Mesa (main): spirv: Create PRIMITIVE_INDICES for NV_mesh_shader on-demand.

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Module: Mesa
Branch: main
Commit: e6cfd1ed6421c6abcf1893802ae55562fde45d20
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e6cfd1ed6421c6abcf1893802ae55562fde45d20

Author: Timur Kristóf <timur.kristof at gmail.com>
Date:   Thu Feb 10 23:52:04 2022 +0100

spirv: Create PRIMITIVE_INDICES for NV_mesh_shader on-demand.

The shader can have SpvOpWritePackedPrimitiveIndices4x8NV while the
output variable may not exist. This seems to be a defect in the
NV_mesh_shader SPIR-V spec, let's work around it by creating the
variable on-demand.

Signed-off-by: Timur Kristóf <timur.kristof at gmail.com>
Reviewed-by: Marcin Ślusarz <marcin.slusarz at intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15005>

---

 src/compiler/spirv/spirv_to_nir.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/compiler/spirv/spirv_to_nir.c b/src/compiler/spirv/spirv_to_nir.c
index 79e176a2218..f0461d8f612 100644
--- a/src/compiler/spirv/spirv_to_nir.c
+++ b/src/compiler/spirv/spirv_to_nir.c
@@ -5604,13 +5604,27 @@ vtn_handle_write_packed_primitive_indices(struct vtn_builder *b, SpvOp opcode,
       }
    }
 
-   /* TODO(mesh): It may be the case that the variable is not present in the
+   /* It may be the case that the variable is not present in the
     * entry point interface list.
     *
     * See https://github.com/KhronosGroup/SPIRV-Registry/issues/104.
     */
-   vtn_fail_if(indices == NULL,
-               "Missing output variable decorated with PrimitiveIndices builtin.");
+
+   if (!indices) {
+      unsigned vertices_per_prim =
+         num_mesh_vertices_per_primitive(b->shader->info.mesh.primitive_type);
+      unsigned max_prim_indices =
+         vertices_per_prim * b->shader->info.mesh.max_primitives_out;
+      const struct glsl_type *t =
+         glsl_array_type(glsl_uint_type(), max_prim_indices, 0);
+      nir_variable *var =
+         nir_variable_create(b->shader, nir_var_shader_out, t,
+                             "gl_PrimitiveIndicesNV");
+
+      var->data.location = VARYING_SLOT_PRIMITIVE_INDICES;
+      var->data.interpolation = INTERP_MODE_NONE;
+      indices = nir_build_deref_var(&b->nb, var);
+   }
 
    nir_ssa_def *offset = vtn_get_nir_ssa(b, w[1]);
    nir_ssa_def *packed = vtn_get_nir_ssa(b, w[2]);
@@ -5619,7 +5633,7 @@ vtn_handle_write_packed_primitive_indices(struct vtn_builder *b, SpvOp opcode,
       nir_deref_instr *offset_deref =
          nir_build_deref_array(&b->nb, indices,
                                nir_iadd_imm(&b->nb, offset, i));
-      nir_ssa_def *val = nir_u2u(&b->nb, nir_channel(&b->nb, unpacked, i), 32);
+      nir_ssa_def *val = nir_u2u32(&b->nb, nir_channel(&b->nb, unpacked, i));
 
       nir_store_deref(&b->nb, offset_deref, val, 0x1);
    }