nir/shader_info: remove uses_demote

This flag is mostly redundant with uses_discard and was only
introduced to implement demote with LLVM when it didn't have
that intrinsic.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27617>

src/amd/vulkan/radv_shader.c

@@ -176,7 +176,7 @@ radv_optimize_nir(struct nir_shader *shader, bool optimize_conservatively)
    NIR_PASS(progress, shader, nir_remove_dead_variables,
             nir_var_function_temp | nir_var_shader_in | nir_var_shader_out | nir_var_mem_shared, NULL);
 
-   if (shader->info.stage == MESA_SHADER_FRAGMENT && (shader->info.fs.uses_discard || shader->info.fs.uses_demote)) {
+   if (shader->info.stage == MESA_SHADER_FRAGMENT && shader->info.fs.uses_discard) {
       NIR_PASS(progress, shader, nir_opt_conditional_discard);
       NIR_PASS(progress, shader, nir_opt_move_discards_to_top);
    }

src/broadcom/compiler/nir_to_vir.c

@@ -1917,7 +1917,6 @@ emit_frag_end(struct v3d_compile *c)
         if (c->output_position_index == -1 &&
             !(c->s->info.num_images || c->s->info.num_ssbos) &&
             !c->s->info.fs.uses_discard &&
-            !c->s->info.fs.uses_demote &&
             !c->fs_key->sample_alpha_to_coverage &&
             c->output_sample_mask_index == -1 &&
             has_any_tlb_color_write) {

src/compiler/nir/nir_gather_info.c

@@ -467,8 +467,6 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
    switch (instr->intrinsic) {
    case nir_intrinsic_demote:
    case nir_intrinsic_demote_if:
-      shader->info.fs.uses_demote = true;
-      FALLTHROUGH; /* quads with helper lanes only might be discarded entirely */
    case nir_intrinsic_terminate:
    case nir_intrinsic_terminate_if:
       /* Freedreno uses discard_if() to end GS invocations that don't produce
@@ -1002,7 +1000,6 @@ nir_shader_gather_info(nir_shader *shader, nir_function_impl *entrypoint)
    if (shader->info.stage == MESA_SHADER_FRAGMENT) {
       shader->info.fs.uses_sample_qualifier = false;
       shader->info.fs.uses_discard = false;
-      shader->info.fs.uses_demote = false;
       shader->info.fs.color_is_dual_source = false;
       shader->info.fs.uses_fbfetch_output = false;
       shader->info.fs.needs_quad_helper_invocations = false;

src/compiler/nir/nir_print.c

@@ -2561,7 +2561,6 @@ print_shader_info(const struct shader_info *info, FILE *fp)
 
    case MESA_SHADER_FRAGMENT:
       print_nz_bool(fp, "uses_discard", info->fs.uses_discard);
-      print_nz_bool(fp, "uses_demote", info->fs.uses_demote);
       print_nz_bool(fp, "uses_fbfetch_output", info->fs.uses_fbfetch_output);
       print_nz_bool(fp, "color_is_dual_source", info->fs.color_is_dual_source);
 

src/compiler/shader_info.h

@@ -332,7 +332,6 @@ typedef struct shader_info {
 
       struct {
          bool uses_discard:1;
-         bool uses_demote:1;
          bool uses_fbfetch_output:1;
          bool fbfetch_coherent:1;
          bool color_is_dual_source:1;

src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c

@@ -4421,7 +4421,8 @@ nir_to_spirv(struct nir_shader *s, const struct zink_shader_info *sinfo, const s
    case MESA_SHADER_FRAGMENT:
       if (s->info.fs.uses_sample_shading)
          spirv_builder_emit_cap(&ctx.builder, SpvCapabilitySampleRateShading);
-      if (s->info.fs.uses_demote && spirv_version < SPIRV_VERSION(1, 6))
+      if (s->info.fs.uses_discard && spirv_version < SPIRV_VERSION(1, 6) &&
+          screen->info.have_EXT_shader_demote_to_helper_invocation)
          spirv_builder_emit_extension(&ctx.builder,
                                       "SPV_EXT_demote_to_helper_invocation");
       break;

src/intel/compiler/brw_fs.cpp

@@ -3644,8 +3644,7 @@ brw_nir_populate_wm_prog_data(nir_shader *shader,
                               struct brw_wm_prog_data *prog_data,
                               const struct brw_mue_map *mue_map)
 {
-   prog_data->uses_kill = shader->info.fs.uses_discard ||
-                          shader->info.fs.uses_demote;
+   prog_data->uses_kill = shader->info.fs.uses_discard;
    prog_data->uses_omask = !key->ignore_sample_mask_out &&
       (shader->info.outputs_written & BITFIELD64_BIT(FRAG_RESULT_SAMPLE_MASK));
    prog_data->max_polygons = 1;

src/intel/compiler/elk/elk_fs.cpp

@@ -6450,7 +6450,6 @@ elk_nir_populate_wm_prog_data(nir_shader *shader,
     * so the shader definitely kills pixels.
     */
    prog_data->uses_kill = shader->info.fs.uses_discard ||
-                          shader->info.fs.uses_demote ||
                           key->emit_alpha_test;
    prog_data->uses_omask = !key->ignore_sample_mask_out &&
       (shader->info.outputs_written & BITFIELD64_BIT(FRAG_RESULT_SAMPLE_MASK));

src/nouveau/codegen/nv50_ir_from_nir.cpp

@@ -1322,7 +1322,7 @@ Converter::parseNIR()
       info_out->prop.fp.postDepthCoverage = nir->info.fs.post_depth_coverage;
       info_out->prop.fp.readsSampleLocations =
          BITSET_TEST(nir->info.system_values_read, SYSTEM_VALUE_SAMPLE_POS);
-      info_out->prop.fp.usesDiscard = nir->info.fs.uses_discard || nir->info.fs.uses_demote;
+      info_out->prop.fp.usesDiscard = nir->info.fs.uses_discard;
       info_out->prop.fp.usesSampleMaskIn =
          BITSET_TEST(nir->info.system_values_read, SYSTEM_VALUE_SAMPLE_MASK_IN);
       break;

src/panfrost/lib/pan_shader.c

@@ -167,8 +167,7 @@ GENX(pan_shader_compile)(nir_shader *s, struct panfrost_compile_inputs *inputs,
       /* List of reasons we need to execute frag shaders when things
        * are masked off */
 
-      info->fs.sidefx = s->info.writes_memory || s->info.fs.uses_discard ||
-                        s->info.fs.uses_demote;
+      info->fs.sidefx = s->info.writes_memory || s->info.fs.uses_discard;
 
       /* With suitable ZSA/blend, is early-z possible? */
       info->fs.can_early_z = !info->fs.sidefx && !info->fs.writes_depth &&