Allow a counter to be instantiated using a Scala range (#1515)

* Add positive range generator

* Allow the Counter module to be instantiated with a Scala range

* Use head/last to determine counter width

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>

* Let counter overflow naturally when appropriate

We only need to explicitly wrap counters that don't start at zero, or end on a power of two. Otherwise we just let the counter overflow naturally to avoid wasting an extra mux.

* Require counter range to be non-empty

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/ChiselSpec.scala b/src/test/scala/chiselTests/ChiselSpec.scala
index 7980e772..9518fb5c 100644
--- a/src/test/scala/chiselTests/ChiselSpec.scala
+++ b/src/test/scala/chiselTests/ChiselSpec.scala
@@ -150,6 +150,20 @@ class ChiselPropSpec extends PropSpec with ChiselRunners with ScalaCheckProperty
   // Generator for small positive integers.
   val smallPosInts = Gen.choose(1, 4)
 
+  // Generator for positive (ascending or descending) ranges.
+  def posRange: Gen[Range] = for {
+    dir <- Gen.oneOf(true, false)
+    step <- Gen.choose(1, 3)
+    m <- Gen.choose(1, 10)
+    n <- Gen.choose(1, 10)
+  } yield {
+    if (dir) {
+      Range(m, (m+n)*step, step)
+    } else {
+      Range((m+n)*step, m, -step)
+    }
+  }
+
   // Generator for widths considered "safe".
   val safeUIntWidth = Gen.choose(1, 30)