cps-ir: Implement boolean conversion in and use it to implement '&&', '||', and '?:'.

pkg/compiler/lib/src/js_backend/codegen/unsugar.dart

+library dart2js.unsugar_cps;
+
+import '../../cps_ir/cps_ir_nodes.dart';
+
+// TODO(karlklose): share the [ParentVisitor].
+import 'package:compiler/src/cps_ir/optimizers.dart';
+
+class Boolify extends IsTrue {
+  Boolify(Primitive expression) : super(expression);
+  accept(Visitor visitor) => visitor.visitBoolify(this);
+}
+
+/// Rewrites the initial CPS IR to make Dart semantics explicit.
+///
+/// Performs the following rewrites:
+/// - Branch(IsTrue(v), c1, c2) -> Branch(Boolify(v), c1, c2)
+class UnsugarVisitor extends RecursiveVisitor {
+  const UnsugarVisitor();
+
+  void rewrite(FunctionDefinition function) {
+    // Set all parent pointers.
+    new ParentVisitor().visit(function);
+    visit(function);
+  }
+
+  @override
+  Node visit(Node node) {
+    Node result = node.accept(this);
+    return result != null ? result : node;
+  }
+
+  visitBranch(Branch node) {
+    // Create new node.
+    IsTrue condition = node.condition;
+    Branch newNode = new Branch(
+        new Boolify(condition.value.definition),
+        node.trueContinuation.definition,
+        node.falseContinuation.definition);
+    // Replace the node in the parent context.
+    InteriorNode parent = node.parent;
+    parent.body = newNode;
+    newNode.parent = parent;
+    // Remove stale referenced.

[sigurdm, 2014/11/20 12:47:28]

reference*s*

+    condition.value.unlink();
+    node.trueContinuation.unlink();
+    node.falseContinuation.unlink();
+  }
+}