bool DevirtModule::run() {
Function *TypeTestFunc =
M.getFunction(Intrinsic::getName(Intrinsic::type_test));
Function *TypeCheckedLoadFunc =
M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load));
Function *AssumeFunc = M.getFunction(Intrinsic::getName(Intrinsic::assume));
if ((!TypeTestFunc || TypeTestFunc->use_empty() || !AssumeFunc ||
AssumeFunc->use_empty()) &&
(!TypeCheckedLoadFunc || TypeCheckedLoadFunc->use_empty()))
return false;
if (TypeTestFunc && AssumeFunc)
scanTypeTestUsers(TypeTestFunc, AssumeFunc);
if (TypeCheckedLoadFunc)
scanTypeCheckedLoadUsers(TypeCheckedLoadFunc);
// Rebuild type metadata into a map for easy lookup.
std::vector<VTableBits> Bits;
DenseMap<Metadata *, std::set<TypeMemberInfo>> TypeIdMap;
buildTypeIdentifierMap(Bits, TypeIdMap);
if (TypeIdMap.empty())
return true;
// For each (type, offset) pair:
bool DidVirtualConstProp = false;
std::map<std::string, Function*> DevirtTargets;
for (auto &S : CallSlots) {
// Search each of the members of the type identifier for the virtual
// function implementation at offset S.first.ByteOffset, and add to
// TargetsForSlot.
std::vector<VirtualCallTarget> TargetsForSlot;
if (!tryFindVirtualCallTargets(TargetsForSlot, TypeIdMap[S.first.TypeID],
S.first.ByteOffset))
continue;
if (!trySingleImplDevirt(TargetsForSlot, S.second) &&
tryVirtualConstProp(TargetsForSlot, S.second))
DidVirtualConstProp = true;
// Collect functions devirtualized at least for one call site for stats.
if (RemarksEnabled)
for (const auto &T : TargetsForSlot)
if (T.WasDevirt)
DevirtTargets[T.Fn->getName()] = T.Fn;
}
if (RemarksEnabled) {
// Generate remarks for each devirtualized function.
for (const auto &DT : DevirtTargets) {
Function *F = DT.second;
DISubprogram *SP = F->getSubprogram();
DebugLoc DL = SP ? DebugLoc::get(SP->getScopeLine(), 0, SP) : DebugLoc();
emitOptimizationRemark(F->getContext(), DEBUG_TYPE, *F, DL,
Twine("devirtualized ") + F->getName());
}
}
// If we were able to eliminate all unsafe uses for a type checked load,
// eliminate the type test by replacing it with true.
if (TypeCheckedLoadFunc) {
auto True = ConstantInt::getTrue(M.getContext());
for (auto &&U : NumUnsafeUsesForTypeTest) {
if (U.second == 0) {
U.first->replaceAllUsesWith(True);
U.first->eraseFromParent();
}
}
}
// Rebuild each global we touched as part of virtual constant propagation to
// include the before and after bytes.
if (DidVirtualConstProp)
for (VTableBits &B : Bits)
rebuildGlobal(B);
return true;
}
