Ensure we don't overflow in BCE

test/mjsunit/regress/regress-bce-underflow.js

Index: test/mjsunit/regress/regress-bce-underflow.js
diff --git a/test/mjsunit/regress/regress-bce-underflow.js b/test/mjsunit/regress/regress-bce-underflow.js
new file mode 100644
index 0000000000000000000000000000000000000000..daa776005e7b5bcb165cd04f2c6abf226fc720b3
--- /dev/null
+++ b/test/mjsunit/regress/regress-bce-underflow.js
@@ -0,0 +1,35 @@
+// 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 f(a, i, bool) {
+  var result;
+  if (bool) {
+    // Make sure i - -0x80000000 doesn't overflow in BCE, missing a check for
+    // x-0 later on.
+    result = f2(a, 0x7fffffff, i, i, -0x80000000);
+  } else {
+    result = f2(a, -3, 4, i, 0);
+  }
+  return result;
+}
+
+function f2(a, c, x, i, d) {
+  return a[x + c] + a[x - 0] + a[i - d];
+}
+
+
+var a = [];
+var i = 0;
+a.push(i++);
+a.push(i++);
+a.push(i++);
+a.push(i++);
+a.push(i++);
+f(a, 0, false);
+f(a, 0, false);
+f(a, 0, false);
+%OptimizeFunctionOnNextCall(f);
+%DebugPrint(f(a, -0x7fffffff, true));