nir/spirv: Add support for device groups

Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>

src/compiler/nir/nir.h

@@ -1888,6 +1888,8 @@ typedef struct nir_shader_compiler_options {
 
    bool lower_cs_local_index_from_id;
 
+   bool lower_device_index_to_zero;
+
    /**
     * Should nir_lower_io() create load_interpolated_input intrinsics?
     *

src/compiler/nir/nir_lower_system_values.c

@@ -133,6 +133,11 @@ convert_block(nir_block *block, nir_builder *b)
          break;
       }
 
+      case SYSTEM_VALUE_DEVICE_INDEX:
+         if (b->shader->options->lower_device_index_to_zero)
+            sysval = nir_imm_int(b, 0);
+         break;
+
       default:
          break;
       }