[Bug 99221] >2% perf drop in GfxBench T-Rex with "i965: disable loop unrolling in GLSL IR"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99221

--- Comment #10 from Matt Turner <mattst88 at gmail.com> ---
(In reply to Eero Tamminen from comment #9)
> 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;
> ------------------------
> ?

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.

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