Unify handling of identical(NaN, NaN) between generated code and Dart API.

Unify handling of identical(NaN, NaN) between generated code and Dart API.
Addresses issue 18738, assuming that the spec spec will be/has been updated so
doubles are identical iff they have the same representation as 64-bit IEEE
floating point numbers.

R=koda@google.com, srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=37118

[srdjan, 2014-06-06 23:23:55]

lgtm

[koda, 2014-06-06 23:26:29]

https://codereview.chromium.org/317643004/diff/1/runtime/vm/object_test.cc
File runtime/vm/object_test.cc (right):

https://codereview.chromium.org/317643004/diff/1/runtime/vm/object_test.cc#ne...
runtime/vm/object_test.cc:531: const Double& nan2 =
Double::Handle(Double::New(1.0/0.0));
Doesn't 1.0/0.0 give you positive infinity?

It seems better to to a reinterpret_cast here from two explicit bit patterns.

[regis, 2014-06-06 23:51:56]

Thanks!
PTAL

https://codereview.chromium.org/317643004/diff/1/runtime/vm/object_test.cc
File runtime/vm/object_test.cc (right):

https://codereview.chromium.org/317643004/diff/1/runtime/vm/object_test.cc#ne...
runtime/vm/object_test.cc:531: const Double& nan2 =
Double::Handle(Double::New(1.0/0.0));
On 2014/06/06 23:26:29, koda wrote:
> Doesn't 1.0/0.0 give you positive infinity?
> 
> It seems better to to a reinterpret_cast here from two explicit bit patterns.

Yes, thank you, 1.0/0.0 is infinity, but not a NaN.
I've added isnan checks and explicit bit patterns.

[koda, 2014-06-06 23:54:28]

LGTM

https://codereview.chromium.org/317643004/diff/20001/runtime/vm/object_test.cc
File runtime/vm/object_test.cc (right):

https://codereview.chromium.org/317643004/diff/20001/runtime/vm/object_test.c...
runtime/vm/object_test.cc:532: const Double& nan2 =
Double::Handle(Double::New(1.0/0.0));
Please rename the variable to something more appropriate, like 'inf'.

[regis, 2014-06-09 16:37:21]

Thanks!

https://codereview.chromium.org/317643004/diff/20001/runtime/vm/object_test.cc
File runtime/vm/object_test.cc (right):

https://codereview.chromium.org/317643004/diff/20001/runtime/vm/object_test.c...
runtime/vm/object_test.cc:532: const Double& nan2 =
Double::Handle(Double::New(1.0/0.0));
On 2014/06/06 23:54:28, koda wrote:
> Please rename the variable to something more appropriate, like 'inf'.

Done.

[regis, 2014-06-09 16:41:04]

Committed patchset #3 manually as r37118 (presubmit successful).