Fix a bug in the variable allocator: a pure instruction between an inlined if and its inlined expre…

tests/language/inlined_conditional_test.dart

Index: tests/language/inlined_conditional_test.dart
===================================================================
--- tests/language/inlined_conditional_test.dart	(revision 0)
+++ tests/language/inlined_conditional_test.dart	(revision 0)
@@ -0,0 +1,49 @@
+// Copyright (c) 2013, 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.
+
+// Regression test for dart2js. There was a bug in the variable
+// allocator when a pure (side-effect free) instruction stand
+// in-between an inlined `if` and its inlined expression.
+
+import "package:expect/expect.dart";
+
+var topLevel;
+
+// Make [foo] an inlineable expression with a return type check.
+Function foo(c) {
+  // Use [c] twice to make sure it is stored in a local.
+  return (c is Function ? null : c);
+}
+
+bar() {
+  var b = new Object();
+  f() {
+    // Inside a closure, locals that escape are stored in a closure
+    // class. By using [b] in both branches, the optimizers will move
+    // the fetching of [b] before the `if`. This puts the fetching
+    // instruction in between the `if` and the expression of the `if`.
+    // This instruction being pure, the variable allocator was dealing
+    // with it in a special way.
+    //
+    // Because the expression in the `if` is being recognized by the
+    // optimizers as being also a JavaScript expression, we do not
+    // allocate a name for it. But some expressions that it uses still
+    // can have a name, and our variable allocator did not handle live
+    // variables due to the inlining of the ternary expression in [foo].
+    if (foo(topLevel) == null) {
+      return b.toString();
+    } else {
+      return b.hashCode;
+    }
+  }
+  return f();
+}
+
+main() {
+  // Make sure the inferrer does not get an exact type for [topLevel].
+  topLevel = new Object();
+  topLevel = main;
+  var res = bar();
+  Expect.isTrue(res is String);
+}