nir: Add pass to combine adjacent scoped memory barriers

SPIR-V generates very granular barriers, however HW and backends might
not necessarily take advantage of those.  This pass provides a general
mechanism to combine such barriers.

Reviewed-by: Eric Anholt <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3224>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index ec281ad5317..1fe0264cbe5 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -4240,6 +4240,17 @@ bool nir_opt_algebraic_before_ffma(nir_shader *shader);
 bool nir_opt_algebraic_late(nir_shader *shader);
 bool nir_opt_constant_folding(nir_shader *shader);
 
+/* Try to combine a and b into a.  Return true if combination was possible,
+ * which will result in b being removed by the pass.  Return false if
+ * combination wasn't possible.
+ */
+typedef bool (*nir_combine_memory_barrier_cb)(
+   nir_intrinsic_instr *a, nir_intrinsic_instr *b, void *data);
+
+bool nir_opt_combine_memory_barriers(nir_shader *shader,
+                                     nir_combine_memory_barrier_cb combine_cb,
+                                     void *data);
+
 bool nir_opt_combine_stores(nir_shader *shader, nir_variable_mode modes);
 
 bool nir_copy_prop(nir_shader *shader);