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/TargetTransformInfo.h"
49 #include "llvm/ADT/SmallVector.h"
50 #include "llvm/ADT/Statistic.h"
51 #include "llvm/Support/CommandLine.h"
56 STATISTIC(NumInvokes, "Number of invokes 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.
67 // Used for expensive EH support.
69 GlobalVariable *JBListHead;
70 Constant *SetJmpFn, *LongJmpFn, *StackSaveFn, *StackRestoreFn;
71 bool useExpensiveEHSupport;
73 // We peek in STTI to grab the target's jmp_buf size and alignment
74 const ScalarTargetTransformInfo *STTI;
77 static char ID; // Pass identification, replacement for typeid
78 explicit LowerInvoke(bool useExpensiveEHSupport = ExpensiveEHSupport)
79 : FunctionPass(ID), useExpensiveEHSupport(useExpensiveEHSupport),
81 initializeLowerInvokePass(*PassRegistry::getPassRegistry());
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() {
111 return new LowerInvoke(ExpensiveEHSupport);
113 FunctionPass *llvm::createLowerInvokePass(bool useExpensiveEHSupport) {
114 return new LowerInvoke(useExpensiveEHSupport);
117 // doInitialization - Make sure that there is a prototype for abort in the
119 bool LowerInvoke::doInitialization(Module &M) {
120 TargetTransformInfo *TTI = getAnalysisIfAvailable<TargetTransformInfo>();
122 STTI = TTI->getScalarTargetTransformInfo();
124 Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext());
125 if (useExpensiveEHSupport) {
126 // Insert a type for the linked list of jump buffers.
127 unsigned JBSize = STTI ? STTI->getJumpBufSize() : 0;
128 JBSize = JBSize ? JBSize : 200;
129 Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
131 JBLinkTy = StructType::create(M.getContext(), "llvm.sjljeh.jmpbufty");
132 Type *Elts[] = { JmpBufTy, PointerType::getUnqual(JBLinkTy) };
133 JBLinkTy->setBody(Elts);
135 Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
137 // Now that we've done that, insert the jmpbuf list head global, unless it
139 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
140 JBListHead = new GlobalVariable(M, PtrJBList, false,
141 GlobalValue::LinkOnceAnyLinkage,
142 Constant::getNullValue(PtrJBList),
143 "llvm.sjljeh.jblist");
146 // VisualStudio defines setjmp as _setjmp
147 #if defined(_MSC_VER) && defined(setjmp) && \
148 !defined(setjmp_undefined_for_msvc)
149 # pragma push_macro("setjmp")
151 # define setjmp_undefined_for_msvc
154 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
156 #if defined(_MSC_VER) && defined(setjmp_undefined_for_msvc)
157 // let's return it to _setjmp state
158 # pragma pop_macro("setjmp")
159 # undef setjmp_undefined_for_msvc
162 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
163 StackSaveFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
164 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
167 // We need the 'write' and 'abort' functions for both models.
168 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
173 bool LowerInvoke::insertCheapEHSupport(Function &F) {
174 bool Changed = false;
175 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
176 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
177 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
178 // Insert a normal call instruction...
179 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
181 NewCall->takeName(II);
182 NewCall->setCallingConv(II->getCallingConv());
183 NewCall->setAttributes(II->getAttributes());
184 NewCall->setDebugLoc(II->getDebugLoc());
185 II->replaceAllUsesWith(NewCall);
187 // Insert an unconditional branch to the normal destination.
188 BranchInst::Create(II->getNormalDest(), II);
190 // Remove any PHI node entries from the exception destination.
191 II->getUnwindDest()->removePredecessor(BB);
193 // Remove the invoke instruction now.
194 BB->getInstList().erase(II);
196 ++NumInvokes; Changed = true;
201 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
202 /// specified invoke instruction with a call.
203 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
204 AllocaInst *InvokeNum,
205 AllocaInst *StackPtr,
206 SwitchInst *CatchSwitch) {
207 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
210 // If the unwind edge has phi nodes, split the edge.
211 if (isa<PHINode>(II->getUnwindDest()->begin())) {
212 SplitCriticalEdge(II, 1, this);
214 // If there are any phi nodes left, they must have a single predecessor.
215 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
216 PN->replaceAllUsesWith(PN->getIncomingValue(0));
217 PN->eraseFromParent();
221 // Insert a store of the invoke num before the invoke and store zero into the
222 // location afterward.
223 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
225 // Insert a store of the stack ptr before the invoke, so we can restore it
226 // later in the exception case.
227 CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
228 new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
230 BasicBlock::iterator NI = II->getNormalDest()->getFirstInsertionPt();
232 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
233 InvokeNum, false, NI);
235 Instruction* StackPtrLoad =
236 new LoadInst(StackPtr, "stackptr.restore", true,
237 II->getUnwindDest()->getFirstInsertionPt());
238 CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
240 // Add a switch case to our unwind block.
241 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
243 // Insert a normal call instruction.
244 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
245 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
247 NewCall->takeName(II);
248 NewCall->setCallingConv(II->getCallingConv());
249 NewCall->setAttributes(II->getAttributes());
250 NewCall->setDebugLoc(II->getDebugLoc());
251 II->replaceAllUsesWith(NewCall);
253 // Replace the invoke with an uncond branch.
254 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
255 II->eraseFromParent();
258 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
259 /// we reach blocks we've already seen.
260 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
261 if (!LiveBBs.insert(BB).second) return; // already been here.
263 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
264 MarkBlocksLiveIn(*PI, LiveBBs);
267 // First thing we need to do is scan the whole function for values that are
268 // live across unwind edges. Each value that is live across an unwind edge
269 // we spill into a stack location, guaranteeing that there is nothing live
270 // across the unwind edge. This process also splits all critical edges
271 // coming out of invoke's.
273 splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
274 // First step, split all critical edges from invoke instructions.
275 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
276 InvokeInst *II = Invokes[i];
277 SplitCriticalEdge(II, 0, this);
278 SplitCriticalEdge(II, 1, this);
279 assert(!isa<PHINode>(II->getNormalDest()) &&
280 !isa<PHINode>(II->getUnwindDest()) &&
281 "critical edge splitting left single entry phi nodes?");
284 Function *F = Invokes.back()->getParent()->getParent();
286 // To avoid having to handle incoming arguments specially, we lower each arg
287 // to a copy instruction in the entry block. This ensures that the argument
288 // value itself cannot be live across the entry block.
289 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
290 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
291 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
292 ++AfterAllocaInsertPt;
293 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
295 Type *Ty = AI->getType();
296 // Aggregate types can't be cast, but are legal argument types, so we have
297 // to handle them differently. We use an extract/insert pair as a
298 // lightweight method to achieve the same goal.
299 if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
300 Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt);
301 Instruction *NI = InsertValueInst::Create(AI, EI, 0);
303 AI->replaceAllUsesWith(NI);
304 // Set the operand of the instructions back to the AllocaInst.
305 EI->setOperand(0, AI);
306 NI->setOperand(0, AI);
308 // This is always a no-op cast because we're casting AI to AI->getType()
309 // so src and destination types are identical. BitCast is the only
311 CastInst *NC = new BitCastInst(
312 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
313 AI->replaceAllUsesWith(NC);
314 // Set the operand of the cast instruction back to the AllocaInst.
315 // Normally it's forbidden to replace a CastInst's operand because it
316 // could cause the opcode to reflect an illegal conversion. However,
317 // we're replacing it here with the same value it was constructed with.
318 // We do this because the above replaceAllUsesWith() clobbered the
319 // operand, but we want this one to remain.
320 NC->setOperand(0, AI);
324 // Finally, scan the code looking for instructions with bad live ranges.
325 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
326 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
327 // Ignore obvious cases we don't have to handle. In particular, most
328 // instructions either have no uses or only have a single use inside the
329 // current block. Ignore them quickly.
330 Instruction *Inst = II;
331 if (Inst->use_empty()) continue;
332 if (Inst->hasOneUse() &&
333 cast<Instruction>(Inst->use_back())->getParent() == BB &&
334 !isa<PHINode>(Inst->use_back())) continue;
336 // If this is an alloca in the entry block, it's not a real register
338 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
339 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
342 // Avoid iterator invalidation by copying users to a temporary vector.
343 SmallVector<Instruction*,16> Users;
344 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
346 Instruction *User = cast<Instruction>(*UI);
347 if (User->getParent() != BB || isa<PHINode>(User))
348 Users.push_back(User);
351 // Scan all of the uses and see if the live range is live across an unwind
352 // edge. If we find a use live across an invoke edge, create an alloca
353 // and spill the value.
354 std::set<InvokeInst*> InvokesWithStoreInserted;
356 // Find all of the blocks that this value is live in.
357 std::set<BasicBlock*> LiveBBs;
358 LiveBBs.insert(Inst->getParent());
359 while (!Users.empty()) {
360 Instruction *U = Users.back();
363 if (!isa<PHINode>(U)) {
364 MarkBlocksLiveIn(U->getParent(), LiveBBs);
366 // Uses for a PHI node occur in their predecessor block.
367 PHINode *PN = cast<PHINode>(U);
368 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
369 if (PN->getIncomingValue(i) == Inst)
370 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
374 // Now that we know all of the blocks that this thing is live in, see if
375 // it includes any of the unwind locations.
376 bool NeedsSpill = false;
377 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
378 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
379 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
384 // If we decided we need a spill, do it.
387 DemoteRegToStack(*Inst, true);
392 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
393 SmallVector<ReturnInst*,16> Returns;
394 SmallVector<InvokeInst*,16> Invokes;
395 UnreachableInst* UnreachablePlaceholder = 0;
397 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
398 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
399 // Remember all return instructions in case we insert an invoke into this
401 Returns.push_back(RI);
402 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
403 Invokes.push_back(II);
406 if (Invokes.empty()) return false;
408 NumInvokes += Invokes.size();
410 // TODO: This is not an optimal way to do this. In particular, this always
411 // inserts setjmp calls into the entries of functions with invoke instructions
412 // even though there are possibly paths through the function that do not
413 // execute any invokes. In particular, for functions with early exits, e.g.
414 // the 'addMove' method in hexxagon, it would be nice to not have to do the
415 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
416 // would not be too hard to do.
418 // If we have an invoke instruction, insert a setjmp that dominates all
419 // invokes. After the setjmp, use a cond branch that goes to the original
420 // code path on zero, and to a designated 'catch' block of nonzero.
421 Value *OldJmpBufPtr = 0;
422 if (!Invokes.empty()) {
423 // First thing we need to do is scan the whole function for values that are
424 // live across unwind edges. Each value that is live across an unwind edge
425 // we spill into a stack location, guaranteeing that there is nothing live
426 // across the unwind edge. This process also splits all critical edges
427 // coming out of invoke's.
428 splitLiveRangesLiveAcrossInvokes(Invokes);
430 BasicBlock *EntryBB = F.begin();
432 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
433 // that needs to be restored on all exits from the function. This is an
434 // alloca because the value needs to be live across invokes.
435 unsigned Align = STTI ? STTI->getJumpBufAlignment() : 0;
437 new AllocaInst(JBLinkTy, 0, Align,
438 "jblink", F.begin()->begin());
440 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
441 ConstantInt::get(Type::getInt32Ty(F.getContext()), 1) };
442 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx, "OldBuf",
443 EntryBB->getTerminator());
445 // Copy the JBListHead to the alloca.
446 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
447 EntryBB->getTerminator());
448 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
450 // Add the new jumpbuf to the list.
451 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
453 // Create the catch block. The catch block is basically a big switch
454 // statement that goes to all of the invoke catch blocks.
455 BasicBlock *CatchBB =
456 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
458 // Create an alloca which keeps track of the stack pointer before every
459 // invoke, this allows us to properly restore the stack pointer after
461 AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
462 "stackptr", EntryBB->begin());
464 // Create an alloca which keeps track of which invoke is currently
465 // executing. For normal calls it contains zero.
466 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
467 "invokenum",EntryBB->begin());
468 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
469 InvokeNum, true, EntryBB->getTerminator());
471 // Insert a load in the Catch block, and a switch on its value. By default,
472 // we go to a block that just does an unwind (which is the correct action
473 // for a standard call). We insert an unreachable instruction here and
474 // modify the block to jump to the correct unwinding pad later.
475 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
476 UnreachablePlaceholder = new UnreachableInst(F.getContext(), UnwindBB);
478 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
479 SwitchInst *CatchSwitch =
480 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
482 // Now that things are set up, insert the setjmp call itself.
484 // Split the entry block to insert the conditional branch for the setjmp.
485 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
488 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
489 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx, "TheJmpBuf",
490 EntryBB->getTerminator());
491 JmpBufPtr = new BitCastInst(JmpBufPtr,
492 Type::getInt8PtrTy(F.getContext()),
493 "tmp", EntryBB->getTerminator());
494 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
495 EntryBB->getTerminator());
497 // Compare the return value to zero.
498 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
499 ICmpInst::ICMP_EQ, SJRet,
500 Constant::getNullValue(SJRet->getType()),
502 // Nuke the uncond branch.
503 EntryBB->getTerminator()->eraseFromParent();
505 // Put in a new condbranch in its place.
506 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
508 // At this point, we are all set up, rewrite each invoke instruction.
509 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
510 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
513 // We know that there is at least one unwind.
515 // Create three new blocks, the block to load the jmpbuf ptr and compare
516 // against null, the block to do the longjmp, and the error block for if it
517 // is null. Add them at the end of the function because they are not hot.
518 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
520 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
521 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
523 // If this function contains an invoke, restore the old jumpbuf ptr.
526 // Before the return, insert a copy from the saved value to the new value.
527 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
528 new StoreInst(BufPtr, JBListHead, UnwindHandler);
530 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
533 // Load the JBList, if it's null, then there was no catch!
534 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
535 Constant::getNullValue(BufPtr->getType()),
537 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
539 // Create the block to do the longjmp.
540 // Get a pointer to the jmpbuf and longjmp.
541 Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
542 ConstantInt::get(Type::getInt32Ty(F.getContext()), 0) };
543 Idx[0] = GetElementPtrInst::Create(BufPtr, Idx, "JmpBuf", UnwindBlock);
544 Idx[0] = new BitCastInst(Idx[0],
545 Type::getInt8PtrTy(F.getContext()),
547 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
548 CallInst::Create(LongJmpFn, Idx, "", UnwindBlock);
549 new UnreachableInst(F.getContext(), UnwindBlock);
551 // Set up the term block ("throw without a catch").
552 new UnreachableInst(F.getContext(), TermBlock);
554 // Insert a call to abort()
555 CallInst::Create(AbortFn, "",
556 TermBlock->getTerminator())->setTailCall();
558 // Replace the inserted unreachable with a branch to the unwind handler.
559 if (UnreachablePlaceholder) {
560 BranchInst::Create(UnwindHandler, UnreachablePlaceholder);
561 UnreachablePlaceholder->eraseFromParent();
564 // Finally, for any returns from this function, if this function contains an
565 // invoke, restore the old jmpbuf pointer to its input value.
567 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
568 ReturnInst *R = Returns[i];
570 // Before the return, insert a copy from the saved value to the new value.
571 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
572 new StoreInst(OldBuf, JBListHead, true, R);
579 bool LowerInvoke::runOnFunction(Function &F) {
580 TargetTransformInfo *TTI = getAnalysisIfAvailable<TargetTransformInfo>();
582 STTI = TTI->getScalarTargetTransformInfo();
584 if (useExpensiveEHSupport)
585 return insertExpensiveEHSupport(F);
587 return insertCheapEHSupport(F);