intel/compiler: insert URB fence before task/mesh termination

Bspec 53421 says:
"A URB fence memory is typically performed prior the thread
exit message, so that the next thread dispatch that reads
that URB memory will see it."

Cc: 22.1 <mesa-stable>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16665>

src/intel/compiler/brw_fs.cpp

@@ -7039,6 +7039,8 @@ fs_visitor::run_task(bool allow_spilling)
    if (failed)
       return false;
 
+   emit_urb_fence();
+
    emit_cs_terminate();
 
    calculate_cfg();
@@ -7084,6 +7086,8 @@ fs_visitor::run_mesh(bool allow_spilling)
    if (failed)
       return false;
 
+   emit_urb_fence();
+
    emit_cs_terminate();
 
    calculate_cfg();

src/intel/compiler/brw_fs.h

@@ -327,6 +327,7 @@ public:
    void emit_gs_input_load(const fs_reg &dst, const nir_src &vertex_src,
                            unsigned base_offset, const nir_src &offset_src,
                            unsigned num_components, unsigned first_component);
+   void emit_urb_fence();
    void emit_cs_terminate();
    fs_reg emit_work_group_id_setup();
 

src/intel/compiler/brw_fs_visitor.cpp

@@ -27,6 +27,7 @@
  * makes it easier to do backend-specific optimizations than doing so
  * in the GLSL IR or in the native code.
  */
+#include "brw_eu.h"
 #include "brw_fs.h"
 #include "compiler/glsl_types.h"
 
@@ -1045,6 +1046,24 @@ fs_visitor::emit_urb_writes(const fs_reg &gs_vertex_count)
    }
 }
 
+void
+fs_visitor::emit_urb_fence()
+{
+   fs_reg dst = bld.vgrf(BRW_REGISTER_TYPE_UD);
+   fs_inst *fence = bld.emit(SHADER_OPCODE_MEMORY_FENCE, dst,
+                             brw_vec8_grf(0, 0),
+                             brw_imm_ud(true),
+                             brw_imm_ud(0));
+   fence->sfid = BRW_SFID_URB;
+   fence->desc = lsc_fence_msg_desc(devinfo, LSC_FENCE_LOCAL,
+                                    LSC_FLUSH_TYPE_NONE, true);
+
+   bld.exec_all().group(1, 0).emit(FS_OPCODE_SCHEDULING_FENCE,
+                                   bld.null_reg_ud(),
+                                   &dst,
+                                   1);
+}
+
 void
 fs_visitor::emit_cs_terminate()
 {