Make DspComplex multiplies use growing addition. (#157)

DspComplex relies on using the underlying Ring's multiplication. For
UInt, SInt, FixedPoint, etc. these additions wrap instead of grow. For
our implementation of complex multiplication, growing is more desirable
than wrapping.

This commit adds specialized versions of the DspComplex for UInt, SInt,
FixedPoint, etc. that use growing addition.

src/main/scala/dsptools/numbers/chisel_types/DspComplexTypeClass.scala

@@ -3,18 +3,30 @@
 package dsptools.numbers
 
 import chisel3._
+import chisel3.experimental.FixedPoint
 import dsptools.hasContext
 import implicits._
 import chisel3.util.ShiftRegister
 import dsptools.DspException
 
-class DspComplexRing[T <: Data:Ring] extends Ring[DspComplex[T]] with hasContext {
+abstract class DspComplexRing[T <: Data:Ring] extends Ring[DspComplex[T]] with hasContext {
   def plus(f: DspComplex[T], g: DspComplex[T]): DspComplex[T] = {
     DspComplex.wire(f.real + g.real, f.imag + g.imag)
   }
   def plusContext(f: DspComplex[T], g: DspComplex[T]): DspComplex[T] = {
     DspComplex.wire(f.real context_+ g.real, f.imag context_+ g.imag)
   }
+
+  /**
+    * The builtin times calls +. Ideally we'd like to use growing addition, but we're relying on typeclasses and the
+    * default + for UInt, SInt, etc. is wrapping. Thus, we're making an escape hatch just for the default (non-context)
+    * complex multiply.
+    * @param l
+    * @param r
+    * @return the sum of l and r, preferrably growing
+    */
+  protected def plusForTimes(l: T, r: T): T
+
   def times(f: DspComplex[T], g: DspComplex[T]): DspComplex[T] = {
     val c_p_d = g.real + g.imag
     val a_p_b = f.real + f.imag
@@ -59,6 +71,22 @@ class DspComplexRing[T <: Data:Ring] extends Ring[DspComplex[T]] with hasContext
   }
 }
 
+class DspComplexRingUInt extends DspComplexRing[UInt] {
+  override def plusForTimes(l: UInt, r: UInt): UInt = l +& r
+}
+
+class DspComplexRingSInt extends DspComplexRing[SInt] {
+  override def plusForTimes(l: SInt, r: SInt): SInt = l +& r
+}
+
+class DspComplexRingFixed extends DspComplexRing[FixedPoint] {
+  override def plusForTimes(l: FixedPoint, r: FixedPoint): FixedPoint = l +& r
+}
+
+class DspComplexRingData[T <: Data : Ring] extends DspComplexRing[T] {
+  override protected def plusForTimes(l: T, r: T): T = l + r
+}
+
 class DspComplexEq[T <: Data:Eq] extends Eq[DspComplex[T]] with hasContext {
   override def eqv(x: DspComplex[T], y: DspComplex[T]): Bool = {
     Eq[T].eqv(x.real, y.real) && Eq[T].eqv(x.imag, y.imag)
@@ -81,9 +109,15 @@ class DspComplexBinaryRepresentation[T <: Data:Ring:BinaryRepresentation] extend
     DspComplex.wire(BinaryRepresentation[T].trimBinary(a.real, n), BinaryRepresentation[T].trimBinary(a.imag, n))
 }
 
-trait DspComplexImpl {
-  implicit def DspComplexRingImpl[T<: Data:Ring] = new DspComplexRing[T]()
+trait GenericDspComplexImpl {
+  implicit def DspComplexRingDataImpl[T<: Data:Ring] = new DspComplexRingData[T]()
   implicit def DspComplexEq[T <: Data:Eq] = new DspComplexEq[T]()
   implicit def DspComplexBinaryRepresentation[T <: Data:Ring:BinaryRepresentation] = 
     new DspComplexBinaryRepresentation[T]()
 }
+
+trait DspComplexImpl extends GenericDspComplexImpl {
+  implicit def DspComplexRingUIntImpl = new DspComplexRingUInt
+  implicit def DspComplexRingSIntImpl = new DspComplexRingSInt
+  implicit def DspComplexRingFixedImpl = new DspComplexRingFixed
+}

src/test/scala/dsptools/numbers/DspComplexSpec.scala

@@ -1,11 +1,11 @@
 // See LICENSE for license details.
 
-package dsptools.numbers
+package testing.dsptools.numbers
 
 import chisel3._
 import chisel3.iotesters.ChiselPropSpec
 import chisel3.testers.BasicTester
-import dsptools.numbers.implicits._
+import dsptools.numbers._
 
 //scalastyle:off magic.number
 class DspComplexExamples extends Module {