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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - >2% perf drop in GfxBench T-Rex with "i965: disable loop unrolling in GLSL IR""
href="https://bugs.freedesktop.org/show_bug.cgi?id=99221#c11">Comment # 11</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - >2% perf drop in GfxBench T-Rex with "i965: disable loop unrolling in GLSL IR""
href="https://bugs.freedesktop.org/show_bug.cgi?id=99221">bug 99221</a>
from <span class="vcard"><a class="email" href="mailto:eero.t.tamminen@intel.com" title="Eero Tamminen <eero.t.tamminen@intel.com>"> <span class="fn">Eero Tamminen</span></a>
</span></b>
<pre>(In reply to Matt Turner from <a href="show_bug.cgi?id=99221#c10">comment #10</a>)
<span class="quote">> (In reply to Eero Tamminen from <a href="show_bug.cgi?id=99221#c9">comment #9</a>)
> > SynMark PSPhong case seems similar (worse scheduling and more register bank
> > conflicts).
> >
> > In the SynMark PSPom case, fragment shader has two loops of which GLSL IR
> > can unroll the other, but NIR doesn't unroll either of them.
> >
> > Should NIR be able to unroll loops with non-integer loop counter, like GLSL
> > IR did:
> > ------------------------
> > for (float i = 0.02; i < 0.9; i += 0.11)
> > maxSh += (texture(normalTex, texCoord + lightRay * i).a - sh0) * (1.0 -
> > i) * shadowSoftening;
> > ------------------------
> > ?</span >
Few other things that in shader-db had non-integer loop counters with fixed
counts:
- Invisible Inc
- Talos Principle
- Steam Big Picture
- Serious Sam 3
Manhattan, Unigine demos (at Ultra level), Nexuiz and Xonotic had float loops
without fixed count.
<span class="quote">> This is going to get really confusing really quickly is we're trying to
> debug 5 different regressions in the same bug. I recommend filing new bugs
> for each on that we're analyzing and making them block a TRACKER bug.</span >
While there are 4 benchmarks that are known to be regressed, so far it's one
issue, and potential issue with float counter loops.
Does/should NIR support unrolling non-integer loop counters?</pre>
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