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//===- 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 gives them 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().
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/iTerminators.h"
#include "llvm/iOther.h"
#include "Support/Statistic.h"
using namespace llvm;
namespace {
Statistic<> NumLowered("lowerinvoke", "Number of invoke & unwinds replaced");
class LowerInvoke : public FunctionPass {
Value *AbortMessage;
unsigned AbortMessageLength;
Function *WriteFn;
Function *AbortFn;
public:
bool doInitialization(Module &M);
bool runOnFunction(Function &F);
};
RegisterOpt<LowerInvoke>
X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
}
// 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) {
Constant *Msg =
ConstantArray::get("Exception handler needed, but not available.\n");
AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
GlobalVariable *MsgGV =
new GlobalVariable(Msg->getType(), true, GlobalValue::InternalLinkage, Msg,
"", &M);
std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::LongTy));
AbortMessage =
ConstantExpr::getGetElementPtr(ConstantPointerRef::get(MsgGV), GEPIdx);
AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, 0);
WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::IntTy,
PointerType::get(Type::SByteTy), Type::IntTy,
0);
return true;
}
bool LowerInvoke::runOnFunction(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("");
Value *NewCall = new CallInst(II->getCalledValue(),
std::vector<Value*>(II->op_begin()+3,
II->op_end()), Name,II);
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->getExceptionalDest()->removePredecessor(BB);
// Remove the invoke instruction now.
BB->getInstList().erase(II);
++NumLowered; Changed = true;
} else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
// Insert a new call to write(2, AbortMessage, AbortMessageLength);
std::vector<Value*> Args;
Args.push_back(ConstantInt::get(Type::IntTy, 2));
Args.push_back(AbortMessage);
Args.push_back(ConstantInt::get(Type::IntTy, AbortMessageLength));
new CallInst(WriteFn, Args, "", UI);
// Insert a call to abort()
new CallInst(AbortFn, std::vector<Value*>(), "", UI);
// Insert a return instruction.
new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 :
Constant::getNullValue(F.getReturnType()), UI);
// Remove the unwind instruction now.
BB->getInstList().erase(UI);
++NumLowered; Changed = true;
}
return Changed;
}
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