On 03/10/2016 01:24 PM, Patrick Baggett wrote: > On Thu, Mar 10, 2016 at 3:08 PM, Patrick Baggett > <baggett.patr...@gmail.com> wrote: >> On Thu, Mar 10, 2016 at 12:25 PM, Ian Romanick <i...@freedesktop.org> wrote: >>> From: Ian Romanick <ian.d.roman...@intel.com> >>> >>> Sandy Bridge / Ivy Bridge / Haswell >>> total instructions in shared programs: 8462180 -> 8462174 (-0.00%) >>> instructions in affected programs: 564 -> 558 (-1.06%) >>> helped: 6 >>> HURT: 0 >>> >>> total cycles in shared programs: 117542462 -> 117542276 (-0.00%) >>> cycles in affected programs: 9768 -> 9582 (-1.90%) >>> helped: 12 >>> HURT: 0 >>> >>> Broadwell / Skylake >>> total instructions in shared programs: 8980833 -> 8980826 (-0.00%) >>> instructions in affected programs: 626 -> 619 (-1.12%) >>> helped: 7 >>> HURT: 0 >>> >>> total cycles in shared programs: 70077900 -> 70077714 (-0.00%) >>> cycles in affected programs: 9378 -> 9192 (-1.98%) >>> helped: 12 >>> HURT: 0 >>> >>> G45 and Ironlake showed no change. >>> >>> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com> >>> --- >>> src/compiler/nir/nir_opt_algebraic.py | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/src/compiler/nir/nir_opt_algebraic.py >>> b/src/compiler/nir/nir_opt_algebraic.py >>> index 4db8f84..1442ce8 100644 >>> --- a/src/compiler/nir/nir_opt_algebraic.py >>> +++ b/src/compiler/nir/nir_opt_algebraic.py >>> @@ -108,6 +108,11 @@ optimizations = [ >>> # inot(a) >>> (('fge', 0.0, ('b2f', a)), ('inot', a)), >>> >>> + # 0.0 < fabs(a) >>> + # 0.0 != fabs(a) because fabs(a) must be >= 0 >> I think this is wrong. Because >= 0.0 can mean that fabs(a) == 0.0 for >> some a, you can't say then fabs(a) != 0.0. >> >> Then, the counter-example is when a = 0.0 >> >> 1) 0.0 != fabs(0.0) >> 2) 0.0 != 0.0 >> > Rather, I mean the comment is wrong, but the conclusion that: > 0 < fabs(a) <-> a != 0.0 > is correct. You can just build a truth table or just observe that when > a == 0, 0 < 0 is false, and > when a != 0.0, fabs(a) will be > 0, so 0 < fabs(a) will be always true.
How about if I change it to # 0.0 != fabs(a) Since fabs(a) >= 0, 0 <= fabs(a) must be true I think it's trivial to see how to get from "0 < fabs(a)" to "0 != fabs(a)" based on that. >>> + # 0.0 != a >>> + (('flt', 0.0, ('fabs', a)), ('fne', a, 0.0)), >>> + >>> (('fge', ('fneg', ('fabs', a)), 0.0), ('feq', a, 0.0)), >>> (('bcsel', ('flt', a, b), a, b), ('fmin', a, b)), >>> (('bcsel', ('flt', a, b), b, a), ('fmax', a, b)), >>> -- >>> 2.5.0 >>> >>> _______________________________________________ >>> mesa-dev mailing list >>> mesa-dev@lists.freedesktop.org >>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev