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intel/fs: Rework zero-length URB write handling

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Originally we tried to handle this case based on slots_valid.  However,
there are a number of ways that this can go wrong.  For one, we throw
away any trailing slots which either aren't written or are set to
VARYING_SLOT_PAD.  Second, even if PSIZ is a valid slot, we may not
actually write anything there.  Between the lot of these, it was
possible to end up in a case where we tried to do a regular URB write
but ended up with a length of 1 which is invalid.  This commit moves it
to the end and makes it based on a new boolean flag urb_written.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Cc: mesa-stable@lists.freedesktop.org
This commit is contained in:
Jason Ekstrand
2017-09-01 09:59:34 -07:00
parent 6132992cdb
commit 7a82ad54bb
1 changed files with 31 additions and 29 deletions
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60
src/intel/compiler/brw_fs_visitor.cpp
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@@ -566,34 +566,6 @@ fs_visitor::emit_urb_writes(const fs_reg &gs_vertex_count)
else
urb_handle = fs_reg(retype(brw_vec8_grf(1, 0), BRW_REGISTER_TYPE_UD));
/* If we don't have any valid slots to write, just do a minimal urb write
* send to terminate the shader. This includes 1 slot of undefined data,
* because it's invalid to write 0 data:
*
* From the Broadwell PRM, Volume 7: 3D Media GPGPU, Shared Functions -
* Unified Return Buffer (URB) > URB_SIMD8_Write and URB_SIMD8_Read >
* Write Data Payload:
*
* "The write data payload can be between 1 and 8 message phases long."
*/
if (vue_map->slots_valid == 0) {
/* For GS, just turn EmitVertex() into a no-op. We don't want it to
* end the thread, and emit_gs_thread_end() already emits a SEND with
* EOT at the end of the program for us.
*/
if (stage == MESA_SHADER_GEOMETRY)
return;
fs_reg payload = fs_reg(VGRF, alloc.allocate(2), BRW_REGISTER_TYPE_UD);
bld.exec_all().MOV(payload, urb_handle);
fs_inst *inst = bld.emit(SHADER_OPCODE_URB_WRITE_SIMD8, reg_undef, payload);
inst->eot = true;
inst->mlen = 2;
inst->offset = 1;
return;
}
opcode opcode = SHADER_OPCODE_URB_WRITE_SIMD8;
int header_size = 1;
fs_reg per_slot_offsets;
@@ -645,6 +617,7 @@ fs_visitor::emit_urb_writes(const fs_reg &gs_vertex_count)
last_slot--;
}
bool urb_written = false;
for (slot = 0; slot < vue_map->num_slots; slot++) {
int varying = vue_map->slot_to_varying[slot];
switch (varying) {
@@ -730,7 +703,7 @@ 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.
*/
if (length == 8 || slot == last_slot)
if (length == 8 || (length > 0 && slot == last_slot))
flush = true;
if (flush) {
fs_reg *payload_sources =
@@ -755,8 +728,37 @@ fs_visitor::emit_urb_writes(const fs_reg &gs_vertex_count)
urb_offset = starting_urb_offset + slot + 1;
length = 0;
flush = false;
urb_written = true;
}
}
/* If we don't have any valid slots to write, just do a minimal urb write
* send to terminate the shader. This includes 1 slot of undefined data,
* because it's invalid to write 0 data:
*
* From the Broadwell PRM, Volume 7: 3D Media GPGPU, Shared Functions -
* Unified Return Buffer (URB) > URB_SIMD8_Write and URB_SIMD8_Read >
* Write Data Payload:
*
* "The write data payload can be between 1 and 8 message phases long."
*/
if (!urb_written) {
/* For GS, just turn EmitVertex() into a no-op. We don't want it to
* end the thread, and emit_gs_thread_end() already emits a SEND with
* EOT at the end of the program for us.
*/
if (stage == MESA_SHADER_GEOMETRY)
return;
fs_reg payload = fs_reg(VGRF, alloc.allocate(2), BRW_REGISTER_TYPE_UD);
bld.exec_all().MOV(payload, urb_handle);
fs_inst *inst = bld.emit(SHADER_OPCODE_URB_WRITE_SIMD8, reg_undef, payload);
inst->eot = true;
inst->mlen = 2;
inst->offset = 1;
return;
}
}
void