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ReduceOthers: remove constants from the balanced AND tree

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This commit is contained in:
Wesley W. Terpstra
2017-06-23 00:28:05 -07:00
parent 48611266fa
commit 2d8b2f4edd
2 changed files with 41 additions and 13 deletions
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45
src/main/scala/util/ReduceOthers.scala
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@ -1,4 +1,4 @@
// See LICENSE.Berkeley for license details.
// See LICENSE.SiFive for license details.
package util
import Chisel._
@ -7,16 +7,29 @@ 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(_ && _)
val (literals, variables) = x.partition(_.isLit)
val falses = literals.count(_.litValue == 0)
if (falses > 2) {
Seq.fill(x.size) { Bool(false) }
} else if (falses == 1) {
x.map { b =>
if (b.isLit && b.litValue == 0) {
variables.foldLeft(Bool(true))(_ && _)
} else {
Bool(false)
}
}
} 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)
var (out, all) = helper(variables)
x.map { b =>
if (b.isLit) {
all
} else {
val sel = out.head
out = out.tail
sel
}
}
}
}
@ -24,4 +37,18 @@ object ReduceOthers {
def apply(x: Seq[(Bool, Bool)]) {
(x.map(_._1) zip apply(x.map(_._2))) foreach { case (w, x) => w := x }
}
private def helper(x: Seq[Bool]): (Seq[Bool], Bool) = {
if (x.size <= 1) {
(Seq.fill(x.size) { Bool(true) }, x.headOption.getOrElse(Bool(true)))
} else if (x.size <= 3) {
(Seq.tabulate(x.size) { i =>
(x.take(i) ++ x.drop(i+1)).reduce(_ && _)
}, x.reduce(_ && _))
} else {
val (half, all) = helper(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)
}, all)
}
}
}