Full set of sign variants (signed/unsigned/selected) for multiplier operands

doc/components/multiplier.md

@@ -82,12 +82,14 @@ digital signal processing.
 The parameters of the
 `CompressionTreeMultiplier` are:
 
-- 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)
-- `signed` parameter: whether the operands should be treated as signed (2s complement) or unsigned
+- 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).
 - `ppGen` parameter: the type of `PartialProductGenerator` to use which has derived classes for different styles of sign extension. In some cases this adds an extra row to hold a sign bit.
-- An optional `selectSigned` control signal which overrides the `signed` configuration allowing for runtime control of signed or unsigned operation with the same hardware. `signed` must be false if using this control signal.
+- `signedMultiplicand` parameter: whether the multiplicand (first arg) should be treated as signed (2s complement) or unsigned.
+- `signedMultiplier` parameter: whether the multiplier (second arg) should be treated as signed (2s complement) or unsigned.
+- An optional `selectSignedMultiplicand` control signal which overrides the `signedMultiplicand` parameter allowing for runtime control of signed or unsigned operation with the same hardware. `signedMultiplicand` must be false if using this control signal.
+- An optional `selectSignedMultiplier` control signal which overrides the `signedMultiplier` parameter allowing for runtime control of signed or unsigned operation with the same hardware. `signedMultiplier` must be false if using this control signal.
 - An optional `clk`, as well as `enable` and `reset` that are used to add a pipestage in the `ColumnCompressor` to allow for pipelined operation.
 
 Here is an example of use of the `CompressionTreeMultiplier`:
@@ -123,9 +125,13 @@ The parameters of the
 - 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` (default Kogge-Stone).
-- `signed` parameter: whether the operands should be treated as signed (2s complement) or unsigned
 - `ppGen` parameter: the type of `PartialProductGenerator` to use which has derived classes for different styles of sign extension. In some cases this adds an extra row to hold a sign bit (default `PartialProductGeneratorCompactRectSignExtension`).
-- An optional `selectSigned` control signal which overrides the `signed` configuration allowing for runtime control of signed or unsigned operation with the same hardware. `signed` must be false if using this control signal.
+- `signedMultiplicand` parameter: whether the multiplicand (first arg) should be treated as signed (2s complement) or unsigned
+- `signedMultiplier` parameter: whether the multiplier (second arg) should be treated as signed (2s complement) or unsigned
+- `signedAddend` parameter: whether the addend (third arg) should be treated as signed (2s complement) or unsigned
+- An optional `selectSignedMultiplicand` control signal which overrides the `signedMultiplicand` parameter allowing for runtime control of signed or unsigned operation with the same hardware. `signedMultiplicand` must be false if using this control signal.
+- An optional `selectSignedMultiplier` control signal which overrides the `signedMultiplier` parameter allowing for runtime control of signed or unsigned operation with the same hardware. `signedMultiplier` must be false if using this control signal.
+- An optional `selectSignedAddend` control signal which overrides the `signedAddend` parameter allowing for runtime control of signed or unsigned operation with the same hardware. `signedAddend` must be false if using this control signal.
 - An optional `clk`, as well as `enable` and `reset` that are used to add a pipestage in the `ColumnCompressor` to allow for pipelined operation.
 
 Here is an example of using the `CompressionTreeMultiplyAccumulate`:

lib/src/arithmetic/carry_save_mutiplier.dart

@@ -42,8 +42,8 @@ class CarrySaveMultiplier extends Multiplier {
   CarrySaveMultiplier(super.a, super.b,
       {required Logic clk,
       required Logic reset,
-      required super.signed,
-      super.name = 'carry_save_multiplier'}) {
+      super.name = 'carry_save_multiplier'})
+      : super(signedMultiplicand: false, signedMultiplier: false) {
     if (a.width != b.width) {
       throw RohdHclException('inputs of a and b should have same width.');
     }

lib/src/arithmetic/evaluate_partial_product.dart

@@ -25,11 +25,9 @@ extension EvaluateLivePartialProduct on PartialProductGenerator {
       }
     }
     final sum = LogicValue.ofBigInt(accum, maxW).toBigInt();
-    return signed
+    return isSignedMultiplicand() | isSignedMultiplier()
         ? sum.toSigned(maxW)
-        : (selectSigned != null && !selectSigned!.value.isZero)
-            ? sum.toSigned(maxW)
-            : sum;
+        : sum;
   }
 
   /// Print out the partial product matrix

lib/src/arithmetic/multiplicand_selector.dart

@@ -12,7 +12,7 @@ import 'package:rohd_hcl/rohd_hcl.dart';
 
 /// A class accessing the multiples of the multiplicand at a position
 class MultiplicandSelector {
-  /// radix of the selector
+  /// The radix of the selector
   int radix;
 
   /// The bit shift of the selector (typically overlaps 1)
@@ -21,17 +21,25 @@ class MultiplicandSelector {
   /// New width of partial products generated from the multiplicand
   int get width => multiplicand.width + shift - 1;
 
-  /// Access the multiplicand
+  /// The base multiplicand from which to generate multiples to select.
   Logic multiplicand = Logic();
 
-  /// Place to store multiples of the multiplicand
+  /// Place to store [multiples] of the [multiplicand] (e.g. *1, *2, *-1, *-2..)
   late LogicArray multiples;
 
-  /// Generate required multiples of multiplicand
+  /// Build a [MultiplicandSelector] generationg required [multiples] of
+  /// [multiplicand] to [select] using a [RadixEncoder] argument.
+  ///
+  /// [multiplicand] is base multiplicand multiplied by Booth encodings of
+  /// the [RadixEncoder] during [select].
+  ///
+  /// [signedMultiplicand] generates a fixed signed selector versus using
+  /// [selectSignedMultiplicand] which is a runtime sign selection [Logic]
+  /// in which case [signedMultiplicand] must be false.
   MultiplicandSelector(this.radix, this.multiplicand,
-      {Logic? selectSigned, bool signed = false})
+      {Logic? selectSignedMultiplicand, bool signedMultiplicand = false})
       : shift = log2Ceil(radix) {
-    if (signed && (selectSigned != null)) {
+    if (signedMultiplicand && (selectSignedMultiplicand != null)) {
       throw RohdHclException('sign reconfiguration requires signed=false');
     }
     if (radix > 16) {
@@ -41,15 +49,16 @@ class MultiplicandSelector {
     final numMultiples = radix ~/ 2;
     multiples = LogicArray([numMultiples], width);
     final Logic extendedMultiplicand;
-    if (selectSigned == null) {
-      extendedMultiplicand = signed
+    if (selectSignedMultiplicand == null) {
+      extendedMultiplicand = signedMultiplicand
           ? 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))
+        for (var i = len; i < width; i++)
+          mux(selectSignedMultiplicand, sign, Const(0))
       ];
       extendedMultiplicand = (multiplicand.elements + extension).rswizzle();
     }