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brw: ensure VUE header writes in HS/DS/GS stages

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Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12820
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34041>
(cherry picked from commit 35df3925ca)
This commit is contained in:
Lionel Landwerlin 2025-03-13 10:05:55 +02:00 • committed by Eric Engestrom
parent 267502f9f3
commit 56b954a37a
2 changed files with 37 additions and 6 deletions
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2
.pick_status.json
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@ -954,7 +954,7 @@
"description": "brw: ensure VUE header writes in HS/DS/GS stages",
"nominated": true,
"nomination_type": 1,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": null,
"notes": null

41
src/intel/compiler/brw_fs_visitor.cpp
View file

@ -122,11 +122,42 @@ fs_visitor::emit_urb_writes(const brw_reg &gs_vertex_count)
switch (varying) {
case VARYING_SLOT_PSIZ: {
/* The point size varying slot is the vue header and is always in the
* vue map. But often none of the special varyings that live there
* are written and in that case we can skip writing to the vue
* header, provided the corresponding state properly clamps the
* values further down the pipeline. */
if ((vue_map->slots_valid & psiz_mask) == 0) {
* vue map. But often none of the special varyings that live there
* are written and for the vertex shaders we can skip writing to the
* VUE header because it is setup by the VF fixed function. All other
* pre-rasterization stages should setup the VUE header properly as
* describe in the SKL PRMs, Volume 7: 3D-Media-GPGPU, Vertex URB
* Entry (VUE) Formats:
*
* "VUEs are written in two ways:
*
* - At the top of the 3D Geometry pipeline, the VF's
* InputAssembly function creates VUEs and initializes them
* from data extracted from Vertex Buffers as well as
* internally generated data.
*
* - VS, GS, HS and DS threads can compute, format, and write
* new VUEs as thread output."
*
* "Software must ensure that any VUEs subject to readback by the
* 3D pipeline start with a valid Vertex Header. This extends to
* all VUEs with the following exceptions:
*
* - If the VS function is enabled, the VF-written VUEs are not
* required to have Vertex Headers, as the VS-incoming
* vertices are guaranteed to be consumed by the VS (i.e.,
* the VS thread is responsible for overwriting the input
* vertex data).
*
* - If the GS FF is enabled, neither VF-written VUEs nor VS
* thread-generated VUEs are required to have Vertex Headers,
* as the GS will consume all incoming vertices.
*
* - If Rendering is disabled, VertexHeaders are not required
* anywhere."
*/
if ((vue_map->slots_valid & psiz_mask) == 0 &&
stage == MESA_SHADER_VERTEX) {
assert(length == 0);
urb_offset++;
break;