-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Dominik 'Rathann' Mierzejewski wrote: > I'd like to see a case (not involving Pentium 4) where using cmov is slower > than not using it. It definitely is faster for decoding H.264 in FFmpeg > for example. I don't have a specific test case. But I do talk to the CPU architectures at Intel regularly. They always say the cmov should be avoided. Especially with the introduction of the fused micro-ops the various cmp+jcc pairs are likely move faster. And from the code generation perspective using cmp+jcc is also more flexible. With cmov you have to tie up two registers. This is particularly bad with the x86 ABI. There are certainly cases where cmov can be faster. Perhaps exclusively on older micro architectures (P4s, early Core2, maybe AMD, haven't checked). But in general it's no win. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkmIooYACgkQ2ijCOnn/RHSaCwCgvpRT/7GJELdNu+5nSPKUqKHa wmgAnjxFmL278HkbwBCI5HK5YCT47JzC =xAK6 -----END PGP SIGNATURE----- -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
