diff options
| author | Matt Turner <[email protected]> | 2016-02-01 16:44:18 -0800 |
|---|---|---|
| committer | Matt Turner <[email protected]> | 2016-02-08 21:20:58 -0800 |
| commit | 371c4b3c48f665d530bc0c95990ef47f0e4c1b87 (patch) | |
| tree | 366d584b112dd871af22698d6436e96a4d192348 | |
| parent | 2d0d9755da92f7153c1390728fa448b9978e9135 (diff) | |
nir: Recognize open-coded bitfield_reverse.
Helps 11 shaders in UnrealEngine4 demos.
I seriously hope they would have given us bitfieldReverse() if we
exposed GL 4.0 (but we do expose ARB_gpu_shader5, so why not use that
anyway?).
instructions in affected programs: 4875 -> 4633 (-4.96%)
cycles in affected programs: 270516 -> 244516 (-9.61%)
I suspect there's a *lot* of room to improve nir_search/opt_algebraic's
handling of this. We'd actually like to match, e.g., step2 by matching
step1 once and then doing a pointer comparison for the second instance
of step1, but unfortunately we generate an enormous tuple for instead.
The .text size increases by 6.5% and the .data by 17.5%.
text data bss dec hex filename
22957 45224 0 68181 10a55 nir_libnir_la-nir_opt_algebraic.o
24461 53160 0 77621 12f35 nir_libnir_la-nir_opt_algebraic.o
I'd be happy to remove this if Unreal4 uses bitfieldReverse() if it is
in a GL 4.0 context once we expose GL 4.0.
Reviewed-by: Jason Ekstrand <[email protected]>
| -rw-r--r-- | src/compiler/nir/nir_opt_algebraic.py | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py index 9b82bac6f6c..cc2c2299ab9 100644 --- a/src/compiler/nir/nir_opt_algebraic.py +++ b/src/compiler/nir/nir_opt_algebraic.py @@ -312,6 +312,19 @@ optimizations = [ 'options->lower_unpack_snorm_4x8'), ] +# Unreal Engine 4 demo applications open-codes bitfieldReverse() +def bitfield_reverse(u): + step1 = ('ior', ('ishl', u, 16), ('ushr', u, 16)) + step2 = ('ior', ('ishl', ('iand', step1, 0x00ff00ff), 8), ('ushr', ('iand', step1, 0xff00ff00), 8)) + step3 = ('ior', ('ishl', ('iand', step2, 0x0f0f0f0f), 4), ('ushr', ('iand', step2, 0xf0f0f0f0), 4)) + step4 = ('ior', ('ishl', ('iand', step3, 0x33333333), 2), ('ushr', ('iand', step3, 0xcccccccc), 2)) + step5 = ('ior', ('ishl', ('iand', step4, 0x55555555), 1), ('ushr', ('iand', step4, 0xaaaaaaaa), 1)) + + return step5 + +optimizations += [(bitfield_reverse('x'), ('bitfield_reverse', 'x'))] + + # Add optimizations to handle the case where the result of a ternary is # compared to a constant. This way we can take things like # |