gallium: Add PIPE_CAP_CS_DERIVED_SYSTEM_VALUES_SUPPORTED

Tells whether or not the driver can handle gl_LocalInvocationIndex and
gl_GlobalInvocationID.  If not supported (the default), state tracker
will lower those on behalf of the driver.

v2: Add case to u_screen.c.  (Anholt)

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/gallium/auxiliary/util/u_screen.c

@@ -328,6 +328,7 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
    case PIPE_CAP_IMAGE_LOAD_FORMATTED:
    case PIPE_CAP_PREFER_COMPUTE_BLIT_FOR_MULTIMEDIA:
    case PIPE_CAP_FRAGMENT_SHADER_INTERLOCK:
+   case PIPE_CAP_CS_DERIVED_SYSTEM_VALUES_SUPPORTED:
       return 0;
 
    case PIPE_CAP_MAX_GS_INVOCATIONS:

src/gallium/docs/source/screen.rst

@@ -528,6 +528,9 @@ The integer capabilities:
   OpenMAX should use a compute-based blit instead of pipe_context::blit.
 * ``PIPE_CAP_FRAGMENT_SHADER_INTERLOCK``: True if fragment shader interlock
   functionality is supported.
+* ``PIPE_CAP_CS_DERIVED_SYSTEM_VALUES_SUPPORTED``: True if driver handles
+  gl_LocalInvocationIndex and gl_GlobalInvocationID.  Otherwise, state tracker will
+  lower those system values.
 
 .. _pipe_capf:
 

src/gallium/include/pipe/p_defines.h

@@ -885,6 +885,7 @@ enum pipe_cap
    PIPE_CAP_PREFER_COMPUTE_BLIT_FOR_MULTIMEDIA,
    PIPE_CAP_FRAGMENT_SHADER_INTERLOCK,
    PIPE_CAP_FBFETCH_COHERENT,
+   PIPE_CAP_CS_DERIVED_SYSTEM_VALUES_SUPPORTED,
 };
 
 /**

src/mesa/state_tracker/st_extensions.c

@@ -348,7 +348,8 @@ void st_init_limits(struct pipe_screen *screen,
       screen->get_param(screen, PIPE_CAP_GLSL_TESS_LEVELS_AS_INPUTS);
    c->LowerTessLevel =
       !screen->get_param(screen, PIPE_CAP_NIR_COMPACT_ARRAYS);
-   c->LowerCsDerivedVariables = true;
+   c->LowerCsDerivedVariables =
+      !screen->get_param(screen, PIPE_CAP_CS_DERIVED_SYSTEM_VALUES_SUPPORTED);
    c->PrimitiveRestartForPatches =
       screen->get_param(screen, PIPE_CAP_PRIMITIVE_RESTART_FOR_PATCHES);