Revert of [es5] Class of object is "Function" if object has [[Call]].

src/full-codegen/mips/full-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_MIPS
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 3658 matching lines @@
   // adaptor frame.
   __ lw(v0, MemOperand(a2, ArgumentsAdaptorFrameConstants::kLengthOffset));
 
   __ bind(&exit);
   context()->Plug(v0);
 }
 
 
 void FullCodeGenerator::EmitClassOf(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
-  DCHECK_EQ(1, args->length());
+  DCHECK(args->length() == 1);
   Label done, null, function, non_function_constructor;
 
   VisitForAccumulatorValue(args->at(0));
 
   // If the object is a smi, we return null.
   __ JumpIfSmi(v0, &null);
 
-  // If the object is not a receiver, we return null.
-  STATIC_ASSERT(LAST_JS_RECEIVER_TYPE == LAST_TYPE);
+  // Check that the object is a JS object but take special care of JS
+  // functions to make sure they have 'Function' as their class.
+  // Assume that there are only two callable types, and one of them is at
+  // either end of the type range for JS object types. Saves extra comparisons.
+  STATIC_ASSERT(NUM_OF_CALLABLE_SPEC_OBJECT_TYPES == 2);
   __ GetObjectType(v0, v0, a1);  // Map is now in v0.
-  __ Branch(&null, lt, a1, Operand(FIRST_JS_RECEIVER_TYPE));
+  __ Branch(&null, lt, a1, Operand(FIRST_SPEC_OBJECT_TYPE));
 
-  // According to ES5 section 15 Standard Built-in ECMAScript Objects, the
-  // [[Class]] of builtin objects is "Function" if a [[Call]] internal
-  // method is present.
-  __ lbu(a1, FieldMemOperand(v0, Map::kBitFieldOffset));
-  __ And(a1, a1, Operand(1 << Map::kIsCallable));
-  __ Branch(&function, ne, a1, Operand(zero_reg));
+  STATIC_ASSERT(FIRST_NONCALLABLE_SPEC_OBJECT_TYPE ==
+                FIRST_SPEC_OBJECT_TYPE + 1);
+  __ Branch(&function, eq, a1, Operand(FIRST_SPEC_OBJECT_TYPE));
+
+  STATIC_ASSERT(LAST_NONCALLABLE_SPEC_OBJECT_TYPE ==
+                LAST_SPEC_OBJECT_TYPE - 1);
+  __ Branch(&function, eq, a1, Operand(LAST_SPEC_OBJECT_TYPE));
+  // Assume that there is no larger type.
+  STATIC_ASSERT(LAST_NONCALLABLE_SPEC_OBJECT_TYPE == LAST_TYPE - 1);
 
   // Check if the constructor in the map is a JS function.
   Register instance_type = a2;
   __ GetMapConstructor(v0, v0, a1, instance_type);
   __ Branch(&non_function_constructor, ne, instance_type,
             Operand(JS_FUNCTION_TYPE));
 
   // v0 now contains the constructor function. Grab the
   // instance class name from there.
   __ lw(v0, FieldMemOperand(v0, JSFunction::kSharedFunctionInfoOffset));
@@ skipping 1607 matching lines @@
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS