Refactoring of string literals. Implement static string addition.

frog/leg/ssa/nodes.dart

 // Copyright (c) 2011, 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.
 
 interface HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 1083 matching lines @@
         return HType.ARRAY;
       }
     }
     return HType.UNKNOWN;
   }
 
   bool hasExpectedType() => builtinJsName != null;
 
   HInstruction fold() {
     if (name == const SourceString('length') && inputs[1].isLiteralString()) {
-      // TODO(lrn): Account for escapes in string.
+      HLiteral input = inputs[1];
+      DartString string = input.value;
+      return new HLiteral(string.length, HType.INTEGER);
     }
     return this;
   }
 
   void prepareGvn() {
     if (builtinJsName == 'length') {
       assert(!hasSideEffects());
     } else {
       setAllSideEffects();
     }
@@ skipping 120 matching lines @@
   HType computeDesiredInputType(HInstruction input) {
     // TODO(floitsch): we want the target to be a function.
     if (input == target) return HType.UNKNOWN;
     if (isString() || left.isString()) {
       return (input == left) ? HType.STRING : HType.UNKNOWN;
     }
     if (right.isString()) return HType.STRING;
     if (isNumber() || left.isNumber() || right.isNumber()) return HType.NUMBER;
     return HType.UNKNOWN;
   }
+
+  HInstruction fold() {
+    if (left.isLiteralString() && right is HLiteral) {
+      HLiteral op1 = left;
+      HLiteral op2 = right;
+      DartString leftString = op1.value;
+      DartString otherString = null;
+      if (right.isLiteralString()) {
+        otherString = op2.value;
+      } else {
+        assert(op2.isLiteralNumber() ||
+               op2.isLiteralBoolean() ||
+               op2.isLiteralNull());
+        String string = op2.value.toString();
+        otherString = new DartString.literal(string);
+      }
+      DartString cons = new ConsDartString(leftString, otherString);
+      return new HLiteral(cons, HType.STRING);
+    }
+    return super.fold();
+  }
 }
 
 class HDivide extends HBinaryArithmetic {
   HDivide(HStatic target, HInstruction left, HInstruction right)
       : super(target, left, right);
   accept(HVisitor visitor) => visitor.visitDivide(this);
   num evaluate(num a, num b) => a / b;
   bool typeEquals(other) => other is HDivide;
   bool dataEquals(HInstruction other) => true;
 }
@@ skipping 36 matching lines @@
       return this;
     }
     return super.fold();
   }
 
   num evaluate(num a, num b) => a ~/ b;
   bool typeEquals(other) => other is HTruncatingDivide;
   bool dataEquals(HInstruction other) => true;
 }
 
+
+class ConsDartStringIterator implements Iterator<int> {
+  Iterator<int> current;
+  DartString right;
+  bool hasNextLookAhead;
+  ConsDartStringIterator(ConsDartString cons)
+      : current = cons.left.iterator(),
+        right = cons.right {
+    hasNextLookAhead = current.hasNext();
+    if (!hasNextLookAhead) {
+      nextPart();
+    }
+  }
+  bool hasNext() {
+    return hasNextLookAhead;
+  }
+  int next() {
+    assert(hasNextLookAhead);
+    int result = current.next();
+    hasNextLookAhead = current.hasNext();
+    if (!hasNextLookAhead) {
+      nextPart();
+    }
+    return result;
+  }
+  void nextPart() {
+    if (right !== null) {
+      current = right.iterator();
+      right = null;
+      hasNextLookAhead = current.hasNext();
+    }
+  }
+}
+
+class ConsDartString extends DartString {
+  final DartString left;
+  final DartString right;
+  final int length;
+  int hashCache = null;
+  String toStringCache;
+  ConsDartString(DartString left, DartString right)
+      : this.left = left,
+        this.right = right,
+        length = left.length + right.length;
+
+  Iterator<int> iterator() => new ConsDartStringIterator(this);
+
+  String toString() {
+    if (toStringCache !== null) return toStringCache;
+    toStringCache = left.toString().concat(right.toString());
+    return toStringCache;
+  }
+}
+
+
 // TODO(floitsch): Should HBinaryArithmetic really be the super class of
 // HBinaryBitOp?
 class HBinaryBitOp extends HBinaryArithmetic {
   HBinaryBitOp(HStatic target, HInstruction left, HInstruction right)
       : super(target, left, right);
 
   HType computeType() {
     HType type = computeInputsType();
     builtin = type.isInteger();
     if (!type.isUnknown()) return type;
@@ skipping 266 matching lines @@
   }
 
   // Literals have the type they have. It can't be changed.
   bool updateType() => false;
 
   bool hasExpectedType() => true;
 
   bool isLiteralBoolean() => value is bool;
   bool isLiteralNull() => value === null;
   bool isLiteralNumber() => value is num;
-  bool isLiteralString() => value is QuotedString;
+  bool isLiteralString() => value is DartString;
   bool typeEquals(other) => other is HLiteral;
   bool dataEquals(HLiteral other) => value == other.value;
 }
 
 class HNot extends HInstruction {
   HNot(HInstruction value) : super(<HInstruction>[value]);
   void prepareGvn() {
     assert(!hasSideEffects());
     setUseGvn();
   }
@@ skipping 391 matching lines @@
 
   HInstruction get expression() => inputs[0];
 
   HType computeType() => HType.BOOLEAN;
   bool hasExpectedType() => true;
 
   accept(HVisitor visitor) => visitor.visitIs(this);
 
   toString() => "$expression is $typeExpression";
 }