On 09/30/2014 02:16 PM, Matt Turner wrote: > On Tue, Sep 30, 2014 at 2:10 PM, Ian Romanick <i...@freedesktop.org> wrote: >> On 09/27/2014 12:12 PM, Matt Turner wrote: >>> The next patch adds an algebraic optimization for the pattern >>> >>> sqrt a, b >>> rcp c, a >>> >>> and turns it into >>> >>> sqrt a, b >>> rsq c, b >>> >>> but many vertex shaders do >>> >>> a = sqrt(b); >>> var1 /= a; >>> var2 /= a; >>> >>> which generates >>> >>> sqrt a, b >>> rcp c, a >>> rcp d, a >>> >>> If we apply the algebraic optimization before CSE, we'll end up with >>> >>> sqrt a, b >>> rsq c, b >>> rcp d, a >> >> Why doesn't a second pass through opt_algebraic turn this into > > Because the addition in patch #2 just recognizes a consecutive sqrt+rcp > pattern.
That makes sense. Series is Reviewed-by: Ian Romanick <ian.d.roman...@intel.com> >> rsq c, b >> rsq d, b >> >> Seems like this could cause us to miss other optimization opportunities... > > This seems pretty sufficient for the collection of shaders in > shader-db -- no regressions, cuts vec4 instructions, and handles 410 > sqrt+rcp pairs. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
