Mesa (main): v3dv: drop default sampler states if not used

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Module: Mesa
Branch: main
Commit: 1571954be95a06154eaa83f572167b1623aef895
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1571954be95a06154eaa83f572167b1623aef895

Author: Iago Toral Quiroga <itoral at igalia.com>
Date:   Mon May  2 13:31:27 2022 +0200

v3dv: drop default sampler states if not used

If a shader doesn't use any samplers (including default sampler states),
make sure we drop them so other parts of the driver can recognize that
the program doesn't actually use any samplers at all.

Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16322>

---

 src/broadcom/vulkan/v3dv_pipeline.c | 40 ++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/src/broadcom/vulkan/v3dv_pipeline.c b/src/broadcom/vulkan/v3dv_pipeline.c
index 66ceb12f761..4000bec1ec3 100644
--- a/src/broadcom/vulkan/v3dv_pipeline.c
+++ b/src/broadcom/vulkan/v3dv_pipeline.c
@@ -743,7 +743,8 @@ static bool
 lower_sampler(nir_builder *b, nir_tex_instr *instr,
               nir_shader *shader,
               struct v3dv_pipeline *pipeline,
-              const struct v3dv_pipeline_layout *layout)
+              const struct v3dv_pipeline_layout *layout,
+              bool *needs_default_sampler_state)
 {
    uint8_t return_size = 0;
 
@@ -767,6 +768,7 @@ lower_sampler(nir_builder *b, nir_tex_instr *instr,
     * case, and we ensure that it is using the correct return size.
     */
    if (sampler_idx < 0) {
+      *needs_default_sampler_state = true;
       instr->sampler_index = return_size == 16 ?
          V3DV_NO_SAMPLER_16BIT_IDX : V3DV_NO_SAMPLER_32BIT_IDX;
    }
@@ -911,7 +913,8 @@ static bool
 lower_impl(nir_function_impl *impl,
            nir_shader *shader,
            struct v3dv_pipeline *pipeline,
-           const struct v3dv_pipeline_layout *layout)
+           const struct v3dv_pipeline_layout *layout,
+           bool *needs_default_sampler_state)
 {
    nir_builder b;
    nir_builder_init(&b, impl);
@@ -923,7 +926,8 @@ lower_impl(nir_function_impl *impl,
          switch (instr->type) {
          case nir_instr_type_tex:
             progress |=
-               lower_sampler(&b, nir_instr_as_tex(instr), shader, pipeline, layout);
+               lower_sampler(&b, nir_instr_as_tex(instr), shader, pipeline,
+                             layout, needs_default_sampler_state);
             break;
          case nir_instr_type_intrinsic:
             progress |=
@@ -942,13 +946,16 @@ lower_impl(nir_function_impl *impl,
 static bool
 lower_pipeline_layout_info(nir_shader *shader,
                            struct v3dv_pipeline *pipeline,
-                           const struct v3dv_pipeline_layout *layout)
+                           const struct v3dv_pipeline_layout *layout,
+                           bool *needs_default_sampler_state)
 {
    bool progress = false;
+   *needs_default_sampler_state = false;
 
    nir_foreach_function(function, shader) {
       if (function->impl)
-         progress |= lower_impl(function->impl, shader, pipeline, layout);
+         progress |= lower_impl(function->impl, shader, pipeline, layout,
+                                needs_default_sampler_state);
    }
 
    return progress;
@@ -1792,18 +1799,27 @@ pipeline_lower_nir(struct v3dv_pipeline *pipeline,
     * We add two of those, one for the case we need a 16bit return_size, and
     * another for the case we need a 32bit return size.
     */
-   UNUSED unsigned index =
-      descriptor_map_add(&pipeline->shared_data->maps[p_stage->stage]->sampler_map,
-                         -1, -1, -1, 0, 0, 16);
+   struct v3dv_descriptor_maps *maps =
+      pipeline->shared_data->maps[p_stage->stage];
+
+   UNUSED unsigned index;
+   index = descriptor_map_add(&maps->sampler_map, -1, -1, -1, 0, 0, 16);
    assert(index == V3DV_NO_SAMPLER_16BIT_IDX);
 
-   index =
-      descriptor_map_add(&pipeline->shared_data->maps[p_stage->stage]->sampler_map,
-                         -2, -2, -2, 0, 0, 32);
+   index = descriptor_map_add(&maps->sampler_map, -2, -2, -2, 0, 0, 32);
    assert(index == V3DV_NO_SAMPLER_32BIT_IDX);
 
    /* Apply the actual pipeline layout to UBOs, SSBOs, and textures */
-   NIR_PASS_V(p_stage->nir, lower_pipeline_layout_info, pipeline, layout);
+   bool needs_default_sampler_state = false;
+   NIR_PASS_V(p_stage->nir, lower_pipeline_layout_info, pipeline, layout,
+              &needs_default_sampler_state);
+
+   /* If in the end we didn't need to use the default sampler states and the
+    * shader doesn't need any other samplers, get rid of them so we can
+    * recognize that this program doesn't use any samplers at all.
+    */
+   if (!needs_default_sampler_state && maps->sampler_map.num_desc == 2)
+      maps->sampler_map.num_desc = 0;
 
    p_stage->feedback.duration += os_time_get_nano() - stage_start;
 }