From 8a611772245e8384f6eaf31afa8a990121d7576b Mon Sep 17 00:00:00 2001
From: Howard Mao <zhehao.mao@gmail.com>
Date: Thu, 19 Nov 2015 15:04:09 -0800
Subject: [PATCH] generalize TwoWayCounter

---
 uncore/src/main/scala/tilelink.scala | 5 +----
 uncore/src/main/scala/util.scala     | 9 +++++++++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/uncore/src/main/scala/tilelink.scala b/uncore/src/main/scala/tilelink.scala
index 6be218c3..2e02962a 100644
--- a/uncore/src/main/scala/tilelink.scala
+++ b/uncore/src/main/scala/tilelink.scala
@@ -1386,14 +1386,11 @@ trait HasDataBeatCounters {
       down: DecoupledIO[S],
       beat: UInt = UInt(0),
       track: T => Bool = (t: T) => Bool(true)): (Bool, UInt, Bool, UInt, Bool) = {
-    val cnt = Reg(init = UInt(0, width = log2Up(max+1)))
     val (up_idx, up_done) = connectDataBeatCounter(up.fire(), up.bits, beat)
     val (down_idx, down_done) = connectDataBeatCounter(down.fire(), down.bits, beat)
     val do_inc = up_done && track(up.bits)
     val do_dec = down_done
-    cnt := Mux(do_dec,
-            Mux(do_inc, cnt, cnt - UInt(1)),
-            Mux(do_inc, cnt + UInt(1), cnt))
+    val cnt = TwoWayCounter(do_inc, do_dec, max)
     (cnt > UInt(0), up_idx, up_done, down_idx, down_done)
   }
 }
diff --git a/uncore/src/main/scala/util.scala b/uncore/src/main/scala/util.scala
index e5b14e7f..b0036b37 100644
--- a/uncore/src/main/scala/util.scala
+++ b/uncore/src/main/scala/util.scala
@@ -42,6 +42,15 @@ object ZCounter {
   }
 }
 
+object TwoWayCounter {
+  def apply(up: Bool, down: Bool, max: Int): UInt = {
+    val cnt = Reg(init = UInt(0, log2Up(max+1)))
+    when (up && !down) { cnt := cnt + UInt(1) }
+    when (down && !up) { cnt := cnt - UInt(1) }
+    cnt
+  }
+}
+
 class FlowThroughSerializer[T <: Bundle with HasTileLinkData](gen: T, n: Int) extends Module {
   val io = new Bundle {
     val in = Decoupled(gen).flip