From 79f6c73c565ab5f3c6f71bdb7f3ba57ad1fd8615 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 22 May 2026 21:32:19 -0700
Subject: [PATCH] Fix refinalization for --gufa-cast-all

In #8747 we refactored GUFA's `replaceCurrent` to set `optimized = true` and removed the now-redundant `optimized = true` at all the call sites. But we were too aggressive and removed an `optimized = true` in `Adder`, which had a separate `replaceCurrent` that did not set `optimized = true`. This caused a regression where we no longer refinalized after adding casts, but the regression was not caught by any tests.

Fix the bug and add a test that depends on refinalization after adding casts.
---
 src/passes/GUFA.cpp                |  1 +
 test/lit/passes/gufa-cast-all.wast | 41 ++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/src/passes/GUFA.cpp b/src/passes/GUFA.cpp
index addba6b7ee3..533c033524e 100644
--- a/src/passes/GUFA.cpp
+++ b/src/passes/GUFA.cpp
@@ -388,6 +388,7 @@ struct GUFAOptimizer
         if (oracleType.isRef() && oracleType != curr->type &&
             Type::isSubType(oracleType, curr->type)) {
           replaceCurrent(Builder(*getModule()).makeRefCast(curr, oracleType));
+          optimized = true;
         }
       }
     };
diff --git a/test/lit/passes/gufa-cast-all.wast b/test/lit/passes/gufa-cast-all.wast
index bffd88e7714..a1675982f08 100644
--- a/test/lit/passes/gufa-cast-all.wast
+++ b/test/lit/passes/gufa-cast-all.wast
@@ -454,3 +454,44 @@
     )
   )
 )
+
+(module
+  ;; CHECK:      (type $struct (struct))
+  (type $struct (struct))
+
+  ;; CHECK:      (type $1 (func (result (ref $struct))))
+
+  ;; CHECK:      (global $g (mut (ref null $struct)) (struct.new_default $struct))
+  (global $g (mut (ref null $struct)) (struct.new $struct))
+
+  ;; CHECK:      (func $test (type $1) (result (ref $struct))
+  ;; CHECK-NEXT:  (ref.cast (ref (exact $struct))
+  ;; CHECK-NEXT:   (block $block (result (ref (exact $struct)))
+  ;; CHECK-NEXT:    (drop
+  ;; CHECK-NEXT:     (ref.cast (ref (exact $struct))
+  ;; CHECK-NEXT:      (br_on_cast $block (ref (exact $struct)) (ref (exact $struct))
+  ;; CHECK-NEXT:       (ref.cast (ref (exact $struct))
+  ;; CHECK-NEXT:        (global.get $g)
+  ;; CHECK-NEXT:       )
+  ;; CHECK-NEXT:      )
+  ;; CHECK-NEXT:     )
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (unreachable)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $test (result (ref $struct))
+    (block $block (result (ref $struct))
+      (drop
+        (br_on_cast $block (ref null $struct) (ref $struct)
+          ;; This will be cast to (ref (exact $struct)). We must refinalize to
+          ;; update the br_on_cast output to (ref (exact $struct)) as well to
+          ;; maintain the validation condition that the cast output is a subtype
+          ;; of its input.
+          (global.get $g)
+        )
+      )
+      (unreachable)
+    )
+  )
+)