From 860e6844708e4b87ced04bcef0eda7810cba106a Mon Sep 17 00:00:00 2001
From: albertchen-sifive
Date: Thu, 13 Sep 2018 22:09:18 -0700
Subject: Do not remove ExtMods with no ports by default (#888)

---
 src/test/scala/firrtlTests/DCETests.scala | 35 +++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'src/test')

diff --git a/src/test/scala/firrtlTests/DCETests.scala b/src/test/scala/firrtlTests/DCETests.scala
index b8345093..a6def402 100644
--- a/src/test/scala/firrtlTests/DCETests.scala
+++ b/src/test/scala/firrtlTests/DCETests.scala
@@ -8,6 +8,7 @@ import firrtl.passes._
 import firrtl.transforms._
 import firrtl.annotations._
 import firrtl.passes.memlib.SimpleTransform
+import FirrtlCheckers._
 
 import java.io.File
 import java.nio.file.Paths
@@ -320,6 +321,40 @@ class DCETests extends FirrtlFlatSpec {
         """.stripMargin
     exec(input, input)
   }
+  "extmodules with no ports" should "NOT be deleted by default" in {
+    val input =
+      """circuit Top :
+        |  extmodule BlackBox :
+        |    defname = BlackBox
+        |  module Top :
+        |    input x : UInt<1>
+        |    output y : UInt<1>
+        |    inst blackBox of BlackBox
+        |    y <= x
+        |""".stripMargin
+    exec(input, input)
+  }
+  "extmodules with no ports marked optimizable" should "be deleted" in {
+    val input =
+      """circuit Top :
+        |  extmodule BlackBox :
+        |    defname = BlackBox
+        |  module Top :
+        |    input x : UInt<1>
+        |    output y : UInt<1>
+        |    inst blackBox of BlackBox
+        |    y <= x
+        |""".stripMargin
+    val check =
+      """circuit Top :
+        |  module Top :
+        |    input x : UInt<1>
+        |    output y : UInt<1>
+        |    y <= x
+        |""".stripMargin
+    val doTouchAnno = OptimizableExtModuleAnnotation(ModuleName("BlackBox", CircuitName("Top")))
+    exec(input, check, Seq(doTouchAnno))
+  }
   // bar.z is not used and thus is dead code, but foo.z is used so this code isn't eliminated
   "Module deduplication" should "should be preserved despite unused output of ONE instance" in {
     val input =
-- 
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