FixedPoint number support for chisel3 (#328)

* FixedPoint number support for chisel3
FixedPoint numbers have a width and a binary position
Either, neither or both maybe inferred.
Firrtl will convert these to SInts during lowering passes

* Fixes based on Jack's comments on PR #328

* Add experimental warning to FixedPoint class and object

* Fixed comment per Adam's comment on PR #328

1 files changed, 41 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/FixedPointSpec.scala b/src/test/scala/chiselTests/FixedPointSpec.scala
new file mode 100644
index 00000000..69015e42
--- /dev/null
+++ b/src/test/scala/chiselTests/FixedPointSpec.scala
@@ -0,0 +1,41 @@
+// See LICENSE for license details.
+
+package chiselTests
+
+import chisel3._
+import chisel3.testers.BasicTester
+import org.scalatest._
+
+//scalastyle:off magic.number
+class FixedPointSpec extends FlatSpec with Matchers {
+  behavior of "fixed point utilities"
+
+  they should "allow conversion between doubles and the bigints needed to represent them" in {
+    val initialDouble = 0.125
+    val bigInt = FixedPoint.toBigInt(initialDouble, 4)
+    val finalDouble = FixedPoint.toDouble(bigInt, 4)
+
+    initialDouble should be(finalDouble)
+  }
+}
+
+class SBP extends Module {
+  val io = IO(new Bundle {
+    val in =  Input(FixedPoint(6, 2))
+    val out = Output(FixedPoint(4, 0))
+  })
+  io.out := io.in.setBinaryPoint(0)
+}
+class SBPTester extends BasicTester {
+  val dut = Module(new SBP)
+  dut.io.in := FixedPoint.fromDouble(3.75, binaryPoint = 2)
+
+  assert(dut.io.out === FixedPoint.fromDouble(3.0, binaryPoint = 0))
+
+  stop()
+}
+class SBPSpec extends ChiselPropSpec {
+  property("should allow set binary point") {
+    assertTesterPasses { new SBPTester }
+  }
+}