Fix br_on_exn handling in ReFinalize (#2854)

In `ReFinalize`'s branch handling, `updateBreakValueType` is supposed to
be executed only when the branch itself is not replaced with its
argument (because it is guaranteed not to be taken).

Also this moves `visitBrOnExn` from `RuntimeExpressionRunner` to its
base class `ExpressionRunner`, because it does not depend on anything on
the runtime instance to work. This is effectively NFC for now because
`visitTry` is still only implemented only in `RuntimeExpressionRunner`
because it relies on multivalue handling of it, and without it we cannot
create a valid exception `Literal`.

1 files changed, 18 insertions, 23 deletions

diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 257a0670f..b0118231e 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -1270,7 +1270,24 @@ public:
     throwException(flow.getSingleValue());
     WASM_UNREACHABLE("rethrow");
   }
-  Flow visitBrOnExn(BrOnExn* curr) { WASM_UNREACHABLE("unimp"); }
+  Flow visitBrOnExn(BrOnExn* curr) {
+    NOTE_ENTER("BrOnExn");
+    Flow flow = this->visit(curr->exnref);
+    if (flow.breaking()) {
+      return flow;
+    }
+    if (flow.getType() == Type::nullref) {
+      trap("br_on_exn: argument is null");
+    }
+    const ExceptionPackage& ex = flow.getSingleValue().getExceptionPackage();
+    if (curr->event != ex.event) { // Not taken
+      return flow;
+    }
+    // Taken
+    flow.values = ex.values;
+    flow.breakTo = curr->name;
+    return flow;
+  }
 
   virtual void trap(const char* why) { WASM_UNREACHABLE("unimp"); }
 
@@ -1514,10 +1531,6 @@ public:
     NOTE_ENTER("Try");
     return Flow(NONCONSTANT_FLOW);
   }
-  Flow visitBrOnExn(BrOnExn* curr) {
-    NOTE_ENTER("BrOnExn");
-    return Flow(NONCONSTANT_FLOW);
-  }
 
   void trap(const char* why) override { throw NonconstantException(); }
 
@@ -2410,24 +2423,6 @@ private:
         return this->visit(curr->catchBody);
       }
     }
-    Flow visitBrOnExn(BrOnExn* curr) {
-      NOTE_ENTER("BrOnExn");
-      Flow flow = this->visit(curr->exnref);
-      if (flow.breaking()) {
-        return flow;
-      }
-      if (flow.getType() == Type::nullref) {
-        trap("br_on_exn: argument is null");
-      }
-      const ExceptionPackage& ex = flow.getSingleValue().getExceptionPackage();
-      if (curr->event != ex.event) { // Not taken
-        return flow;
-      }
-      // Taken
-      flow.values = ex.values;
-      flow.breakTo = curr->name;
-      return flow;
-    }
     Flow visitPush(Push* curr) {
       NOTE_ENTER("Push");
       Flow value = this->visit(curr->value);