Revert of [regexp] Remove IsRegExp intrinsic

src/js/macros.py

 # Copyright 2006-2009 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 42 matching lines @@
 macro IS_FUNCTION(arg)          = (%IsFunction(arg));
 macro IS_GENERATOR(arg)         = (%_ClassOf(arg) === 'Generator');
 macro IS_GLOBAL(arg)            = (%_ClassOf(arg) === 'global');
 macro IS_MAP(arg)               = (%_ClassOf(arg) === 'Map');
 macro IS_MAP_ITERATOR(arg)      = (%_ClassOf(arg) === 'Map Iterator');
 macro IS_NULL(arg)              = (arg === null);
 macro IS_NULL_OR_UNDEFINED(arg) = (arg == null);
 macro IS_NUMBER(arg)            = (typeof(arg) === 'number');
 macro IS_OBJECT(arg)            = (typeof(arg) === 'object');
 macro IS_PROXY(arg)             = (%_IsJSProxy(arg));
+macro IS_REGEXP(arg)            = (%_IsRegExp(arg));
 macro IS_SCRIPT(arg)            = (%_ClassOf(arg) === 'Script');
 macro IS_SET(arg)               = (%_ClassOf(arg) === 'Set');
 macro IS_SET_ITERATOR(arg)      = (%_ClassOf(arg) === 'Set Iterator');
 macro IS_SHAREDARRAYBUFFER(arg) = (%_ClassOf(arg) === 'SharedArrayBuffer');
 macro IS_SIMD_VALUE(arg)        = (%IsSimdValue(arg));
 macro IS_STRING(arg)            = (typeof(arg) === 'string');
 macro IS_SYMBOL(arg)            = (typeof(arg) === 'symbol');
 macro IS_TYPEDARRAY(arg)        = (%_IsTypedArray(arg));
 macro IS_UNDEFINED(arg)         = (arg === (void 0));
 macro IS_WEAKMAP(arg)           = (%_ClassOf(arg) === 'WeakMap');
@@ skipping 126 matching lines @@
 
 # [[PromiseState]] values:
 # These values must be kept in sync with v8::Promise::PromiseState in
 # include/v8.h
 define kPending = 0;
 define kFulfilled = 1;
 define kRejected = 2;
 
 define kResolveCallback = 0;
 define kRejectCallback = 1;