IR: Rewrite uniquing and creation of MDString

Stop using `Value::getName()` to get the string behind an `MDString`.
Switch to `StringMapEntry<MDString>` so that we can find the string by
its coallocation.

This is part of PR21532.

llvm-svn: 221960

1 files changed, 15 insertions, 7 deletions

diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index 8d616cfb0d6..bc9682976b8 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -37,13 +37,21 @@ MDString::MDString(LLVMContext &C)
   : Value(Type::getMetadataTy(C), Value::MDStringVal) {}
 
 MDString *MDString::get(LLVMContext &Context, StringRef Str) {
-  LLVMContextImpl *pImpl = Context.pImpl;
-  StringMapEntry<Value*> &Entry =
-    pImpl->MDStringCache.GetOrCreateValue(Str);
-  Value *&S = Entry.getValue();
-  if (!S) S = new MDString(Context);
-  S->setValueName(&Entry);
-  return cast<MDString>(S);
+  auto &Store = Context.pImpl->MDStringCache;
+  auto I = Store.find(Str);
+  if (I != Store.end())
+    return &I->second;
+
+  auto *Entry =
+      StringMapEntry<MDString>::Create(Str, Store.getAllocator(), Context);
+  bool WasInserted = Store.insert(Entry);
+  (void)WasInserted;
+  assert(WasInserted && "Expected entry to be inserted");
+  return &Entry->second;
+}
+
+StringRef MDString::getString() const {
+  return StringMapEntry<MDString>::GetStringMapEntryFromValue(*this).first();
 }
 
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