[FIRRTL] Remove nonlocal field from annotations when NLA becomes local (#9329)

This patch adds logic to the module inliner to detect when a NLA
becomes local after inlining mutations. When this occurs,
the `circt.nonlocal` field is removed from the annotation since it is no
longer needed.

Author: uenoku

lib/Dialect/FIRRTL/Transforms/ModuleInliner.cpp

@@ -1560,6 +1560,15 @@ LogicalResult Inliner::run() {
         if (mnla.isDead())
           return true;
 
+        // If the NLA becomes local after mutation (or sometimes an NLA is
+        // annotated even when the annotation is local in the first place),
+        // remove the nonlocal field.
+        if (mnla.isLocal()) {
+          anno.removeMember("circt.nonlocal");
+          newAnnotations.push_back(anno.getAttr());
+          return true;
+        }
+
         // Do nothing if there are no additional NLAs to add or if we're
         // dealing with a root module.  Root modules have already been updated
         // earlier in the pass.  We only need to update NLA paths which are

test/Dialect/FIRRTL/inliner.mlir

@@ -1426,3 +1426,17 @@ firrtl.circuit "FormalMarkerIsUse" {
   // CHECK: firrtl.module private @Foo
   // CHECK: firrtl.module private @Bar
 }
+
+
+// -----
+
+firrtl.circuit "RemoveNonLocalFromLocal" {
+  // CHECK-NOT: @dutNLA
+  hw.hierpath private @dutNLA [@RemoveNonLocalFromLocal::@sym]
+  firrtl.module @Bar() {}
+  // CHECK-LABEL: firrtl.module @RemoveNonLocalFromLocal
+  firrtl.module @RemoveNonLocalFromLocal() {
+    // CHECK: firrtl.instance bar sym @sym {annotations = [{class = "circt.tracker", id = distinct[0]<>}]} @Bar()
+    firrtl.instance bar sym @sym {annotations = [{circt.nonlocal = @dutNLA, class = "circt.tracker", id = distinct[0]<>}]} @Bar()
+  }
+}