linux-kernel - Re: [PATCH] ALSA: synth: emux: remove redundant test for r <= 13

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Date:   Fri, 17 Nov 2017 11:07:47 +0000
From:   Colin Ian King <colin.king@...onical.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: synth: emux: remove redundant test for r <= 13

On 17/11/17 11:06, Takashi Iwai wrote:
> On Tue, 14 Nov 2017 18:26:53 +0100,
> Colin King wrote:
>>
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The calculation r = (3 - ((rate >> 6) & 3)) * 3 results in r being
>> 0, 3, 6 or 9 and so the check (13 > r) is always true and hence we
>> can remove the redundant check and the else path.
>>
>> Detected by CoverityScan, CID#744415 ("Logically dead code")
>>
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> 
> The calculation of t itself can be generic in case we may add a
> support greater than the current r, so I don't think it's so much
> beneficial with this code reduction.  Better to keep the code as
> reference.

OK, that's a good decision.

Colin
> 
> 
> thanks,
> 
> Takashi
> 
>> ---
>>  sound/synth/emux/soundfont.c | 5 +----
>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/sound/synth/emux/soundfont.c b/sound/synth/emux/soundfont.c
>> index 31a4ea94830e..0beb5a737c8b 100644
>> --- a/sound/synth/emux/soundfont.c
>> +++ b/sound/synth/emux/soundfont.c
>> @@ -858,10 +858,7 @@ calc_gus_envelope_time(int rate, int start, int end)
>>  	p = rate & 0x3f;
>>  	t = end - start;
>>  	if (t < 0) t = -t;
>> -	if (13 > r)
>> -		t = t << (13 - r);
>> -	else
>> -		t = t >> (r - 13);
>> +	t = t << (13 - r);
>>  	return (t * 10) / (p * 441);
>>  }
>>  
>> -- 
>> 2.14.1
>>
>>
> --
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