Support compiling ROHD to JavaScript (#445)

.github/workflows/general.yml

@@ -31,6 +31,11 @@ jobs:
       - name: Setup Dart
         uses: dart-lang/setup-dart@v1
 
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
       - name: Install project dependencies
         run: tool/gh_actions/install_dependencies.sh
 

lib/src/modules/gates.dart

@@ -215,14 +215,7 @@ abstract class _TwoInputBitwiseGate extends Module with InlineSystemVerilog {
 
   /// Executes the functional behavior of this gate.
   void _execute() {
-    dynamic toPut;
-    try {
-      toPut = _op(_in0.value, _in1.value);
-    } on Exception {
-      // in case of things like divide by 0
-      toPut = LogicValue.x;
-    }
-    out.put(toPut);
+    out.put(_op(_in0.value, _in1.value));
   }
 
   @override

lib/src/utilities/simcompare.dart

@@ -14,6 +14,7 @@ import 'dart:io';
 
 import 'package:collection/collection.dart';
 import 'package:rohd/rohd.dart';
+import 'package:rohd/src/utilities/web.dart';
 import 'package:test/test.dart';
 
 /// Represents a single test case to check in a single clock cycle.
@@ -242,6 +243,11 @@ abstract class SimCompare {
     bool maskKnownWarnings = true,
     bool buildOnly = false,
   }) {
+    if (kIsWeb) {
+      // if running in web mode, then we can't run icarus verilog
+      return true;
+    }
+
     String signalDeclaration(String signalName) {
       final signal = module.signals.firstWhere((e) => e.name == signalName);
 

lib/src/utilities/web.dart

@@ -0,0 +1,39 @@
+// Copyright (C) 2021-2023 Intel Corporation
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// web.dart
+// Utilities for running ROHD safely on the web or in JavaScript.
+//
+// 2023 December 8
+// Author: Max Korbel <[email protected]>
+
+import 'dart:math';
+
+import 'package:rohd/rohd.dart';
+
+/// Borrowed from Flutter's implementation to determine whether Dart is
+/// compiled to run on the web.  This is relevant for ROHD because when the
+/// code is compiled to JavaScript, it affects the ability for [LogicValue]
+/// to store different sizes of data in different implementations.
+///
+/// See more details here:
+/// https://api.flutter.dev/flutter/foundation/kIsWeb-constant.html
+// ignore: do_not_use_environment
+const bool kIsWeb = bool.fromEnvironment('dart.library.js_util');
+
+/// The number of bits in an int.
+// ignore: constant_identifier_names
+const int INT_BITS = kIsWeb ? 32 : 64;
+
+/// Calculates the `int` result of `1 << shamt` in a safe way considering
+/// whether it is run in JavaScript or native Dart.
+///
+/// In JavaScript, the shift amount is `&`ed with `0x1f`, so `1 << 32 == 0`.
+int oneSllBy(int shamt) {
+  if (kIsWeb) {
+    assert(shamt <= 52, 'Loss of precision in JavaScript beyond 53 bits.');
+    return pow(2, shamt) as int;
+  } else {
+    return 1 << shamt;
+  }
+}

lib/src/values/big_logic_value.dart

@@ -16,10 +16,12 @@ extension BigLogicValueBigIntUtilities on BigInt {
   ///
   /// Always interprets the number as unsigned, and thus never clamps to fit.
   int toIntUnsigned(int width) {
-    if (width > LogicValue._INT_BITS) {
+    if (width > INT_BITS) {
       throw Exception('Cannot convert Int when width $width'
-          ' is greater than ${LogicValue._INT_BITS}');
-    } else if (width == LogicValue._INT_BITS) {
+          ' is greater than $INT_BITS');
+    } else if (width == INT_BITS && INT_BITS > 32) {
+      assert(!kIsWeb, 'This code is not set up to work with JS.');
+
       // When width is 64, `BigInt.toInt()` will clamp values assuming that
       // it's a signed number.  To avoid that, if the width is 64, then do the
       // conversion in two 32-bit chunks and bitwise-or them together.
@@ -28,7 +30,9 @@ extension BigLogicValueBigIntUtilities on BigInt {
       return (this & mask).toInt() |
           (((this >> maskWidth) & mask).toInt() << maskWidth);
     } else {
-      return toInt();
+      return (this & _BigLogicValue._maskOfWidth(width))
+          .toInt()
+          .toSigned(INT_BITS);
     }
   }
 }
@@ -52,13 +56,13 @@ class _BigLogicValue extends LogicValue {
   }
 
   /// Constructs a new [_BigLogicValue], intended to hold values
-  /// with more than [_INT_BITS] bits.
+  /// with more than [INT_BITS] bits.
   ///
   /// Set [allowInefficientRepresentation] to `true` to bypass
   /// inefficient representation assertions.
   _BigLogicValue(BigInt value, BigInt invalid, int width,
       {bool allowInefficientRepresentation = false})
-      : assert(width > LogicValue._INT_BITS,
+      : assert(width > INT_BITS,
             '_BigLogicValue should only be used for large values'),
         super._(width) {
     _value = (_mask & value).toUnsigned(width);
@@ -95,7 +99,7 @@ class _BigLogicValue extends LogicValue {
   @override
   LogicValue _getRange(int start, int end) {
     final newWidth = end - start;
-    if (newWidth > LogicValue._INT_BITS) {
+    if (newWidth > INT_BITS) {
       return LogicValue._bigLogicValueOrFilled(
           (_value >> start) & _maskOfWidth(newWidth),
           (_invalid >> start) & _maskOfWidth(newWidth),
@@ -130,7 +134,7 @@ class _BigLogicValue extends LogicValue {
   int toInt() {
     final bigInt = toBigInt();
     if (bigInt.isValidInt) {
-      return bigInt.toIntUnsigned(LogicValue._INT_BITS);
+      return bigInt.toIntUnsigned(INT_BITS).toSigned(INT_BITS);
     } else {
       throw InvalidTruncationException(
           'LogicValue $this is too long to convert to int.'
@@ -241,4 +245,7 @@ class _BigLogicValue extends LogicValue {
 
   @override
   int get _intValue => _value.toIntUnsigned(width);
+
+  @override
+  late final bool isZero = _value == BigInt.zero && _invalid == BigInt.zero;
 }

lib/src/values/filled_logic_value.dart

@@ -94,7 +94,7 @@ class _FilledLogicValue extends LogicValue {
       return 0;
     } else if (!isValid) {
       throw InvalidValueOperationException(this, 'toInt');
-    } else if (width > LogicValue._INT_BITS) {
+    } else if (width > INT_BITS) {
       throw InvalidTruncationException(
           'LogicValue $this is too long to convert to int.'
           ' Use toBigInt() instead.');
@@ -340,4 +340,7 @@ class _FilledLogicValue extends LogicValue {
       (_value == _LogicValueEnum.one || _value == _LogicValueEnum.z)
           ? _SmallLogicValue._maskOfWidth(width)
           : 0;
+
+  @override
+  bool get isZero => _value == _LogicValueEnum.zero;
 }