drm/radeon/r600_cs: Build failures with GCC 16

drm/radeon/r600_cs: Build failures with GCC 16

[Brahmajit Das]

Hello Developers,

Building linux-next with GCC 16 results in this following build error

$ make
  CALL    scripts/checksyscalls.sh
  DESCEND objtool
  INSTALL libsubcmd_headers
  CC      drivers/gpu/drm/radeon/r600_cs.o
drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
 1411 |         unsigned offset, i, level;
      |                             ^~~~~
cc1: all warnings being treated as errors
make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1
make[5]: *** [scripts/Makefile.build:556: drivers/gpu/drm/radeon] Error 2
make[4]: *** [scripts/Makefile.build:556: drivers/gpu/drm] Error 2
make[3]: *** [scripts/Makefile.build:556: drivers/gpu] Error 2
make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
make[1]: *** [/home/listout/linux/Makefile:2011: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2

I'm not sure whether this is kernel bug or GCC bug at the moment. But
building with GCC 15 does not give this error, hence I'm more inclined
towards the latter.
Planning to also report this on GCC side, wanted to get some
opinion/feedback from kernel devs as well.
I'm on GCC 16.0.0_p2025080.

-- 
Regards,
listout

Re: drm/radeon/r600_cs: Build failures with GCC 16

[Brahmajit Das]

On 09.08.2025 04:45, Brahmajit Das wrote:
> Hello Developers,
> 
> Building linux-next with GCC 16 results in this following build error
> 
> $ make
>   CALL    scripts/checksyscalls.sh
>   DESCEND objtool
>   INSTALL libsubcmd_headers
>   CC      drivers/gpu/drm/radeon/r600_cs.o
> drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
> drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
>  1411 |         unsigned offset, i, level;
>       |                             ^~~~~
> cc1: all warnings being treated as errors
> make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1
> make[5]: *** [scripts/Makefile.build:556: drivers/gpu/drm/radeon] Error 2
> make[4]: *** [scripts/Makefile.build:556: drivers/gpu/drm] Error 2
> make[3]: *** [scripts/Makefile.build:556: drivers/gpu] Error 2
> make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
> make[1]: *** [/home/listout/linux/Makefile:2011: .] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
> 
> I'm not sure whether this is kernel bug or GCC bug at the moment. But
> building with GCC 15 does not give this error, hence I'm more inclined
> towards the latter.
> Planning to also report this on GCC side, wanted to get some
> opinion/feedback from kernel devs as well.
> I'm on GCC 16.0.0_p2025080.
> 
> -- 
> Regards,
> listout

After giving a more thorough look, the level usage seems like dead code?
It's just set (level = blevel) and incremented in the loop (level++). I
don't see any other usage of the level variable. So if we do something
like

diff --git a/drivers/gpu/drm/radeon/r600_cs.c b/drivers/gpu/drm/radeon/r600_cs.c
index ac77d1246b94..953ce0c57dfb 100644
--- a/drivers/gpu/drm/radeon/r600_cs.c
+++ b/drivers/gpu/drm/radeon/r600_cs.c
@@ -1408,7 +1408,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
 			      unsigned block_align, unsigned height_align, unsigned base_align,
 			      unsigned *l0_size, unsigned *mipmap_size)
 {
-	unsigned offset, i, level;
+	unsigned offset, i;
 	unsigned width, height, depth, size;
 	unsigned blocksize;
 	unsigned nbx, nby;
@@ -1420,7 +1420,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
 	w0 = r600_mip_minify(w0, 0);
 	h0 = r600_mip_minify(h0, 0);
 	d0 = r600_mip_minify(d0, 0);
-	for(i = 0, offset = 0, level = blevel; i < nlevels; i++, level++) {
+	for(i = 0, offset = 0; i < nlevels; i++) {
 		width = r600_mip_minify(w0, i);
 		nbx = r600_fmt_get_nblocksx(format, width);

I think it should be fine.

Would really appreciate some feedback.
(CC-ed Dave)

-- 
Regards,
listout

Re: drm/radeon/r600_cs: Build failures with GCC 16

[Christian König]

On 09.08.25 11:36, Brahmajit Das wrote:
> On 09.08.2025 04:45, Brahmajit Das wrote:
>> Hello Developers,
>>
>> Building linux-next with GCC 16 results in this following build error
>>
>> $ make
>>   CALL    scripts/checksyscalls.sh
>>   DESCEND objtool
>>   INSTALL libsubcmd_headers
>>   CC      drivers/gpu/drm/radeon/r600_cs.o
>> drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
>> drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
>>  1411 |         unsigned offset, i, level;
>>       |                             ^~~~~
>> cc1: all warnings being treated as errors
>> make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1
>> make[5]: *** [scripts/Makefile.build:556: drivers/gpu/drm/radeon] Error 2
>> make[4]: *** [scripts/Makefile.build:556: drivers/gpu/drm] Error 2
>> make[3]: *** [scripts/Makefile.build:556: drivers/gpu] Error 2
>> make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
>> make[1]: *** [/home/listout/linux/Makefile:2011: .] Error 2
>> make: *** [Makefile:248: __sub-make] Error 2
>>
>> I'm not sure whether this is kernel bug or GCC bug at the moment. But
>> building with GCC 15 does not give this error, hence I'm more inclined
>> towards the latter.
>> Planning to also report this on GCC side, wanted to get some
>> opinion/feedback from kernel devs as well.
>> I'm on GCC 16.0.0_p2025080.
>>
>> -- 
>> Regards,
>> listout
> 
> After giving a more thorough look, the level usage seems like dead code?
> It's just set (level = blevel) and incremented in the loop (level++). I
> don't see any other usage of the level variable. So if we do something
> like
> 
> diff --git a/drivers/gpu/drm/radeon/r600_cs.c b/drivers/gpu/drm/radeon/r600_cs.c
> index ac77d1246b94..953ce0c57dfb 100644
> --- a/drivers/gpu/drm/radeon/r600_cs.c
> +++ b/drivers/gpu/drm/radeon/r600_cs.c
> @@ -1408,7 +1408,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
>  			      unsigned block_align, unsigned height_align, unsigned base_align,
>  			      unsigned *l0_size, unsigned *mipmap_size)
>  {
> -	unsigned offset, i, level;
> +	unsigned offset, i;
>  	unsigned width, height, depth, size;
>  	unsigned blocksize;
>  	unsigned nbx, nby;
> @@ -1420,7 +1420,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
>  	w0 = r600_mip_minify(w0, 0);
>  	h0 = r600_mip_minify(h0, 0);
>  	d0 = r600_mip_minify(d0, 0);
> -	for(i = 0, offset = 0, level = blevel; i < nlevels; i++, level++) {
> +	for(i = 0, offset = 0; i < nlevels; i++) {
>  		width = r600_mip_minify(w0, i);
>  		nbx = r600_fmt_get_nblocksx(format, width);
> 
> I think it should be fine.

Looks valid to me. Potentially just copy&pasted from some older HW generation and not correctly adjusted for r600.

But the HW handled here is >15 years and the code easily >10 years old. I'm really wondering why gcc only complains now?

Regards,
Christian.

> 
> Would really appreciate some feedback.
> (CC-ed Dave)
> 

Re: drm/radeon/r600_cs: Build failures with GCC 16

[Brahmajit Das]

On 11.08.2025 10:48, Christian König wrote:
...snip...
> 
> Looks valid to me. Potentially just copy&pasted from some older HW generation and not correctly adjusted for r600.
> 
> But the HW handled here is >15 years and the code easily >10 years old. I'm really wondering why gcc only complains now?
> 
> Regards,
> Christian.
> 
> > 
> > Would really appreciate some feedback.
> > (CC-ed Dave)
> > 
> 
That option -Werror=unused-but-set-variable= is new in GCC 16, maybe
that's why it was never caught before?

Would you like me to send a patch?
-- 
Regards,
listout

[PATCH] drm/radeon/r600_cs: clean up of dead code in r600_cs

[Brahmajit Das]

GCC 16 enables -Werror=unused-but-set-variable= which results in build
error with the following message.

drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
 1411 |         unsigned offset, i, level;
      |                             ^~~~~
cc1: all warnings being treated as errors
make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1

level although is set, but in never used in the function
r600_texture_size. Thus resulting in dead code and this error getting
triggered.

Fixes: 60b212f8ddcdb ("drm/radeon: overhaul texture checking. (v3)")
Signed-off-by: Brahmajit Das <listout@listout.xyz>
---
 drivers/gpu/drm/radeon/r600_cs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/r600_cs.c b/drivers/gpu/drm/radeon/r600_cs.c
index ac77d1246b94..811265648a58 100644
--- a/drivers/gpu/drm/radeon/r600_cs.c
+++ b/drivers/gpu/drm/radeon/r600_cs.c
@@ -1408,7 +1408,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
 			      unsigned block_align, unsigned height_align, unsigned base_align,
 			      unsigned *l0_size, unsigned *mipmap_size)
 {
-	unsigned offset, i, level;
+	unsigned offset, i;
 	unsigned width, height, depth, size;
 	unsigned blocksize;
 	unsigned nbx, nby;
@@ -1420,7 +1420,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
 	w0 = r600_mip_minify(w0, 0);
 	h0 = r600_mip_minify(h0, 0);
 	d0 = r600_mip_minify(d0, 0);
-	for(i = 0, offset = 0, level = blevel; i < nlevels; i++, level++) {
+	for (i = 0, offset = 0; i < nlevels; i++) {
 		width = r600_mip_minify(w0, i);
 		nbx = r600_fmt_get_nblocksx(format, width);
 
-- 
2.50.1

Re: [PATCH] drm/radeon/r600_cs: clean up of dead code in r600_cs

[Christian König]

On 11.08.25 11:21, Brahmajit Das wrote:
> GCC 16 enables -Werror=unused-but-set-variable= which results in build
> error with the following message.
> 
> drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
> drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
>  1411 |         unsigned offset, i, level;
>       |                             ^~~~~
> cc1: all warnings being treated as errors
> make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1
> 
> level although is set, but in never used in the function
> r600_texture_size. Thus resulting in dead code and this error getting
> triggered.
> 
> Fixes: 60b212f8ddcdb ("drm/radeon: overhaul texture checking. (v3)")
> Signed-off-by: Brahmajit Das <listout@listout.xyz>

Acked-by: Christian König <christian.koenig@amd.com>

> ---
>  drivers/gpu/drm/radeon/r600_cs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/radeon/r600_cs.c b/drivers/gpu/drm/radeon/r600_cs.c
> index ac77d1246b94..811265648a58 100644
> --- a/drivers/gpu/drm/radeon/r600_cs.c
> +++ b/drivers/gpu/drm/radeon/r600_cs.c
> @@ -1408,7 +1408,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
>  			      unsigned block_align, unsigned height_align, unsigned base_align,
>  			      unsigned *l0_size, unsigned *mipmap_size)
>  {
> -	unsigned offset, i, level;
> +	unsigned offset, i;
>  	unsigned width, height, depth, size;
>  	unsigned blocksize;
>  	unsigned nbx, nby;
> @@ -1420,7 +1420,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
>  	w0 = r600_mip_minify(w0, 0);
>  	h0 = r600_mip_minify(h0, 0);
>  	d0 = r600_mip_minify(d0, 0);
> -	for(i = 0, offset = 0, level = blevel; i < nlevels; i++, level++) {
> +	for (i = 0, offset = 0; i < nlevels; i++) {
>  		width = r600_mip_minify(w0, i);
>  		nbx = r600_fmt_get_nblocksx(format, width);
>  

Re: [PATCH] drm/radeon/r600_cs: clean up of dead code in r600_cs

[Alex Deucher]

Applied.  Thanks!

Alex

On Mon, Aug 11, 2025 at 8:53 AM Christian König
<christian.koenig@amd.com> wrote:
>
> On 11.08.25 11:21, Brahmajit Das wrote:
> > GCC 16 enables -Werror=unused-but-set-variable= which results in build
> > error with the following message.
> >
> > drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_texture_size’:
> > drivers/gpu/drm/radeon/r600_cs.c:1411:29: error: variable ‘level’ set but not used [-Werror=unused-but-set-variable=]
> >  1411 |         unsigned offset, i, level;
> >       |                             ^~~~~
> > cc1: all warnings being treated as errors
> > make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/radeon/r600_cs.o] Error 1
> >
> > level although is set, but in never used in the function
> > r600_texture_size. Thus resulting in dead code and this error getting
> > triggered.
> >
> > Fixes: 60b212f8ddcdb ("drm/radeon: overhaul texture checking. (v3)")
> > Signed-off-by: Brahmajit Das <listout@listout.xyz>
>
> Acked-by: Christian König <christian.koenig@amd.com>
>
> > ---
> >  drivers/gpu/drm/radeon/r600_cs.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/radeon/r600_cs.c b/drivers/gpu/drm/radeon/r600_cs.c
> > index ac77d1246b94..811265648a58 100644
> > --- a/drivers/gpu/drm/radeon/r600_cs.c
> > +++ b/drivers/gpu/drm/radeon/r600_cs.c
> > @@ -1408,7 +1408,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
> >                             unsigned block_align, unsigned height_align, unsigned base_align,
> >                             unsigned *l0_size, unsigned *mipmap_size)
> >  {
> > -     unsigned offset, i, level;
> > +     unsigned offset, i;
> >       unsigned width, height, depth, size;
> >       unsigned blocksize;
> >       unsigned nbx, nby;
> > @@ -1420,7 +1420,7 @@ static void r600_texture_size(unsigned nfaces, unsigned blevel, unsigned llevel,
> >       w0 = r600_mip_minify(w0, 0);
> >       h0 = r600_mip_minify(h0, 0);
> >       d0 = r600_mip_minify(d0, 0);
> > -     for(i = 0, offset = 0, level = blevel; i < nlevels; i++, level++) {
> > +     for (i = 0, offset = 0; i < nlevels; i++) {
> >               width = r600_mip_minify(w0, i);
> >               nbx = r600_fmt_get_nblocksx(format, width);
> >
>