Upstream intervals (#870)

Major features:

- Added Interval type, as well as PrimOps asInterval, clip, wrap, and sqz.
- Changed PrimOp names: bpset -> setp, bpshl -> incp, bpshr -> decp
- Refactored width/bound inferencer into a separate constraint solver
- Added transforms to infer, trim, and remove interval bounds
- Tests for said features

Plan to be released with 1.3

1 files changed, 32 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/constraint/IsNeg.scala b/src/main/scala/firrtl/constraint/IsNeg.scala
new file mode 100644
index 00000000..46f739c6
--- /dev/null
+++ b/src/main/scala/firrtl/constraint/IsNeg.scala
@@ -0,0 +1,32 @@
+// See LICENSE for license details.
+
+package firrtl.constraint
+
+object IsNeg {
+  def apply(child: Constraint): Constraint = new IsNeg(child, 0).reduce()
+}
+
+// Dummy arg is to get around weird Scala issue that can't differentiate between a
+//   private constructor and public apply that share the same arguments
+case class IsNeg private (child: Constraint, dummyArg: Int) extends Constraint {
+  override def reduce(): Constraint = child match {
+    case k: IsKnown => k.neg
+    case x: IsAdd => IsAdd(x.children.map { b => IsNeg(b) })
+    case x: IsMul => IsMul(Seq(IsNeg(x.children.head)) ++ x.children.tail)
+    case x: IsNeg => x.child
+    case x: IsPow => this
+    // -[max(a, b)] -> min[-a, -b]
+    case x: IsMax => IsMin(x.children.map { b => IsNeg(b) })
+    case x: IsMin => IsMax(x.children.map { b => IsNeg(b) })
+    case x: IsVar => this
+    case _ => this
+  }
+
+  lazy val children = Vector(child)
+
+  override def map(f: Constraint=>Constraint): Constraint = IsNeg(f(child))
+
+  override def serialize: String = "(-" + child.serialize + ")"
+}
+
+