Mesa (master): intel/nir: Add a memory barrier before barrier()

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Module: Mesa
Branch: master
Commit: 803fad43c3f9a89f0d8409bd33280b5457b104c7
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=803fad43c3f9a89f0d8409bd33280b5457b104c7

Author: Jason Ekstrand <jason at jlekstrand.net>
Date:   Tue Jan  7 13:20:10 2020 -0600

intel/nir: Add a memory barrier before barrier()

Our barrier instruction does not implicitly do a memory fence but the
GLSL barrier() intrinsic is supposed to.  The easiest back-portable
solution is to just add the NIR barriers.  We'll sort this out more
properly in later commits.

Cc: mesa-stable at lists.freedesktop.org
Closes: #2138
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>

---

 src/intel/compiler/brw_nir_lower_cs_intrinsics.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/intel/compiler/brw_nir_lower_cs_intrinsics.c b/src/intel/compiler/brw_nir_lower_cs_intrinsics.c
index 434ad005281..3f48a3c5dda 100644
--- a/src/intel/compiler/brw_nir_lower_cs_intrinsics.c
+++ b/src/intel/compiler/brw_nir_lower_cs_intrinsics.c
@@ -55,6 +55,20 @@ lower_cs_intrinsics_convert_block(struct lower_intrinsics_state *state,
 
       nir_ssa_def *sysval;
       switch (intrinsic->intrinsic) {
+      case nir_intrinsic_barrier: {
+         /* Our HW barrier instruction doesn't do a memory barrier for us but
+          * the GLSL barrier() intrinsic does for shared memory.  Insert a
+          * shared memory barrier before every barrier().
+          */
+         b->cursor = nir_before_instr(&intrinsic->instr);
+
+         nir_intrinsic_instr *shared_barrier =
+            nir_intrinsic_instr_create(b->shader,
+                                       nir_intrinsic_memory_barrier_shared);
+         nir_builder_instr_insert(b, &shared_barrier->instr);
+         continue;
+      }
+
       case nir_intrinsic_load_local_invocation_index:
       case nir_intrinsic_load_local_invocation_id: {
          /* First time we are using those, so let's calculate them. */