nir: Add a nir_shader_preserve_all_metadata helper

There are some passes which really work on the shader level and it's
easier if we have a helper which preserves metadata on the whole shader.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5171>

src/compiler/nir/nir.h

@@ -3294,6 +3294,8 @@ nir_function_impl *nir_cf_node_get_function(nir_cf_node *node);
 void nir_metadata_require(nir_function_impl *impl, nir_metadata required, ...);
 /** dirties all but the preserved metadata */
 void nir_metadata_preserve(nir_function_impl *impl, nir_metadata preserved);
+/** Preserves all metadata for the given shader */
+void nir_shader_preserve_all_metadata(nir_shader *shader);
 
 /** creates an instruction with default swizzle/writemask/etc. with NULL registers */
 nir_alu_instr *nir_alu_instr_create(nir_shader *shader, nir_op op);

src/compiler/nir/nir_metadata.c

@@ -59,6 +59,15 @@ nir_metadata_preserve(nir_function_impl *impl, nir_metadata preserved)
    impl->valid_metadata &= preserved;
 }
 
+void
+nir_shader_preserve_all_metadata(nir_shader *shader)
+{
+   nir_foreach_function(function, shader) {
+      if (function->impl)
+         nir_metadata_preserve(function->impl, nir_metadata_all);
+   }
+}
+
 #ifndef NDEBUG
 /**
  * Make sure passes properly invalidate metadata (part 1).