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nir: Recognize a pattern of bool frobbing from TGSI KILL_IF. 

TGSI's conditional discards take float arg and negate it, so GLSL to TGSI
generates a b2f and negates that value.  Only, in NIR we want a proper
bool once again, so we compare with 0.  This is a lot of pointless extra
instructions.

total instructions in shared programs: 39735 -> 39702 (-0.08%)
instructions in affected programs:     1342 -> 1309 (-2.46%)

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
This commit is contained in:
Eric Anholt 2015-03-29 23:04:21 -07:00
parent 6e8d4a2f80
commit 15b03b7964
1 changed files with 2 additions and 0 deletions
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2
src/glsl/nir/nir_opt_algebraic.py
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@ -100,6 +100,8 @@ optimizations = [
(('fmul', ('b2f', a), ('b2f', b)), ('b2f', ('iand', a, b))),
(('fsat', ('fadd', ('b2f', a), ('b2f', b))), ('b2f', ('ior', a, b))),
(('iand', 'a@bool', 1.0), ('b2f', a)),
(('flt', ('fneg', ('b2f', a)), 0), a), # Generated by TGSI KILL_IF.
(('flt', ('fsub', 0.0, ('b2f', a)), 0), a), # Generated by TGSI KILL_IF.
# Comparison with the same args. Note that these are not done for
# the float versions because NaN always returns false on float
# inequalities.