* [PATCH] m68k: One function call less in cf_tlb_miss()
@ 2019-07-05 15:18 Markus Elfring
2019-07-05 23:56 ` Finn Thain
0 siblings, 1 reply; 6+ messages in thread
From: Markus Elfring @ 2019-07-05 15:18 UTC (permalink / raw)
To: linux-m68k, Andrew Morton, Geert Uytterhoeven, Greg Ungerer,
Michal Hocko, Mike Rapoport
Cc: LKML, kernel-janitors
From: Markus Elfring <elfring@users.sourceforge.net>
Date: Fri, 5 Jul 2019 17:11:37 +0200
Avoid an extra function call by using a ternary operator instead of
a conditional statement for a setting selection.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
arch/m68k/mm/mcfmmu.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
index 6cb1e41d58d0..02fc0778028e 100644
--- a/arch/m68k/mm/mcfmmu.c
+++ b/arch/m68k/mm/mcfmmu.c
@@ -146,12 +146,10 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);
-
- if (dtlb)
- mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
- else
- mmu_write(MMUOR, MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
-
+ mmu_write(MMUOR,
+ dtlb
+ ? MMUOR_ACC | MMUOR_UAA
+ : MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
local_irq_restore(flags);
return 0;
}
--
2.22.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] m68k: One function call less in cf_tlb_miss()
2019-07-05 15:18 [PATCH] m68k: One function call less in cf_tlb_miss() Markus Elfring
@ 2019-07-05 23:56 ` Finn Thain
2019-07-14 13:23 ` Geert Uytterhoeven
0 siblings, 1 reply; 6+ messages in thread
From: Finn Thain @ 2019-07-05 23:56 UTC (permalink / raw)
To: Markus Elfring
Cc: linux-m68k, Andrew Morton, Geert Uytterhoeven, Greg Ungerer,
Michal Hocko, Mike Rapoport, LKML, kernel-janitors
On Fri, 5 Jul 2019, Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Fri, 5 Jul 2019 17:11:37 +0200
>
> Avoid an extra function call
Not really. You've avoided an extra statement.
> by using a ternary operator instead of a conditional statement for a
> setting selection.
>
> This issue was detected by using the Coccinelle software.
>
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> arch/m68k/mm/mcfmmu.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
> index 6cb1e41d58d0..02fc0778028e 100644
> --- a/arch/m68k/mm/mcfmmu.c
> +++ b/arch/m68k/mm/mcfmmu.c
> @@ -146,12 +146,10 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
>
> mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
> ((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);
> -
> - if (dtlb)
> - mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
> - else
> - mmu_write(MMUOR, MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
> -
> + mmu_write(MMUOR,
> + dtlb
> + ? MMUOR_ACC | MMUOR_UAA
> + : MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
If you are trying to avoid redundancy, why not finish the job?
+ mmu_write(MMUOR, (dtlb ? 0 : MMUOR_ITLB) | MMUOR_ACC | MMUOR_UAA);
--
> local_irq_restore(flags);
> return 0;
> }
> --
> 2.22.0
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] m68k: One function call less in cf_tlb_miss()
2019-07-05 23:56 ` Finn Thain
@ 2019-07-14 13:23 ` Geert Uytterhoeven
2019-07-14 16:05 ` Markus Elfring
0 siblings, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2019-07-14 13:23 UTC (permalink / raw)
To: Markus Elfring
Cc: Finn Thain, Andrew Morton, Greg Ungerer, Michal Hocko,
Mike Rapoport, linux-m68k, LKML, kernel-janitors
Hi Markus,
On Sat, Jul 6, 2019 at 1:57 AM Finn Thain <fthain@telegraphics.com.au> wrote:
> On Fri, 5 Jul 2019, Markus Elfring wrote:
> > From: Markus Elfring <elfring@users.sourceforge.net>
> > Date: Fri, 5 Jul 2019 17:11:37 +0200
> >
> > Avoid an extra function call
> > by using a ternary operator instead of a conditional statement for a
> > setting selection.
Have you looked at the actual assembler output generated by the compiler?
> > This issue was detected by using the Coccinelle software.
> >
> > Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> > ---
> > arch/m68k/mm/mcfmmu.c | 10 ++++------
> > 1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
> > index 6cb1e41d58d0..02fc0778028e 100644
> > --- a/arch/m68k/mm/mcfmmu.c
> > +++ b/arch/m68k/mm/mcfmmu.c
> > @@ -146,12 +146,10 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
> >
> > mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
> > ((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);
> > -
> > - if (dtlb)
> > - mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
> > - else
> > - mmu_write(MMUOR, MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
> > -
> > + mmu_write(MMUOR,
> > + dtlb
> > + ? MMUOR_ACC | MMUOR_UAA
> > + : MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
While the ternary operator can be useful for short expressions, it can
also lead to hard-to-read code. IMHO the latter is the case here
(hint: the expression needs 3 lines).
> If you are trying to avoid redundancy, why not finish the job?
>
> + mmu_write(MMUOR, (dtlb ? 0 : MMUOR_ITLB) | MMUOR_ACC | MMUOR_UAA);
Thanks Finn, much better!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: m68k: One function call less in cf_tlb_miss()
2019-07-14 13:23 ` Geert Uytterhoeven
@ 2019-07-14 16:05 ` Markus Elfring
2019-07-14 21:14 ` Geert Uytterhoeven
0 siblings, 1 reply; 6+ messages in thread
From: Markus Elfring @ 2019-07-14 16:05 UTC (permalink / raw)
To: Geert Uytterhoeven, linux-m68k, kernel-janitors
Cc: Finn Thain, Andrew Morton, Greg Ungerer, Michal Hocko,
Mike Rapoport, LKML
>>> Avoid an extra function call by using a ternary operator
>>> instead of a conditional statement for a setting selection.
>
> Have you looked at the actual assembler output generated by the compiler?
Not yet.
* Can the suggested small refactoring matter for a specific software combination there?
* Would you like to clarify this change possibility a bit more?
Regards,
Markus
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: m68k: One function call less in cf_tlb_miss()
2019-07-14 16:05 ` Markus Elfring
@ 2019-07-14 21:14 ` Geert Uytterhoeven
2019-07-15 6:11 ` Markus Elfring
0 siblings, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2019-07-14 21:14 UTC (permalink / raw)
To: Markus Elfring
Cc: linux-m68k, kernel-janitors, Finn Thain, Andrew Morton,
Greg Ungerer, Michal Hocko, Mike Rapoport, LKML
Hi Markus,
On Sun, Jul 14, 2019 at 6:06 PM Markus Elfring <Markus.Elfring@web.de> wrote:
> >>> Avoid an extra function call by using a ternary operator
> >>> instead of a conditional statement for a setting selection.
> >
> > Have you looked at the actual assembler output generated by the compiler?
>
> Not yet.
You better do, it can be a good learning experience!
> * Can the suggested small refactoring matter for a specific software combination there?
> * Would you like to clarify this change possibility a bit more?
-EPARSE
No need to relay my emails through https://en.wikipedia.org/wiki/ELIZA ;-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: m68k: One function call less in cf_tlb_miss()
2019-07-14 21:14 ` Geert Uytterhoeven
@ 2019-07-15 6:11 ` Markus Elfring
0 siblings, 0 replies; 6+ messages in thread
From: Markus Elfring @ 2019-07-15 6:11 UTC (permalink / raw)
To: Geert Uytterhoeven, linux-m68k, kernel-janitors
Cc: Finn Thain, Andrew Morton, Greg Ungerer, Michal Hocko,
Mike Rapoport, LKML
> You better do,
It can eventually happen again under other circumstances.
> it can be a good learning experience!
This can be also possible.
>> * Can the suggested small refactoring matter for a specific software combination there?
>> * Would you like to clarify this change possibility a bit more?
>
> -EPARSE
I am curious where you got parsing (or more understanding) difficulties
for these questions.
Regards,
Markus
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-07-05 15:18 [PATCH] m68k: One function call less in cf_tlb_miss() Markus Elfring
2019-07-05 23:56 ` Finn Thain
2019-07-14 13:23 ` Geert Uytterhoeven
2019-07-14 16:05 ` Markus Elfring
2019-07-14 21:14 ` Geert Uytterhoeven
2019-07-15 6:11 ` Markus Elfring
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