[Mesa-dev] [PATCH] radeonsi: enable 32-bit denormals on VI+

[Ilia Mirkin]

So, I don't know whether this affects more than compute shaders
without reading the code, but I explicitly had to enable denorm
flushing on nvc0 in order to fix some sad artifacts in Unigine Heaven.

Right now nouveau only does denorm flushes on graphics shaders, but
the reason I did that originally was to leave them on for a
hypothetical OpenCL compute situation (and GL compute was far from my
radar at the time). IMHO GL compute shaders probably want denorm
flushing as well.

Cheers,

  -ilia

On Wed, Jan 11, 2017 at 1:09 PM, Marek Olšák <maraeo at gmail.com> wrote:
> Reviewed-by: Marek Olšák <marek.olsak at amd.com>
>
> Would you please run a GPU-bound benchmark of your choice to make sure
> it doesn't affect performance?
>
> Thanks,
> Marek
>
> On Wed, Jan 11, 2017 at 6:29 PM, Samuel Pitoiset
> <samuel.pitoiset at gmail.com> wrote:
>> Only VI can do 32-bit denormals at full rate while previous
>> generations can do it only for 64-bit and 16-bit.
>>
>> This fixes some dEQP tests with the highp type qualifier.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99343
>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>> ---
>>  src/gallium/drivers/radeonsi/si_shader.c | 11 ++++++++---
>>  1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
>> index 5dfbd6603a..e9cb11883f 100644
>> --- a/src/gallium/drivers/radeonsi/si_shader.c
>> +++ b/src/gallium/drivers/radeonsi/si_shader.c
>> @@ -6361,8 +6361,10 @@ int si_compile_llvm(struct si_screen *sscreen,
>>
>>         si_shader_binary_read_config(binary, conf, 0);
>>
>> -       /* Enable 64-bit and 16-bit denormals, because there is no performance
>> -        * cost.
>> +       /* Enable denormals when there is no performance cost.
>> +        *
>> +        * Only VI can do 32-bit denormals at full rate while previous
>> +        * generations can do it only for 64-bit and 16-bit.
>>          *
>>          * If denormals are enabled, all floating-point output modifiers are
>>          * ignored.
>> @@ -6373,7 +6375,10 @@ int si_compile_llvm(struct si_screen *sscreen,
>>          *   have to stop using those.
>>          * - SI & CI would be very slow.
>>          */
>> -       conf->float_mode |= V_00B028_FP_64_DENORMS;
>> +       if (sscreen->b.chip_class >= VI)
>> +               conf->float_mode |= V_00B028_FP_ALL_DENORMS;
>> +       else
>> +               conf->float_mode |= V_00B028_FP_64_DENORMS;
>>
>>         FREE(binary->config);
>>         FREE(binary->global_symbol_offsets);
>> --
>> 2.11.0
>>
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