1 //===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Constants.h"
39 #include "llvm/DerivedTypes.h"
40 #include "llvm/Instructions.h"
41 #include "llvm/Module.h"
42 #include "llvm/Pass.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/Local.h"
45 #include "llvm/ADT/Statistic.h"
46 #include "llvm/Support/CommandLine.h"
47 #include "llvm/Support/Compiler.h"
48 #include "llvm/Target/TargetLowering.h"
53 Statistic<> NumInvokes("lowerinvoke", "Number of invokes replaced");
54 Statistic<> NumUnwinds("lowerinvoke", "Number of unwinds replaced");
55 Statistic<> NumSpilled("lowerinvoke",
56 "Number of registers live across unwind edges");
57 cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
58 cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
60 class VISIBILITY_HIDDEN LowerInvoke : public FunctionPass {
61 // Used for both models.
65 unsigned AbortMessageLength;
67 // Used for expensive EH support.
69 GlobalVariable *JBListHead;
70 Function *SetJmpFn, *LongJmpFn;
72 // We peek in TLI to grab the target's jmp_buf size and alignment
73 const TargetLowering *TLI;
76 LowerInvoke(const TargetLowering *tli = NULL) : TLI(tli) { }
77 bool doInitialization(Module &M);
78 bool runOnFunction(Function &F);
80 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
81 // This is a cluster of orthogonal Transforms
82 AU.addPreservedID(PromoteMemoryToRegisterID);
83 AU.addPreservedID(LowerSelectID);
84 AU.addPreservedID(LowerSwitchID);
85 AU.addPreservedID(LowerAllocationsID);
89 void createAbortMessage();
90 void writeAbortMessage(Instruction *IB);
91 bool insertCheapEHSupport(Function &F);
92 void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
93 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
94 AllocaInst *InvokeNum, SwitchInst *CatchSwitch);
95 bool insertExpensiveEHSupport(Function &F);
98 RegisterPass<LowerInvoke>
99 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
102 const PassInfo *llvm::LowerInvokePassID = X.getPassInfo();
104 // Public Interface To the LowerInvoke pass.
105 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
106 return new LowerInvoke(TLI);
109 // doInitialization - Make sure that there is a prototype for abort in the
111 bool LowerInvoke::doInitialization(Module &M) {
112 const Type *VoidPtrTy = PointerType::get(Type::SByteTy);
114 if (ExpensiveEHSupport) {
115 // Insert a type for the linked list of jump buffers.
116 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
117 JBSize = JBSize ? JBSize : 200;
118 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
120 { // The type is recursive, so use a type holder.
121 std::vector<const Type*> Elements;
122 Elements.push_back(JmpBufTy);
123 OpaqueType *OT = OpaqueType::get();
124 Elements.push_back(PointerType::get(OT));
125 PATypeHolder JBLType(StructType::get(Elements));
126 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
127 JBLinkTy = JBLType.get();
128 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
131 const Type *PtrJBList = PointerType::get(JBLinkTy);
133 // Now that we've done that, insert the jmpbuf list head global, unless it
135 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
136 JBListHead = new GlobalVariable(PtrJBList, false,
137 GlobalValue::LinkOnceLinkage,
138 Constant::getNullValue(PtrJBList),
139 "llvm.sjljeh.jblist", &M);
141 SetJmpFn = M.getOrInsertFunction("llvm.setjmp", Type::IntTy,
142 PointerType::get(JmpBufTy), (Type *)0);
143 LongJmpFn = M.getOrInsertFunction("llvm.longjmp", Type::VoidTy,
144 PointerType::get(JmpBufTy),
145 Type::IntTy, (Type *)0);
148 // We need the 'write' and 'abort' functions for both models.
149 AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, (Type *)0);
151 // Unfortunately, 'write' can end up being prototyped in several different
152 // ways. If the user defines a three (or more) operand function named 'write'
153 // we will use their prototype. We _do not_ want to insert another instance
154 // of a write prototype, because we don't know that the funcresolve pass will
155 // run after us. If there is a definition of a write function, but it's not
156 // suitable for our uses, we just don't emit write calls. If there is no
157 // write prototype at all, we just add one.
158 if (Function *WF = M.getNamedFunction("write")) {
159 if (WF->getFunctionType()->getNumParams() > 3 ||
160 WF->getFunctionType()->isVarArg())
165 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::IntTy,
166 VoidPtrTy, Type::IntTy, (Type *)0);
171 void LowerInvoke::createAbortMessage() {
172 Module &M = *WriteFn->getParent();
173 if (ExpensiveEHSupport) {
174 // The abort message for expensive EH support tells the user that the
175 // program 'unwound' without an 'invoke' instruction.
177 ConstantArray::get("ERROR: Exception thrown, but not caught!\n");
178 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
180 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
181 GlobalValue::InternalLinkage,
182 Msg, "abortmsg", &M);
183 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::IntTy));
184 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx);
186 // The abort message for cheap EH support tells the user that EH is not
189 ConstantArray::get("Exception handler needed, but not enabled. Recompile"
190 " program with -enable-correct-eh-support.\n");
191 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
193 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
194 GlobalValue::InternalLinkage,
195 Msg, "abortmsg", &M);
196 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::IntTy));
197 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx);
202 void LowerInvoke::writeAbortMessage(Instruction *IB) {
204 if (AbortMessage == 0) createAbortMessage();
206 // These are the arguments we WANT...
207 std::vector<Value*> Args;
208 Args.push_back(ConstantInt::get(Type::IntTy, 2));
209 Args.push_back(AbortMessage);
210 Args.push_back(ConstantInt::get(Type::IntTy, AbortMessageLength));
212 // If the actual declaration of write disagrees, insert casts as
214 const FunctionType *FT = WriteFn->getFunctionType();
215 unsigned NumArgs = FT->getNumParams();
216 for (unsigned i = 0; i != 3; ++i)
217 if (i < NumArgs && FT->getParamType(i) != Args[i]->getType())
218 Args[i] = ConstantExpr::getCast(cast<Constant>(Args[i]),
219 FT->getParamType(i));
221 (new CallInst(WriteFn, Args, "", 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 // Insert a normal call instruction...
230 std::string Name = II->getName(); II->setName("");
231 CallInst *NewCall = new CallInst(II->getCalledValue(),
232 std::vector<Value*>(II->op_begin()+3,
233 II->op_end()), Name, II);
234 NewCall->setCallingConv(II->getCallingConv());
235 II->replaceAllUsesWith(NewCall);
237 // Insert an unconditional branch to the normal destination.
238 new BranchInst(II->getNormalDest(), II);
240 // Remove any PHI node entries from the exception destination.
241 II->getUnwindDest()->removePredecessor(BB);
243 // Remove the invoke instruction now.
244 BB->getInstList().erase(II);
246 ++NumInvokes; Changed = true;
247 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
248 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
249 writeAbortMessage(UI);
251 // Insert a call to abort()
252 (new CallInst(AbortFn, std::vector<Value*>(), "", UI))->setTailCall();
254 // Insert a return instruction. This really should be a "barrier", as it
256 new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 :
257 Constant::getNullValue(F.getReturnType()), UI);
259 // Remove the unwind instruction now.
260 BB->getInstList().erase(UI);
262 ++NumUnwinds; Changed = true;
267 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
268 /// specified invoke instruction with a call.
269 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
270 AllocaInst *InvokeNum,
271 SwitchInst *CatchSwitch) {
272 ConstantInt *InvokeNoC = ConstantInt::get(Type::UIntTy, InvokeNo);
274 // Insert a store of the invoke num before the invoke and store zero into the
275 // location afterward.
276 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
278 BasicBlock::iterator NI = II->getNormalDest()->begin();
279 while (isa<PHINode>(NI)) ++NI;
281 new StoreInst(Constant::getNullValue(Type::UIntTy), InvokeNum, false, NI);
283 // Add a switch case to our unwind block.
284 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
286 // Insert a normal call instruction.
287 std::string Name = II->getName(); II->setName("");
288 CallInst *NewCall = new CallInst(II->getCalledValue(),
289 std::vector<Value*>(II->op_begin()+3,
292 NewCall->setCallingConv(II->getCallingConv());
293 II->replaceAllUsesWith(NewCall);
295 // Replace the invoke with an uncond branch.
296 new BranchInst(II->getNormalDest(), NewCall->getParent());
297 II->eraseFromParent();
300 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
301 /// we reach blocks we've already seen.
302 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
303 if (!LiveBBs.insert(BB).second) return; // already been here.
305 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
306 MarkBlocksLiveIn(*PI, LiveBBs);
309 // First thing we need to do is scan the whole function for values that are
310 // live across unwind edges. Each value that is live across an unwind edge
311 // we spill into a stack location, guaranteeing that there is nothing live
312 // across the unwind edge. This process also splits all critical edges
313 // coming out of invoke's.
315 splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
316 // First step, split all critical edges from invoke instructions.
317 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
318 InvokeInst *II = Invokes[i];
319 SplitCriticalEdge(II, 0, this);
320 SplitCriticalEdge(II, 1, this);
321 assert(!isa<PHINode>(II->getNormalDest()) &&
322 !isa<PHINode>(II->getUnwindDest()) &&
323 "critical edge splitting left single entry phi nodes?");
326 Function *F = Invokes.back()->getParent()->getParent();
328 // To avoid having to handle incoming arguments specially, we lower each arg
329 // to a copy instruction in the entry block. This ensure that the argument
330 // value itself cannot be live across the entry block.
331 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
332 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
333 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
334 ++AfterAllocaInsertPt;
335 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
337 CastInst *NC = new CastInst(AI, AI->getType(), AI->getName()+".tmp",
338 AfterAllocaInsertPt);
339 AI->replaceAllUsesWith(NC);
340 NC->setOperand(0, AI);
343 // Finally, scan the code looking for instructions with bad live ranges.
344 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
345 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
346 // Ignore obvious cases we don't have to handle. In particular, most
347 // instructions either have no uses or only have a single use inside the
348 // current block. Ignore them quickly.
349 Instruction *Inst = II;
350 if (Inst->use_empty()) continue;
351 if (Inst->hasOneUse() &&
352 cast<Instruction>(Inst->use_back())->getParent() == BB &&
353 !isa<PHINode>(Inst->use_back())) continue;
355 // If this is an alloca in the entry block, it's not a real register
357 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
358 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
361 // Avoid iterator invalidation by copying users to a temporary vector.
362 std::vector<Instruction*> Users;
363 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
365 Instruction *User = cast<Instruction>(*UI);
366 if (User->getParent() != BB || isa<PHINode>(User))
367 Users.push_back(User);
370 // Scan all of the uses and see if the live range is live across an unwind
371 // edge. If we find a use live across an invoke edge, create an alloca
372 // and spill the value.
373 AllocaInst *SpillLoc = 0;
374 std::set<InvokeInst*> InvokesWithStoreInserted;
376 // Find all of the blocks that this value is live in.
377 std::set<BasicBlock*> LiveBBs;
378 LiveBBs.insert(Inst->getParent());
379 while (!Users.empty()) {
380 Instruction *U = Users.back();
383 if (!isa<PHINode>(U)) {
384 MarkBlocksLiveIn(U->getParent(), LiveBBs);
386 // Uses for a PHI node occur in their predecessor block.
387 PHINode *PN = cast<PHINode>(U);
388 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
389 if (PN->getIncomingValue(i) == Inst)
390 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
394 // Now that we know all of the blocks that this thing is live in, see if
395 // it includes any of the unwind locations.
396 bool NeedsSpill = false;
397 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
398 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
399 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
404 // If we decided we need a spill, do it.
407 DemoteRegToStack(*Inst, true);
412 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
413 std::vector<ReturnInst*> Returns;
414 std::vector<UnwindInst*> Unwinds;
415 std::vector<InvokeInst*> Invokes;
417 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
418 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
419 // Remember all return instructions in case we insert an invoke into this
421 Returns.push_back(RI);
422 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
423 Invokes.push_back(II);
424 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
425 Unwinds.push_back(UI);
428 if (Unwinds.empty() && Invokes.empty()) return false;
430 NumInvokes += Invokes.size();
431 NumUnwinds += Unwinds.size();
433 // TODO: This is not an optimal way to do this. In particular, this always
434 // inserts setjmp calls into the entries of functions with invoke instructions
435 // even though there are possibly paths through the function that do not
436 // execute any invokes. In particular, for functions with early exits, e.g.
437 // the 'addMove' method in hexxagon, it would be nice to not have to do the
438 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
439 // would not be too hard to do.
441 // If we have an invoke instruction, insert a setjmp that dominates all
442 // invokes. After the setjmp, use a cond branch that goes to the original
443 // code path on zero, and to a designated 'catch' block of nonzero.
444 Value *OldJmpBufPtr = 0;
445 if (!Invokes.empty()) {
446 // First thing we need to do is scan the whole function for values that are
447 // live across unwind edges. Each value that is live across an unwind edge
448 // we spill into a stack location, guaranteeing that there is nothing live
449 // across the unwind edge. This process also splits all critical edges
450 // coming out of invoke's.
451 splitLiveRangesLiveAcrossInvokes(Invokes);
453 BasicBlock *EntryBB = F.begin();
455 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
456 // that needs to be restored on all exits from the function. This is an
457 // alloca because the value needs to be live across invokes.
458 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
460 new AllocaInst(JBLinkTy, 0, Align, "jblink", F.begin()->begin());
462 std::vector<Value*> Idx;
463 Idx.push_back(Constant::getNullValue(Type::IntTy));
464 Idx.push_back(ConstantInt::get(Type::UIntTy, 1));
465 OldJmpBufPtr = new GetElementPtrInst(JmpBuf, Idx, "OldBuf",
466 EntryBB->getTerminator());
468 // Copy the JBListHead to the alloca.
469 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
470 EntryBB->getTerminator());
471 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
473 // Add the new jumpbuf to the list.
474 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
476 // Create the catch block. The catch block is basically a big switch
477 // statement that goes to all of the invoke catch blocks.
478 BasicBlock *CatchBB = new BasicBlock("setjmp.catch", &F);
480 // Create an alloca which keeps track of which invoke is currently
481 // executing. For normal calls it contains zero.
482 AllocaInst *InvokeNum = new AllocaInst(Type::UIntTy, 0, "invokenum",
484 new StoreInst(ConstantInt::get(Type::UIntTy, 0), InvokeNum, true,
485 EntryBB->getTerminator());
487 // Insert a load in the Catch block, and a switch on its value. By default,
488 // we go to a block that just does an unwind (which is the correct action
489 // for a standard call).
490 BasicBlock *UnwindBB = new BasicBlock("unwindbb", &F);
491 Unwinds.push_back(new UnwindInst(UnwindBB));
493 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
494 SwitchInst *CatchSwitch =
495 new SwitchInst(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
497 // Now that things are set up, insert the setjmp call itself.
499 // Split the entry block to insert the conditional branch for the setjmp.
500 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
503 Idx[1] = ConstantInt::get(Type::UIntTy, 0);
504 Value *JmpBufPtr = new GetElementPtrInst(JmpBuf, Idx, "TheJmpBuf",
505 EntryBB->getTerminator());
506 Value *SJRet = new CallInst(SetJmpFn, JmpBufPtr, "sjret",
507 EntryBB->getTerminator());
509 // Compare the return value to zero.
510 Value *IsNormal = BinaryOperator::createSetEQ(SJRet,
511 Constant::getNullValue(SJRet->getType()),
512 "notunwind", EntryBB->getTerminator());
513 // Nuke the uncond branch.
514 EntryBB->getTerminator()->eraseFromParent();
516 // Put in a new condbranch in its place.
517 new BranchInst(ContBlock, CatchBB, IsNormal, EntryBB);
519 // At this point, we are all set up, rewrite each invoke instruction.
520 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
521 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch);
524 // We know that there is at least one unwind.
526 // Create three new blocks, the block to load the jmpbuf ptr and compare
527 // against null, the block to do the longjmp, and the error block for if it
528 // is null. Add them at the end of the function because they are not hot.
529 BasicBlock *UnwindHandler = new BasicBlock("dounwind", &F);
530 BasicBlock *UnwindBlock = new BasicBlock("unwind", &F);
531 BasicBlock *TermBlock = new BasicBlock("unwinderror", &F);
533 // If this function contains an invoke, restore the old jumpbuf ptr.
536 // Before the return, insert a copy from the saved value to the new value.
537 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
538 new StoreInst(BufPtr, JBListHead, UnwindHandler);
540 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
543 // Load the JBList, if it's null, then there was no catch!
544 Value *NotNull = BinaryOperator::createSetNE(BufPtr,
545 Constant::getNullValue(BufPtr->getType()),
546 "notnull", UnwindHandler);
547 new BranchInst(UnwindBlock, TermBlock, NotNull, UnwindHandler);
549 // Create the block to do the longjmp.
550 // Get a pointer to the jmpbuf and longjmp.
551 std::vector<Value*> Idx;
552 Idx.push_back(Constant::getNullValue(Type::IntTy));
553 Idx.push_back(ConstantInt::get(Type::UIntTy, 0));
554 Idx[0] = new GetElementPtrInst(BufPtr, Idx, "JmpBuf", UnwindBlock);
555 Idx[1] = ConstantInt::get(Type::IntTy, 1);
556 new CallInst(LongJmpFn, Idx, "", UnwindBlock);
557 new UnreachableInst(UnwindBlock);
559 // Set up the term block ("throw without a catch").
560 new UnreachableInst(TermBlock);
562 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
563 writeAbortMessage(TermBlock->getTerminator());
565 // Insert a call to abort()
566 (new CallInst(AbortFn, std::vector<Value*>(), "",
567 TermBlock->getTerminator()))->setTailCall();
570 // Replace all unwinds with a branch to the unwind handler.
571 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
572 new BranchInst(UnwindHandler, Unwinds[i]);
573 Unwinds[i]->eraseFromParent();
576 // Finally, for any returns from this function, if this function contains an
577 // invoke, restore the old jmpbuf pointer to its input value.
579 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
580 ReturnInst *R = Returns[i];
582 // Before the return, insert a copy from the saved value to the new value.
583 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
584 new StoreInst(OldBuf, JBListHead, true, R);
591 bool LowerInvoke::runOnFunction(Function &F) {
592 if (ExpensiveEHSupport)
593 return insertExpensiveEHSupport(F);
595 return insertCheapEHSupport(F);