Enable Clock Invalidation (#2485) (#2487)

Loosen restrictions on clocks to enable them to be connected to
DontCare, i.e., be invalidated.

Co-authored-by: Jack Koenig <koenig@sifive.com>
Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Co-authored-by: Jack Koenig <koenig@sifive.com>
(cherry picked from commit 5d8a0c8e406376f7ceda91273fb0fa7a646865aa)

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/InvalidateAPISpec.scala b/src/test/scala/chiselTests/InvalidateAPISpec.scala
index 2c51e5d2..dbd353a0 100644
--- a/src/test/scala/chiselTests/InvalidateAPISpec.scala
+++ b/src/test/scala/chiselTests/InvalidateAPISpec.scala
@@ -228,4 +228,12 @@ class InvalidateAPISpec extends ChiselPropSpec with Matchers with BackendCompila
     val firrtlOutput = myGenerateFirrtl(new ModuleWithoutDontCare)
     firrtlOutput should include("is invalid")
   }
+
+  property("a clock should be able to be connected to a DontCare") {
+    class ClockConnectedToDontCare extends Module {
+      val foo = IO(Output(Clock()))
+      foo := DontCare
+    }
+    myGenerateFirrtl(new ClockConnectedToDontCare) should include("foo is invalid")
+  }
 }