On 26/06/17 08:37, Toebs Douglass wrote: > 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). > > This is correct. AArch64 cannot do the 16-byte atomic compare and swap and needs lock operations. R.
