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nir/algebraic: Clean up value range analysis-based optimizations

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Fix the a / b ordering in some compares.  Delete duplicate patterns.
Add a table explaining things.  While I was cleaning this up, I managed
to confuse myself.  The table helped sort that out.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
This commit is contained in:
Ian Romanick 2019-08-08 16:48:14 -07:00
parent ccb236d1bc
commit e07248d2a8
1 changed files with 18 additions and 8 deletions
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26
src/compiler/nir/nir_opt_algebraic.py
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@ -838,31 +838,41 @@ optimizations.extend([
(('fne', 'a(is_not_zero)', 0.0), True),
(('feq', 'a(is_not_zero)', 0.0), False),
# In this chart, + means value > 0 and - means value < 0.
#
# + >= + -> unknown 0 >= + -> false - >= + -> false
# + >= 0 -> true 0 >= 0 -> true - >= 0 -> false
# + >= - -> true 0 >= - -> true - >= - -> unknown
#
# Using grouping conceptually similar to a Karnaugh map...
#
# (+ >= 0, + >= -, 0 >= 0, 0 >= -) == (is_not_negative >= is_not_positive) -> true
# (0 >= +, - >= +) == (is_not_positive >= gt_zero) -> false
# (- >= +, - >= 0) == (lt_zero >= is_not_negative) -> false
#
# The flt / ilt cases just invert the expected result.
#
# The results expecting true, must be marked imprecise. The results
# expecting false are fine because NaN compared >= or < anything is false.
(('~fge', 'a(is_not_negative)', 'b(is_not_positive)'), True),
(('fge', 'b(is_not_positive)', 'a(is_gt_zero)'), False),
(('fge', 'a(is_not_positive)', 'b(is_gt_zero)'), False),
(('fge', 'a(is_lt_zero)', 'b(is_not_negative)'), False),
(('~fge', 'b(is_not_negative)', 'a(is_not_positive)'), True),
(('flt', 'a(is_not_negative)', 'b(is_not_positive)'), False),
(('~flt', 'b(is_not_positive)', 'a(is_gt_zero)'), True),
(('~flt', 'a(is_not_positive)', 'b(is_gt_zero)'), True),
(('~flt', 'a(is_lt_zero)', 'b(is_not_negative)'), True),
(('flt', 'b(is_not_negative)', 'a(is_not_positive)'), False),
(('ine', 'a(is_not_zero)', 0), True),
(('ieq', 'a(is_not_zero)', 0), False),
(('ige', 'a(is_not_negative)', 'b(is_not_positive)'), True),
(('ige', 'b(is_not_positive)', 'a(is_gt_zero)'), False),
(('ige', 'a(is_not_positive)', 'b(is_gt_zero)'), False),
(('ige', 'a(is_lt_zero)', 'b(is_not_negative)'), False),
(('ige', 'b(is_not_negative)', 'a(is_not_positive)'), True),
(('ilt', 'a(is_not_negative)', 'b(is_not_positive)'), False),
(('ilt', 'b(is_not_positive)', 'a(is_gt_zero)'), True),
(('ilt', 'a(is_not_positive)', 'b(is_gt_zero)'), True),
(('ilt', 'a(is_lt_zero)', 'b(is_not_negative)'), True),
(('ilt', 'b(is_not_negative)', 'a(is_not_positive)'), False),
(('ult', 0, 'a(is_gt_zero)'), True),