Improve Fill code generation

1 files changed, 4 insertions, 9 deletions

diff --git a/src/main/scala/chisel3/util/Bitwise.scala b/src/main/scala/chisel3/util/Bitwise.scala
index 7f295200..3134d043 100644
--- a/src/main/scala/chisel3/util/Bitwise.scala
+++ b/src/main/scala/chisel3/util/Bitwise.scala
@@ -29,22 +29,17 @@ object Fill {
     n match {
       case 0 => UInt(width=0)
       case 1 => x
-      case y if n > 1 =>
+      case _ if x.width.known && 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(y + 1)).filter(i => (y & (1 << i)) != 0).map(p2(_)))
+        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.")
     }
   }
-  /** Fan out x n times */
-  def apply(n: Int, x: Bool): UInt =
-    if (n > 1) {
-      UInt(0,n) - x
-    } else {
-      apply(n, x: UInt)
-    }
 }
 
 /** Litte/big bit endian convertion: reverse the order of the bits in a UInt.