* [PATCH] x86: Micro-optimization in nhmex_rbox_get_constraint
@ 2014-06-19 13:15 Rasmus Villemoes
2014-06-23 8:55 ` Peter Zijlstra
2014-07-05 10:47 ` [tip:perf/core] perf/x86: Micro-optimize nhmex_rbox_get_constraint() tip-bot for Rasmus Villemoes
0 siblings, 2 replies; 3+ messages in thread
From: Rasmus Villemoes @ 2014-06-19 13:15 UTC (permalink / raw)
To: Peter Zijlstra, H. Peter Anvin, Ingo Molnar
Cc: x86, linux-kernel, Rasmus Villemoes
Flipping the LSB doesn't require four lines of code. This shaves a few
bytes of the generated code, including a branch.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 65bbbea..e009f3c 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -2946,10 +2946,7 @@ again:
* extra registers. If we failed to take an extra
* register, try the alternative.
*/
- if (idx % 2)
- idx--;
- else
- idx++;
+ idx ^= 1;
if (idx != reg1->idx % 6) {
if (idx == 2)
config1 >>= 8;
--
1.9.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] x86: Micro-optimization in nhmex_rbox_get_constraint
2014-06-19 13:15 [PATCH] x86: Micro-optimization in nhmex_rbox_get_constraint Rasmus Villemoes
@ 2014-06-23 8:55 ` Peter Zijlstra
2014-07-05 10:47 ` [tip:perf/core] perf/x86: Micro-optimize nhmex_rbox_get_constraint() tip-bot for Rasmus Villemoes
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2014-06-23 8:55 UTC (permalink / raw)
To: Rasmus Villemoes; +Cc: H. Peter Anvin, Ingo Molnar, x86, linux-kernel
On Thu, Jun 19, 2014 at 03:15:31PM +0200, Rasmus Villemoes wrote:
> Flipping the LSB doesn't require four lines of code. This shaves a few
> bytes of the generated code, including a branch.
>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip:perf/core] perf/x86: Micro-optimize nhmex_rbox_get_constraint()
2014-06-19 13:15 [PATCH] x86: Micro-optimization in nhmex_rbox_get_constraint Rasmus Villemoes
2014-06-23 8:55 ` Peter Zijlstra
@ 2014-07-05 10:47 ` tip-bot for Rasmus Villemoes
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Rasmus Villemoes @ 2014-07-05 10:47 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, linux, hpa, mingo, peterz, acme, tglx
Commit-ID: 2172c1f5aa58310784f358ca20fdddfcdc2a0d7b
Gitweb: http://git.kernel.org/tip/2172c1f5aa58310784f358ca20fdddfcdc2a0d7b
Author: Rasmus Villemoes <linux@rasmusvillemoes.dk>
AuthorDate: Thu, 19 Jun 2014 15:15:31 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 5 Jul 2014 11:21:52 +0200
perf/x86: Micro-optimize nhmex_rbox_get_constraint()
Flipping the LSB doesn't require four lines of code. This shaves a few
bytes of the generated code, including a branch.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403183731-15402-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 65bbbea..e009f3c 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -2946,10 +2946,7 @@ again:
* extra registers. If we failed to take an extra
* register, try the alternative.
*/
- if (idx % 2)
- idx--;
- else
- idx++;
+ idx ^= 1;
if (idx != reg1->idx % 6) {
if (idx == 2)
config1 >>= 8;
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-07-05 10:48 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-06-19 13:15 [PATCH] x86: Micro-optimization in nhmex_rbox_get_constraint Rasmus Villemoes
2014-06-23 8:55 ` Peter Zijlstra
2014-07-05 10:47 ` [tip:perf/core] perf/x86: Micro-optimize nhmex_rbox_get_constraint() tip-bot for Rasmus Villemoes
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox