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.

llvm-svn: 192558

llvm/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;
   }
 };
 

llvm/lib/MC/MCSubtargetInfo.cpp

@@ -96,10 +96,8 @@ MCSubtargetInfo::getSchedModelForCPU(StringRef CPU) const {
 #endif
 
   // Find entry
-  SubtargetInfoKV KV;
-  KV.Key = CPU.data();
   const SubtargetInfoKV *Found =
-    std::lower_bound(ProcSchedModels, ProcSchedModels+NumProcs, KV);
+    std::lower_bound(ProcSchedModels, ProcSchedModels+NumProcs, CPU);
   if (Found == ProcSchedModels+NumProcs || StringRef(Found->Key) != CPU) {
     errs() << "'" << CPU
            << "' is not a recognized processor for this target"

llvm/lib/MC/SubtargetFeature.cpp

@@ -121,13 +121,10 @@ void SubtargetFeatures::AddFeature(const StringRef String,
 /// Find KV in array using binary search.
 static const SubtargetFeatureKV *Find(StringRef S, const SubtargetFeatureKV *A,
                                       size_t L) {
-  // Make the lower bound element we're looking for
-  SubtargetFeatureKV KV;
-  KV.Key = S.data();
   // Determine the end of the array
   const SubtargetFeatureKV *Hi = A + L;
   // Binary search the array
-  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, KV);
+  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, S);
   // If not found then return NULL
   if (F == Hi || StringRef(F->Key) != S) return NULL;
   // Return the found array item