SjLjEHPrepare.cpp revision ca752c9020a1b1cf151142bd9e0cbca9af12d807
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/Transforms/Utils/BasicBlockUtils.h" 26#include "llvm/Transforms/Utils/Local.h" 27#include "llvm/ADT/Statistic.h" 28#include "llvm/ADT/SmallVector.h" 29#include "llvm/Support/CommandLine.h" 30#include "llvm/Support/Debug.h" 31#include "llvm/Support/raw_ostream.h" 32#include "llvm/Target/TargetLowering.h" 33using namespace llvm; 34 35STATISTIC(NumInvokes, "Number of invokes replaced"); 36STATISTIC(NumUnwinds, "Number of unwinds replaced"); 37STATISTIC(NumSpilled, "Number of registers live across unwind edges"); 38 39namespace { 40 class SjLjEHPass : public FunctionPass { 41 42 const TargetLowering *TLI; 43 44 const Type *FunctionContextTy; 45 Constant *RegisterFn; 46 Constant *UnregisterFn; 47 Constant *ResumeFn; 48 Constant *BuiltinSetjmpFn; 49 Constant *FrameAddrFn; 50 Constant *LSDAAddrFn; 51 Value *PersonalityFn; 52 Constant *SelectorFn; 53 Constant *ExceptionFn; 54 Constant *CallSiteFn; 55 56 Value *CallSite; 57 public: 58 static char ID; // Pass identification, replacement for typeid 59 explicit SjLjEHPass(const TargetLowering *tli = NULL) 60 : FunctionPass(&ID), TLI(tli) { } 61 bool doInitialization(Module &M); 62 bool runOnFunction(Function &F); 63 64 virtual void getAnalysisUsage(AnalysisUsage &AU) const { } 65 const char *getPassName() const { 66 return "SJLJ Exception Handling preparation"; 67 } 68 69 private: 70 void markInvokeCallSite(InvokeInst *II, unsigned InvokeNo, 71 Value *CallSite, 72 SwitchInst *CatchSwitch); 73 void splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes); 74 bool insertSjLjEHSupport(Function &F); 75 }; 76} // end anonymous namespace 77 78char SjLjEHPass::ID = 0; 79 80// Public Interface To the SjLjEHPass pass. 81FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) { 82 return new SjLjEHPass(TLI); 83} 84// doInitialization - Set up decalarations and types needed to process 85// exceptions. 86bool SjLjEHPass::doInitialization(Module &M) { 87 // Build the function context structure. 88 // builtin_setjmp uses a five word jbuf 89 const Type *VoidPtrTy = 90 Type::getInt8PtrTy(M.getContext()); 91 const Type *Int32Ty = Type::getInt32Ty(M.getContext()); 92 FunctionContextTy = 93 StructType::get(M.getContext(), 94 VoidPtrTy, // __prev 95 Int32Ty, // call_site 96 ArrayType::get(Int32Ty, 4), // __data 97 VoidPtrTy, // __personality 98 VoidPtrTy, // __lsda 99 ArrayType::get(VoidPtrTy, 5), // __jbuf 100 NULL); 101 RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register", 102 Type::getVoidTy(M.getContext()), 103 PointerType::getUnqual(FunctionContextTy), 104 (Type *)0); 105 UnregisterFn = 106 M.getOrInsertFunction("_Unwind_SjLj_Unregister", 107 Type::getVoidTy(M.getContext()), 108 PointerType::getUnqual(FunctionContextTy), 109 (Type *)0); 110 ResumeFn = 111 M.getOrInsertFunction("_Unwind_SjLj_Resume", 112 Type::getVoidTy(M.getContext()), 113 VoidPtrTy, 114 (Type *)0); 115 FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); 116 BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp); 117 LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); 118 SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector); 119 ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception); 120 CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); 121 PersonalityFn = 0; 122 123 return true; 124} 125 126/// markInvokeCallSite - Insert code to mark the call_site for this invoke 127void SjLjEHPass::markInvokeCallSite(InvokeInst *II, unsigned InvokeNo, 128 Value *CallSite, 129 SwitchInst *CatchSwitch) { 130 ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()), 131 InvokeNo); 132 // The runtime comes back to the dispatcher with the call_site - 1 in 133 // the context. Odd, but there it is. 134 ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()), 135 InvokeNo - 1); 136 137 // If the unwind edge has phi nodes, split the edge. 138 if (isa<PHINode>(II->getUnwindDest()->begin())) { 139 SplitCriticalEdge(II, 1, this); 140 141 // If there are any phi nodes left, they must have a single predecessor. 142 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) { 143 PN->replaceAllUsesWith(PN->getIncomingValue(0)); 144 PN->eraseFromParent(); 145 } 146 } 147 148 // Insert a store of the invoke num before the invoke 149 new StoreInst(CallSiteNoC, CallSite, true, II); // volatile 150 CallInst::Create(CallSiteFn, CallSiteNoC, "", II); 151 152 // Add a switch case to our unwind block. 153 CatchSwitch->addCase(SwitchValC, II->getUnwindDest()); 154 // We still want this to look like an invoke so we emit the LSDA properly, 155 // so we don't transform the invoke into a call here. 156} 157 158/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until 159/// we reach blocks we've already seen. 160static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) { 161 if (!LiveBBs.insert(BB).second) return; // already been here. 162 163 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 164 MarkBlocksLiveIn(*PI, LiveBBs); 165} 166 167/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge 168/// we spill into a stack location, guaranteeing that there is nothing live 169/// across the unwind edge. This process also splits all critical edges 170/// coming out of invoke's. 171void SjLjEHPass:: 172splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) { 173 // First step, split all critical edges from invoke instructions. 174 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 175 InvokeInst *II = Invokes[i]; 176 SplitCriticalEdge(II, 0, this); 177 SplitCriticalEdge(II, 1, this); 178 assert(!isa<PHINode>(II->getNormalDest()) && 179 !isa<PHINode>(II->getUnwindDest()) && 180 "critical edge splitting left single entry phi nodes?"); 181 } 182 183 Function *F = Invokes.back()->getParent()->getParent(); 184 185 // To avoid having to handle incoming arguments specially, we lower each arg 186 // to a copy instruction in the entry block. This ensures that the argument 187 // value itself cannot be live across the entry block. 188 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin(); 189 while (isa<AllocaInst>(AfterAllocaInsertPt) && 190 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize())) 191 ++AfterAllocaInsertPt; 192 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); 193 AI != E; ++AI) { 194 // This is always a no-op cast because we're casting AI to AI->getType() so 195 // src and destination types are identical. BitCast is the only possibility. 196 CastInst *NC = new BitCastInst( 197 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt); 198 AI->replaceAllUsesWith(NC); 199 // Normally its is forbidden to replace a CastInst's operand because it 200 // could cause the opcode to reflect an illegal conversion. However, we're 201 // replacing it here with the same value it was constructed with to simply 202 // make NC its user. 203 NC->setOperand(0, AI); 204 } 205 206 // Finally, scan the code looking for instructions with bad live ranges. 207 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 208 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { 209 // Ignore obvious cases we don't have to handle. In particular, most 210 // instructions either have no uses or only have a single use inside the 211 // current block. Ignore them quickly. 212 Instruction *Inst = II; 213 if (Inst->use_empty()) continue; 214 if (Inst->hasOneUse() && 215 cast<Instruction>(Inst->use_back())->getParent() == BB && 216 !isa<PHINode>(Inst->use_back())) continue; 217 218 // If this is an alloca in the entry block, it's not a real register 219 // value. 220 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) 221 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin()) 222 continue; 223 224 // Avoid iterator invalidation by copying users to a temporary vector. 225 SmallVector<Instruction*,16> Users; 226 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); 227 UI != E; ++UI) { 228 Instruction *User = cast<Instruction>(*UI); 229 if (User->getParent() != BB || isa<PHINode>(User)) 230 Users.push_back(User); 231 } 232 233 // Find all of the blocks that this value is live in. 234 std::set<BasicBlock*> LiveBBs; 235 LiveBBs.insert(Inst->getParent()); 236 while (!Users.empty()) { 237 Instruction *U = Users.back(); 238 Users.pop_back(); 239 240 if (!isa<PHINode>(U)) { 241 MarkBlocksLiveIn(U->getParent(), LiveBBs); 242 } else { 243 // Uses for a PHI node occur in their predecessor block. 244 PHINode *PN = cast<PHINode>(U); 245 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 246 if (PN->getIncomingValue(i) == Inst) 247 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); 248 } 249 } 250 251 // Now that we know all of the blocks that this thing is live in, see if 252 // it includes any of the unwind locations. 253 bool NeedsSpill = false; 254 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 255 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); 256 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { 257 NeedsSpill = true; 258 } 259 } 260 261 // If we decided we need a spill, do it. 262 if (NeedsSpill) { 263 ++NumSpilled; 264 DemoteRegToStack(*Inst, true); 265 } 266 } 267} 268 269bool SjLjEHPass::insertSjLjEHSupport(Function &F) { 270 SmallVector<ReturnInst*,16> Returns; 271 SmallVector<UnwindInst*,16> Unwinds; 272 SmallVector<InvokeInst*,16> Invokes; 273 274 // Look through the terminators of the basic blocks to find invokes, returns 275 // and unwinds 276 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 277 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { 278 // Remember all return instructions in case we insert an invoke into this 279 // function. 280 Returns.push_back(RI); 281 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { 282 Invokes.push_back(II); 283 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 284 Unwinds.push_back(UI); 285 } 286 // If we don't have any invokes or unwinds, there's nothing to do. 287 if (Unwinds.empty() && Invokes.empty()) return false; 288 289 // Find the eh.selector.* and eh.exception calls. We'll use the first 290 // eh.selector to determine the right personality function to use. For 291 // SJLJ, we always use the same personality for the whole function, 292 // not on a per-selector basis. 293 // FIXME: That's a bit ugly. Better way? 294 SmallVector<CallInst*,16> EH_Selectors; 295 SmallVector<CallInst*,16> EH_Exceptions; 296 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 297 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 298 if (CallInst *CI = dyn_cast<CallInst>(I)) { 299 if (CI->getCalledFunction() == SelectorFn) { 300 if (!PersonalityFn) PersonalityFn = CI->getOperand(2); 301 EH_Selectors.push_back(CI); 302 } else if (CI->getCalledFunction() == ExceptionFn) { 303 EH_Exceptions.push_back(CI); 304 } 305 } 306 } 307 } 308 // If we don't have any eh.selector calls, we can't determine the personality 309 // function. Without a personality function, we can't process exceptions. 310 if (!PersonalityFn) return false; 311 312 NumInvokes += Invokes.size(); 313 NumUnwinds += Unwinds.size(); 314 315 if (!Invokes.empty()) { 316 // We have invokes, so we need to add register/unregister calls to get 317 // this function onto the global unwind stack. 318 // 319 // First thing we need to do is scan the whole function for values that are 320 // live across unwind edges. Each value that is live across an unwind edge 321 // we spill into a stack location, guaranteeing that there is nothing live 322 // across the unwind edge. This process also splits all critical edges 323 // coming out of invoke's. 324 splitLiveRangesLiveAcrossInvokes(Invokes); 325 326 BasicBlock *EntryBB = F.begin(); 327 // Create an alloca for the incoming jump buffer ptr and the new jump buffer 328 // that needs to be restored on all exits from the function. This is an 329 // alloca because the value needs to be added to the global context list. 330 unsigned Align = 4; // FIXME: Should be a TLI check? 331 AllocaInst *FunctionContext = 332 new AllocaInst(FunctionContextTy, 0, Align, 333 "fcn_context", F.begin()->begin()); 334 335 Value *Idxs[2]; 336 const Type *Int32Ty = Type::getInt32Ty(F.getContext()); 337 Value *Zero = ConstantInt::get(Int32Ty, 0); 338 // We need to also keep around a reference to the call_site field 339 Idxs[0] = Zero; 340 Idxs[1] = ConstantInt::get(Int32Ty, 1); 341 CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 342 "call_site", 343 EntryBB->getTerminator()); 344 345 // The exception selector comes back in context->data[1] 346 Idxs[1] = ConstantInt::get(Int32Ty, 2); 347 Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 348 "fc_data", 349 EntryBB->getTerminator()); 350 Idxs[1] = ConstantInt::get(Int32Ty, 1); 351 Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2, 352 "exc_selector_gep", 353 EntryBB->getTerminator()); 354 // The exception value comes back in context->data[0] 355 Idxs[1] = Zero; 356 Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2, 357 "exception_gep", 358 EntryBB->getTerminator()); 359 360 // The result of the eh.selector call will be replaced with a 361 // a reference to the selector value returned in the function 362 // context. We leave the selector itself so the EH analysis later 363 // can use it. 364 for (int i = 0, e = EH_Selectors.size(); i < e; ++i) { 365 CallInst *I = EH_Selectors[i]; 366 Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I); 367 I->replaceAllUsesWith(SelectorVal); 368 } 369 // eh.exception calls are replaced with references to the proper 370 // location in the context. Unlike eh.selector, the eh.exception 371 // calls are removed entirely. 372 for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) { 373 CallInst *I = EH_Exceptions[i]; 374 // Possible for there to be duplicates, so check to make sure 375 // the instruction hasn't already been removed. 376 if (!I->getParent()) continue; 377 Value *Val = new LoadInst(ExceptionAddr, "exception", true, I); 378 const Type *Ty = Type::getInt8PtrTy(F.getContext()); 379 Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I); 380 381 I->replaceAllUsesWith(Val); 382 I->eraseFromParent(); 383 } 384 385 // The entry block changes to have the eh.sjlj.setjmp, with a conditional 386 // branch to a dispatch block for non-zero returns. If we return normally, 387 // we're not handling an exception and just register the function context 388 // and continue. 389 390 // Create the dispatch block. The dispatch block is basically a big switch 391 // statement that goes to all of the invoke landing pads. 392 BasicBlock *DispatchBlock = 393 BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F); 394 395 // Insert a load in the Catch block, and a switch on its value. By default, 396 // we go to a block that just does an unwind (which is the correct action 397 // for a standard call). 398 BasicBlock *UnwindBlock = 399 BasicBlock::Create(F.getContext(), "unwindbb", &F); 400 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock)); 401 402 Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true, 403 DispatchBlock); 404 SwitchInst *DispatchSwitch = 405 SwitchInst::Create(DispatchLoad, UnwindBlock, Invokes.size(), 406 DispatchBlock); 407 // Split the entry block to insert the conditional branch for the setjmp. 408 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(), 409 "eh.sjlj.setjmp.cont"); 410 411 // Populate the Function Context 412 // 1. LSDA address 413 // 2. Personality function address 414 // 3. jmpbuf (save FP and call eh.sjlj.setjmp) 415 416 // LSDA address 417 Idxs[0] = Zero; 418 Idxs[1] = ConstantInt::get(Int32Ty, 4); 419 Value *LSDAFieldPtr = 420 GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 421 "lsda_gep", 422 EntryBB->getTerminator()); 423 Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr", 424 EntryBB->getTerminator()); 425 new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator()); 426 427 Idxs[1] = ConstantInt::get(Int32Ty, 3); 428 Value *PersonalityFieldPtr = 429 GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 430 "lsda_gep", 431 EntryBB->getTerminator()); 432 new StoreInst(PersonalityFn, PersonalityFieldPtr, true, 433 EntryBB->getTerminator()); 434 435 // Save the frame pointer. 436 Idxs[1] = ConstantInt::get(Int32Ty, 5); 437 Value *FieldPtr 438 = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 439 "jbuf_gep", 440 EntryBB->getTerminator()); 441 Idxs[1] = ConstantInt::get(Int32Ty, 0); 442 Value *ElemPtr = 443 GetElementPtrInst::Create(FieldPtr, Idxs, Idxs+2, "jbuf_fp_gep", 444 EntryBB->getTerminator()); 445 446 Value *Val = CallInst::Create(FrameAddrFn, 447 ConstantInt::get(Int32Ty, 0), 448 "fp", 449 EntryBB->getTerminator()); 450 new StoreInst(Val, ElemPtr, true, EntryBB->getTerminator()); 451 // Call the setjmp instrinsic. It fills in the rest of the jmpbuf 452 Value *SetjmpArg = 453 CastInst::Create(Instruction::BitCast, FieldPtr, 454 Type::getInt8PtrTy(F.getContext()), "", 455 EntryBB->getTerminator()); 456 Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg, 457 "dispatch", 458 EntryBB->getTerminator()); 459 // check the return value of the setjmp. non-zero goes to dispatcher 460 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(), 461 ICmpInst::ICMP_EQ, DispatchVal, Zero, 462 "notunwind"); 463 // Nuke the uncond branch. 464 EntryBB->getTerminator()->eraseFromParent(); 465 466 // Put in a new condbranch in its place. 467 BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB); 468 469 // Register the function context and make sure it's known to not throw 470 CallInst *Register = 471 CallInst::Create(RegisterFn, FunctionContext, "", 472 ContBlock->getTerminator()); 473 Register->setDoesNotThrow(); 474 475 // At this point, we are all set up, update the invoke instructions 476 // to mark their call_site values, and fill in the dispatch switch 477 // accordingly. 478 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) 479 markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch); 480 481 // The front end has likely added calls to _Unwind_Resume. We need 482 // to find those calls and mark the call_site as -1 immediately prior. 483 // resume is a noreturn function, so any block that has a call to it 484 // should end in an 'unreachable' instruction with the call immediately 485 // prior. That's how we'll search. 486 // ??? There's got to be a better way. this is fugly. 487 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 488 if ((dyn_cast<UnreachableInst>(BB->getTerminator()))) { 489 BasicBlock::iterator I = BB->getTerminator(); 490 // Check the previous instruction and see if it's a resume call 491 if (I == BB->begin()) continue; 492 if (CallInst *CI = dyn_cast<CallInst>(--I)) { 493 if (CI->getCalledFunction() == ResumeFn) { 494 Value *NegativeOne = Constant::getAllOnesValue(Int32Ty); 495 new StoreInst(NegativeOne, CallSite, true, I); // volatile 496 } 497 } 498 } 499 500 // Replace all unwinds with a branch to the unwind handler. 501 // ??? Should this ever happen with sjlj exceptions? 502 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) { 503 BranchInst::Create(UnwindBlock, Unwinds[i]); 504 Unwinds[i]->eraseFromParent(); 505 } 506 507 // Finally, for any returns from this function, if this function contains an 508 // invoke, add a call to unregister the function context. 509 for (unsigned i = 0, e = Returns.size(); i != e; ++i) 510 CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]); 511 } 512 513 return true; 514} 515 516bool SjLjEHPass::runOnFunction(Function &F) { 517 bool Res = insertSjLjEHSupport(F); 518 return Res; 519} 520