[turbofan] Introduce a dedicated CheckBounds operator.

test/mjsunit/compiler/regress-5100.js

Index: test/mjsunit/compiler/regress-5100.js
diff --git a/test/mjsunit/compiler/regress-5100.js b/test/mjsunit/compiler/regress-5100.js
new file mode 100644
index 0000000000000000000000000000000000000000..694cd8a75be881ac527972b935db32afe9565c02
--- /dev/null
+++ b/test/mjsunit/compiler/regress-5100.js
@@ -0,0 +1,51 @@
+// Copyright 2016 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
+
+var a = [0, 1];
+a["true"] = "true";
+a["false"] = "false";
+a["null"] = "null";
+a["undefined"] = "undefined";
+
+// Ensure we don't accidentially truncate true when used to index arrays.
+(function() {
+  function f(x) { return a[x]; }
+
+  assertEquals(0, f(0));
+  assertEquals(0, f(0));
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals("true", f(true));
+})();
+
+// Ensure we don't accidentially truncate false when used to index arrays.
+(function() {
+  function f( x) { return a[x]; }
+
+  assertEquals(0, f(0));
+  assertEquals(0, f(0));
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals("false", f(false));
+})();
+
+// Ensure we don't accidentially truncate null when used to index arrays.
+(function() {
+  function f( x) { return a[x]; }
+
+  assertEquals(0, f(0));
+  assertEquals(0, f(0));
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals("null", f(null));
+})();
+
+// Ensure we don't accidentially truncate undefined when used to index arrays.
+(function() {
+  function f( x) { return a[x]; }
+
+  assertEquals(0, f(0));
+  assertEquals(0, f(0));
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals("undefined", f(undefined));
+})();