On Sun, Feb 12, 2017 at 9:13 PM, Liu Hao <lh_mouse@xxxxxxx> wrote: > On 2017/2/13 9:59, Jeffrey Walton wrote: >> >> For x86 machines, you often want to use 'gcc -march=native -dM -E >> </dev/null | sort' (or similar). The '-march=native' is important to >> get most of the defines for the native machine. > > I know a few of them and am wondering whether they are subject to change in > future releases. I've never seen them change from GCC release to GCC release. Once they are added, they appear to be written in stone. Changing them would probably be a bad idea. The defines will change as you move from one processor to another. Xeon's seem to cause a lot of confusion. Folks will compile on one Xeon model, and then experience a SIGILL on another one. The difference between Xeon E5-2699v4 and Xeon E5-2699v3 is not very obvious until you realize its Broadwell (E5-2699v4) vs Haswell ( E5-2699v3). There are a few odd ones, like -mrdrnd and __RDRND__ for the rdrand instruction. In contrast, rdseed uses all the vowels: -mrdseed and __RDSEED__. Jeff
