SjLjEHPrepare.cpp revision 6ef94175d1bbab95f195770bb3c559b3ab38c4e5
1//===- SjLjEHPass.cpp - Eliminate Invoke & Unwind instructions -----------===// 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 transformation is designed for use by code generators which use SjLj 11// based exception handling. 12// 13//===----------------------------------------------------------------------===// 14 15#define DEBUG_TYPE "sjljehprepare" 16#include "llvm/Transforms/Scalar.h" 17#include "llvm/Constants.h" 18#include "llvm/DerivedTypes.h" 19#include "llvm/Instructions.h" 20#include "llvm/Intrinsics.h" 21#include "llvm/LLVMContext.h" 22#include "llvm/Module.h" 23#include "llvm/Pass.h" 24#include "llvm/CodeGen/Passes.h" 25#include "llvm/Target/TargetData.h" 26#include "llvm/Target/TargetLowering.h" 27#include "llvm/Transforms/Utils/BasicBlockUtils.h" 28#include "llvm/Transforms/Utils/Local.h" 29#include "llvm/Support/CommandLine.h" 30#include "llvm/Support/Debug.h" 31#include "llvm/Support/IRBuilder.h" 32#include "llvm/ADT/DenseMap.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/ADT/Statistic.h" 35#include <set> 36using namespace llvm; 37 38static cl::opt<bool> DisableOldSjLjEH("disable-old-sjlj-eh", cl::Hidden, 39 cl::desc("Disable the old SjLj EH preparation pass")); 40 41STATISTIC(NumInvokes, "Number of invokes replaced"); 42STATISTIC(NumUnwinds, "Number of unwinds replaced"); 43STATISTIC(NumSpilled, "Number of registers live across unwind edges"); 44 45namespace { 46 class SjLjEHPass : public FunctionPass { 47 const TargetLowering *TLI; 48 Type *FunctionContextTy; 49 Constant *RegisterFn; 50 Constant *UnregisterFn; 51 Constant *BuiltinSetjmpFn; 52 Constant *FrameAddrFn; 53 Constant *StackAddrFn; 54 Constant *StackRestoreFn; 55 Constant *LSDAAddrFn; 56 Value *PersonalityFn; 57 Constant *SelectorFn; 58 Constant *ExceptionFn; 59 Constant *CallSiteFn; 60 Constant *DispatchSetupFn; 61 Value *CallSite; 62 DenseMap<InvokeInst*, BasicBlock*> LPadSuccMap; 63 public: 64 static char ID; // Pass identification, replacement for typeid 65 explicit SjLjEHPass(const TargetLowering *tli = NULL) 66 : FunctionPass(ID), TLI(tli) { } 67 bool doInitialization(Module &M); 68 bool runOnFunction(Function &F); 69 70 virtual void getAnalysisUsage(AnalysisUsage &AU) const {} 71 const char *getPassName() const { 72 return "SJLJ Exception Handling preparation"; 73 } 74 75 private: 76 bool setupEntryBlockAndCallSites(Function &F); 77 void setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads); 78 79 void insertCallSiteStore(Instruction *I, int Number, Value *CallSite); 80 void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite, 81 SwitchInst *CatchSwitch); 82 void splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes); 83 void splitLandingPad(InvokeInst *II); 84 bool insertSjLjEHSupport(Function &F); 85 }; 86} // end anonymous namespace 87 88char SjLjEHPass::ID = 0; 89 90// Public Interface To the SjLjEHPass pass. 91FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) { 92 return new SjLjEHPass(TLI); 93} 94// doInitialization - Set up decalarations and types needed to process 95// exceptions. 96bool SjLjEHPass::doInitialization(Module &M) { 97 // Build the function context structure. 98 // builtin_setjmp uses a five word jbuf 99 Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext()); 100 Type *Int32Ty = Type::getInt32Ty(M.getContext()); 101 FunctionContextTy = 102 StructType::get(VoidPtrTy, // __prev 103 Int32Ty, // call_site 104 ArrayType::get(Int32Ty, 4), // __data 105 VoidPtrTy, // __personality 106 VoidPtrTy, // __lsda 107 ArrayType::get(VoidPtrTy, 5), // __jbuf 108 NULL); 109 RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register", 110 Type::getVoidTy(M.getContext()), 111 PointerType::getUnqual(FunctionContextTy), 112 (Type *)0); 113 UnregisterFn = 114 M.getOrInsertFunction("_Unwind_SjLj_Unregister", 115 Type::getVoidTy(M.getContext()), 116 PointerType::getUnqual(FunctionContextTy), 117 (Type *)0); 118 FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); 119 StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave); 120 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore); 121 BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp); 122 LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); 123 SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector); 124 ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception); 125 CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); 126 DispatchSetupFn 127 = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_dispatch_setup); 128 PersonalityFn = 0; 129 130 return true; 131} 132 133/// insertCallSiteStore - Insert a store of the call-site value to the 134/// function context 135void SjLjEHPass::insertCallSiteStore(Instruction *I, int Number, 136 Value *CallSite) { 137 ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()), 138 Number); 139 // Insert a store of the call-site number 140 new StoreInst(CallSiteNoC, CallSite, true, I); // volatile 141} 142 143/// splitLandingPad - Split a landing pad. This takes considerable care because 144/// of PHIs and other nasties. The problem is that the jump table needs to jump 145/// to the landing pad block. However, the landing pad block can be jumped to 146/// only by an invoke instruction. So we clone the landingpad instruction into 147/// its own basic block, have the invoke jump to there. The landingpad 148/// instruction's basic block's successor is now the target for the jump table. 149/// 150/// But because of PHI nodes, we need to create another basic block for the jump 151/// table to jump to. This is definitely a hack, because the values for the PHI 152/// nodes may not be defined on the edge from the jump table. But that's okay, 153/// because the jump table is simply a construct to mimic what is happening in 154/// the CFG. So the values are mysteriously there, even though there is no value 155/// for the PHI from the jump table's edge (hence calling this a hack). 156void SjLjEHPass::splitLandingPad(InvokeInst *II) { 157 SmallVector<BasicBlock*, 2> NewBBs; 158 SplitLandingPadPredecessors(II->getUnwindDest(), II->getParent(), 159 ".1", ".2", this, NewBBs); 160 161 // Create an empty block so that the jump table has something to jump to 162 // which doesn't have any PHI nodes. 163 BasicBlock *LPad = NewBBs[0]; 164 BasicBlock *Succ = *succ_begin(LPad); 165 BasicBlock *JumpTo = BasicBlock::Create(II->getContext(), "jt.land", 166 LPad->getParent(), Succ); 167 LPad->getTerminator()->eraseFromParent(); 168 BranchInst::Create(JumpTo, LPad); 169 BranchInst::Create(Succ, JumpTo); 170 LPadSuccMap[II] = JumpTo; 171 172 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { 173 PHINode *PN = cast<PHINode>(I); 174 Value *Val = PN->removeIncomingValue(LPad, false); 175 PN->addIncoming(Val, JumpTo); 176 } 177} 178 179/// markInvokeCallSite - Insert code to mark the call_site for this invoke 180void SjLjEHPass::markInvokeCallSite(InvokeInst *II, int InvokeNo, 181 Value *CallSite, 182 SwitchInst *CatchSwitch) { 183 ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()), 184 InvokeNo); 185 // The runtime comes back to the dispatcher with the call_site - 1 in 186 // the context. Odd, but there it is. 187 ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()), 188 InvokeNo - 1); 189 190 // If the unwind edge has phi nodes, split the edge. 191 if (isa<PHINode>(II->getUnwindDest()->begin())) { 192 // FIXME: New EH - This if-condition will be always true in the new scheme. 193 if (II->getUnwindDest()->isLandingPad()) 194 splitLandingPad(II); 195 else 196 SplitCriticalEdge(II, 1, this); 197 198 // If there are any phi nodes left, they must have a single predecessor. 199 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) { 200 PN->replaceAllUsesWith(PN->getIncomingValue(0)); 201 PN->eraseFromParent(); 202 } 203 } 204 205 // Insert the store of the call site value 206 insertCallSiteStore(II, InvokeNo, CallSite); 207 208 // Record the call site value for the back end so it stays associated with 209 // the invoke. 210 CallInst::Create(CallSiteFn, CallSiteNoC, "", II); 211 212 // Add a switch case to our unwind block. 213 if (BasicBlock *SuccBB = LPadSuccMap[II]) { 214 CatchSwitch->addCase(SwitchValC, SuccBB); 215 } else { 216 CatchSwitch->addCase(SwitchValC, II->getUnwindDest()); 217 } 218 219 // We still want this to look like an invoke so we emit the LSDA properly, 220 // so we don't transform the invoke into a call here. 221} 222 223/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until 224/// we reach blocks we've already seen. 225static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) { 226 if (!LiveBBs.insert(BB).second) return; // already been here. 227 228 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 229 MarkBlocksLiveIn(*PI, LiveBBs); 230} 231 232/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge 233/// we spill into a stack location, guaranteeing that there is nothing live 234/// across the unwind edge. This process also splits all critical edges 235/// coming out of invoke's. 236/// FIXME: Move this function to a common utility file (Local.cpp?) so 237/// both SjLj and LowerInvoke can use it. 238void SjLjEHPass:: 239splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) { 240 // First step, split all critical edges from invoke instructions. 241 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 242 InvokeInst *II = Invokes[i]; 243 SplitCriticalEdge(II, 0, this); 244 245 // FIXME: New EH - This if-condition will be always true in the new scheme. 246 if (II->getUnwindDest()->isLandingPad()) 247 splitLandingPad(II); 248 else 249 SplitCriticalEdge(II, 1, this); 250 251 assert(!isa<PHINode>(II->getNormalDest()) && 252 !isa<PHINode>(II->getUnwindDest()) && 253 "Critical edge splitting left single entry phi nodes?"); 254 } 255 256 Function *F = Invokes.back()->getParent()->getParent(); 257 258 // To avoid having to handle incoming arguments specially, we lower each arg 259 // to a copy instruction in the entry block. This ensures that the argument 260 // value itself cannot be live across the entry block. 261 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin(); 262 while (isa<AllocaInst>(AfterAllocaInsertPt) && 263 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize())) 264 ++AfterAllocaInsertPt; 265 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); 266 AI != E; ++AI) { 267 Type *Ty = AI->getType(); 268 // Aggregate types can't be cast, but are legal argument types, so we have 269 // to handle them differently. We use an extract/insert pair as a 270 // lightweight method to achieve the same goal. 271 if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) { 272 Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt); 273 Instruction *NI = InsertValueInst::Create(AI, EI, 0); 274 NI->insertAfter(EI); 275 AI->replaceAllUsesWith(NI); 276 // Set the operand of the instructions back to the AllocaInst. 277 EI->setOperand(0, AI); 278 NI->setOperand(0, AI); 279 } else { 280 // This is always a no-op cast because we're casting AI to AI->getType() 281 // so src and destination types are identical. BitCast is the only 282 // possibility. 283 CastInst *NC = new BitCastInst( 284 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt); 285 AI->replaceAllUsesWith(NC); 286 // Set the operand of the cast instruction back to the AllocaInst. 287 // Normally it's forbidden to replace a CastInst's operand because it 288 // could cause the opcode to reflect an illegal conversion. However, 289 // we're replacing it here with the same value it was constructed with. 290 // We do this because the above replaceAllUsesWith() clobbered the 291 // operand, but we want this one to remain. 292 NC->setOperand(0, AI); 293 } 294 } 295 296 // Finally, scan the code looking for instructions with bad live ranges. 297 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 298 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { 299 // Ignore obvious cases we don't have to handle. In particular, most 300 // instructions either have no uses or only have a single use inside the 301 // current block. Ignore them quickly. 302 Instruction *Inst = II; 303 if (Inst->use_empty()) continue; 304 if (Inst->hasOneUse() && 305 cast<Instruction>(Inst->use_back())->getParent() == BB && 306 !isa<PHINode>(Inst->use_back())) continue; 307 308 // If this is an alloca in the entry block, it's not a real register 309 // value. 310 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) 311 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin()) 312 continue; 313 314 // Avoid iterator invalidation by copying users to a temporary vector. 315 SmallVector<Instruction*,16> Users; 316 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); 317 UI != E; ++UI) { 318 Instruction *User = cast<Instruction>(*UI); 319 if (User->getParent() != BB || isa<PHINode>(User)) 320 Users.push_back(User); 321 } 322 323 // Find all of the blocks that this value is live in. 324 std::set<BasicBlock*> LiveBBs; 325 LiveBBs.insert(Inst->getParent()); 326 while (!Users.empty()) { 327 Instruction *U = Users.back(); 328 Users.pop_back(); 329 330 if (!isa<PHINode>(U)) { 331 MarkBlocksLiveIn(U->getParent(), LiveBBs); 332 } else { 333 // Uses for a PHI node occur in their predecessor block. 334 PHINode *PN = cast<PHINode>(U); 335 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 336 if (PN->getIncomingValue(i) == Inst) 337 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); 338 } 339 } 340 341 // Now that we know all of the blocks that this thing is live in, see if 342 // it includes any of the unwind locations. 343 bool NeedsSpill = false; 344 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 345 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); 346 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { 347 NeedsSpill = true; 348 } 349 } 350 351 // If we decided we need a spill, do it. 352 // FIXME: Spilling this way is overkill, as it forces all uses of 353 // the value to be reloaded from the stack slot, even those that aren't 354 // in the unwind blocks. We should be more selective. 355 if (NeedsSpill) { 356 ++NumSpilled; 357 DemoteRegToStack(*Inst, true); 358 } 359 } 360} 361 362/// CreateLandingPadLoad - Load the exception handling values and insert them 363/// into a structure. 364static Instruction *CreateLandingPadLoad(Function &F, Value *ExnAddr, 365 Value *SelAddr, 366 BasicBlock::iterator InsertPt) { 367 Value *Exn = new LoadInst(ExnAddr, "exn", false, 368 InsertPt); 369 Type *Ty = Type::getInt8PtrTy(F.getContext()); 370 Exn = CastInst::Create(Instruction::IntToPtr, Exn, Ty, "", InsertPt); 371 Value *Sel = new LoadInst(SelAddr, "sel", false, InsertPt); 372 373 Ty = StructType::get(Exn->getType(), Sel->getType(), NULL); 374 InsertValueInst *LPadVal = InsertValueInst::Create(llvm::UndefValue::get(Ty), 375 Exn, 0, 376 "lpad.val", InsertPt); 377 return InsertValueInst::Create(LPadVal, Sel, 1, "lpad.val", InsertPt); 378} 379 380/// ReplaceLandingPadVal - Replace the landingpad instruction's value with a 381/// load from the stored values (via CreateLandingPadLoad). This looks through 382/// PHI nodes, and removes them if they are dead. 383static void ReplaceLandingPadVal(Function &F, Instruction *Inst, Value *ExnAddr, 384 Value *SelAddr) { 385 if (Inst->use_empty()) return; 386 387 while (!Inst->use_empty()) { 388 Instruction *I = cast<Instruction>(Inst->use_back()); 389 390 if (PHINode *PN = dyn_cast<PHINode>(I)) { 391 ReplaceLandingPadVal(F, PN, ExnAddr, SelAddr); 392 if (PN->use_empty()) PN->eraseFromParent(); 393 continue; 394 } 395 396 I->replaceUsesOfWith(Inst, CreateLandingPadLoad(F, ExnAddr, SelAddr, I)); 397 } 398} 399 400bool SjLjEHPass::insertSjLjEHSupport(Function &F) { 401 SmallVector<ReturnInst*,16> Returns; 402 SmallVector<UnwindInst*,16> Unwinds; 403 SmallVector<InvokeInst*,16> Invokes; 404 405 // Look through the terminators of the basic blocks to find invokes, returns 406 // and unwinds. 407 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 408 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { 409 // Remember all return instructions in case we insert an invoke into this 410 // function. 411 Returns.push_back(RI); 412 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { 413 Invokes.push_back(II); 414 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 415 Unwinds.push_back(UI); 416 } 417 } 418 419 NumInvokes += Invokes.size(); 420 NumUnwinds += Unwinds.size(); 421 422 // If we don't have any invokes, there's nothing to do. 423 if (Invokes.empty()) return false; 424 425 // Find the eh.selector.*, eh.exception and alloca calls. 426 // 427 // Remember any allocas() that aren't in the entry block, as the 428 // jmpbuf saved SP will need to be updated for them. 429 // 430 // We'll use the first eh.selector to determine the right personality 431 // function to use. For SJLJ, we always use the same personality for the 432 // whole function, not on a per-selector basis. 433 // FIXME: That's a bit ugly. Better way? 434 SmallVector<CallInst*,16> EH_Selectors; 435 SmallVector<CallInst*,16> EH_Exceptions; 436 SmallVector<Instruction*,16> JmpbufUpdatePoints; 437 438 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 439 // Note: Skip the entry block since there's nothing there that interests 440 // us. eh.selector and eh.exception shouldn't ever be there, and we 441 // want to disregard any allocas that are there. 442 // 443 // FIXME: This is awkward. The new EH scheme won't need to skip the entry 444 // block. 445 if (BB == F.begin()) { 446 if (InvokeInst *II = dyn_cast<InvokeInst>(F.begin()->getTerminator())) { 447 // FIXME: This will be always non-NULL in the new EH. 448 if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) 449 if (!PersonalityFn) PersonalityFn = LPI->getPersonalityFn(); 450 } 451 452 continue; 453 } 454 455 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 456 if (CallInst *CI = dyn_cast<CallInst>(I)) { 457 if (CI->getCalledFunction() == SelectorFn) { 458 if (!PersonalityFn) PersonalityFn = CI->getArgOperand(1); 459 EH_Selectors.push_back(CI); 460 } else if (CI->getCalledFunction() == ExceptionFn) { 461 EH_Exceptions.push_back(CI); 462 } else if (CI->getCalledFunction() == StackRestoreFn) { 463 JmpbufUpdatePoints.push_back(CI); 464 } 465 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) { 466 JmpbufUpdatePoints.push_back(AI); 467 } else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) { 468 // FIXME: This will be always non-NULL in the new EH. 469 if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) 470 if (!PersonalityFn) PersonalityFn = LPI->getPersonalityFn(); 471 } 472 } 473 } 474 475 // If we don't have any eh.selector calls, we can't determine the personality 476 // function. Without a personality function, we can't process exceptions. 477 if (!PersonalityFn) return false; 478 479 // We have invokes, so we need to add register/unregister calls to get this 480 // function onto the global unwind stack. 481 // 482 // First thing we need to do is scan the whole function for values that are 483 // live across unwind edges. Each value that is live across an unwind edge we 484 // spill into a stack location, guaranteeing that there is nothing live across 485 // the unwind edge. This process also splits all critical edges coming out of 486 // invoke's. 487 splitLiveRangesAcrossInvokes(Invokes); 488 489 490 SmallVector<LandingPadInst*, 16> LandingPads; 491 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 492 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) 493 // FIXME: This will be always non-NULL in the new EH. 494 if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) 495 LandingPads.push_back(LPI); 496 } 497 498 499 BasicBlock *EntryBB = F.begin(); 500 // Create an alloca for the incoming jump buffer ptr and the new jump buffer 501 // that needs to be restored on all exits from the function. This is an 502 // alloca because the value needs to be added to the global context list. 503 unsigned Align = 4; // FIXME: Should be a TLI check? 504 AllocaInst *FunctionContext = 505 new AllocaInst(FunctionContextTy, 0, Align, 506 "fcn_context", F.begin()->begin()); 507 508 Value *Idxs[2]; 509 Type *Int32Ty = Type::getInt32Ty(F.getContext()); 510 Value *Zero = ConstantInt::get(Int32Ty, 0); 511 // We need to also keep around a reference to the call_site field 512 Idxs[0] = Zero; 513 Idxs[1] = ConstantInt::get(Int32Ty, 1); 514 CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, "call_site", 515 EntryBB->getTerminator()); 516 517 // The exception selector comes back in context->data[1] 518 Idxs[1] = ConstantInt::get(Int32Ty, 2); 519 Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, "fc_data", 520 EntryBB->getTerminator()); 521 Idxs[1] = ConstantInt::get(Int32Ty, 1); 522 Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, 523 "exc_selector_gep", 524 EntryBB->getTerminator()); 525 // The exception value comes back in context->data[0] 526 Idxs[1] = Zero; 527 Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, 528 "exception_gep", 529 EntryBB->getTerminator()); 530 531 // The result of the eh.selector call will be replaced with a a reference to 532 // the selector value returned in the function context. We leave the selector 533 // itself so the EH analysis later can use it. 534 for (int i = 0, e = EH_Selectors.size(); i < e; ++i) { 535 CallInst *I = EH_Selectors[i]; 536 Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I); 537 I->replaceAllUsesWith(SelectorVal); 538 } 539 540 // eh.exception calls are replaced with references to the proper location in 541 // the context. Unlike eh.selector, the eh.exception calls are removed 542 // entirely. 543 for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) { 544 CallInst *I = EH_Exceptions[i]; 545 // Possible for there to be duplicates, so check to make sure the 546 // instruction hasn't already been removed. 547 if (!I->getParent()) continue; 548 Value *Val = new LoadInst(ExceptionAddr, "exception", true, I); 549 Type *Ty = Type::getInt8PtrTy(F.getContext()); 550 Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I); 551 552 I->replaceAllUsesWith(Val); 553 I->eraseFromParent(); 554 } 555 556 for (unsigned i = 0, e = LandingPads.size(); i != e; ++i) 557 ReplaceLandingPadVal(F, LandingPads[i], ExceptionAddr, SelectorAddr); 558 559 // The entry block changes to have the eh.sjlj.setjmp, with a conditional 560 // branch to a dispatch block for non-zero returns. If we return normally, 561 // we're not handling an exception and just register the function context and 562 // continue. 563 564 // Create the dispatch block. The dispatch block is basically a big switch 565 // statement that goes to all of the invoke landing pads. 566 BasicBlock *DispatchBlock = 567 BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F); 568 569 // Insert a load of the callsite in the dispatch block, and a switch on its 570 // value. By default, we issue a trap statement. 571 BasicBlock *TrapBlock = 572 BasicBlock::Create(F.getContext(), "trapbb", &F); 573 CallInst::Create(Intrinsic::getDeclaration(F.getParent(), Intrinsic::trap), 574 "", TrapBlock); 575 new UnreachableInst(F.getContext(), TrapBlock); 576 577 Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true, 578 DispatchBlock); 579 SwitchInst *DispatchSwitch = 580 SwitchInst::Create(DispatchLoad, TrapBlock, Invokes.size(), 581 DispatchBlock); 582 // Split the entry block to insert the conditional branch for the setjmp. 583 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(), 584 "eh.sjlj.setjmp.cont"); 585 586 // Populate the Function Context 587 // 1. LSDA address 588 // 2. Personality function address 589 // 3. jmpbuf (save SP, FP and call eh.sjlj.setjmp) 590 591 // LSDA address 592 Idxs[0] = Zero; 593 Idxs[1] = ConstantInt::get(Int32Ty, 4); 594 Value *LSDAFieldPtr = 595 GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep", 596 EntryBB->getTerminator()); 597 Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr", 598 EntryBB->getTerminator()); 599 new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator()); 600 601 Idxs[1] = ConstantInt::get(Int32Ty, 3); 602 Value *PersonalityFieldPtr = 603 GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep", 604 EntryBB->getTerminator()); 605 new StoreInst(PersonalityFn, PersonalityFieldPtr, true, 606 EntryBB->getTerminator()); 607 608 // Save the frame pointer. 609 Idxs[1] = ConstantInt::get(Int32Ty, 5); 610 Value *JBufPtr 611 = GetElementPtrInst::Create(FunctionContext, Idxs, "jbuf_gep", 612 EntryBB->getTerminator()); 613 Idxs[1] = ConstantInt::get(Int32Ty, 0); 614 Value *FramePtr = 615 GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep", 616 EntryBB->getTerminator()); 617 618 Value *Val = CallInst::Create(FrameAddrFn, 619 ConstantInt::get(Int32Ty, 0), 620 "fp", 621 EntryBB->getTerminator()); 622 new StoreInst(Val, FramePtr, true, EntryBB->getTerminator()); 623 624 // Save the stack pointer. 625 Idxs[1] = ConstantInt::get(Int32Ty, 2); 626 Value *StackPtr = 627 GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep", 628 EntryBB->getTerminator()); 629 630 Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator()); 631 new StoreInst(Val, StackPtr, true, EntryBB->getTerminator()); 632 633 // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. 634 Value *SetjmpArg = 635 CastInst::Create(Instruction::BitCast, JBufPtr, 636 Type::getInt8PtrTy(F.getContext()), "", 637 EntryBB->getTerminator()); 638 Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg, 639 "dispatch", 640 EntryBB->getTerminator()); 641 642 // Add a call to dispatch_setup after the setjmp call. This is expanded to any 643 // target-specific setup that needs to be done. 644 CallInst::Create(DispatchSetupFn, DispatchVal, "", EntryBB->getTerminator()); 645 646 // check the return value of the setjmp. non-zero goes to dispatcher. 647 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(), 648 ICmpInst::ICMP_EQ, DispatchVal, Zero, 649 "notunwind"); 650 // Nuke the uncond branch. 651 EntryBB->getTerminator()->eraseFromParent(); 652 653 // Put in a new condbranch in its place. 654 BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB); 655 656 // Register the function context and make sure it's known to not throw 657 CallInst *Register = 658 CallInst::Create(RegisterFn, FunctionContext, "", 659 ContBlock->getTerminator()); 660 Register->setDoesNotThrow(); 661 662 // At this point, we are all set up, update the invoke instructions to mark 663 // their call_site values, and fill in the dispatch switch accordingly. 664 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) 665 markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch); 666 667 // Mark call instructions that aren't nounwind as no-action (call_site == 668 // -1). Skip the entry block, as prior to then, no function context has been 669 // created for this function and any unexpected exceptions thrown will go 670 // directly to the caller's context, which is what we want anyway, so no need 671 // to do anything here. 672 for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) { 673 for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I) 674 if (CallInst *CI = dyn_cast<CallInst>(I)) { 675 // Ignore calls to the EH builtins (eh.selector, eh.exception) 676 Constant *Callee = CI->getCalledFunction(); 677 if (Callee != SelectorFn && Callee != ExceptionFn 678 && !CI->doesNotThrow()) 679 insertCallSiteStore(CI, -1, CallSite); 680 } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) { 681 insertCallSiteStore(RI, -1, CallSite); 682 } 683 } 684 685 // Replace all unwinds with a branch to the unwind handler. 686 // ??? Should this ever happen with sjlj exceptions? 687 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) { 688 BranchInst::Create(TrapBlock, Unwinds[i]); 689 Unwinds[i]->eraseFromParent(); 690 } 691 692 // Following any allocas not in the entry block, update the saved SP in the 693 // jmpbuf to the new value. 694 for (unsigned i = 0, e = JmpbufUpdatePoints.size(); i != e; ++i) { 695 Instruction *AI = JmpbufUpdatePoints[i]; 696 Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp"); 697 StackAddr->insertAfter(AI); 698 Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true); 699 StoreStackAddr->insertAfter(StackAddr); 700 } 701 702 // Finally, for any returns from this function, if this function contains an 703 // invoke, add a call to unregister the function context. 704 for (unsigned i = 0, e = Returns.size(); i != e; ++i) 705 CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]); 706 707 return true; 708} 709 710/// setupFunctionContext - Allocate the function context on the stack and fill 711/// it with all of the data that we know at this point. 712void SjLjEHPass::setupFunctionContext(Function &F, 713 ArrayRef<LandingPadInst*> LPads) { 714 BasicBlock *EntryBB = F.begin(); 715 716 // Create an alloca for the incoming jump buffer ptr and the new jump buffer 717 // that needs to be restored on all exits from the function. This is an alloca 718 // because the value needs to be added to the global context list. 719 unsigned Align = 720 TLI->getTargetData()->getPrefTypeAlignment(FunctionContextTy); 721 AllocaInst *FuncCtx = 722 new AllocaInst(FunctionContextTy, 0, Align, "fn_context", EntryBB->begin()); 723 724 // Store a pointer to the function context so that the back-end will know 725 // where to look for it. 726 CallInst::Create(Intrinsic::getDeclaration(F.getParent(), 727 Intrinsic::eh_sjlj_functioncontext), 728 FuncCtx, "", EntryBB->getTerminator()); 729 730 // Fill in the function context structure. 731 Value *Idxs[2]; 732 Type *Int32Ty = Type::getInt32Ty(F.getContext()); 733 Value *Zero = ConstantInt::get(Int32Ty, 0); 734 Value *One = ConstantInt::get(Int32Ty, 1); 735 736 // Keep around a reference to the call_site field. 737 Idxs[0] = Zero; 738 Idxs[1] = One; 739 CallSite = GetElementPtrInst::Create(FuncCtx, Idxs, "call_site", 740 EntryBB->getTerminator()); 741 742 // Reference the __data field. 743 Idxs[1] = ConstantInt::get(Int32Ty, 2); 744 Value *FCData = GetElementPtrInst::Create(FuncCtx, Idxs, "__data", 745 EntryBB->getTerminator()); 746 747 // The exception value comes back in context->__data[0]. 748 Idxs[1] = Zero; 749 Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, 750 "exception_gep", 751 EntryBB->getTerminator()); 752 753 // The exception selector comes back in context->__data[1]. 754 Idxs[1] = One; 755 Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, 756 "exn_selector_gep", 757 EntryBB->getTerminator()); 758 759 for (unsigned I = 0, E = LPads.size(); I != E; ++I) { 760 LandingPadInst *LPI = LPads[I]; 761 IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt()); 762 763 Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val"); 764 ExnVal = Builder.CreateIntToPtr(ExnVal, Type::getInt8PtrTy(F.getContext())); 765 Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val"); 766 767 Type *LPadType = LPI->getType(); 768 Value *LPadVal = UndefValue::get(LPadType); 769 LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val"); 770 LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val"); 771 772 LPI->replaceAllUsesWith(LPadVal); 773 } 774 775 // Personality function 776 Idxs[1] = ConstantInt::get(Int32Ty, 3); 777 if (!PersonalityFn) 778 PersonalityFn = LPads[0]->getPersonalityFn(); 779 Value *PersonalityFieldPtr = 780 GetElementPtrInst::Create(FuncCtx, Idxs, "pers_fn_gep", 781 EntryBB->getTerminator()); 782 new StoreInst(PersonalityFn, PersonalityFieldPtr, true, 783 EntryBB->getTerminator()); 784 785 // LSDA address 786 Idxs[1] = ConstantInt::get(Int32Ty, 4); 787 Value *LSDAFieldPtr = 788 GetElementPtrInst::Create(FuncCtx, Idxs, "lsda_gep", 789 EntryBB->getTerminator()); 790 Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr", 791 EntryBB->getTerminator()); 792 new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator()); 793 794 // Get a reference to the jump buffer. 795 Idxs[1] = ConstantInt::get(Int32Ty, 5); 796 Value *JBufPtr = 797 GetElementPtrInst::Create(FuncCtx, Idxs, "jbuf_gep", 798 EntryBB->getTerminator()); 799 Idxs[1] = Zero; 800 Value *FramePtr = 801 GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep", 802 EntryBB->getTerminator()); 803 804 // Save the frame pointer. 805 Value *Val = CallInst::Create(FrameAddrFn, 806 ConstantInt::get(Int32Ty, 0), 807 "fp", 808 EntryBB->getTerminator()); 809 new StoreInst(Val, FramePtr, true, EntryBB->getTerminator()); 810 811 // Save the stack pointer. 812 Idxs[1] = ConstantInt::get(Int32Ty, 2); 813 Value *StackPtr = 814 GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep", 815 EntryBB->getTerminator()); 816 817 Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator()); 818 new StoreInst(Val, StackPtr, true, EntryBB->getTerminator()); 819 820 // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. 821 Value *SetjmpArg = 822 CastInst::Create(Instruction::BitCast, JBufPtr, 823 Type::getInt8PtrTy(F.getContext()), "", 824 EntryBB->getTerminator()); 825 Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg, 826 "dispatch", 827 EntryBB->getTerminator()); 828 829 // Add a call to dispatch_setup after the setjmp call. This is expanded to any 830 // target-specific setup that needs to be done. 831 CallInst::Create(DispatchSetupFn, DispatchVal, "", EntryBB->getTerminator()); 832} 833 834/// setupEntryBlockAndCallSites - Setup the entry block by creating and filling 835/// the function context and marking the call sites with the appropriate 836/// values. These values are used by the DWARF EH emitter. 837bool SjLjEHPass::setupEntryBlockAndCallSites(Function &F) { 838 SmallVector<InvokeInst*, 16> Invokes; 839 SmallVector<LandingPadInst*, 16> LPads; 840 841 // Look through the terminators of the basic blocks to find invokes. 842 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 843 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { 844 Invokes.push_back(II); 845 LPads.push_back(II->getUnwindDest()->getLandingPadInst()); 846 } 847 848 if (Invokes.empty()) return false; 849 850 setupFunctionContext(F, LPads); 851 852 // At this point, we are all set up, update the invoke instructions to mark 853 // their call_site values, and fill in the dispatch switch accordingly. 854 for (unsigned I = 0, E = Invokes.size(); I != E; ++I) { 855 insertCallSiteStore(Invokes[I], I + 1, CallSite); 856 857 ConstantInt *CallSiteNum = 858 ConstantInt::get(Type::getInt32Ty(F.getContext()), I + 1); 859 860 // Record the call site value for the back end so it stays associated with 861 // the invoke. 862 CallInst::Create(CallSiteFn, CallSiteNum, "", Invokes[I]); 863 } 864 865 // Mark call instructions that aren't nounwind as no-action (call_site == 866 // -1). Skip the entry block, as prior to then, no function context has been 867 // created for this function and any unexpected exceptions thrown will go 868 // directly to the caller's context, which is what we want anyway, so no need 869 // to do anything here. 870 for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) { 871 for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I) 872 if (CallInst *CI = dyn_cast<CallInst>(I)) { 873 if (!CI->doesNotThrow()) 874 insertCallSiteStore(CI, -1, CallSite); 875 } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) { 876 insertCallSiteStore(RI, -1, CallSite); 877 } 878 } 879 880 return true; 881} 882 883bool SjLjEHPass::runOnFunction(Function &F) { 884 bool Res = false; 885 if (!DisableOldSjLjEH) 886 Res = insertSjLjEHSupport(F); 887 else 888 Res = setupEntryBlockAndCallSites(F); 889 return Res; 890} 891