ir3: Add ir3_trim_constlen()

This provides the policy for how to handle reducing constlen for some
stages.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5607>

diff --git a/src/freedreno/ir3/ir3_shader.c b/src/freedreno/ir3/ir3_shader.c
index 6c64f84..37e1f8b 100644 (file)
--- a/src/freedreno/ir3/ir3_shader.c
+++ b/src/freedreno/ir3/ir3_shader.c
@@ -326,6 +326,75 @@ ir3_setup_used_key(struct ir3_shader *shader)
        }
 }
 
+
+/* Given an array of constlen's, decrease some of them so that the sum stays
+ * within "combined_limit" while trying to fairly share the reduction. Returns
+ * a bitfield of which stages should be trimmed.
+ */
+static uint32_t
+trim_constlens(unsigned *constlens,
+                          unsigned first_stage, unsigned last_stage,
+                          unsigned combined_limit, unsigned safe_limit)
+{
+   unsigned cur_total = 0;
+   for (unsigned i = first_stage; i <= last_stage; i++) {
+      cur_total += constlens[i];
+   }
+
+   unsigned max_stage;
+   unsigned max_const = 0;
+   uint32_t trimmed = 0;
+
+   while (cur_total > combined_limit) {
+          for (unsigned i = first_stage; i <= last_stage; i++) {
+                  if (constlens[i] >= max_const) {
+                          max_stage = i;
+                          max_const = constlens[i];
+                  }
+          }
+
+          assert(max_const > safe_limit);
+          trimmed |= 1 << max_stage;
+          cur_total = cur_total - max_const + safe_limit;
+          constlens[max_stage] = safe_limit;
+   }
+
+   return trimmed;
+}
+
+/* Figures out which stages in the pipeline to use the "safe" constlen for, in
+ * order to satisfy all shared constlen limits.
+ */
+uint32_t
+ir3_trim_constlen(struct ir3_shader_variant **variants,
+                                 const struct ir3_compiler *compiler)
+{
+       unsigned constlens[MESA_SHADER_STAGES] = {};
+
+       for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
+               if (variants[i])
+                       constlens[i] = variants[i]->constlen;
+       }
+
+       uint32_t trimmed = 0;
+       STATIC_ASSERT(MESA_SHADER_STAGES <= 8 * sizeof(trimmed));
+
+       /* There are two shared limits to take into account, the geometry limit on
+        * a6xx and the total limit. The frag limit on a6xx only matters for a
+        * single stage, so it's always satisfied with the first variant.
+        */
+       if (compiler->gpu_id >= 600) {
+               trimmed |=
+                       trim_constlens(constlens, MESA_SHADER_VERTEX, MESA_SHADER_GEOMETRY,
+                                                  compiler->max_const_geom, compiler->max_const_safe);
+       }
+       trimmed |=
+               trim_constlens(constlens, MESA_SHADER_VERTEX, MESA_SHADER_FRAGMENT,
+                                          compiler->max_const_pipeline, compiler->max_const_safe);
+
+       return trimmed;
+}
+
 struct ir3_shader *
 ir3_shader_from_nir(struct ir3_compiler *compiler, nir_shader *nir,
                unsigned reserved_user_consts, struct ir3_stream_output_info *stream_output)

diff --git a/src/freedreno/ir3/ir3_shader.h b/src/freedreno/ir3/ir3_shader.h
index b2dbc64..8e15442 100644 (file)
--- a/src/freedreno/ir3/ir3_shader.h
+++ b/src/freedreno/ir3/ir3_shader.h
@@ -704,6 +704,8 @@ struct ir3_shader_variant * ir3_shader_get_variant(struct ir3_shader *shader,
                const struct ir3_shader_key *key, bool binning_pass, bool *created);
 struct ir3_shader * ir3_shader_from_nir(struct ir3_compiler *compiler, nir_shader *nir,
                unsigned reserved_user_consts, struct ir3_stream_output_info *stream_output);
+uint32_t ir3_trim_constlen(struct ir3_shader_variant **variants,
+               const struct ir3_compiler *compiler);
 void ir3_shader_destroy(struct ir3_shader *shader);
 void ir3_shader_disasm(struct ir3_shader_variant *so, uint32_t *bin, FILE *out);
 uint64_t ir3_shader_outputs(const struct ir3_shader *so);