linux-kernel - Re: [PATCH] drm/i915/perf: remove redundant variable 'taken'

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Date:   Sat, 8 Oct 2022 13:55:24 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Colin Ian King <colin.i.king@...il.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915/perf: remove redundant variable 'taken'

Le 07/10/2022 à 21:53, Colin Ian King a écrit :
> The assignment to variable taken is redundant and so it can be
> removed as well as the variable too.
> 
> Cleans up clang-scan build warnings:
> warning: Although the value stored to 'taken' is used in the enclosing
> expression, the value is never actually read from 'taken'
> [deadcode.DeadStores]

Hi,

#define OA_TAKEN(tail, head)	((tail - head) & (OA_BUFFER_SIZE - 1))

So if the result is not used, maybe calling OA_TAKEN() can be removed as 
well?
It looks like a no-op in such a case.

CJ

> 
> Signed-off-by: Colin Ian King <colin.i.king@...il.com>
> ---
>   drivers/gpu/drm/i915/i915_perf.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 0defbb43ceea..15816df916c7 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -656,7 +656,6 @@ static int gen8_append_oa_reports(struct i915_perf_stream *stream,
>   	size_t start_offset = *offset;
>   	unsigned long flags;
>   	u32 head, tail;
> -	u32 taken;
>   	int ret = 0;
>   
>   	if (drm_WARN_ON(&uncore->i915->drm, !stream->enabled))
> @@ -692,7 +691,7 @@ static int gen8_append_oa_reports(struct i915_perf_stream *stream,
>   
>   
>   	for (/* none */;
> -	     (taken = OA_TAKEN(tail, head));
> +	     OA_TAKEN(tail, head);
>   	     head = (head + report_size) & mask) {
>   		u8 *report = oa_buf_base + head;
>   		u32 *report32 = (void *)report;
> @@ -950,7 +949,6 @@ static int gen7_append_oa_reports(struct i915_perf_stream *stream,
>   	size_t start_offset = *offset;
>   	unsigned long flags;
>   	u32 head, tail;
> -	u32 taken;
>   	int ret = 0;
>   
>   	if (drm_WARN_ON(&uncore->i915->drm, !stream->enabled))
> @@ -984,7 +982,7 @@ static int gen7_append_oa_reports(struct i915_perf_stream *stream,
>   
>   
>   	for (/* none */;
> -	     (taken = OA_TAKEN(tail, head));
> +	     OA_TAKEN(tail, head);
>   	     head = (head + report_size) & mask) {
>   		u8 *report = oa_buf_base + head;
>   		u32 *report32 = (void *)report;