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.addPreserved("mem2reg");
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 INITIALIZE_PASS(LowerInvoke, "lowerinvoke",
104 "Lower invoke and unwind, for unwindless code generators",
107 char &llvm::LowerInvokePassID = LowerInvoke::ID;
109 // Public Interface To the LowerInvoke pass.
110 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
111 return new LowerInvoke(TLI, ExpensiveEHSupport);
113 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI,
114 bool useExpensiveEHSupport) {
115 return new LowerInvoke(TLI, useExpensiveEHSupport);
118 // doInitialization - Make sure that there is a prototype for abort in the
120 bool LowerInvoke::doInitialization(Module &M) {
121 const Type *VoidPtrTy =
122 Type::getInt8PtrTy(M.getContext());
123 if (useExpensiveEHSupport) {
124 // Insert a type for the linked list of jump buffers.
125 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
126 JBSize = JBSize ? JBSize : 200;
127 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
129 { // The type is recursive, so use a type holder.
130 std::vector<const Type*> Elements;
131 Elements.push_back(JmpBufTy);
132 OpaqueType *OT = OpaqueType::get(M.getContext());
133 Elements.push_back(PointerType::getUnqual(OT));
134 PATypeHolder JBLType(StructType::get(M.getContext(), Elements));
135 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
136 JBLinkTy = JBLType.get();
137 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
140 const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
142 // Now that we've done that, insert the jmpbuf list head global, unless it
144 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
145 JBListHead = new GlobalVariable(M, PtrJBList, false,
146 GlobalValue::LinkOnceAnyLinkage,
147 Constant::getNullValue(PtrJBList),
148 "llvm.sjljeh.jblist");
151 // VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
152 // so it looks like Intrinsic::_setjmp
153 #if defined(_MSC_VER) && defined(setjmp)
154 #define setjmp_undefined_for_visual_studio
158 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
160 #if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
161 // let's return it to _setjmp state in case anyone ever needs it after this
162 // point under VisualStudio
163 #define setjmp _setjmp
166 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
167 StackSaveFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
168 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
171 // We need the 'write' and 'abort' functions for both models.
172 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
177 bool LowerInvoke::insertCheapEHSupport(Function &F) {
178 bool Changed = false;
179 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
180 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
181 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
182 // Insert a normal call instruction...
183 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
184 CallArgs.begin(), CallArgs.end(),
186 NewCall->takeName(II);
187 NewCall->setCallingConv(II->getCallingConv());
188 NewCall->setAttributes(II->getAttributes());
189 II->replaceAllUsesWith(NewCall);
191 // Insert an unconditional branch to the normal destination.
192 BranchInst::Create(II->getNormalDest(), II);
194 // Remove any PHI node entries from the exception destination.
195 II->getUnwindDest()->removePredecessor(BB);
197 // Remove the invoke instruction now.
198 BB->getInstList().erase(II);
200 ++NumInvokes; Changed = true;
201 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
202 // Insert a call to abort()
203 CallInst::Create(AbortFn, "", UI)->setTailCall();
205 // Insert a return instruction. This really should be a "barrier", as it
207 ReturnInst::Create(F.getContext(),
208 F.getReturnType()->isVoidTy() ?
209 0 : Constant::getNullValue(F.getReturnType()), UI);
211 // Remove the unwind instruction now.
212 BB->getInstList().erase(UI);
214 ++NumUnwinds; Changed = true;
219 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
220 /// specified invoke instruction with a call.
221 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
222 AllocaInst *InvokeNum,
223 AllocaInst *StackPtr,
224 SwitchInst *CatchSwitch) {
225 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
228 // If the unwind edge has phi nodes, split the edge.
229 if (isa<PHINode>(II->getUnwindDest()->begin())) {
230 SplitCriticalEdge(II, 1, this);
232 // If there are any phi nodes left, they must have a single predecessor.
233 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
234 PN->replaceAllUsesWith(PN->getIncomingValue(0));
235 PN->eraseFromParent();
239 // Insert a store of the invoke num before the invoke and store zero into the
240 // location afterward.
241 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
243 // Insert a store of the stack ptr before the invoke, so we can restore it
244 // later in the exception case.
245 CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
246 new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
248 BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
250 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
251 InvokeNum, false, NI);
253 Instruction* StackPtrLoad = new LoadInst(StackPtr, "stackptr.restore", true,
254 II->getUnwindDest()->getFirstNonPHI()
256 CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
258 // Add a switch case to our unwind block.
259 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
261 // Insert a normal call instruction.
262 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
263 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
264 CallArgs.begin(), CallArgs.end(), "",
266 NewCall->takeName(II);
267 NewCall->setCallingConv(II->getCallingConv());
268 NewCall->setAttributes(II->getAttributes());
269 II->replaceAllUsesWith(NewCall);
271 // Replace the invoke with an uncond branch.
272 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
273 II->eraseFromParent();
276 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
277 /// we reach blocks we've already seen.
278 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
279 if (!LiveBBs.insert(BB).second) return; // already been here.
281 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
282 MarkBlocksLiveIn(*PI, LiveBBs);
285 // First thing we need to do is scan the whole function for values that are
286 // live across unwind edges. Each value that is live across an unwind edge
287 // we spill into a stack location, guaranteeing that there is nothing live
288 // across the unwind edge. This process also splits all critical edges
289 // coming out of invoke's.
291 splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
292 // First step, split all critical edges from invoke instructions.
293 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
294 InvokeInst *II = Invokes[i];
295 SplitCriticalEdge(II, 0, this);
296 SplitCriticalEdge(II, 1, this);
297 assert(!isa<PHINode>(II->getNormalDest()) &&
298 !isa<PHINode>(II->getUnwindDest()) &&
299 "critical edge splitting left single entry phi nodes?");
302 Function *F = Invokes.back()->getParent()->getParent();
304 // To avoid having to handle incoming arguments specially, we lower each arg
305 // to a copy instruction in the entry block. This ensures that the argument
306 // value itself cannot be live across the entry block.
307 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
308 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
309 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
310 ++AfterAllocaInsertPt;
311 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
313 const Type *Ty = AI->getType();
314 // Aggregate types can't be cast, but are legal argument types, so we have
315 // to handle them differently. We use an extract/insert pair as a
316 // lightweight method to achieve the same goal.
317 if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
318 Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt);
319 Instruction *NI = InsertValueInst::Create(AI, EI, 0);
321 AI->replaceAllUsesWith(NI);
322 // Set the operand of the instructions back to the AllocaInst.
323 EI->setOperand(0, AI);
324 NI->setOperand(0, AI);
326 // This is always a no-op cast because we're casting AI to AI->getType()
327 // so src and destination types are identical. BitCast is the only
329 CastInst *NC = new BitCastInst(
330 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
331 AI->replaceAllUsesWith(NC);
332 // Set the operand of the cast instruction back to the AllocaInst.
333 // Normally it's forbidden to replace a CastInst's operand because it
334 // could cause the opcode to reflect an illegal conversion. However,
335 // we're replacing it here with the same value it was constructed with.
336 // We do this because the above replaceAllUsesWith() clobbered the
337 // operand, but we want this one to remain.
338 NC->setOperand(0, AI);
342 // Finally, scan the code looking for instructions with bad live ranges.
343 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
344 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
345 // Ignore obvious cases we don't have to handle. In particular, most
346 // instructions either have no uses or only have a single use inside the
347 // current block. Ignore them quickly.
348 Instruction *Inst = II;
349 if (Inst->use_empty()) continue;
350 if (Inst->hasOneUse() &&
351 cast<Instruction>(Inst->use_back())->getParent() == BB &&
352 !isa<PHINode>(Inst->use_back())) continue;
354 // If this is an alloca in the entry block, it's not a real register
356 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
357 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
360 // Avoid iterator invalidation by copying users to a temporary vector.
361 SmallVector<Instruction*,16> Users;
362 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
364 Instruction *User = cast<Instruction>(*UI);
365 if (User->getParent() != BB || isa<PHINode>(User))
366 Users.push_back(User);
369 // Scan all of the uses and see if the live range is live across an unwind
370 // edge. If we find a use live across an invoke edge, create an alloca
371 // and spill the value.
372 std::set<InvokeInst*> InvokesWithStoreInserted;
374 // Find all of the blocks that this value is live in.
375 std::set<BasicBlock*> LiveBBs;
376 LiveBBs.insert(Inst->getParent());
377 while (!Users.empty()) {
378 Instruction *U = Users.back();
381 if (!isa<PHINode>(U)) {
382 MarkBlocksLiveIn(U->getParent(), LiveBBs);
384 // Uses for a PHI node occur in their predecessor block.
385 PHINode *PN = cast<PHINode>(U);
386 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
387 if (PN->getIncomingValue(i) == Inst)
388 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
392 // Now that we know all of the blocks that this thing is live in, see if
393 // it includes any of the unwind locations.
394 bool NeedsSpill = false;
395 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
396 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
397 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
402 // If we decided we need a spill, do it.
405 DemoteRegToStack(*Inst, true);
410 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
411 SmallVector<ReturnInst*,16> Returns;
412 SmallVector<UnwindInst*,16> Unwinds;
413 SmallVector<InvokeInst*,16> Invokes;
415 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
416 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
417 // Remember all return instructions in case we insert an invoke into this
419 Returns.push_back(RI);
420 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
421 Invokes.push_back(II);
422 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
423 Unwinds.push_back(UI);
426 if (Unwinds.empty() && Invokes.empty()) return false;
428 NumInvokes += Invokes.size();
429 NumUnwinds += Unwinds.size();
431 // TODO: This is not an optimal way to do this. In particular, this always
432 // inserts setjmp calls into the entries of functions with invoke instructions
433 // even though there are possibly paths through the function that do not
434 // execute any invokes. In particular, for functions with early exits, e.g.
435 // the 'addMove' method in hexxagon, it would be nice to not have to do the
436 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
437 // would not be too hard to do.
439 // If we have an invoke instruction, insert a setjmp that dominates all
440 // invokes. After the setjmp, use a cond branch that goes to the original
441 // code path on zero, and to a designated 'catch' block of nonzero.
442 Value *OldJmpBufPtr = 0;
443 if (!Invokes.empty()) {
444 // First thing we need to do is scan the whole function for values that are
445 // live across unwind edges. Each value that is live across an unwind edge
446 // we spill into a stack location, guaranteeing that there is nothing live
447 // across the unwind edge. This process also splits all critical edges
448 // coming out of invoke's.
449 splitLiveRangesLiveAcrossInvokes(Invokes);
451 BasicBlock *EntryBB = F.begin();
453 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
454 // that needs to be restored on all exits from the function. This is an
455 // alloca because the value needs to be live across invokes.
456 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
458 new AllocaInst(JBLinkTy, 0, Align,
459 "jblink", F.begin()->begin());
461 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
462 ConstantInt::get(Type::getInt32Ty(F.getContext()), 1) };
463 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
465 EntryBB->getTerminator());
467 // Copy the JBListHead to the alloca.
468 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
469 EntryBB->getTerminator());
470 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
472 // Add the new jumpbuf to the list.
473 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
475 // Create the catch block. The catch block is basically a big switch
476 // statement that goes to all of the invoke catch blocks.
477 BasicBlock *CatchBB =
478 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
480 // Create an alloca which keeps track of the stack pointer before every
481 // invoke, this allows us to properly restore the stack pointer after
483 AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
484 "stackptr", EntryBB->begin());
486 // Create an alloca which keeps track of which invoke is currently
487 // executing. For normal calls it contains zero.
488 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
489 "invokenum",EntryBB->begin());
490 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
491 InvokeNum, true, EntryBB->getTerminator());
493 // Insert a load in the Catch block, and a switch on its value. By default,
494 // we go to a block that just does an unwind (which is the correct action
495 // for a standard call).
496 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
497 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
499 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
500 SwitchInst *CatchSwitch =
501 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
503 // Now that things are set up, insert the setjmp call itself.
505 // Split the entry block to insert the conditional branch for the setjmp.
506 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
509 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
510 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, &Idx[0], &Idx[2],
512 EntryBB->getTerminator());
513 JmpBufPtr = new BitCastInst(JmpBufPtr,
514 Type::getInt8PtrTy(F.getContext()),
515 "tmp", EntryBB->getTerminator());
516 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
517 EntryBB->getTerminator());
519 // Compare the return value to zero.
520 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
521 ICmpInst::ICMP_EQ, SJRet,
522 Constant::getNullValue(SJRet->getType()),
524 // Nuke the uncond branch.
525 EntryBB->getTerminator()->eraseFromParent();
527 // Put in a new condbranch in its place.
528 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
530 // At this point, we are all set up, rewrite each invoke instruction.
531 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
532 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
535 // We know that there is at least one unwind.
537 // Create three new blocks, the block to load the jmpbuf ptr and compare
538 // against null, the block to do the longjmp, and the error block for if it
539 // is null. Add them at the end of the function because they are not hot.
540 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
542 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
543 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
545 // If this function contains an invoke, restore the old jumpbuf ptr.
548 // Before the return, insert a copy from the saved value to the new value.
549 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
550 new StoreInst(BufPtr, JBListHead, UnwindHandler);
552 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
555 // Load the JBList, if it's null, then there was no catch!
556 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
557 Constant::getNullValue(BufPtr->getType()),
559 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
561 // Create the block to do the longjmp.
562 // Get a pointer to the jmpbuf and longjmp.
563 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
564 ConstantInt::get(Type::getInt32Ty(F.getContext()), 0) };
565 Idx[0] = GetElementPtrInst::Create(BufPtr, &Idx[0], &Idx[2], "JmpBuf",
567 Idx[0] = new BitCastInst(Idx[0],
568 Type::getInt8PtrTy(F.getContext()),
570 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
571 CallInst::Create(LongJmpFn, &Idx[0], &Idx[2], "", UnwindBlock);
572 new UnreachableInst(F.getContext(), UnwindBlock);
574 // Set up the term block ("throw without a catch").
575 new UnreachableInst(F.getContext(), TermBlock);
577 // Insert a call to abort()
578 CallInst::Create(AbortFn, "",
579 TermBlock->getTerminator())->setTailCall();
582 // Replace all unwinds with a branch to the unwind handler.
583 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
584 BranchInst::Create(UnwindHandler, Unwinds[i]);
585 Unwinds[i]->eraseFromParent();
588 // Finally, for any returns from this function, if this function contains an
589 // invoke, restore the old jmpbuf pointer to its input value.
591 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
592 ReturnInst *R = Returns[i];
594 // Before the return, insert a copy from the saved value to the new value.
595 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
596 new StoreInst(OldBuf, JBListHead, true, R);
603 bool LowerInvoke::runOnFunction(Function &F) {
604 if (useExpensiveEHSupport)
605 return insertExpensiveEHSupport(F);
607 return insertCheapEHSupport(F);