MC: Don't assume incoming StringRef's are null terminated.

This can happen when processing command line arguments, which
are often stored as std::string's and later turned into
StringRef's via std::string::data().  Unfortunately this
is not guaranteed to return a null-terminated string
until C++11, causing breakage on platforms that don't do this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192558 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/SubtargetFeature.h

@@ -37,9 +37,9 @@ struct SubtargetFeatureKV {
   uint64_t Value;                       // K-V integer value
   uint64_t Implies;                     // K-V bit mask
 
-  // Compare routine for std binary search
-  bool operator<(const SubtargetFeatureKV &S) const {
-    return strcmp(Key, S.Key) < 0;
+  // Compare routine for std::lower_bound
+  bool operator<(StringRef S) const {
+    return StringRef(Key) < S;
   }
 };
 
@@ -52,9 +52,9 @@ struct SubtargetInfoKV {
   const char *Key;                      // K-V key string
   const void *Value;                    // K-V pointer value
 
-  // Compare routine for std binary search
-  bool operator<(const SubtargetInfoKV &S) const {
-    return strcmp(Key, S.Key) < 0;
+  // Compare routine for std::lower_bound
+  bool operator<(StringRef S) const {
+    return StringRef(Key) < S;
   }
 };