Replace (Lower|Upper)caseString in favor of StringRef's newest methods.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143891 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/AsmParser/X86AsmParser.cpp b/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 6bedd52..f4639a3 100644
--- a/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -20,7 +20,6 @@
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/SourceMgr.h"
@@ -412,7 +411,7 @@
 
   // If the match failed, try the register name as lowercase.
   if (RegNo == 0)
-    RegNo = MatchRegisterName(LowercaseString(Tok.getString()));
+    RegNo = MatchRegisterName(Tok.getString().lower());
 
   if (!is64BitMode()) {
     // FIXME: This should be done using Requires<In32BitMode> and