2015-12-10 12:17 GMT-03:00 David Laight <David.Laight@xxxxxxxxxx>:
> From: Felipe Balbi
>> Sent: 10 December 2015 15:14
>> "Geyslan G. Bem" <geyslan@xxxxxxxxx> 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@xxxxxxxxx>
>> > ---
>>
>> 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?
>
> David
>
--
Regards,
Geyslan G. Bem
hackingbits.com
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