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nir: add flt comparision simplification

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Didn't turn out as useful as I'd hoped, but it will help alot more on
i965 by reducing regressions when we drop brw_do_channel_expressions()
and brw_do_vector_splitting().

I'm not sure how much sense 'is_not_used_by_conditional' makes on
platforms other than i965 but since this is a new opt it at least
won't do any harm.

shader-db BDW:

total instructions in shared programs: 13029581 -> 13029415 (-0.00%)
instructions in affected programs: 15268 -> 15102 (-1.09%)
helped: 86
HURT: 0

total cycles in shared programs: 247038346 -> 247036198 (-0.00%)
cycles in affected programs: 692634 -> 690486 (-0.31%)
helped: 183
HURT: 27

Reviewed-by: Elie Tournier <elie.tournier@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Timothy Arceri 2017-01-12 17:01:03 +11:00 • committed by Timothy Arceri
parent 18947fde7a
commit 83f7fdf83a
2 changed files with 19 additions and 0 deletions
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4
src/compiler/nir/nir_opt_algebraic.py
View file

@ -158,6 +158,10 @@ optimizations = [
# a != 0.0
(('flt', 0.0, ('fabs', a)), ('fne', a, 0.0)),
# ignore this opt when the result is used by a bcsel or if so we can make
# use of conditional modifiers on supported hardware.
(('flt(is_not_used_by_conditional)', ('fadd(is_used_once)', a, ('fneg', b)), 0.0), ('flt', a, b)),
(('fge', ('fneg', ('fabs', a)), 0.0), ('feq', a, 0.0)),
(('bcsel', ('flt', b, a), b, a), ('fmin', a, b)),
(('bcsel', ('flt', a, b), b, a), ('fmax', a, b)),

15
src/compiler/nir/nir_search_helpers.h
View file

@ -158,4 +158,19 @@ is_not_used_by_if(nir_alu_instr *instr)
return list_empty(&instr->dest.dest.ssa.if_uses);
}
static inline bool
is_not_used_by_conditional(nir_alu_instr *instr)
{
if (!is_not_used_by_if(instr))
return false;
nir_foreach_use(use, &instr->dest.dest.ssa) {
if (use->parent_instr->type == nir_instr_type_alu &&
nir_instr_as_alu(use->parent_instr)->op == nir_op_bcsel)
return false;
}
return true;
}
#endif /* _NIR_SEARCH_ */