[Mesa-dev] [PATCH v2] glsls: Modify exec_list to avoid strict-aliasing violations
davmac at davmac.org
Thu Jun 25 05:53:24 PDT 2015
On 25/06/15 12:27, Eero Tamminen wrote:
> On 06/25/2015 02:48 AM, Davin McCall wrote:
>> In terms of performance:
>> (export LIBGL_ALWAYS_SOFTWARE=1; time glmark2)
> For Intel driver, INTEL_NO_HW=1 could be used.
> (Do other drivers have something similar?)
Unfortunately I do not have an Intel display set up. What exactly would
>> Again, only a very small improvement when strict aliasing is enabled.
>> With the above in mind it is reasonable to question whether this patch
>> is worthwhile.
> IMHO to evaluate that, we would need data for more drivers, not just
> for SW rendering.
Given that we are talking about using a compiler option when compiling
Mesa itself, I do not imagine that we would see a more significant
change in performance when using HW assisted rendering. The code that
runs on the GPU is the same in either case.
Using the R600 driver (and Radeon 6770 hardware) I get:
glmark2 Score: 1614
With strict aliasing:
glmark2 Score: 1626
This is all on x86, 32-bit. It's possible that more of an improvement
would be seen on less register-starved architectures (including Intel
x86-64), since more register spills/loads can potentially be avoided. I
don't have the capability to test that right now. It's entirely possible
that compiling without -fno-strict-aliasing on x86-64 will not (at
present, even with this patch applied) produce a working library.
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