nir: Distribute binary operations with constants into bcsel

This was specifically designed to simplify 1+mix(0, a-1, condition) to
mix(1, a, condition) by pushing the 1+ inside.

Skylake, Broadwell, and Haswell had similar results.  Skylake shown.
total instructions in shared programs: 14521753 -> 14521716 (<.01%)
instructions in affected programs: 10619 -> 10582 (-0.35%)
helped: 51
HURT: 14
helped stats (abs) min: 1 max: 12 x̄: 1.43 x̃: 1
helped stats (rel) min: 0.20% max: 3.58% x̄: 1.01% x̃: 0.95%
HURT stats (abs)   min: 1 max: 11 x̄: 2.57 x̃: 1
HURT stats (rel)   min: 0.22% max: 1.75% x̄: 1.20% x̃: 1.32%
95% mean confidence interval for instructions value: -1.31 0.17
95% mean confidence interval for instructions %-change: -0.80% -0.27%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 533000205 -> 533003533 (<.01%)
cycles in affected programs: 110610 -> 113938 (3.01%)
helped: 43
HURT: 28
helped stats (abs) min: 6 max: 440 x̄: 27.12 x̃: 16
helped stats (rel) min: 0.39% max: 4.84% x̄: 1.60% x̃: 1.67%
HURT stats (abs)   min: 2 max: 3066 x̄: 160.50 x̃: 14
HURT stats (rel)   min: 0.08% max: 77.78% x̄: 5.16% x̃: 0.62%
95% mean confidence interval for cycles value: -43.81 137.56
95% mean confidence interval for cycles %-change: -1.47% 3.60%
Inconclusive result (value mean confidence interval includes 0).

Ivy Bridge
total instructions in shared programs: 10018840 -> 10018713 (<.01%)
instructions in affected programs: 9431 -> 9304 (-1.35%)
helped: 51
HURT: 3
helped stats (abs) min: 1 max: 80 x̄: 2.76 x̃: 1
helped stats (rel) min: 0.20% max: 16.43% x̄: 1.16% x̃: 0.81%
HURT stats (abs)   min: 1 max: 12 x̄: 4.67 x̃: 1
HURT stats (rel)   min: 0.22% max: 1.33% x̄: 0.59% x̃: 0.22%
95% mean confidence interval for instructions value: -5.36 0.66
95% mean confidence interval for instructions %-change: -1.66% -0.46%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 87571944 -> 87572785 (<.01%)
cycles in affected programs: 117234 -> 118075 (0.72%)
helped: 42
HURT: 23
helped stats (abs) min: 2 max: 114 x̄: 51.90 x̃: 30
helped stats (rel) min: 0.11% max: 11.01% x̄: 4.45% x̃: 2.74%
HURT stats (abs)   min: 1 max: 2341 x̄: 131.35 x̃: 10
HURT stats (rel)   min: 0.06% max: 37.11% x̄: 2.75% x̃: 0.61%
95% mean confidence interval for cycles value: -61.05 86.93
95% mean confidence interval for cycles %-change: -3.47% -0.33%
Inconclusive result (value mean confidence interval includes 0).

Sandy Bridge
total instructions in shared programs: 10542933 -> 10542844 (<.01%)
instructions in affected programs: 11487 -> 11398 (-0.77%)
helped: 52
HURT: 3
helped stats (abs) min: 1 max: 40 x̄: 1.96 x̃: 1
helped stats (rel) min: 0.08% max: 8.16% x̄: 0.90% x̃: 0.72%
HURT stats (abs)   min: 1 max: 11 x̄: 4.33 x̃: 1
HURT stats (rel)   min: 0.22% max: 1.22% x̄: 0.55% x̃: 0.22%
95% mean confidence interval for instructions value: -3.17 -0.07
95% mean confidence interval for instructions %-change: -1.13% -0.52%
Instructions are helped.

total cycles in shared programs: 146098397 -> 146097094 (<.01%)
cycles in affected programs: 128140 -> 126837 (-1.02%)
helped: 47
HURT: 8
helped stats (abs) min: 2 max: 333 x̄: 29.21 x̃: 18
helped stats (rel) min: 0.13% max: 5.04% x̄: 1.18% x̃: 0.95%
HURT stats (abs)   min: 1 max: 16 x̄: 8.75 x̃: 9
HURT stats (rel)   min: 0.08% max: 0.43% x̄: 0.30% x̃: 0.34%
95% mean confidence interval for cycles value: -37.49 -9.90
95% mean confidence interval for cycles %-change: -1.22% -0.71%
Cycles are helped.

Iron Lake
total instructions in shared programs: 7886711 -> 7886509 (<.01%)
instructions in affected programs: 10425 -> 10223 (-1.94%)
helped: 50
HURT: 2
helped stats (abs) min: 1 max: 78 x̄: 4.08 x̃: 1
helped stats (rel) min: 0.34% max: 15.38% x̄: 1.12% x̃: 0.54%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.86% max: 0.91% x̄: 0.89% x̃: 0.89%
95% mean confidence interval for instructions value: -8.05 0.28
95% mean confidence interval for instructions %-change: -1.83% -0.26%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 178115324 -> 178114612 (<.01%)
cycles in affected programs: 765726 -> 765014 (-0.09%)
helped: 39
HURT: 1
helped stats (abs) min: 2 max: 276 x̄: 18.31 x̃: 8
helped stats (rel) min: <.01% max: 8.47% x̄: 0.39% x̃: 0.04%
HURT stats (abs)   min: 2 max: 2 x̄: 2.00 x̃: 2
HURT stats (rel)   min: 0.03% max: 0.03% x̄: 0.03% x̃: 0.03%
95% mean confidence interval for cycles value: -32.07 -3.53
95% mean confidence interval for cycles %-change: -0.86% 0.10%
Inconclusive result (%-change mean confidence interval includes 0).

GM45
total instructions in shared programs: 4857762 -> 4857661 (<.01%)
instructions in affected programs: 5523 -> 5422 (-1.83%)
helped: 25
HURT: 1
helped stats (abs) min: 1 max: 78 x̄: 4.08 x̃: 1
helped stats (rel) min: 0.34% max: 13.61% x̄: 1.04% x̃: 0.52%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.86% max: 0.86% x̄: 0.86% x̃: 0.86%
95% mean confidence interval for instructions value: -9.99 2.22
95% mean confidence interval for instructions %-change: -2.01% 0.08%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 122179674 -> 122179194 (<.01%)
cycles in affected programs: 530162 -> 529682 (-0.09%)
helped: 22
HURT: 1
helped stats (abs) min: 2 max: 292 x̄: 21.91 x̃: 7
helped stats (rel) min: <.01% max: 8.65% x̄: 0.44% x̃: 0.04%
HURT stats (abs)   min: 2 max: 2 x̄: 2.00 x̃: 2
HURT stats (rel)   min: 0.03% max: 0.03% x̄: 0.03% x̃: 0.03%
95% mean confidence interval for cycles value: -46.56 4.82
95% mean confidence interval for cycles %-change: -1.20% 0.36%
Inconclusive result (value mean confidence interval includes 0).

Signed-off-by: Ian Romanick <[email protected]>
Reviewed-by: Samuel Iglesias Gonsálvez <[email protected]>
Reviewed-by: Elie Tournier <[email protected]>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 3cc910a8a60..6dc19d9b121 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -604,6 +604,21 @@ for op in ['flt', 'fge', 'feq', 'fne',
        ('bcsel', 'a', (op, 'd', 'b'), (op, 'd', 'c'))),
    ]
 
+
+# For example, this converts things like
+#
+#    1 + mix(0, a - 1, condition)
+#
+# into
+#
+#    mix(1, (a-1)+1, condition)
+#
+# Other optimizations will rearrange the constants.
+for op in ['fadd', 'fmul', 'iadd', 'imul']:
+   optimizations += [
+      ((op, ('bcsel(is_used_once)', a, '#b', c), '#d'), ('bcsel', a, (op, b, d), (op, c, d)))
+   ]
+
 # This section contains "late" optimizations that should be run before
 # creating ffmas and calling regular optimizations for the final time.
 # Optimizations should go here if they help code generation and conflict