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 specification
https://01.org/sites/default/files/documentation/snb_ihd_os_vol2_part1_0.pdf
sections: 1.6.5.3, 1.6.5.6
the ILK must behave itself in the similar way)
Signed-off-by: Andrii Simiklit <andrii.simik...@globallogic.com>
---
src/intel/compiler/gen6_gs_visitor.cpp | 53 ++++++++++++++++++++++++++++++----
1 file changed, 47 insertions(+), 6 deletions(-)
diff --git a/src/intel/compiler/gen6_gs_visitor.cpp
b/src/intel/compiler/gen6_gs_visitor.cpp
index 66c69fb..2143fd2 100644
--- a/src/intel/compiler/gen6_gs_visitor.cpp
+++ b/src/intel/compiler/gen6_gs_visitor.cpp
@@ -300,10 +300,11 @@ 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 for the EOT message (one for the
+ * necessary to avoid different setups (under Pre-IL only) 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.
+ * something we do not want.
+ * But for ILK and SNB we can not avoid the end the program with an
IF/ELSE/ENDIF block.
*/
inst = emit(GS_OPCODE_URB_WRITE_ALLOCATE);
inst->urb_write_flags = BRW_URB_WRITE_COMPLETE;
@@ -449,8 +450,12 @@ gen6_gs_visitor::emit_thread_end()
if (prog->info.has_transform_feedback_varyings)
xfb_write();
}
- emit(BRW_OPCODE_ENDIF);
-
+ enum { GEN5_ILK = 5 };
+ const bool common_eot_approach_can_be_used = (devinfo->gen < GEN5_ILK);
+ if(common_eot_approach_can_be_used)
+ {
+ emit(BRW_OPCODE_ENDIF);
+ }
/* Finally, emit EOT message.
*
* In gen6 we need to end the thread differently depending on whether we
have
@@ -463,8 +468,30 @@ gen6_gs_visitor::emit_thread_end()
* VUE handle every time we do a URB WRITE, even for the last vertex we
emit.
* 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 by setting the COMPLETE and UNUSED flags in
+ * 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 (gen6) Spec:
https://01.org/sites/default/files/documentation/snb_ihd_os_vol2_part1_0.pdf
+ * 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 (gen6) Spec:
https://01.org/sites/default/files/documentation/snb_ihd_os_vol4_part2_0.pdf
+ * 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 (gen6) Spec:
https://01.org/sites/default/files/documentation/snb_ihd_os_vol2_part1_0.pdf
+ * 1.6.5.6 Thread Termination
*/
this->current_annotation = "gen6 thread end: EOT";
@@ -480,8 +507,22 @@ gen6_gs_visitor::emit_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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