bool LowerIntrinsics::NeedsDefaultLoweringPass(const GCStrategy &C) {
// Default lowering is necessary only if read or write barriers have a default
// action. The default for roots is no action.
return !C.customWriteBarrier()
|| !C.customReadBarrier()
|| C.initializeRoots();
}
bool LowerIntrinsics::PerformDefaultLowering(Function &F, GCStrategy &S) {
InsertAutomaticGCRoots(F, S);
// FIXME: Turn this back on after fixing gcregroot in SelectionDAG.
//InsertGCRegisterRoots(F, S);
bool LowerWr = !S.customWriteBarrier();
bool LowerRd = !S.customReadBarrier();
bool InitRoots = S.initializeRoots();
SmallVector<Instruction *, 32> Roots;
bool MadeChange = false;
for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE; ++BB) {
for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) {
Function *F = CI->getCalledFunction();
switch (F->getIntrinsicID()) {
case Intrinsic::gcwrite:
if (LowerWr) {
// Replace a write barrier with a simple store.
Value *St = new StoreInst(CI->getArgOperand(0),
CI->getArgOperand(2), CI);
CI->replaceAllUsesWith(St);
CI->eraseFromParent();
}
break;
case Intrinsic::gcread:
if (LowerRd) {
// Replace a read barrier with a simple load.
Value *Ld = new LoadInst(CI->getArgOperand(1), "", CI);
Ld->takeName(CI);
CI->replaceAllUsesWith(Ld);
CI->eraseFromParent();
}
break;
case Intrinsic::gcroot:
if (InitRoots) {
// Initialize the GC root, but do not delete the intrinsic. The
// backend needs the intrinsic to flag the stack slot.
Value *V = CI->getArgOperand(0)->stripPointerCastsOnly();
Roots.push_back(cast<Instruction>(V));
}
break;
default:
continue;
}
MadeChange = true;
}
}
}
if (Roots.size())
MadeChange |= InsertRootInitializers(F, Roots.begin(), Roots.size());
return MadeChange;
}