/// Replace resumes that are not reachable from a cleanup landing pad with
/// unreachable and then simplify those blocks.
size_t DwarfEHPrepare::pruneUnreachableResumes(
Function &Fn, SmallVectorImpl<ResumeInst *> &Resumes,
SmallVectorImpl<LandingPadInst *> &CleanupLPads) {
BitVector ResumeReachable(Resumes.size());
size_t ResumeIndex = 0;
for (auto *RI : Resumes) {
for (auto *LP : CleanupLPads) {
if (isPotentiallyReachable(LP, RI, DT)) {
ResumeReachable.set(ResumeIndex);
break;
}
}
++ResumeIndex;
}
// If everything is reachable, there is no change.
if (ResumeReachable.all())
return Resumes.size();
const TargetTransformInfo &TTI =
getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn);
LLVMContext &Ctx = Fn.getContext();
// Otherwise, insert unreachable instructions and call simplifycfg.
size_t ResumesLeft = 0;
for (size_t I = 0, E = Resumes.size(); I < E; ++I) {
ResumeInst *RI = Resumes[I];
if (ResumeReachable[I]) {
Resumes[ResumesLeft++] = RI;
} else {
BasicBlock *BB = RI->getParent();
new UnreachableInst(Ctx, RI);
RI->eraseFromParent();
SimplifyCFG(BB, TTI, 1);
}
}
Resumes.resize(ResumesLeft);
return ResumesLeft;
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
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);
}
if (Resumes.empty())
return false;
// Find the rewind function if we didn't already.
const TargetLowering *TLI = TM->getTargetLowering();
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);
}
// Create the basic block where the _Unwind_Resume call will live.
LLVMContext &Ctx = Fn.getContext();
unsigned ResumesSize = Resumes.size();
if (ResumesSize == 1) {
// Instead of creating a new BB and PHI node, just append the call to
// _Unwind_Resume to the end of the single resume block.
ResumeInst *RI = Resumes.front();
BasicBlock *UnwindBB = RI->getParent();
Value *ExnObj = GetExceptionObject(RI);
// Call the _Unwind_Resume function.
CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesSize,
"exn.obj", UnwindBB);
// Extract the exception object from the ResumeInst and add it to the PHI node
// that feeds the _Unwind_Resume call.
for (SmallVectorImpl<ResumeInst*>::iterator
I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
ResumeInst *RI = *I;
BasicBlock *Parent = RI->getParent();
BranchInst::Create(UnwindBB, Parent);
Value *ExnObj = GetExceptionObject(RI);
PN->addIncoming(ExnObj, Parent);
++NumResumesLowered;
}
// Call the function.
CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
SmallVector<ResumeInst*, 16> Resumes;
SmallVector<LandingPadInst*, 16> CleanupLPads;
for (BasicBlock &BB : Fn) {
if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(RI);
if (auto *LP = BB.getLandingPadInst())
if (LP->isCleanup())
CleanupLPads.push_back(LP);
}
if (Resumes.empty())
return false;
// Check the personality, don't do anything if it's funclet-based.
EHPersonality Pers = classifyEHPersonality(Fn.getPersonalityFn());
if (isFuncletEHPersonality(Pers))
return false;
LLVMContext &Ctx = Fn.getContext();
size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads);
if (ResumesLeft == 0)
return true; // We pruned them all.
// Find the rewind function if we didn't already.
if (!RewindFunction) {
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);
}
// Create the basic block where the _Unwind_Resume call will live.
if (ResumesLeft == 1) {
// Instead of creating a new BB and PHI node, just append the call to
// _Unwind_Resume to the end of the single resume block.
ResumeInst *RI = Resumes.front();
BasicBlock *UnwindBB = RI->getParent();
Value *ExnObj = GetExceptionObject(RI);
// Call the _Unwind_Resume function.
CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft,
"exn.obj", UnwindBB);
// Extract the exception object from the ResumeInst and add it to the PHI node
// that feeds the _Unwind_Resume call.
for (ResumeInst *RI : Resumes) {
BasicBlock *Parent = RI->getParent();
BranchInst::Create(UnwindBB, Parent);
Value *ExnObj = GetExceptionObject(RI);
PN->addIncoming(ExnObj, Parent);
++NumResumesLowered;
}
// Call the function.
CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
