# UNDF: UNDF-2026-000000170
--- a/src/amd/compiler/aco_register_allocation.cpp
+++ b/src/amd/compiler/aco_register_allocation.cpp
@@ -998,6 +998,14 @@ update_renames(ra_ctx& ctx, RegisterFile& reg_file, std::vector<parallelcopy>& p
                bool never_rename = false)
 {
+   /* Build a tempId→index map for O(1) lookup of "did we already move a
+    * definition with this temp ID?".  Maintained incrementally as entries
+    * are erased below.
+    */
+   std::unordered_map<uint32_t, size_t> def_temp_idx;
+   for (size_t i = 0; i < parallelcopies.size(); i++) {
+      if (parallelcopies[i].def.isTemp())
+         def_temp_idx[parallelcopies[i].def.getTemp().id()] = i;
+   }
+
    /* clear operands */
    if (clear_operands) {
       for (parallelcopy& copy : parallelcopies) {
@@ -1056,10 +1064,16 @@ update_renames(ra_ctx& ctx, RegisterFile& reg_file, std::vector<parallelcopy>& p
       /* Check if we moved another parallelcopy definition. */
-      auto other = std::find_if(parallelcopies.begin(), parallelcopies.end(), [&](parallelcopy& c)
-                                { return c.def.isTemp() && it->op.getTemp() == c.def.getTemp(); });
+      auto map_it = def_temp_idx.find(it->op.getTemp().id());
+      auto other = (map_it != def_temp_idx.end())
+                   ? parallelcopies.begin() + map_it->second
+                   : parallelcopies.end();
       if (other != parallelcopies.end())
          it->op = other->op;

@@ -1077,6 +1091,12 @@ update_renames(ra_ctx& ctx, RegisterFile& reg_file, std::vector<parallelcopy>& p
       if (!is_copy_kill && other != parallelcopies.end()) {
          if (renamed_all) {
             assert(other < it);
+            /* Remove erased entry from the index map. */
+            if (other->def.isTemp())
+               def_temp_idx.erase(other->def.getTemp().id());
             it = parallelcopies.erase(other);
+            /* Rebuild indices after erase — entries after `other` shifted. */
+            for (size_t i = std::distance(parallelcopies.begin(), it); i < parallelcopies.size(); i++)
+               if (parallelcopies[i].def.isTemp())
+                  def_temp_idx[parallelcopies[i].def.getTemp().id()] = i;
          } else if (other->copy_kill < 0 && !never_rename) {