GUFA: Mutable exported globals are roots (#4935)

Such globals can be written to from the outside, so we cannot infer anything about
their contents.

Fixes #4932

1 files changed, 7 insertions, 0 deletions

diff --git a/src/ir/possible-contents.cpp b/src/ir/possible-contents.cpp
index d9c608bda..f1302b3dd 100644
--- a/src/ir/possible-contents.cpp
+++ b/src/ir/possible-contents.cpp
@@ -1234,6 +1234,13 @@ Flower::Flower(Module& wasm) : wasm(wasm) {
           }
         }
       }
+    } else if (ex->kind == ExternalKind::Global) {
+      // Exported mutable globals are roots, since the outside may write any
+      // value to them.
+      auto name = ex->value;
+      if (wasm.getGlobal(name)->mutable_) {
+        roots[GlobalLocation{name}] = PossibleContents::many();
+      }
     }
   }