Cleanup StringAddFlags.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index 1e1a2fc51e29064ef7d63edad18b4a67125358a5..7773667b7e91c5647ed72e776ca04a087367c0f7 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -1897,8 +1897,8 @@ void BinaryOpStub::GenerateBothStringStub(MacroAssembler* masm) {
   __ CompareObjectType(right, r2, r2, FIRST_NONSTRING_TYPE);
   __ b(ge, &call_runtime);
 
-  StringAddStub string_add_stub((StringAddFlags)
-                                (ERECT_FRAME | NO_STRING_CHECK_IN_STUB));
+  StringAddStub string_add_stub(
+      (StringAddFlags)(STRING_ADD_CHECK_NONE | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_stub);
 
@@ -2256,8 +2256,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ CompareObjectType(left, r2, r2, FIRST_NONSTRING_TYPE);
   __ b(ge, &left_not_string);
 
-  StringAddStub string_add_left_stub((StringAddFlags)
-      (ERECT_FRAME | NO_STRING_CHECK_LEFT_IN_STUB));
+  StringAddStub string_add_left_stub(
+      (StringAddFlags)(STRING_ADD_CHECK_RIGHT | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_left_stub);
 
@@ -2267,8 +2267,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ CompareObjectType(right, r2, r2, FIRST_NONSTRING_TYPE);
   __ b(ge, &call_runtime);
 
-  StringAddStub string_add_right_stub((StringAddFlags)
-      (ERECT_FRAME | NO_STRING_CHECK_RIGHT_IN_STUB));
+  StringAddStub string_add_right_stub(
+      (StringAddFlags)(STRING_ADD_CHECK_LEFT | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_right_stub);
 
@@ -5494,7 +5494,11 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ ldr(r1, MemOperand(sp, 0 * kPointerSize));  // Second argument.
 
   // Make sure that both arguments are strings if not known in advance.
-  if ((flags_ & NO_STRING_ADD_FLAGS) != 0) {
+  // Otherwise, at least one of the arguments is definitely a string,
+  // and we convert the one that is not known to be a string.
+  if ((flags_ & STRING_ADD_CHECK_BOTH) == STRING_ADD_CHECK_BOTH) {
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT);
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT);
     __ JumpIfEitherSmi(r0, r1, &call_runtime);
     // Load instance types.
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
@@ -5506,20 +5510,16 @@ void StringAddStub::Generate(MacroAssembler* masm) {
     __ tst(r4, Operand(kIsNotStringMask));
     __ tst(r5, Operand(kIsNotStringMask), eq);
     __ b(ne, &call_runtime);
-  } else {
-    // Here at least one of the arguments is definitely a string.
-    // We convert the one that is not known to be a string.
-    if ((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) == 0) {
-      ASSERT((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) != 0);
-      GenerateConvertArgument(
-          masm, 1 * kPointerSize, r0, r2, r3, r4, r5, &call_builtin);
-      builtin_id = Builtins::STRING_ADD_RIGHT;
-    } else if ((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) == 0) {
-      ASSERT((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) != 0);
-      GenerateConvertArgument(
-          masm, 0 * kPointerSize, r1, r2, r3, r4, r5, &call_builtin);
-      builtin_id = Builtins::STRING_ADD_LEFT;
-    }
+  } else if ((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT) {
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == 0);
+    GenerateConvertArgument(
+        masm, 1 * kPointerSize, r0, r2, r3, r4, r5, &call_builtin);
+    builtin_id = Builtins::STRING_ADD_RIGHT;
+  } else if ((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT) {
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == 0);
+    GenerateConvertArgument(
+        masm, 0 * kPointerSize, r1, r2, r3, r4, r5, &call_builtin);
+    builtin_id = Builtins::STRING_ADD_LEFT;
   }
 
   // Both arguments are strings.
@@ -5567,7 +5567,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ b(ne, &longer_than_two);
 
   // Check that both strings are non-external ASCII strings.
-  if (flags_ != NO_STRING_ADD_FLAGS) {
+  if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldr(r5, FieldMemOperand(r1, HeapObject::kMapOffset));
     __ ldrb(r4, FieldMemOperand(r4, Map::kInstanceTypeOffset));
@@ -5615,7 +5615,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
 
   // If result is not supposed to be flat, allocate a cons string object.
   // If both strings are ASCII the result is an ASCII cons string.
-  if (flags_ != NO_STRING_ADD_FLAGS) {
+  if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldr(r5, FieldMemOperand(r1, HeapObject::kMapOffset));
     __ ldrb(r4, FieldMemOperand(r4, Map::kInstanceTypeOffset));
@@ -5698,7 +5698,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   // r6: sum of lengths.
   Label first_prepared, second_prepared;
   __ bind(&string_add_flat_result);
-  if (flags_ != NO_STRING_ADD_FLAGS) {
+  if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldr(r5, FieldMemOperand(r1, HeapObject::kMapOffset));
     __ ldrb(r4, FieldMemOperand(r4, Map::kInstanceTypeOffset));
@@ -5786,7 +5786,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
 
   // Just jump to runtime to add the two strings.
   __ bind(&call_runtime);
-  if ((flags_ & ERECT_FRAME) != 0) {
+  if ((flags_ & STRING_ADD_ERECT_FRAME) != 0) {
     GenerateRegisterArgsPop(masm);
     // Build a frame
     {
@@ -5801,7 +5801,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
 
   if (call_builtin.is_linked()) {
     __ bind(&call_builtin);
-    if ((flags_ & ERECT_FRAME) != 0) {
+    if ((flags_ & STRING_ADD_ERECT_FRAME) != 0) {
       GenerateRegisterArgsPop(masm);
       // Build a frame
       {