nir/lower_shader_calls: reobtain impl after NIR_PASS

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37573>

src/compiler/nir/nir_lower_shader_calls.c

@@ -1993,6 +1993,11 @@ nir_lower_shader_calls(nir_shader *shader,
       bool progress = false;
       NIR_PASS(progress, shader, wrap_instrs, instr_is_shader_call);
 
+      /* NIR_PASS might recreate the function_impl when NIR_DEBUG=serialize or
+       * NIR_DEBUG=clone is used.
+       */
+      impl = nir_shader_get_entrypoint(shader);
+
       nir_rematerialize_derefs_in_use_blocks_impl(impl);
 
       if (progress)