nir: use nir_shader_instructions_pass in nir_lower_interpolation

Changes:
- nir_metadata_preserve(..., nir_metadata_block_index | nir_metadata_dominance)
  is called only when pass makes progress
- nir_metadata_preserve(..., nir_metadata_all) is called when pass doesn't
  make progress

Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12282>

src/compiler/nir/nir_lower_interpolation.c

@@ -35,19 +35,18 @@
 #include "nir_builder.h"
 
 static bool
-nir_lower_interpolation_block(nir_block *block, nir_builder *b,
+nir_lower_interpolation_instr(nir_builder *b, nir_instr *instr, void *cb_data)
-                              nir_lower_interpolation_options options)
 {
-   bool progress = false;
+   nir_lower_interpolation_options options =
+         *(nir_lower_interpolation_options *)cb_data;
 
-   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 (intr->intrinsic != nir_intrinsic_load_interpolated_input)
-         continue;
+      return false;
 
    assert(intr->dest.is_ssa);
    assert(intr->src[0].is_ssa);
@@ -58,7 +57,7 @@ nir_lower_interpolation_block(nir_block *block, nir_builder *b,
 
    /* Leave VARYING_SLOT_POS alone */
    if (nir_intrinsic_base(intr) == VARYING_SLOT_POS)
-         continue;
+      return false;
 
    const enum glsl_interp_mode interp_mode =
       nir_intrinsic_interp_mode(bary_intrinsic);
@@ -69,7 +68,7 @@ nir_lower_interpolation_block(nir_block *block, nir_builder *b,
    /* Only lower for inputs that need interpolation */
    if (interp_mode != INTERP_MODE_SMOOTH &&
        interp_mode != INTERP_MODE_NOPERSPECTIVE)
-         continue;
+      return false;
 
    nir_intrinsic_op op = bary_intrinsic->intrinsic;
 
@@ -77,25 +76,25 @@ nir_lower_interpolation_block(nir_block *block, nir_builder *b,
    case nir_intrinsic_load_barycentric_at_sample:
       if (options & nir_lower_interpolation_at_sample)
          break;
-         continue;
+      return false;
    case nir_intrinsic_load_barycentric_at_offset:
       if (options & nir_lower_interpolation_at_offset)
          break;
-         continue;
+      return false;
    case nir_intrinsic_load_barycentric_centroid:
       if (options & nir_lower_interpolation_centroid)
          break;
-         continue;
+      return false;
    case nir_intrinsic_load_barycentric_pixel:
       if (options & nir_lower_interpolation_pixel)
          break;
-         continue;
+      return false;
    case nir_intrinsic_load_barycentric_sample:
       if (options & nir_lower_interpolation_sample)
          break;
-         continue;
+      return false;
    default:
-         continue;
+      return false;
    }
 
    b->cursor = nir_before_instr(instr);
@@ -123,38 +122,14 @@ nir_lower_interpolation_block(nir_block *block, nir_builder *b,
    nir_ssa_def *vec = nir_vec(b, comps, intr->num_components);
    nir_ssa_def_rewrite_uses(&intr->dest.ssa, vec);
 
-      progress = true;
+   return true;
-   }
-
-   return progress;
-}
-
-static bool
-nir_lower_interpolation_impl(nir_function_impl *impl,
-                             nir_lower_interpolation_options options)
-{
-   bool progress = false;
-   nir_builder builder;
-   nir_builder_init(&builder, impl);
-
-   nir_foreach_block(block, impl) {
-      progress |= nir_lower_interpolation_block(block, &builder, options);
-   }
-
-   nir_metadata_preserve(impl, nir_metadata_block_index |
-                               nir_metadata_dominance);
-   return progress;
 }
 
 bool
 nir_lower_interpolation(nir_shader *shader, nir_lower_interpolation_options options)
 {
-   bool progress = false;
+   return nir_shader_instructions_pass(shader, nir_lower_interpolation_instr,
-
+                                       nir_metadata_block_index |
-   nir_foreach_function(function, shader) {
+                                       nir_metadata_dominance,
-      if (function->impl)
+                                       &options);
-         progress |= nir_lower_interpolation_impl(function->impl, options);
-   }
-
-   return progress;
 }