ValueMapper: Add support for seeding metadata with nullptr

Support seeding a ValueMap with nullptr for Metadata entries, a
situation I didn't consider in the Metadata/Value split.

I added a ValueMapper::getMappedMD accessor that returns an
Optional<Metadata*> with the mapped (possibly null) metadata.  IRMover
needs to use this to avoid modifying the map when it's checking for
unneeded subprograms.  I updated a call from bugpoint since I find the
new code clearer.

llvm-svn: 265228

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index b658ffba0c2..a72c456ef0f 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -305,8 +305,8 @@ static Metadata *MapMetadataImpl(const Metadata *MD,
                                  ValueMapTypeRemapper *TypeMapper,
                                  ValueMaterializer *Materializer) {
   // If the value already exists in the map, use it.
-  if (Metadata *NewMD = VM.MD().lookup(MD).get())
-    return NewMD;
+  if (Optional<Metadata *> NewMD = VM.getMappedMD(MD))
+    return *NewMD;
 
   if (isa<MDString>(MD))
     return mapToSelf(VM, MD);
@@ -380,8 +380,8 @@ Metadata *llvm::MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
 MDNode *llvm::MapMetadata(const MDNode *MD, ValueToValueMapTy &VM,
                           RemapFlags Flags, ValueMapTypeRemapper *TypeMapper,
                           ValueMaterializer *Materializer) {
-  return cast<MDNode>(MapMetadata(static_cast<const Metadata *>(MD), VM, Flags,
-                                  TypeMapper, Materializer));
+  return cast_or_null<MDNode>(MapMetadata(static_cast<const Metadata *>(MD), VM,
+                                          Flags, TypeMapper, Materializer));
 }
 
 /// RemapInstruction - Convert the instruction operands from referencing the