Fix optimized Math.pow on x64 with NaN exponents.

Fix optimized Math.pow on x64 with NaN exponents.

The libc implementation used by the optimized code differs
from the expected behaviour. It does not return double.NaN
as the Dart implementation of pow when the exponent is NaN.

The test fails when running with  a low optimization-counter-threshold=5.

BUG=https://code.google.com/p/dart/issues/detail?id=13543
TEST=math/double_pow_test
R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27950

[srdjan, 2013-09-26 13:09:22]

LGTM

https://codereview.chromium.org/24695003/diff/1/runtime/vm/intermediate_langu...
File runtime/vm/intermediate_language_x64.cc (right):

https://codereview.chromium.org/24695003/diff/1/runtime/vm/intermediate_langu...
runtime/vm/intermediate_language_x64.cc:4259: __ movsd(result, exp);
Add comment: result is NaN

[Florian Schneider, 2013-09-26 13:11:28]

Thanks for the quick review.

https://codereview.chromium.org/24695003/diff/1/runtime/vm/intermediate_langu...
File runtime/vm/intermediate_language_x64.cc (right):

https://codereview.chromium.org/24695003/diff/1/runtime/vm/intermediate_langu...
runtime/vm/intermediate_language_x64.cc:4259: __ movsd(result, exp);
On 2013/09/26 13:09:22, srdjan wrote:
> Add comment: result is NaN

Done.

[Florian Schneider, 2013-09-26 13:13:04]

Committed patchset #2 manually as r27950 (presubmit successful).