Add BSwitch macro and update gtkwave config

macros/src/utils/BSwitchMacro.scala

@@ -0,0 +1,77 @@
+package macros.utils
+
+import scala.language.experimental.macros
+import scala.reflect.macros.blackbox._
+import chisel3._
+import chisel3.experimental.SourceInfo
+import chisel3.util.BitPat
+
+object bis {
+
+    /** Executes `block` if the bswitch condition matchs `v`.
+      */
+    def apply(v: BitPat)(block: => Any): Unit = {
+        locally((v, block))
+        require(
+            false,
+            "The 'bis' keyword may not be used outside of a bswitch."
+        )
+    }
+}
+
+class BSwitchContext(
+    cond: UInt,
+    whenContext: Option[WhenContext],
+    lits: Set[BitPat]
+) {
+    def bis(
+        pat: BitPat
+    )(block: => Any)(implicit
+        sourceInfo: SourceInfo
+    ): BSwitchContext = {
+        require(
+            !lits.exists(w => {
+                w.overlap(pat)
+            }),
+            "all bis conditions must be mutually exclusive!"
+        )
+
+        // def instead of val so that logic ends up in legal place
+        def p = (cond === pat)
+        whenContext match {
+            case Some(w) =>
+                new BSwitchContext(
+                    cond,
+                    Some(w.elsewhen(p)(block)),
+                    lits + pat
+                )
+            case None =>
+                new BSwitchContext(
+                    cond,
+                    Some(when(p)(block)),
+                    lits + pat
+                )
+        }
+    }
+}
+
+object bswitch {
+    def apply[T <: Element](cond: T)(x: => Any): Unit = macro impl
+    def impl(c: Context)(cond: c.Tree)(x: c.Tree): c.Tree = {
+        import c.universe._
+        val q"..$body" = x
+        val res = body.foldLeft(
+            q"""new macros.utils.BSwitchContext($cond, None, Set.empty)"""
+        ) { case (acc, tree) =>
+            tree match {
+                case q"macros.utils.bis.apply( ..$params )( ..$body )" =>
+                    q"$acc.bis( ..$params )( ..$body )"
+                case _ =>
+                    throw new Exception(
+                        s"Cannot include blocks that do not begin with bis() in bswitch."
+                    )
+            }
+        }
+        q"""{ $res }"""
+    }
+}