Cleanup StringAddFlags.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index f1c6c39b05ef8fa8764278ade8cdaeb63dce7993..83ea24770ce89b59cf770395944f11cd266fca53 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -2140,8 +2140,8 @@ void BinaryOpStub::GenerateBothStringStub(MacroAssembler* masm) {
   __ GetObjectType(right, a2, a2);
   __ Branch(&call_runtime, ge, a2, Operand(FIRST_NONSTRING_TYPE));
 
-  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);
 
@@ -2558,8 +2558,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ GetObjectType(left, a2, a2);
   __ Branch(&left_not_string, ge, a2, Operand(FIRST_NONSTRING_TYPE));
 
-  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);
 
@@ -2569,8 +2569,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ GetObjectType(right, a2, a2);
   __ Branch(&call_runtime, ge, a2, Operand(FIRST_NONSTRING_TYPE));
 
-  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);
 
@@ -5872,7 +5872,11 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ lw(a1, 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(a0, a1, &call_runtime);
     // Load instance types.
     __ lw(t0, FieldMemOperand(a0, HeapObject::kMapOffset));
@@ -5884,20 +5888,16 @@ void StringAddStub::Generate(MacroAssembler* masm) {
     __ Or(t4, t0, Operand(t1));
     __ And(t4, t4, Operand(kIsNotStringMask));
     __ Branch(&call_runtime, ne, t4, Operand(zero_reg));
-  } 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, a0, a2, a3, t0, t1, &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, a1, a2, a3, t0, t1, &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, a0, a2, a3, t0, t1, &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, a1, a2, a3, t0, t1, &call_builtin);
+    builtin_id = Builtins::STRING_ADD_LEFT;
   }
 
   // Both arguments are strings.
@@ -5948,7 +5948,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ Branch(&longer_than_two, ne, t2, Operand(2));
 
   // 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) {
     __ lw(t0, FieldMemOperand(a0, HeapObject::kMapOffset));
     __ lw(t1, FieldMemOperand(a1, HeapObject::kMapOffset));
     __ lbu(t0, FieldMemOperand(t0, Map::kInstanceTypeOffset));
@@ -5992,7 +5992,7 @@ 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) {
     __ lw(t0, FieldMemOperand(a0, HeapObject::kMapOffset));
     __ lw(t1, FieldMemOperand(a1, HeapObject::kMapOffset));
     __ lbu(t0, FieldMemOperand(t0, Map::kInstanceTypeOffset));
@@ -6075,7 +6075,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   // t2: 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) {
     __ lw(t0, FieldMemOperand(a0, HeapObject::kMapOffset));
     __ lw(t1, FieldMemOperand(a1, HeapObject::kMapOffset));
     __ lbu(t0, FieldMemOperand(t0, Map::kInstanceTypeOffset));
@@ -6161,7 +6161,7 @@ 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.
     {
@@ -6176,7 +6176,7 @@ 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.
       {