Revert of Remove SIMD.js from V8.

src/js/macros.py

Index: src/js/macros.py
diff --git a/src/js/macros.py b/src/js/macros.py
index f10da42c655ed9bb77be8c8955343948d277b086..fc564ff97cd758658b30a10a6039fbbba05677b9 100644
--- a/src/js/macros.py
+++ b/src/js/macros.py
@@ -64,6 +64,7 @@
 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));