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, *StackSaveFn, *StackRestoreFn;
74 bool useExpensiveEHSupport;
76 // We peek in TLI to grab the target's jmp_buf size and alignment
77 const TargetLowering *TLI;
80 static char ID; // Pass identification, replacement for typeid
81 explicit LowerInvoke(const TargetLowering *tli = NULL,
82 bool useExpensiveEHSupport = ExpensiveEHSupport)
83 : FunctionPass(&ID), useExpensiveEHSupport(useExpensiveEHSupport),
85 bool doInitialization(Module &M);
86 bool runOnFunction(Function &F);
88 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
89 // This is a cluster of orthogonal Transforms
90 AU.addPreservedID(PromoteMemoryToRegisterID);
91 AU.addPreservedID(LowerSwitchID);
95 void createAbortMessage(Module *M);
96 void writeAbortMessage(Instruction *IB);
97 bool insertCheapEHSupport(Function &F);
98 void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
99 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
100 AllocaInst *InvokeNum, AllocaInst *StackPtr,
101 SwitchInst *CatchSwitch);
102 bool insertExpensiveEHSupport(Function &F);
106 char LowerInvoke::ID = 0;
107 static RegisterPass<LowerInvoke>
108 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
110 const PassInfo *const llvm::LowerInvokePassID = &X;
112 // Public Interface To the LowerInvoke pass.
113 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
114 return new LowerInvoke(TLI, ExpensiveEHSupport);
116 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI,
117 bool useExpensiveEHSupport) {
118 return new LowerInvoke(TLI, useExpensiveEHSupport);
121 // doInitialization - Make sure that there is a prototype for abort in the
123 bool LowerInvoke::doInitialization(Module &M) {
124 const Type *VoidPtrTy =
125 Type::getInt8PtrTy(M.getContext());
127 if (useExpensiveEHSupport) {
128 // Insert a type for the linked list of jump buffers.
129 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
130 JBSize = JBSize ? JBSize : 200;
131 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
133 { // The type is recursive, so use a type holder.
134 std::vector<const Type*> Elements;
135 Elements.push_back(JmpBufTy);
136 OpaqueType *OT = OpaqueType::get(M.getContext());
137 Elements.push_back(PointerType::getUnqual(OT));
138 PATypeHolder JBLType(StructType::get(M.getContext(), Elements));
139 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
140 JBLinkTy = JBLType.get();
141 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
144 const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
146 // Now that we've done that, insert the jmpbuf list head global, unless it
148 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
149 JBListHead = new GlobalVariable(M, PtrJBList, false,
150 GlobalValue::LinkOnceAnyLinkage,
151 Constant::getNullValue(PtrJBList),
152 "llvm.sjljeh.jblist");
155 // VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
156 // so it looks like Intrinsic::_setjmp
157 #if defined(_MSC_VER) && defined(setjmp)
158 #define setjmp_undefined_for_visual_studio
162 SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
164 #if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
165 // let's return it to _setjmp state in case anyone ever needs it after this
166 // point under VisualStudio
167 #define setjmp _setjmp
170 LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
171 StackSaveFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
172 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
175 // We need the 'write' and 'abort' functions for both models.
176 AbortFn = M.getOrInsertFunction("abort", Type::getVoidTy(M.getContext()),
178 #if 0 // "write" is Unix-specific.. code is going away soon anyway.
179 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
180 VoidPtrTy, Type::Int32Ty, (Type *)0);
187 void LowerInvoke::createAbortMessage(Module *M) {
188 if (useExpensiveEHSupport) {
189 // The abort message for expensive EH support tells the user that the
190 // program 'unwound' without an 'invoke' instruction.
192 ConstantArray::get(M->getContext(),
193 "ERROR: Exception thrown, but not caught!\n");
194 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
196 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
197 GlobalValue::InternalLinkage,
199 std::vector<Constant*> GEPIdx(2,
200 Constant::getNullValue(Type::getInt32Ty(M->getContext())));
201 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
203 // The abort message for cheap EH support tells the user that EH is not
206 ConstantArray::get(M->getContext(),
207 "Exception handler needed, but not enabled."
208 "Recompile program with -enable-correct-eh-support.\n");
209 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
211 GlobalVariable *MsgGV = new GlobalVariable(*M, Msg->getType(), true,
212 GlobalValue::InternalLinkage,
214 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(
215 Type::getInt32Ty(M->getContext())));
216 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
221 void LowerInvoke::writeAbortMessage(Instruction *IB) {
223 if (AbortMessage == 0)
224 createAbortMessage(IB->getParent()->getParent()->getParent());
226 // These are the arguments we WANT...
228 Args[0] = ConstantInt::get(Type::Int32Ty, 2);
229 Args[1] = AbortMessage;
230 Args[2] = ConstantInt::get(Type::Int32Ty, AbortMessageLength);
231 (new CallInst(WriteFn, Args, 3, "", IB))->setTailCall();
235 bool LowerInvoke::insertCheapEHSupport(Function &F) {
236 bool Changed = false;
237 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
238 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
239 std::vector<Value*> CallArgs(II->op_begin(), II->op_end() - 3);
240 // Insert a normal call instruction...
241 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
242 CallArgs.begin(), CallArgs.end(),
244 NewCall->takeName(II);
245 NewCall->setCallingConv(II->getCallingConv());
246 NewCall->setAttributes(II->getAttributes());
247 II->replaceAllUsesWith(NewCall);
249 // Insert an unconditional branch to the normal destination.
250 BranchInst::Create(II->getNormalDest(), II);
252 // Remove any PHI node entries from the exception destination.
253 II->getUnwindDest()->removePredecessor(BB);
255 // Remove the invoke instruction now.
256 BB->getInstList().erase(II);
258 ++NumInvokes; Changed = true;
259 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
260 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
261 writeAbortMessage(UI);
263 // Insert a call to abort()
264 CallInst::Create(AbortFn, "", UI)->setTailCall();
266 // Insert a return instruction. This really should be a "barrier", as it
268 ReturnInst::Create(F.getContext(),
269 F.getReturnType()->isVoidTy() ?
270 0 : Constant::getNullValue(F.getReturnType()), UI);
272 // Remove the unwind instruction now.
273 BB->getInstList().erase(UI);
275 ++NumUnwinds; Changed = true;
280 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
281 /// specified invoke instruction with a call.
282 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
283 AllocaInst *InvokeNum,
284 AllocaInst *StackPtr,
285 SwitchInst *CatchSwitch) {
286 ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
289 // If the unwind edge has phi nodes, split the edge.
290 if (isa<PHINode>(II->getUnwindDest()->begin())) {
291 SplitCriticalEdge(II, 1, this);
293 // If there are any phi nodes left, they must have a single predecessor.
294 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
295 PN->replaceAllUsesWith(PN->getIncomingValue(0));
296 PN->eraseFromParent();
300 // Insert a store of the invoke num before the invoke and store zero into the
301 // location afterward.
302 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
304 // Insert a store of the stack ptr before the invoke, so we can restore it
305 // later in the exception case.
306 CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
307 new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
309 BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
311 new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
312 InvokeNum, false, NI);
314 Instruction* StackPtrLoad = new LoadInst(StackPtr, "stackptr.restore", true,
315 II->getUnwindDest()->getFirstNonPHI()
317 CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
319 // Add a switch case to our unwind block.
320 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
322 // Insert a normal call instruction.
323 std::vector<Value*> CallArgs(II->op_begin(), II->op_end() - 3);
324 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
325 CallArgs.begin(), CallArgs.end(), "",
327 NewCall->takeName(II);
328 NewCall->setCallingConv(II->getCallingConv());
329 NewCall->setAttributes(II->getAttributes());
330 II->replaceAllUsesWith(NewCall);
332 // Replace the invoke with an uncond branch.
333 BranchInst::Create(II->getNormalDest(), NewCall->getParent());
334 II->eraseFromParent();
337 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
338 /// we reach blocks we've already seen.
339 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
340 if (!LiveBBs.insert(BB).second) return; // already been here.
342 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
343 MarkBlocksLiveIn(*PI, LiveBBs);
346 // First thing we need to do is scan the whole function for values that are
347 // live across unwind edges. Each value that is live across an unwind edge
348 // we spill into a stack location, guaranteeing that there is nothing live
349 // across the unwind edge. This process also splits all critical edges
350 // coming out of invoke's.
352 splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
353 // First step, split all critical edges from invoke instructions.
354 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
355 InvokeInst *II = Invokes[i];
356 SplitCriticalEdge(II, 0, this);
357 SplitCriticalEdge(II, 1, this);
358 assert(!isa<PHINode>(II->getNormalDest()) &&
359 !isa<PHINode>(II->getUnwindDest()) &&
360 "critical edge splitting left single entry phi nodes?");
363 Function *F = Invokes.back()->getParent()->getParent();
365 // To avoid having to handle incoming arguments specially, we lower each arg
366 // to a copy instruction in the entry block. This ensures that the argument
367 // value itself cannot be live across the entry block.
368 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
369 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
370 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
371 ++AfterAllocaInsertPt;
372 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
374 // This is always a no-op cast because we're casting AI to AI->getType() so
375 // src and destination types are identical. BitCast is the only possibility.
376 CastInst *NC = new BitCastInst(
377 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
378 AI->replaceAllUsesWith(NC);
379 // Normally its is forbidden to replace a CastInst's operand because it
380 // could cause the opcode to reflect an illegal conversion. However, we're
381 // replacing it here with the same value it was constructed with to simply
383 NC->setOperand(0, AI);
386 // Finally, scan the code looking for instructions with bad live ranges.
387 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
388 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
389 // Ignore obvious cases we don't have to handle. In particular, most
390 // instructions either have no uses or only have a single use inside the
391 // current block. Ignore them quickly.
392 Instruction *Inst = II;
393 if (Inst->use_empty()) continue;
394 if (Inst->hasOneUse() &&
395 cast<Instruction>(Inst->use_back())->getParent() == BB &&
396 !isa<PHINode>(Inst->use_back())) continue;
398 // If this is an alloca in the entry block, it's not a real register
400 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
401 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
404 // Avoid iterator invalidation by copying users to a temporary vector.
405 std::vector<Instruction*> Users;
406 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
408 Instruction *User = cast<Instruction>(*UI);
409 if (User->getParent() != BB || isa<PHINode>(User))
410 Users.push_back(User);
413 // Scan all of the uses and see if the live range is live across an unwind
414 // edge. If we find a use live across an invoke edge, create an alloca
415 // and spill the value.
416 std::set<InvokeInst*> InvokesWithStoreInserted;
418 // Find all of the blocks that this value is live in.
419 std::set<BasicBlock*> LiveBBs;
420 LiveBBs.insert(Inst->getParent());
421 while (!Users.empty()) {
422 Instruction *U = Users.back();
425 if (!isa<PHINode>(U)) {
426 MarkBlocksLiveIn(U->getParent(), LiveBBs);
428 // Uses for a PHI node occur in their predecessor block.
429 PHINode *PN = cast<PHINode>(U);
430 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
431 if (PN->getIncomingValue(i) == Inst)
432 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
436 // Now that we know all of the blocks that this thing is live in, see if
437 // it includes any of the unwind locations.
438 bool NeedsSpill = false;
439 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
440 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
441 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
446 // If we decided we need a spill, do it.
449 DemoteRegToStack(*Inst, true);
454 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
455 std::vector<ReturnInst*> Returns;
456 std::vector<UnwindInst*> Unwinds;
457 std::vector<InvokeInst*> Invokes;
459 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
460 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
461 // Remember all return instructions in case we insert an invoke into this
463 Returns.push_back(RI);
464 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
465 Invokes.push_back(II);
466 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
467 Unwinds.push_back(UI);
470 if (Unwinds.empty() && Invokes.empty()) return false;
472 NumInvokes += Invokes.size();
473 NumUnwinds += Unwinds.size();
475 // TODO: This is not an optimal way to do this. In particular, this always
476 // inserts setjmp calls into the entries of functions with invoke instructions
477 // even though there are possibly paths through the function that do not
478 // execute any invokes. In particular, for functions with early exits, e.g.
479 // the 'addMove' method in hexxagon, it would be nice to not have to do the
480 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
481 // would not be too hard to do.
483 // If we have an invoke instruction, insert a setjmp that dominates all
484 // invokes. After the setjmp, use a cond branch that goes to the original
485 // code path on zero, and to a designated 'catch' block of nonzero.
486 Value *OldJmpBufPtr = 0;
487 if (!Invokes.empty()) {
488 // First thing we need to do is scan the whole function for values that are
489 // live across unwind edges. Each value that is live across an unwind edge
490 // we spill into a stack location, guaranteeing that there is nothing live
491 // across the unwind edge. This process also splits all critical edges
492 // coming out of invoke's.
493 splitLiveRangesLiveAcrossInvokes(Invokes);
495 BasicBlock *EntryBB = F.begin();
497 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
498 // that needs to be restored on all exits from the function. This is an
499 // alloca because the value needs to be live across invokes.
500 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
502 new AllocaInst(JBLinkTy, 0, Align,
503 "jblink", F.begin()->begin());
505 std::vector<Value*> Idx;
506 Idx.push_back(Constant::getNullValue(Type::getInt32Ty(F.getContext())));
507 Idx.push_back(ConstantInt::get(Type::getInt32Ty(F.getContext()), 1));
508 OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
510 EntryBB->getTerminator());
512 // Copy the JBListHead to the alloca.
513 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
514 EntryBB->getTerminator());
515 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
517 // Add the new jumpbuf to the list.
518 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
520 // Create the catch block. The catch block is basically a big switch
521 // statement that goes to all of the invoke catch blocks.
522 BasicBlock *CatchBB =
523 BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
525 // Create an alloca which keeps track of the stack pointer before every
526 // invoke, this allows us to properly restore the stack pointer after
528 AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
529 "stackptr", EntryBB->begin());
531 // Create an alloca which keeps track of which invoke is currently
532 // executing. For normal calls it contains zero.
533 AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
534 "invokenum",EntryBB->begin());
535 new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
536 InvokeNum, true, EntryBB->getTerminator());
538 // Insert a load in the Catch block, and a switch on its value. By default,
539 // we go to a block that just does an unwind (which is the correct action
540 // for a standard call).
541 BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
542 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
544 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
545 SwitchInst *CatchSwitch =
546 SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
548 // Now that things are set up, insert the setjmp call itself.
550 // Split the entry block to insert the conditional branch for the setjmp.
551 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
554 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
555 Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
557 EntryBB->getTerminator());
558 JmpBufPtr = new BitCastInst(JmpBufPtr,
559 Type::getInt8PtrTy(F.getContext()),
560 "tmp", EntryBB->getTerminator());
561 Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
562 EntryBB->getTerminator());
564 // Compare the return value to zero.
565 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
566 ICmpInst::ICMP_EQ, SJRet,
567 Constant::getNullValue(SJRet->getType()),
569 // Nuke the uncond branch.
570 EntryBB->getTerminator()->eraseFromParent();
572 // Put in a new condbranch in its place.
573 BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
575 // At this point, we are all set up, rewrite each invoke instruction.
576 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
577 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
580 // We know that there is at least one unwind.
582 // Create three new blocks, the block to load the jmpbuf ptr and compare
583 // against null, the block to do the longjmp, and the error block for if it
584 // is null. Add them at the end of the function because they are not hot.
585 BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
587 BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
588 BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
590 // If this function contains an invoke, restore the old jumpbuf ptr.
593 // Before the return, insert a copy from the saved value to the new value.
594 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
595 new StoreInst(BufPtr, JBListHead, UnwindHandler);
597 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
600 // Load the JBList, if it's null, then there was no catch!
601 Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
602 Constant::getNullValue(BufPtr->getType()),
604 BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
606 // Create the block to do the longjmp.
607 // Get a pointer to the jmpbuf and longjmp.
608 std::vector<Value*> Idx;
609 Idx.push_back(Constant::getNullValue(Type::getInt32Ty(F.getContext())));
610 Idx.push_back(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0));
611 Idx[0] = GetElementPtrInst::Create(BufPtr, Idx.begin(), Idx.end(), "JmpBuf",
613 Idx[0] = new BitCastInst(Idx[0],
614 Type::getInt8PtrTy(F.getContext()),
616 Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
617 CallInst::Create(LongJmpFn, Idx.begin(), Idx.end(), "", UnwindBlock);
618 new UnreachableInst(F.getContext(), UnwindBlock);
620 // Set up the term block ("throw without a catch").
621 new UnreachableInst(F.getContext(), TermBlock);
623 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
624 writeAbortMessage(TermBlock->getTerminator());
626 // Insert a call to abort()
627 CallInst::Create(AbortFn, "",
628 TermBlock->getTerminator())->setTailCall();
631 // Replace all unwinds with a branch to the unwind handler.
632 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
633 BranchInst::Create(UnwindHandler, Unwinds[i]);
634 Unwinds[i]->eraseFromParent();
637 // Finally, for any returns from this function, if this function contains an
638 // invoke, restore the old jmpbuf pointer to its input value.
640 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
641 ReturnInst *R = Returns[i];
643 // Before the return, insert a copy from the saved value to the new value.
644 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
645 new StoreInst(OldBuf, JBListHead, true, R);
652 bool LowerInvoke::runOnFunction(Function &F) {
653 if (useExpensiveEHSupport)
654 return insertExpensiveEHSupport(F);
656 return insertCheapEHSupport(F);