nir: Make lowering gl_LocalInvocationIndex optional

Cc: "12.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.c

@@ -1752,6 +1752,8 @@ nir_intrinsic_from_system_value(gl_system_value val)
       return nir_intrinsic_load_sample_mask_in;
    case SYSTEM_VALUE_LOCAL_INVOCATION_ID:
       return nir_intrinsic_load_local_invocation_id;
+   case SYSTEM_VALUE_LOCAL_INVOCATION_INDEX:
+      return nir_intrinsic_load_local_invocation_index;
    case SYSTEM_VALUE_WORK_GROUP_ID:
       return nir_intrinsic_load_work_group_id;
    case SYSTEM_VALUE_NUM_WORK_GROUPS:
@@ -1801,6 +1803,8 @@ nir_system_value_from_intrinsic(nir_intrinsic_op intrin)
       return SYSTEM_VALUE_SAMPLE_MASK_IN;
    case nir_intrinsic_load_local_invocation_id:
       return SYSTEM_VALUE_LOCAL_INVOCATION_ID;
+   case nir_intrinsic_load_local_invocation_index:
+      return SYSTEM_VALUE_LOCAL_INVOCATION_INDEX;
    case nir_intrinsic_load_num_work_groups:
       return SYSTEM_VALUE_NUM_WORK_GROUPS;
    case nir_intrinsic_load_work_group_id:

src/compiler/nir/nir.h

@@ -1682,6 +1682,8 @@ typedef struct nir_shader_compiler_options {
 
    /* Indicates that the driver only has zero-based vertex id */
    bool vertex_id_zero_based;
+
+   bool lower_cs_local_index_from_id;
 } nir_shader_compiler_options;
 
 typedef struct nir_shader_info {

src/compiler/nir/nir_gather_info.c

@@ -44,6 +44,7 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader)
    case nir_intrinsic_load_primitive_id:
    case nir_intrinsic_load_invocation_id:
    case nir_intrinsic_load_local_invocation_id:
+   case nir_intrinsic_load_local_invocation_index:
    case nir_intrinsic_load_work_group_id:
    case nir_intrinsic_load_num_work_groups:
       shader->info.system_values_read |=

src/compiler/nir/nir_intrinsics.h

@@ -299,6 +299,7 @@ SYSTEM_VALUE(tess_level_outer, 4, 0, xx, xx, xx)
 SYSTEM_VALUE(tess_level_inner, 2, 0, xx, xx, xx)
 SYSTEM_VALUE(patch_vertices_in, 1, 0, xx, xx, xx)
 SYSTEM_VALUE(local_invocation_id, 3, 0, xx, xx, xx)
+SYSTEM_VALUE(local_invocation_index, 1, 0, xx, xx, xx)
 SYSTEM_VALUE(work_group_id, 3, 0, xx, xx, xx)
 SYSTEM_VALUE(user_clip_plane, 4, 1, UCP_ID, xx, xx)
 SYSTEM_VALUE(num_work_groups, 3, 0, xx, xx, xx)

src/compiler/nir/nir_lower_system_values.c

@@ -48,7 +48,7 @@ convert_block(nir_block *block, nir_builder *b)
 
       b->cursor = nir_after_instr(&load_var->instr);
 
-      nir_ssa_def *sysval;
+      nir_ssa_def *sysval = NULL;
       switch (var->data.location) {
       case SYSTEM_VALUE_GLOBAL_INVOCATION_ID: {
          /* From the GLSL man page for gl_GlobalInvocationID:
@@ -74,6 +74,12 @@ convert_block(nir_block *block, nir_builder *b)
       }
 
       case SYSTEM_VALUE_LOCAL_INVOCATION_INDEX: {
+         /* If lower_cs_local_index_from_id is true, then we derive the local
+          * index from the local id.
+          */
+         if (!b->shader->options->lower_cs_local_index_from_id)
+            break;
+
          /* From the GLSL man page for gl_LocalInvocationIndex:
           *
           *    "The value of gl_LocalInvocationIndex is equal to
@@ -111,12 +117,14 @@ convert_block(nir_block *block, nir_builder *b)
             nir_load_system_value(b, nir_intrinsic_load_base_instance, 0));
          break;
 
-      default: {
+      default:
+         break;
+      }
+
+      if (sysval == NULL) {
          nir_intrinsic_op sysval_op =
             nir_intrinsic_from_system_value(var->data.location);
          sysval = nir_load_system_value(b, sysval_op, 0);
-         break;
-      } /* default */
       }
 
       nir_ssa_def_rewrite_uses(&load_var->dest.ssa, nir_src_for_ssa(sysval));

src/mesa/drivers/dri/i965/brw_compiler.c

@@ -40,7 +40,8 @@
    .lower_fdiv = true,                                                        \
    .lower_flrp64 = true,                                                      \
    .native_integers = true,                                                   \
-   .vertex_id_zero_based = true
+   .vertex_id_zero_based = true,                                              \
+   .lower_cs_local_index_from_id = true
 
 static const struct nir_shader_compiler_options scalar_nir_options = {
    COMMON_OPTIONS,