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" 29 using namespace llvm; 30 31 STATISTIC(NumLandingPadsSplit, "Number of landing pads split"); 32 STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); 33 STATISTIC(NumResumesLowered, "Number of eh.resume calls lowered"); 34 STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); 35 36 namespace { 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 InsertUnwindResumeCalls(); 67 68 bool NormalizeLandingPads(); 69 bool LowerUnwindsAndResumes(); 70 bool MoveExceptionValueCalls(); 71 72 Instruction *CreateExceptionValueCall(BasicBlock *BB); 73 74 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still 75 /// use the "llvm.eh.catch.all.value" call need to convert to using its 76 /// initializer instead. 77 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); 78 79 bool HasCatchAllInSelector(IntrinsicInst *); 80 81 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 82 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 83 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels); 84 85 /// FindAllURoRInvokes - Find all URoR invokes in the function. 86 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); 87 88 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 89 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to 90 /// a landing pad within the current function. This is a candidate to merge 91 /// the selector associated with the URoR invoke with the one from the 92 /// URoR's landing pad. 93 bool HandleURoRInvokes(); 94 95 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated 96 /// with the eh.exception call. This recursively looks past instructions 97 /// which don't change the EH pointer value, like casts or PHI nodes. 98 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 99 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 100 SmallPtrSet<PHINode*, 32> &SeenPHIs); 101 102 public: 103 static char ID; // Pass identification, replacement for typeid. 104 DwarfEHPrepare(const TargetMachine *tm) : 105 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), 106 ExceptionValueIntrinsic(0), SelectorIntrinsic(0), 107 URoR(0), EHCatchAllValue(0), RewindFunction(0) { 108 initializeDominatorTreePass(*PassRegistry::getPassRegistry()); 109 } 110 111 virtual bool runOnFunction(Function &Fn); 112 113 // getAnalysisUsage - We need the dominator tree for handling URoR. 114 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 115 AU.addRequired<DominatorTree>(); 116 AU.addPreserved<DominatorTree>(); 117 } 118 119 const char *getPassName() const { 120 return "Exception handling preparation"; 121 } 122 123 }; 124 } // end anonymous namespace 125 126 char DwarfEHPrepare::ID = 0; 127 128 FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { 129 return new DwarfEHPrepare(tm); 130 } 131 132 /// HasCatchAllInSelector - Return true if the intrinsic instruction has a 133 /// catch-all. 134 bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { 135 if (!EHCatchAllValue) return false; 136 137 unsigned ArgIdx = II->getNumArgOperands() - 1; 138 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); 139 return GV == EHCatchAllValue; 140 } 141 142 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. 143 void DwarfEHPrepare:: 144 FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, 145 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { 146 for (Value::use_iterator 147 I = SelectorIntrinsic->use_begin(), 148 E = SelectorIntrinsic->use_end(); I != E; ++I) { 149 IntrinsicInst *II = cast<IntrinsicInst>(*I); 150 151 if (II->getParent()->getParent() != F) 152 continue; 153 154 if (!HasCatchAllInSelector(II)) 155 Sels.insert(II); 156 else 157 CatchAllSels.insert(II); 158 } 159 } 160 161 /// FindAllURoRInvokes - Find all URoR invokes in the function. 162 void DwarfEHPrepare:: 163 FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { 164 for (Value::use_iterator 165 I = URoR->use_begin(), 166 E = URoR->use_end(); I != E; ++I) { 167 if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) 168 URoRInvokes.insert(II); 169 } 170 } 171 172 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use 173 /// the "llvm.eh.catch.all.value" call need to convert to using its 174 /// initializer instead. 175 bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { 176 if (!EHCatchAllValue) return false; 177 178 if (!SelectorIntrinsic) { 179 SelectorIntrinsic = 180 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 181 if (!SelectorIntrinsic) return false; 182 } 183 184 bool Changed = false; 185 for (SmallPtrSet<IntrinsicInst*, 32>::iterator 186 I = Sels.begin(), E = Sels.end(); I != E; ++I) { 187 IntrinsicInst *Sel = *I; 188 189 // Index of the "llvm.eh.catch.all.value" variable. 190 unsigned OpIdx = Sel->getNumArgOperands() - 1; 191 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); 192 if (GV != EHCatchAllValue) continue; 193 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); 194 Changed = true; 195 } 196 197 return Changed; 198 } 199 200 /// FindSelectorAndURoR - Find the eh.selector call associated with the 201 /// eh.exception call. And indicate if there is a URoR "invoke" associated with 202 /// the eh.exception call. This recursively looks past instructions which don't 203 /// change the EH pointer value, like casts or PHI nodes. 204 bool 205 DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, 206 SmallPtrSet<IntrinsicInst*, 8> &SelCalls, 207 SmallPtrSet<PHINode*, 32> &SeenPHIs) { 208 bool Changed = false; 209 210 for (Value::use_iterator 211 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { 212 Instruction *II = dyn_cast<Instruction>(*I); 213 if (!II || II->getParent()->getParent() != F) continue; 214 215 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { 216 if (Sel->getIntrinsicID() == Intrinsic::eh_selector) 217 SelCalls.insert(Sel); 218 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { 219 if (Invoke->getCalledFunction() == URoR) 220 URoRInvoke = true; 221 } else if (CastInst *CI = dyn_cast<CastInst>(II)) { 222 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls, SeenPHIs); 223 } else if (PHINode *PN = dyn_cast<PHINode>(II)) { 224 if (SeenPHIs.insert(PN)) 225 // Don't process a PHI node more than once. 226 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls, SeenPHIs); 227 } 228 } 229 230 return Changed; 231 } 232 233 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or 234 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to a 235 /// landing pad within the current function. This is a candidate to merge the 236 /// selector associated with the URoR invoke with the one from the URoR's 237 /// landing pad. 238 bool DwarfEHPrepare::HandleURoRInvokes() { 239 if (!EHCatchAllValue) { 240 EHCatchAllValue = 241 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); 242 if (!EHCatchAllValue) return false; 243 } 244 245 if (!SelectorIntrinsic) { 246 SelectorIntrinsic = 247 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); 248 if (!SelectorIntrinsic) return false; 249 } 250 251 SmallPtrSet<IntrinsicInst*, 32> Sels; 252 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; 253 FindAllCleanupSelectors(Sels, CatchAllSels); 254 255 if (!URoR) { 256 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); 257 if (!URoR) return CleanupSelectors(CatchAllSels); 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, "eh.sel.catch.all", II); 342 343 NewSelector->setTailCall(II->isTailCall()); 344 NewSelector->setAttributes(II->getAttributes()); 345 NewSelector->setCallingConv(II->getCallingConv()); 346 347 II->replaceAllUsesWith(NewSelector); 348 II->eraseFromParent(); 349 } 350 } 351 352 Changed |= CleanupSelectors(CatchAllSels); 353 return Changed; 354 } 355 356 /// NormalizeLandingPads - Normalize and discover landing pads, noting them 357 /// in the LandingPads set. A landing pad is normal if the only CFG edges 358 /// that end at it are unwind edges from invoke instructions. If we inlined 359 /// through an invoke we could have a normal branch from the previous 360 /// unwind block through to the landing pad for the original invoke. 361 /// Abnormal landing pads are fixed up by redirecting all unwind edges to 362 /// a new basic block which falls through to the original. 363 bool DwarfEHPrepare::NormalizeLandingPads() { 364 bool Changed = false; 365 366 const MCAsmInfo *MAI = TM->getMCAsmInfo(); 367 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; 368 369 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 370 TerminatorInst *TI = I->getTerminator(); 371 if (!isa<InvokeInst>(TI)) 372 continue; 373 BasicBlock *LPad = TI->getSuccessor(1); 374 // Skip landing pads that have already been normalized. 375 if (LandingPads.count(LPad)) 376 continue; 377 378 // Check that only invoke unwind edges end at the landing pad. 379 bool OnlyUnwoundTo = true; 380 bool SwitchOK = usingSjLjEH; 381 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); 382 PI != PE; ++PI) { 383 TerminatorInst *PT = (*PI)->getTerminator(); 384 // The SjLj dispatch block uses a switch instruction. This is effectively 385 // an unwind edge, so we can disregard it here. There will only ever 386 // be one dispatch, however, so if there are multiple switches, one 387 // of them truly is a normal edge, not an unwind edge. 388 if (SwitchOK && isa<SwitchInst>(PT)) { 389 SwitchOK = false; 390 continue; 391 } 392 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { 393 OnlyUnwoundTo = false; 394 break; 395 } 396 } 397 398 if (OnlyUnwoundTo) { 399 // Only unwind edges lead to the landing pad. Remember the landing pad. 400 LandingPads.insert(LPad); 401 continue; 402 } 403 404 // At least one normal edge ends at the landing pad. Redirect the unwind 405 // edges to a new basic block which falls through into this one. 406 407 // Create the new basic block. 408 BasicBlock *NewBB = BasicBlock::Create(F->getContext(), 409 LPad->getName() + "_unwind_edge"); 410 411 // Insert it into the function right before the original landing pad. 412 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); 413 414 // Redirect unwind edges from the original landing pad to NewBB. 415 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { 416 TerminatorInst *PT = (*PI++)->getTerminator(); 417 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) 418 // Unwind to the new block. 419 PT->setSuccessor(1, NewBB); 420 } 421 422 // If there are any PHI nodes in LPad, we need to update them so that they 423 // merge incoming values from NewBB instead. 424 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { 425 PHINode *PN = cast<PHINode>(II); 426 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); 427 428 // Check to see if all of the values coming in via unwind edges are the 429 // same. If so, we don't need to create a new PHI node. 430 Value *InVal = PN->getIncomingValueForBlock(*PB); 431 for (pred_iterator PI = PB; PI != PE; ++PI) { 432 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { 433 InVal = 0; 434 break; 435 } 436 } 437 438 if (InVal == 0) { 439 // Different unwind edges have different values. Create a new PHI node 440 // in NewBB. 441 PHINode *NewPN = PHINode::Create(PN->getType(), 442 PN->getNumIncomingValues(), 443 PN->getName()+".unwind", NewBB); 444 // Add an entry for each unwind edge, using the value from the old PHI. 445 for (pred_iterator PI = PB; PI != PE; ++PI) 446 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); 447 448 // Now use this new PHI as the common incoming value for NewBB in PN. 449 InVal = NewPN; 450 } 451 452 // Revector exactly one entry in the PHI node to come from NewBB 453 // and delete all other entries that come from unwind edges. If 454 // there are both normal and unwind edges from the same predecessor, 455 // this leaves an entry for the normal edge. 456 for (pred_iterator PI = PB; PI != PE; ++PI) 457 PN->removeIncomingValue(*PI); 458 PN->addIncoming(InVal, NewBB); 459 } 460 461 // Add a fallthrough from NewBB to the original landing pad. 462 BranchInst::Create(LPad, NewBB); 463 464 // Now update DominatorTree analysis information. 465 DT->splitBlock(NewBB); 466 467 // Remember the newly constructed landing pad. The original landing pad 468 // LPad is no longer a landing pad now that all unwind edges have been 469 // revectored to NewBB. 470 LandingPads.insert(NewBB); 471 ++NumLandingPadsSplit; 472 Changed = true; 473 } 474 475 return Changed; 476 } 477 478 /// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, 479 /// rethrowing any previously caught exception. This will crash horribly 480 /// at runtime if there is no such exception: using unwind to throw a new 481 /// exception is currently not supported. 482 bool DwarfEHPrepare::LowerUnwindsAndResumes() { 483 SmallVector<Instruction*, 16> ResumeInsts; 484 485 for (Function::iterator fi = F->begin(), fe = F->end(); fi != fe; ++fi) { 486 for (BasicBlock::iterator bi = fi->begin(), be = fi->end(); bi != be; ++bi){ 487 if (isa<UnwindInst>(bi)) 488 ResumeInsts.push_back(bi); 489 else if (CallInst *call = dyn_cast<CallInst>(bi)) 490 if (Function *fn = dyn_cast<Function>(call->getCalledValue())) 491 if (fn->getName() == "llvm.eh.resume") 492 ResumeInsts.push_back(bi); 493 } 494 } 495 496 if (ResumeInsts.empty()) return false; 497 498 // Find the rewind function if we didn't already. 499 if (!RewindFunction) { 500 LLVMContext &Ctx = ResumeInsts[0]->getContext(); 501 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 502 Type::getInt8PtrTy(Ctx), false); 503 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 504 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 505 } 506 507 bool Changed = false; 508 509 for (SmallVectorImpl<Instruction*>::iterator 510 I = ResumeInsts.begin(), E = ResumeInsts.end(); I != E; ++I) { 511 Instruction *RI = *I; 512 513 // Replace the resuming instruction with a call to _Unwind_Resume (or the 514 // appropriate target equivalent). 515 516 llvm::Value *ExnValue; 517 if (isa<UnwindInst>(RI)) 518 ExnValue = CreateExceptionValueCall(RI->getParent()); 519 else 520 ExnValue = cast<CallInst>(RI)->getArgOperand(0); 521 522 // Create the call... 523 CallInst *CI = CallInst::Create(RewindFunction, ExnValue, "", RI); 524 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 525 526 // ...followed by an UnreachableInst, if it was an unwind. 527 // Calls to llvm.eh.resume are typically already followed by this. 528 if (isa<UnwindInst>(RI)) 529 new UnreachableInst(RI->getContext(), RI); 530 531 if (isa<UnwindInst>(RI)) 532 ++NumUnwindsLowered; 533 else 534 ++NumResumesLowered; 535 536 // Nuke the resume instruction. 537 RI->eraseFromParent(); 538 539 Changed = true; 540 } 541 542 return Changed; 543 } 544 545 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from 546 /// landing pads by replacing calls outside of landing pads with direct use of 547 /// a register holding the appropriate value; this requires adding calls inside 548 /// all landing pads to initialize the register. Also, move eh.exception calls 549 /// inside landing pads to the start of the landing pad (optional, but may make 550 /// things simpler for later passes). 551 bool DwarfEHPrepare::MoveExceptionValueCalls() { 552 // If the eh.exception intrinsic is not declared in the module then there is 553 // nothing to do. Speed up compilation by checking for this common case. 554 if (!ExceptionValueIntrinsic && 555 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) 556 return false; 557 558 bool Changed = false; 559 560 // Move calls to eh.exception that are inside a landing pad to the start of 561 // the landing pad. 562 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end(); 563 LI != LE; ++LI) { 564 BasicBlock *LP = *LI; 565 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end(); 566 II != IE;) 567 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 568 // Found a call to eh.exception. 569 if (!EI->use_empty()) { 570 // If there is already a call to eh.exception at the start of the 571 // landing pad, then get hold of it; otherwise create such a call. 572 Value *CallAtStart = CreateExceptionValueCall(LP); 573 574 // If the call was at the start of a landing pad then leave it alone. 575 if (EI == CallAtStart) 576 continue; 577 EI->replaceAllUsesWith(CallAtStart); 578 } 579 EI->eraseFromParent(); 580 ++NumExceptionValuesMoved; 581 Changed = true; 582 } 583 } 584 585 // Look for calls to eh.exception that are not in a landing pad. If one is 586 // found, then a register that holds the exception value will be created in 587 // each landing pad, and the SSAUpdater will be used to compute the values 588 // returned by eh.exception calls outside of landing pads. 589 SSAUpdater SSA; 590 591 // Remember where we found the eh.exception call, to avoid rescanning earlier 592 // basic blocks which we already know contain no eh.exception calls. 593 bool FoundCallOutsideLandingPad = false; 594 Function::iterator BB = F->begin(); 595 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 596 // Skip over landing pads. 597 if (LandingPads.count(BB)) 598 continue; 599 600 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 601 II != IE; ++II) 602 if (isa<EHExceptionInst>(II)) { 603 SSA.Initialize(II->getType(), II->getName()); 604 FoundCallOutsideLandingPad = true; 605 break; 606 } 607 608 if (FoundCallOutsideLandingPad) 609 break; 610 } 611 612 // If all calls to eh.exception are in landing pads then we are done. 613 if (!FoundCallOutsideLandingPad) 614 return Changed; 615 616 // Add a call to eh.exception at the start of each landing pad, and tell the 617 // SSAUpdater that this is the value produced by the landing pad. 618 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); 619 LI != LE; ++LI) 620 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI)); 621 622 // Now turn all calls to eh.exception that are not in a landing pad into a use 623 // of the appropriate register. 624 for (Function::iterator BE = F->end(); BB != BE; ++BB) { 625 // Skip over landing pads. 626 if (LandingPads.count(BB)) 627 continue; 628 629 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); 630 II != IE;) 631 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { 632 // Found a call to eh.exception, replace it with the value from any 633 // upstream landing pad(s). 634 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB)); 635 EI->eraseFromParent(); 636 ++NumExceptionValuesMoved; 637 } 638 } 639 640 return true; 641 } 642 643 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at 644 /// the start of the basic block (unless there already is one, in which case 645 /// the existing call is returned). 646 Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { 647 Instruction *Start = BB->getFirstNonPHIOrDbg(); 648 // Is this a call to eh.exception? 649 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) 650 if (CI->getIntrinsicID() == Intrinsic::eh_exception) 651 // Reuse the existing call. 652 return Start; 653 654 // Find the eh.exception intrinsic if we didn't already. 655 if (!ExceptionValueIntrinsic) 656 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), 657 Intrinsic::eh_exception); 658 659 // Create the call. 660 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); 661 } 662 663 /// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present 664 /// into calls to the appropriate _Unwind_Resume function. 665 bool DwarfEHPrepare::InsertUnwindResumeCalls() { 666 bool UsesNewEH = false; 667 SmallVector<ResumeInst*, 16> Resumes; 668 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 669 TerminatorInst *TI = I->getTerminator(); 670 if (ResumeInst *RI = dyn_cast<ResumeInst>(TI)) 671 Resumes.push_back(RI); 672 else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) 673 UsesNewEH = II->getUnwindDest()->isLandingPad(); 674 } 675 676 if (Resumes.empty()) 677 return UsesNewEH; 678 679 // Find the rewind function if we didn't already. 680 if (!RewindFunction) { 681 LLVMContext &Ctx = Resumes[0]->getContext(); 682 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), 683 Type::getInt8PtrTy(Ctx), false); 684 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); 685 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); 686 } 687 688 // Create the basic block where the _Unwind_Resume call will live. 689 LLVMContext &Ctx = F->getContext(); 690 BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", F); 691 PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), Resumes.size(), 692 "exn.obj", UnwindBB); 693 694 // Extract the exception object from the ResumeInst and add it to the PHI node 695 // that feeds the _Unwind_Resume call. 696 BasicBlock *UnwindBBDom = Resumes[0]->getParent(); 697 for (SmallVectorImpl<ResumeInst*>::iterator 698 I = Resumes.begin(), E = Resumes.end(); I != E; ++I) { 699 ResumeInst *RI = *I; 700 BranchInst::Create(UnwindBB, RI->getParent()); 701 ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0), 702 0, "exn.obj", RI); 703 PN->addIncoming(ExnObj, RI->getParent()); 704 UnwindBBDom = DT->findNearestCommonDominator(RI->getParent(), UnwindBBDom); 705 RI->eraseFromParent(); 706 } 707 708 // Call the function. 709 CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB); 710 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); 711 712 // We never expect _Unwind_Resume to return. 713 new UnreachableInst(Ctx, UnwindBB); 714 715 // Now update DominatorTree analysis information. 716 DT->addNewBlock(UnwindBB, UnwindBBDom); 717 return true; 718 } 719 720 bool DwarfEHPrepare::runOnFunction(Function &Fn) { 721 bool Changed = false; 722 723 // Initialize internal state. 724 DT = &getAnalysis<DominatorTree>(); // FIXME: We won't need this with the new EH. 725 F = &Fn; 726 727 if (InsertUnwindResumeCalls()) { 728 // FIXME: The reset of this function can go once the new EH is done. 729 LandingPads.clear(); 730 return true; 731 } 732 733 // Ensure that only unwind edges end at landing pads (a landing pad is a 734 // basic block where an invoke unwind edge ends). 735 Changed |= NormalizeLandingPads(); 736 737 // Turn unwind instructions and eh.resume calls into libcalls. 738 Changed |= LowerUnwindsAndResumes(); 739 740 // TODO: Move eh.selector calls to landing pads and combine them. 741 742 // Move eh.exception calls to landing pads. 743 Changed |= MoveExceptionValueCalls(); 744 745 Changed |= HandleURoRInvokes(); 746 747 LandingPads.clear(); 748 749 return Changed; 750 } 751