[intrinsics] Kill the %_IsMinusZero intrinsic.

[intrinsics] Kill the %_IsMinusZero intrinsic.

By now only the default %TypedArray%.prototype.sort compare function
and the JS implementation of SameValueZero were still using the odd
%_IsMinusZero intrinsic, whose semantics both included a number check
(actually HeapNumber test) plus testing if the heap number stores the
special -0 value. In both cases we already know that we deal with
number so we can reduce it to a simple number test for -0, which can
be expressed via dividing 1 by that value and checking the sign of
the result. In case of the compare function, we can be even smarter
and work with the reciprocal values in case x and y are equal to 0
(although long term we should probably rewrite the fast case for
the typed array sorting function in C++ anyway, which will be way,
way faster than our handwritten callback-style, type-feedback
polluted JS implementation).

R=yangguo@chromium.org

Committed: https://crrev.com/00f7d1f5f82139a041e6cf57294f67670169074e
Cr-Commit-Position: refs/heads/master@{#33833}

[Benedikt Meurer, 2016-02-08 18:54:37]

Hey Yang,

Removing a lot of special case code that has no real value (anymore at least).
Please take a look.

Thanks,
Benedikt

[Yang, 2016-02-09 06:09:48]

lgtm

[Benedikt Meurer, 2016-02-09 06:10:26]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-02-09 06:10:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1680783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1680783002/1

[commit-bot: I haz the power, 2016-02-09 06:28:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-09 06:29:08]

Description was changed from

==========
[intrinsics] Kill the %_IsMinusZero intrinsic.

By now only the default %TypedArray%.prototype.sort compare function
and the JS implementation of SameValueZero were still using the odd
%_IsMinusZero intrinsic, whose semantics both included a number check
(actually HeapNumber test) plus testing if the heap number stores the
special -0 value. In both cases we already know that we deal with
number so we can reduce it to a simple number test for -0, which can
be expressed via dividing 1 by that value and checking the sign of
the result. In case of the compare function, we can be even smarter
and work with the reciprocal values in case x and y are equal to 0
(although long term we should probably rewrite the fast case for
the typed array sorting function in C++ anyway, which will be way,
way faster than our handwritten callback-style, type-feedback
polluted JS implementation).

R=yangguo@chromium.org
==========

to

==========
[intrinsics] Kill the %_IsMinusZero intrinsic.

By now only the default %TypedArray%.prototype.sort compare function
and the JS implementation of SameValueZero were still using the odd
%_IsMinusZero intrinsic, whose semantics both included a number check
(actually HeapNumber test) plus testing if the heap number stores the
special -0 value. In both cases we already know that we deal with
number so we can reduce it to a simple number test for -0, which can
be expressed via dividing 1 by that value and checking the sign of
the result. In case of the compare function, we can be even smarter
and work with the reciprocal values in case x and y are equal to 0
(although long term we should probably rewrite the fast case for
the typed array sorting function in C++ anyway, which will be way,
way faster than our handwritten callback-style, type-feedback
polluted JS implementation).

R=yangguo@chromium.org

Committed: https://crrev.com/00f7d1f5f82139a041e6cf57294f67670169074e
Cr-Commit-Position: refs/heads/master@{#33833}
==========

[commit-bot: I haz the power, 2016-02-09 06:29:09]

Patchset 1 (id:??) landed as
https://crrev.com/00f7d1f5f82139a041e6cf57294f67670169074e
Cr-Commit-Position: refs/heads/master@{#33833}