Fix sign extension issue in Emitter (#1785)

* add sign-extend const-prop test

* Emitter: don't wrap Neg operand in concat

1 files changed, 10 insertions, 0 deletions

diff --git a/src/test/scala/firrtlTests/ConstantPropagationTests.scala b/src/test/scala/firrtlTests/ConstantPropagationTests.scala
index 653653d6..efe85e48 100644
--- a/src/test/scala/firrtlTests/ConstantPropagationTests.scala
+++ b/src/test/scala/firrtlTests/ConstantPropagationTests.scala
@@ -1651,4 +1651,14 @@ class ConstantPropagationEquivalenceSpec extends FirrtlFlatSpec {
           |""".stripMargin
      firrtlEquivalenceTest(input, transforms)
    }
+
+  "propagation of signed expressions" should "have the correct signs" in {
+    val input =
+      s"""circuit SignTester :
+         |  module SignTester :
+         |    output ref : SInt<3>
+         |    ref <= mux(UInt<1>("h0"), SInt<3>("h0"), neg(UInt<2>("h3")))
+         |""".stripMargin
+    firrtlEquivalenceTest(input, transforms)
+  }
 }