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. > 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
