Hej all. __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 is defined on x86_64 if and only if -mcx16 is given. gcc version 4.9.2 (Debian 4.9.2-10) winterflaw@localhost:~$ gcc -march=native -dM -E - < /dev/null | sort | grep SYNC #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1 __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 is not defined at all on aarch64, as far as I can tell. gcc version 4.9.2 (Debian/Linaro 4.9.2-10) debian@pine64:~$ gcc -march=armv8-a+crypto+crc -dM -E - < /dev/null | sort | grep SYNC #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1 Both are the OS provided GCCs (Debian 8 in both cases).
