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Don't always create a separate block for the call to _Unwind_Resume.

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Sometimes there is only one 'resume' instruction per function. In those
situations, we don't need a separate block for the call to _Unwind_Resume. In
fact, it adds a lot of overhead to code-gen if we do that -- especially at -O0.
If we have a single 'resume' instruction, just generate the call within that
block.
<rdar://problem/10694814>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149159 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2012-01-28 00:47:18 +00:00
parent 1d5013992f
commit b0064c6d8b
1 changed files with 61 additions and 32 deletions
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93
lib/CodeGen/DwarfEHPrepare.cpp
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@ -39,6 +39,7 @@ namespace {
Constant *RewindFunction;
bool InsertUnwindResumeCalls(Function &Fn);
Instruction *GetExceptionObject(ResumeInst *RI);
public:
static char ID; // Pass identification, replacement for typeid.
@ -64,6 +65,46 @@ FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
return new DwarfEHPrepare(tm);
}
/// GetExceptionObject - Return the exception object from the value passed into
/// the 'resume' instruction (typically an aggregate). Clean up any dead
/// instructions, including the 'resume' instruction.
Instruction *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) {
Value *V = RI->getOperand(0);
Instruction *ExnObj = 0;
InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
LoadInst *SelLoad = 0;
InsertValueInst *ExcIVI = 0;
bool EraseIVIs = false;
if (SelIVI) {
if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
ExnObj = cast<Instruction>(ExcIVI->getOperand(1));
SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
EraseIVIs = true;
}
}
}
if (!ExnObj)
ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
RI->eraseFromParent();
if (EraseIVIs) {
if (SelIVI->getNumUses() == 0)
SelIVI->eraseFromParent();
if (ExcIVI->getNumUses() == 0)
ExcIVI->eraseFromParent();
if (SelLoad && SelLoad->getNumUses() == 0)
SelLoad->eraseFromParent();
}
return ExnObj;
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
@ -91,8 +132,26 @@ bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
// 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();
Instruction *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), Resumes.size(),
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
@ -102,38 +161,8 @@ bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
ResumeInst *RI = *I;
BranchInst::Create(UnwindBB, RI->getParent());
Value *V = RI->getOperand(0);
Instruction *ExnObj = 0;
InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
LoadInst *SelLoad = 0;
InsertValueInst *ExcIVI = 0;
bool EraseIVIs = false;
if (SelIVI) {
if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
ExnObj = cast<Instruction>(ExcIVI->getOperand(1));
SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
EraseIVIs = true;
}
}
}
if (!ExnObj)
ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
Instruction *ExnObj = GetExceptionObject(RI);
PN->addIncoming(ExnObj, RI->getParent());
RI->eraseFromParent();
if (EraseIVIs) {
if (SelIVI->getNumUses() == 0)
SelIVI->eraseFromParent();
if (ExcIVI->getNumUses() == 0)
ExcIVI->eraseFromParent();
if (SelLoad && SelLoad->getNumUses() == 0)
SelLoad->eraseFromParent();
}
++NumResumesLowered;
}