nir: Add gl_WorkGroupID system variable

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

src/glsl/nir/nir.c

@@ -1459,6 +1459,8 @@ 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_work_group_id:
+      return SYSTEM_VALUE_WORK_GROUP_ID;
    /* FINISHME: Add tessellation intrinsics.
       return SYSTEM_VALUE_TESS_COORD;
       return SYSTEM_VALUE_VERTICES_IN;

src/glsl/nir/nir_intrinsics.h

@@ -142,6 +142,7 @@ SYSTEM_VALUE(sample_pos, 2)
 SYSTEM_VALUE(sample_mask_in, 1)
 SYSTEM_VALUE(invocation_id, 1)
 SYSTEM_VALUE(local_invocation_id, 3)
+SYSTEM_VALUE(work_group_id, 3)
 
 /*
  * The format of the indices depends on the type of the load.  For uniforms,

src/glsl/nir/nir_lower_system_values.c

@@ -73,6 +73,9 @@ convert_instr(nir_intrinsic_instr *instr)
    case SYSTEM_VALUE_LOCAL_INVOCATION_ID:
       op = nir_intrinsic_load_local_invocation_id;
       break;
+   case SYSTEM_VALUE_WORK_GROUP_ID:
+      op = nir_intrinsic_load_work_group_id;
+      break;
    default:
       unreachable("not reached");
    }