Cleanup StringAddFlags.

Avoid duplication of StringAddFlags in the platform specific code stubs header files.
Fix the inverted flag logic, replacing it with a scheme that is easier to understand.

Depends on: https://codereview.chromium.org/19541003

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/19492006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15775 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

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)
+  StringAddStub string_add_stub(
-                                (ERECT_FRAME | NO_STRING_CHECK_IN_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)
+  StringAddStub string_add_left_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_LEFT_IN_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)
+  StringAddStub string_add_right_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_RIGHT_IN_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 {
+  } else if ((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT) {
-    // Here at least one of the arguments is definitely a string.
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == 0);
-    // We convert the one that is not known to be a string.
+    GenerateConvertArgument(
-    if ((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) == 0) {
+        masm, 1 * kPointerSize, r0, r2, r3, r4, r5, &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_RIGHT;
-      GenerateConvertArgument(
+  } else if ((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT) {
-          masm, 1 * kPointerSize, r0, r2, r3, r4, r5, &call_builtin);
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == 0);
-      builtin_id = Builtins::STRING_ADD_RIGHT;
+    GenerateConvertArgument(
-    } else if ((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) == 0) {
+        masm, 0 * kPointerSize, r1, r2, r3, r4, r5, &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_LEFT;
-      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
       {

src/arm/code-stubs-arm.h

@@ -144,21 +144,6 @@ class StringHelper : public AllStatic {
 };
 
 
-// Flag that indicates how to generate code for the stub StringAddStub.
-enum StringAddFlags {
-  NO_STRING_ADD_FLAGS = 1 << 0,
-  // Omit left string check in stub (left is definitely a string).
-  NO_STRING_CHECK_LEFT_IN_STUB = 1 << 1,
-  // Omit right string check in stub (right is definitely a string).
-  NO_STRING_CHECK_RIGHT_IN_STUB = 1 << 2,
-  // Stub needs a frame before calling the runtime
-  ERECT_FRAME = 1 << 3,
-  // Omit both string checks in stub.
-  NO_STRING_CHECK_IN_STUB =
-      NO_STRING_CHECK_LEFT_IN_STUB | NO_STRING_CHECK_RIGHT_IN_STUB
-};
-
-
 class StringAddStub: public PlatformCodeStub {
  public:
   explicit StringAddStub(StringAddFlags flags) : flags_(flags) {}

src/arm/full-codegen-arm.cc

@@ -3719,7 +3719,7 @@ void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   VisitForStackValue(args->at(0));
   VisitForStackValue(args->at(1));
 
-  StringAddStub stub(NO_STRING_ADD_FLAGS);
+  StringAddStub stub(STRING_ADD_CHECK_BOTH);
   __ CallStub(&stub);
   context()->Plug(r0);
 }

src/code-stubs.h

@@ -393,6 +393,22 @@ class RuntimeCallHelper {
   DISALLOW_COPY_AND_ASSIGN(RuntimeCallHelper);
 };
 
+
+// TODO(bmeurer): Move to the StringAddStub declaration once we're
+// done with the translation to a hydrogen code stub.
+enum StringAddFlags {
+  // Omit both parameter checks.
+  STRING_ADD_CHECK_NONE = 0,
+  // Check left parameter.
+  STRING_ADD_CHECK_LEFT = 1 << 0,
+  // Check right parameter.
+  STRING_ADD_CHECK_RIGHT = 1 << 1,
+  // Check both parameters.
+  STRING_ADD_CHECK_BOTH = STRING_ADD_CHECK_LEFT | STRING_ADD_CHECK_RIGHT,
+  // Stub needs a frame before calling the runtime
+  STRING_ADD_ERECT_FRAME = 1 << 2
+};
+
 } }  // namespace v8::internal
 
 #if V8_TARGET_ARCH_IA32

src/hydrogen-instructions.h

@@ -6182,7 +6182,7 @@ class HStringAdd: public HBinaryOperation {
                            HValue* context,
                            HValue* left,
                            HValue* right,
-                           StringAddFlags flags = NO_STRING_CHECK_IN_STUB);
+                           StringAddFlags flags = STRING_ADD_CHECK_NONE);
 
   StringAddFlags flags() const { return flags_; }
 

src/hydrogen.cc

@@ -9083,7 +9083,7 @@ void HOptimizedGraphBuilder::GenerateStringAdd(CallRuntime* call) {
   HValue* left = Pop();
   HValue* context = environment()->LookupContext();
   HInstruction* result = HStringAdd::New(
-      zone(), context, left, right, NO_STRING_ADD_FLAGS);
+      zone(), context, left, right, STRING_ADD_CHECK_BOTH);
   return ast_context()->ReturnInstruction(result, call->id());
 }
 

src/ia32/code-stubs-ia32.cc

@@ -1353,8 +1353,8 @@ void BinaryOpStub::GenerateBothStringStub(MacroAssembler* masm) {
   __ CmpObjectType(right, FIRST_NONSTRING_TYPE, ecx);
   __ j(above_equal, &call_runtime, Label::kNear);
 
-  StringAddStub string_add_stub((StringAddFlags)
+  StringAddStub string_add_stub(
-                                (ERECT_FRAME | NO_STRING_CHECK_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_NONE | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_stub);
 
@@ -1999,8 +1999,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ CmpObjectType(left, FIRST_NONSTRING_TYPE, ecx);
   __ j(above_equal, &left_not_string, Label::kNear);
 
-  StringAddStub string_add_left_stub((StringAddFlags)
+  StringAddStub string_add_left_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_LEFT_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_RIGHT | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_left_stub);
 
@@ -2010,8 +2010,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ CmpObjectType(right, FIRST_NONSTRING_TYPE, ecx);
   __ j(above_equal, &call_runtime, Label::kNear);
 
-  StringAddStub string_add_right_stub((StringAddFlags)
+  StringAddStub string_add_right_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_RIGHT_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_LEFT | STRING_ADD_ERECT_FRAME));
   GenerateRegisterArgsPush(masm);
   __ TailCallStub(&string_add_right_stub);
 
@@ -5376,7 +5376,11 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ mov(edx, Operand(esp, 1 * 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);
     __ JumpIfSmi(eax, &call_runtime);
     __ CmpObjectType(eax, FIRST_NONSTRING_TYPE, ebx);
     __ j(above_equal, &call_runtime);
@@ -5385,20 +5389,16 @@ void StringAddStub::Generate(MacroAssembler* masm) {
     __ JumpIfSmi(edx, &call_runtime);
     __ CmpObjectType(edx, FIRST_NONSTRING_TYPE, ebx);
     __ j(above_equal, &call_runtime);
-  } else {
+  } else if ((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT) {
-    // Here at least one of the arguments is definitely a string.
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == 0);
-    // We convert the one that is not known to be a string.
+    GenerateConvertArgument(masm, 2 * kPointerSize, eax, ebx, ecx, edi,
-    if ((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) == 0) {
+                            &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_RIGHT;
-      GenerateConvertArgument(masm, 2 * kPointerSize, eax, ebx, ecx, edi,
+  } else if ((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT) {
-                              &call_builtin);
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == 0);
-      builtin_id = Builtins::STRING_ADD_RIGHT;
+    GenerateConvertArgument(masm, 1 * kPointerSize, edx, ebx, ecx, edi,
-    } else if ((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) == 0) {
+                            &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_LEFT;
-      GenerateConvertArgument(masm, 1 * kPointerSize, edx, ebx, ecx, edi,
-                              &call_builtin);
-      builtin_id = Builtins::STRING_ADD_LEFT;
-    }
   }
 
   // Both arguments are strings.
@@ -5684,7 +5684,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ Drop(2);
   // 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, ecx);
     // Build a frame
     {
@@ -5699,7 +5699,7 @@ 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, ecx);
       // Build a frame
       {

src/ia32/code-stubs-ia32.h

@@ -144,20 +144,6 @@ class StringHelper : public AllStatic {
 };
 
 
-enum StringAddFlags {
-  NO_STRING_ADD_FLAGS = 1 << 0,
-  // Omit left string check in stub (left is definitely a string).
-  NO_STRING_CHECK_LEFT_IN_STUB = 1 << 1,
-  // Omit right string check in stub (right is definitely a string).
-  NO_STRING_CHECK_RIGHT_IN_STUB = 1 << 2,
-  // Stub needs a frame before calling the runtime
-  ERECT_FRAME = 1 << 3,
-  // Omit both string checks in stub.
-  NO_STRING_CHECK_IN_STUB =
-      NO_STRING_CHECK_LEFT_IN_STUB | NO_STRING_CHECK_RIGHT_IN_STUB
-};
-
-
 class StringAddStub: public PlatformCodeStub {
  public:
   explicit StringAddStub(StringAddFlags flags) : flags_(flags) {}

src/ia32/full-codegen-ia32.cc

@@ -3685,7 +3685,7 @@ void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   VisitForStackValue(args->at(0));
   VisitForStackValue(args->at(1));
 
-  StringAddStub stub(NO_STRING_ADD_FLAGS);
+  StringAddStub stub(STRING_ADD_CHECK_BOTH);
   __ CallStub(&stub);
   context()->Plug(eax);
 }

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)
+  StringAddStub string_add_stub(
-                                (ERECT_FRAME | NO_STRING_CHECK_IN_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)
+  StringAddStub string_add_left_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_LEFT_IN_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)
+  StringAddStub string_add_right_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_RIGHT_IN_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 {
+  } else if ((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT) {
-    // Here at least one of the arguments is definitely a string.
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == 0);
-    // We convert the one that is not known to be a string.
+    GenerateConvertArgument(
-    if ((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) == 0) {
+        masm, 1 * kPointerSize, a0, a2, a3, t0, t1, &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_RIGHT;
-      GenerateConvertArgument(
+  } else if ((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT) {
-          masm, 1 * kPointerSize, a0, a2, a3, t0, t1, &call_builtin);
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == 0);
-      builtin_id = Builtins::STRING_ADD_RIGHT;
+    GenerateConvertArgument(
-    } else if ((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) == 0) {
+        masm, 0 * kPointerSize, a1, a2, a3, t0, t1, &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_LEFT;
-      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.
       {

src/mips/code-stubs-mips.h

@@ -145,21 +145,6 @@ class StringHelper : public AllStatic {
 };
 
 
-// Flag that indicates how to generate code for the stub StringAddStub.
-enum StringAddFlags {
-  NO_STRING_ADD_FLAGS = 1 << 0,
-  // Omit left string check in stub (left is definitely a string).
-  NO_STRING_CHECK_LEFT_IN_STUB = 1 << 1,
-  // Omit right string check in stub (right is definitely a string).
-  NO_STRING_CHECK_RIGHT_IN_STUB = 1 << 2,
-  // Stub needs a frame before calling the runtime
-  ERECT_FRAME = 1 << 3,
-  // Omit both string checks in stub.
-  NO_STRING_CHECK_IN_STUB =
-      NO_STRING_CHECK_LEFT_IN_STUB | NO_STRING_CHECK_RIGHT_IN_STUB
-};
-
-
 class StringAddStub: public PlatformCodeStub {
  public:
   explicit StringAddStub(StringAddFlags flags) : flags_(flags) {}

src/mips/full-codegen-mips.cc

@@ -3746,7 +3746,7 @@ void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   VisitForStackValue(args->at(0));
   VisitForStackValue(args->at(1));
 
-  StringAddStub stub(NO_STRING_ADD_FLAGS);
+  StringAddStub stub(STRING_ADD_CHECK_BOTH);
   __ CallStub(&stub);
   context()->Plug(v0);
 }

src/x64/code-stubs-x64.cc

@@ -1014,8 +1014,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ JumpIfSmi(left, &left_not_string, Label::kNear);
   __ CmpObjectType(left, FIRST_NONSTRING_TYPE, rcx);
   __ j(above_equal, &left_not_string, Label::kNear);
-  StringAddStub string_add_left_stub((StringAddFlags)
+  StringAddStub string_add_left_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_LEFT_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_RIGHT | STRING_ADD_ERECT_FRAME));
   BinaryOpStub_GenerateRegisterArgsPushUnderReturn(masm);
   __ TailCallStub(&string_add_left_stub);
 
@@ -1025,8 +1025,8 @@ void BinaryOpStub::GenerateAddStrings(MacroAssembler* masm) {
   __ CmpObjectType(right, FIRST_NONSTRING_TYPE, rcx);
   __ j(above_equal, &call_runtime, Label::kNear);
 
-  StringAddStub string_add_right_stub((StringAddFlags)
+  StringAddStub string_add_right_stub(
-      (ERECT_FRAME | NO_STRING_CHECK_RIGHT_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_LEFT | STRING_ADD_ERECT_FRAME));
   BinaryOpStub_GenerateRegisterArgsPushUnderReturn(masm);
   __ TailCallStub(&string_add_right_stub);
 
@@ -1101,8 +1101,8 @@ void BinaryOpStub::GenerateBothStringStub(MacroAssembler* masm) {
   __ CmpObjectType(right, FIRST_NONSTRING_TYPE, rcx);
   __ j(above_equal, &call_runtime);
 
-  StringAddStub string_add_stub((StringAddFlags)
+  StringAddStub string_add_stub(
-                                (ERECT_FRAME | NO_STRING_CHECK_IN_STUB));
+      (StringAddFlags)(STRING_ADD_CHECK_NONE | STRING_ADD_ERECT_FRAME));
   BinaryOpStub_GenerateRegisterArgsPushUnderReturn(masm);
   __ TailCallStub(&string_add_stub);
 
@@ -4516,7 +4516,11 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ movq(rdx, Operand(rsp, 1 * kPointerSize));  // Second argument (right).
 
   // 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);
     __ JumpIfSmi(rax, &call_runtime);
     __ CmpObjectType(rax, FIRST_NONSTRING_TYPE, r8);
     __ j(above_equal, &call_runtime);
@@ -4525,20 +4529,16 @@ void StringAddStub::Generate(MacroAssembler* masm) {
     __ JumpIfSmi(rdx, &call_runtime);
     __ CmpObjectType(rdx, FIRST_NONSTRING_TYPE, r9);
     __ j(above_equal, &call_runtime);
-  } else {
+  } else if ((flags_ & STRING_ADD_CHECK_LEFT) == STRING_ADD_CHECK_LEFT) {
-    // Here at least one of the arguments is definitely a string.
+    ASSERT((flags_ & STRING_ADD_CHECK_RIGHT) == 0);
-    // We convert the one that is not known to be a string.
+    GenerateConvertArgument(masm, 2 * kPointerSize, rax, rbx, rcx, rdi,
-    if ((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) == 0) {
+                            &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_RIGHT;
-      GenerateConvertArgument(masm, 2 * kPointerSize, rax, rbx, rcx, rdi,
+  } else if ((flags_ & STRING_ADD_CHECK_RIGHT) == STRING_ADD_CHECK_RIGHT) {
-                              &call_builtin);
+    ASSERT((flags_ & STRING_ADD_CHECK_LEFT) == 0);
-      builtin_id = Builtins::STRING_ADD_RIGHT;
+    GenerateConvertArgument(masm, 1 * kPointerSize, rdx, rbx, rcx, rdi,
-    } else if ((flags_ & NO_STRING_CHECK_RIGHT_IN_STUB) == 0) {
+                            &call_builtin);
-      ASSERT((flags_ & NO_STRING_CHECK_LEFT_IN_STUB) != 0);
+    builtin_id = Builtins::STRING_ADD_LEFT;
-      GenerateConvertArgument(masm, 1 * kPointerSize, rdx, rbx, rcx, rdi,
-                              &call_builtin);
-      builtin_id = Builtins::STRING_ADD_LEFT;
-    }
   }
 
   // Both arguments are strings.
@@ -4574,7 +4574,7 @@ void StringAddStub::Generate(MacroAssembler* masm) {
 
   // If arguments where known to be strings, maps are not loaded to r8 and r9
   // by the code above.
-  if (flags_ != NO_STRING_ADD_FLAGS) {
+  if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ movq(r8, FieldOperand(rax, HeapObject::kMapOffset));
     __ movq(r9, FieldOperand(rdx, HeapObject::kMapOffset));
   }
@@ -4794,7 +4794,7 @@ 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, rcx);
     // Build a frame
     {
@@ -4809,7 +4809,7 @@ 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, rcx);
       // Build a frame
       {

src/x64/code-stubs-x64.h

@@ -134,21 +134,6 @@ class StringHelper : public AllStatic {
 };
 
 
-// Flag that indicates how to generate code for the stub StringAddStub.
-enum StringAddFlags {
-  NO_STRING_ADD_FLAGS = 1 << 0,
-  // Omit left string check in stub (left is definitely a string).
-  NO_STRING_CHECK_LEFT_IN_STUB = 1 << 1,
-  // Omit right string check in stub (right is definitely a string).
-  NO_STRING_CHECK_RIGHT_IN_STUB = 1 << 2,
-  // Stub needs a frame before calling the runtime
-  ERECT_FRAME = 1 << 3,
-  // Omit both string checks in stub.
-  NO_STRING_CHECK_IN_STUB =
-      NO_STRING_CHECK_LEFT_IN_STUB | NO_STRING_CHECK_RIGHT_IN_STUB
-};
-
-
 class StringAddStub: public PlatformCodeStub {
  public:
   explicit StringAddStub(StringAddFlags flags) : flags_(flags) {}

src/x64/full-codegen-x64.cc

@@ -3645,7 +3645,7 @@ void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   VisitForStackValue(args->at(0));
   VisitForStackValue(args->at(1));
 
-  StringAddStub stub(NO_STRING_ADD_FLAGS);
+  StringAddStub stub(STRING_ADD_CHECK_BOTH);
   __ CallStub(&stub);
   context()->Plug(rax);
 }