diff options
Diffstat (limited to 'lib/Transforms/Utils/LowerInvoke.cpp')
| -rw-r--r-- | lib/Transforms/Utils/LowerInvoke.cpp | 580 |
1 files changed, 580 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/LowerInvoke.cpp b/lib/Transforms/Utils/LowerInvoke.cpp new file mode 100644 index 0000000000..7039a4b7e1 --- /dev/null +++ b/lib/Transforms/Utils/LowerInvoke.cpp @@ -0,0 +1,580 @@ +//===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===// +// +// The LLVM Compiler Infrastructure +// +// This file was developed by the LLVM research group and is distributed under +// the University of Illinois Open Source License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This transformation is designed for use by code generators which do not yet +// support stack unwinding. This pass supports two models of exception handling +// lowering, the 'cheap' support and the 'expensive' support. +// +// 'Cheap' exception handling support gives the program the ability to execute +// any program which does not "throw an exception", by turning 'invoke' +// instructions into calls and by turning 'unwind' instructions into calls to +// abort(). If the program does dynamically use the unwind instruction, the +// program will print a message then abort. +// +// 'Expensive' exception handling support gives the full exception handling +// support to the program at the cost of making the 'invoke' instruction +// really expensive. It basically inserts setjmp/longjmp calls to emulate the +// exception handling as necessary. +// +// Because the 'expensive' support slows down programs a lot, and EH is only +// used for a subset of the programs, it must be specifically enabled by an +// option. +// +// Note that after this pass runs the CFG is not entirely accurate (exceptional +// control flow edges are not correct anymore) so only very simple things should +// be done after the lowerinvoke pass has run (like generation of native code). +// This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't +// support the invoke instruction yet" lowering pass. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Scalar.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/Instructions.h" +#include "llvm/Module.h" +#include "llvm/Pass.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Support/CommandLine.h" +#include <csetjmp> +using namespace llvm; + +namespace { + Statistic<> NumInvokes("lowerinvoke", "Number of invokes replaced"); + Statistic<> NumUnwinds("lowerinvoke", "Number of unwinds replaced"); + Statistic<> NumSpilled("lowerinvoke", + "Number of registers live across unwind edges"); + cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support", + cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code")); + + class LowerInvoke : public FunctionPass { + // Used for both models. + Function *WriteFn; + Function *AbortFn; + Value *AbortMessage; + unsigned AbortMessageLength; + + // Used for expensive EH support. + const Type *JBLinkTy; + GlobalVariable *JBListHead; + Function *SetJmpFn, *LongJmpFn; + public: + bool doInitialization(Module &M); + bool runOnFunction(Function &F); + + private: + void createAbortMessage(); + void writeAbortMessage(Instruction *IB); + bool insertCheapEHSupport(Function &F); + void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes); + void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo, + AllocaInst *InvokeNum, SwitchInst *CatchSwitch); + bool insertExpensiveEHSupport(Function &F); + }; + + RegisterOpt<LowerInvoke> + X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators"); +} + +const PassInfo *llvm::LowerInvokePassID = X.getPassInfo(); + +// Public Interface To the LowerInvoke pass. +FunctionPass *llvm::createLowerInvokePass() { return new LowerInvoke(); } + +// doInitialization - Make sure that there is a prototype for abort in the +// current module. +bool LowerInvoke::doInitialization(Module &M) { + const Type *VoidPtrTy = PointerType::get(Type::SByteTy); + AbortMessage = 0; + if (ExpensiveEHSupport) { + // Insert a type for the linked list of jump buffers. Unfortunately, we + // don't know the size of the target's setjmp buffer, so we make a guess. + // If this guess turns out to be too small, bad stuff could happen. + unsigned JmpBufSize = 200; // PPC has 192 words + assert(sizeof(jmp_buf) <= JmpBufSize*sizeof(void*) && + "LowerInvoke doesn't know about targets with jmp_buf size > 200 words!"); + const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JmpBufSize); + + { // The type is recursive, so use a type holder. + std::vector<const Type*> Elements; + Elements.push_back(JmpBufTy); + OpaqueType *OT = OpaqueType::get(); + Elements.push_back(PointerType::get(OT)); + PATypeHolder JBLType(StructType::get(Elements)); + OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle. + JBLinkTy = JBLType.get(); + M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy); + } + + const Type *PtrJBList = PointerType::get(JBLinkTy); + + // Now that we've done that, insert the jmpbuf list head global, unless it + // already exists. + if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) + JBListHead = new GlobalVariable(PtrJBList, false, + GlobalValue::LinkOnceLinkage, + Constant::getNullValue(PtrJBList), + "llvm.sjljeh.jblist", &M); + SetJmpFn = M.getOrInsertFunction("llvm.setjmp", Type::IntTy, + PointerType::get(JmpBufTy), (Type *)0); + LongJmpFn = M.getOrInsertFunction("llvm.longjmp", Type::VoidTy, + PointerType::get(JmpBufTy), + Type::IntTy, (Type *)0); + } + + // We need the 'write' and 'abort' functions for both models. + AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, (Type *)0); + + // Unfortunately, 'write' can end up being prototyped in several different + // ways. If the user defines a three (or more) operand function named 'write' + // we will use their prototype. We _do not_ want to insert another instance + // of a write prototype, because we don't know that the funcresolve pass will + // run after us. If there is a definition of a write function, but it's not + // suitable for our uses, we just don't emit write calls. If there is no + // write prototype at all, we just add one. + if (Function *WF = M.getNamedFunction("write")) { + if (WF->getFunctionType()->getNumParams() > 3 || + WF->getFunctionType()->isVarArg()) + WriteFn = WF; + else + WriteFn = 0; + } else { + WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::IntTy, + VoidPtrTy, Type::IntTy, (Type *)0); + } + return true; +} + +void LowerInvoke::createAbortMessage() { + Module &M = *WriteFn->getParent(); + if (ExpensiveEHSupport) { + // The abort message for expensive EH support tells the user that the + // program 'unwound' without an 'invoke' instruction. + Constant *Msg = + ConstantArray::get("ERROR: Exception thrown, but not caught!\n"); + AbortMessageLength = Msg->getNumOperands()-1; // don't include \0 + + GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true, + GlobalValue::InternalLinkage, + Msg, "abortmsg", &M); + std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::IntTy)); + AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx); + } else { + // The abort message for cheap EH support tells the user that EH is not + // enabled. + Constant *Msg = + ConstantArray::get("Exception handler needed, but not enabled. Recompile" + " program with -enable-correct-eh-support.\n"); + AbortMessageLength = Msg->getNumOperands()-1; // don't include \0 + + GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true, + GlobalValue::InternalLinkage, + Msg, "abortmsg", &M); + std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::IntTy)); + AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx); + } +} + + +void LowerInvoke::writeAbortMessage(Instruction *IB) { + if (WriteFn) { + if (AbortMessage == 0) createAbortMessage(); + + // These are the arguments we WANT... + std::vector<Value*> Args; + Args.push_back(ConstantInt::get(Type::IntTy, 2)); + Args.push_back(AbortMessage); + Args.push_back(ConstantInt::get(Type::IntTy, AbortMessageLength)); + + // If the actual declaration of write disagrees, insert casts as + // appropriate. + const FunctionType *FT = WriteFn->getFunctionType(); + unsigned NumArgs = FT->getNumParams(); + for (unsigned i = 0; i != 3; ++i) + if (i < NumArgs && FT->getParamType(i) != Args[i]->getType()) + Args[i] = ConstantExpr::getCast(cast<Constant>(Args[i]), + FT->getParamType(i)); + + (new CallInst(WriteFn, Args, "", IB))->setTailCall(); + } +} + +bool LowerInvoke::insertCheapEHSupport(Function &F) { + bool Changed = false; + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) + if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { + // Insert a normal call instruction... + std::string Name = II->getName(); II->setName(""); + CallInst *NewCall = new CallInst(II->getCalledValue(), + std::vector<Value*>(II->op_begin()+3, + II->op_end()), Name, II); + NewCall->setCallingConv(II->getCallingConv()); + II->replaceAllUsesWith(NewCall); + + // Insert an unconditional branch to the normal destination. + new BranchInst(II->getNormalDest(), II); + + // Remove any PHI node entries from the exception destination. + II->getUnwindDest()->removePredecessor(BB); + + // Remove the invoke instruction now. + BB->getInstList().erase(II); + + ++NumInvokes; Changed = true; + } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { + // Insert a new call to write(2, AbortMessage, AbortMessageLength); + writeAbortMessage(UI); + + // Insert a call to abort() + (new CallInst(AbortFn, std::vector<Value*>(), "", UI))->setTailCall(); + + // Insert a return instruction. This really should be a "barrier", as it + // is unreachable. + new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 : + Constant::getNullValue(F.getReturnType()), UI); + + // Remove the unwind instruction now. + BB->getInstList().erase(UI); + + ++NumUnwinds; Changed = true; + } + return Changed; +} + +/// rewriteExpensiveInvoke - Insert code and hack the function to replace the +/// specified invoke instruction with a call. +void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo, + AllocaInst *InvokeNum, + SwitchInst *CatchSwitch) { + ConstantUInt *InvokeNoC = ConstantUInt::get(Type::UIntTy, InvokeNo); + + // Insert a store of the invoke num before the invoke and store zero into the + // location afterward. + new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile + + BasicBlock::iterator NI = II->getNormalDest()->begin(); + while (isa<PHINode>(NI)) ++NI; + // nonvolatile. + new StoreInst(Constant::getNullValue(Type::UIntTy), InvokeNum, false, NI); + + // Add a switch case to our unwind block. + CatchSwitch->addCase(InvokeNoC, II->getUnwindDest()); + + // Insert a normal call instruction. + std::string Name = II->getName(); II->setName(""); + CallInst *NewCall = new CallInst(II->getCalledValue(), + std::vector<Value*>(II->op_begin()+3, + II->op_end()), Name, + II); + NewCall->setCallingConv(II->getCallingConv()); + II->replaceAllUsesWith(NewCall); + + // Replace the invoke with an uncond branch. + new BranchInst(II->getNormalDest(), NewCall->getParent()); + II->eraseFromParent(); +} + +/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until +/// we reach blocks we've already seen. +static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) { + if (!LiveBBs.insert(BB).second) return; // already been here. + + for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) + MarkBlocksLiveIn(*PI, LiveBBs); +} + +// First thing we need to do is scan the whole function for values that are +// live across unwind edges. Each value that is live across an unwind edge +// we spill into a stack location, guaranteeing that there is nothing live +// across the unwind edge. This process also splits all critical edges +// coming out of invoke's. +void LowerInvoke:: +splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) { + // First step, split all critical edges from invoke instructions. + for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { + InvokeInst *II = Invokes[i]; + SplitCriticalEdge(II, 0, this); + SplitCriticalEdge(II, 1, this); + assert(!isa<PHINode>(II->getNormalDest()) && + !isa<PHINode>(II->getUnwindDest()) && + "critical edge splitting left single entry phi nodes?"); + } + + Function *F = Invokes.back()->getParent()->getParent(); + + // To avoid having to handle incoming arguments specially, we lower each arg + // to a copy instruction in the entry block. This ensure that the argument + // value itself cannot be live across the entry block. + BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin(); + while (isa<AllocaInst>(AfterAllocaInsertPt) && + isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize())) + ++AfterAllocaInsertPt; + for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); + AI != E; ++AI) { + CastInst *NC = new CastInst(AI, AI->getType(), AI->getName()+".tmp", + AfterAllocaInsertPt); + AI->replaceAllUsesWith(NC); + NC->setOperand(0, AI); + } + + // Finally, scan the code looking for instructions with bad live ranges. + for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) + for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { + // Ignore obvious cases we don't have to handle. In particular, most + // instructions either have no uses or only have a single use inside the + // current block. Ignore them quickly. + Instruction *Inst = II; + if (Inst->use_empty()) continue; + if (Inst->hasOneUse() && + cast<Instruction>(Inst->use_back())->getParent() == BB && + !isa<PHINode>(Inst->use_back())) continue; + + // If this is an alloca in the entry block, it's not a real register + // value. + if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) + if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin()) + continue; + + // Avoid iterator invalidation by copying users to a temporary vector. + std::vector<Instruction*> Users; + for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); + UI != E; ++UI) { + Instruction *User = cast<Instruction>(*UI); + if (User->getParent() != BB || isa<PHINode>(User)) + Users.push_back(User); + } + + // Scan all of the uses and see if the live range is live across an unwind + // edge. If we find a use live across an invoke edge, create an alloca + // and spill the value. + AllocaInst *SpillLoc = 0; + std::set<InvokeInst*> InvokesWithStoreInserted; + + // Find all of the blocks that this value is live in. + std::set<BasicBlock*> LiveBBs; + LiveBBs.insert(Inst->getParent()); + while (!Users.empty()) { + Instruction *U = Users.back(); + Users.pop_back(); + + if (!isa<PHINode>(U)) { + MarkBlocksLiveIn(U->getParent(), LiveBBs); + } else { + // Uses for a PHI node occur in their predecessor block. + PHINode *PN = cast<PHINode>(U); + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (PN->getIncomingValue(i) == Inst) + MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); + } + } + + // Now that we know all of the blocks that this thing is live in, see if + // it includes any of the unwind locations. + bool NeedsSpill = false; + for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { + BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); + if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { + NeedsSpill = true; + } + } + + // If we decided we need a spill, do it. + if (NeedsSpill) { + ++NumSpilled; + DemoteRegToStack(*Inst, true); + } + } +} + +bool LowerInvoke::insertExpensiveEHSupport(Function &F) { + std::vector<ReturnInst*> Returns; + std::vector<UnwindInst*> Unwinds; + std::vector<InvokeInst*> Invokes; + + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) + if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { + // Remember all return instructions in case we insert an invoke into this + // function. + Returns.push_back(RI); + } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { + Invokes.push_back(II); + } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { + Unwinds.push_back(UI); + } + + if (Unwinds.empty() && Invokes.empty()) return false; + + NumInvokes += Invokes.size(); + NumUnwinds += Unwinds.size(); + + // TODO: This is not an optimal way to do this. In particular, this always + // inserts setjmp calls into the entries of functions with invoke instructions + // even though there are possibly paths through the function that do not + // execute any invokes. In particular, for functions with early exits, e.g. + // the 'addMove' method in hexxagon, it would be nice to not have to do the + // setjmp stuff on the early exit path. This requires a bit of dataflow, but + // would not be too hard to do. + + // If we have an invoke instruction, insert a setjmp that dominates all + // invokes. After the setjmp, use a cond branch that goes to the original + // code path on zero, and to a designated 'catch' block of nonzero. + Value *OldJmpBufPtr = 0; + if (!Invokes.empty()) { + // First thing we need to do is scan the whole function for values that are + // live across unwind edges. Each value that is live across an unwind edge + // we spill into a stack location, guaranteeing that there is nothing live + // across the unwind edge. This process also splits all critical edges + // coming out of invoke's. + splitLiveRangesLiveAcrossInvokes(Invokes); + + BasicBlock *EntryBB = F.begin(); + + // Create an alloca for the incoming jump buffer ptr and the new jump buffer + // that needs to be restored on all exits from the function. This is an + // alloca because the value needs to be live across invokes. + AllocaInst *JmpBuf = + new AllocaInst(JBLinkTy, 0, "jblink", F.begin()->begin()); + + std::vector<Value*> Idx; + Idx.push_back(Constant::getNullValue(Type::IntTy)); + Idx.push_back(ConstantUInt::get(Type::UIntTy, 1)); + OldJmpBufPtr = new GetElementPtrInst(JmpBuf, Idx, "OldBuf", + EntryBB->getTerminator()); + + // Copy the JBListHead to the alloca. + Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true, + EntryBB->getTerminator()); + new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator()); + + // Add the new jumpbuf to the list. + new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator()); + + // Create the catch block. The catch block is basically a big switch + // statement that goes to all of the invoke catch blocks. + BasicBlock *CatchBB = new BasicBlock("setjmp.catch", &F); + + // Create an alloca which keeps track of which invoke is currently + // executing. For normal calls it contains zero. + AllocaInst *InvokeNum = new AllocaInst(Type::UIntTy, 0, "invokenum", + EntryBB->begin()); + new StoreInst(ConstantInt::get(Type::UIntTy, 0), InvokeNum, true, + EntryBB->getTerminator()); + + // Insert a load in the Catch block, and a switch on its value. By default, + // we go to a block that just does an unwind (which is the correct action + // for a standard call). + BasicBlock *UnwindBB = new BasicBlock("unwindbb", &F); + Unwinds.push_back(new UnwindInst(UnwindBB)); + + Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB); + SwitchInst *CatchSwitch = + new SwitchInst(CatchLoad, UnwindBB, Invokes.size(), CatchBB); + + // Now that things are set up, insert the setjmp call itself. + + // Split the entry block to insert the conditional branch for the setjmp. + BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(), + "setjmp.cont"); + + Idx[1] = ConstantUInt::get(Type::UIntTy, 0); + Value *JmpBufPtr = new GetElementPtrInst(JmpBuf, Idx, "TheJmpBuf", + EntryBB->getTerminator()); + Value *SJRet = new CallInst(SetJmpFn, JmpBufPtr, "sjret", + EntryBB->getTerminator()); + + // Compare the return value to zero. + Value *IsNormal = BinaryOperator::createSetEQ(SJRet, + Constant::getNullValue(SJRet->getType()), + "notunwind", EntryBB->getTerminator()); + // Nuke the uncond branch. + EntryBB->getTerminator()->eraseFromParent(); + + // Put in a new condbranch in its place. + new BranchInst(ContBlock, CatchBB, IsNormal, EntryBB); + + // At this point, we are all set up, rewrite each invoke instruction. + for (unsigned i = 0, e = Invokes.size(); i != e; ++i) + rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch); + } + + // We know that there is at least one unwind. + + // Create three new blocks, the block to load the jmpbuf ptr and compare + // against null, the block to do the longjmp, and the error block for if it + // is null. Add them at the end of the function because they are not hot. + BasicBlock *UnwindHandler = new BasicBlock("dounwind", &F); + BasicBlock *UnwindBlock = new BasicBlock("unwind", &F); + BasicBlock *TermBlock = new BasicBlock("unwinderror", &F); + + // If this function contains an invoke, restore the old jumpbuf ptr. + Value *BufPtr; + if (OldJmpBufPtr) { + // Before the return, insert a copy from the saved value to the new value. + BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler); + new StoreInst(BufPtr, JBListHead, UnwindHandler); + } else { + BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler); + } + + // Load the JBList, if it's null, then there was no catch! + Value *NotNull = BinaryOperator::createSetNE(BufPtr, + Constant::getNullValue(BufPtr->getType()), + "notnull", UnwindHandler); + new BranchInst(UnwindBlock, TermBlock, NotNull, UnwindHandler); + + // Create the block to do the longjmp. + // Get a pointer to the jmpbuf and longjmp. + std::vector<Value*> Idx; + Idx.push_back(Constant::getNullValue(Type::IntTy)); + Idx.push_back(ConstantUInt::get(Type::UIntTy, 0)); + Idx[0] = new GetElementPtrInst(BufPtr, Idx, "JmpBuf", UnwindBlock); + Idx[1] = ConstantInt::get(Type::IntTy, 1); + new CallInst(LongJmpFn, Idx, "", UnwindBlock); + new UnreachableInst(UnwindBlock); + + // Set up the term block ("throw without a catch"). + new UnreachableInst(TermBlock); + + // Insert a new call to write(2, AbortMessage, AbortMessageLength); + writeAbortMessage(TermBlock->getTerminator()); + + // Insert a call to abort() + (new CallInst(AbortFn, std::vector<Value*>(), "", + TermBlock->getTerminator()))->setTailCall(); + + + // Replace all unwinds with a branch to the unwind handler. + for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) { + new BranchInst(UnwindHandler, Unwinds[i]); + Unwinds[i]->eraseFromParent(); + } + + // Finally, for any returns from this function, if this function contains an + // invoke, restore the old jmpbuf pointer to its input value. + if (OldJmpBufPtr) { + for (unsigned i = 0, e = Returns.size(); i != e; ++i) { + ReturnInst *R = Returns[i]; + + // Before the return, insert a copy from the saved value to the new value. + Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R); + new StoreInst(OldBuf, JBListHead, true, R); + } + } + + return true; +} + +bool LowerInvoke::runOnFunction(Function &F) { + if (ExpensiveEHSupport) + return insertExpensiveEHSupport(F); + else + return insertCheapEHSupport(F); +} |