diff --git a/src/puya/ir/models.py b/src/puya/ir/models.py
index f38db39e0..5963f3238 100644
--- a/src/puya/ir/models.py
+++ b/src/puya/ir/models.py
@@ -1,7 +1,7 @@
 import abc
 import typing
 import typing as t
-from collections.abc import Iterable, Iterator, Mapping, Sequence
+from collections.abc import Iterable, Iterator, Mapping, Sequence, Set
 
 import attrs
 from immutabledict import immutabledict
@@ -823,7 +823,7 @@ def _check_blocks(self, _attribute: object, body: list[BasicBlock]) -> None:
                         f" for phi node {phi}",
                         self.source_location,
                     )
-        used_registers = frozenset(_get_used_registers(body))
+        used_registers = _get_used_registers(body)
         defined_registers = frozenset(self.parameters) | frozenset(_get_assigned_registers(body))
         bad_reads = used_registers - defined_registers
         if bad_reads:
@@ -867,25 +867,14 @@ def _get_assigned_registers(blocks: Sequence[BasicBlock]) -> Iterator[Register]:
                 yield from op.targets
 
 
-def _get_used_registers(blocks: Sequence[BasicBlock]) -> Iterator[Register]:
-    # TODO: replace with visitor
+def _get_used_registers(blocks: Sequence[BasicBlock]) -> Set[Register]:
+    from puya.ir.register_read_collector import RegisterReadCollector
+
+    collector = RegisterReadCollector()
     for block in blocks:
-        for phi in block.phis:
-            yield from (arg.value for arg in phi.args)
-        for op in block.ops:
-            match op:
-                case (
-                    Assignment(
-                        source=Intrinsic(args=args)
-                        | Assignment(source=ValueTuple(values=args))
-                        | InvokeSubroutine(args=args)
-                    )
-                    | Intrinsic(args=args)
-                    | InvokeSubroutine(args=args)
-                ):
-                    yield from (arg for arg in args if isinstance(arg, Register))
-                case Assignment(source=Register() as reg):
-                    yield reg
+        for op in block.all_ops:
+            op.accept(collector)
+    return collector.used_registers
 
 
 @attrs.define(kw_only=True, eq=False)