From 5df39e3bbddaefcb0d0c4d1f10412c508b120aca Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 9 Aug 2022 09:49:04 -0700
Subject: RedundantSetElimination: ReFinalize when needed (#4877)

---
 src/passes/RedundantSetElimination.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'src')

diff --git a/src/passes/RedundantSetElimination.cpp b/src/passes/RedundantSetElimination.cpp
index 90925edf2..0b4cad056 100644
--- a/src/passes/RedundantSetElimination.cpp
+++ b/src/passes/RedundantSetElimination.cpp
@@ -67,6 +67,9 @@ struct RedundantSetElimination
 
   Index numLocals;
 
+  // In rare cases we make a change to a type that requires a refinalize.
+  bool refinalize = false;
+
   // cfg traversal work
 
   static void doVisitLocalSet(RedundantSetElimination* self,
@@ -94,6 +97,10 @@ struct RedundantSetElimination
     flowValues(func);
     // remove redundant sets
     optimize();
+
+    if (refinalize) {
+      ReFinalize().walkFunctionInModule(func, this->getModule());
+    }
   }
 
   // Use a value numbering for the values of expressions.
@@ -346,6 +353,20 @@ struct RedundantSetElimination
       drop->value = value;
       drop->finalize();
     } else {
+      // If we are replacing the set with something of a more specific type,
+      // then we need to refinalize, for example:
+      //
+      //  (struct.get $X 0
+      //    (local.tee $x
+      //      (..something of type $Y, a subtype of $X..)
+      //    )
+      //  )
+      //
+      // After the replacement the struct.get will read from $Y, whose field may
+      // have a more refined type.
+      if (value->type != set->type) {
+        refinalize = true;
+      }
       *setp = value;
     }
   }
-- 
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