util ReduceOthers produces nlogn cost ready-valid logic

src/main/scala/util/ReduceOthers.scala

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+// See LICENSE.Berkeley for license details.
+
+package util
+import Chisel._
+
+object ReduceOthers {
+  // Given a list of bools, create this output:
+  //   out[i] = AND[j=0..out.size, j!=i] in[j]
+  def apply(x: Seq[Bool]): Seq[Bool] = {
+    if (x.size <= 1) {
+      Seq.fill(x.size) { Bool(true) }
+    } else if (x.size <= 3) {
+      Seq.tabulate(x.size) { i =>
+        (x.take(i) ++ x.drop(i+1)).reduce(_ && _)
+      }
+    } else {
+      val half = ReduceOthers(x.grouped(2).map(_.reduce(_ && _)).toList)
+      Seq.tabulate(x.size) { i =>
+        if ((i ^ 1) >= x.size) half(i/2) else x(i ^ 1) && half(i / 2)
+      }
+    }
+  }
+  // Take pairs of (output_wire, input_bool)
+  def apply(x: Seq[(Bool, Bool)]) {
+    (x.map(_._1) zip apply(x.map(_._2))) foreach { case (w, x) => w := x }
+  }
+}