1 files changed, 43 insertions, 9 deletions

diff --git a/src/main/scala/chisel3/util/Bitwise.scala b/src/main/scala/chisel3/util/Bitwise.scala
index 289d27b1..950fa65f 100644
--- a/src/main/scala/chisel3/util/Bitwise.scala
+++ b/src/main/scala/chisel3/util/Bitwise.scala
@@ -8,11 +8,21 @@ package chisel3.util
 import chisel3._
 import chisel3.core.SeqUtils
 
+/** Creates repetitions of each bit of the input in order.
+  *
+  * @example {{{
+  * FillInterleaved(2, "b1 0 0 0".U)  // equivalent to "b11 00 00 00".U
+  * FillInterleaved(2, "b1 0 0 1".U)  // equivalent to "b11 00 00 11".U
+  * FillInterleaved(2, myUIntWire)  // dynamic interleaved fill
+  *
+  * FillInterleaved(2, Seq(true.B, false.B, false.B, false.B))  // equivalent to "b11 00 00 00".U
+  * FillInterleaved(2, Seq(true.B, false.B, false.B, true.B))  // equivalent to "b11 00 00 11".U
+  * }}}
+  */
 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)
 
@@ -23,14 +33,31 @@ object FillInterleaved {
   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.
+/** Returns the number of bits set (value is 1 or true) in the input signal.
+  *
+  * @example {{{
+  * PopCount(Seq(true.B, false.B, true.B, true.B))  // evaluates to 3.U
+  * PopCount(Seq(false.B, false.B, true.B, false.B))  // evaluates to 1.U
+  *
+  * PopCount("b1011".U)  // evaluates to 3.U
+  * PopCount("b0010".U)  // evaluates to 1.U
+  * PopCount(myUIntWire)  // dynamic count
+  * }}}
   */
-object PopCount
-{
+object PopCount {
   def apply(in: Iterable[Bool]): UInt = SeqUtils.count(in.toSeq)
+
   def apply(in: Bits): UInt = apply((0 until in.getWidth).map(in(_)))
 }
 
+/** Create repetitions of the input using a tree fanout topology.
+  *
+  * @example {{{
+  * Fill(2, "b1000".U)  // equivalent to "b1000 1000".U
+  * Fill(2, "b1001".U)  // equivalent to "b1001 1001".U
+  * Fill(2, myUIntWire)  // dynamic fill
+  * }}}
+  */
 object Fill {
   /** Create n repetitions of x using a tree fanout topology.
     *
@@ -38,10 +65,10 @@ object Fill {
     */
   def apply(n: Int, x: UInt): UInt = {
     n match {
-      case 0 => UInt.width(0)
+      case 0 => UInt(0.W)
       case 1 => x
       case _ if x.isWidthKnown && x.getWidth == 1 =>
-        Mux(x.toBool, UInt((BigInt(1) << n) - 1, n), UInt(0, n))
+        Mux(x.toBool, ((BigInt(1) << n) - 1).asUInt(n.W), 0.U(n.W))
       case _ if n > 1 =>
         val p2 = Array.ofDim[UInt](log2Up(n + 1))
         p2(0) = x
@@ -53,6 +80,14 @@ object Fill {
   }
 }
 
+/** Returns the input in bit-reversed order. Useful for little/big-endian conversion.
+  *
+  * @example {{{
+  * Reverse("b1101".U)  // equivalent to "b1011".U
+  * Reverse("b1101".U(8.W))  // equivalent to "b10110000".U
+  * Reverse(myUIntWire)  // dynamic reverse
+  * }}}
+  */
 object Reverse {
   private def doit(in: UInt, length: Int): UInt = {
     if (length == 1) {
@@ -61,7 +96,7 @@ object Reverse {
       // This esoterica improves simulation performance
       var res = in
       var shift = length >> 1
-      var mask = UInt((BigInt(1) << length) - 1, length)
+      var mask = ((BigInt(1) << length) - 1).asUInt(length.W)
       do {
         mask = mask ^ (mask(length-shift-1,0) << shift)
         res = ((res >> shift) & mask) | ((res(length-shift-1,0) << shift) & ~mask)
@@ -73,7 +108,6 @@ object Reverse {
       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)
 }