From 2210e71f429f92887e5913b4fba9474fc25a6318 Mon Sep 17 00:00:00 2001
From: "Wesley W. Terpstra" <wesley@sifive.com>
Date: Fri, 16 Sep 2016 00:49:05 -0700
Subject: [PATCH] tilelink2 AddressDecoder: validate output of optimization

---
 .../scala/uncore/tilelink2/AddressDecoder.scala   | 15 +++++++++++++--
 src/main/scala/uncore/tilelink2/Parameters.scala  |  3 +++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/main/scala/uncore/tilelink2/AddressDecoder.scala b/src/main/scala/uncore/tilelink2/AddressDecoder.scala
index adddc8a5..ea7cacac 100644
--- a/src/main/scala/uncore/tilelink2/AddressDecoder.scala
+++ b/src/main/scala/uncore/tilelink2/AddressDecoder.scala
@@ -28,11 +28,22 @@ object AddressDecoder
         require (!a.overlaps(b)) // it must be possible to disambiguate ports!
       } }
     }
+
     val maxBits = log2Ceil(ports.map(_.map(_.max).max).max + 1)
     val bits = (0 until maxBits).map(BigInt(1) << _).toSeq
     val selected = recurse(Seq(ports.map(_.sorted).sorted(portOrder)), bits)
-    selected.reduceLeft(_ | _)
-    // port validation via mask expansion
+    val output = selected.reduceLeft(_ | _)
+
+    // Modify the AddressSets to allow the new wider match functions
+    val widePorts = ports.map { _.map { _.widen(~output) } }
+    // Verify that it remains possible to disambiguate all ports
+    widePorts.combinations(2).foreach { case Seq(x, y) =>
+      x.foreach { a => y.foreach { b =>
+        require (!a.overlaps(b))
+      } }
+    }
+
+    output
   }
 
   // A simpler version that works for a Seq[Int]
diff --git a/src/main/scala/uncore/tilelink2/Parameters.scala b/src/main/scala/uncore/tilelink2/Parameters.scala
index 6423db3c..7c49e792 100644
--- a/src/main/scala/uncore/tilelink2/Parameters.scala
+++ b/src/main/scala/uncore/tilelink2/Parameters.scala
@@ -98,6 +98,9 @@ case class AddressSet(base: BigInt, mask: BigInt) extends Ordered[AddressSet]
   // A strided slave serves discontiguous ranges
   def strided = alignment1 != mask
 
+  // Widen the match function to ignore all bits in imask
+  def widen(imask: BigInt) = AddressSet(base & ~imask, mask | imask)
+
   // AddressSets have one natural Ordering (the containment order)
   def compare(x: AddressSet) = {
     val primary   = (this.base - x.base).signum // smallest address first