Mesa (master): nir: Rewrite lower_undef_to_zero

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Module: Mesa
Branch: master
Commit: 783b895ec9fe15af6214de28e262e20f18ad4cf1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=783b895ec9fe15af6214de28e262e20f18ad4cf1

Author: Jason Ekstrand <jason at jlekstrand.net>
Date:   Tue Nov 17 17:45:22 2020 -0600

nir: Rewrite lower_undef_to_zero

This both fixes its metadata handling (it was flagging dirty regardless
of progress) and reduces the entire pass to 21 LOC including whitespace
by making better use of helpers.

Reviewed-by: Jesse Natalie <jenatali at microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7565>

---

 src/compiler/nir/nir_lower_undef_to_zero.c | 55 +++++++++---------------------
 1 file changed, 17 insertions(+), 38 deletions(-)

diff --git a/src/compiler/nir/nir_lower_undef_to_zero.c b/src/compiler/nir/nir_lower_undef_to_zero.c
index e75086b5097..9727d626ed8 100644
--- a/src/compiler/nir/nir_lower_undef_to_zero.c
+++ b/src/compiler/nir/nir_lower_undef_to_zero.c
@@ -40,45 +40,24 @@
 
 #include "nir_builder.h"
 
+static bool
+lower_undef_instr_to_zero(nir_builder *b, nir_instr *instr, UNUSED void *_state)
+{
+   if (instr->type != nir_instr_type_ssa_undef)
+      return false;
+
+   nir_ssa_undef_instr *und = nir_instr_as_ssa_undef(instr);
+   b->cursor = nir_instr_remove(&und->instr);
+   nir_ssa_def *zero = nir_imm_zero(b, und->def.num_components,
+                                       und->def.bit_size);
+   nir_ssa_def_rewrite_uses(&und->def, nir_src_for_ssa(zero));
+   return true;
+}
+
 bool
 nir_lower_undef_to_zero(nir_shader *shader)
 {
-   bool progress = false;
-
-   nir_foreach_function(function, shader) {
-      if (!function->impl) continue;
-
-      nir_builder b;
-      nir_builder_init(&b, function->impl);
-
-      nir_foreach_block(block, function->impl) {
-         nir_foreach_instr_safe(instr, block) {
-            if (instr->type != nir_instr_type_ssa_undef) continue;
-
-            nir_ssa_undef_instr *und = nir_instr_as_ssa_undef(instr);
-
-            /* Get the required size */
-            unsigned c = und->def.num_components;
-            unsigned s = und->def.bit_size;
-
-            nir_const_value v[NIR_MAX_VEC_COMPONENTS];
-            memset(v, 0, sizeof(v));
-
-            b.cursor = nir_before_instr(instr);
-            nir_ssa_def *zero = nir_build_imm(&b, c, s, v);
-            nir_src zerosrc = nir_src_for_ssa(zero);
-
-            nir_ssa_def_rewrite_uses(&und->def, zerosrc);
-
-            progress |= true;
-         }
-      }
-
-      nir_metadata_preserve(function->impl, nir_metadata_block_index | nir_metadata_dominance);
-
-   }
-
-   return progress;
+   return nir_shader_instructions_pass(shader, lower_undef_instr_to_zero,
+                                       nir_metadata_block_index |
+                                       nir_metadata_dominance, NULL);
 }
-
-