On Wed, 2017-01-04 at 21:33 -0800, Kenneth Graunke wrote:
> If the VUE map has slots at the end which the shader does not write,
> then we'd "flush" (constructing an URB write) on the last output it
> actually wrote. Then, we'd construct another SEND with EOT, but with
> no actual payload data. That's not legal.
>
> For example, SSO programs have clip distance slots allocated no
> matter
> what, but the shader may not write them. If it doesn't write any
> user
> defined varyings, then the clip distance slots will be the last ones.
>
> Found while debugging
> dEQP-VK.tessellation.shader_input_output.gl_position_vs_to_tcs_to_tes
>
> Cc: mesa-sta...@lists.freedesktop.org
> Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> ---
> src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index 14415bd5c7a..08ac7bc276a 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -672,6 +672,14 @@ fs_visitor::emit_urb_writes(const fs_reg
> &gs_vertex_count)
> length = 0;
> urb_offset = starting_urb_offset;
> flush = false;
> +
It might be nice to add a small comment about why we have slots that
are not written to here.
/* SSO shaders can have slots that are never actually written to so
* ignore them when looking for the last slot.
*/
Or I'm sure you can come up with something better.
Otherwise:
Reviewed-by: Timothy Arceri <timothy.arc...@collabora.com>
> + int last_slot = vue_map->num_slots - 1;
> + while (last_slot > 0 &&
> + (vue_map->slot_to_varying[last_slot] ==
> BRW_VARYING_SLOT_PAD ||
> + outputs[vue_map->slot_to_varying[last_slot]].file ==
> BAD_FILE)) {
> + last_slot--;
> + }
> +
> for (slot = 0; slot < vue_map->num_slots; slot++) {
> int varying = vue_map->slot_to_varying[slot];
> switch (varying) {
> @@ -757,8 +765,7 @@ fs_visitor::emit_urb_writes(const fs_reg
> &gs_vertex_count)
> * the last slot or if we need to flush (see BAD_FILE varying
> case
> * above), emit a URB write send now to flush out the data.
> */
> - int last = slot == vue_map->num_slots - 1;
> - if (length == 8 || last)
> + if (length == 8 || slot == last_slot)
> flush = true;
> if (flush) {
> fs_reg *payload_sources =
> @@ -777,7 +784,7 @@ fs_visitor::emit_urb_writes(const fs_reg
> &gs_vertex_count)
> header_size);
>
> fs_inst *inst = abld.emit(opcode, reg_undef, payload);
> - inst->eot = last && stage != MESA_SHADER_GEOMETRY;
> + inst->eot = slot == last_slot && stage !=
> MESA_SHADER_GEOMETRY;
> inst->mlen = length + header_size;
> inst->offset = urb_offset;
> urb_offset = starting_urb_offset + slot + 1;
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