DwarfEHPrepare.cpp [plain text]
#define DEBUG_TYPE "dwarfehprepare"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
STATISTIC(NumResumesLowered, "Number of resume calls lowered");
namespace {
class DwarfEHPrepare : public FunctionPass {
const TargetMachine *TM;
const TargetLowering *TLI;
Constant *RewindFunction;
bool InsertUnwindResumeCalls(Function &Fn);
public:
static char ID; DwarfEHPrepare(const TargetMachine *tm) :
FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
RewindFunction(0) {
initializeDominatorTreePass(*PassRegistry::getPassRegistry());
}
virtual bool runOnFunction(Function &Fn);
virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
const char *getPassName() const {
return "Exception handling preparation";
}
};
}
char DwarfEHPrepare::ID = 0;
FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
return new DwarfEHPrepare(tm);
}
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
bool UsesNewEH = false;
SmallVector<ResumeInst*, 16> Resumes;
for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
TerminatorInst *TI = I->getTerminator();
if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
Resumes.push_back(RI);
else if (InvokeInst *II = dyn_cast<InvokeInst>(TI))
UsesNewEH = II->getUnwindDest()->isLandingPad();
}
if (Resumes.empty())
return UsesNewEH;
if (!RewindFunction) {
LLVMContext &Ctx = Resumes[0]->getContext();
FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
Type::getInt8PtrTy(Ctx), false);
const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
}
LLVMContext &Ctx = Fn.getContext();
BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), Resumes.size(),
"exn.obj", UnwindBB);
for (SmallVectorImpl<ResumeInst*>::iterator
I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
ResumeInst *RI = *I;
BranchInst::Create(UnwindBB, RI->getParent());
ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0),
0, "exn.obj", RI);
PN->addIncoming(ExnObj, RI->getParent());
RI->eraseFromParent();
++NumResumesLowered;
}
CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
new UnreachableInst(Ctx, UnwindBB);
return true;
}
bool DwarfEHPrepare::runOnFunction(Function &Fn) {
bool Changed = InsertUnwindResumeCalls(Fn);
return Changed;
}