Fix up Absolute value #abs (#491)

* Fix up Absolute value #abs
Defines #abs in Num
Implement #abs in UInt
Change #abs in SInt to return an SInt
Change #abs in FixedPoint to return a FixedPoint
Added  a couple of tests
Add some scala style suppression to Bits so I can read code in IntelliJ

* Per review
Add tests that abs works for positive values
Added SInt and UInt tests for abs to new underpopulated IntegerMathSpec
Used fixed point literals in fixed points abs definition

2 files changed, 58 insertions, 17 deletions

diff --git a/src/test/scala/chiselTests/FixedPointSpec.scala b/src/test/scala/chiselTests/FixedPointSpec.scala
index bfbb4e46..d0557e66 100644
--- a/src/test/scala/chiselTests/FixedPointSpec.scala
+++ b/src/test/scala/chiselTests/FixedPointSpec.scala
@@ -21,23 +21,31 @@ class FixedPointLiteralSpec extends FlatSpec with Matchers {
 }
 
 class FixedPointFromBitsTester extends BasicTester {
-    val uint = 3.U(4.W)
-    val sint = -3.S
-    val fp   = FixedPoint.fromDouble(3.0, width = 4, binaryPoint = 0)
-    val fp_tpe = FixedPoint(4.W, 1.BP)
-    val uint_result = FixedPoint.fromDouble(1.5, width = 4, binaryPoint = 1)
-    val sint_result = FixedPoint.fromDouble(-1.5, width = 4, binaryPoint = 1)
-    val fp_result   = FixedPoint.fromDouble(1.5, width = 4, binaryPoint = 1)
-
-    val uint2fp = fp_tpe.fromBits(uint)
-    val sint2fp = fp_tpe.fromBits(sint)
-    val fp2fp   = fp_tpe.fromBits(fp)
-
-    assert(uint2fp === uint_result)
-    assert(sint2fp === sint_result)
-    assert(fp2fp   === fp_result)
-
-    stop()
+  val uint = 3.U(4.W)
+  val sint = -3.S
+
+  val fp   = FixedPoint.fromDouble(3.0, width = 4, binaryPoint = 0)
+  val fp_tpe = FixedPoint(4.W, 1.BP)
+  val uint_result = FixedPoint.fromDouble(1.5, width = 4, binaryPoint = 1)
+  val sint_result = FixedPoint.fromDouble(-1.5, width = 4, binaryPoint = 1)
+  val fp_result   = FixedPoint.fromDouble(1.5, width = 4, binaryPoint = 1)
+
+  val uint2fp = fp_tpe.fromBits(uint)
+  val sint2fp = fp_tpe.fromBits(sint)
+  val fp2fp   = fp_tpe.fromBits(fp)
+
+  val negativefp = -3.5.F(binaryPoint = 4)
+  val positivefp = 3.5.F(binaryPoint = 4)
+
+  assert(uint2fp === uint_result)
+  assert(sint2fp === sint_result)
+  assert(fp2fp   === fp_result)
+
+  assert(positivefp.abs() === positivefp)
+  assert(negativefp.abs() === positivefp)
+  assert(negativefp.abs() =/= negativefp)
+
+  stop()
 }
 
 class SBP extends Module {
diff --git a/src/test/scala/chiselTests/IntegerMathSpec.scala b/src/test/scala/chiselTests/IntegerMathSpec.scala
new file mode 100644
index 00000000..3ccade8e
--- /dev/null
+++ b/src/test/scala/chiselTests/IntegerMathSpec.scala
@@ -0,0 +1,33 @@
+// See LICENSE for license details.
+
+package chiselTests
+
+import chisel3._
+import chisel3.testers.BasicTester
+
+//scalastyle:off magic.number
+class IntegerMathTester extends BasicTester {
+
+  //TODO: Add more operators
+
+  /* absolute values tests */
+
+  val uint = 3.U(4.W)
+  val sint = (-3).S()
+  val sintpos = 3.S()
+  val wrongSIntPos = 4.S()
+
+  assert(uint.abs() === uint)
+  assert(sint.abs() === sintpos)
+  assert(sintpos.abs() === sintpos)
+
+  assert(sint.abs() =/= wrongSIntPos)
+
+  stop()
+}
+
+class IntegerMathSpec extends ChiselPropSpec {
+  property("All integer ops should return the correct result") {
+    assertTesterPasses{ new IntegerMathTester }
+  }
+}