On Aug 11, 2016 6:16 PM, "Ian Romanick" <<a href="mailto:idr@freedesktop.org">idr@freedesktop.org</a>> wrote: > > On 08/11/2016 11:54 AM, Thomas Helland wrote: > > 2016-08-11 18:19 GMT+02:00 Ian Romanick <<a href="mailto:idr@freedesktop.org">idr@freedesktop.org</a>>: > >> ping > >> > >> On 07/19/2016 10:37 PM, Ian Romanick wrote: > >>> From: Ian Romanick <<a href="mailto:ian.d.romanick@intel.com">ian.d.romanick@intel.com</a>> > >>> > >>> Some shaders include code that looks like: > >>> > >>> uniform int i; > >>> uniform vec4 bones[...]; > >>> > >>> foo(bones[i * 3], bones[i * 3 + 1], bones[i * 3 + 2]); > >>> > >>> CSE would do some work on this: > >>> > >>> x = i * 3 > >>> foo(bones[x], bones[x + 1], bones[x + 2]); > >>> > >>> The compiler may then add '<< 4 + base' to the index calculations. > >>> This results in expressions like > >>> > >>> x = i * 3 > >>> foo(bones[x << 4], bones[(x + 1) << 4], bones[(x + 2) << 4]); > >>> > > > > This may just be me being dense, but why is the compiler adding the shift? > > It seems like this would be "un-optimizing" and so it shouldn't be added? > > The shift is to convert the array offset to a byte offset. A vec4 is 16 > bytes. > > > This patch is also a good argument for adding a constant reassociation pass. > > At least the (a * #b) << #c ---> a * (#b << #c) would be caught by that. > > > > I was confused whether the optimization was preserving signed-ness correctly > > but after a couple rounds with myself I believe it is correct. I believe so too. "<< c" as an operator is equivalent to "* (1 << c)" so association and distributivity apply. > > The change looks good and is: > > > > Reviewed-by: Thomas Helland <<a href="mailto:thomashelland90@gmail.com">thomashelland90@gmail.com</a>> Reviewed-by: Jason Ekstrand <<a href="mailto:jason@jlekstrand.net">jason@jlekstrand.net</a>> > > (Oh, and yes, I'm back to hobby mesa development after finally > > securing a new job and a new apartment) > > Welcome back! Woohoo! > >>> Just rearranging the math to produce (i * 48) + 16 saves an > >>> instruction, and it allows CSE to do more work. > >>> > >>> x = i * 48; > >>> foo(bones[x], bones[x + 16], bones[x + 32]); > >>> > >>> So, ~6 instructions becomes ~3. > >>> > >>> Some individual shader-db results look pretty bad. However, I have a > >>> really, really hard time believing the change in estimated cycles in, > >>> for example, 3dmmes-taiji/51.shader_test after looking that change in > >>> the generated code. > >>> > >>> G45 > >>> total instructions in shared programs: 4020840 -> 4010070 (-0.27%) > >>> instructions in affected programs: 177460 -> 166690 (-6.07%) > >>> helped: 894 > >>> HURT: 0 > >>> > >>> total cycles in shared programs: 98829000 -> 98784990 (-0.04%) > >>> cycles in affected programs: 3936648 -> 3892638 (-1.12%) > >>> helped: 894 > >>> HURT: 0 > >>> > >>> Ironlake > >>> total instructions in shared programs: 6418887 -> 6408117 (-0.17%) > >>> instructions in affected programs: 177460 -> 166690 (-6.07%) > >>> helped: 894 > >>> HURT: 0 > >>> > >>> total cycles in shared programs: 143504542 -> 143460532 (-0.03%) > >>> cycles in affected programs: 3936648 -> 3892638 (-1.12%) > >>> helped: 894 > >>> HURT: 0 > >>> > >>> Sandy Bridge > >>> total instructions in shared programs: 8357887 -> 8339251 (-0.22%) > >>> instructions in affected programs: 432715 -> 414079 (-4.31%) > >>> helped: 2795 > >>> HURT: 0 > >>> > >>> total cycles in shared programs: 118284184 -> 118207412 (-0.06%) > >>> cycles in affected programs: 6114626 -> 6037854 (-1.26%) > >>> helped: 2478 > >>> HURT: 317 > >>> > >>> Ivy Bridge > >>> total instructions in shared programs: 7669390 -> 7653822 (-0.20%) > >>> instructions in affected programs: 388234 -> 372666 (-4.01%) > >>> helped: 2795 > >>> HURT: 0 > >>> > >>> total cycles in shared programs: 68381982 -> 68263684 (-0.17%) > >>> cycles in affected programs: 1972658 -> 1854360 (-6.00%) > >>> helped: 2458 > >>> HURT: 307 > >>> > >>> Haswell > >>> total instructions in shared programs: 7082636 -> 7067068 (-0.22%) > >>> instructions in affected programs: 388234 -> 372666 (-4.01%) > >>> helped: 2795 > >>> HURT: 0 > >>> > >>> total cycles in shared programs: 68282020 -> 68164158 (-0.17%) > >>> cycles in affected programs: 1891820 -> 1773958 (-6.23%) > >>> helped: 2459 > >>> HURT: 261 > >>> > >>> Broadwell > >>> total instructions in shared programs: 9002466 -> 8985875 (-0.18%) > >>> instructions in affected programs: 658784 -> 642193 (-2.52%) > >>> helped: 2795 > >>> HURT: 5 > >>> > >>> total cycles in shared programs: 78503092 -> 78450404 (-0.07%) > >>> cycles in affected programs: 2873304 -> 2820616 (-1.83%) > >>> helped: 2275 > >>> HURT: 415 > >>> > >>> Skylake > >>> total instructions in shared programs: 9156978 -> 9140387 (-0.18%) > >>> instructions in affected programs: 682625 -> 666034 (-2.43%) > >>> helped: 2795 > >>> HURT: 5 > >>> > >>> total cycles in shared programs: 75591392 -> 75550574 (-0.05%) > >>> cycles in affected programs: 3192120 -> 3151302 (-1.28%) > >>> helped: 2271 > >>> HURT: 425 > >>> > >>> Signed-off-by: Ian Romanick <<a href="mailto:ian.d.romanick@intel.com">ian.d.romanick@intel.com</a>> > >>> --- > >>> src/compiler/nir/nir_opt_algebraic.py | 11 +++++++++++ > >>> 1 file changed, 11 insertions(+) > >>> > >>> diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py > >>> index 0f0896b..37cb700 100644 > >>> --- a/src/compiler/nir/nir_opt_algebraic.py > >>> +++ b/src/compiler/nir/nir_opt_algebraic.py > >>> @@ -119,6 +119,17 @@ optimizations = [ > >>> (('~fadd@64', a, ('fmul', c , ('fadd', b, ('fneg', a)))), ('flrp', a, b, c), '!options->lower_flrp64'), > >>> (('ffma', a, b, c), ('fadd', ('fmul', a, b), c), 'options->lower_ffma'), > >>> (('~fadd', ('fmul', a, b), c), ('ffma', a, b, c), 'options->fuse_ffma'), > >>> + > >>> + # (a * #b + #c) << #d > >>> + # ((a * #b) << #d) + (#c << #d) > >>> + # (a * (#b << #d)) + (#c << #d) > >>> + (('ishl', ('iadd', ('imul', a, '#b'), '#c'), '#d'), > >>> + ('iadd', ('imul', a, ('ishl', b, d)), ('ishl', c, d))), > >>> + > >>> + # (a * #b) << #c > >>> + # a * (#b << #c) > >>> + (('ishl', ('imul', a, '#b'), '#c'), ('imul', a, ('ishl', b, c))), > >>> + > >>> # Comparison simplifications > >>> (('~inot', ('flt', a, b)), ('fge', a, b)), > >>> (('~inot', ('fge', a, b)), ('flt', a, b)), > >>> > >> > >> _______________________________________________ > >> mesa-dev mailing list > >> <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> > >> <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> > > > > _______________________________________________ > mesa-dev mailing list > <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> > <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a>