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intel/fs: Don't optimize out 1.0*x and -1.0*x

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This (sort of) matches the behavior of nir_opt_algebraic.  This ensures
that subnormal values are properly flushed to zero.

With the aid of "nir/search: Float sources of texture instructions are
float users" and "nir/search: Transitively apply is_only_used_as_float",
there would have been no shader-db regressions on Intel platforms.
However, those caused a significant increase in compile time.  Since the
instruction regressions were so small, I just dropped those commits
rather than improve them.

All Haswell and newer platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 20125042 -> 20125094 (<.01%)
instructions in affected programs: 7184 -> 7236 (0.72%)
helped: 0
HURT: 32
HURT stats (abs)   min: 1 max: 4 x̄: 1.62 x̃: 2
HURT stats (rel)   min: 0.11% max: 1.49% x̄: 0.85% x̃: 0.78%
95% mean confidence interval for instructions value: 1.39 1.86
95% mean confidence interval for instructions %-change: 0.74% 0.96%
Instructions are HURT.

total cycles in shared programs: 862745586 -> 862746551 (<.01%)
cycles in affected programs: 109872 -> 110837 (0.88%)
helped: 12
HURT: 23
helped stats (abs) min: 2 max: 774 x̄: 90.83 x̃: 19
helped stats (rel) min: 0.07% max: 25.23% x̄: 3.06% x̃: 0.40%
HURT stats (abs)   min: 2 max: 1106 x̄: 89.35 x̃: 12
HURT stats (rel)   min: 0.08% max: 45.40% x̄: 3.01% x̃: 0.47%
95% mean confidence interval for cycles value: -60.09 115.23
95% mean confidence interval for cycles %-change: -2.21% 4.07%
Inconclusive result (value mean confidence interval includes 0).

All of the shaders hurt are in either UE4 shooter-game or shooter_demo.

Tiger Lake
Instructions in all programs: 159893213 -> 159893290 (+0.0%)
SENDs in all programs: 6936431 -> 6936431 (+0.0%)
Loops in all programs: 38385 -> 38385 (+0.0%)
Cycles in all programs: 7019259514 -> 7019260087 (+0.0%)
Spills in all programs: 101389 -> 101389 (+0.0%)
Fills in all programs: 131532 -> 131532 (+0.0%)

Ice Lake
Instructions in all programs: 143624164 -> 143624235 (+0.0%)
SENDs in all programs: 6980289 -> 6980289 (+0.0%)
Loops in all programs: 38383 -> 38383 (+0.0%)
Cycles in all programs: 8440082767 -> 8440083238 (+0.0%)
Spills in all programs: 102246 -> 102246 (+0.0%)
Fills in all programs: 131908 -> 131908 (+0.0%)

Skylake
Instructions in all programs: 134185424 -> 134185495 (+0.0%)
SENDs in all programs: 6938790 -> 6938790 (+0.0%)
Loops in all programs: 38356 -> 38356 (+0.0%)
Cycles in all programs: 8222366529 -> 8222366923 (+0.0%)
Spills in all programs: 98821 -> 98821 (+0.0%)
Fills in all programs: 125218 -> 125218 (+0.0%)

Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Fixes: f5dd6dfe01 ("anv: enable VK_KHR_shader_float_controls and SPV_KHR_float_controls")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13999>
(cherry picked from commit 38a94c82e6)
This commit is contained in:
Ian Romanick 2021-10-29 14:16:44 -07:00 • committed by Dylan Baker
parent cc1511acd7
commit 8d42870798
2 changed files with 4 additions and 1 deletions
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2
.pick_status.json
View file

@ -121,7 +121,7 @@
"description": "intel/fs: Don't optimize out 1.0*x and -1.0*x",
"nominated": true,
"nomination_type": 1,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": "f5dd6dfe012666123bb59b9a4f8e9afb46d67414"
},

3
src/intel/compiler/brw_fs.cpp
View file

@ -2572,6 +2572,9 @@ fs_visitor::opt_algebraic()
if (inst->src[1].file != IMM)
continue;
if (brw_reg_type_is_floating_point(inst->src[1].type))
break;
/* a * 1.0 = a */
if (inst->src[1].is_one()) {
inst->opcode = BRW_OPCODE_MOV;