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

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Date:   Mon, 10 Oct 2022 09:14:02 +0100
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        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>,
        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'


On 08/10/2022 12:55, Christophe JAILLET wrote:
> 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.

AFAICS result is used, just the copy/local variable is not.

For the patch:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>

Thanks for the cleanup, will merge.

Regards,

Tvrtko


> 
> 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;
>