void ValueEnumerator::EnumerateMetadata(const Value *MD) {
assert((isa<MDNode>(MD) || isa<MDString>(MD)) && "Invalid metadata kind");
- // Enumerate the type of this value.
- EnumerateType(MD->getType());
-
+ // Skip function-local nodes themselves, but walk their operands.
const MDNode *N = dyn_cast<MDNode>(MD);
-
- // In the module-level pass, skip function-local nodes themselves, but
- // do walk their operands.
if (N && N->isFunctionLocal() && N->getFunction()) {
EnumerateMDNodeOperands(N);
return;
}
- // Check to see if it's already in!
- unsigned &MDValueID = MDValueMap[MD];
- if (MDValueID)
+ // Insert a dummy ID to block the co-recursive call to
+ // EnumerateMDNodeOperands() from re-visiting MD in a cyclic graph.
+ //
+ // Return early if there's already an ID.
+ if (!MDValueMap.insert(std::make_pair(MD, 0)).second)
return;
- MDValues.push_back(MD);
- MDValueID = MDValues.size();
+ // Enumerate the type of this value.
+ EnumerateType(MD->getType());
- // Enumerate all non-function-local operands.
+ // Visit operands first to minimize RAUW.
if (N)
EnumerateMDNodeOperands(N);
+
+ // Replace the dummy ID inserted above with the correct one. MDValueMap may
+ // have changed by inserting operands, so we need a fresh lookup here.
+ MDValues.push_back(MD);
+ MDValueMap[MD] = MDValues.size();
}
/// EnumerateFunctionLocalMetadataa - Incorporate function-local metadata