Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1288604

Re: [PATCH] usb: remove redundant conditions

Show all headers | View raw

2015-12-10 12:29 GMT-03:00 Geyslan G. Bem <geyslan@gmail.com>:
> 2015-12-10 12:17 GMT-03:00 David Laight <David.Laight@aculab.com>:
>> From: Felipe Balbi
>>> Sent: 10 December 2015 15:14
>>> "Geyslan G. Bem" <geyslan@gmail.com> writes:
>>>
>>> > This patch removes redundant conditions.
>>> >
>>> >  - (!A || (A && B)) is the same as (!A || B).
>>> >  - (length && length > 5) can be reduced to a single evaluation.
>>> >
>>> > Caught by: cppcheck
>>> >
>>> > Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
>>> > ---
>>>
>>> I guess you didn't get previous comment in time; let's split this per
>>> driver so different maintainers can pick their parts.
>>
>> I also suspect that gcc will optimise out the redundant checks as well.
> Yes, David. it will.
>
> Let's see.
>
> void f(int f, int s)
> {
>         if (!f || (f && s))
>                 printf("branch\n");
> }
>
> Generates without optimization three comparisons:
>
>         cmpl    $0, -4(%rbp)
>         je      .L2
>         cmpl    $0, -4(%rbp)
>         je      .L4
>         cmpl    $0, -8(%rbp)
>         je      .L4
>
> But with -O2 it generates only two:
>
>         testl   %edi, %edi
>         je      .L2
>         testl   %esi, %esi
>         je      .L1
>
> Despite that, I think that the patches are welcome since they silence
> checkpatch and make code clearer. Don't you think?
Sorry, silence "cppcheck". I'm mistaking the tool name.
>
>>
>>         David
>>
>
>
>
> --
> Regards,
>
> Geyslan G. Bem
> hackingbits.com



-- 
Regards,

Geyslan G. Bem
hackingbits.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 03:00 +0100
  Re: [PATCH] usb: remove redundant conditions Johan Hovold <johan@kernel.org> - 2015-12-10 11:50 +0100
    Re: [PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 12:00 +0100
  Re: [PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 16:00 +0100
  Re: [PATCH] usb: remove redundant conditions Felipe Balbi <balbi@ti.com> - 2015-12-10 16:00 +0100
  Re: [PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 16:20 +0100
    Re: [PATCH] usb: remove redundant conditions Felipe Balbi <balbi@ti.com> - 2015-12-10 16:40 +0100
  RE: [PATCH] usb: remove redundant conditions David Laight <David.Laight@ACULAB.COM> - 2015-12-10 16:20 +0100
    Re: [PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 16:40 +0100
    Re: [PATCH] usb: remove redundant conditions "Geyslan G. Bem" <geyslan@gmail.com> - 2015-12-10 16:40 +0100
  Re: [PATCH] usb: remove redundant conditions Felipe Balbi <balbi@ti.com> - 2015-12-10 16:20 +0100

csiph-web