glsl: add gl_LocalGroupSizeARB as a system value

v2: - only add it if the ext is enabled (Ilia)

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/compiler/glsl/builtin_variables.cpp

@@ -1249,6 +1249,12 @@ builtin_variable_generator::generate_cs_special_vars()
                     "gl_LocalInvocationID");
    add_system_value(SYSTEM_VALUE_WORK_GROUP_ID, uvec3_t, "gl_WorkGroupID");
    add_system_value(SYSTEM_VALUE_NUM_WORK_GROUPS, uvec3_t, "gl_NumWorkGroups");
+
+   if (state->ARB_compute_variable_group_size_enable) {
+      add_system_value(SYSTEM_VALUE_LOCAL_GROUP_SIZE,
+                       uvec3_t, "gl_LocalGroupSizeARB");
+   }
+
    if (state->ctx->Const.LowerCsDerivedVariables) {
       add_variable("gl_GlobalInvocationID", uvec3_t, ir_var_auto, 0);
       add_variable("gl_LocalInvocationIndex", uint_t, ir_var_auto, 0);

src/compiler/shader_enums.h

@@ -472,6 +472,7 @@ typedef enum
    SYSTEM_VALUE_GLOBAL_INVOCATION_ID,
    SYSTEM_VALUE_WORK_GROUP_ID,
    SYSTEM_VALUE_NUM_WORK_GROUPS,
+   SYSTEM_VALUE_LOCAL_GROUP_SIZE,
    /*@}*/
 
    /**