nir/nir_lower_wrmasks: Use the nir_lower_instructions_pass() helper.

This fixes the invalidation of metadata when we didn't modify the shader
and unindents a bunch of code.

Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6412>

src/compiler/nir/nir_lower_wrmasks.c

@@ -179,53 +179,55 @@ split_wrmask(nir_builder *b, nir_intrinsic_instr *intr)
    nir_instr_remove(&intr->instr);
 }
 
-bool
+struct nir_lower_wrmasks_state {
-nir_lower_wrmasks(nir_shader *shader, nir_instr_filter_cb cb, const void *data)
+   nir_instr_filter_cb cb;
+   const void *data;
+};
+
+static bool
+nir_lower_wrmasks_instr(nir_builder *b, nir_instr *instr, void *data)
 {
-   bool progress = false;
+   struct nir_lower_wrmasks_state *state = data;
 
-   nir_foreach_function(function, shader) {
-      nir_function_impl *impl = function->impl;
-
-      if (!impl)
-         continue;
-
-      nir_foreach_block(block, impl) {
-         nir_foreach_instr_safe(instr, block) {
    if (instr->type != nir_instr_type_intrinsic)
-               continue;
+      return false;
 
    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 
    /* if no wrmask, then skip it: */
    if (!nir_intrinsic_has_write_mask(intr))
-               continue;
+      return false;
 
    /* if wrmask is already contiguous, then nothing to do: */
    if (nir_intrinsic_write_mask(intr) == BITFIELD_MASK(intr->num_components))
-               continue;
+      return false;
 
    /* do we know how to lower this instruction? */
    if (value_src(intr->intrinsic) < 0)
-               continue;
+      return false;
 
    assert(offset_src(intr->intrinsic) >= 0);
 
    /* does backend need us to lower this intrinsic? */
-            if (cb && !cb(instr, data))
+   if (state->cb && !state->cb(instr, state->data))
-               continue;
+      return false;
 
-            nir_builder b;
+   split_wrmask(b, intr);
-            nir_builder_init(&b, impl);
-            split_wrmask(&b, intr);
-            progress = true;
-         }
-      }
 
-      nir_metadata_preserve(impl, nir_metadata_block_index |
+   return true;
-                                  nir_metadata_dominance);
+}
-
+
-   }
+bool
-
+nir_lower_wrmasks(nir_shader *shader, nir_instr_filter_cb cb, const void *data)
-   return progress;
+{
+   struct nir_lower_wrmasks_state state = {
+      .cb = cb,
+      .data = data,
+   };
+
+   return nir_shader_instructions_pass(shader,
+                                       nir_lower_wrmasks_instr,
+                                       nir_metadata_block_index |
+                                       nir_metadata_dominance,
+                                       &state);
 }