Mesa (main): broadcom/compiler: lower nir_intrinsic_load_num_subgroups

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Module: Mesa
Branch: main
Commit: a9ad04f17d9f2c902141d3a362e2993ac9ce3ab8
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=a9ad04f17d9f2c902141d3a362e2993ac9ce3ab8

Author: Iago Toral Quiroga <itoral at igalia.com>
Date:   Tue Jun 22 12:00:55 2021 +0200

broadcom/compiler: lower nir_intrinsic_load_num_subgroups

The number of subgroups is the local workgroup size divided by the
dispatch width.

Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11620>

---

 src/broadcom/compiler/nir_to_vir.c |  4 +++
 src/broadcom/compiler/vir.c        | 69 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/src/broadcom/compiler/nir_to_vir.c b/src/broadcom/compiler/nir_to_vir.c
index de1cc9e6077..6f3d2c5a8b5 100644
--- a/src/broadcom/compiler/nir_to_vir.c
+++ b/src/broadcom/compiler/nir_to_vir.c
@@ -3241,6 +3241,10 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
                 break;
         }
 
+        case nir_intrinsic_load_num_subgroups:
+                unreachable("Should have been lowered");
+                break;
+
         default:
                 fprintf(stderr, "Unknown intrinsic: ");
                 nir_print_instr(&instr->instr, stderr);
diff --git a/src/broadcom/compiler/vir.c b/src/broadcom/compiler/vir.c
index e1d174c8030..1b35ed95033 100644
--- a/src/broadcom/compiler/vir.c
+++ b/src/broadcom/compiler/vir.c
@@ -25,6 +25,7 @@
 #include "v3d_compiler.h"
 #include "util/u_prim.h"
 #include "compiler/nir/nir_schedule.h"
+#include "compiler/nir/nir_builder.h"
 
 int
 vir_get_nsrc(struct qinst *inst)
@@ -1350,6 +1351,72 @@ v3d_nir_sort_constant_ubo_loads(nir_shader *s, struct v3d_compile *c)
         return c->sorted_any_ubo_loads;
 }
 
+static void
+lower_load_num_subgroups(struct v3d_compile *c,
+                         nir_builder *b,
+                         nir_intrinsic_instr *intr)
+{
+        assert(c->s->info.stage == MESA_SHADER_COMPUTE);
+        assert(intr->intrinsic == nir_intrinsic_load_num_subgroups);
+
+        b->cursor = nir_after_instr(&intr->instr);
+        uint32_t num_subgroups =
+                DIV_ROUND_UP(c->s->info.workgroup_size[0] *
+                             c->s->info.workgroup_size[1] *
+                             c->s->info.workgroup_size[2], V3D_CHANNELS);
+        nir_ssa_def *result = nir_imm_int(b, num_subgroups);
+        nir_ssa_def_rewrite_uses(&intr->dest.ssa, result);
+        nir_instr_remove(&intr->instr);
+}
+
+static bool
+lower_subgroup_intrinsics(struct v3d_compile *c,
+                          nir_block *block, nir_builder *b)
+{
+        bool progress = false;
+        nir_foreach_instr_safe(inst, block) {
+                if (inst->type != nir_instr_type_intrinsic)
+                        continue;;
+
+                nir_intrinsic_instr *intr =
+                        nir_instr_as_intrinsic(inst);
+                if (!intr)
+                        continue;
+
+                switch (intr->intrinsic) {
+                case nir_intrinsic_load_num_subgroups: {
+                        lower_load_num_subgroups(c, b, intr);
+                        progress = true;
+                        break;
+                }
+                default:
+                        break;
+                }
+        }
+
+        return progress;
+}
+
+static bool
+v3d_nir_lower_subgroup_intrinsics(nir_shader *s, struct v3d_compile *c)
+{
+        bool progress = false;
+        nir_foreach_function(function, s) {
+                if (function->impl) {
+                        nir_builder b;
+                        nir_builder_init(&b, function->impl);
+
+                        nir_foreach_block(block, function->impl)
+                                progress |= lower_subgroup_intrinsics(c, block, &b);
+
+                        nir_metadata_preserve(function->impl,
+                                              nir_metadata_block_index |
+                                              nir_metadata_dominance);
+                }
+        }
+        return progress;
+}
+
 static void
 v3d_attempt_compile(struct v3d_compile *c)
 {
@@ -1422,6 +1489,8 @@ v3d_attempt_compile(struct v3d_compile *c)
 
         NIR_PASS_V(c->s, nir_lower_wrmasks, should_split_wrmask, c->s);
 
+        NIR_PASS_V(c->s, v3d_nir_lower_subgroup_intrinsics, c);
+
         v3d_optimize_nir(c, c->s);
 
         /* Do late algebraic optimization to turn add(a, neg(b)) back into