A64: Synchronize with r15358.

src/a64/ic-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 310 matching lines @@
                       not_unique, hi);
   STATIC_ASSERT(LAST_UNIQUE_NAME_TYPE == FIRST_NONSTRING_TYPE);
   __ B(eq, &unique);
 
   // Is the string an array index with cached numeric value?
   __ Ldr(hash_scratch.W(), FieldMemOperand(key, Name::kHashFieldOffset));
   __ TestAndBranchIfAllClear(hash_scratch,
                              Name::kContainsCachedArrayIndexMask,
                              index_string);
 
-  // Is the string internalized?
+  // Is the string internalized? We know it's a string, so a single bit test is
+  // enough.
   __ Ldrb(hash_scratch, FieldMemOperand(map_scratch, Map::kInstanceTypeOffset));
   STATIC_ASSERT(kInternalizedTag != 0);
   __ TestAndBranchIfAllClear(hash_scratch, kIsInternalizedMask,
                              not_unique);
 
   __ Bind(&unique);
   // Fall through if the key is a unique name.
 }
 
 
@@ skipping 1507 matching lines @@
     ASSERT(to_patch->Mask(TestBranchMask) == TBNZ);
     // This is JumpIfSmi(smi_reg, branch_imm).
     patcher.tbz(smi_reg, 0, branch_imm);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_A64