cleanup of API making more methods private, fixing SignMag adder API

lib/src/arithmetic/adder.dart

@@ -30,10 +30,6 @@ abstract class Adder extends Module {
   /// The addition results [sum] including carry bit
   Logic get sum => output('sum');
 
-  /// Implementation needs to provide a method for calculating the full sum
-  @protected
-  Logic calculateSum();
-
   /// Implementation needs to provide a method for calculating the sum
   /// without carry
   @protected
@@ -57,7 +53,7 @@ abstract class Adder extends Module {
 
     out <= calculateOut();
     carryOut <= calculateCarry();
-    sum <= calculateSum();
+    sum <= [carryOut, out].swizzle();
   }
 }
 

lib/src/arithmetic/multiplier.dart

@@ -60,7 +60,7 @@ abstract class MultiplyAccumulate extends Module {
   /// Take input [a] and input [b], compute their
   /// product, add input [c] to produce the [accumulate] result.
   MultiplyAccumulate(Logic a, Logic b, Logic c,
-      {this.signed = false, super.name}) {
+      {required this.signed, super.name}) {
     this.a = addInput('a', a, width: a.width);
     this.b = addInput('b', b, width: b.width);
     this.c = addInput('c', c, width: c.width);
@@ -103,7 +103,7 @@ class CompressionTreeMultiplyAccumulate extends MultiplyAccumulate {
   ///   a given radix and final adder functor
   CompressionTreeMultiplyAccumulate(super.a, super.b, super.c, int radix,
       ParallelPrefix Function(List<Logic>, Logic Function(Logic, Logic)) ppTree,
-      {super.signed = false})
+      {required super.signed})
       : super(
             name: 'Compression Tree Multiply Accumulate: '
                 'R${radix}_${ppTree.call([Logic()], (a, b) => Logic()).name}') {
@@ -154,7 +154,8 @@ class MutiplyOnly extends MultiplyAccumulate {
   /// Construct a MultiplyAccumulate that only multiplies to enable
   /// using the same tester with zero addend.
   MutiplyOnly(super.a, super.b, super.c,
-      Multiplier Function(Logic a, Logic b) multiplyGenerator)
+      Multiplier Function(Logic a, Logic b) multiplyGenerator,
+      {super.signed = false}) // Will be overrwridden by multiplyGenerator
       : super(name: 'Multiply Only: ${multiplyGenerator.call(a, b).name}') {
     final accumulate = addOutput('accumulate', width: a.width + b.width + 1);
 

lib/src/arithmetic/parallel_prefix_operations.dart

@@ -237,10 +237,6 @@ class ParallelPrefixAdder extends Adder {
   @override
   @protected
   Logic calculateCarry() => _carry;
-
-  @override
-  @protected
-  Logic calculateSum() => [_carry, _out].swizzle();
 }
 
 /// Incrementer based on ParallelPrefix tree

lib/src/arithmetic/partial_product_generator.dart

@@ -91,13 +91,13 @@ class PartialProductGenerator {
       case SignExtension.none:
         ;
       case SignExtension.brute:
-        bruteForceSignExtend();
+        _bruteForceSignExtend();
       case SignExtension.stop:
-        signExtendWithStopBitsRect();
+        _signExtendWithStopBitsRect();
       case SignExtension.compact:
-        signExtendCompact();
+        _signExtendCompact();
       case SignExtension.compactRect:
-        signExtendCompactRect();
+        _signExtendCompactRect();
     }
   }
 
@@ -114,7 +114,7 @@ class PartialProductGenerator {
   }
 
   /// Fully sign extend the PP array: useful for reference only
-  void bruteForceSignExtend() {
+  void _bruteForceSignExtend() {
     if (_signExtended) {
       throw RohdHclException('Partial Product array already sign-extended');
     }
@@ -142,7 +142,7 @@ class PartialProductGenerator {
   /// enough that carry bit lands outside another row).
   /// This technique can then be combined with a first-row extension technique
   /// for folding in the final carry.
-  void signExtendWithStopBitsRect() {
+  void _signExtendWithStopBitsRect() {
     if (_signExtended) {
       throw RohdHclException('Partial Product array already sign-extended');
     }
@@ -219,7 +219,7 @@ class PartialProductGenerator {
   }
 
   /// Sign extend the PP array using stop bits without adding a row.
-  void signExtendCompact() {
+  void _signExtendCompact() {
     // An implementation of
     // Mohanty, B.K., Choubey, A. Efficient Design for Radix-8 Booth Multiplier
     // and Its Application in Lifting 2-D DWT. Circuits Syst Signal Process 36,
@@ -323,7 +323,7 @@ class PartialProductGenerator {
   /// This routine works with different widths of multiplicand/multiplier,
   /// an extension of Mohanty, B.K., Choubey designed by
   /// Desmond A. Kirkpatrick
-  void signExtendCompactRect() {
+  void _signExtendCompactRect() {
     if (_signExtended) {
       throw RohdHclException('Partial Product array already sign-extended');
     }
@@ -462,7 +462,11 @@ class PartialProductGenerator {
     }
     return maxW;
   }
+}
 
+/// Debug routines for printing out partial product matrix during
+/// simulation with live logic values
+extension EvaluateLivePartialProduct on PartialProductGenerator {
   /// Accumulate the partial products and return as BigInt
   BigInt evaluate() {
     final maxW = maxWidth();
@@ -479,8 +483,7 @@ class PartialProductGenerator {
   }
 
   /// Print out the partial product matrix
-  @override
-  String toString() {
+  String representation() {
     final str = StringBuffer();
 
     final maxW = maxWidth();

lib/src/arithmetic/ripple_carry_adder.dart

@@ -47,8 +47,4 @@ class RippleCarryAdder extends Adder {
   @override
   @protected
   Logic calculateCarry() => _carry;
-
-  @override
-  @protected
-  Logic calculateSum() => [_carry, _out].swizzle();
 }

lib/src/arithmetic/sign_magnitude_adder.dart

@@ -28,12 +28,17 @@ class SignMagnitudeAdder extends Adder {
   /// The sign of the result
   Logic get sign => output('sign');
 
+  /// If largest magnitude negative is first argument, no compare and
+  /// swap is needed.
+  bool largestNegativeFirst;
+
   late final Logic _out;
   late final Logic _carry = Logic();
 
   /// [SignMagnitudeAdder] constructor with an unsigned adder functor
   SignMagnitudeAdder(Logic as, super.a, Logic bs, super.b,
-      Adder Function(Logic, Logic) adderGen)
+      Adder Function(Logic, Logic) adderGen,
+      {this.largestNegativeFirst = false})
       : _out = Logic(width: a.width),
         super(
             name: 'Ones Complement Adder: '
@@ -42,14 +47,17 @@ class SignMagnitudeAdder extends Adder {
     bSign = addInput('bSign', bs);
     final sign = addOutput('sign');
 
+    final computeSign = mux(largestNegativeFirst ? Const(1) : Const(0), aSign,
+        mux(a.lt(b) & aSign, bSign, aSign));
+
     final aOnesComplement = mux(aSign, ~a, a);
     final bOnesComplement = mux(bSign, ~b, b);
 
     final adder = adderGen(aOnesComplement, bOnesComplement);
     final endAround = adder.carryOut & (aSign | bSign);
     final localOut = mux(endAround, adder.sum + 1, adder.sum);
 
-    sign <= aSign;
+    sign <= computeSign;
     _out <= mux(sign, ~localOut, localOut).slice(_out.width - 1, 0);
     _carry <= localOut.slice(localOut.width - 1, localOut.width - 1);
   }
@@ -61,8 +69,4 @@ class SignMagnitudeAdder extends Adder {
   @override
   @protected
   Logic calculateCarry() => _carry;
-
-  @override
-  @protected
-  Logic calculateSum() => [_carry, _out].swizzle();
 }