nir: Add a nir_foreach_uniform_variable helper

This one's a bit more complex because it filters off only those
variables with mode == nir_var_uniform.  As such, it's not exactly a
drop-in replacement for nir_foreach_variable(var, &nir->uniforms).

Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5966>

src/compiler/glsl/gl_nir_link_atomics.c

@@ -148,7 +148,7 @@ find_active_atomic_counters(struct gl_context *ctx,
 
       nir_shader *nir = sh->Program->nir;
 
-      nir_foreach_variable(var, &nir->uniforms) {
+      nir_foreach_uniform_variable(var, nir) {
          if (!glsl_contains_atomic(var->type))
             continue;
 

src/compiler/nir/nir.h

@@ -636,6 +636,14 @@ typedef struct nir_variable {
 #define nir_foreach_shader_out_variable_safe(var, shader) \
    nir_foreach_variable_safe(var, &(shader)->outputs)
 
+#define nir_foreach_uniform_variable(var, shader) \
+   nir_foreach_variable(var, &(shader)->uniforms) \
+      if (var->data.mode == nir_var_uniform)
+
+#define nir_foreach_uniform_variable_safe(var, shader) \
+   nir_foreach_variable_safe(var, &(shader)->uniforms) \
+      if (var->data.mode == nir_var_uniform)
+
 static inline bool
 nir_variable_is_global(const nir_variable *var)
 {

src/compiler/nir/nir_gather_info.c

@@ -601,7 +601,7 @@ nir_shader_gather_info(nir_shader *shader, nir_function_impl *entrypoint)
    shader->info.image_buffers = 0;
    shader->info.msaa_images = 0;
 
-   nir_foreach_variable(var, &shader->uniforms) {
+   nir_foreach_uniform_variable(var, shader) {
       /* Bindless textures and images don't use non-bindless slots.
        * Interface blocks imply inputs, outputs, UBO, or SSBO, which can only
        * mean bindless.

src/compiler/nir/nir_lower_atomics_to_ssbo.c

@@ -188,7 +188,7 @@ nir_lower_atomics_to_ssbo(nir_shader *shader)
    if (progress) {
       /* replace atomic_uint uniforms with ssbo's: */
       unsigned replaced = 0;
-      nir_foreach_variable_safe(var, &shader->uniforms) {
+      nir_foreach_uniform_variable_safe(var, shader) {
          if (is_atomic_uint(var->type)) {
             exec_node_remove(&var->node);