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pan/va: weaken barrier requirements for allow_merging_workgroups

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The only requirement for barriers is that the hardware doesn't support
allow_merging_workgroups with actual BARRIER instructions. We only emit
these for workgroup execution barriers though, so are safe to merge
workgroups when the shader uses memory barriers or subgroup execution
barriers.

Signed-off-by: Olivia Lee <olivia.lee@collabora.com>
Reviewed-by: Caterina Shablia <caterina.shablia@collabora.com>
Reviewed-by: Lars-Ivar Hesselberg Simonsen <lars-ivar.simonsen@arm.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38586>
This commit is contained in:
Olivia Lee 2025-11-30 20:18:37 -08:00 • committed by Marge Bot
parent 46aac5abaf
commit 1f75299ebb
1 changed files with 33 additions and 10 deletions
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43
src/panfrost/compiler/bifrost/bifrost_nir.c
View file

@ -575,6 +575,37 @@ bi_lower_subgroups(nir_builder *b, nir_intrinsic_instr *intr, void *data)
return true;
}
/* Workgroups may be merged if the structure of the workgroup is not software
* visible. This is true if neither shared memory nor BARRIER instructions are
* used. The hardware may be able to optimize compute shaders that set this
* flag. */
static bool
bi_can_merge_workgroups(nir_shader *nir)
{
if (nir->info.shared_size != 0)
return false;
nir_foreach_function_impl(impl, nir) {
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
/* We only emit BARRIER instructions for workgroup execution
* barriers. For subgroup execution barriers, the only consequence
* of merging workgroups is that the scope may be larger, which is
* allowed. */
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic == nir_intrinsic_barrier &&
nir_intrinsic_execution_scope(intrin) == SCOPE_WORKGROUP)
return false;
}
}
}
return true;
}
static bool
bi_lower_load_output(nir_builder *b, nir_intrinsic_instr *intr,
UNUSED void *data)
@ -1121,16 +1152,8 @@ bifrost_compile_shader_nir(nir_shader *nir,
bi_compile_variant(nir, inputs, binary, info, BI_IDVS_NONE);
}
if (mesa_shader_stage_is_compute(nir->info.stage)) {
/* Workgroups may be merged if the structure of the workgroup is
* not software visible. This is true if neither shared memory
* nor barriers are used. The hardware may be able to optimize
* compute shaders that set this flag.
*/
info->cs.allow_merging_workgroups = (nir->info.shared_size == 0) &&
!nir->info.uses_control_barrier &&
!nir->info.uses_memory_barrier;
}
if (mesa_shader_stage_is_compute(nir->info.stage))
info->cs.allow_merging_workgroups = bi_can_merge_workgroups(nir);
info->ubo_mask &= (1 << nir->info.num_ubos) - 1;
}