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]>

1 files changed, 6 insertions, 65 deletions

diff --git a/src/compiler/nir/nir_opt_intrinsics.c b/src/compiler/nir/nir_opt_intrinsics.c
index d5fdc516007..98c8b1a01e8 100644
--- a/src/compiler/nir/nir_opt_intrinsics.c
+++ b/src/compiler/nir/nir_opt_intrinsics.c
@@ -28,26 +28,6 @@
  * \file nir_opt_intrinsics.c
  */
 
-static nir_ssa_def *
-high_subgroup_mask(nir_builder *b,
-                   nir_ssa_def *count,
-                   uint64_t base_mask)
-{
-   /* group_mask could probably be calculated more efficiently but we want to
-    * be sure not to shift by 64 if the subgroup size is 64 because the GLSL
-    * shift operator is undefined in that case. In any case if we were worried
-    * about efficency this should probably be done further down because the
-    * subgroup size is likely to be known at compile time.
-    */
-   nir_ssa_def *subgroup_size = nir_load_subgroup_size(b);
-   nir_ssa_def *all_bits = nir_imm_int64(b, ~0ull);
-   nir_ssa_def *shift = nir_isub(b, nir_imm_int(b, 64), subgroup_size);
-   nir_ssa_def *group_mask = nir_ushr(b, all_bits, shift);
-   nir_ssa_def *higher_bits = nir_ishl(b, nir_imm_int64(b, base_mask), count);
-
-   return nir_iand(b, higher_bits, group_mask);
-}
-
 static bool
 opt_intrinsics_impl(nir_function_impl *impl)
 {
@@ -66,22 +46,14 @@ opt_intrinsics_impl(nir_function_impl *impl)
 
          switch (intrin->intrinsic) {
          case nir_intrinsic_vote_any:
-         case nir_intrinsic_vote_all: {
-            nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
-            if (!val && !b.shader->options->lower_vote_trivial)
-               continue;
-
-            replacement = nir_ssa_for_src(&b, intrin->src[0], 1);
+         case nir_intrinsic_vote_all:
+            if (nir_src_as_const_value(intrin->src[0]))
+               replacement = nir_ssa_for_src(&b, intrin->src[0], 1);
             break;
-         }
-         case nir_intrinsic_vote_eq: {
-            nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
-            if (!val && !b.shader->options->lower_vote_trivial)
-               continue;
-
-            replacement = nir_imm_int(&b, NIR_TRUE);
+         case nir_intrinsic_vote_eq:
+            if (nir_src_as_const_value(intrin->src[0]))
+               replacement = nir_imm_int(&b, NIR_TRUE);
             break;
-         }
          case nir_intrinsic_ballot: {
             assert(b.shader->options->max_subgroup_size != 0);
             if (b.shader->options->max_subgroup_size > 32 ||
@@ -100,37 +72,6 @@ opt_intrinsics_impl(nir_function_impl *impl)
                                                  nir_imm_int(&b, 0));
             break;
          }
-         case nir_intrinsic_load_subgroup_eq_mask:
-         case nir_intrinsic_load_subgroup_ge_mask:
-         case nir_intrinsic_load_subgroup_gt_mask:
-         case nir_intrinsic_load_subgroup_le_mask:
-         case nir_intrinsic_load_subgroup_lt_mask: {
-            if (!b.shader->options->lower_subgroup_masks)
-               break;
-
-            nir_ssa_def *count = nir_load_subgroup_invocation(&b);
-
-            switch (intrin->intrinsic) {
-            case nir_intrinsic_load_subgroup_eq_mask:
-               replacement = nir_ishl(&b, nir_imm_int64(&b, 1ull), count);
-               break;
-            case nir_intrinsic_load_subgroup_ge_mask:
-               replacement = high_subgroup_mask(&b, count, ~0ull);
-               break;
-            case nir_intrinsic_load_subgroup_gt_mask:
-               replacement = high_subgroup_mask(&b, count, ~1ull);
-               break;
-            case nir_intrinsic_load_subgroup_le_mask:
-               replacement = nir_inot(&b, nir_ishl(&b, nir_imm_int64(&b, ~1ull), count));
-               break;
-            case nir_intrinsic_load_subgroup_lt_mask:
-               replacement = nir_inot(&b, nir_ishl(&b, nir_imm_int64(&b, ~0ull), count));
-               break;
-            default:
-               unreachable("you seriously can't tell this is unreachable?");
-            }
-            break;
-         }
          default:
             break;
          }