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

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Date:   Fri, 17 Nov 2017 12:06:36 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Colin King" <colin.king@...onical.com>
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 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.


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
> 
>