[ia32] Match -0 - x with sign bit flip.

[ia32] Match -0 - x with sign bit flip.

We can use xorps/xorpd on Intel CPUs to flip the sign bit. Ideally we'd
use an absolute 128-bit constant in the code object, as OCaml/GCC
does, however that requires 128-bit alignment for code objects,
which is not yet implemented. So for now we materialize the mask
inline.

As drive-by-fix, don't hardcode xmm0 as scratch double register.

R=svenpanne@chromium.org

Committed: https://crrev.com/49bb6617aba36b1b346e2fbfefa2771de7234e68
Cr-Commit-Position: refs/heads/master@{#27618}

[Benedikt Meurer, 2015-04-07 09:37:09]

Hey Sven,

This is a port of the x64 change landed earlier today (see
https://codereview.chromium.org/1046893002). Please take a look.

Thanks,
Benedikt

[Sven Panne, 2015-04-07 10:41:52]

The CQ bit was checked by svenpanne@chromium.org

[Sven Panne, 2015-04-07 10:41:53]

lgtm

[commit-bot: I haz the power, 2015-04-07 10:42:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1064833002/1

[commit-bot: I haz the power, 2015-04-07 10:44:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-07 10:44:14]

Patchset 1 (id:??) landed as
https://crrev.com/49bb6617aba36b1b346e2fbfefa2771de7234e68
Cr-Commit-Position: refs/heads/master@{#27618}