Query the StringMap only once when creating MDString (NFC)

Summary: Loading IR with debug info improves MDString::get() from 19ms to 10ms.

Reviewers: dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D16597

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261030 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/IR/Metadata.h b/include/llvm/IR/Metadata.h
index df8ce35..bb21d7a 100644 (file)
--- a/include/llvm/IR/Metadata.h
+++ b/include/llvm/IR/Metadata.h
@@ -592,9 +592,9 @@ class MDString : public Metadata {
 
   StringMapEntry<MDString> *Entry;
   MDString() : Metadata(MDStringKind, Uniqued), Entry(nullptr) {}
-  MDString(MDString &&) : Metadata(MDStringKind, Uniqued) {}
 
 public:
+  MDString(MDString &&R) = default;
   static MDString *get(LLVMContext &Context, StringRef Str);
   static MDString *get(LLVMContext &Context, const char *Str) {
     return get(Context, Str ? StringRef(Str) : StringRef());

diff --git a/lib/IR/Metadata.cpp b/lib/IR/Metadata.cpp
index cc0c568..ddb9cc4 100644 (file)
--- a/lib/IR/Metadata.cpp
+++ b/lib/IR/Metadata.cpp
@@ -397,17 +397,12 @@ void ValueAsMetadata::handleRAUW(Value *From, Value *To) {
 
 MDString *MDString::get(LLVMContext &Context, StringRef Str) {
   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(), MDString());
-  bool WasInserted = Store.insert(Entry);
-  (void)WasInserted;
-  assert(WasInserted && "Expected entry to be inserted");
-  Entry->second.Entry = Entry;
-  return &Entry->second;
+  auto I = Store.insert(std::make_pair(Str, MDString()));
+  auto &MapEntry = I.first->getValue();
+  if (!I.second)
+    return &MapEntry;
+  MapEntry.Entry = &*I.first;
+  return &MapEntry;
 }
 
 StringRef MDString::getString() const {