nir: Add helpers for lazy var creation.

This should make writing some lowering/meta code easier.  It also keeps
the num_inputs/outputs updated, when sometimes passes forgot to do so (for
example, nir_lower_input_attachments updated for one of the two vars it
creates).  The names of the variables change in many cases, but it's
probably nicer to see "VERT_ATTRIB_POS" than "in_0" or whatever.

I've only converted mesa core (compiler and GL), not all the driver meta
code.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22809>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 05efa36aec1..1e35b6ae2fc 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -4044,6 +4044,19 @@ nir_variable *nir_local_variable_create(nir_function_impl *impl,
                                         const struct glsl_type *type,
                                         const char *name);
 
+/* Gets the variable for the given mode and location, creating it (with the given
+ * type) if necessary.
+ */
+nir_variable *
+nir_get_variable_with_location(nir_shader *shader, nir_variable_mode mode, int location,
+                               const struct glsl_type *type);
+
+/* Creates a variable for the given mode and location.
+ */
+nir_variable *
+nir_create_variable_with_location(nir_shader *shader, nir_variable_mode mode, int location,
+                                  const struct glsl_type *type);
+
 nir_variable *nir_find_variable_with_location(nir_shader *shader,
                                               nir_variable_mode mode,
                                               unsigned location);