diff options
| author | Ian Romanick <[email protected]> | 2018-10-24 20:13:45 -0700 |
|---|---|---|
| committer | Ian Romanick <[email protected]> | 2019-05-14 11:38:22 -0700 |
| commit | 3cb091f8b4e071c4eed3b2e2ff57c7657f532498 (patch) | |
| tree | eaae34af3bb4347c6e236cb334931e8db35517a3 | |
| parent | 9725e45b3d06d7e226471e0c0eb8da0b0d54f448 (diff) | |
nir/algebraic: Eliminate a tautological compare
The value-range tracking pass that is coming is not clever enough to
know that the result of the ffma must be non-negative. Making it that
smart will require quite a bit of work. It might be possible to add a
special case that detects that a whole tree of fadd(fmul(fsat(a),
fneg(fsat(a))), 1.0) cannot be negative.
For cases when the comparison is used in the domain guard for a
square-root (see nir/algebraic: Simplify fsqrt domain guard), the
compare may be converted to a fmax. This patch also handles that case.
All of the affected cases are in DiRT: Showdown.
All Gen7+ platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 17225365 -> 17225303 (<.01%)
instructions in affected programs: 40051 -> 39989 (-0.15%)
helped: 62
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.07% max: 0.66% x̄: 0.27% x̃: 0.26%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -0.31% -0.22%
Instructions are helped.
total cycles in shared programs: 360842788 -> 360842595 (<.01%)
cycles in affected programs: 1818081 -> 1817888 (-0.01%)
helped: 29
HURT: 22
helped stats (abs) min: 1 max: 206 x̄: 20.66 x̃: 14
helped stats (rel) min: <.01% max: 9.55% x̄: 0.87% x̃: 0.42%
HURT stats (abs) min: 1 max: 108 x̄: 18.45 x̃: 7
HURT stats (rel) min: <.01% max: 4.48% x̄: 0.56% x̃: 0.19%
95% mean confidence interval for cycles value: -14.48 6.91
95% mean confidence interval for cycles %-change: -0.71% 0.21%
Inconclusive result (value mean confidence interval includes 0).
No changes on any other Intel platform.
Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Thomas Helland <[email protected]>
| -rw-r--r-- | src/compiler/nir/nir_opt_algebraic.py | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py index 15ac3bd32ca..b95d544d555 100644 --- a/src/compiler/nir/nir_opt_algebraic.py +++ b/src/compiler/nir/nir_opt_algebraic.py @@ -652,6 +652,13 @@ optimizations = [ (('~fmin', ('fabs', a), 1.0), ('fsat', ('fabs', a)), '!options->lower_fsat'), + # The result of the multiply must be in [-1, 0], so the result of the ffma + # must be in [0, 1]. + (('flt', ('fadd', ('fmul', ('fsat', a), ('fneg', ('fsat', a))), 1.0), 0.0), False), + (('flt', ('fadd', ('fneg', ('fmul', ('fsat', a), ('fsat', a))), 1.0), 0.0), False), + (('fmax', ('fadd', ('fmul', ('fsat', a), ('fneg', ('fsat', a))), 1.0), 0.0), ('fadd', ('fmul', ('fsat', a), ('fneg', ('fsat', a))), 1.0)), + (('fmax', ('fadd', ('fneg', ('fmul', ('fsat', a), ('fsat', a))), 1.0), 0.0), ('fadd', ('fneg', ('fmul', ('fsat', a), ('fsat', a))), 1.0)), + # Packing and then unpacking does nothing (('unpack_64_2x32_split_x', ('pack_64_2x32_split', a, b)), a), (('unpack_64_2x32_split_y', ('pack_64_2x32_split', a, b)), b), |