spirv2dxil: Support passing first vertex / base instance to DXIL backend

These values now have 3 modes of operation so switch from a bool to an enum:
1. Zero
2. Native DXIL sysvals
3. "Runtime data" via a constant buffer or root constants

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28383>

src/microsoft/spirv_to_dxil/dxil_spirv_nir.c

@@ -213,6 +213,8 @@ lower_shader_system_values(struct nir_builder *builder, nir_instr *instr,
          offsetof(struct dxil_spirv_compute_runtime_data, base_group_x);
       break;
    case nir_intrinsic_load_first_vertex:
+      if (conf->first_vertex_and_base_instance_mode == DXIL_SPIRV_SYSVAL_TYPE_NATIVE)
+         return false;
       offset = offsetof(struct dxil_spirv_vertex_runtime_data, first_vertex);
       break;
    case nir_intrinsic_load_is_indexed_draw:
@@ -220,6 +222,8 @@ lower_shader_system_values(struct nir_builder *builder, nir_instr *instr,
          offsetof(struct dxil_spirv_vertex_runtime_data, is_indexed_draw);
       break;
    case nir_intrinsic_load_base_instance:
+      if (conf->first_vertex_and_base_instance_mode == DXIL_SPIRV_SYSVAL_TYPE_NATIVE)
+         return false;
       offset = offsetof(struct dxil_spirv_vertex_runtime_data, base_instance);
       break;
    case nir_intrinsic_load_draw_id:
@@ -887,7 +891,7 @@ dxil_spirv_nir_passes(nir_shader *nir,
    NIR_PASS_V(nir, nir_lower_system_values);
 
    nir_lower_compute_system_values_options compute_options = {
-      .has_base_workgroup_id = !conf->zero_based_compute_workgroup_id,
+      .has_base_workgroup_id = conf->workgroup_id_mode != DXIL_SPIRV_SYSVAL_TYPE_ZERO,
    };
    NIR_PASS_V(nir, nir_lower_compute_system_values, &compute_options);
    NIR_PASS_V(nir, dxil_nir_lower_subgroup_id);
@@ -917,7 +921,7 @@ dxil_spirv_nir_passes(nir_shader *nir,
       nir->info.fs.uses_sample_shading = true;
    }
 
-   if (conf->zero_based_vertex_instance_id) {
+   if (conf->first_vertex_and_base_instance_mode == DXIL_SPIRV_SYSVAL_TYPE_ZERO) {
       // vertex_id and instance_id should have already been transformed to
       // base zero before spirv_to_dxil was called. Therefore, we can zero out
       // base/firstVertex/Instance.

src/microsoft/spirv_to_dxil/spirv2dxil.c

@@ -182,7 +182,7 @@ main(int argc, char **argv)
    conf.runtime_data_cbv.register_space = 31;
    conf.push_constant_cbv.base_shader_register = 0;
    conf.push_constant_cbv.register_space = 30;
-   conf.zero_based_vertex_instance_id = true;
+   conf.first_vertex_and_base_instance_mode = DXIL_SPIRV_SYSVAL_TYPE_ZERO;
    conf.declared_read_only_images_as_srvs = true;
    conf.shader_model_max = SHADER_MODEL_6_2;
 
@@ -218,6 +218,8 @@ main(int argc, char **argv)
          break;
       case 'm':
          conf.shader_model_max = SHADER_MODEL_6_0 + atoi(optarg);
+         conf.first_vertex_and_base_instance_mode = conf.shader_model_max >= SHADER_MODEL_6_8 ?
+            DXIL_SPIRV_SYSVAL_TYPE_NATIVE : DXIL_SPIRV_SYSVAL_TYPE_ZERO;
          break;
       case 'x':
          val_ver = DXIL_VALIDATOR_1_0 + atoi(optarg);

src/microsoft/spirv_to_dxil/spirv_to_dxil.c

@@ -69,7 +69,7 @@ spirv_to_dxil(const uint32_t *words, size_t word_count,
    dxil_get_nir_compiler_options(&nir_options, conf->shader_model_max, supported_bit_sizes, supported_bit_sizes);
    // We will manually handle base_vertex when vertex_id and instance_id have
    // have been already converted to zero-base.
-   nir_options.lower_base_vertex = !conf->zero_based_vertex_instance_id;
+   nir_options.lower_base_vertex = conf->first_vertex_and_base_instance_mode != DXIL_SPIRV_SYSVAL_TYPE_ZERO;
 
    nir_shader *nir = spirv_to_nir(
       words, word_count, (struct nir_spirv_specialization *)specializations,

src/microsoft/spirv_to_dxil/spirv_to_dxil.h

@@ -141,6 +141,16 @@ enum dxil_spirv_yz_flip_mode {
 
 #define DXIL_SPIRV_MAX_VIEWPORT 16
 
+enum dxil_spirv_sysval_type {
+   // The sysval can be inlined in the shader as a constant zero
+   DXIL_SPIRV_SYSVAL_TYPE_ZERO,
+   // The sysval has a supported DXIL equivalent
+   DXIL_SPIRV_SYSVAL_TYPE_NATIVE,
+   // The sysval might be nonzero and has no DXIL equivalent, so it
+   // will need to be provided by the runtime_data constant buffer
+   DXIL_SPIRV_SYSVAL_TYPE_RUNTIME_DATA,
+};
+
 struct dxil_spirv_runtime_conf {
    struct {
       uint32_t register_space;
@@ -152,11 +162,8 @@ struct dxil_spirv_runtime_conf {
       uint32_t base_shader_register;
    } push_constant_cbv;
 
-   // Set true if vertex and instance ids have already been converted to
-   // zero-based. Otherwise, runtime_data will be required to lower them.
-   bool zero_based_vertex_instance_id;
-   // Set true if workgroup base is known to be zero
-   bool zero_based_compute_workgroup_id;
+   enum dxil_spirv_sysval_type first_vertex_and_base_instance_mode;
+   enum dxil_spirv_sysval_type workgroup_id_mode;
 
    struct {
       // mode != DXIL_SPIRV_YZ_FLIP_NONE only valid on vertex/geometry stages.

src/microsoft/vulkan/dzn_pipeline.c

@@ -238,8 +238,8 @@ dzn_pipeline_get_nir_shader(struct dzn_device *device,
          .register_space = DZN_REGISTER_SPACE_PUSH_CONSTANT,
          .base_shader_register = 0,
       },
-      .zero_based_vertex_instance_id = false,
-      .zero_based_compute_workgroup_id = false,
+      .first_vertex_and_base_instance_mode = DXIL_SPIRV_SYSVAL_TYPE_RUNTIME_DATA,
+      .workgroup_id_mode = DXIL_SPIRV_SYSVAL_TYPE_RUNTIME_DATA,
       .yz_flip = {
          .mode = options->yz_flip_mode,
          .y_mask = options->y_flip_mask,