Fixes and improvements related to shifts (#412)

lib/src/exceptions/exceptions.dart

@@ -9,3 +9,4 @@ export './module/module_exceptions.dart';
 export './name/name_exceptions.dart';
 export './sim_compare/sim_compare_exceptions.dart';
 export 'rohd_exception.dart';
+export 'unsupported_type_exception.dart';

lib/src/exceptions/logic_value/value_width_mismatch_exception.dart

@@ -15,6 +15,6 @@ class ValueWidthMismatchException extends RohdException {
   /// Creates an exception when two [LogicValue] considered for the operation
   /// are of different width.
   ValueWidthMismatchException(LogicValue a, LogicValue b)
-      : super('Width Mismatch ${a.width} & ${b.width}: '
-            'LogicValue must be of same width');
+      : super('Width mismatch between $a (${a.width}) & $b (${b.width}): '
+            'LogicValues must be of same width for this operation.');
 }

lib/src/exceptions/sim_compare/non_supported_type_exception.dart

@@ -18,7 +18,7 @@ class NonSupportedTypeException extends RohdException {
   /// with default error [message].
   ///
   /// Creates a [NonSupportedTypeException] with an optional error [message].
-  NonSupportedTypeException(String vector,
+  NonSupportedTypeException(dynamic vector,
       [String message = 'The runtimetype of expected vector is unsupported: '])
-      : super(message + vector.runtimeType.toString());
+      : super('$message $vector (${vector.runtimeType})');
 }

lib/src/exceptions/unsupported_type_exception.dart

@@ -0,0 +1,18 @@
+// Copyright (C) 2023 Intel Corporation
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// unsupported_type_exception.dart
+// An exception that is thrown when an unsupported type is used.
+//
+// 2023 September 14
+// Author: Max Korbel <max.korbel@intel.com
+
+import 'package:rohd/src/exceptions/rohd_exception.dart';
+
+/// An exception that is thrown when an unsupported type is used.
+class UnsupportedTypeException extends RohdException {
+  /// Creates an exception when an unsupported type is used.
+  UnsupportedTypeException(dynamic value, List<Type> supportedTypes)
+      : super('Unsupported type ${value.runtimeType} used ($value).'
+            ' Supported types are ${supportedTypes.join(',')}');
+}

lib/src/modules/gates.dart

@@ -351,7 +351,7 @@ class _ShiftGate extends Module with InlineSystemVerilog {
       : super(name: name) {
     final shiftAmountLogic = shiftAmount is Logic
         ? shiftAmount
-        : Const(shiftAmount, width: in_.width);
+        : Const(LogicValue.ofInferWidth(shiftAmount));
 
     _inName = Module.unpreferredName('in_${in_.name}');
     _shiftAmountName =

lib/src/utilities/simcompare.dart

@@ -47,15 +47,22 @@ class Vector {
   /// the [inputValues].
   static String _errorCheckString(String sigName, dynamic expected,
       LogicValue expectedVal, String inputValues) {
-    final expectedHexStr = expected is int
-        ? '0x${expected.toRadixString(16)}'
-        : expected.toString();
-    final expectedValStr = expectedVal.toString();
+    if (expected is! int && expected is! LogicValue && expected is! BigInt) {
+      throw NonSupportedTypeException(expected);
+    }
 
-    if (expected is! int && expected is! LogicValue) {
-      throw Exception(
-          'Support for ${expected.runtimeType} is not supported (yet?).');
+    String expectedHexStr;
+    if (expected is int) {
+      expectedHexStr =
+          BigInt.from(expected).toUnsigned(expectedVal.width).toRadixString(16);
+    } else if (expected is BigInt) {
+      expectedHexStr = expected.toUnsigned(expectedVal.width).toRadixString(16);
+    } else {
+      expectedHexStr = expected.toString();
     }
+    expectedHexStr = '0x$expectedHexStr';
+
+    final expectedValStr = expectedVal.toString();
 
     return 'if($sigName !== $expectedValStr) '
         '\$error(\$sformatf("Expected $sigName=$expectedHexStr,'
@@ -80,7 +87,11 @@ class Vector {
         }
         return arrAssigns.toString();
       } else {
-        return '$signalName = ${inputValues[signalName]};';
+        var assignmentValue = inputValues[signalName];
+        if (assignmentValue is BigInt) {
+          assignmentValue = LogicValue.of(assignmentValue, width: signal.width);
+        }
+        return '$signalName = $assignmentValue;';
       }
     }).join('\n');
 
@@ -151,7 +162,12 @@ abstract class SimCompare {
                   ' expected $o to be $value, but it was ${o.value}.';
               if (value is int) {
                 expect(o.value.isValid, isTrue, reason: errorReason);
-                expect(o.value.toInt(), equals(value), reason: errorReason);
+                expect(o.value.toBigInt(),
+                    equals(BigInt.from(value).toUnsigned(o.width)),
+                    reason: errorReason);
+              } else if (value is BigInt) {
+                expect(o.value.isValid, isTrue, reason: errorReason);
+                expect(o.value.toBigInt(), equals(value), reason: errorReason);
               } else if (value is LogicValue) {
                 if (o.width > 1 &&
                     (value == LogicValue.x || value == LogicValue.z)) {
@@ -162,7 +178,7 @@ abstract class SimCompare {
                   expect(o.value, equals(value), reason: errorReason);
                 }
               } else {
-                throw NonSupportedTypeException(value.runtimeType.toString());
+                throw NonSupportedTypeException(value);
               }
             }
           }).catchError(

lib/src/values/big_logic_value.dart

@@ -42,7 +42,7 @@ class _BigLogicValue extends LogicValue {
   late final BigInt _invalid;
 
   BigInt get _mask => _maskOfWidth(width);
-  static final Map<int, BigInt> _masksOfWidth = {};
+  static final Map<int, BigInt> _masksOfWidth = HashMap();
   static BigInt _maskOfWidth(int width) {
     if (!_masksOfWidth.containsKey(width)) {
       _masksOfWidth[width] =
@@ -121,15 +121,22 @@ class _BigLogicValue extends LogicValue {
   @override
   BigInt toBigInt() {
     if (_invalid.sign != 0) {
-      throw Exception('Cannot convert invalid LogicValue to BigInt: $this');
+      throw InvalidValueOperationException(this, 'toBigInt');
     }
     return _value;
   }
 
   @override
-  int toInt() =>
-      throw Exception('LogicValue width $width is too long to convert to int.'
+  int toInt() {
+    final bigInt = toBigInt();
+    if (bigInt.isValidInt) {
+      return bigInt.toIntUnsigned(LogicValue._INT_BITS);
+    } else {
+      throw InvalidTruncationException(
+          'LogicValue $this is too long to convert to int.'
           ' Use toBigInt() instead.');
+    }
+  }
 
   @override
   LogicValue operator ~() => LogicValue._bigLogicValueOrFilled(
@@ -197,28 +204,34 @@ class _BigLogicValue extends LogicValue {
   }
 
   @override
-  LogicValue _shiftLeft(int shamt) => !isValid
-      ? _FilledLogicValue(_LogicValueEnum.x, width)
-      : LogicValue._bigLogicValueOrFilled(
-          (_value << shamt) & _mask, (_invalid << shamt) & _mask, width);
+  LogicValue _shiftLeft(int shamt) => LogicValue._bigLogicValueOrFilled(
+      (_value << shamt) & _mask, (_invalid << shamt) & _mask, width);
 
   @override
-  LogicValue _shiftRight(int shamt) => !isValid
-      ? _FilledLogicValue(_LogicValueEnum.x, width)
-      : LogicValue._bigLogicValueOrFilled(
-          _value >> shamt, _invalid >> shamt, width);
+  LogicValue _shiftRight(int shamt) => LogicValue._bigLogicValueOrFilled(
+      // we can just use >> because these are unsigned
+      _value >> shamt,
+      _invalid >> shamt,
+      width);
 
   @override
-  LogicValue _shiftArithmeticRight(int shamt) => !isValid
-      ? _FilledLogicValue(_LogicValueEnum.x, width)
-      : LogicValue._bigLogicValueOrFilled(
-          (_value |
-                  (this[width - 1] == LogicValue.one
-                      ? ((_mask >> (width - shamt)) << (width - shamt))
-                      : BigInt.zero)) >>
-              shamt,
-          _invalid >> shamt,
-          width);
+  LogicValue _shiftArithmeticRight(int shamt) {
+    shamt;
+
+    var value = (_value.toSigned(width) >> shamt).toUnsigned(width);
+    var invalid = (_invalid.toSigned(width) >> shamt).toUnsigned(width);
+
+    // if uppermost bit is invalid, then turn the shifted bits into X's
+    if (!this[-1].isValid) {
+      // for affected bits of value: zero out value
+      value &= _mask >> shamt;
+
+      // for affected bits of invalid: make sure they are high
+      invalid |= ~_mask >> shamt;
+    }
+
+    return LogicValue._bigLogicValueOrFilled(value, invalid, width);
+  }
 
   @override
   BigInt get _bigIntInvalid => _invalid;

lib/src/values/filled_logic_value.dart

@@ -73,8 +73,7 @@ class _FilledLogicValue extends LogicValue {
   int get _hashCode => _value.hashCode;
 
   @override
-  bool get isValid =>
-      !(_value == _LogicValueEnum.x || _value == _LogicValueEnum.z);
+  bool get isValid => _value.isValid;
 
   @override
   bool get isFloating => _value == _LogicValueEnum.z;
@@ -86,21 +85,24 @@ class _FilledLogicValue extends LogicValue {
     } else if (_value == _LogicValueEnum.zero) {
       return BigInt.zero;
     }
-    throw Exception('Cannot convert invalid value "$_value" to BigInt.');
+    throw InvalidValueOperationException(this, 'toBigInt');
   }
 
   @override
   int toInt() {
-    if (width > LogicValue._INT_BITS) {
-      throw Exception('LogicValue width $width is too long to convert to int.'
+    if (_value == _LogicValueEnum.zero) {
+      return 0;
+    } else if (!isValid) {
+      throw InvalidValueOperationException(this, 'toInt');
+    } else if (width > LogicValue._INT_BITS) {
+      throw InvalidTruncationException(
+          'LogicValue $this is too long to convert to int.'
           ' Use toBigInt() instead.');
-    }
-    if (_value == _LogicValueEnum.one) {
+    } else if (_value == _LogicValueEnum.one) {
       return _SmallLogicValue._maskOfWidth(width);
-    } else if (_value == _LogicValueEnum.zero) {
-      return 0;
     }
-    throw Exception('Cannot convert invalid value "$_value" to an int.');
+
+    throw InvalidValueOperationException(this, 'toInt');
   }
 
   @override
@@ -289,10 +291,6 @@ class _FilledLogicValue extends LogicValue {
       return this;
     }
 
-    if (shamt >= width) {
-      return _FilledLogicValue(_LogicValueEnum.zero, width);
-    }
-
     return [
       getRange(0, width - shamt),
       _FilledLogicValue(_LogicValueEnum.zero, shamt),
@@ -305,18 +303,19 @@ class _FilledLogicValue extends LogicValue {
       return this;
     }
 
-    if (shamt >= width) {
-      return _FilledLogicValue(_LogicValueEnum.zero, width);
-    }
-
     return [
       _FilledLogicValue(_LogicValueEnum.zero, shamt),
-      getRange(shamt, width),
+      _getRange(shamt, width),
     ].swizzle();
   }
 
   @override
-  LogicValue _shiftArithmeticRight(int shamt) => this;
+  LogicValue _shiftArithmeticRight(int shamt) => _value != _LogicValueEnum.z
+      ? this
+      : [
+          _FilledLogicValue(_LogicValueEnum.x, shamt),
+          _getRange(shamt, width),
+        ].swizzle();
 
   @override
   BigInt get _bigIntInvalid =>