From b43bcdfcd129e7ea6e770511ea20f9d079017047 Mon Sep 17 00:00:00 2001
From: "Wesley W. Terpstra" <wesley@sifive.com>
Date: Tue, 7 Nov 2017 11:29:49 -0800
Subject: [PATCH] CloneModule: beat chisel into submission

---
 src/main/scala/diplomacy/CloneModule.scala | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 src/main/scala/diplomacy/CloneModule.scala

diff --git a/src/main/scala/diplomacy/CloneModule.scala b/src/main/scala/diplomacy/CloneModule.scala
new file mode 100644
index 00000000..bacb4c6c
--- /dev/null
+++ b/src/main/scala/diplomacy/CloneModule.scala
@@ -0,0 +1,61 @@
+// See LICENSE.SiFive for license details.
+
+// !!! HACK TO WORK-AROUND MISSING CHISEL FEATURE
+// !!! We need to be inside the chisel3 package to access Builder
+
+package chisel3.shim
+
+import Chisel._
+import chisel3.experimental.{RawModule, MultiIOModule, BaseModule}
+import chisel3.internal.Builder
+import chisel3.core.UserModule
+import chisel3.internal.firrtl.{Command, DefInstance}
+import scala.collection.immutable.ListMap
+import scala.collection.mutable.ArrayBuffer
+
+class CloneModule private (model: RawModule) extends BlackBox
+{
+  import CloneModule._
+  override def desiredName = model.name
+  val io = IO(new ClonePorts(model.getPorts.map(_.id): _*))
+}
+
+class HackDefInstance(imp: DefInstance, _name: => String) extends DefInstance(imp.sourceInfo, imp.id, imp.ports)
+{
+  override def name = _name
+}
+
+object CloneModule
+{
+  def apply(model: BaseModule): ClonePorts = {
+    // Create the 'BlackBox' stand-in
+    val mod = Module(new CloneModule(model.asInstanceOf[RawModule]))
+    // Rewrite the instance definition to be the original module
+    // (this is needed because the original module gets clobbered by DCE + constant prop)
+    val method = classOf[UserModule].getDeclaredMethod("_commands")
+    method.setAccessible(true)
+    val commands = method.invoke(Builder.forcedUserModule).asInstanceOf[ArrayBuffer[Command]]
+    val victimIdx = commands.lastIndexWhere {
+      case DefInstance(_, kill, _) => mod eq kill
+      case _ => false
+    }
+    val victim = commands(victimIdx).asInstanceOf[DefInstance]
+    val standin = new HackDefInstance(victim.copy(id = model), victim.name)
+    commands.update(victimIdx, standin)
+    // Wire it up
+    model match {
+      case _: MultiIOModule =>
+        mod.io("clock") := Module.clock
+        mod.io("reset") := Module.reset
+      case _: RawModule => // Do nothing
+    }
+    mod.io
+  }
+}
+
+class ClonePorts(elts: Data*) extends Record
+{
+  val elements = ListMap(elts.map(d => d.instanceName -> d.chiselCloneType): _*)
+  def apply(field: String) = elements(field)
+  override def cloneType = (new ClonePorts(elts: _*)).asInstanceOf[this.type]
+}