add support to build chisel from source

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "dependencies/cde"]
 	path = dependencies/cde
 	url = https://github.com/chipsalliance/cde.git
+[submodule "dependencies/chisel"]
+	path = dependencies/chisel
+	url = https://github.com/chipsalliance/chisel.git

build.sc

@@ -4,20 +4,33 @@ import mill.scalalib.publish._
 import coursier.maven.MavenRepository
 import $file.dependencies.hardfloat.common
 import $file.dependencies.cde.common
+import $file.dependencies.chisel.build
 import $file.common
 
 object v {
-  val scala = "2.13.10"
+  val scala = "2.13.12"
   // the first version in this Map is the mainly supported version which will be used to run tests
   val chiselCrossVersions = Map(
     "3.6.0" -> (ivy"edu.berkeley.cs::chisel3:3.6.0", ivy"edu.berkeley.cs:::chisel3-plugin:3.6.0"),
     "5.0.0" -> (ivy"org.chipsalliance::chisel:5.0.0", ivy"org.chipsalliance:::chisel-plugin:5.0.0"),
+    // build from project from source
+    "source" -> (ivy"org.chipsalliance::chisel:99", ivy"org.chipsalliance:::chisel-plugin:99"),
   )
   val mainargs = ivy"com.lihaoyi::mainargs:0.5.0"
   val json4sJackson = ivy"org.json4s::json4s-jackson:4.0.5"
   val scalaReflect = ivy"org.scala-lang:scala-reflect:${scala}"
 }
 
+// Build form source only for dev
+object chisel extends Chisel
+
+trait Chisel
+  extends millbuild.dependencies.chisel.build.Chisel {
+  def crossValue = v.scala
+  override def millSourcePath = os.pwd / "dependencies" / "chisel"
+  def scalaVersion = T(v.scala)
+}
+
 object macros extends Macros
 
 trait Macros
@@ -41,13 +54,13 @@ trait Hardfloat
 
   override def millSourcePath = os.pwd / "dependencies" / "hardfloat" / "hardfloat"
 
-  def chiselModule = None
+  def chiselModule = Option.when(crossValue == "source")(chisel)
 
-  def chiselPluginJar = None
+  def chiselPluginJar = T(Option.when(crossValue == "source")(chisel.pluginModule.jar()))
 
-  def chiselIvy = Some(v.chiselCrossVersions(crossValue)._1)
+  def chiselIvy = Option.when(crossValue != "source")(v.chiselCrossVersions(crossValue)._1)
 
-  def chiselPluginIvy = Some(v.chiselCrossVersions(crossValue)._2)
+  def chiselPluginIvy = Option.when(crossValue != "source")(v.chiselCrossVersions(crossValue)._2)
 }
 
 object cde extends CDE
@@ -73,13 +86,13 @@ trait RocketChip
 
   override def millSourcePath = super.millSourcePath / os.up
 
-  def chiselModule = None
+  def chiselModule = Option.when(crossValue == "source")(chisel)
 
-  def chiselPluginJar = None
+  def chiselPluginJar = T(Option.when(crossValue == "source")(chisel.pluginModule.jar()))
 
-  def chiselIvy = Some(v.chiselCrossVersions(crossValue)._1)
+  def chiselIvy = Option.when(crossValue != "source")(v.chiselCrossVersions(crossValue)._1)
 
-  def chiselPluginIvy = Some(v.chiselCrossVersions(crossValue)._2)
+  def chiselPluginIvy = Option.when(crossValue != "source")(v.chiselCrossVersions(crossValue)._2)
 
   def macrosModule = macros