From cd0cae2fd1b0c765b90bc51f87025bb11196c6c4 Mon Sep 17 00:00:00 2001
From: Hideto Ueno <uenoku.tokotoko@gmail.com>
Date: Tue, 24 Jan 2023 23:11:42 +0900
Subject: [PATCH] [LowerTypes] Fix a race condition (#4582)

This PR fixes a race condition in LowerTypes with aggregate preservation mode. In the instance op lowering, linkage of referenced module is checked, however it is not allowed to read attributes from different threads.
---
 lib/Dialect/FIRRTL/Transforms/LowerTypes.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/Dialect/FIRRTL/Transforms/LowerTypes.cpp b/lib/Dialect/FIRRTL/Transforms/LowerTypes.cpp
index ffae4b702005..2da968cbfc1c 100644
--- a/lib/Dialect/FIRRTL/Transforms/LowerTypes.cpp
+++ b/lib/Dialect/FIRRTL/Transforms/LowerTypes.cpp
@@ -451,8 +451,12 @@ TypeLoweringVisitor::getPreservatinoModeForModule(FModuleLike module) {
   // We cannot preserve external module ports.
   if (!isa<FModuleOp>(module))
     return PreserveAggregate::None;
+
+  // If `module` is a top-module, we have to lower ports. Don't read attributes
+  // of `module` since the attributes could be mutated in a different thread.
   if (aggregatePreservationMode != PreserveAggregate::None &&
-      preservePublicTypes && cast<hw::HWModuleLike>(*module).isPublic())
+      preservePublicTypes &&
+      module->getParentOfType<CircuitOp>().getMainModule(&symTbl) == module)
     return PreserveAggregate::None;
   return aggregatePreservationMode;
 }