[TableGen] Return StringRef from ValueTypeByHwMode::getMVTName

Avoid unnecessary std::string creations during TypeSetByHwMode::writeToStream.

Found during investigations into PR28222

Differential Revision: https://reviews.llvm.org/D38174

llvm-svn: 313983

2 files changed, 5 insertions, 6 deletions

diff --git a/llvm/utils/TableGen/InfoByHwMode.cpp b/llvm/utils/TableGen/InfoByHwMode.cpp
index 882a6a78509..aee0dd6fa6a 100644
--- a/llvm/utils/TableGen/InfoByHwMode.cpp
+++ b/llvm/utils/TableGen/InfoByHwMode.cpp
@@ -70,10 +70,9 @@ MVT &ValueTypeByHwMode::getOrCreateTypeForMode(unsigned Mode, MVT Type) {
   return Map.insert(std::make_pair(Mode, Type)).first->second;
 }
 
-std::string ValueTypeByHwMode::getMVTName(MVT T) {
-  std::string N = llvm::getEnumName(T.SimpleTy);
-  if (N.substr(0,5) == "MVT::")
-    N = N.substr(5);
+StringRef ValueTypeByHwMode::getMVTName(MVT T) {
+  StringRef N = llvm::getEnumName(T.SimpleTy);
+  N.consume_front("MVT::");
   return N;
 }
 
@@ -91,7 +90,7 @@ std::string ValueTypeByHwMode::getAsString() const {
   for (unsigned i = 0, e = Pairs.size(); i != e; ++i) {
     const PairType *P = Pairs[i];
     str << '(' << getModeName(P->first)
-        << ':' << getMVTName(P->second) << ')';
+        << ':' << getMVTName(P->second).str() << ')';
     if (i != e-1)
       str << ',';
   }
diff --git a/llvm/utils/TableGen/InfoByHwMode.h b/llvm/utils/TableGen/InfoByHwMode.h
index 71149e8da19..57640fc3025 100644
--- a/llvm/utils/TableGen/InfoByHwMode.h
+++ b/llvm/utils/TableGen/InfoByHwMode.h
@@ -129,7 +129,7 @@ struct ValueTypeByHwMode : public InfoByHwMode<MVT> {
   MVT getType(unsigned Mode) const { return get(Mode); }
   MVT &getOrCreateTypeForMode(unsigned Mode, MVT Type);
 
-  static std::string getMVTName(MVT T);
+  static StringRef getMVTName(MVT T);
   std::string getAsString() const;
   void dump() const;
 };