We can not use the VUE Dereference flags combination for EOT
message under ILK and SNB because the threads are not initialized
there with initial VUE handle unlike Pre-IL.
So to avoid GPU hangs on SNB and ILK we need
to avoid usage of the VUE Dereference flags combination.
(Was tested only on SNB but according to the specification
SNB Volume 2 Part 1: 1.6.5.3, 1.6.5.6
the ILK must behave itself in the similar way)
v2: Approach to fix this issue was changed.
Instead of different EOT flags in the program end
we will create VUE every time even if GS produces no output.
Signed-off-by: Andrii Simiklit <andrii.simik...@globallogic.com>
---
src/intel/compiler/gen6_gs_visitor.cpp | 88 +++++++++-------------------------
1 file changed, 23 insertions(+), 65 deletions(-)
diff --git a/src/intel/compiler/gen6_gs_visitor.cpp
b/src/intel/compiler/gen6_gs_visitor.cpp
index ac3ba55..b831d33 100644
--- a/src/intel/compiler/gen6_gs_visitor.cpp
+++ b/src/intel/compiler/gen6_gs_visitor.cpp
@@ -300,11 +300,10 @@ gen6_gs_visitor::emit_urb_write_opcode(bool complete, int
base_mrf,
/* Otherwise we always request to allocate a new VUE handle. If this is
* the last write before the EOT message and the new handle never gets
* used it will be dereferenced when we send the EOT message. This is
- * necessary to avoid different setups (under Pre-IL only) for the EOT
message (one for the
+ * necessary to avoid different setups for the EOT message (one for the
* case when there is no output and another for the case when there is)
* which would require to end the program with an IF/ELSE/ENDIF block,
- * something we do not want.
- * But for ILK and SNB we can not avoid the end the program with an
IF/ELSE/ENDIF block.
+ * something we do not want.
*/
inst = emit(GS_OPCODE_URB_WRITE_ALLOCATE);
inst->urb_write_flags = BRW_URB_WRITE_COMPLETE;
@@ -351,27 +350,27 @@ gen6_gs_visitor::emit_thread_end()
int max_usable_mrf = FIRST_SPILL_MRF(devinfo->gen);
/* Issue the FF_SYNC message and obtain the initial VUE handle. */
- emit(CMP(dst_null_ud(), this->vertex_count, brw_imm_ud(0u),
BRW_CONDITIONAL_G));
- emit(IF(BRW_PREDICATE_NORMAL));
- {
- this->current_annotation = "gen6 thread end: ff_sync";
+ this->current_annotation = "gen6 thread end: ff_sync";
- vec4_instruction *inst;
- if (prog->info.has_transform_feedback_varyings) {
+ vec4_instruction *inst = NULL;
+ if (prog->info.has_transform_feedback_varyings) {
src_reg sol_temp(this, glsl_type::uvec4_type);
emit(GS_OPCODE_FF_SYNC_SET_PRIMITIVES,
- dst_reg(this->svbi),
- this->vertex_count,
- this->prim_count,
- sol_temp);
+ dst_reg(this->svbi),
+ this->vertex_count,
+ this->prim_count,
+ sol_temp);
inst = emit(GS_OPCODE_FF_SYNC,
dst_reg(this->temp), this->prim_count, this->svbi);
- } else {
+ } else {
inst = emit(GS_OPCODE_FF_SYNC,
dst_reg(this->temp), this->prim_count, brw_imm_ud(0u));
- }
- inst->base_mrf = base_mrf;
+ }
+ inst->base_mrf = base_mrf;
+ emit(CMP(dst_null_ud(), this->vertex_count, brw_imm_ud(0u),
BRW_CONDITIONAL_G));
+ emit(IF(BRW_PREDICATE_NORMAL));
+ {
/* Loop over all buffered vertices and emit URB write messages */
this->current_annotation = "gen6 thread end: urb writes init";
src_reg vertex(this, glsl_type::uint_type);
@@ -415,7 +414,7 @@ gen6_gs_visitor::emit_thread_end()
dst_reg reg = dst_reg(MRF, mrf);
reg.type = output_reg[varying][0].type;
data.type = reg.type;
- vec4_instruction *inst = emit(MOV(reg, data));
+ inst = emit(MOV(reg, data));
inst->force_writemask_all = true;
mrf++;
@@ -450,11 +449,8 @@ gen6_gs_visitor::emit_thread_end()
if (prog->info.has_transform_feedback_varyings)
xfb_write();
}
- const bool common_eot_approach_can_be_used = (devinfo->gen < 5);
- if(common_eot_approach_can_be_used)
- {
- emit(BRW_OPCODE_ENDIF);
- }
+ emit(BRW_OPCODE_ENDIF);
+
/* Finally, emit EOT message.
*
* In gen6 we need to end the thread differently depending on whether we
have
@@ -464,35 +460,11 @@ gen6_gs_visitor::emit_thread_end()
*
* However, this would lead us to end the program with an ENDIF opcode,
* which we want to avoid, so what we do is that we always request a new
- * VUE handle every time we do a URB WRITE, even for the last vertex we
emit.
+ * VUE handle every time, even if GS produces no output.
* With this we make sure that whether we have emitted at least one vertex
* or none at all, we have to finish the thread without writing to the URB,
- * which works for both cases (but only under Pre-IL) by setting
- * the COMPLETE and UNUSED flags in the EOT message.
- *
- * But under ILK or SNB we must not use combination COMPLETE and UNUSED
- * because this combination could be used only for already allocated VUE.
- * But unlike Pre-IL in the ILK and SNB
- * the initial VUE is not passed to threads.
- * This behaver mentioned in specification:
- * SNB Volume 2 Part 1:
- * "1.6.5.3 VUE Allocation (GS, CLIP) [DevIL]"
- * "1.6.5.4 VUE Allocation (GS) [DevSNB+]"
- * "The threads are not passed an initial handle.
- * Instead, they request a first handle (if any)
- * via the URB shared function’s FF_SYNC message (see Shared
Functions).
- * If additional handles are required,
- * the URB_WRITE allocate mechanism (mentioned above) is used."
- *
- * So for ILK and for SNB we must use only UNUSED flag.
- * This is accepteble combination according to:
- * SNB Volume 4 Part 2:
- * "2.4.2 Message Descriptor"
- * "Table lists the valid and invalid combinations of
- * the Complete, Used, Allocate and EOT bits"
- * "Thread terminate non-write of URB"
- * SNB Volume 2 Part 1:
- * "1.6.5.6 Thread Termination"
+ * which works for both cases by setting the COMPLETE and UNUSED flags in
+ * the EOT message.
*/
this->current_annotation = "gen6 thread end: EOT";
@@ -504,26 +476,12 @@ gen6_gs_visitor::emit_thread_end()
emit(GS_OPCODE_SET_DWORD_2, dst_reg(MRF, base_mrf), data);
}
- vec4_instruction *inst = emit(GS_OPCODE_THREAD_END);
+ inst = emit(GS_OPCODE_THREAD_END);
inst->urb_write_flags = BRW_URB_WRITE_COMPLETE | BRW_URB_WRITE_UNUSED;
inst->base_mrf = base_mrf;
inst->mlen = 1;
-
- if(!common_eot_approach_can_be_used)
- {
- emit(BRW_OPCODE_ELSE);
-
- this->current_annotation = "gen6 thread end: EOT";
-
- vec4_instruction *unused_urb_inst = emit(GS_OPCODE_THREAD_END);
- unused_urb_inst->urb_write_flags = BRW_URB_WRITE_UNUSED;
- unused_urb_inst->base_mrf = base_mrf;
- unused_urb_inst->mlen = 1;
-
- emit(BRW_OPCODE_ENDIF);
- }
}
-
+
void
gen6_gs_visitor::setup_payload()
{
--
2.7.4
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