[Mesa-dev] [PATCH] glsl: Optimize certain if-statements to just casts from the condition

[Kenneth Graunke]

On Friday, January 16, 2015 04:54:44 PM Ian Romanick wrote:
> On 01/16/2015 04:25 PM, Matt Turner wrote:
> > On Thu, Jan 15, 2015 at 6:46 PM, Ian Romanick <idr at freedesktop.org> wrote:
> >> On 01/16/2015 08:15 AM, Matt Turner wrote:
> >>> From: Ian Romanick <ian.d.romanick at intel.com>
> >>>
> >>> Some shaders end up with code that looks something like:
> >>>
> >>>     if (some_condition)
> >>>         result = 1.0;
> >>>     else
> >>>         result = 0.0;
> >>>
> >>> This pass converts those if-statements to
> >>>
> >>>      result = float(some_condition);
> >>>
> >>> total instructions in shared programs: 5934568 -> 5921818 (-0.21%)
> >>> instructions in affected programs:     723433 -> 710683 (-1.76%)
> >>> GAINED:                                26
> >>> LOST:                                  7
> >>
> >> I was getting really different results here... on my more recent version
> >> (that should produce the same IR), I was getting basically the reverse
> >> lost / gained.  The other results were about the same.
> >>
> >> I updated both Mesa and shader-db, and I'm not able to do a full
> >> shader-db run now.  At semi-arbitrary points in the run I get
> >>
> >> Exception: Only shader 0 found.
> >> shaders/closed/unreal4/sun-temple/180.shader_test
> > 
> > You need commit f0aec4ee1e3 to avoid an assertion failure.
> > 
> >> If I run that shader_test by hand, I get multiple shader emitted.  I'm
> >> using the older run.py... is it possible that's broken?
> > 
> > It's been working for me in occasional usage to generate *.out files.
> 
> Trivial. :p
> 
> diff --git a/run.py b/run.py
> index 4fc366e..d57da21 100755
> --- a/run.py
> +++ b/run.py
> @@ -57,7 +57,7 @@ def run_test(filename):
>          raise Exception('Only shader 0 found. {}'.format(filename))
>  
>      re_search = re.compile(
> -        r'(?P<stage>[A-Za-z0-9]+) shader\: (?P<count>\d+) instructions.')
> +        r'(?P<stage>[A-Za-z0-9 ]+) shader\: (?P<count>\d+) instructions.')
>      for line in lines:
>          match = re_search.match(line)
>          if match is not None:

FYI, I broke report.py support with run.py the other day.  You want to use
Matt's new C-based multithreaded runner, which takes literally 1/3 of the
time of the old Python script.

$ make
$ ./run shaders | tee results/foobarquux

or for even faster runs:
$ LD_PRELOAD=/usr/lib64/libjemalloc.so.1 INTEL_NO_HW=1 ./run shaders

--Ken
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