Make kAsciiDataHintTag have correct semantics for all both 1 and 2 byte string types.

src/ia32/macro-assembler-ia32.cc

 // Copyright 2012 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 2620 matching lines @@
   and_(scratch1, object2);
   JumpIfSmi(scratch1, failure);
 
   // Load instance type for both strings.
   mov(scratch1, FieldOperand(object1, HeapObject::kMapOffset));
   mov(scratch2, FieldOperand(object2, HeapObject::kMapOffset));
   movzx_b(scratch1, FieldOperand(scratch1, Map::kInstanceTypeOffset));
   movzx_b(scratch2, FieldOperand(scratch2, Map::kInstanceTypeOffset));
 
   // Check that both are flat ASCII strings.
-  const int kFlatAsciiStringMask =
-      kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask;
+  const int kFlatAsciiStringMask = kIsNotStringMask | kStringRepresentationMask
+          | kStringEncodingMask | kAsciiDataHintTag;
   const int kFlatAsciiStringTag = ASCII_STRING_TYPE;
   // Interleave bits from both instance types and compare them in one check.
-  ASSERT_EQ(0, kFlatAsciiStringMask & (kFlatAsciiStringMask << 3));
+  ASSERT_EQ(0, kFlatAsciiStringMask & (kFlatAsciiStringMask << 8));
+  ASSERT_EQ(ASCII_STRING_TYPE, ASCII_STRING_TYPE & kFlatAsciiStringMask);
   and_(scratch1, kFlatAsciiStringMask);
   and_(scratch2, kFlatAsciiStringMask);
-  lea(scratch1, Operand(scratch1, scratch2, times_8, 0));
-  cmp(scratch1, kFlatAsciiStringTag | (kFlatAsciiStringTag << 3));
+  shl(scratch1, 8);
+  or_(scratch1, scratch2);
+  cmp(scratch1, kFlatAsciiStringTag | (kFlatAsciiStringTag << 8));
   j(not_equal, failure);
 }
 
 
 void MacroAssembler::PrepareCallCFunction(int num_arguments, Register scratch) {
   int frame_alignment = OS::ActivationFrameAlignment();
   if (frame_alignment != 0) {
     // Make stack end at alignment and make room for num_arguments words
     // and the original value of esp.
     mov(scratch, esp);
@@ skipping 317 matching lines @@
   j(not_equal, call_runtime);
 
   mov(ecx, FieldOperand(ebx, Map::kPrototypeOffset));
   cmp(ecx, isolate()->factory()->null_value());
   j(not_equal, &next);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32