diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 7e594a2..2ca52a4 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -22,7 +22,6 @@
 #include "llvm/DerivedTypes.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/SelectionDAG.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
@@ -2365,7 +2364,7 @@
   assert(*(Constraint.end()-1) == '}' && "Not a brace enclosed constraint?");
 
   // Remove the braces from around the name.
-  std::string RegName(Constraint.begin()+1, Constraint.end()-1);
+  StringRef RegName(Constraint.data()+1, Constraint.size()-2);
 
   // Figure out which register class contains this reg.
   const TargetRegisterInfo *RI = TM.getRegisterInfo();
@@ -2388,7 +2387,7 @@
     
     for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); 
          I != E; ++I) {
-      if (StringsEqualNoCase(RegName, RI->getName(*I)))
+      if (RegName.equals_lower(RI->getName(*I)))
         return std::make_pair(*I, RC);
     }
   }
diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index 6905edf..51e1100 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -15,6 +15,26 @@
 const size_t StringRef::npos;
 #endif
 
+static char ascii_tolower(char x) {
+  if (x >= 'A' && x <= 'Z')
+    return x - 'A' + 'a';
+  return x;
+}
+
+/// compare_lower - Compare strings, ignoring case.
+int StringRef::compare_lower(StringRef RHS) const {
+  for (size_t I = 0, E = std::min(Length, RHS.Length); I != E; ++I) {
+    char LHC = ascii_tolower(Data[I]);
+    char RHC = ascii_tolower(RHS.Data[I]);
+    if (LHC != RHC)
+      return LHC < RHC ? -1 : 1;
+  }
+
+  if (Length == RHS.Length)
+        return 0;
+  return Length < RHS.Length ? -1 : 1;
+}
+
 //===----------------------------------------------------------------------===//
 // String Searching
 //===----------------------------------------------------------------------===//
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 1b67159..7da1d1c 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9595,14 +9595,14 @@
     }
 
     // GCC allows "st(0)" to be called just plain "st".
-    if (StringsEqualNoCase("{st}", Constraint)) {
+    if (StringRef("{st}").equals_lower(Constraint)) {
       Res.first = X86::ST0;
       Res.second = X86::RFP80RegisterClass;
       return Res;
     }
 
     // flags -> EFLAGS
-    if (StringsEqualNoCase("{flags}", Constraint)) {
+    if (StringRef("{flags}").equals_lower(Constraint)) {
       Res.first = X86::EFLAGS;
       Res.second = X86::CCRRegisterClass;
       return Res;