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diff --git a/src/main/scala/chisel3/util/Bitwise.scala b/src/main/scala/chisel3/util/Bitwise.scala
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+++ b/src/main/scala/chisel3/util/Bitwise.scala
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+// See LICENSE for license details.
+
+/** Miscellaneous circuit generators operating on bits.
+  */
+
+package chisel3.util
+
+import chisel3._
+import chisel3.core.SeqUtils
+
+object FillInterleaved {
+  /** Creates n repetitions of each bit of x in order.
+    *
+    * Output data-equivalent to in(size(in)-1) (n times) ## ... ## in(1) (n times) ## in(0) (n times)
+    * For example, FillInterleaved(2, "b1000") === UInt("b11 00 00 00")
+    */
+  def apply(n: Int, in: UInt): UInt = apply(n, in.toBools)
+
+  /** Creates n repetitions of each bit of x in order.
+    *
+    * Output data-equivalent to in(size(in)-1) (n times) ## ... ## in(1) (n times) ## in(0) (n times)
+    */
+  def apply(n: Int, in: Seq[Bool]): UInt = Cat(in.map(Fill(n, _)).reverse)
+}
+
+/** Returns the number of bits set (i.e value is 1) in the input signal.
+  */
+object PopCount
+{
+  def apply(in: Iterable[Bool]): UInt = SeqUtils.count(in.toSeq)
+  def apply(in: Bits): UInt = apply((0 until in.getWidth).map(in(_)))
+}
+
+object Fill {
+  /** Create n repetitions of x using a tree fanout topology.
+    *
+    * Output data-equivalent to x ## x ## ... ## x (n repetitions).
+    */
+  def apply(n: Int, x: UInt): UInt = {
+    n match {
+      case 0 => UInt.width(0)
+      case 1 => x
+      case _ if x.isWidthKnown && x.getWidth == 1 =>
+        Mux(x.toBool, UInt((BigInt(1) << n) - 1, n), UInt(0, n))
+      case _ if n > 1 =>
+        val p2 = Array.ofDim[UInt](log2Up(n + 1))
+        p2(0) = x
+        for (i <- 1 until p2.length)
+          p2(i) = Cat(p2(i-1), p2(i-1))
+        Cat((0 until log2Up(n + 1)).filter(i => (n & (1 << i)) != 0).map(p2(_)))
+      case _ => throw new IllegalArgumentException(s"n (=$n) must be nonnegative integer.")
+    }
+  }
+}
+
+object Reverse {
+  private def doit(in: UInt, length: Int): UInt = {
+    if (length == 1) {
+      in
+    } else if (isPow2(length) && length >= 8 && length <= 64) {
+      // This esoterica improves simulation performance
+      var res = in
+      var shift = length >> 1
+      var mask = UInt((BigInt(1) << length) - 1, length)
+      do {
+        mask = mask ^ (mask(length-shift-1,0) << shift)
+        res = ((res >> shift) & mask) | ((res(length-shift-1,0) << shift) & ~mask)
+        shift = shift >> 1
+      } while (shift > 0)
+      res
+    } else {
+      val half = (1 << log2Up(length))/2
+      Cat(doit(in(half-1,0), half), doit(in(length-1,half), length-half))
+    }
+  }
+  /** Returns the input in bit-reversed order. Useful for little/big-endian conversion.
+    */
+  def apply(in: UInt): UInt = doit(in, in.getWidth)
+}