Use JavaScript runtime semantics when constant folding.

lib/compiler/implementation/compile_time_constants.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class Constant implements Hashable {
   const Constant();
 
   bool isNull() => false;
   bool isBool() => false;
   bool isTrue() => false;
   bool isFalse() => false;
   bool isInt() => false;
   bool isDouble() => false;
   bool isNum() => false;
   bool isString() => false;
   bool isList() => false;
   bool isMap() => false;
   bool isConstructedObject() => false;
   bool isFunction() => false;
   /** Returns true if the constant is null, a bool, a number or a string. */
   bool isPrimitive() => false;
   /** Returns true if the constant is a list, a map or a constructed object. */
   bool isObject() => false;
   bool isSentinel() => false;
 
   bool isNaN() => false;
+  bool isMinusZero() => false;
 
   abstract void _writeJsCode(CodeBuffer buffer, ConstantHandler handler);
   /**
     * Unless the constant can be emitted multiple times (as for numbers and
     * strings) adds its canonical name to the buffer.
     */
   abstract void _writeCanonicalizedJsCode(CodeBuffer buffer,
                                           ConstantHandler handler);
   abstract List<Constant> getDependencies();
 }
@@ skipping 149 matching lines @@
       return const DoubleConstant._internal(0.0);
     } else if (value == 1.0) {
       return const DoubleConstant._internal(1.0);
     } else {
       return new DoubleConstant._internal(value);
     }
   }
   const DoubleConstant._internal(this.value);
   bool isDouble() => true;
   bool isNaN() => value.isNaN();
+  // We need to check for the negative sign since -0.0 == 0.0.
+  bool isMinusZero() => value == 0.0 && value.isNegative();
 
   void _writeJsCode(CodeBuffer buffer, ConstantHandler handler) {
     if (value.isNaN()) {
       buffer.add("(0/0)");
     } else if (value == double.INFINITY) {
       buffer.add("(1/0)");
     } else if (value == -double.INFINITY) {
       buffer.add("(-1/0)");
     } else {
       buffer.add("$value");
@@ skipping 17 matching lines @@
   DartString toDartString() => new DartString.literal(value.toString());
 }
 
 class BoolConstant extends PrimitiveConstant {
   factory BoolConstant(value) {
     return value ? new TrueConstant() : new FalseConstant();
   }
   const BoolConstant._internal();
   bool isBool() => true;
 
-  BoolConstant unaryFold(String op) {
-    if (op == "!") return new BoolConstant(!value);
-    return null;
-  }
-
   abstract BoolConstant negate();
 }
 
 class TrueConstant extends BoolConstant {
   final bool value = true;
 
   factory TrueConstant() => const TrueConstant._internal();
   const TrueConstant._internal() : super._internal();
   bool isTrue() => true;
 
@@ skipping 279 matching lines @@
   int hashCode() => _hashCode;
   List<Constant> getDependencies() => fields;
 }
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
  */
 class ConstantHandler extends CompilerTask {
+  final ConstantSystem constantSystem;
+
   /**
    * Contains the initial value of fields. Must contain all static and global
    * initializations of const fields. May contain eagerly compiled values for
    * statics and instance fields.
    */
   final Map<VariableElement, Constant> initialVariableValues;
 
   /** Map from compile-time constants to their JS name. */
   final Map<Constant, String> compiledConstants;
 
   /** The set of variable elements that are in the process of being computed. */
   final Set<VariableElement> pendingVariables;
 
   /** Caches the statics where the initial value cannot be eagerly compiled. */
   final Set<VariableElement> lazyStatics;
 
 
-  ConstantHandler(Compiler compiler)
+  ConstantHandler(Compiler compiler, this.constantSystem)
       : initialVariableValues = new Map<VariableElement, Dynamic>(),
         compiledConstants = new Map<Constant, String>(),
         pendingVariables = new Set<VariableElement>(),
         lazyStatics = new Set<VariableElement>(),
         super(compiler);
   String get name => 'ConstantHandler';
 
   void registerCompileTimeConstant(Constant constant) {
     Function ifAbsentThunk = (() {
       return constant.isFunction()
@@ skipping 98 matching lines @@
       pendingVariables.remove(element);
       return value;
     });
   }
 
   Constant compileNodeWithDefinitions(Node node,
                                       TreeElements definitions,
                                       [bool isConst]) {
     return measure(() {
       assert(node !== null);
-      CompileTimeConstantEvaluator evaluator =
-          new CompileTimeConstantEvaluator(definitions, compiler, isConst);
+      CompileTimeConstantEvaluator evaluator = new CompileTimeConstantEvaluator(
+          constantSystem, definitions, compiler, isConst);
       return evaluator.evaluate(node);
     });
   }
 
   /** Attempts to compile a constant expression. Returns null if not possible */
   Constant tryCompileNodeWithDefinitions(Node node, TreeElements definitions) {
     return measure(() {
       assert(node !== null);
       try {
         TryCompileTimeConstantEvaluator evaluator =
-            new TryCompileTimeConstantEvaluator(definitions, compiler);
+            new TryCompileTimeConstantEvaluator(constantSystem,
+                                                definitions,
+                                                compiler);
         return evaluator.evaluate(node);
       } on CompileTimeConstantError catch (exn) {
         return null;
       }
     });
   }
 
   /**
    * Returns a [List] of static non final fields that need to be initialized.
    * The list must be evaluated in order since the fields might depend on each
@@ skipping 121 matching lines @@
     }
   }
 
   String getJsConstructor(ClassElement element) {
     return compiler.namer.isolatePropertiesAccess(element);
   }
 }
 
 class CompileTimeConstantEvaluator extends AbstractVisitor {
   bool isEvaluatingConstant;
+  final ConstantSystem constantSystem;
   final TreeElements elements;
   final Compiler compiler;
 
-  CompileTimeConstantEvaluator(this.elements, this.compiler, [bool isConst])
+  CompileTimeConstantEvaluator(this.constantSystem,
+                               this.elements,
+                               this.compiler,
+                               [bool isConst])
       : this.isEvaluatingConstant = isConst;
 
   Constant evaluate(Node node) {
     return node.accept(this);
   }
 
   Constant evaluateConstant(Node node) {
     bool oldIsEvaluatingConstant = isEvaluatingConstant;
     isEvaluatingConstant = true;
     Constant result = node.accept(this);
     isEvaluatingConstant = oldIsEvaluatingConstant;
     assert(result != null);
     return result;
   }
 
   Constant visitNode(Node node) {
     return signalNotCompileTimeConstant(node);
   }
 
   Constant visitLiteralBool(LiteralBool node) {
-    return new BoolConstant(node.value);
+    return constantSystem.createBool(node.value);
   }
 
   Constant visitLiteralDouble(LiteralDouble node) {
-    return new DoubleConstant(node.value);
+    return constantSystem.createDouble(node.value);
   }
 
   Constant visitLiteralInt(LiteralInt node) {
-    return new IntConstant(node.value);
+    return constantSystem.createInt(node.value);
   }
 
   Constant visitLiteralList(LiteralList node) {
     if (!node.isConst())  {
       return signalNotCompileTimeConstant(node);
     }
     List<Constant> arguments = <Constant>[];
     for (Link<Node> link = node.elements.nodes;
          !link.isEmpty();
          link = link.tail) {
@@ skipping 47 matching lines @@
     classElement.ensureResolved(compiler);
     // TODO(floitsch): copy over the generic type.
     DartType type = new InterfaceType(classElement);
     compiler.registerInstantiatedClass(classElement);
     Constant constant = new MapConstant(type, keysList, values, protoValue);
     compiler.constantHandler.registerCompileTimeConstant(constant);
     return constant;
   }
 
   Constant visitLiteralNull(LiteralNull node) {
-    return new NullConstant();
+    return constantSystem.createNull();
   }
 
   Constant visitLiteralString(LiteralString node) {
-    return new StringConstant(node.dartString, node);
+    return constantSystem.createString(node.dartString, node);
   }
 
   Constant visitStringJuxtaposition(StringJuxtaposition node) {
     StringConstant left = evaluate(node.first);
     StringConstant right = evaluate(node.second);
     if (left == null || right == null) return null;
-    return new StringConstant(new DartString.concat(left.value, right.value),
-                              node);
+    return constantSystem.createString(
+        new DartString.concat(left.value, right.value), node);
   }
 
   Constant visitStringInterpolation(StringInterpolation node) {
     StringConstant initialString = evaluate(node.string);
     if (initialString == null) return null;
     DartString accumulator = initialString.value;
     for (StringInterpolationPart part in node.parts) {
       Constant expression = evaluate(part.expression);
       DartString expressionString;
       if (expression.isNum() || expression.isBool()) {
         PrimitiveConstant primitive = expression;
         expressionString = new DartString.literal(primitive.value.toString());
       } else if (expression.isString()) {
         PrimitiveConstant primitive = expression;
         expressionString = primitive.value;
       } else {
         return signalNotCompileTimeConstant(part.expression);
       }
       accumulator = new DartString.concat(accumulator, expressionString);
       StringConstant partString = evaluate(part.string);
       if (partString == null) return null;
       accumulator = new DartString.concat(accumulator, partString.value);
     };
-    return new StringConstant(accumulator, node);
+    return constantSystem.createString(accumulator, node);
   }
 
   // TODO(floitsch): provide better error-messages.
   Constant visitSend(Send send) {
     Element element = elements[send];
     if (Elements.isStaticOrTopLevelField(element)) {
       Constant result;
       if (element.modifiers !== null) {
         if (element.modifiers.isConst()) {
           result = compiler.compileConstant(element);
@@ skipping 12 matching lines @@
       compiler.constantHandler.registerCompileTimeConstant(constant);
       return constant;
     } else if (send.isPrefix) {
       assert(send.isOperator);
       Constant receiverConstant = evaluate(send.receiver);
       if (receiverConstant == null) return null;
       Operator op = send.selector;
       Constant folded;
       switch (op.source.stringValue) {
         case "!":
-          folded = const NotOperation().fold(receiverConstant);
+          folded = constantSystem.not.fold(receiverConstant);
           break;
         case "-":
-          folded = const NegateOperation().fold(receiverConstant);
+          folded = constantSystem.negate.fold(receiverConstant);
           break;
         case "~":
-          folded = const BitNotOperation().fold(receiverConstant);
+          folded = constantSystem.bitNot.fold(receiverConstant);
           break;
         default:
           compiler.internalError("Unexpected operator.", node: op);
           break;
       }
       if (folded === null) return signalNotCompileTimeConstant(send);
       return folded;
     } else if (send.isOperator && !send.isPostfix) {
       assert(send.argumentCount() == 1);
       Constant left = evaluate(send.receiver);
       Constant right = evaluate(send.argumentsNode.nodes.head);
       if (left == null || right == null) return null;
       Operator op = send.selector.asOperator();
       Constant folded = null;
       switch (op.source.stringValue) {
         case "+":
-          folded = const AddOperation().fold(left, right);
+          folded = constantSystem.add.fold(left, right);
           break;
         case "-":
-          folded = const SubtractOperation().fold(left, right);
+          folded = constantSystem.subtract.fold(left, right);
           break;
         case "*":
-          folded = const MultiplyOperation().fold(left, right);
+          folded = constantSystem.multiply.fold(left, right);
           break;
         case "/":
-          folded = const DivideOperation().fold(left, right);
+          folded = constantSystem.divide.fold(left, right);
           break;
         case "%":
-          folded = const ModuloOperation().fold(left, right);
+          folded = constantSystem.modulo.fold(left, right);
           break;
         case "~/":
-          folded = const TruncatingDivideOperation().fold(left, right);
+          folded = constantSystem.truncatingDivide.fold(left, right);
           break;
         case "|":
-          folded = const BitOrOperation().fold(left, right);
+          folded = constantSystem.bitOr.fold(left, right);
           break;
         case "&":
-          folded = const BitAndOperation().fold(left, right);
+          folded = constantSystem.bitAnd.fold(left, right);
           break;
         case "^":
-          folded = const BitXorOperation().fold(left, right);
+          folded = constantSystem.bitXor.fold(left, right);
           break;
         case "||":
-          folded = const BooleanOr().fold(left, right);
+          folded = constantSystem.booleanOr.fold(left, right);
           break;
         case "&&":
-          folded = const BooleanAnd().fold(left, right);
+          folded = constantSystem.booleanAnd.fold(left, right);
           break;
         case "<<":
-          folded = const ShiftLeftOperation().fold(left, right);
+          folded = constantSystem.shiftLeft.fold(left, right);
           break;
         case ">>":
-          folded = const ShiftRightOperation().fold(left, right);
+          folded = constantSystem.shiftRight.fold(left, right);
           break;
         case "<":
-          folded = const LessOperation().fold(left, right);
+          folded = constantSystem.less.fold(left, right);
           break;
         case "<=":
-          folded = const LessEqualOperation().fold(left, right);
+          folded = constantSystem.lessEqual.fold(left, right);
           break;
         case ">":
-          folded = const GreaterOperation().fold(left, right);
+          folded = constantSystem.greater.fold(left, right);
           break;
         case ">=":
-          folded = const GreaterEqualOperation().fold(left, right);
+          folded = constantSystem.greaterEqual.fold(left, right);
           break;
         case "==":
           if (left.isPrimitive() && right.isPrimitive()) {
-            folded = const EqualsOperation().fold(left, right);
+            folded = constantSystem.equal.fold(left, right);
           }
           break;
         case "===":
           if (left.isPrimitive() && right.isPrimitive()) {
-            folded = const IdentityOperation().fold(left, right);
+            folded = constantSystem.identity.fold(left, right);
           }
           break;
         case "!=":
           if (left.isPrimitive() && right.isPrimitive()) {
-            BoolConstant areEquals = const EqualsOperation().fold(left, right);
+            BoolConstant areEquals = constantSystem.equal.fold(left, right);
             if (areEquals === null) {
               folded = null;
             } else {
               folded = areEquals.negate();
             }
           }
           break;
         case "!==":
           if (left.isPrimitive() && right.isPrimitive()) {
             BoolConstant areIdentical =
-                const IdentityOperation().fold(left, right);
+                constantSystem.identity.fold(left, right);
             if (areIdentical === null) {
               folded = null;
             } else {
               folded = areIdentical.negate();
             }
           }
           break;
       }
       if (folded === null) return signalNotCompileTimeConstant(send);
       return folded;
@@ skipping 34 matching lines @@
     if (classElement.isInterface()) {
       compiler.resolver.resolveMethodElement(constructor);
       constructor = constructor.defaultImplementation;
       classElement = constructor.getEnclosingClass();
     }
 
     Selector selector = elements.getSelector(send);
     List<Constant> arguments =
         evaluateArgumentsToConstructor(selector, send.arguments, constructor);
     ConstructorEvaluator evaluator =
-        new ConstructorEvaluator(constructor, compiler);
+        new ConstructorEvaluator(constructor, constantSystem, compiler);
     evaluator.evaluateConstructorFieldValues(arguments);
     List<Constant> jsNewArguments = evaluator.buildJsNewArguments(classElement);
 
     compiler.registerInstantiatedClass(classElement);
     // TODO(floitsch): take generic types into account.
     DartType type = classElement.computeType(compiler);
     Constant constant = new ConstructedConstant(type, jsNewArguments);
     compiler.constantHandler.registerCompileTimeConstant(constant);
     return constant;
   }
@@ skipping 16 matching lines @@
     // Else we don't need to do anything. The final handler is only
     // optimistically trying to compile constants. So it is normal that we
     // sometimes see non-compile time constants.
     // Simply return [:null:] which is used to propagate a failing
     // compile-time compilation.
     return null;
   }
 }
 
 class TryCompileTimeConstantEvaluator extends CompileTimeConstantEvaluator {
-  TryCompileTimeConstantEvaluator(TreeElements elements, Compiler compiler):
-      super(elements, compiler, isConst: true);
+  TryCompileTimeConstantEvaluator(ConstantSystem constantSystem,
+                                  TreeElements elements,
+                                  Compiler compiler)
+      : super(constantSystem, elements, compiler, isConst: true);
 
   error(Node node) {
     // Just fail without reporting it anywhere.
     throw new CompileTimeConstantError(
         MessageKind.NOT_A_COMPILE_TIME_CONSTANT, const []);
   }
 }
 
 class ConstructorEvaluator extends CompileTimeConstantEvaluator {
   FunctionElement constructor;
   final Map<Element, Constant> definitions;
   final Map<Element, Constant> fieldValues;
 
-  ConstructorEvaluator(FunctionElement constructor, Compiler compiler)
+  ConstructorEvaluator(FunctionElement constructor,
+                       ConstantSystem constantSystem,
+                       Compiler compiler)
       : this.constructor = constructor,
         this.definitions = new Map<Element, Constant>(),
         this.fieldValues = new Map<Element, Constant>(),
-        super(compiler.resolver.resolveMethodElement(constructor),
+        super(constantSystem,
+              compiler.resolver.resolveMethodElement(constructor),
               compiler,
               isConst: true);
 
   Constant visitSend(Send send) {
     Element element = elements[send];
     if (Elements.isLocal(element)) {
       Constant constant = definitions[element];
       if (constant === null) {
         compiler.internalError("Local variable without value", node: send);
       }
@@ skipping 20 matching lines @@
       }
     });
   }
 
   void evaluateSuperOrRedirectSend(Selector selector,
                                    Link<Node> arguments,
                                    FunctionElement targetConstructor) {
     List<Constant> compiledArguments =
         evaluateArgumentsToConstructor(selector, arguments, targetConstructor);
 
-    ConstructorEvaluator evaluator =
-        new ConstructorEvaluator(targetConstructor, compiler);
+    ConstructorEvaluator evaluator = new ConstructorEvaluator(
+        targetConstructor, constantSystem, compiler);
     evaluator.evaluateConstructorFieldValues(compiledArguments);
     // Copy over the fieldValues from the super/redirect-constructor.
     evaluator.fieldValues.forEach((key, value) => fieldValues[key] = value);
   }
 
   /**
    * Runs through the initializers of the given [constructor] and updates
    * the [fieldValues] map.
    */
   void evaluateConstructorInitializers() {
@@ skipping 72 matching lines @@
       Constant fieldValue = fieldValues[field];
       if (fieldValue === null) {
         // Use the default value.
         fieldValue = compiler.compileConstant(field);
       }
       jsNewArguments.add(fieldValue);
     });
     return jsNewArguments;
   }
 }