From 5744ce6df80ba9ec153b07744eb8da7a01876f2c Mon Sep 17 00:00:00 2001
From: Andrew Waterman
Date: Thu, 14 Mar 2019 02:04:05 -0700
Subject: Add PopCount test

---
 src/test/scala/chiselTests/PopCount.scala | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 src/test/scala/chiselTests/PopCount.scala

diff --git a/src/test/scala/chiselTests/PopCount.scala b/src/test/scala/chiselTests/PopCount.scala
new file mode 100644
index 00000000..2c144382
--- /dev/null
+++ b/src/test/scala/chiselTests/PopCount.scala
@@ -0,0 +1,25 @@
+// 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)
+}
+
+class PopCountSpec extends ChiselPropSpec {
+  property("Mul lookup table should return the correct result") {
+    forAll(smallPosInts) { (n: Int) =>  assertTesterPasses { new PopCountTester(n) } }
+  }
+}
-- 
cgit v1.2.3


From 6c39009771d3c9169f66e8a65b5d8f996d5c6e1f Mon Sep 17 00:00:00 2001
From: Andrew Waterman
Date: Thu, 14 Mar 2019 02:04:23 -0700
Subject: Add width constraint to PopCount test (which currently fails)

---
 src/test/scala/chiselTests/PopCount.scala | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/test/scala/chiselTests/PopCount.scala b/src/test/scala/chiselTests/PopCount.scala
index 2c144382..d9b3b837 100644
--- a/src/test/scala/chiselTests/PopCount.scala
+++ b/src/test/scala/chiselTests/PopCount.scala
@@ -16,6 +16,8 @@ class PopCountTester(n: Int) extends BasicTester {
   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 {
-- 
cgit v1.2.3


From 52168a5f3edee6c427a2bf4e1fd033259b46ac9e Mon Sep 17 00:00:00 2001
From: Andrew Waterman
Date: Thu, 14 Mar 2019 02:04:34 -0700
Subject: Fix PopCount width

---
 chiselFrontend/src/main/scala/chisel3/core/SeqUtils.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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.
-- 
cgit v1.2.3