1 //===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation is designed for use by code generators which do not yet
11 // support stack unwinding. This pass supports two models of exception handling
12 // lowering, the 'cheap' support and the 'expensive' support.
14 // 'Cheap' exception handling support gives the program the ability to execute
15 // any program which does not "throw an exception", by turning 'invoke'
16 // instructions into calls and by turning 'unwind' instructions into calls to
17 // abort(). If the program does dynamically use the unwind instruction, the
18 // program will print a message then abort.
20 // 'Expensive' exception handling support gives the full exception handling
21 // support to the program at the cost of making the 'invoke' instruction
22 // really expensive. It basically inserts setjmp/longjmp calls to emulate the
23 // exception handling as necessary.
25 // Because the 'expensive' support slows down programs a lot, and EH is only
26 // used for a subset of the programs, it must be specifically enabled by an
29 // Note that after this pass runs the CFG is not entirely accurate (exceptional
30 // control flow edges are not correct anymore) so only very simple things should
31 // be done after the lowerinvoke pass has run (like generation of native code).
32 // This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
33 // support the invoke instruction yet" lowering pass.
35 //===----------------------------------------------------------------------===//
37 #define DEBUG_TYPE "lowerinvoke"
38 #include "llvm/Transforms/Scalar.h"
39 #include "llvm/Constants.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/Instructions.h"
42 #include "llvm/Intrinsics.h"
43 #include "llvm/LLVMContext.h"
44 #include "llvm/Module.h"
45 #include "llvm/Pass.h"
46 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
47 #include "llvm/Transforms/Utils/Local.h"
48 #include "llvm/ADT/SmallVector.h"
49 #include "llvm/ADT/Statistic.h"
50 #include "llvm/Support/CommandLine.h"
51 #include "llvm/Target/TargetLowering.h"
56 STATISTIC(NumInvokes, "Number of invokes replaced");
57 STATISTIC(NumUnwinds, "Number of unwinds replaced");
58 STATISTIC(NumSpilled, "Number of registers live across unwind edges");
60 static cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
61 cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
64 class LowerInvoke : public FunctionPass {
65 // Used for both models.
69 unsigned AbortMessageLength;
71 // Used for expensive EH support.
73 GlobalVariable *JBListHead;
74 Constant *SetJmpFn, *LongJmpFn, *StackSaveFn, *StackRestoreFn;
75 bool useExpensiveEHSupport;
77 // We peek in TLI to grab the target's jmp_buf size and alignment
78 const TargetLowering *TLI;
81 static char ID; // Pass identification, replacement for typeid
82 explicit LowerInvoke(const TargetLowering *tli = NULL,
83 bool useExpensiveEHSupport = ExpensiveEHSupport)
84 : FunctionPass(&ID), useExpensiveEHSupport(useExpensiveEHSupport),
86 bool doInitialization(Module &M);
87 bool runOnFunction(Function &F);
89 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
90 // This is a cluster of orthogonal Transforms
91 AU.addPreservedID(PromoteMemoryToRegisterID);
92 AU.addPreservedID(LowerSwitchID);
96 void createAbortMessage(Module *M);
97 void writeAbortMessage(Instruction *IB);
98 bool insertCheapEHSupport(Function &F);
99 void splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*>&Invokes);
100 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
101 AllocaInst *InvokeNum, AllocaInst *StackPtr,
102 SwitchInst *CatchSwitch);
103 bool insertExpensiveEHSupport(Function &F);
107 char LowerInvoke::ID = 0;
108 static RegisterPass<LowerInvoke>
109 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
111 const PassInfo *const llvm::LowerInvokePassID = &X;
113 // Public Interface To the LowerInvoke pass.
114 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
115 return new LowerInvoke(TLI, ExpensiveEHSupport);
117 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI,
118 bool useExpensiveEHSupport) {
119 return new LowerInvoke(TLI, useExpensiveEHSupport);
122 // doInitialization - Make sure that there is a prototype for abort in the
124 bool LowerInvoke::doInitialization(Module &M) {
125 const Type *VoidPtrTy =
126 Type::getInt8PtrTy(M.getContext());
128 if (useExpensiveEHSupport) {
129 // Insert a type for the linked list of jump buffers.
130 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
131 JBSize = JBSize ? JBSize : 200;
132 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
134 { // The type is recursive, so use a type holder.
135 std::vector<const Type*> Elements;
136 Elements.push_back(JmpBufTy);
137 OpaqueType *OT = OpaqueType::get(M.getContext());
138 Elements.push_back(PointerType::getUnqual(OT));
139 PATypeHolder JBLType(StructType::get(M.getContext(), Elements));
140 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
141 JBLinkTy = JBLType.get();
142 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
145 const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
147 // Now that we've done that, insert the jmpbuf list head global, unless it
149 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
150 JBListHead = new GlobalVariable(M, PtrJBList, false,
151 GlobalValue::LinkOnceAnyLinkage,
152 Constant::getNullValue(PtrJBList),
153 "llvm.sjljeh.jblist");
156 // VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
157 // so it looks like Intrinsic::_setjmp
158 #if defined(_MSC_VER) && defined(setjmp)
159 #define setjmp_undefined_for_visual_studio
163 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
165 #if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
166 // let's return it to _setjmp state in case anyone ever needs it after this
167 // point under VisualStudio
168 #define setjmp _setjmp
171 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
172 StackSaveFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
173 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
176 // We need the 'write' and 'abort' functions for both models.
177 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
179 #if 0 // "write" is Unix-specific.. code is going away soon anyway.
180 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
181 VoidPtrTy, Type::Int32Ty, (Type *)0);
188 void LowerInvoke::createAbortMessage(Module *M) {
189 Constant *Null32 = Constant::getNullValue(Type::getInt32Ty(M->getContext()));
190 Constant *GEPIdx[2] = { Null32, Null32 };
191 if (useExpensiveEHSupport) {
192 // The abort message for expensive EH support tells the user that the
193 // program 'unwound' without an 'invoke' instruction.
195 ConstantArray::get(M->getContext(),
196 "ERROR: Exception thrown, but not caught!\n");
197 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
199 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
200 GlobalValue::InternalLinkage,
202 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
204 // The abort message for cheap EH support tells the user that EH is not
207 ConstantArray::get(M->getContext(),
208 "Exception handler needed, but not enabled."
209 "Recompile program with -enable-correct-eh-support.\n");
210 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
212 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
213 GlobalValue::InternalLinkage,
215 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
220 void LowerInvoke::writeAbortMessage(Instruction *IB) {
222 if (AbortMessage == 0)
223 createAbortMessage(IB->getParent()->getParent()->getParent());
225 // These are the arguments we WANT...
227 Args[0] = ConstantInt::get(Type::Int32Ty, 2);
228 Args[1] = AbortMessage;
229 Args[2] = ConstantInt::get(Type::Int32Ty, AbortMessageLength);
230 (new CallInst(WriteFn, Args, 3, "", IB))->setTailCall();
234 bool LowerInvoke::insertCheapEHSupport(Function &F) {
235 bool Changed = false;
236 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
237 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
238 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
239 // Insert a normal call instruction...
240 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
241 CallArgs.begin(), CallArgs.end(),
243 NewCall->takeName(II);
244 NewCall->setCallingConv(II->getCallingConv());
245 NewCall->setAttributes(II->getAttributes());
246 II->replaceAllUsesWith(NewCall);
248 // Insert an unconditional branch to the normal destination.
249 BranchInst::Create(II->getNormalDest(), II);
251 // Remove any PHI node entries from the exception destination.
252 II->getUnwindDest()->removePredecessor(BB);
254 // Remove the invoke instruction now.
255 BB->getInstList().erase(II);
257 ++NumInvokes; Changed = true;
258 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
259 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
260 writeAbortMessage(UI);
262 // Insert a call to abort()
263 CallInst::Create(AbortFn, "", UI)->setTailCall();
265 // Insert a return instruction. This really should be a "barrier", as it
267 ReturnInst::Create(F.getContext(),
268 F.getReturnType()->isVoidTy() ?
269 0 : Constant::getNullValue(F.getReturnType()), UI);
271 // Remove the unwind instruction now.
272 BB->getInstList().erase(UI);
274 ++NumUnwinds; Changed = true;
279 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
280 /// specified invoke instruction with a call.
281 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
282 AllocaInst *InvokeNum,
283 AllocaInst *StackPtr,
284 SwitchInst *CatchSwitch) {
285 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
288 // If the unwind edge has phi nodes, split the edge.
289 if (isa<PHINode>(II->getUnwindDest()->begin())) {
290 SplitCriticalEdge(II, 1, this);
292 // If there are any phi nodes left, they must have a single predecessor.
293 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
294 PN->replaceAllUsesWith(PN->getIncomingValue(0));
295 PN->eraseFromParent();
299 // Insert a store of the invoke num before the invoke and store zero into the
300 // location afterward.
301 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
303 // Insert a store of the stack ptr before the invoke, so we can restore it
304 // later in the exception case.
305 CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
306 new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
308 BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
310 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
311 InvokeNum, false, NI);
313 Instruction* StackPtrLoad = new LoadInst(StackPtr, "stackptr.restore", true,
314 II->getUnwindDest()->getFirstNonPHI()
316 CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
318 // Add a switch case to our unwind block.
319 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
321 // Insert a normal call instruction.
322 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
323 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
324 CallArgs.begin(), CallArgs.end(), "",
326 NewCall->takeName(II);
327 NewCall->setCallingConv(II->getCallingConv());
328 NewCall->setAttributes(II->getAttributes());
329 II->replaceAllUsesWith(NewCall);
331 // Replace the invoke with an uncond branch.
332 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
333 II->eraseFromParent();
336 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
337 /// we reach blocks we've already seen.
338 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
339 if (!LiveBBs.insert(BB).second) return; // already been here.
341 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
342 MarkBlocksLiveIn(*PI, LiveBBs);
345 // First thing we need to do is scan the whole function for values that are
346 // live across unwind edges. Each value that is live across an unwind edge
347 // we spill into a stack location, guaranteeing that there is nothing live
348 // across the unwind edge. This process also splits all critical edges
349 // coming out of invoke's.
351 splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
352 // First step, split all critical edges from invoke instructions.
353 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
354 InvokeInst *II = Invokes[i];
355 SplitCriticalEdge(II, 0, this);
356 SplitCriticalEdge(II, 1, this);
357 assert(!isa<PHINode>(II->getNormalDest()) &&
358 !isa<PHINode>(II->getUnwindDest()) &&
359 "critical edge splitting left single entry phi nodes?");
362 Function *F = Invokes.back()->getParent()->getParent();
364 // To avoid having to handle incoming arguments specially, we lower each arg
365 // to a copy instruction in the entry block. This ensures that the argument
366 // value itself cannot be live across the entry block.
367 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
368 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
369 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
370 ++AfterAllocaInsertPt;
371 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
373 const Type *Ty = AI->getType();
374 // StructType can't be cast, but is a legal argument type, so we have
375 // to handle them differently. We use an extract/insert pair as a
376 // lightweight method to achieve the same goal.
377 if (isa<StructType>(Ty)) {
378 Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsertPt);
379 Instruction *NI = InsertValueInst::Create(AI, EI, 0);
381 AI->replaceAllUsesWith(NI);
382 // Set the struct operand of the instructions back to the AllocaInst.
383 EI->setOperand(0, AI);
384 NI->setOperand(0, AI);
386 // This is always a no-op cast because we're casting AI to AI->getType()
387 // so src and destination types are identical. BitCast is the only
389 CastInst *NC = new BitCastInst(
390 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
391 AI->replaceAllUsesWith(NC);
392 // Set the operand of the cast instruction back to the AllocaInst.
393 // Normally it's forbidden to replace a CastInst's operand because it
394 // could cause the opcode to reflect an illegal conversion. However,
395 // we're replacing it here with the same value it was constructed with.
396 // We do this because the above replaceAllUsesWith() clobbered the
397 // operand, but we want this one to remain.
398 NC->setOperand(0, AI);
402 // Finally, scan the code looking for instructions with bad live ranges.
403 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
404 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
405 // Ignore obvious cases we don't have to handle. In particular, most
406 // instructions either have no uses or only have a single use inside the
407 // current block. Ignore them quickly.
408 Instruction *Inst = II;
409 if (Inst->use_empty()) continue;
410 if (Inst->hasOneUse() &&
411 cast<Instruction>(Inst->use_back())->getParent() == BB &&
412 !isa<PHINode>(Inst->use_back())) continue;
414 // If this is an alloca in the entry block, it's not a real register
416 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
417 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
420 // Avoid iterator invalidation by copying users to a temporary vector.
421 SmallVector<Instruction*,16> Users;
422 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
424 Instruction *User = cast<Instruction>(*UI);
425 if (User->getParent() != BB || isa<PHINode>(User))
426 Users.push_back(User);
429 // Scan all of the uses and see if the live range is live across an unwind
430 // edge. If we find a use live across an invoke edge, create an alloca
431 // and spill the value.
432 std::set<InvokeInst*> InvokesWithStoreInserted;
434 // Find all of the blocks that this value is live in.
435 std::set<BasicBlock*> LiveBBs;
436 LiveBBs.insert(Inst->getParent());
437 while (!Users.empty()) {
438 Instruction *U = Users.back();
441 if (!isa<PHINode>(U)) {
442 MarkBlocksLiveIn(U->getParent(), LiveBBs);
444 // Uses for a PHI node occur in their predecessor block.
445 PHINode *PN = cast<PHINode>(U);
446 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
447 if (PN->getIncomingValue(i) == Inst)
448 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
452 // Now that we know all of the blocks that this thing is live in, see if
453 // it includes any of the unwind locations.
454 bool NeedsSpill = false;
455 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
456 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
457 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
462 // If we decided we need a spill, do it.
465 DemoteRegToStack(*Inst, true);
470 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
471 SmallVector<ReturnInst*,16> Returns;
472 SmallVector<UnwindInst*,16> Unwinds;
473 SmallVector<InvokeInst*,16> Invokes;
475 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
476 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
477 // Remember all return instructions in case we insert an invoke into this
479 Returns.push_back(RI);
480 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
481 Invokes.push_back(II);
482 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
483 Unwinds.push_back(UI);
486 if (Unwinds.empty() && Invokes.empty()) return false;
488 NumInvokes += Invokes.size();
489 NumUnwinds += Unwinds.size();
491 // TODO: This is not an optimal way to do this. In particular, this always
492 // inserts setjmp calls into the entries of functions with invoke instructions
493 // even though there are possibly paths through the function that do not
494 // execute any invokes. In particular, for functions with early exits, e.g.
495 // the 'addMove' method in hexxagon, it would be nice to not have to do the
496 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
497 // would not be too hard to do.
499 // If we have an invoke instruction, insert a setjmp that dominates all
500 // invokes. After the setjmp, use a cond branch that goes to the original
501 // code path on zero, and to a designated 'catch' block of nonzero.
502 Value *OldJmpBufPtr = 0;
503 if (!Invokes.empty()) {
504 // First thing we need to do is scan the whole function for values that are
505 // live across unwind edges. Each value that is live across an unwind edge
506 // we spill into a stack location, guaranteeing that there is nothing live
507 // across the unwind edge. This process also splits all critical edges
508 // coming out of invoke's.
509 splitLiveRangesLiveAcrossInvokes(Invokes);
511 BasicBlock *EntryBB = F.begin();
513 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
514 // that needs to be restored on all exits from the function. This is an
515 // alloca because the value needs to be live across invokes.
516 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
518 new AllocaInst(JBLinkTy, 0, Align,
519 "jblink", F.begin()->begin());
521 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
522 ConstantInt::get(Type::getInt32Ty(F.getContext()), 1) };
523 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
525 EntryBB->getTerminator());
527 // Copy the JBListHead to the alloca.
528 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
529 EntryBB->getTerminator());
530 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
532 // Add the new jumpbuf to the list.
533 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
535 // Create the catch block. The catch block is basically a big switch
536 // statement that goes to all of the invoke catch blocks.
537 BasicBlock *CatchBB =
538 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
540 // Create an alloca which keeps track of the stack pointer before every
541 // invoke, this allows us to properly restore the stack pointer after
543 AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
544 "stackptr", EntryBB->begin());
546 // Create an alloca which keeps track of which invoke is currently
547 // executing. For normal calls it contains zero.
548 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
549 "invokenum",EntryBB->begin());
550 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
551 InvokeNum, true, EntryBB->getTerminator());
553 // Insert a load in the Catch block, and a switch on its value. By default,
554 // we go to a block that just does an unwind (which is the correct action
555 // for a standard call).
556 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
557 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
559 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
560 SwitchInst *CatchSwitch =
561 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
563 // Now that things are set up, insert the setjmp call itself.
565 // Split the entry block to insert the conditional branch for the setjmp.
566 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
569 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
570 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
572 EntryBB->getTerminator());
573 JmpBufPtr = new BitCastInst(JmpBufPtr,
574 Type::getInt8PtrTy(F.getContext()),
575 "tmp", EntryBB->getTerminator());
576 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
577 EntryBB->getTerminator());
579 // Compare the return value to zero.
580 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
581 ICmpInst::ICMP_EQ, SJRet,
582 Constant::getNullValue(SJRet->getType()),
584 // Nuke the uncond branch.
585 EntryBB->getTerminator()->eraseFromParent();
587 // Put in a new condbranch in its place.
588 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
590 // At this point, we are all set up, rewrite each invoke instruction.
591 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
592 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
595 // We know that there is at least one unwind.
597 // Create three new blocks, the block to load the jmpbuf ptr and compare
598 // against null, the block to do the longjmp, and the error block for if it
599 // is null. Add them at the end of the function because they are not hot.
600 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
602 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
603 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
605 // If this function contains an invoke, restore the old jumpbuf ptr.
608 // Before the return, insert a copy from the saved value to the new value.
609 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
610 new StoreInst(BufPtr, JBListHead, UnwindHandler);
612 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
615 // Load the JBList, if it's null, then there was no catch!
616 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
617 Constant::getNullValue(BufPtr->getType()),
619 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
621 // Create the block to do the longjmp.
622 // Get a pointer to the jmpbuf and longjmp.
623 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
624 ConstantInt::get(Type::getInt32Ty(F.getContext()), 0) };
625 Idx[0] = GetElementPtrInst::Create(BufPtr, &Idx[0], &Idx[2], "JmpBuf",
627 Idx[0] = new BitCastInst(Idx[0],
628 Type::getInt8PtrTy(F.getContext()),
630 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
631 CallInst::Create(LongJmpFn, &Idx[0], &Idx[2], "", UnwindBlock);
632 new UnreachableInst(F.getContext(), UnwindBlock);
634 // Set up the term block ("throw without a catch").
635 new UnreachableInst(F.getContext(), TermBlock);
637 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
638 writeAbortMessage(TermBlock->getTerminator());
640 // Insert a call to abort()
641 CallInst::Create(AbortFn, "",
642 TermBlock->getTerminator())->setTailCall();
645 // Replace all unwinds with a branch to the unwind handler.
646 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
647 BranchInst::Create(UnwindHandler, Unwinds[i]);
648 Unwinds[i]->eraseFromParent();
651 // Finally, for any returns from this function, if this function contains an
652 // invoke, restore the old jmpbuf pointer to its input value.
654 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
655 ReturnInst *R = Returns[i];
657 // Before the return, insert a copy from the saved value to the new value.
658 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
659 new StoreInst(OldBuf, JBListHead, true, R);
666 bool LowerInvoke::runOnFunction(Function &F) {
667 if (useExpensiveEHSupport)
668 return insertExpensiveEHSupport(F);
670 return insertCheapEHSupport(F);