glsl: teach std140_base_alignment about samplers

These functions are about to be used more aggressively for determining
uniform layout. Samplers may be inside of structs, and it's easier to
reuse the existing base alignment logic.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/glsl/glsl_types.cpp

@@ -1077,6 +1077,15 @@ glsl_type::std140_base_alignment(bool row_major) const
       return base_alignment;
    }
 
+   /* A sampler may never occur in a UBO (without bindless of some sort),
+    * however it is convenient to use this alignment function even with
+    * regular uniforms. This allows use of this function on uniform structs
+    * that contain samplers.
+    */
+   if (this->is_sampler()) {
+      return 0;
+   }
+
    assert(!"not reached");
    return -1;
 }