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| author | Jan Beulich <JBeulich@suse.com> | 2012-09-10 15:24:43 +0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2012-09-13 19:44:01 +0400 |
| commit | 5870661c091e827973674cc3469b50c959008c2b (patch) | |
| tree | 4043f28631c98fbc03babd7b8b32af788f6f362e /mm/percpu.c | |
| parent | 1edfbb4153bd29bcf8d2236676238d5237972be1 (diff) | |
| download | linux-5870661c091e827973674cc3469b50c959008c2b.tar.xz | |
x86: Prefer TZCNT over BFS
Following a relatively recent compiler change, make use of the
fact that for non-zero input BSF and TZCNT produce the same
result, and that CPUs not knowing of TZCNT will treat the
instruction as BSF (i.e. ignore what looks like a REP prefix to
them). The assumption here is that TZCNT would never have worse
performance than BSF.
For the moment, only do this when the respective generic-CPU
option is selected (as there are no specific-CPU options
covering the CPUs supporting TZCNT), and don't do that when size
optimization was requested.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/504DEA1B020000780009A277@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm/percpu.c')
0 files changed, 0 insertions, 0 deletions