ObjectiveC. add comment.

llvm-svn: 199257

clang/lib/CodeGen/CGObjCMac.cpp

@@ -4293,14 +4293,14 @@ llvm::Value *CGObjCMac::EmitIvarOffset(CodeGen::CodeGenFunction &CGF,
 ///   unsigned flags;
 /// };
 enum ImageInfoFlags {
-  eImageInfo_FixAndContinue      = (1 << 0),
+  eImageInfo_FixAndContinue      = (1 << 0), // no longer set by clang
   eImageInfo_GarbageCollected    = (1 << 1),
   eImageInfo_GCOnly              = (1 << 2),
-  eImageInfo_OptimizedByDyld     = (1 << 3), // FIXME: When is this set.
+  eImageInfo_OptimizedByDyld     = (1 << 3), // set by the dyld shared cache
 
   // A flag indicating that the module has no instances of a @synthesize of a
   // superclass variable. <rdar://problem/6803242>
-  eImageInfo_CorrectedSynthesize = (1 << 4),
+  eImageInfo_CorrectedSynthesize = (1 << 4), // no longer set by clang
   eImageInfo_ImageIsSimulated    = (1 << 5)
 };