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// See LICENSE for license details.
/** Circuit generators for working with one-hot representations.
*/
package chisel3.util
import chisel3._
/** Returns the bit position of the sole high bit of the input bitvector.
*
* Inverse operation of [[UIntToOH]].
*
* @note assumes exactly one high bit, results undefined otherwise
*/
object OHToUInt {
def apply(in: Seq[Bool]): UInt = apply(Cat(in.reverse), in.size)
def apply(in: Vec[Bool]): UInt = apply(in.asUInt, in.size)
def apply(in: Bits): UInt = apply(in, in.getWidth)
def apply(in: Bits, width: Int): UInt = {
if (width <= 2) {
Log2(in, width)
} else {
val mid = 1 << (log2Up(width)-1)
val hi = in(width-1, mid)
val lo = in(mid-1, 0)
Cat(hi.orR, apply(hi | lo, mid))
}
}
}
/** Returns the bit position of the least-significant high bit of the input bitvector.
*
* Multiple bits may be high in the input.
*/
object PriorityEncoder {
def apply(in: Seq[Bool]): UInt = PriorityMux(in, (0 until in.size).map(UInt(_)))
def apply(in: Bits): UInt = apply(in.toBools)
}
/** Returns the one hot encoding of the input UInt.
*/
object UIntToOH {
def apply(in: UInt, width: Int = -1): UInt =
if (width == -1) {
UInt(1) << in
} else {
(UInt(1) << in(log2Up(width)-1,0))(width-1,0)
}
}
/** Returns a bit vector in which only the least-significant 1 bit in the input vector, if any,
* is set.
*/
object PriorityEncoderOH {
private def encode(in: Seq[Bool]): UInt = {
val outs = Seq.tabulate(in.size)(i => UInt(BigInt(1) << i, in.size))
PriorityMux(in :+ Bool(true), outs :+ UInt(0, in.size))
}
def apply(in: Seq[Bool]): Seq[Bool] = {
val enc = encode(in)
Seq.tabulate(in.size)(enc(_))
}
def apply(in: Bits): UInt = encode((0 until in.getWidth).map(i => in(i)))
}
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