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Avoid Module creation for Constant Gate scenarios #481

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52 changes: 49 additions & 3 deletions lib/src/signals/logic.dart
Original file line number Diff line number Diff line change
Expand Up @@ -319,13 +319,59 @@ class Logic {
void operator <=(Logic other) => gets(other);

/// Logical bitwise NOT.
Logic operator ~() => NotGate(this).out;
Logic operator ~() {
if (this is Const) {
if (value.isValid) {
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I think we can rely on the operators within LogicValue for this? i.e. something like Const(~this.value)?

if (value == LogicValue.of(0, width: width)) {
return Const(LogicValue.filled(width, LogicValue.one));
} else if (value == LogicValue.filled(width, LogicValue.one)) {
return Const(LogicValue.of(0, width: width));
}
} else {
return Const(LogicValue.x, width: width);
}
}
return NotGate(this).out;
}

/// Logical bitwise AND.
Logic operator &(Logic other) => And2Gate(this, other).out;
Logic operator &(Logic other) {
if (this is Const || other is Const) {
if (value.isValid && other.value.isValid) {
if (value == LogicValue.of(0, width: width) ||
other.value == LogicValue.of(0, width: width)) {
return Const(LogicValue.of(0, width: width));
} else if (value == LogicValue.filled(width, LogicValue.one)) {
return other;
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What if other is Const and this is not Const but has a value of all 1s currently? Need to be cautious to only consider the value if it's a Const.

} else if (other.value == LogicValue.filled(width, LogicValue.one)) {
return this;
}
} else {
return Const(LogicValue.x, width: width);
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This isn't quite right, consider 11x11 & 11111 == 11x11

If we just cover the cases of all 0's and all 1's that's probably enough and let the rest fall through to the and gate?

}
}
return And2Gate(this, other).out;
}

/// Logical bitwise OR.
Logic operator |(Logic other) => Or2Gate(this, other).out;
Logic operator |(Logic other) {
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same here for or

if (this is Const || other is Const) {
if (value.isValid && other.value.isValid) {
if (value == LogicValue.filled(width, LogicValue.one) ||
other.value == LogicValue.filled(width, LogicValue.one)) {
return Const(LogicValue.filled(width, LogicValue.one));
} else if (value == LogicValue.of(LogicValue.zero, width: width)) {
return other;
} else if (other.value ==
LogicValue.of(LogicValue.zero, width: width)) {
return this;
}
} else {
return Const(LogicValue.x, width: width);
}
}
return Or2Gate(this, other).out;
}

/// Logical bitwise XOR.
Logic operator ^(Logic other) => Xor2Gate(this, other).out;
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103 changes: 103 additions & 0 deletions test/gate_test.dart
Original file line number Diff line number Diff line change
Expand Up @@ -353,6 +353,109 @@ void main() {
});
});

group('Const input Gate test', () {
test('NotGate single bit Constant input', () async {
final a = Logic();
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naming the variables could be helpful for understanding the intent of the test, e.g. normalLogic, const0, etc.

final b = Const(LogicValue.zero, width: 1);
final c = Const(LogicValue.x, width: 1);
final d = Const(LogicValue.one, width: 1);
a.put(LogicValue.one);

final result = ~b;
expect(result, isA<Const>());
expect(result.value, equals(LogicValue.one));

final result2 = ~c;
expect(result2, isA<Const>());
expect(result2.value, equals(LogicValue.x));

final result3 = ~d;
expect(result3, isA<Const>());
expect(result3.value, equals(LogicValue.zero));
});

test('NotGate Multi bit Constant input', () async {
final b = Const(bin('1111'), width: 4);
final c = Const(bin('0100'), width: 4);
final result = ~b;

expect(result, isA<Const>());
expect(result.value, equals(LogicValue.of(LogicValue.zero, width: 4)));

final result2 = ~c;
expect(result2, isA<Logic>());
expect(result2.value, equals(LogicValue.of(11, width: 4)));
});

test('And2Gate Single bit Constant input', () async {
final a = Logic();
final b = Const(LogicValue.zero, width: 1);
final c = Const(LogicValue.x, width: 1);
final d = Const(LogicValue.one, width: 1);
a.put(LogicValue.one);

final result = a & b;
expect(result, isA<Const>());
expect(result.value, equals(LogicValue.zero));

final result2 = a & c;
expect(result2, isA<Const>());
expect(result2.value, equals(LogicValue.x));

final result3 = a & d;
expect(result3, isA<Logic>());
expect(result3.value, equals(a.value));
});

test('And2Gate Multi bit Constant input', () async {
final a = Const(LogicValue.of(LogicValue.zero, width: 4));
final b = Const(bin('1111'), width: 4);
final c = Const(bin('0100'), width: 4);
final result = a & c;

expect(result, isA<Const>());
expect(result.value, equals(LogicValue.of(LogicValue.zero, width: 4)));

final result2 = b & c;
expect(result2, isA<Logic>());
expect(result2.value, equals(c.value));
});

test('OR2Gate Single bit Constant input', () async {
final a = Logic();
final b = Const(LogicValue.zero, width: 1);
final c = Const(LogicValue.x, width: 1);
final d = Const(LogicValue.one, width: 1);
a.put(LogicValue.one);

final result = a | b;
expect(result, isA<Logic>());
expect(result.value, equals(a.value));

final result2 = a | c;
expect(result2, isA<Const>());
expect(result2.value, equals(LogicValue.x));

final result3 = a | d;
expect(result3, isA<Const>());
expect(result3.value, equals(LogicValue.one));
});

test('OR2Gate Multi bit Constant input', () async {
final a = Const(LogicValue.of(LogicValue.zero, width: 4));
final b = Const(bin('1111'), width: 4);
final c = Const(bin('0100'), width: 4);
final result = a | c;

expect(result, isA<Logic>());
expect(result.value, equals(c.value));

final result2 = b | c;
expect(result2, isA<Const>());
expect(result2.value, equals(LogicValue.filled(4, LogicValue.one)));
});
});

group('simcompare', () {
test('NotGate single bit', () async {
final gtm = GateTestModule(Logic(), Logic());
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