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// SPDX-License-Identifier: Apache-2.0
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)
}
}
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