Agnostic multiplier (#125)

* compressor with flopped output

* selectSigned is working for partial product generation

* multiplier documentation update

doc/components/floating_point.md

@@ -16,7 +16,7 @@ $$minExponent <= exponent <= maxExponent$$
 
  And a mantissa in the range of $[1,2)$.  Subnormal numbers are represented with a zero exponent and leading zeros in the mantissa capture the negative exponent value.
 
-The various IEEE constants representing corner cases of the field of floating-point values for a given size of `FloatingPointValue`: infinities, zeros, limits for normal (e.g. mantissa in the range of $[1,2])$ and sub-normal numbers (zero exponent, and mantissa <1).
+The various IEEE constants representing corner cases of the field of floating-point values for a given size of `FloatingPointValue`: infinities, zeros, limits for normal (e.g. mantissa in the range of $[1,2)$ and sub-normal numbers (zero exponent, and mantissa <1).
 
 Appropriate string representations, comparison operations, and operators are available.  The usefulness of `FloatingPointValue` is in the testing of `FloatingPoint` components, where we can leverage the abstraction of a floating-point value type to drive and compare floating-point values operated upon by floating-point components.
 

doc/components/multiplier.md

@@ -82,10 +82,11 @@ digital signal processing.
 The parameters of the
 `CompressionTreeMultiplier` are:
 
-- Two input terms `a` and `b`
+- Two input terms `a` and `b` which can be different widths
 - The radix used for Booth encoding (2, 4, 8, and 16 are currently supported)
 - The type of `ParallelPrefix` tree used in the final `ParallelPrefixAdder` (optional)
-- Whether the operands should be treated as signed (2s complement) or unsigned
+- `signed` parameter: whether the operands should be treated as signed (2s complement) or unsigned
+- An optional `selectSigned` control signal which overrides the `signed` configuration allowing for runtime control of signed or unsigned operation with the same hardware.
 
 Here is an example of use of the `CompressionTreeMultiplier`:
 
@@ -116,11 +117,12 @@ tree to allow for accumulation into this third input.
 The parameters of the
 `CompressionTreeMultiplyAccumulate` are:
 
-- Two input terms a and b
-- The accumulate input term c
+- Two input product terms `a` and `b` which can be different widths
+- The accumulate input term `c` which must have width as sum of the two operand widths + 1.
 - The radix used for Booth encoding (2, 4, 8, and 16 are currently supported)
-- The type of `ParallelPrefix` tree used in the final `ParallelPrefixAdder` (optional)
-- Whether the operands should be treated as signed (2s complement) or unsigned
+- The type of `ParallelPrefix` tree used in the final `ParallelPrefixAdder` (default Kogge-Stone).
+- `signed` parameter: whether the operands should be treated as signed (2s complement) or unsigned
+- An optional `selectSigned` control signal which overrides the `signed` configuration allowing for runtime control of signed or unsigned operation with the same hardware.
 
 Here is an example of using the `CompressionTreeMultiplyAccumulate`:
 

lib/src/arithmetic/evaluate_partial_product.dart

@@ -25,7 +25,11 @@ extension EvaluateLivePartialProduct on PartialProductGenerator {
       }
     }
     final sum = LogicValue.ofBigInt(accum, maxW).toBigInt();
-    return signed ? sum.toSigned(maxW) : sum;
+    return signed
+        ? sum.toSigned(maxW)
+        : (selectSigned != null && !selectSigned!.value.isZero)
+            ? sum.toSigned(maxW)
+            : sum;
   }
 
   /// Print out the partial product matrix

lib/src/arithmetic/multiplicand_selector.dart

@@ -28,17 +28,31 @@ class MultiplicandSelector {
   late LogicArray multiples;
 
   /// Generate required multiples of multiplicand
-  MultiplicandSelector(this.radix, this.multiplicand, {required bool signed})
+  MultiplicandSelector(this.radix, this.multiplicand,
+      {Logic? selectSigned, bool signed = false})
       : shift = log2Ceil(radix) {
+    if (signed && (selectSigned != null)) {
+      throw RohdHclException('sign reconfiguration requires signed=false');
+    }
     if (radix > 16) {
       throw RohdHclException('Radices beyond 16 are not yet supported');
     }
     final width = multiplicand.width + shift;
     final numMultiples = radix ~/ 2;
     multiples = LogicArray([numMultiples], width);
-    final extendedMultiplicand = signed
-        ? multiplicand.signExtend(width)
-        : multiplicand.zeroExtend(width);
+    final Logic extendedMultiplicand;
+    if (selectSigned == null) {
+      extendedMultiplicand = signed
+          ? multiplicand.signExtend(width)
+          : multiplicand.zeroExtend(width);
+    } else {
+      final len = multiplicand.width;
+      final sign = multiplicand[len - 1];
+      final extension = [
+        for (var i = len; i < width; i++) mux(selectSigned, sign, Const(0))
+      ];
+      extendedMultiplicand = (multiplicand.elements + extension).rswizzle();
+    }
 
     for (var pos = 0; pos < numMultiples; pos++) {
       final ratio = pos + 1;

lib/src/arithmetic/multiplier.dart

@@ -11,6 +11,7 @@
 import 'package:meta/meta.dart';
 import 'package:rohd/rohd.dart';
 import 'package:rohd_hcl/rohd_hcl.dart';
+import 'package:rohd_hcl/src/arithmetic/partial_product_sign_extend.dart';
 
 /// An abstract class for all multiplier implementations.
 abstract class Multiplier extends Module {
@@ -72,10 +73,20 @@ class CompressionTreeMultiplier extends Multiplier {
   @override
   Logic get product => output('product');
 
-  /// Construct a compression tree integer multipler with
-  ///   a given radix and final adder functor
+  /// Construct a compression tree integer multiplier with a given [radix]
+  /// and prefix tree functor [ppTree] for the compressor and final adder.
+  ///
+  /// [a] and [b] are the product terms and they can be different widths
+  /// allowing for rectangular multiplication.
+  ///
+  /// [signed] parameter configures the multiplier as a signed multiplier
+  /// (default is unsigned).
+  ///
+  /// Optional [selectSigned] allows for runtime configuration of signed
+  /// or unsigned operation, overriding the [signed] static configuration.
   CompressionTreeMultiplier(super.a, super.b, int radix,
-      {ParallelPrefix Function(List<Logic>, Logic Function(Logic, Logic))
+      {Logic? selectSigned,
+      ParallelPrefix Function(List<Logic>, Logic Function(Logic, Logic))
           ppTree = KoggeStone.new,
       super.signed = false})
       : super(
@@ -86,7 +97,7 @@ class CompressionTreeMultiplier extends Multiplier {
     final product = addOutput('product', width: a.width + b.width);
     final pp = PartialProductGeneratorCompactRectSignExtension(
         a, b, RadixEncoder(radix),
-        signed: signed);
+        selectSigned: selectSigned, signed: signed);
 
     final compressor = ColumnCompressor(pp)..compress();
     final adder = ParallelPrefixAdder(
@@ -96,16 +107,26 @@ class CompressionTreeMultiplier extends Multiplier {
   }
 }
 
-/// An implementation of an integer multiply accumulate using compression trees
+/// An implementation of an integer multiply-accumulate using compression trees
 class CompressionTreeMultiplyAccumulate extends MultiplyAccumulate {
   /// The final product of the multiplier module.
   @override
   Logic get accumulate => output('accumulate');
 
-  /// Construct a compression tree integer multipler with
-  ///   a given radix and final adder functor
+  /// Construct a compression tree integer multiply-add with a given [radix]
+  /// and prefix tree functor [ppTree] for the compressor and final adder.
+  ///
+  /// [a] and [b] are the product terms, [c] is the accumulate term which
+  /// must be the sum of the widths plus 1.
+  ///
+  /// [signed] parameter configures the multiplier as a signed multiplier
+  /// (default is unsigned).
+  ///
+  /// Optional [selectSigned] allows for runtime configuration of signed
+  /// or unsigned operation, overriding the [signed] static configuration.
   CompressionTreeMultiplyAccumulate(super.a, super.b, super.c, int radix,
       {required super.signed,
+      Logic? selectSigned,
       ParallelPrefix Function(List<Logic>, Logic Function(Logic, Logic))
           ppTree = KoggeStone.new})
       : super(
@@ -114,7 +135,7 @@ class CompressionTreeMultiplyAccumulate extends MultiplyAccumulate {
     final accumulate = addOutput('accumulate', width: a.width + b.width + 1);
     final pp = PartialProductGeneratorCompactRectSignExtension(
         a, b, RadixEncoder(radix),
-        signed: signed);
+        selectSigned: selectSigned, signed: signed);
 
     // TODO(desmonddak): This sign extension method for the additional
     //  addend may only work with CompactRectSignExtension
@@ -151,7 +172,7 @@ class MutiplyOnly extends MultiplyAccumulate {
   Logic get accumulate => output('accumulate');
 
   /// Construct a MultiplyAccumulate that only multiplies to enable
-  /// using the same tester with zero addend.
+  /// using the same tester with zero accumulate addend [c].
   MutiplyOnly(super.a, super.b, super.c,
       Multiplier Function(Logic a, Logic b) multiplyGenerator,
       {super.signed = false}) // Will be overrwridden by multiplyGenerator

lib/src/arithmetic/multiplier_encoder.dart

@@ -76,8 +76,8 @@ class RadixEncoder {
       ].swizzle().and());
     }
 
-    return RadixEncode._(
-        multiples.rswizzle(), multiplierSlice[multiplierSlice.width - 1]);
+    return RadixEncode._(multiples.rswizzle(),
+        multiples.rswizzle().or() & multiplierSlice[multiplierSlice.width - 1]);
   }
 }
 
@@ -97,9 +97,12 @@ class MultiplierEncoder {
 
   /// Generate an encoding of the input multiplier
   MultiplierEncoder(this.multiplier, RadixEncoder radixEncoder,
-      {required bool signed})
+      {Logic? selectSigned, bool signed = false})
       : _encoder = radixEncoder,
         _sliceWidth = log2Ceil(radixEncoder.radix) + 1 {
+    if (signed && (selectSigned != null)) {
+      throw RohdHclException('sign reconfiguration requires signed=false');
+    }
     // Unsigned encoding wants to overlap past the multipler
     if (signed) {
       rows =
@@ -109,10 +112,20 @@ class MultiplierEncoder {
       rows = (((multiplier.width + 1) % (_sliceWidth - 1) == 0) ? 0 : 1) +
           ((multiplier.width + 1) ~/ log2Ceil(radixEncoder.radix));
     }
-    // slices overlap by 1 and start at -1
-    _extendedMultiplier = (signed
-        ? multiplier.signExtend(rows * (_sliceWidth - 1))
-        : multiplier.zeroExtend(rows * (_sliceWidth - 1)));
+    // slices overlap by 1 and start at -1a
+    if (selectSigned == null) {
+      _extendedMultiplier = (signed
+          ? multiplier.signExtend(rows * (_sliceWidth - 1))
+          : multiplier.zeroExtend(rows * (_sliceWidth - 1)));
+    } else {
+      final len = multiplier.width;
+      final sign = multiplier[len - 1];
+      final extension = [
+        for (var i = len - 1; i < (rows * (_sliceWidth - 1)); i++)
+          mux(selectSigned, sign, Const(0))
+      ];
+      _extendedMultiplier = (multiplier.elements + extension).rswizzle();
+    }
   }
 
   /// Retrieve the Booth encoding for the row