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/Statistic.h"
49 #include "llvm/Support/CommandLine.h"
50 #include "llvm/Target/TargetLowering.h"
55 STATISTIC(NumInvokes, "Number of invokes replaced");
56 STATISTIC(NumUnwinds, "Number of unwinds replaced");
57 STATISTIC(NumSpilled, "Number of registers live across unwind edges");
59 static cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
60 cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
63 class LowerInvoke : public FunctionPass {
64 // Used for both models.
68 unsigned AbortMessageLength;
70 // Used for expensive EH support.
72 GlobalVariable *JBListHead;
73 Constant *SetJmpFn, *LongJmpFn;
75 // We peek in TLI to grab the target's jmp_buf size and alignment
76 const TargetLowering *TLI;
79 static char ID; // Pass identification, replacement for typeid
80 explicit LowerInvoke(const TargetLowering *tli = NULL)
81 : FunctionPass(&ID), TLI(tli) { }
82 bool doInitialization(Module &M);
83 bool runOnFunction(Function &F);
85 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
86 // This is a cluster of orthogonal Transforms
87 AU.addPreservedID(PromoteMemoryToRegisterID);
88 AU.addPreservedID(LowerSwitchID);
92 void createAbortMessage(Module *M);
93 void writeAbortMessage(Instruction *IB);
94 bool insertCheapEHSupport(Function &F);
95 void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
96 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
97 AllocaInst *InvokeNum, 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);
113 // doInitialization - Make sure that there is a prototype for abort in the
115 bool LowerInvoke::doInitialization(Module &M) {
116 const Type *VoidPtrTy =
117 Type::getInt8PtrTy(M.getContext());
119 if (ExpensiveEHSupport) {
120 // Insert a type for the linked list of jump buffers.
121 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
122 JBSize = JBSize ? JBSize : 200;
123 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
125 { // The type is recursive, so use a type holder.
126 std::vector<const Type*> Elements;
127 Elements.push_back(JmpBufTy);
128 OpaqueType *OT = OpaqueType::get(M.getContext());
129 Elements.push_back(PointerType::getUnqual(OT));
130 PATypeHolder JBLType(StructType::get(M.getContext(), Elements));
131 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
132 JBLinkTy = JBLType.get();
133 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
136 const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
138 // Now that we've done that, insert the jmpbuf list head global, unless it
140 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
141 JBListHead = new GlobalVariable(M, PtrJBList, false,
142 GlobalValue::LinkOnceAnyLinkage,
143 Constant::getNullValue(PtrJBList),
144 "llvm.sjljeh.jblist");
147 // VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
148 // so it looks like Intrinsic::_setjmp
149 #if defined(_MSC_VER) && defined(setjmp)
150 #define setjmp_undefined_for_visual_studio
154 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
156 #if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
157 // let's return it to _setjmp state in case anyone ever needs it after this
158 // point under VisualStudio
159 #define setjmp _setjmp
162 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
165 // We need the 'write' and 'abort' functions for both models.
166 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
168 #if 0 // "write" is Unix-specific.. code is going away soon anyway.
169 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
170 VoidPtrTy, Type::Int32Ty, (Type *)0);
177 void LowerInvoke::createAbortMessage(Module *M) {
178 if (ExpensiveEHSupport) {
179 // The abort message for expensive EH support tells the user that the
180 // program 'unwound' without an 'invoke' instruction.
182 ConstantArray::get(M->getContext(),
183 "ERROR: Exception thrown, but not caught!\n");
184 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
186 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
187 GlobalValue::InternalLinkage,
189 std::vector<Constant*> GEPIdx(2,
190 Constant::getNullValue(Type::getInt32Ty(M->getContext())));
191 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
193 // The abort message for cheap EH support tells the user that EH is not
196 ConstantArray::get(M->getContext(),
197 "Exception handler needed, but not enabled."
198 "Recompile program with -enable-correct-eh-support.\n");
199 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
201 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
202 GlobalValue::InternalLinkage,
204 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(
205 Type::getInt32Ty(M->getContext())));
206 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
211 void LowerInvoke::writeAbortMessage(Instruction *IB) {
213 if (AbortMessage == 0)
214 createAbortMessage(IB->getParent()->getParent()->getParent());
216 // These are the arguments we WANT...
218 Args[0] = ConstantInt::get(Type::Int32Ty, 2);
219 Args[1] = AbortMessage;
220 Args[2] = ConstantInt::get(Type::Int32Ty, AbortMessageLength);
221 (new CallInst(WriteFn, Args, 3, "", IB))->setTailCall();
225 bool LowerInvoke::insertCheapEHSupport(Function &F) {
226 bool Changed = false;
227 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
228 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
229 std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
230 // Insert a normal call instruction...
231 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
232 CallArgs.begin(), CallArgs.end(), "",II);
233 NewCall->takeName(II);
234 NewCall->setCallingConv(II->getCallingConv());
235 NewCall->setAttributes(II->getAttributes());
236 II->replaceAllUsesWith(NewCall);
238 // Insert an unconditional branch to the normal destination.
239 BranchInst::Create(II->getNormalDest(), II);
241 // Remove any PHI node entries from the exception destination.
242 II->getUnwindDest()->removePredecessor(BB);
244 // Remove the invoke instruction now.
245 BB->getInstList().erase(II);
247 ++NumInvokes; Changed = true;
248 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
249 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
250 writeAbortMessage(UI);
252 // Insert a call to abort()
253 CallInst::Create(AbortFn, "", UI)->setTailCall();
255 // Insert a return instruction. This really should be a "barrier", as it
257 ReturnInst::Create(F.getContext(),
258 F.getReturnType()->isVoidTy() ?
259 0 : Constant::getNullValue(F.getReturnType()), UI);
261 // Remove the unwind instruction now.
262 BB->getInstList().erase(UI);
264 ++NumUnwinds; Changed = true;
269 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
270 /// specified invoke instruction with a call.
271 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
272 AllocaInst *InvokeNum,
273 SwitchInst *CatchSwitch) {
274 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
277 // If the unwind edge has phi nodes, split the edge.
278 if (isa<PHINode>(II->getUnwindDest()->begin())) {
279 SplitCriticalEdge(II, 1, this);
281 // If there are any phi nodes left, they must have a single predecessor.
282 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
283 PN->replaceAllUsesWith(PN->getIncomingValue(0));
284 PN->eraseFromParent();
288 // Insert a store of the invoke num before the invoke and store zero into the
289 // location afterward.
290 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
292 BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
294 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
295 InvokeNum, false, NI);
297 // Add a switch case to our unwind block.
298 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
300 // Insert a normal call instruction.
301 std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
302 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
303 CallArgs.begin(), CallArgs.end(), "",
305 NewCall->takeName(II);
306 NewCall->setCallingConv(II->getCallingConv());
307 NewCall->setAttributes(II->getAttributes());
308 II->replaceAllUsesWith(NewCall);
310 // Replace the invoke with an uncond branch.
311 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
312 II->eraseFromParent();
315 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
316 /// we reach blocks we've already seen.
317 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
318 if (!LiveBBs.insert(BB).second) return; // already been here.
320 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
321 MarkBlocksLiveIn(*PI, LiveBBs);
324 // First thing we need to do is scan the whole function for values that are
325 // live across unwind edges. Each value that is live across an unwind edge
326 // we spill into a stack location, guaranteeing that there is nothing live
327 // across the unwind edge. This process also splits all critical edges
328 // coming out of invoke's.
330 splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
331 // First step, split all critical edges from invoke instructions.
332 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
333 InvokeInst *II = Invokes[i];
334 SplitCriticalEdge(II, 0, this);
335 SplitCriticalEdge(II, 1, this);
336 assert(!isa<PHINode>(II->getNormalDest()) &&
337 !isa<PHINode>(II->getUnwindDest()) &&
338 "critical edge splitting left single entry phi nodes?");
341 Function *F = Invokes.back()->getParent()->getParent();
343 // To avoid having to handle incoming arguments specially, we lower each arg
344 // to a copy instruction in the entry block. This ensures that the argument
345 // value itself cannot be live across the entry block.
346 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
347 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
348 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
349 ++AfterAllocaInsertPt;
350 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
352 // This is always a no-op cast because we're casting AI to AI->getType() so
353 // src and destination types are identical. BitCast is the only possibility.
354 CastInst *NC = new BitCastInst(
355 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
356 AI->replaceAllUsesWith(NC);
357 // Normally its is forbidden to replace a CastInst's operand because it
358 // could cause the opcode to reflect an illegal conversion. However, we're
359 // replacing it here with the same value it was constructed with to simply
361 NC->setOperand(0, AI);
364 // Finally, scan the code looking for instructions with bad live ranges.
365 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
366 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
367 // Ignore obvious cases we don't have to handle. In particular, most
368 // instructions either have no uses or only have a single use inside the
369 // current block. Ignore them quickly.
370 Instruction *Inst = II;
371 if (Inst->use_empty()) continue;
372 if (Inst->hasOneUse() &&
373 cast<Instruction>(Inst->use_back())->getParent() == BB &&
374 !isa<PHINode>(Inst->use_back())) continue;
376 // If this is an alloca in the entry block, it's not a real register
378 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
379 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
382 // Avoid iterator invalidation by copying users to a temporary vector.
383 std::vector<Instruction*> Users;
384 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
386 Instruction *User = cast<Instruction>(*UI);
387 if (User->getParent() != BB || isa<PHINode>(User))
388 Users.push_back(User);
391 // Scan all of the uses and see if the live range is live across an unwind
392 // edge. If we find a use live across an invoke edge, create an alloca
393 // and spill the value.
394 std::set<InvokeInst*> InvokesWithStoreInserted;
396 // Find all of the blocks that this value is live in.
397 std::set<BasicBlock*> LiveBBs;
398 LiveBBs.insert(Inst->getParent());
399 while (!Users.empty()) {
400 Instruction *U = Users.back();
403 if (!isa<PHINode>(U)) {
404 MarkBlocksLiveIn(U->getParent(), LiveBBs);
406 // Uses for a PHI node occur in their predecessor block.
407 PHINode *PN = cast<PHINode>(U);
408 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
409 if (PN->getIncomingValue(i) == Inst)
410 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
414 // Now that we know all of the blocks that this thing is live in, see if
415 // it includes any of the unwind locations.
416 bool NeedsSpill = false;
417 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
418 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
419 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
424 // If we decided we need a spill, do it.
427 DemoteRegToStack(*Inst, true);
432 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
433 std::vector<ReturnInst*> Returns;
434 std::vector<UnwindInst*> Unwinds;
435 std::vector<InvokeInst*> Invokes;
437 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
438 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
439 // Remember all return instructions in case we insert an invoke into this
441 Returns.push_back(RI);
442 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
443 Invokes.push_back(II);
444 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
445 Unwinds.push_back(UI);
448 if (Unwinds.empty() && Invokes.empty()) return false;
450 NumInvokes += Invokes.size();
451 NumUnwinds += Unwinds.size();
453 // TODO: This is not an optimal way to do this. In particular, this always
454 // inserts setjmp calls into the entries of functions with invoke instructions
455 // even though there are possibly paths through the function that do not
456 // execute any invokes. In particular, for functions with early exits, e.g.
457 // the 'addMove' method in hexxagon, it would be nice to not have to do the
458 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
459 // would not be too hard to do.
461 // If we have an invoke instruction, insert a setjmp that dominates all
462 // invokes. After the setjmp, use a cond branch that goes to the original
463 // code path on zero, and to a designated 'catch' block of nonzero.
464 Value *OldJmpBufPtr = 0;
465 if (!Invokes.empty()) {
466 // First thing we need to do is scan the whole function for values that are
467 // live across unwind edges. Each value that is live across an unwind edge
468 // we spill into a stack location, guaranteeing that there is nothing live
469 // across the unwind edge. This process also splits all critical edges
470 // coming out of invoke's.
471 splitLiveRangesLiveAcrossInvokes(Invokes);
473 BasicBlock *EntryBB = F.begin();
475 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
476 // that needs to be restored on all exits from the function. This is an
477 // alloca because the value needs to be live across invokes.
478 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
480 new AllocaInst(JBLinkTy, 0, Align,
481 "jblink", F.begin()->begin());
483 std::vector<Value*> Idx;
484 Idx.push_back(Constant::getNullValue(Type::getInt32Ty(F.getContext())));
485 Idx.push_back(ConstantInt::get(Type::getInt32Ty(F.getContext()), 1));
486 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
488 EntryBB->getTerminator());
490 // Copy the JBListHead to the alloca.
491 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
492 EntryBB->getTerminator());
493 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
495 // Add the new jumpbuf to the list.
496 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
498 // Create the catch block. The catch block is basically a big switch
499 // statement that goes to all of the invoke catch blocks.
500 BasicBlock *CatchBB =
501 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
503 // Create an alloca which keeps track of which invoke is currently
504 // executing. For normal calls it contains zero.
505 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
506 "invokenum",EntryBB->begin());
507 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
508 InvokeNum, true, EntryBB->getTerminator());
510 // Insert a load in the Catch block, and a switch on its value. By default,
511 // we go to a block that just does an unwind (which is the correct action
512 // for a standard call).
513 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
514 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
516 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
517 SwitchInst *CatchSwitch =
518 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
520 // Now that things are set up, insert the setjmp call itself.
522 // Split the entry block to insert the conditional branch for the setjmp.
523 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
526 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
527 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
529 EntryBB->getTerminator());
530 JmpBufPtr = new BitCastInst(JmpBufPtr,
531 Type::getInt8PtrTy(F.getContext()),
532 "tmp", EntryBB->getTerminator());
533 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
534 EntryBB->getTerminator());
536 // Compare the return value to zero.
537 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
538 ICmpInst::ICMP_EQ, SJRet,
539 Constant::getNullValue(SJRet->getType()),
541 // Nuke the uncond branch.
542 EntryBB->getTerminator()->eraseFromParent();
544 // Put in a new condbranch in its place.
545 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
547 // At this point, we are all set up, rewrite each invoke instruction.
548 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
549 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch);
552 // We know that there is at least one unwind.
554 // Create three new blocks, the block to load the jmpbuf ptr and compare
555 // against null, the block to do the longjmp, and the error block for if it
556 // is null. Add them at the end of the function because they are not hot.
557 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
559 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
560 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
562 // If this function contains an invoke, restore the old jumpbuf ptr.
565 // Before the return, insert a copy from the saved value to the new value.
566 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
567 new StoreInst(BufPtr, JBListHead, UnwindHandler);
569 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
572 // Load the JBList, if it's null, then there was no catch!
573 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
574 Constant::getNullValue(BufPtr->getType()),
576 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
578 // Create the block to do the longjmp.
579 // Get a pointer to the jmpbuf and longjmp.
580 std::vector<Value*> Idx;
581 Idx.push_back(Constant::getNullValue(Type::getInt32Ty(F.getContext())));
582 Idx.push_back(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0));
583 Idx[0] = GetElementPtrInst::Create(BufPtr, Idx.begin(), Idx.end(), "JmpBuf",
585 Idx[0] = new BitCastInst(Idx[0],
586 Type::getInt8PtrTy(F.getContext()),
588 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
589 CallInst::Create(LongJmpFn, Idx.begin(), Idx.end(), "", UnwindBlock);
590 new UnreachableInst(F.getContext(), UnwindBlock);
592 // Set up the term block ("throw without a catch").
593 new UnreachableInst(F.getContext(), TermBlock);
595 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
596 writeAbortMessage(TermBlock->getTerminator());
598 // Insert a call to abort()
599 CallInst::Create(AbortFn, "",
600 TermBlock->getTerminator())->setTailCall();
603 // Replace all unwinds with a branch to the unwind handler.
604 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
605 BranchInst::Create(UnwindHandler, Unwinds[i]);
606 Unwinds[i]->eraseFromParent();
609 // Finally, for any returns from this function, if this function contains an
610 // invoke, restore the old jmpbuf pointer to its input value.
612 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
613 ReturnInst *R = Returns[i];
615 // Before the return, insert a copy from the saved value to the new value.
616 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
617 new StoreInst(OldBuf, JBListHead, true, R);
624 bool LowerInvoke::runOnFunction(Function &F) {
625 if (ExpensiveEHSupport)
626 return insertExpensiveEHSupport(F);
628 return insertCheapEHSupport(F);