DwarfEHPrepare.cpp revision edac4923dc2e1694f7004123ccd7c1af952d0d68
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(NumResumesLowered, "Number of eh.resume calls lowered"); 34STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); 35 36namespace { 37 class DwarfEHPrepare : public FunctionPass { 38 const TargetMachine *TM; 39 const TargetLowering *TLI; 40 41 // The eh.exception intrinsic. 42 Function *ExceptionValueIntrinsic; 43 44 // The eh.selector intrinsic. 45 Function *SelectorIntrinsic; 46 47 // _Unwind_Resume_or_Rethrow or _Unwind_SjLj_Resume call. 48 Constant *URoR; 49 50 // The EH language-specific catch-all type. 51 GlobalVariable *EHCatchAllValue; 52 53 // _Unwind_Resume or the target equivalent. 54 Constant *RewindFunction; 55 56 // We both use and preserve dominator info. 57 DominatorTree *DT; 58 59 // The function we are running on. 60 Function *F; 61 62 // The landing pads for this function. 63 typedef SmallPtrSet<BasicBlock*, 8> BBSet; 64 BBSet LandingPads; 65 66 bool NormalizeLandingPads(); 67 bool LowerUnwindsAndResumes(); 68 bool MoveExceptionValueCalls(); 69 70 Instruction *CreateExceptionValueCall(BasicBlock *BB); 71 72 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still 73 /// use the "llvm.eh.catch.all.value" call need to convert to using its 74 /// initializer instead. 75 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); 76 77 bool HasCatchAllInSelector(IntrinsicInst *); 78 79 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 80 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 81 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels); 82 83 /// FindAllURoRInvokes - Find all URoR invokes in the function. 84 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); 85 86 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 87 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to 88 /// a landing pad within the current function. This is a candidate to merge 89 /// the selector associated with the URoR invoke with the one from the 90 /// URoR's landing pad. 91 bool HandleURoRInvokes(); 92 93 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated 94 /// with the eh.exception call. This recursively looks past instructions 95 /// which don't change the EH pointer value, like casts or PHI nodes. 96 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 97 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 98 SmallPtrSet<PHINode*, 32> &SeenPHIs); 99 100 public: 101 static char ID; // Pass identification, replacement for typeid. 102 DwarfEHPrepare(const TargetMachine *tm) : 103 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), 104 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 105 URoR(0), EHCatchAllValue(0), RewindFunction(0) { 106 initializeDominatorTreePass(*PassRegistry::getPassRegistry()); 107 } 108 109 virtual bool runOnFunction(Function &Fn); 110 111 // getAnalysisUsage - We need the dominator tree for handling URoR. 112 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 113 AU.addRequired<DominatorTree>(); 114 AU.addPreserved<DominatorTree>(); 115 } 116 117 const char *getPassName() const { 118 return "Exception handling preparation"; 119 } 120 121 }; 122} // end anonymous namespace 123 124char DwarfEHPrepare::ID = 0; 125 126FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { 127 return new DwarfEHPrepare(tm); 128} 129 130/// HasCatchAllInSelector - Return true if the intrinsic instruction has a 131/// catch-all. 132bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 133 if (!EHCatchAllValue) return false; 134 135 unsigned ArgIdx = II->getNumArgOperands() - 1; 136 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 137 return GV == EHCatchAllValue; 138} 139 140/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 141void DwarfEHPrepare:: 142FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 143 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 144 for (Value::use_iterator 145 I = SelectorIntrinsic->use_begin(), 146 E = SelectorIntrinsic->use_end(); I != E; ++I) { 147 IntrinsicInst *II = cast<IntrinsicInst>(*I); 148 149 if (II->getParent()->getParent() != F) 150 continue; 151 152 if (!HasCatchAllInSelector(II)) 153 Sels.insert(II); 154 else 155 CatchAllSels.insert(II); 156 } 157} 158 159/// FindAllURoRInvokes - Find all URoR invokes in the function. 160void DwarfEHPrepare:: 161FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 162 for (Value::use_iterator 163 I = URoR->use_begin(), 164 E = URoR->use_end(); I != E; ++I) { 165 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 166 URoRInvokes.insert(II); 167 } 168} 169 170/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 171/// the "llvm.eh.catch.all.value" call need to convert to using its 172/// initializer instead. 173bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 174 if (!EHCatchAllValue) return false; 175 176 if (!SelectorIntrinsic) { 177 SelectorIntrinsic = 178 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 179 if (!SelectorIntrinsic) return false; 180 } 181 182 bool Changed = false; 183 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 184 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 185 IntrinsicInst *Sel = *I; 186 187 // Index of the "llvm.eh.catch.all.value" variable. 188 unsigned OpIdx = Sel->getNumArgOperands() - 1; 189 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 190 if (GV != EHCatchAllValue) continue; 191 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 192 Changed = true; 193 } 194 195 return Changed; 196} 197 198/// FindSelectorAndURoR - Find the eh.selector call associated with the 199/// eh.exception call. And indicate if there is a URoR "invoke" associated with 200/// the eh.exception call. This recursively looks past instructions which don't 201/// change the EH pointer value, like casts or PHI nodes. 202bool 203DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 204 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 205 SmallPtrSet<PHINode*, 32> &SeenPHIs) { 206 bool Changed = false; 207 208 for (Value::use_iterator 209 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 210 Instruction *II = dyn_cast<Instruction>(*I); 211 if (!II || II->getParent()->getParent() != F) continue; 212 213 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 214 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 215 SelCalls.insert(Sel); 216 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 217 if (Invoke->getCalledFunction() == URoR) 218 URoRInvoke = true; 219 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 220 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls, SeenPHIs); 221 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 222 if (SeenPHIs.insert(PN)) 223 // Don't process a PHI node more than once. 224 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls, SeenPHIs); 225 } 226 } 227 228 return Changed; 229} 230 231/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 232/// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to a 233/// landing pad within the current function. This is a candidate to merge the 234/// selector associated with the URoR invoke with the one from the URoR's 235/// landing pad. 236bool DwarfEHPrepare::HandleURoRInvokes() { 237 if (!EHCatchAllValue) { 238 EHCatchAllValue = 239 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 240 if (!EHCatchAllValue) return false; 241 } 242 243 if (!SelectorIntrinsic) { 244 SelectorIntrinsic = 245 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 246 if (!SelectorIntrinsic) return false; 247 } 248 249 SmallPtrSet<IntrinsicInst*, 32> Sels; 250 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 251 FindAllCleanupSelectors(Sels, CatchAllSels); 252 253 if (!URoR) { 254 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 255 if (!URoR) return CleanupSelectors(CatchAllSels); 256 } 257 258 SmallPtrSet<InvokeInst*, 32> URoRInvokes; 259 FindAllURoRInvokes(URoRInvokes); 260 261 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; 262 263 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 264 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { 265 const BasicBlock *SelBB = (*SI)->getParent(); 266 for (SmallPtrSet<InvokeInst*, 32>::iterator 267 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { 268 const BasicBlock *URoRBB = (*UI)->getParent(); 269 if (DT->dominates(SelBB, URoRBB)) { 270 SelsToConvert.insert(*SI); 271 break; 272 } 273 } 274 } 275 276 bool Changed = false; 277 278 if (Sels.size() != SelsToConvert.size()) { 279 // If we haven't been able to convert all of the clean-up selectors, then 280 // loop through the slow way to see if they still need to be converted. 281 if (!ExceptionValueIntrinsic) { 282 ExceptionValueIntrinsic = 283 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); 284 if (!ExceptionValueIntrinsic) 285 return CleanupSelectors(CatchAllSels); 286 } 287 288 for (Value::use_iterator 289 I = ExceptionValueIntrinsic->use_begin(), 290 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { 291 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); 292 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; 293 294 bool URoRInvoke = false; 295 SmallPtrSet<IntrinsicInst*, 8> SelCalls; 296 SmallPtrSet<PHINode*, 32> SeenPHIs; 297 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls, SeenPHIs); 298 299 if (URoRInvoke) { 300 // This EH pointer is being used by an invoke of an URoR instruction and 301 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we 302 // need to convert it to a 'catch-all'. 303 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 304 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) 305 if (!HasCatchAllInSelector(*SI)) 306 SelsToConvert.insert(*SI); 307 } 308 } 309 } 310 311 if (!SelsToConvert.empty()) { 312 // Convert all clean-up eh.selectors, which are associated with "invokes" of 313 // URoR calls, into catch-all eh.selectors. 314 Changed = true; 315 316 for (SmallPtrSet<IntrinsicInst*, 8>::iterator 317 SI = SelsToConvert.begin(), SE = SelsToConvert.end(); 318 SI != SE; ++SI) { 319 IntrinsicInst *II = *SI; 320 321 // Use the exception object pointer and the personality function 322 // from the original selector. 323 CallSite CS(II); 324 IntrinsicInst::op_iterator I = CS.arg_begin(); 325 IntrinsicInst::op_iterator E = CS.arg_end(); 326 IntrinsicInst::op_iterator B = prior(E); 327 328 // Exclude last argument if it is an integer. 329 if (isa<ConstantInt>(B)) E = B; 330 331 // Add exception object pointer (front). 332 // Add personality function (next). 333 // Add in any filter IDs (rest). 334 SmallVector<Value*, 8> Args(I, E); 335 336 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. 337 338 CallInst *NewSelector = 339 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), 340 "eh.sel.catch.all", II); 341 342 NewSelector->setTailCall(II->isTailCall()); 343 NewSelector->setAttributes(II->getAttributes()); 344 NewSelector->setCallingConv(II->getCallingConv()); 345 346 II->replaceAllUsesWith(NewSelector); 347 II->eraseFromParent(); 348 } 349 } 350 351 Changed |= CleanupSelectors(CatchAllSels); 352 return Changed; 353} 354 355/// NormalizeLandingPads - Normalize and discover landing pads, noting them 356/// in the LandingPads set. A landing pad is normal if the only CFG edges 357/// that end at it are unwind edges from invoke instructions. If we inlined 358/// through an invoke we could have a normal branch from the previous 359/// unwind block through to the landing pad for the original invoke. 360/// Abnormal landing pads are fixed up by redirecting all unwind edges to 361/// a new basic block which falls through to the original. 362bool DwarfEHPrepare::NormalizeLandingPads() { 363 bool Changed = false; 364 365 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 366 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 367 368 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 369 TerminatorInst *TI = I->getTerminator(); 370 if (!isa<InvokeInst>(TI)) 371 continue; 372 BasicBlock *LPad = TI->getSuccessor(1); 373 // Skip landing pads that have already been normalized. 374 if (LandingPads.count(LPad)) 375 continue; 376 377 // Check that only invoke unwind edges end at the landing pad. 378 bool OnlyUnwoundTo = true; 379 bool SwitchOK = usingSjLjEH; 380 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 381 PI != PE; ++PI) { 382 TerminatorInst *PT = (*PI)->getTerminator(); 383 // The SjLj dispatch block uses a switch instruction. This is effectively 384 // an unwind edge, so we can disregard it here. There will only ever 385 // be one dispatch, however, so if there are multiple switches, one 386 // of them truly is a normal edge, not an unwind edge. 387 if (SwitchOK && isa<SwitchInst>(PT)) { 388 SwitchOK = false; 389 continue; 390 } 391 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 392 OnlyUnwoundTo = false; 393 break; 394 } 395 } 396 397 if (OnlyUnwoundTo) { 398 // Only unwind edges lead to the landing pad. Remember the landing pad. 399 LandingPads.insert(LPad); 400 continue; 401 } 402 403 // At least one normal edge ends at the landing pad. Redirect the unwind 404 // edges to a new basic block which falls through into this one. 405 406 // Create the new basic block. 407 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 408 LPad->getName() + "_unwind_edge"); 409 410 // Insert it into the function right before the original landing pad. 411 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 412 413 // Redirect unwind edges from the original landing pad to NewBB. 414 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 415 TerminatorInst *PT = (*PI++)->getTerminator(); 416 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 417 // Unwind to the new block. 418 PT->setSuccessor(1, NewBB); 419 } 420 421 // If there are any PHI nodes in LPad, we need to update them so that they 422 // merge incoming values from NewBB instead. 423 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 424 PHINode *PN = cast<PHINode>(II); 425 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 426 427 // Check to see if all of the values coming in via unwind edges are the 428 // same. If so, we don't need to create a new PHI node. 429 Value *InVal = PN->getIncomingValueForBlock(*PB); 430 for (pred_iterator PI = PB; PI != PE; ++PI) { 431 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 432 InVal = 0; 433 break; 434 } 435 } 436 437 if (InVal == 0) { 438 // Different unwind edges have different values. Create a new PHI node 439 // in NewBB. 440 PHINode *NewPN = PHINode::Create(PN->getType(), 441 PN->getNumIncomingValues(), 442 PN->getName()+".unwind", NewBB); 443 // Add an entry for each unwind edge, using the value from the old PHI. 444 for (pred_iterator PI = PB; PI != PE; ++PI) 445 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 446 447 // Now use this new PHI as the common incoming value for NewBB in PN. 448 InVal = NewPN; 449 } 450 451 // Revector exactly one entry in the PHI node to come from NewBB 452 // and delete all other entries that come from unwind edges. If 453 // there are both normal and unwind edges from the same predecessor, 454 // this leaves an entry for the normal edge. 455 for (pred_iterator PI = PB; PI != PE; ++PI) 456 PN->removeIncomingValue(*PI); 457 PN->addIncoming(InVal, NewBB); 458 } 459 460 // Add a fallthrough from NewBB to the original landing pad. 461 BranchInst::Create(LPad, NewBB); 462 463 // Now update DominatorTree analysis information. 464 DT->splitBlock(NewBB); 465 466 // Remember the newly constructed landing pad. The original landing pad 467 // LPad is no longer a landing pad now that all unwind edges have been 468 // revectored to NewBB. 469 LandingPads.insert(NewBB); 470 ++NumLandingPadsSplit; 471 Changed = true; 472 } 473 474 return Changed; 475} 476 477/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 478/// rethrowing any previously caught exception. This will crash horribly 479/// at runtime if there is no such exception: using unwind to throw a new 480/// exception is currently not supported. 481bool DwarfEHPrepare::LowerUnwindsAndResumes() { 482 SmallVector<Instruction*, 16> ResumeInsts; 483 484 for (Function::iterator fi = F->begin(), fe = F->end(); fi != fe; ++fi) { 485 for (BasicBlock::iterator bi = fi->begin(), be = fi->end(); bi != be; ++bi){ 486 if (isa<UnwindInst>(bi)) 487 ResumeInsts.push_back(bi); 488 else if (CallInst *call = dyn_cast<CallInst>(bi)) 489 if (Function *fn = dyn_cast<Function>(call->getCalledValue())) 490 if (fn->getName() == "llvm.eh.resume") 491 ResumeInsts.push_back(bi); 492 } 493 } 494 495 if (ResumeInsts.empty()) return false; 496 497 // Find the rewind function if we didn't already. 498 if (!RewindFunction) { 499 LLVMContext &Ctx = ResumeInsts[0]->getContext(); 500 std::vector<const Type*> 501 Params(1, Type::getInt8PtrTy(Ctx)); 502 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 503 Params, false); 504 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 505 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 506 } 507 508 bool Changed = false; 509 510 for (SmallVectorImpl<Instruction*>::iterator 511 I = ResumeInsts.begin(), E = ResumeInsts.end(); I != E; ++I) { 512 Instruction *RI = *I; 513 514 // Replace the resuming instruction with a call to _Unwind_Resume (or the 515 // appropriate target equivalent). 516 517 llvm::Value *ExnValue; 518 if (isa<UnwindInst>(RI)) 519 ExnValue = CreateExceptionValueCall(RI->getParent()); 520 else 521 ExnValue = cast<CallInst>(RI)->getArgOperand(0); 522 523 // Create the call... 524 CallInst *CI = CallInst::Create(RewindFunction, ExnValue, "", RI); 525 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 526 527 // ...followed by an UnreachableInst, if it was an unwind. 528 // Calls to llvm.eh.resume are typically already followed by this. 529 if (isa<UnwindInst>(RI)) 530 new UnreachableInst(RI->getContext(), RI); 531 532 if (isa<UnwindInst>(RI)) 533 ++NumUnwindsLowered; 534 else 535 ++NumResumesLowered; 536 537 // Nuke the resume instruction. 538 RI->eraseFromParent(); 539 540 Changed = true; 541 } 542 543 return Changed; 544} 545 546/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 547/// landing pads by replacing calls outside of landing pads with direct use of 548/// a register holding the appropriate value; this requires adding calls inside 549/// all landing pads to initialize the register. Also, move eh.exception calls 550/// inside landing pads to the start of the landing pad (optional, but may make 551/// things simpler for later passes). 552bool DwarfEHPrepare::MoveExceptionValueCalls() { 553 // If the eh.exception intrinsic is not declared in the module then there is 554 // nothing to do. Speed up compilation by checking for this common case. 555 if (!ExceptionValueIntrinsic && 556 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 557 return false; 558 559 bool Changed = false; 560 561 // Move calls to eh.exception that are inside a landing pad to the start of 562 // the landing pad. 563 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end(); 564 LI != LE; ++LI) { 565 BasicBlock *LP = *LI; 566 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end(); 567 II != IE;) 568 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 569 // Found a call to eh.exception. 570 if (!EI->use_empty()) { 571 // If there is already a call to eh.exception at the start of the 572 // landing pad, then get hold of it; otherwise create such a call. 573 Value *CallAtStart = CreateExceptionValueCall(LP); 574 575 // If the call was at the start of a landing pad then leave it alone. 576 if (EI == CallAtStart) 577 continue; 578 EI->replaceAllUsesWith(CallAtStart); 579 } 580 EI->eraseFromParent(); 581 ++NumExceptionValuesMoved; 582 Changed = true; 583 } 584 } 585 586 // Look for calls to eh.exception that are not in a landing pad. If one is 587 // found, then a register that holds the exception value will be created in 588 // each landing pad, and the SSAUpdater will be used to compute the values 589 // returned by eh.exception calls outside of landing pads. 590 SSAUpdater SSA; 591 592 // Remember where we found the eh.exception call, to avoid rescanning earlier 593 // basic blocks which we already know contain no eh.exception calls. 594 bool FoundCallOutsideLandingPad = false; 595 Function::iterator BB = F->begin(); 596 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 597 // Skip over landing pads. 598 if (LandingPads.count(BB)) 599 continue; 600 601 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 602 II != IE; ++II) 603 if (isa<EHExceptionInst>(II)) { 604 SSA.Initialize(II->getType(), II->getName()); 605 FoundCallOutsideLandingPad = true; 606 break; 607 } 608 609 if (FoundCallOutsideLandingPad) 610 break; 611 } 612 613 // If all calls to eh.exception are in landing pads then we are done. 614 if (!FoundCallOutsideLandingPad) 615 return Changed; 616 617 // Add a call to eh.exception at the start of each landing pad, and tell the 618 // SSAUpdater that this is the value produced by the landing pad. 619 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 620 LI != LE; ++LI) 621 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI)); 622 623 // Now turn all calls to eh.exception that are not in a landing pad into a use 624 // of the appropriate register. 625 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 626 // Skip over landing pads. 627 if (LandingPads.count(BB)) 628 continue; 629 630 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 631 II != IE;) 632 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 633 // Found a call to eh.exception, replace it with the value from any 634 // upstream landing pad(s). 635 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB)); 636 EI->eraseFromParent(); 637 ++NumExceptionValuesMoved; 638 } 639 } 640 641 return true; 642} 643 644/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 645/// the start of the basic block (unless there already is one, in which case 646/// the existing call is returned). 647Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 648 Instruction *Start = BB->getFirstNonPHIOrDbg(); 649 // Is this a call to eh.exception? 650 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 651 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 652 // Reuse the existing call. 653 return Start; 654 655 // Find the eh.exception intrinsic if we didn't already. 656 if (!ExceptionValueIntrinsic) 657 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 658 Intrinsic::eh_exception); 659 660 // Create the call. 661 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 662} 663 664bool DwarfEHPrepare::runOnFunction(Function &Fn) { 665 bool Changed = false; 666 667 // Initialize internal state. 668 DT = &getAnalysis<DominatorTree>(); 669 F = &Fn; 670 671 // Ensure that only unwind edges end at landing pads (a landing pad is a 672 // basic block where an invoke unwind edge ends). 673 Changed |= NormalizeLandingPads(); 674 675 // Turn unwind instructions and eh.resume calls into libcalls. 676 Changed |= LowerUnwindsAndResumes(); 677 678 // TODO: Move eh.selector calls to landing pads and combine them. 679 680 // Move eh.exception calls to landing pads. 681 Changed |= MoveExceptionValueCalls(); 682 683 Changed |= HandleURoRInvokes(); 684 685 LandingPads.clear(); 686 687 return Changed; 688} 689