1 files changed, 22 insertions, 7 deletions
diff --git a/src/passes/CodeFolding.cpp b/src/passes/CodeFolding.cpp
index 70a357bbf..10255a670 100644
--- a/src/passes/CodeFolding.cpp
+++ b/src/passes/CodeFolding.cpp
@@ -304,13 +304,28 @@ private:
         // anything exiting that is in all targets is something bad
         return false;
       }
-      // Currently pop instructions are only used for exnref.pop, which is a
-      // pseudo instruction following a catch. We check if the current
-      // expression has a pop child. This can be overly conservative, because
-      // this can also exclude whole try-catches that contain a pop within them.
-      if (getModule()->features.hasExceptionHandling() &&
-          !FindAll<Pop>(item).list.empty()) {
-        return false;
+      if (getModule()->features.hasExceptionHandling()) {
+        // Currently pop instructions are only used for exnref.pop, which is a
+        // pseudo instruction following a catch. We check if the current
+        // expression has a pop child. This can be overly conservative, because
+        // this can also exclude whole try-catches that contain a pop within
+        // them.
+        if (!FindAll<Pop>(item).list.empty()) {
+          return false;
+        }
+        // When an expression can throw and it is within a try scope, taking it
+        // out of the try scope changes the program's behavior, because the
+        // expression that would otherwise have been caught by the try now
+        // throws up to the next try scope or even up to the caller. We restrict
+        // the move if 'outOf' contains a 'try' anywhere in it. This is a
+        // conservative approximation because there can be cases that 'try' is
+        // within the expression that may throw so it is safe to take the
+        // expression out.
+        if (EffectAnalyzer(getPassOptions(), getModule()->features, item)
+              .throws &&
+            !FindAll<Try>(outOf).list.empty()) {
+          return false;
+        }
       }
     }
     return true;