// a register holding the appropriate value; this requires adding calls inside 525/// all landing pads to initialize the register. Also, move eh.exception calls 526/// inside landing pads to the start of the landing pad (optional, but may make 527/// things simpler for later passes). 528bool DwarfEHPrepare::MoveExceptionValueCalls() { 529 // If the eh.exception intrinsic is not declared in the module then there is 530 // nothing to do. Speed up compilation by checking for this common case. 531 if (!ExceptionValueIntrinsic && 532 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 533 return false; 534 535 bool Changed = false; 536 537 // Move calls to eh.exception that are inside a landing pad to the start of 538 // the landing pad. 539 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end(); 540 LI != LE; ++LI) { 541 BasicBlock *LP = *LI; 542 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end(); 543 II != IE;) 544 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 545 // Found a call to eh.exception. 546 if (!EI->use_empty()) { 547 // If there is already a call to eh.exception at the start of the 548 // landing pad, then get hold of it; otherwise create such a call. 549 Value *CallAtStart = CreateExceptionValueCall(LP); 550 551 // If the call was at the start of a landing pad then leave it alone. 552 if (EI == CallAtStart) 553 continue; 554 EI->replaceAllUsesWith(CallAtStart); 555 } 556 EI->eraseFromParent(); 557 ++NumExceptionValuesMoved; 558 Changed = true; 559 } 560 } 561 562 // Look for calls to eh.exception that are not in a landing pad. If one is 563 // found, then a register that holds the exception value will be created in 564 // each landing pad, and the SSAUpdater will be used to compute the values 565 // returned by eh.exception calls outside of landing pads. 566 SSAUpdater SSA; 567 568 // Remember where we found the eh.exception call, to avoid rescanning earlier 569 // basic blocks which we already know contain no eh.exception calls. 570 bool FoundCallOutsideLandingPad = false; 571 Function::iterator BB = F->begin(); 572 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 573 // Skip over landing pads. 574 if (LandingPads.count(BB)) 575 continue; 576 577 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 578 II != IE; ++II) 579 if (isa<EHExceptionInst>(II)) { 580 SSA.Initialize(II->getType(), II->getName()); 581 FoundCallOutsideLandingPad = true; 582 break; 583 } 584 585 if (FoundCallOutsideLandingPad) 586 break; 587 } 588 589 // If all calls to eh.exception are in landing pads then we are done. 590 if (!FoundCallOutsideLandingPad) 591 return Changed; 592 593 // Add a call to eh.exception at the start of each landing pad, and tell the 594 // SSAUpdater that this is the value produced by the landing pad. 595 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 596 LI != LE; ++LI) 597 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI)); 598 599 // Now turn all calls to eh.exception that are not in a landing pad into a use 600 // of the appropriate register. 601 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 602 // Skip over landing pads. 603 if (LandingPads.count(BB)) 604 continue; 605 606 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 607 II != IE;) 608 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 609 // Found a call to eh.exception, replace it with the value from any 610 // upstream landing pad(s). 611 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB)); 612 EI->eraseFromParent(); 613 ++NumExceptionValuesMoved; 614 } 615 } 616 617 return true; 618} 619 620/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 621/// the start of the basic block (unless there already is one, in which case 622/// the existing call is returned). 623Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 624 Instruction *Start = BB->getFirstNonPHIOrDbg(); 625 // Is this a call to eh.exception? 626 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 627 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 628 // Reuse the existing call. 629 return Start; 630 631 // Find the eh.exception intrinsic if we didn't already. 632 if (!ExceptionValueIntrinsic) 633 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 634 Intrinsic::eh_exception); 635 636 // Create the call. 637 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 638} 639 640bool DwarfEHPrepare::runOnFunction(Function &Fn) { 641 bool Changed = false; 642 643 // Initialize internal state. 644 DT = &getAnalysis<DominatorTree>(); 645 F = &Fn; 646 647 // Ensure that only unwind edges end at landing pads (a landing pad is a 648 // basic block where an invoke unwind edge ends). 649 Changed |= NormalizeLandingPads(); 650 651 // Turn unwind instructions into libcalls. 652 Changed |= LowerUnwinds(); 653 654 // TODO: Move eh.selector calls to landing pads and combine them. 655 656 // Move eh.exception calls to landing pads. 657 Changed |= MoveExceptionValueCalls(); 658 659 Changed |= HandleURoRInvokes(); 660 661 LandingPads.clear(); 662 663 return Changed; 664} 665