From afaf4da94e7cfded68684c9629146ce05e445217 Mon Sep 17 00:00:00 2001
From: Mike Urbach <mike.urbach@sifive.com>
Date: Sat, 16 Mar 2024 16:57:49 -0700
Subject: [PATCH] [FIRRTL] Handle either kind of path attribute in
 LowerClasses.

Sometimes the start of a hierarchical path is an InnerRefAttr, and
sometimes the path is just a single FlatSymbolRefAttr. Either way, we
just need the StringAttr refering to the module name. There is a
helper called `root` for this on HierPathOp. But at this point we are
constructing the path to build a HierPathOp, we don't already have
one. So, I've implemented this the same as how `root` is implemented.
---
 lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp b/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
index f0e54d3e1e1c..47e11ca2abf3 100644
--- a/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
+++ b/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
@@ -384,7 +384,11 @@ LogicalResult LowerClassesPass::processPaths(
       // We will plumb in the basepath from this module.
       StringAttr altBasePathModule;
       if (needsAltBasePath) {
-        altBasePathModule = cast<hw::InnerRefAttr>(path.front()).getModule();
+        altBasePathModule =
+            TypeSwitch<Attribute, StringAttr>(path.front())
+                .Case<FlatSymbolRefAttr>([](auto a) { return a.getAttr(); })
+                .Case<hw::InnerRefAttr>([](auto a) { return a.getModule(); });
+
         pathInfoTable.addAltBasePathRoot(altBasePathModule);
       }