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

3 files changed, 17 insertions, 9 deletions

diff --git a/llvm/lib/IR/LLVMContextImpl.cpp b/llvm/lib/IR/LLVMContextImpl.cpp
index 09bf6b123a9..df3449d12c8 100644
--- a/llvm/lib/IR/LLVMContextImpl.cpp
+++ b/llvm/lib/IR/LLVMContextImpl.cpp
@@ -135,7 +135,7 @@ LLVMContextImpl::~LLVMContextImpl() {
          "Destroying all MDNodes didn't empty the Context's sets.");
 
   // Destroy MDStrings.
-  DeleteContainerSeconds(MDStringCache);
+  MDStringCache.clear();
 }
 
 // ConstantsContext anchors
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index bd0097c31ba..3190c22fceb 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -261,7 +261,7 @@ public:
   FoldingSet<AttributeSetImpl> AttrsLists;
   FoldingSet<AttributeSetNode> AttrsSetNodes;
 
-  StringMap<Value*> MDStringCache;
+  StringMap<MDString> MDStringCache;
 
   FoldingSet<MDNode> MDNodeSet;
 
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();
 }
 
 //===----------------------------------------------------------------------===//