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nir/algebraic: Mark comparisons generated from lowered fsign precise

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This prevents other transformations from converting them to 'a != 0'.
For example, both of these transformations can do this:

   (('~flt', 0.0, ('fabs', a)), ('fne', a, 0.0)),
   (('~flt', ('fneg', ('fabs', a)), 0.0), ('fne', a, 0.0)),

Both fsign(fabs(NaN)) and fsign(fneg(fabs(NaN))) should produce zero,
but, since 'NaN != 0.0' is true, cascading these transformations could
cause them to generate 1.0 or -1.0 respecively.

No shader-db or fossil-db changes on any Intel platform.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6358>
This commit is contained in:
Ian Romanick
2020-02-19 12:47:21 -08:00
committed by Marge Bot
parent 9771af5dde
commit ec16f935fe
1 changed files with 6 additions and 3 deletions
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9
src/compiler/nir/nir_opt_algebraic.py
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@@ -572,8 +572,9 @@ optimizations.extend([
# SignedZeroInfNanPreserve is set, but we don't currently have any way of
# representing this in the optimizations other than the usual ~.
(('~fmax', ('fmin', a, 0.0), -1.0), ('fneg', ('fsat', ('fneg', a))), '!options->lower_fsat'),
# fsat(fsign(NaN)) = fsat(0) = 0, and b2f(0 < NaN) = b2f(False) = 0.
(('fsat', ('fsign', a)), ('b2f', ('flt', 0.0, a))),
# fsat(fsign(NaN)) = fsat(0) = 0, and b2f(0 < NaN) = b2f(False) = 0. Mark
# the new comparison precise to prevent it being changed to 'a != 0'.
(('fsat', ('fsign', a)), ('b2f', ('!flt', 0.0, a))),
(('fsat', ('b2f', a)), ('b2f', a)),
(('fsat', a), ('fmin', ('fmax', a, 0.0), 1.0), 'options->lower_fsat'),
(('fsat', ('fsat', a)), ('fsat', a)),
@@ -1576,7 +1577,9 @@ optimizations.extend([
(('imin', ('imax', a, -1), 1), ('isign', a), '!options->lower_isign'),
(('imax', ('imin', a, 1), -1), ('isign', a), '!options->lower_isign'),
# float(0 < NaN) - float(NaN < 0) = float(False) - float(False) = 0 - 0 = 0
(('fsign', a), ('fsub', ('b2f', ('flt', 0.0, a)), ('b2f', ('flt', a, 0.0))), 'options->lower_fsign'),
# Mark the new comparisons precise to prevent them being changed to 'a !=
# 0' or 'a == 0'.
(('fsign', a), ('fsub', ('b2f', ('!flt', 0.0, a)), ('b2f', ('!flt', a, 0.0))), 'options->lower_fsign'),
# Address/offset calculations:
# Drivers supporting imul24 should use the nir_lower_amul() pass, this