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intel/fs: bound subgroup invocation read to dispatch size

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This is to avoid out of bound register accesses (potentially leading
to hangs) when the dispatch size is smaller than when is reported in
the NIR subgroup_size.

v2: Implement bounding with a mask (since workgroup sizes are powers of 2) (Faith)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 530de844ef ("intel,anv,iris,crocus: Drop subgroup size from the shader key")
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21282>
(cherry picked from commit 9ac192d79d)
This commit is contained in:
Lionel Landwerlin 2023-02-08 20:48:25 +02:00 • committed by Dylan Baker
parent 14c0675135
commit 25e614486e
2 changed files with 14 additions and 2 deletions
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2
.pick_status.json
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@ -670,7 +670,7 @@
"description": "intel/fs: bound subgroup invocation read to dispatch size",
"nominated": true,
"nomination_type": 1,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": "530de844ef4d6f8d64276ad4558dd8a3d787e390"
},

14
src/intel/compiler/brw_fs_nir.cpp
View file

@ -5428,10 +5428,22 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
case nir_intrinsic_read_invocation: {
const fs_reg value = get_nir_src(instr->src[0]);
const fs_reg invocation = get_nir_src(instr->src[1]);
fs_reg tmp = bld.vgrf(value.type);
/* When for some reason the subgroup_size picked by NIR is larger than
* the dispatch size picked by the backend (this could happen in RT,
* FS), bound the invocation to the dispatch size.
*/
fs_reg bound_invocation;
if (bld.dispatch_width() < bld.shader->nir->info.subgroup_size) {
bound_invocation = bld.vgrf(BRW_REGISTER_TYPE_UD);
bld.AND(bound_invocation, invocation, brw_imm_ud(dispatch_width - 1));
} else {
bound_invocation = invocation;
}
bld.exec_all().emit(SHADER_OPCODE_BROADCAST, tmp, value,
bld.emit_uniformize(invocation));
bld.emit_uniformize(bound_invocation));
bld.MOV(retype(dest, value.type), fs_reg(component(tmp, 0)));
break;