compiler, nir: Add and set barrier metadata

Useful for determining whether certain optimizations are legal for a
compute shader (e.g. optimizing workgroup size in the driver).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6312>

src/compiler/shader_info.h

@@ -226,6 +226,10 @@ typedef struct shader_info {
    /* Whether gl_Layer is viewport-relative */
    bool layer_viewport_relative:1;
 
+   /* Whether explicit barriers are used */
+   bool uses_control_barrier : 1;
+   bool uses_memory_barrier : 1;
+
    union {
       struct {
          /* Which inputs are doubles */