With >= 64 non-string instance types, I removed an optimization

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 0b74ace6f8b50b264021c7718fa726402bbb6017..36bd567cb6772d463ec95227290a4b89cc21f091 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -3230,10 +3230,9 @@ static void BranchIfNotInternalizedString(MacroAssembler* masm,
   __ movq(scratch, FieldOperand(object, HeapObject::kMapOffset));
   __ movzxbq(scratch,
              FieldOperand(scratch, Map::kInstanceTypeOffset));
-  STATIC_ASSERT(kInternalizedTag != 0);
-  __ and_(scratch, Immediate(kIsNotStringMask | kIsInternalizedMask));
-  __ cmpb(scratch, Immediate(kInternalizedTag | kStringTag));
-  __ j(not_equal, label);
+  STATIC_ASSERT(kInternalizedTag == 0 && kStringTag == 0);
+  __ testb(scratch, Immediate(kIsNotStringMask | kIsNotInternalizedMask));
+  __ j(not_zero, label);
 }
 
 
@@ -5652,14 +5651,10 @@ void ICCompareStub::GenerateInternalizedStrings(MacroAssembler* masm) {
   __ movq(tmp2, FieldOperand(right, HeapObject::kMapOffset));
   __ movzxbq(tmp1, FieldOperand(tmp1, Map::kInstanceTypeOffset));
   __ movzxbq(tmp2, FieldOperand(tmp2, Map::kInstanceTypeOffset));
-  STATIC_ASSERT(kInternalizedTag != 0);
-  __ and_(tmp1, Immediate(kIsNotStringMask | kIsInternalizedMask));
-  __ cmpb(tmp1, Immediate(kInternalizedTag | kStringTag));
-  __ j(not_equal, &miss, Label::kNear);
-
-  __ and_(tmp2, Immediate(kIsNotStringMask | kIsInternalizedMask));
-  __ cmpb(tmp2, Immediate(kInternalizedTag | kStringTag));
-  __ j(not_equal, &miss, Label::kNear);
+  STATIC_ASSERT(kInternalizedTag == 0 && kStringTag == 0);
+  __ or_(tmp1, tmp2);
+  __ testb(tmp1, Immediate(kIsNotStringMask | kIsNotInternalizedMask));
+  __ j(not_zero, &miss, Label::kNear);
 
   // Internalized strings are compared by identity.
   Label done;
@@ -5696,7 +5691,6 @@ void ICCompareStub::GenerateUniqueNames(MacroAssembler* masm) {
 
   // Check that both operands are unique names. This leaves the instance
   // types loaded in tmp1 and tmp2.
-  STATIC_ASSERT(kInternalizedTag != 0);
   __ movq(tmp1, FieldOperand(left, HeapObject::kMapOffset));
   __ movq(tmp2, FieldOperand(right, HeapObject::kMapOffset));
   __ movzxbq(tmp1, FieldOperand(tmp1, Map::kInstanceTypeOffset));
@@ -5769,10 +5763,10 @@ void ICCompareStub::GenerateStrings(MacroAssembler* masm) {
   // strings.
   if (equality) {
     Label do_compare;
-    STATIC_ASSERT(kInternalizedTag != 0);
-    __ and_(tmp1, tmp2);
-    __ testb(tmp1, Immediate(kIsInternalizedMask));
-    __ j(zero, &do_compare, Label::kNear);
+    STATIC_ASSERT(kInternalizedTag == 0);
+    __ or_(tmp1, tmp2);
+    __ testb(tmp1, Immediate(kIsNotInternalizedMask));
+    __ j(not_zero, &do_compare, Label::kNear);
     // Make sure rax is non-zero. At this point input operands are
     // guaranteed to be non-zero.
     ASSERT(right.is(rax));