SjLjEHPrepare.cpp revision 0a9b7e23d54e15a4fd57dac39e40252db1546245
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/Compiler.h" 31#include "llvm/Support/Debug.h" 32#include "llvm/Support/raw_ostream.h" 33#include "llvm/Target/TargetLowering.h" 34using namespace llvm; 35 36STATISTIC(NumInvokes, "Number of invokes replaced"); 37STATISTIC(NumUnwinds, "Number of unwinds replaced"); 38STATISTIC(NumSpilled, "Number of registers live across unwind edges"); 39 40namespace { 41 class VISIBILITY_HIDDEN SjLjEHPass : public FunctionPass { 42 43 const TargetLowering *TLI; 44 45 const Type *FunctionContextTy; 46 Constant *RegisterFn; 47 Constant *UnregisterFn; 48 Constant *ResumeFn; 49 Constant *BuiltinSetjmpFn; 50 Constant *FrameAddrFn; 51 Constant *LSDAAddrFn; 52 Value *PersonalityFn; 53 Constant *Selector32Fn; 54 Constant *Selector64Fn; 55 Constant *ExceptionFn; 56 57 Value *CallSite; 58 public: 59 static char ID; // Pass identification, replacement for typeid 60 explicit SjLjEHPass(const TargetLowering *tli = NULL) 61 : FunctionPass(&ID), TLI(tli) { } 62 bool doInitialization(Module &M); 63 bool runOnFunction(Function &F); 64 65 virtual void getAnalysisUsage(AnalysisUsage &AU) const { } 66 const char *getPassName() const { 67 return "SJLJ Exception Handling preparation"; 68 } 69 70 private: 71 void markInvokeCallSite(InvokeInst *II, unsigned InvokeNo, 72 Value *CallSite, 73 SwitchInst *CatchSwitch); 74 void splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes); 75 bool insertSjLjEHSupport(Function &F); 76 }; 77} // end anonymous namespace 78 79char SjLjEHPass::ID = 0; 80 81// Public Interface To the SjLjEHPass pass. 82FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) { 83 return new SjLjEHPass(TLI); 84} 85// doInitialization - Make sure that there is a prototype for abort in the 86// current module. 87bool SjLjEHPass::doInitialization(Module &M) { 88 // Build the function context structure. 89 // builtin_setjmp uses a five word jbuf 90 const Type *VoidPtrTy = 91 PointerType::getUnqual(Type::getInt8Ty(M.getContext())); 92 const Type *Int32Ty = Type::getInt32Ty(M.getContext()); 93 FunctionContextTy = 94 StructType::get(M.getContext(), 95 VoidPtrTy, // __prev 96 Int32Ty, // call_site 97 ArrayType::get(Int32Ty, 4), // __data 98 VoidPtrTy, // __personality 99 VoidPtrTy, // __lsda 100 ArrayType::get(VoidPtrTy, 5), // __jbuf 101 NULL); 102 RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register", 103 Type::getVoidTy(M.getContext()), 104 PointerType::getUnqual(FunctionContextTy), 105 (Type *)0); 106 UnregisterFn = 107 M.getOrInsertFunction("_Unwind_SjLj_Unregister", 108 Type::getVoidTy(M.getContext()), 109 PointerType::getUnqual(FunctionContextTy), 110 (Type *)0); 111 ResumeFn = 112 M.getOrInsertFunction("_Unwind_SjLj_Resume", 113 Type::getVoidTy(M.getContext()), 114 VoidPtrTy, 115 (Type *)0); 116 FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); 117 BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp); 118 LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); 119 Selector32Fn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector_i32); 120 Selector64Fn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector_i64); 121 ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception); 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 and store zero into the 149 // location afterward. 150 new StoreInst(CallSiteNoC, CallSite, true, II); // volatile 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 // FIXME: ??? Or will this cause strangeness with mis-matched IDs like 156 // when it was in the front end? 157} 158 159/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until 160/// we reach blocks we've already seen. 161static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) { 162 if (!LiveBBs.insert(BB).second) return; // already been here. 163 164 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 165 MarkBlocksLiveIn(*PI, LiveBBs); 166} 167 168/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge 169/// we spill into a stack location, guaranteeing that there is nothing live 170/// across the unwind edge. This process also splits all critical edges 171/// coming out of invoke's. 172void SjLjEHPass:: 173splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) { 174 // First step, split all critical edges from invoke instructions. 175 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 176 InvokeInst *II = Invokes[i]; 177 SplitCriticalEdge(II, 0, this); 178 SplitCriticalEdge(II, 1, this); 179 assert(!isa<PHINode>(II->getNormalDest()) && 180 !isa<PHINode>(II->getUnwindDest()) && 181 "critical edge splitting left single entry phi nodes?"); 182 } 183 184 Function *F = Invokes.back()->getParent()->getParent(); 185 186 // To avoid having to handle incoming arguments specially, we lower each arg 187 // to a copy instruction in the entry block. This ensures that the argument 188 // value itself cannot be live across the entry block. 189 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin(); 190 while (isa<AllocaInst>(AfterAllocaInsertPt) && 191 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize())) 192 ++AfterAllocaInsertPt; 193 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); 194 AI != E; ++AI) { 195 // This is always a no-op cast because we're casting AI to AI->getType() so 196 // src and destination types are identical. BitCast is the only possibility. 197 CastInst *NC = new BitCastInst( 198 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt); 199 AI->replaceAllUsesWith(NC); 200 // Normally its is forbidden to replace a CastInst's operand because it 201 // could cause the opcode to reflect an illegal conversion. However, we're 202 // replacing it here with the same value it was constructed with to simply 203 // make NC its user. 204 NC->setOperand(0, AI); 205 } 206 207 // Finally, scan the code looking for instructions with bad live ranges. 208 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 209 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { 210 // Ignore obvious cases we don't have to handle. In particular, most 211 // instructions either have no uses or only have a single use inside the 212 // current block. Ignore them quickly. 213 Instruction *Inst = II; 214 if (Inst->use_empty()) continue; 215 if (Inst->hasOneUse() && 216 cast<Instruction>(Inst->use_back())->getParent() == BB && 217 !isa<PHINode>(Inst->use_back())) continue; 218 219 // If this is an alloca in the entry block, it's not a real register 220 // value. 221 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) 222 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin()) 223 continue; 224 225 // Avoid iterator invalidation by copying users to a temporary vector. 226 SmallVector<Instruction*,16> Users; 227 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); 228 UI != E; ++UI) { 229 Instruction *User = cast<Instruction>(*UI); 230 if (User->getParent() != BB || isa<PHINode>(User)) 231 Users.push_back(User); 232 } 233 234 // Find all of the blocks that this value is live in. 235 std::set<BasicBlock*> LiveBBs; 236 LiveBBs.insert(Inst->getParent()); 237 while (!Users.empty()) { 238 Instruction *U = Users.back(); 239 Users.pop_back(); 240 241 if (!isa<PHINode>(U)) { 242 MarkBlocksLiveIn(U->getParent(), LiveBBs); 243 } else { 244 // Uses for a PHI node occur in their predecessor block. 245 PHINode *PN = cast<PHINode>(U); 246 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 247 if (PN->getIncomingValue(i) == Inst) 248 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); 249 } 250 } 251 252 // Now that we know all of the blocks that this thing is live in, see if 253 // it includes any of the unwind locations. 254 bool NeedsSpill = false; 255 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 256 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); 257 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { 258 NeedsSpill = true; 259 } 260 } 261 262 // If we decided we need a spill, do it. 263 if (NeedsSpill) { 264 ++NumSpilled; 265 DemoteRegToStack(*Inst, true); 266 } 267 } 268} 269 270bool SjLjEHPass::insertSjLjEHSupport(Function &F) { 271 SmallVector<ReturnInst*,16> Returns; 272 SmallVector<UnwindInst*,16> Unwinds; 273 SmallVector<InvokeInst*,16> Invokes; 274 275 // Look through the terminators of the basic blocks to find invokes, returns 276 // and unwinds 277 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 278 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { 279 // Remember all return instructions in case we insert an invoke into this 280 // function. 281 Returns.push_back(RI); 282 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { 283 Invokes.push_back(II); 284 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 285 Unwinds.push_back(UI); 286 } 287 // If we don't have any invokes or unwinds, there's nothing to do. 288 if (Unwinds.empty() && Invokes.empty()) return false; 289 290 NumInvokes += Invokes.size(); 291 NumUnwinds += Unwinds.size(); 292 293 294 if (!Invokes.empty()) { 295 // We have invokes, so we need to add register/unregister calls to get 296 // this function onto the global unwind stack. 297 // 298 // First thing we need to do is scan the whole function for values that are 299 // live across unwind edges. Each value that is live across an unwind edge 300 // we spill into a stack location, guaranteeing that there is nothing live 301 // across the unwind edge. This process also splits all critical edges 302 // coming out of invoke's. 303 splitLiveRangesLiveAcrossInvokes(Invokes); 304 305 BasicBlock *EntryBB = F.begin(); 306 // Create an alloca for the incoming jump buffer ptr and the new jump buffer 307 // that needs to be restored on all exits from the function. This is an 308 // alloca because the value needs to be added to the global context list. 309 unsigned Align = 4; // FIXME: Should be a TLI check? 310 AllocaInst *FunctionContext = 311 new AllocaInst(FunctionContextTy, 0, Align, 312 "fcn_context", F.begin()->begin()); 313 314 Value *Idxs[2]; 315 const Type *Int32Ty = Type::getInt32Ty(F.getContext()); 316 Value *Zero = ConstantInt::get(Int32Ty, 0); 317 // We need to also keep around a reference to the call_site field 318 Idxs[0] = Zero; 319 Idxs[1] = ConstantInt::get(Int32Ty, 1); 320 CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 321 "call_site", 322 EntryBB->getTerminator()); 323 324 // The exception selector comes back in context->data[1] 325 Idxs[1] = ConstantInt::get(Int32Ty, 2); 326 Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2, 327 "fc_data", 328 EntryBB->getTerminator()); 329 Idxs[1] = ConstantInt::get(Int32Ty, 1); 330 Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2, 331 "exc_selector_gep", 332 EntryBB->getTerminator()); 333 // The exception value comes back in context->data[0] 334 Idxs[1] = Zero; 335 Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2, 336 "exception_gep", 337 EntryBB->getTerminator()); 338 339 // Find the eh.selector.* and eh.exception calls. We'll use the first 340 // ex.selector to determine the right personality function to use. For 341 // SJLJ, we always use the same personality for the whole function, 342 // not on a per-selector basis. 343 // FIXME: That's a bit ugly. Better way? 344 SmallVector<CallInst*,16> EH_Selectors; 345 SmallVector<CallInst*,16> EH_Exceptions; 346 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 347 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 348 if (CallInst *CI = dyn_cast<CallInst>(I)) { 349 if (CI->getCalledFunction() == Selector32Fn || 350 CI->getCalledFunction() == Selector64Fn) { 351 if (!PersonalityFn) PersonalityFn = CI->getOperand(2); 352 EH_Selectors.push_back(CI); 353 } else if (CI->getCalledFunction() == ExceptionFn) { 354 EH_Exceptions.push_back(CI); 355 } 356 } 357 } 358 } 359 // The result of the eh.selector call will be replaced with a 360 // a reference to the selector value returned in the function 361 // context. We leave the selector itself so the EH analysis later 362 // can use it. 363 for (int i = 0, e = EH_Selectors.size(); i < e; ++i) { 364 CallInst *I = EH_Selectors[i]; 365 Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I); 366 I->replaceAllUsesWith(SelectorVal); 367 } 368 // eh.exception calls are replaced with references to the proper 369 // location in the context. Unlike eh.selector, the eh.exception 370 // calls are removed entirely. 371 for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) { 372 CallInst *I = EH_Exceptions[i]; 373 // Possible for there to be duplicates, so check to make sure 374 // the instruction hasn't already been removed. 375 if (!I->getParent()) continue; 376 Value *Val = new LoadInst(ExceptionAddr, "exception", true, I); 377 Type *Ty = PointerType::getUnqual(Type::getInt8Ty(F.getContext())); 378 Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I); 379 380 I->replaceAllUsesWith(Val); 381 I->eraseFromParent(); 382 } 383 384 385 386 387 // The entry block changes to have the eh.sjlj.setjmp, with a conditional 388 // branch to a dispatch block for non-zero returns. If we return normally, 389 // we're not handling an exception and just register the function context 390 // and continue. 391 392 // Create the dispatch block. The dispatch block is basically a big switch 393 // statement that goes to all of the invoke landing pads. 394 BasicBlock *DispatchBlock = 395 BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F); 396 397 // Insert a load in the Catch block, and a switch on its value. By default, 398 // we go to a block that just does an unwind (which is the correct action 399 // for a standard call). 400 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwindbb", &F); 401 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock)); 402 403 Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true, 404 DispatchBlock); 405 SwitchInst *DispatchSwitch = 406 SwitchInst::Create(DispatchLoad, UnwindBlock, Invokes.size(), 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::getInt8Ty(F.getContext())->getPointerTo(), "", 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