nir: Add a new subgroups lowering pass

This commit pulls nir_lower_read_invocations_to_scalar along with most
of the guts of nir_opt_intrinsics (which mostly does subgroup lowering)
into a new nir_lower_subgroups pass.  There are various other bits of
subgroup lowering that we're going to want to do so it makes a bit more
sense to keep it all together in one pass.  We also move it in i965 to
happen after nir_lower_system_values to ensure that because we want to
handle the subgroup mask system value intrinsics here.

Reviewed-by: Iago Toral Quiroga <[email protected]>

2 files changed, 7 insertions, 4 deletions

diff --git a/src/intel/compiler/brw_compiler.c b/src/intel/compiler/brw_compiler.c
index f6120cbf0ac..8c709b55a10 100644
--- a/src/intel/compiler/brw_compiler.c
+++ b/src/intel/compiler/brw_compiler.c
@@ -57,7 +57,6 @@ static const struct nir_shader_compiler_options scalar_nir_options = {
    .lower_unpack_snorm_4x8 = true,
    .lower_unpack_unorm_2x16 = true,
    .lower_unpack_unorm_4x8 = true,
-   .lower_subgroup_masks = true,
    .max_subgroup_size = 32,
    .max_unroll_iterations = 32,
 };
@@ -80,7 +79,6 @@ static const struct nir_shader_compiler_options vector_nir_options = {
    .lower_unpack_unorm_2x16 = true,
    .lower_extract_byte = true,
    .lower_extract_word = true,
-   .lower_vote_trivial = true,
    .max_unroll_iterations = 32,
 };
 
@@ -99,7 +97,6 @@ static const struct nir_shader_compiler_options vector_nir_options_gen6 = {
    .lower_unpack_unorm_2x16 = true,
    .lower_extract_byte = true,
    .lower_extract_word = true,
-   .lower_vote_trivial = true,
    .max_unroll_iterations = 32,
 };
 
diff --git a/src/intel/compiler/brw_nir.c b/src/intel/compiler/brw_nir.c
index e5ff6deb2f7..f599f748a8a 100644
--- a/src/intel/compiler/brw_nir.c
+++ b/src/intel/compiler/brw_nir.c
@@ -620,7 +620,6 @@ brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir)
 
    OPT(nir_lower_tex, &tex_options);
    OPT(nir_normalize_cubemap_coords);
-   OPT(nir_lower_read_invocation_to_scalar);
 
    OPT(nir_lower_global_vars_to_local);
 
@@ -637,6 +636,13 @@ brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir)
 
    OPT(nir_lower_system_values);
 
+   const nir_lower_subgroups_options subgroups_options = {
+      .lower_to_scalar = true,
+      .lower_subgroup_masks = true,
+      .lower_vote_trivial = !is_scalar,
+   };
+   OPT(nir_lower_subgroups, &subgroups_options);
+
    OPT(nir_lower_clip_cull_distance_arrays);
 
    nir_variable_mode indirect_mask = 0;