1 files changed, 59 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/constraint/IsMax.scala b/src/main/scala/firrtl/constraint/IsMax.scala
new file mode 100644
index 00000000..3f24b7c0
--- /dev/null
+++ b/src/main/scala/firrtl/constraint/IsMax.scala
@@ -0,0 +1,59 @@
+// See LICENSE for license details.
+
+package firrtl.constraint
+
+object IsMax {
+  def apply(left: Constraint, right: Constraint): Constraint = (left, right) match {
+    case (l: IsKnown, r: IsKnown) => l max r
+    case _ => apply(Seq(left, right))
+  }
+  def apply(children: Seq[Constraint]): Constraint = {
+    val x = children.foldLeft(new IsMax(None, Vector(), Vector())) { (add, c) =>
+      add.addChild(c)
+    }
+    x.reduce()
+  }
+}
+
+case class IsMax private[constraint](known: Option[IsKnown],
+                                     mins: Vector[IsMin],
+                                     others: Vector[Constraint]
+                                    ) extends MultiAry {
+
+  def op(b1: IsKnown, b2: IsKnown): IsKnown = b1 max b2
+
+  override def serialize: String = "max(" + children.map(_.serialize).mkString(", ") + ")"
+
+  override def map(f: Constraint=>Constraint): Constraint = IsMax(children.map(f))
+
+  lazy val children: Vector[Constraint] = {
+    if(known.nonEmpty) known.get +: (mins ++ others) else mins ++ others
+  }
+
+  def reduce(): Constraint = {
+    if(children.size == 1) children.head else {
+      (known, mins, others) match {
+        case (Some(IsKnown(a)), _, _) =>
+          // Eliminate minimums who have a known minimum value which is smaller than known maximum value
+          val filteredMins = mins.filter {
+            case IsMin(Some(IsKnown(i)), _, _) if i <= a => false
+            case other => true
+          }
+          // If a successful filter, rerun reduce
+          val newMax = new IsMax(known, filteredMins, others)
+          if(filteredMins.size != mins.size) {
+            newMax.reduce()
+          } else newMax
+        case _ => this
+      }
+    }
+  }
+
+  def addChild(x: Constraint): IsMax = x match {
+    case k: IsKnown => new IsMax(known = merge(Some(k), known), mins, others)
+    case max: IsMax => new IsMax(known = merge(known, max.known), max.mins ++ mins, others ++ max.others)
+    case min: IsMin => new IsMax(known, mins :+ min, others)
+    case other      => new IsMax(known, mins, others :+ other)
+  }
+}
+