[tip:perf/core] perf/x86: Micro-optimize nhmex_rbox_get_constraint()
From: tip-bot for Rasmus Villemoes
Date: Sat Jul 05 2014 - 06:48:10 EST
Commit-ID: 2172c1f5aa58310784f358ca20fdddfcdc2a0d7b
Gitweb: http://git.kernel.org/tip/2172c1f5aa58310784f358ca20fdddfcdc2a0d7b
Author: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 19 Jun 2014 15:15:31 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1403183731-15402-1-git-send-email-linux@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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;
--
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