SjLjEHPrepare.cpp revision 288943
155682Smarkm//===- SjLjEHPrepare.cpp - Eliminate Invoke & Unwind instructions ---------===// 2233294Sstas// 3233294Sstas// The LLVM Compiler Infrastructure 4233294Sstas// 555682Smarkm// This file is distributed under the University of Illinois Open Source 6233294Sstas// License. See LICENSE.TXT for details. 7233294Sstas// 8233294Sstas//===----------------------------------------------------------------------===// 955682Smarkm// 10233294Sstas// This transformation is designed for use by code generators which use SjLj 11233294Sstas// based exception handling. 1255682Smarkm// 13233294Sstas//===----------------------------------------------------------------------===// 14233294Sstas 15233294Sstas#include "llvm/CodeGen/Passes.h" 1655682Smarkm#include "llvm/ADT/DenseMap.h" 17233294Sstas#include "llvm/ADT/SetVector.h" 18233294Sstas#include "llvm/ADT/SmallPtrSet.h" 19233294Sstas#include "llvm/ADT/SmallVector.h" 2055682Smarkm#include "llvm/ADT/Statistic.h" 21233294Sstas#include "llvm/IR/Constants.h" 22233294Sstas#include "llvm/IR/DataLayout.h" 23233294Sstas#include "llvm/IR/DerivedTypes.h" 24233294Sstas#include "llvm/IR/IRBuilder.h" 25233294Sstas#include "llvm/IR/Instructions.h" 26233294Sstas#include "llvm/IR/Intrinsics.h" 27233294Sstas#include "llvm/IR/LLVMContext.h" 28233294Sstas#include "llvm/IR/Module.h" 29233294Sstas#include "llvm/Pass.h" 30233294Sstas#include "llvm/Support/CommandLine.h" 31233294Sstas#include "llvm/Support/Debug.h" 3255682Smarkm#include "llvm/Support/raw_ostream.h" 3355682Smarkm#include "llvm/Target/TargetLowering.h" 3455682Smarkm#include "llvm/Target/TargetSubtargetInfo.h" 3555682Smarkm#include "llvm/Transforms/Scalar.h" 3655682Smarkm#include "llvm/Transforms/Utils/BasicBlockUtils.h" 3755682Smarkm#include "llvm/Transforms/Utils/Local.h" 3855682Smarkm#include <set> 39120945Snectarusing namespace llvm; 4055682Smarkm 4155682Smarkm#define DEBUG_TYPE "sjljehprepare" 4255682Smarkm 4355682SmarkmSTATISTIC(NumInvokes, "Number of invokes replaced"); 4455682SmarkmSTATISTIC(NumSpilled, "Number of registers live across unwind edges"); 4555682Smarkm 4655682Smarkmnamespace { 4755682Smarkmclass SjLjEHPrepare : public FunctionPass { 4855682Smarkm Type *doubleUnderDataTy; 4955682Smarkm Type *doubleUnderJBufTy; 5055682Smarkm Type *FunctionContextTy; 5155682Smarkm Constant *RegisterFn; 52120945Snectar Constant *UnregisterFn; 5355682Smarkm Constant *BuiltinSetjmpFn; 5455682Smarkm Constant *FrameAddrFn; 5555682Smarkm Constant *StackAddrFn; 5655682Smarkm Constant *StackRestoreFn; 5755682Smarkm Constant *LSDAAddrFn; 5855682Smarkm Value *PersonalityFn; 59233294Sstas Constant *CallSiteFn; 6055682Smarkm Constant *FuncCtxFn; 6155682Smarkm AllocaInst *FuncCtx; 6255682Smarkm 6355682Smarkmpublic: 6455682Smarkm static char ID; // Pass identification, replacement for typeid 65233294Sstas explicit SjLjEHPrepare() : FunctionPass(ID) {} 6655682Smarkm bool doInitialization(Module &M) override; 6755682Smarkm bool runOnFunction(Function &F) override; 6855682Smarkm 6955682Smarkm void getAnalysisUsage(AnalysisUsage &AU) const override {} 7055682Smarkm const char *getPassName() const override { 71233294Sstas return "SJLJ Exception Handling preparation"; 7255682Smarkm } 7355682Smarkm 7455682Smarkmprivate: 7555682Smarkm bool setupEntryBlockAndCallSites(Function &F); 76 void substituteLPadValues(LandingPadInst *LPI, Value *ExnVal, Value *SelVal); 77 Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst *> LPads); 78 void lowerIncomingArguments(Function &F); 79 void lowerAcrossUnwindEdges(Function &F, ArrayRef<InvokeInst *> Invokes); 80 void insertCallSiteStore(Instruction *I, int Number); 81}; 82} // end anonymous namespace 83 84char SjLjEHPrepare::ID = 0; 85INITIALIZE_PASS(SjLjEHPrepare, "sjljehprepare", "Prepare SjLj exceptions", 86 false, false) 87 88// Public Interface To the SjLjEHPrepare pass. 89FunctionPass *llvm::createSjLjEHPreparePass() { return new SjLjEHPrepare(); } 90// doInitialization - Set up decalarations and types needed to process 91// exceptions. 92bool SjLjEHPrepare::doInitialization(Module &M) { 93 // Build the function context structure. 94 // builtin_setjmp uses a five word jbuf 95 Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext()); 96 Type *Int32Ty = Type::getInt32Ty(M.getContext()); 97 doubleUnderDataTy = ArrayType::get(Int32Ty, 4); 98 doubleUnderJBufTy = ArrayType::get(VoidPtrTy, 5); 99 FunctionContextTy = StructType::get(VoidPtrTy, // __prev 100 Int32Ty, // call_site 101 doubleUnderDataTy, // __data 102 VoidPtrTy, // __personality 103 VoidPtrTy, // __lsda 104 doubleUnderJBufTy, // __jbuf 105 nullptr); 106 RegisterFn = M.getOrInsertFunction( 107 "_Unwind_SjLj_Register", Type::getVoidTy(M.getContext()), 108 PointerType::getUnqual(FunctionContextTy), (Type *)nullptr); 109 UnregisterFn = M.getOrInsertFunction( 110 "_Unwind_SjLj_Unregister", Type::getVoidTy(M.getContext()), 111 PointerType::getUnqual(FunctionContextTy), (Type *)nullptr); 112 FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); 113 StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave); 114 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore); 115 BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp); 116 LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); 117 CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); 118 FuncCtxFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_functioncontext); 119 PersonalityFn = nullptr; 120 121 return true; 122} 123 124/// insertCallSiteStore - Insert a store of the call-site value to the 125/// function context 126void SjLjEHPrepare::insertCallSiteStore(Instruction *I, int Number) { 127 IRBuilder<> Builder(I); 128 129 // Get a reference to the call_site field. 130 Type *Int32Ty = Type::getInt32Ty(I->getContext()); 131 Value *Zero = ConstantInt::get(Int32Ty, 0); 132 Value *One = ConstantInt::get(Int32Ty, 1); 133 Value *Idxs[2] = { Zero, One }; 134 Value *CallSite = 135 Builder.CreateGEP(FunctionContextTy, FuncCtx, Idxs, "call_site"); 136 137 // Insert a store of the call-site number 138 ConstantInt *CallSiteNoC = 139 ConstantInt::get(Type::getInt32Ty(I->getContext()), Number); 140 Builder.CreateStore(CallSiteNoC, CallSite, true /*volatile*/); 141} 142 143/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until 144/// we reach blocks we've already seen. 145static void MarkBlocksLiveIn(BasicBlock *BB, 146 SmallPtrSetImpl<BasicBlock *> &LiveBBs) { 147 if (!LiveBBs.insert(BB).second) 148 return; // already been here. 149 150 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 151 MarkBlocksLiveIn(*PI, LiveBBs); 152} 153 154/// substituteLPadValues - Substitute the values returned by the landingpad 155/// instruction with those returned by the personality function. 156void SjLjEHPrepare::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal, 157 Value *SelVal) { 158 SmallVector<Value *, 8> UseWorkList(LPI->user_begin(), LPI->user_end()); 159 while (!UseWorkList.empty()) { 160 Value *Val = UseWorkList.pop_back_val(); 161 ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val); 162 if (!EVI) 163 continue; 164 if (EVI->getNumIndices() != 1) 165 continue; 166 if (*EVI->idx_begin() == 0) 167 EVI->replaceAllUsesWith(ExnVal); 168 else if (*EVI->idx_begin() == 1) 169 EVI->replaceAllUsesWith(SelVal); 170 if (EVI->getNumUses() == 0) 171 EVI->eraseFromParent(); 172 } 173 174 if (LPI->getNumUses() == 0) 175 return; 176 177 // There are still some uses of LPI. Construct an aggregate with the exception 178 // values and replace the LPI with that aggregate. 179 Type *LPadType = LPI->getType(); 180 Value *LPadVal = UndefValue::get(LPadType); 181 IRBuilder<> Builder( 182 std::next(BasicBlock::iterator(cast<Instruction>(SelVal)))); 183 LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val"); 184 LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val"); 185 186 LPI->replaceAllUsesWith(LPadVal); 187} 188 189/// setupFunctionContext - Allocate the function context on the stack and fill 190/// it with all of the data that we know at this point. 191Value *SjLjEHPrepare::setupFunctionContext(Function &F, 192 ArrayRef<LandingPadInst *> LPads) { 193 BasicBlock *EntryBB = F.begin(); 194 195 // Create an alloca for the incoming jump buffer ptr and the new jump buffer 196 // that needs to be restored on all exits from the function. This is an alloca 197 // because the value needs to be added to the global context list. 198 auto &DL = F.getParent()->getDataLayout(); 199 unsigned Align = DL.getPrefTypeAlignment(FunctionContextTy); 200 FuncCtx = new AllocaInst(FunctionContextTy, nullptr, Align, "fn_context", 201 EntryBB->begin()); 202 203 // Fill in the function context structure. 204 for (unsigned I = 0, E = LPads.size(); I != E; ++I) { 205 LandingPadInst *LPI = LPads[I]; 206 IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt()); 207 208 // Reference the __data field. 209 Value *FCData = 210 Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 2, "__data"); 211 212 // The exception values come back in context->__data[0]. 213 Value *ExceptionAddr = Builder.CreateConstGEP2_32(doubleUnderDataTy, FCData, 214 0, 0, "exception_gep"); 215 Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val"); 216 ExnVal = Builder.CreateIntToPtr(ExnVal, Builder.getInt8PtrTy()); 217 218 Value *SelectorAddr = Builder.CreateConstGEP2_32(doubleUnderDataTy, FCData, 219 0, 1, "exn_selector_gep"); 220 Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val"); 221 222 substituteLPadValues(LPI, ExnVal, SelVal); 223 } 224 225 // Personality function 226 IRBuilder<> Builder(EntryBB->getTerminator()); 227 if (!PersonalityFn) 228 PersonalityFn = F.getPersonalityFn(); 229 Value *PersonalityFieldPtr = Builder.CreateConstGEP2_32( 230 FunctionContextTy, FuncCtx, 0, 3, "pers_fn_gep"); 231 Builder.CreateStore( 232 Builder.CreateBitCast(PersonalityFn, Builder.getInt8PtrTy()), 233 PersonalityFieldPtr, /*isVolatile=*/true); 234 235 // LSDA address 236 Value *LSDA = Builder.CreateCall(LSDAAddrFn, {}, "lsda_addr"); 237 Value *LSDAFieldPtr = 238 Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 4, "lsda_gep"); 239 Builder.CreateStore(LSDA, LSDAFieldPtr, /*isVolatile=*/true); 240 241 return FuncCtx; 242} 243 244/// lowerIncomingArguments - To avoid having to handle incoming arguments 245/// specially, we lower each arg to a copy instruction in the entry block. This 246/// ensures that the argument value itself cannot be live out of the entry 247/// block. 248void SjLjEHPrepare::lowerIncomingArguments(Function &F) { 249 BasicBlock::iterator AfterAllocaInsPt = F.begin()->begin(); 250 while (isa<AllocaInst>(AfterAllocaInsPt) && 251 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsPt)->getArraySize())) 252 ++AfterAllocaInsPt; 253 254 for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end(); AI != AE; 255 ++AI) { 256 Type *Ty = AI->getType(); 257 258 // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction. 259 Value *TrueValue = ConstantInt::getTrue(F.getContext()); 260 Value *UndefValue = UndefValue::get(Ty); 261 Instruction *SI = SelectInst::Create(TrueValue, AI, UndefValue, 262 AI->getName() + ".tmp", 263 AfterAllocaInsPt); 264 AI->replaceAllUsesWith(SI); 265 266 // Reset the operand, because it was clobbered by the RAUW above. 267 SI->setOperand(1, AI); 268 } 269} 270 271/// lowerAcrossUnwindEdges - Find all variables which are alive across an unwind 272/// edge and spill them. 273void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F, 274 ArrayRef<InvokeInst *> Invokes) { 275 // Finally, scan the code looking for instructions with bad live ranges. 276 for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) { 277 for (BasicBlock::iterator II = BB->begin(), IIE = BB->end(); II != IIE; 278 ++II) { 279 // Ignore obvious cases we don't have to handle. In particular, most 280 // instructions either have no uses or only have a single use inside the 281 // current block. Ignore them quickly. 282 Instruction *Inst = II; 283 if (Inst->use_empty()) 284 continue; 285 if (Inst->hasOneUse() && 286 cast<Instruction>(Inst->user_back())->getParent() == BB && 287 !isa<PHINode>(Inst->user_back())) 288 continue; 289 290 // If this is an alloca in the entry block, it's not a real register 291 // value. 292 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) 293 if (isa<ConstantInt>(AI->getArraySize()) && BB == F.begin()) 294 continue; 295 296 // Avoid iterator invalidation by copying users to a temporary vector. 297 SmallVector<Instruction *, 16> Users; 298 for (User *U : Inst->users()) { 299 Instruction *UI = cast<Instruction>(U); 300 if (UI->getParent() != BB || isa<PHINode>(UI)) 301 Users.push_back(UI); 302 } 303 304 // Find all of the blocks that this value is live in. 305 SmallPtrSet<BasicBlock *, 64> LiveBBs; 306 LiveBBs.insert(Inst->getParent()); 307 while (!Users.empty()) { 308 Instruction *U = Users.back(); 309 Users.pop_back(); 310 311 if (!isa<PHINode>(U)) { 312 MarkBlocksLiveIn(U->getParent(), LiveBBs); 313 } else { 314 // Uses for a PHI node occur in their predecessor block. 315 PHINode *PN = cast<PHINode>(U); 316 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 317 if (PN->getIncomingValue(i) == Inst) 318 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); 319 } 320 } 321 322 // Now that we know all of the blocks that this thing is live in, see if 323 // it includes any of the unwind locations. 324 bool NeedsSpill = false; 325 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 326 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); 327 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { 328 DEBUG(dbgs() << "SJLJ Spill: " << *Inst << " around " 329 << UnwindBlock->getName() << "\n"); 330 NeedsSpill = true; 331 break; 332 } 333 } 334 335 // If we decided we need a spill, do it. 336 // FIXME: Spilling this way is overkill, as it forces all uses of 337 // the value to be reloaded from the stack slot, even those that aren't 338 // in the unwind blocks. We should be more selective. 339 if (NeedsSpill) { 340 DemoteRegToStack(*Inst, true); 341 ++NumSpilled; 342 } 343 } 344 } 345 346 // Go through the landing pads and remove any PHIs there. 347 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { 348 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); 349 LandingPadInst *LPI = UnwindBlock->getLandingPadInst(); 350 351 // Place PHIs into a set to avoid invalidating the iterator. 352 SmallPtrSet<PHINode *, 8> PHIsToDemote; 353 for (BasicBlock::iterator PN = UnwindBlock->begin(); isa<PHINode>(PN); ++PN) 354 PHIsToDemote.insert(cast<PHINode>(PN)); 355 if (PHIsToDemote.empty()) 356 continue; 357 358 // Demote the PHIs to the stack. 359 for (PHINode *PN : PHIsToDemote) 360 DemotePHIToStack(PN); 361 362 // Move the landingpad instruction back to the top of the landing pad block. 363 LPI->moveBefore(UnwindBlock->begin()); 364 } 365} 366 367/// setupEntryBlockAndCallSites - Setup the entry block by creating and filling 368/// the function context and marking the call sites with the appropriate 369/// values. These values are used by the DWARF EH emitter. 370bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) { 371 SmallVector<ReturnInst *, 16> Returns; 372 SmallVector<InvokeInst *, 16> Invokes; 373 SmallSetVector<LandingPadInst *, 16> LPads; 374 375 // Look through the terminators of the basic blocks to find invokes. 376 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 377 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { 378 if (Function *Callee = II->getCalledFunction()) 379 if (Callee->isIntrinsic() && 380 Callee->getIntrinsicID() == Intrinsic::donothing) { 381 // Remove the NOP invoke. 382 BranchInst::Create(II->getNormalDest(), II); 383 II->eraseFromParent(); 384 continue; 385 } 386 387 Invokes.push_back(II); 388 LPads.insert(II->getUnwindDest()->getLandingPadInst()); 389 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { 390 Returns.push_back(RI); 391 } 392 393 if (Invokes.empty()) 394 return false; 395 396 NumInvokes += Invokes.size(); 397 398 lowerIncomingArguments(F); 399 lowerAcrossUnwindEdges(F, Invokes); 400 401 Value *FuncCtx = 402 setupFunctionContext(F, makeArrayRef(LPads.begin(), LPads.end())); 403 BasicBlock *EntryBB = F.begin(); 404 IRBuilder<> Builder(EntryBB->getTerminator()); 405 406 // Get a reference to the jump buffer. 407 Value *JBufPtr = 408 Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 5, "jbuf_gep"); 409 410 // Save the frame pointer. 411 Value *FramePtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 0, 412 "jbuf_fp_gep"); 413 414 Value *Val = Builder.CreateCall(FrameAddrFn, Builder.getInt32(0), "fp"); 415 Builder.CreateStore(Val, FramePtr, /*isVolatile=*/true); 416 417 // Save the stack pointer. 418 Value *StackPtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 2, 419 "jbuf_sp_gep"); 420 421 Val = Builder.CreateCall(StackAddrFn, {}, "sp"); 422 Builder.CreateStore(Val, StackPtr, /*isVolatile=*/true); 423 424 // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. 425 Value *SetjmpArg = Builder.CreateBitCast(JBufPtr, Builder.getInt8PtrTy()); 426 Builder.CreateCall(BuiltinSetjmpFn, SetjmpArg); 427 428 // Store a pointer to the function context so that the back-end will know 429 // where to look for it. 430 Value *FuncCtxArg = Builder.CreateBitCast(FuncCtx, Builder.getInt8PtrTy()); 431 Builder.CreateCall(FuncCtxFn, FuncCtxArg); 432 433 // At this point, we are all set up, update the invoke instructions to mark 434 // their call_site values. 435 for (unsigned I = 0, E = Invokes.size(); I != E; ++I) { 436 insertCallSiteStore(Invokes[I], I + 1); 437 438 ConstantInt *CallSiteNum = 439 ConstantInt::get(Type::getInt32Ty(F.getContext()), I + 1); 440 441 // Record the call site value for the back end so it stays associated with 442 // the invoke. 443 CallInst::Create(CallSiteFn, CallSiteNum, "", Invokes[I]); 444 } 445 446 // Mark call instructions that aren't nounwind as no-action (call_site == 447 // -1). Skip the entry block, as prior to then, no function context has been 448 // created for this function and any unexpected exceptions thrown will go 449 // directly to the caller's context, which is what we want anyway, so no need 450 // to do anything here. 451 for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) 452 for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I) 453 if (CallInst *CI = dyn_cast<CallInst>(I)) { 454 if (!CI->doesNotThrow()) 455 insertCallSiteStore(CI, -1); 456 } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) { 457 insertCallSiteStore(RI, -1); 458 } 459 460 // Register the function context and make sure it's known to not throw 461 CallInst *Register = 462 CallInst::Create(RegisterFn, FuncCtx, "", EntryBB->getTerminator()); 463 Register->setDoesNotThrow(); 464 465 // Following any allocas not in the entry block, update the saved SP in the 466 // jmpbuf to the new value. 467 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 468 if (BB == F.begin()) 469 continue; 470 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 471 if (CallInst *CI = dyn_cast<CallInst>(I)) { 472 if (CI->getCalledFunction() != StackRestoreFn) 473 continue; 474 } else if (!isa<AllocaInst>(I)) { 475 continue; 476 } 477 Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp"); 478 StackAddr->insertAfter(I); 479 Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true); 480 StoreStackAddr->insertAfter(StackAddr); 481 } 482 } 483 484 // Finally, for any returns from this function, if this function contains an 485 // invoke, add a call to unregister the function context. 486 for (unsigned I = 0, E = Returns.size(); I != E; ++I) 487 CallInst::Create(UnregisterFn, FuncCtx, "", Returns[I]); 488 489 return true; 490} 491 492bool SjLjEHPrepare::runOnFunction(Function &F) { 493 bool Res = setupEntryBlockAndCallSites(F); 494 return Res; 495} 496