* [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code
@ 2014-06-01 21:43 Rickard Strandqvist
2014-06-02 7:24 ` Clemens Ladisch
0 siblings, 1 reply; 3+ messages in thread
From: Rickard Strandqvist @ 2014-06-01 21:43 UTC (permalink / raw)
To: Tony Luck, Fenghua Yu
Cc: Rickard Strandqvist, Paul Gortmaker, Rafael J. Wysocki,
Srivatsa S. Bhat, linux-ia64, linux-kernel
>From what I know, AND is faster then modulo.
Not sure if this is worth changing though.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
---
arch/ia64/kernel/palinfo.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index c39c3cd..7915b02 100644
--- a/arch/ia64/kernel/palinfo.c
+++ b/arch/ia64/kernel/palinfo.c
@@ -156,7 +156,8 @@ static void bitregister_process(struct seq_file *m, u64 *reg_info, int max)
for(; i < max; i++ ) {
- if (i != 0 && (i%64) == 0) value = *++reg_info;
+ if (i != 0 && (i&63) == 0)
+ value = *++reg_info;
if ((value & 0x1) == 0 && skip == 0) {
if (begin <= i - 2)
--
1.7.10.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code
2014-06-01 21:43 [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code Rickard Strandqvist
@ 2014-06-02 7:24 ` Clemens Ladisch
2014-06-02 17:59 ` Rickard Strandqvist
0 siblings, 1 reply; 3+ messages in thread
From: Clemens Ladisch @ 2014-06-02 7:24 UTC (permalink / raw)
To: Rickard Strandqvist, Tony Luck, Fenghua Yu
Cc: Paul Gortmaker, Rafael J. Wysocki, Srivatsa S. Bhat, linux-ia64,
linux-kernel
Rickard Strandqvist wrote:
> From what I know, AND is faster then modulo.
Which is why the compiler does this optimization automatically,
if it can prove that it is correct.
> - if (i != 0 && (i%64) == 0)
> + if (i != 0 && (i&63) == 0)
Did you prove that i cannot be negative?
Regards,
Clemens
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code
2014-06-02 7:24 ` Clemens Ladisch
@ 2014-06-02 17:59 ` Rickard Strandqvist
0 siblings, 0 replies; 3+ messages in thread
From: Rickard Strandqvist @ 2014-06-02 17:59 UTC (permalink / raw)
To: Clemens Ladisch
Cc: Tony Luck, Fenghua Yu, Paul Gortmaker, Rafael J. Wysocki,
Srivatsa S. Bhat, linux-ia64, linux-kernel@vger.kernel.org
Hi
Thought I would be able to do that. But after testing, I could not
measure any difference.
Thought it would make a noticeable difference, but guess gcc resolve
this in the best way.
Best regards
Rickard Strandqvist
2014-06-02 9:24 GMT+02:00 Clemens Ladisch <clemens@ladisch.de>:
> Rickard Strandqvist wrote:
>> From what I know, AND is faster then modulo.
>
> Which is why the compiler does this optimization automatically,
> if it can prove that it is correct.
>
>> - if (i != 0 && (i%64) == 0)
>> + if (i != 0 && (i&63) == 0)
>
> Did you prove that i cannot be negative?
>
>
> Regards,
> Clemens
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-06-01 21:43 [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code Rickard Strandqvist
2014-06-02 7:24 ` Clemens Ladisch
2014-06-02 17:59 ` Rickard Strandqvist
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