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nir: Optimize uniform iadd, fadd, and ixor reduction operations

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This adds optimizations for iadd, fadd, and ixor with reduce,
inclusive scan, and exclusive scan.

NOTE: The fadd and ixor optimizations had no shader-db or fossil-db
changes on any Intel platform.

NOTE 2: This change "fixes" arb_compute_variable_group_size-local-size
and base-local-size.shader_test on DG2 and MTL. This is just changing
the code path taken to not use whatever path was not working properly
before.

This is a subset of the things optimized by ACO. See also
https://gitlab.freedesktop.org/mesa/mesa/-/issues/3731#note_682802. The
min, max, iand, and ior exclusive_scan optimizations are not
implemented.

Broadwell on shader-db is not happy. I have not investigated.

v2: Silence some warnings about discarding const.

v3: Rename mbcnt to count_active_invocations. Add a big comment
explaining the differences between the two paths. Suggested by Rhys.

shader-db:

All Gfx9 and newer platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 20300384 -> 20299545 (<.01%)
instructions in affected programs: 19167 -> 18328 (-4.38%)
helped: 35 / HURT: 0

total cycles in shared programs: 842809750 -> 842766381 (<.01%)
cycles in affected programs: 2160249 -> 2116880 (-2.01%)
helped: 33 / HURT: 2

total spills in shared programs: 4632 -> 4626 (-0.13%)
spills in affected programs: 206 -> 200 (-2.91%)
helped: 3 / HURT: 0

total fills in shared programs: 5594 -> 5581 (-0.23%)
fills in affected programs: 664 -> 651 (-1.96%)
helped: 3 / HURT: 1

fossil-db results:

All Intel platforms had similar results. (Ice Lake shown)
Totals:
Instrs: 165551893 -> 165513303 (-0.02%)
Cycles: 15132539132 -> 15125314947 (-0.05%); split: -0.05%, +0.00%
Spill count: 45258 -> 45204 (-0.12%)
Fill count: 74286 -> 74157 (-0.17%)
Scratch Memory Size: 2467840 -> 2451456 (-0.66%)

Totals from 712 (0.11% of 656120) affected shaders:
Instrs: 598931 -> 560341 (-6.44%)
Cycles: 184650167 -> 177425982 (-3.91%); split: -3.95%, +0.04%
Spill count: 983 -> 929 (-5.49%)
Fill count: 2274 -> 2145 (-5.67%)
Scratch Memory Size: 52224 -> 35840 (-31.37%)

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27044>
This commit is contained in:
Ian Romanick
2023-12-19 18:40:41 -08:00
parent c63ea755fe
commit 535caaf3e0
3 changed files with 98 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/intel/compiler/brw_nir.c
+14 -11
View File
@@ -1699,12 +1699,14 @@ brw_postprocess_nir(nir_shader *nir, const struct brw_compiler *compiler,
NIR_PASS(_, nir, nir_convert_to_lcssa, true, true);
NIR_PASS_V(nir, nir_divergence_analysis);
static const nir_lower_subgroups_options subgroups_options = {
.ballot_bit_size = 32,
.ballot_components = 1,
.lower_elect = true,
.lower_subgroup_masks = true,
};
if (OPT(nir_opt_uniform_atomics)) {
const nir_lower_subgroups_options subgroups_options = {
.ballot_bit_size = 32,
.ballot_components = 1,
.lower_elect = true,
};
OPT(nir_lower_subgroups, &subgroups_options);
if (OPT(nir_lower_int64))
@@ -1716,12 +1718,13 @@ brw_postprocess_nir(nir_shader *nir, const struct brw_compiler *compiler,
/* nir_opt_uniform_subgroup can create some operations (e.g.,
* load_subgroup_lt_mask) that need to be lowered again.
*/
if (OPT(nir_opt_uniform_subgroup)) {
const nir_lower_subgroups_options subgroups_options = {
.ballot_bit_size = 32,
.ballot_components = 1,
.lower_subgroup_masks = true,
};
if (OPT(nir_opt_uniform_subgroup, &subgroups_options)) {
/* Some of the optimizations can generate 64-bit integer multiplication
* that must be lowered.
*/
if (OPT(nir_lower_int64))
brw_nir_optimize(nir, is_scalar, devinfo);
OPT(nir_lower_subgroups, &subgroups_options);
}