diff --git a/js/src/assembler/wtf/Platform.h b/js/src/assembler/wtf/Platform.h

--- a/js/src/assembler/wtf/Platform.h

+++ b/js/src/assembler/wtf/Platform.h

@@ -205,16 +205,23 @@

 #endif

 /* WTF_CPU_S390 - S390 32-bit */

 #if defined(__s390__)

 #define WTF_CPU_S390 1

 #define WTF_CPU_BIG_ENDIAN 1

 #endif

+#if defined(__aarch64__)

+#define WTF_CPU_AARCH64 1

+#if defined(__AARCH64EB__)

+#define WTF_CPU_BIG_ENDIAN 1

+#endif

+#endif

+

 /* WTF_CPU_X86 - i386 / x86 32-bit */

 #if   defined(__i386__) \

     || defined(i386)     \

     || defined(_M_IX86)  \

     || defined(_X86_)    \

     || defined(__THW_INTEL)

 #define WTF_CPU_X86 1

 #endif