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.
68 // Used for expensive EH support.
70 GlobalVariable *JBListHead;
71 Constant *SetJmpFn, *LongJmpFn, *StackSaveFn, *StackRestoreFn;
72 bool useExpensiveEHSupport;
74 // We peek in TLI to grab the target's jmp_buf size and alignment
75 const TargetLowering *TLI;
78 static char ID; // Pass identification, replacement for typeid
79 explicit LowerInvoke(const TargetLowering *tli = NULL,
80 bool useExpensiveEHSupport = ExpensiveEHSupport)
81 : FunctionPass(&ID), useExpensiveEHSupport(useExpensiveEHSupport),
83 bool doInitialization(Module &M);
84 bool runOnFunction(Function &F);
86 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
87 // This is a cluster of orthogonal Transforms
88 AU.addPreservedID(PromoteMemoryToRegisterID);
89 AU.addPreservedID(LowerSwitchID);
93 bool insertCheapEHSupport(Function &F);
94 void splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*>&Invokes);
95 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
96 AllocaInst *InvokeNum, AllocaInst *StackPtr,
97 SwitchInst *CatchSwitch);
98 bool insertExpensiveEHSupport(Function &F);
102 char LowerInvoke::ID = 0;
103 static RegisterPass<LowerInvoke>
104 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
106 const PassInfo *const llvm::LowerInvokePassID = &X;
108 // Public Interface To the LowerInvoke pass.
109 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
110 return new LowerInvoke(TLI, ExpensiveEHSupport);
112 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI,
113 bool useExpensiveEHSupport) {
114 return new LowerInvoke(TLI, useExpensiveEHSupport);
117 // doInitialization - Make sure that there is a prototype for abort in the
119 bool LowerInvoke::doInitialization(Module &M) {
120 const Type *VoidPtrTy =
121 Type::getInt8PtrTy(M.getContext());
122 if (useExpensiveEHSupport) {
123 // Insert a type for the linked list of jump buffers.
124 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
125 JBSize = JBSize ? JBSize : 200;
126 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
128 { // The type is recursive, so use a type holder.
129 std::vector<const Type*> Elements;
130 Elements.push_back(JmpBufTy);
131 OpaqueType *OT = OpaqueType::get(M.getContext());
132 Elements.push_back(PointerType::getUnqual(OT));
133 PATypeHolder JBLType(StructType::get(M.getContext(), Elements));
134 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
135 JBLinkTy = JBLType.get();
136 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
139 const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
141 // Now that we've done that, insert the jmpbuf list head global, unless it
143 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
144 JBListHead = new GlobalVariable(M, PtrJBList, false,
145 GlobalValue::LinkOnceAnyLinkage,
146 Constant::getNullValue(PtrJBList),
147 "llvm.sjljeh.jblist");
150 // VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
151 // so it looks like Intrinsic::_setjmp
152 #if defined(_MSC_VER) && defined(setjmp)
153 #define setjmp_undefined_for_visual_studio
157 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
159 #if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
160 // let's return it to _setjmp state in case anyone ever needs it after this
161 // point under VisualStudio
162 #define setjmp _setjmp
165 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
166 StackSaveFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
167 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
170 // We need the 'write' and 'abort' functions for both models.
171 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
176 bool LowerInvoke::insertCheapEHSupport(Function &F) {
177 bool Changed = false;
178 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
179 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
180 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
181 // Insert a normal call instruction...
182 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
183 CallArgs.begin(), CallArgs.end(),
185 NewCall->takeName(II);
186 NewCall->setCallingConv(II->getCallingConv());
187 NewCall->setAttributes(II->getAttributes());
188 II->replaceAllUsesWith(NewCall);
190 // Insert an unconditional branch to the normal destination.
191 BranchInst::Create(II->getNormalDest(), II);
193 // Remove any PHI node entries from the exception destination.
194 II->getUnwindDest()->removePredecessor(BB);
196 // Remove the invoke instruction now.
197 BB->getInstList().erase(II);
199 ++NumInvokes; Changed = true;
200 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
201 // Insert a call to abort()
202 CallInst::Create(AbortFn, "", UI)->setTailCall();
204 // Insert a return instruction. This really should be a "barrier", as it
206 ReturnInst::Create(F.getContext(),
207 F.getReturnType()->isVoidTy() ?
208 0 : Constant::getNullValue(F.getReturnType()), UI);
210 // Remove the unwind instruction now.
211 BB->getInstList().erase(UI);
213 ++NumUnwinds; Changed = true;
218 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
219 /// specified invoke instruction with a call.
220 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
221 AllocaInst *InvokeNum,
222 AllocaInst *StackPtr,
223 SwitchInst *CatchSwitch) {
224 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
227 // If the unwind edge has phi nodes, split the edge.
228 if (isa<PHINode>(II->getUnwindDest()->begin())) {
229 SplitCriticalEdge(II, 1, this);
231 // If there are any phi nodes left, they must have a single predecessor.
232 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
233 PN->replaceAllUsesWith(PN->getIncomingValue(0));
234 PN->eraseFromParent();
238 // Insert a store of the invoke num before the invoke and store zero into the
239 // location afterward.
240 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
242 // Insert a store of the stack ptr before the invoke, so we can restore it
243 // later in the exception case.
244 CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
245 new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
247 BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
249 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
250 InvokeNum, false, NI);
252 Instruction* StackPtrLoad = new LoadInst(StackPtr, "stackptr.restore", true,
253 II->getUnwindDest()->getFirstNonPHI()
255 CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
257 // Add a switch case to our unwind block.
258 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
260 // Insert a normal call instruction.
261 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
262 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
263 CallArgs.begin(), CallArgs.end(), "",
265 NewCall->takeName(II);
266 NewCall->setCallingConv(II->getCallingConv());
267 NewCall->setAttributes(II->getAttributes());
268 II->replaceAllUsesWith(NewCall);
270 // Replace the invoke with an uncond branch.
271 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
272 II->eraseFromParent();
275 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
276 /// we reach blocks we've already seen.
277 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
278 if (!LiveBBs.insert(BB).second) return; // already been here.
280 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
281 MarkBlocksLiveIn(*PI, LiveBBs);
284 // First thing we need to do is scan the whole function for values that are
285 // live across unwind edges. Each value that is live across an unwind edge
286 // we spill into a stack location, guaranteeing that there is nothing live
287 // across the unwind edge. This process also splits all critical edges
288 // coming out of invoke's.
290 splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
291 // First step, split all critical edges from invoke instructions.
292 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
293 InvokeInst *II = Invokes[i];
294 SplitCriticalEdge(II, 0, this);
295 SplitCriticalEdge(II, 1, this);
296 assert(!isa<PHINode>(II->getNormalDest()) &&
297 !isa<PHINode>(II->getUnwindDest()) &&
298 "critical edge splitting left single entry phi nodes?");
301 Function *F = Invokes.back()->getParent()->getParent();
303 // To avoid having to handle incoming arguments specially, we lower each arg
304 // to a copy instruction in the entry block. This ensures that the argument
305 // value itself cannot be live across the entry block.
306 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
307 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
308 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
309 ++AfterAllocaInsertPt;
310 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
312 const Type *Ty = AI->getType();
313 // StructType can't be cast, but is a legal argument type, so we have
314 // to handle them differently. We use an extract/insert pair as a
315 // lightweight method to achieve the same goal.
316 if (isa<StructType>(Ty)) {
317 Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsertPt);
318 Instruction *NI = InsertValueInst::Create(AI, EI, 0);
320 AI->replaceAllUsesWith(NI);
321 // Set the struct operand of the instructions back to the AllocaInst.
322 EI->setOperand(0, AI);
323 NI->setOperand(0, AI);
325 // This is always a no-op cast because we're casting AI to AI->getType()
326 // so src and destination types are identical. BitCast is the only
328 CastInst *NC = new BitCastInst(
329 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
330 AI->replaceAllUsesWith(NC);
331 // Set the operand of the cast instruction back to the AllocaInst.
332 // Normally it's forbidden to replace a CastInst's operand because it
333 // could cause the opcode to reflect an illegal conversion. However,
334 // we're replacing it here with the same value it was constructed with.
335 // We do this because the above replaceAllUsesWith() clobbered the
336 // operand, but we want this one to remain.
337 NC->setOperand(0, AI);
341 // Finally, scan the code looking for instructions with bad live ranges.
342 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
343 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
344 // Ignore obvious cases we don't have to handle. In particular, most
345 // instructions either have no uses or only have a single use inside the
346 // current block. Ignore them quickly.
347 Instruction *Inst = II;
348 if (Inst->use_empty()) continue;
349 if (Inst->hasOneUse() &&
350 cast<Instruction>(Inst->use_back())->getParent() == BB &&
351 !isa<PHINode>(Inst->use_back())) continue;
353 // If this is an alloca in the entry block, it's not a real register
355 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
356 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
359 // Avoid iterator invalidation by copying users to a temporary vector.
360 SmallVector<Instruction*,16> Users;
361 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
363 Instruction *User = cast<Instruction>(*UI);
364 if (User->getParent() != BB || isa<PHINode>(User))
365 Users.push_back(User);
368 // Scan all of the uses and see if the live range is live across an unwind
369 // edge. If we find a use live across an invoke edge, create an alloca
370 // and spill the value.
371 std::set<InvokeInst*> InvokesWithStoreInserted;
373 // Find all of the blocks that this value is live in.
374 std::set<BasicBlock*> LiveBBs;
375 LiveBBs.insert(Inst->getParent());
376 while (!Users.empty()) {
377 Instruction *U = Users.back();
380 if (!isa<PHINode>(U)) {
381 MarkBlocksLiveIn(U->getParent(), LiveBBs);
383 // Uses for a PHI node occur in their predecessor block.
384 PHINode *PN = cast<PHINode>(U);
385 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
386 if (PN->getIncomingValue(i) == Inst)
387 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
391 // Now that we know all of the blocks that this thing is live in, see if
392 // it includes any of the unwind locations.
393 bool NeedsSpill = false;
394 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
395 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
396 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
401 // If we decided we need a spill, do it.
404 DemoteRegToStack(*Inst, true);
409 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
410 SmallVector<ReturnInst*,16> Returns;
411 SmallVector<UnwindInst*,16> Unwinds;
412 SmallVector<InvokeInst*,16> Invokes;
414 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
415 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
416 // Remember all return instructions in case we insert an invoke into this
418 Returns.push_back(RI);
419 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
420 Invokes.push_back(II);
421 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
422 Unwinds.push_back(UI);
425 if (Unwinds.empty() && Invokes.empty()) return false;
427 NumInvokes += Invokes.size();
428 NumUnwinds += Unwinds.size();
430 // TODO: This is not an optimal way to do this. In particular, this always
431 // inserts setjmp calls into the entries of functions with invoke instructions
432 // even though there are possibly paths through the function that do not
433 // execute any invokes. In particular, for functions with early exits, e.g.
434 // the 'addMove' method in hexxagon, it would be nice to not have to do the
435 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
436 // would not be too hard to do.
438 // If we have an invoke instruction, insert a setjmp that dominates all
439 // invokes. After the setjmp, use a cond branch that goes to the original
440 // code path on zero, and to a designated 'catch' block of nonzero.
441 Value *OldJmpBufPtr = 0;
442 if (!Invokes.empty()) {
443 // First thing we need to do is scan the whole function for values that are
444 // live across unwind edges. Each value that is live across an unwind edge
445 // we spill into a stack location, guaranteeing that there is nothing live
446 // across the unwind edge. This process also splits all critical edges
447 // coming out of invoke's.
448 splitLiveRangesLiveAcrossInvokes(Invokes);
450 BasicBlock *EntryBB = F.begin();
452 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
453 // that needs to be restored on all exits from the function. This is an
454 // alloca because the value needs to be live across invokes.
455 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
457 new AllocaInst(JBLinkTy, 0, Align,
458 "jblink", F.begin()->begin());
460 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
461 ConstantInt::get(Type::getInt32Ty(F.getContext()), 1) };
462 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
464 EntryBB->getTerminator());
466 // Copy the JBListHead to the alloca.
467 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
468 EntryBB->getTerminator());
469 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
471 // Add the new jumpbuf to the list.
472 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
474 // Create the catch block. The catch block is basically a big switch
475 // statement that goes to all of the invoke catch blocks.
476 BasicBlock *CatchBB =
477 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
479 // Create an alloca which keeps track of the stack pointer before every
480 // invoke, this allows us to properly restore the stack pointer after
482 AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
483 "stackptr", EntryBB->begin());
485 // Create an alloca which keeps track of which invoke is currently
486 // executing. For normal calls it contains zero.
487 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
488 "invokenum",EntryBB->begin());
489 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
490 InvokeNum, true, EntryBB->getTerminator());
492 // Insert a load in the Catch block, and a switch on its value. By default,
493 // we go to a block that just does an unwind (which is the correct action
494 // for a standard call).
495 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
496 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
498 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
499 SwitchInst *CatchSwitch =
500 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
502 // Now that things are set up, insert the setjmp call itself.
504 // Split the entry block to insert the conditional branch for the setjmp.
505 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
508 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
509 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
511 EntryBB->getTerminator());
512 JmpBufPtr = new BitCastInst(JmpBufPtr,
513 Type::getInt8PtrTy(F.getContext()),
514 "tmp", EntryBB->getTerminator());
515 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
516 EntryBB->getTerminator());
518 // Compare the return value to zero.
519 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
520 ICmpInst::ICMP_EQ, SJRet,
521 Constant::getNullValue(SJRet->getType()),
523 // Nuke the uncond branch.
524 EntryBB->getTerminator()->eraseFromParent();
526 // Put in a new condbranch in its place.
527 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
529 // At this point, we are all set up, rewrite each invoke instruction.
530 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
531 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
534 // We know that there is at least one unwind.
536 // Create three new blocks, the block to load the jmpbuf ptr and compare
537 // against null, the block to do the longjmp, and the error block for if it
538 // is null. Add them at the end of the function because they are not hot.
539 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
541 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
542 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
544 // If this function contains an invoke, restore the old jumpbuf ptr.
547 // Before the return, insert a copy from the saved value to the new value.
548 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
549 new StoreInst(BufPtr, JBListHead, UnwindHandler);
551 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
554 // Load the JBList, if it's null, then there was no catch!
555 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
556 Constant::getNullValue(BufPtr->getType()),
558 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
560 // Create the block to do the longjmp.
561 // Get a pointer to the jmpbuf and longjmp.
562 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
563 ConstantInt::get(Type::getInt32Ty(F.getContext()), 0) };
564 Idx[0] = GetElementPtrInst::Create(BufPtr, &Idx[0], &Idx[2], "JmpBuf",
566 Idx[0] = new BitCastInst(Idx[0],
567 Type::getInt8PtrTy(F.getContext()),
569 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
570 CallInst::Create(LongJmpFn, &Idx[0], &Idx[2], "", UnwindBlock);
571 new UnreachableInst(F.getContext(), UnwindBlock);
573 // Set up the term block ("throw without a catch").
574 new UnreachableInst(F.getContext(), TermBlock);
576 // Insert a call to abort()
577 CallInst::Create(AbortFn, "",
578 TermBlock->getTerminator())->setTailCall();
581 // Replace all unwinds with a branch to the unwind handler.
582 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
583 BranchInst::Create(UnwindHandler, Unwinds[i]);
584 Unwinds[i]->eraseFromParent();
587 // Finally, for any returns from this function, if this function contains an
588 // invoke, restore the old jmpbuf pointer to its input value.
590 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
591 ReturnInst *R = Returns[i];
593 // Before the return, insert a copy from the saved value to the new value.
594 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
595 new StoreInst(OldBuf, JBListHead, true, R);
602 bool LowerInvoke::runOnFunction(Function &F) {
603 if (useExpensiveEHSupport)
604 return insertExpensiveEHSupport(F);
606 return insertCheapEHSupport(F);