diff options
| -rw-r--r-- | chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala | 4 | ||||
| -rw-r--r-- | src/test/scala/chiselTests/PopCount.scala | 27 |
2 files changed, 30 insertions, 1 deletions
diff --git a/chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala b/chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala index e87fb045..f15fb178 100644 --- a/chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala +++ b/chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala @@ -37,7 +37,9 @@ private[chisel3] object SeqUtils { def do_count(in: Seq[Bool])(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): UInt = in.size match { case 0 => 0.U case 1 => in.head - case n => count(in take n/2) +& count(in drop n/2) + case n => + val sum = count(in take n/2) +& count(in drop n/2) + sum(BigInt(n).bitLength - 1, 0) } /** Returns the data value corresponding to the first true predicate. diff --git a/src/test/scala/chiselTests/PopCount.scala b/src/test/scala/chiselTests/PopCount.scala new file mode 100644 index 00000000..d9b3b837 --- /dev/null +++ b/src/test/scala/chiselTests/PopCount.scala @@ -0,0 +1,27 @@ +// See LICENSE for license details. + +package chiselTests + +import chisel3._ +import chisel3.util.PopCount +import org.scalatest._ +import org.scalatest.prop._ +import chisel3.testers.BasicTester + +class PopCountTester(n: Int) extends BasicTester { + val x = RegInit(0.U(n.W)) + x := x + 1.U + when (RegNext(x === ~0.U(n.W))) { stop() } + + val result = PopCount(x.asBools) + val expected = x.asBools.foldLeft(0.U)(_ +& _) + assert(result === expected) + + require(result.getWidth == BigInt(n).bitLength) +} + +class PopCountSpec extends ChiselPropSpec { + property("Mul lookup table should return the correct result") { + forAll(smallPosInts) { (n: Int) => assertTesterPasses { new PopCountTester(n) } } + } +} |