Index: /Source/JavaScriptCore/heap/GCMemoryOperations.h
===================================================================
--- /Source/JavaScriptCore/heap/GCMemoryOperations.h	(revision 261325)
+++ /Source/JavaScriptCore/heap/GCMemoryOperations.h	(revision 261326)
@@ -54,5 +54,5 @@
     };
 
-#if COMPILER(GCC_COMPATIBLE) && USE(JSVALUE64)
+#if COMPILER(GCC_COMPATIBLE) && (CPU(X86_64) || CPU(ARM64))
     if (bytes <= smallCutoff)
         slowPathForwardMemcpy();
@@ -122,6 +122,4 @@
             : "d0", "d1", "memory"
         );
-#else
-    slowPathForwardMemcpy();
 #endif // CPU(X86_64)
     } else {
@@ -140,5 +138,5 @@
 #else
     slowPathForwardMemcpy();
-#endif // COMPILER(GCC_COMPATIBLE)
+#endif // COMPILER(GCC_COMPATIBLE) && (CPU(X86_64) || CPU(ARM64))
 #else
     memcpy(dst, src, bytes);