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

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 7ea71e47eb059b1cf788c2970eddc211e00a5a02..fb8501039497a984572c1bf2894ce679f3fbbb20 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -5748,13 +5748,6 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   // edi: second instance type.
   __ test(ecx, Immediate(kAsciiDataHintMask));
   __ j(not_zero, &ascii_data);
-  __ mov(ecx, FieldOperand(eax, HeapObject::kMapOffset));
-  __ movzx_b(ecx, FieldOperand(ecx, Map::kInstanceTypeOffset));
-  __ xor_(edi, ecx);
-  STATIC_ASSERT(kOneByteStringTag != 0 && kAsciiDataHintTag != 0);
-  __ and_(edi, kOneByteStringTag | kAsciiDataHintTag);
-  __ cmp(edi, kOneByteStringTag | kAsciiDataHintTag);
-  __ j(equal, &ascii_data);
   // Allocate a two byte cons string.
   __ AllocateTwoByteConsString(ecx, edi, no_reg, &call_runtime);
   __ jmp(&allocated);