add new isSingleStringRef()/getSingleStringRef() methods to twine,

and use them to avoid a copy of a string in getNameWithPrefix in
the common case.  It seems like Value::setName and other places 
should use this as well?


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93301 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/VMCore/Mangler.cpp b/lib/VMCore/Mangler.cpp
index 87a623a8f9..4d8a91cbf3 100644
--- a/lib/VMCore/Mangler.cpp
+++ b/lib/VMCore/Mangler.cpp
@@ -188,8 +188,13 @@ std::string Mangler::getMangledName(const GlobalValue *GV, const char *Suffix,
 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
                                 const Twine &GVName, ManglerPrefixTy PrefixTy) {
   SmallString<256> TmpData;
-  GVName.toVector(TmpData);
-  StringRef Name = TmpData.str();
+  StringRef Name;
+  if (GVName.isSingleStringRef())
+    Name = GVName.getSingleStringRef();
+  else {
+    GVName.toVector(TmpData);
+    Name = TmpData.str();
+  }
   assert(!Name.empty() && "getNameWithPrefix requires non-empty name");
   
   // If the global name is not led with \1, add the appropriate prefixes.