[turbofan] Optimize loads of global constants in JSTypedLowering.

test/mjsunit/global-undefined.js

Index: test/mjsunit/global-undefined.js
diff --git a/test/mjsunit/global-undefined.js b/test/mjsunit/global-undefined.js
new file mode 100644
index 0000000000000000000000000000000000000000..6190f6f55207fcb5821cf4274a061a298353a54b
--- /dev/null
+++ b/test/mjsunit/global-undefined.js
@@ -0,0 +1,149 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function test(expected, f) {
+  assertEquals(expected, f());
+  assertEquals(expected, f());
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals(expected, f());
+  assertEquals(expected, f());
+}
+
+function testThrows(f) {
+  assertThrows(f);
+  assertThrows(f);
+  %OptimizeFunctionOnNextCall(f);
+  assertThrows(f);
+  assertThrows(f);
+}
+
+function f1() { return undefined; }
+test(void 0, f1);
+
+function f2() { return void 0; }
+test(void 0, f2);
+
+function f3() { return void 0 == void 0; }
+test(true, f3);
+
+function f4() { return void 0 == undefined; }
+test(true, f4);
+
+function f5() { return undefined == void 0; }
+test(true, f5);
+
+function f6() { return "" + undefined; }
+test("undefined", f6);
+
+function f7() { return void 0 === void 0; }
+test(true, f7);
+
+function f8() { return void 0 === undefined; }
+test(true, f8);
+
+function f9() { return undefined === void 0; }
+test(true, f9);
+
+delete undefined;
+
+function g1() { return undefined; }
+test(void 0, g1);
+
+function g2() { return void 0; }
+test(void 0, g2);
+
+function g3() { return void 0 == void 0; }
+test(true, g3);
+
+function g4() { return void 0 == undefined; }
+test(true, g4);
+
+function g5() { return undefined == void 0; }
+test(true, g5);
+
+function g6() { return "" + undefined; }
+test("undefined", g6);
+
+function g7() { return void 0 === void 0; }
+test(true, g7);
+
+function g8() { return void 0 === undefined; }
+test(true, g8);
+
+function g9() { return undefined === void 0; }
+test(true, g9);
+
+undefined = 111;
+
+function h1() { return undefined; }
+test(void 0, h1);
+
+function h2() { return void 0; }
+test(void 0, h2);
+
+function h3() { return void 0 == void 0; }
+test(true, h3);
+
+function h4() { return void 0 == undefined; }
+test(true, h4);
+
+function h5() { return undefined == void 0; }
+test(true, h5);
+
+function h6() { return "" + undefined; }
+test("undefined", h6);
+
+function h7() { return void 0 === void 0; }
+test(true, h7);
+
+function h8() { return void 0 === undefined; }
+test(true, h8);
+
+function h9() { return undefined === void 0; }
+test(true, h9);
+
+// -------------
+
+function k1() { return this.undefined; }
+test(void 0, k1);
+
+function k2() { return void 0; }
+test(void 0, k2);
+
+function k3() { return void 0 == void 0; }
+test(true, k3);
+
+function k4() { return void 0 == this.undefined; }
+test(true, k4);
+
+function k5() { return this.undefined == void 0; }
+test(true, k5);
+
+function k6() { return "" + this.undefined; }
+test("undefined", k6);
+
+function k7() { return void 0 === void 0; }
+test(true, k7);
+
+function k8() { return void 0 === this.undefined; }
+test(true, k8);
+
+function k9() { return this.undefined === void 0; }
+test(true, k9);
+
+// -------------
+
+function m1() { return undefined.x; }
+testThrows(m1);
+
+function m2() { return undefined.undefined; }
+testThrows(m2);
+
+function m3() { return (void 0).x; }
+testThrows(m3);
+
+function m4() { return (void 0).undefined; }
+testThrows(m4);