VM: Improve and fix double negation on MIPS.

tests/language/nan_identical_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file

[zra, 2015/10/29 21:16:13]

It looks like this test will fail if we ever try to run on an architecture
configured to canonicalize NaNs. Whatever we pull out of the byte array into an
FP register will be the canonicalized value. V8 has chosen to turn that bit on
on ARM64 as an optimization, if I understand this CL correctly:
https://codereview.chromium.org/255343004/

I guess this test failing well let us know. Not sure if that's the right way to
find out. Maybe add a comment here about the problem?

 // 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.
 // Test a new statement by itself.
-// VMOptions=--optimization-counter-threshold=4 --no-use-osr
+// VMOptions=--optimization-counter-threshold=4
 
 import 'dart:typed_data';
 
 import "package:expect/expect.dart";
 
 double uint64toDouble(int i) {
   var buffer = new Uint8List(8).buffer;
   var bdata = new ByteData.view(buffer);
   bdata.setUint64(0, i);
   return bdata.getFloat64(0);
@@ skipping 25 matching lines @@
     Expect.isFalse(checkIdentical(a, b));
     Expect.isFalse(checkIdentical(-a, -b));
     Expect.isFalse(checkIdentical(-a, b));
     Expect.isFalse(checkIdentical(a, -b));
 
     Expect.isTrue(checkIdentical(-(-a), a));
     Expect.isTrue(checkIdentical(-(-b), b));
   }
 }
 
-checkIdentical(a, b) => identical(a, b);
+checkIdentical(a, b) => identical(a, b);