Add comments explaining why it's not necessary to include the
is-function-local flag in metadata uniquing bits.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112528 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/VMCore/Metadata.cpp b/lib/VMCore/Metadata.cpp
index 17e0bc2..b9f97db 100644
--- a/lib/VMCore/Metadata.cpp
+++ b/lib/VMCore/Metadata.cpp
@@ -190,6 +190,8 @@
// Add all the operand pointers. Note that we don't have to add the
// isFunctionLocal bit because that's implied by the operands.
+ // Note that if the operands are later nulled out, the node will be
+ // removed from the uniquing map.
FoldingSetNodeID ID;
for (unsigned i = 0; i != NumVals; ++i)
ID.AddPointer(Vals[i]);
@@ -276,6 +278,8 @@
void MDNode::Profile(FoldingSetNodeID &ID) const {
// Add all the operand pointers. Note that we don't have to add the
// isFunctionLocal bit because that's implied by the operands.
+ // Note that if the operands are later nulled out, the node will be
+ // removed from the uniquing map.
for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
ID.AddPointer(getOperand(i));
}
@@ -326,7 +330,8 @@
// If we are dropping an argument to null, we choose to not unique the MDNode
// anymore. This commonly occurs during destruction, and uniquing these
- // brings little reuse.
+ // brings little reuse. Also, this means we don't need to include
+ // isFunctionLocal bits in FoldingSetNodeIDs for MDNodes.
if (To == 0) {
setIsNotUniqued();
return;