[webkit-dev] RFC: dropping support for x87

[Xan]

Hi,
as part of Igalia's work on 32bit support we spent some time trying to iron
out some bugs in JSC/intel 32bit builds. A bunch of them were related to
rounding errors (or more precisely, differences) caused by the extended
precision FP registers used by default in x87; which, in turn, is the
default in GCC when compiling with -m32.

We discussed a number of solutions, but then we noticed that major browsers
have in recent times already dropped support for x87:

Firefox:
https://support.mozilla.org/en-US/kb/your-hardware-no-longer-supported
Chrome: https://support.google.com/chrome/a/answer/7100626?hl=en

This removes a small maintenance burden and prevents future bugs like the
ones we investigated. Also, in practice, intel hardware older than Pentium
4-era machines is very rare. All this considered, we decided it made sense
to do the same in WebKit.

In short, this email is a RFC to see if anyone in the WebKit community
objects to this change, or has any comment about it. The bug where we have
attached the patch for this change is:
https://bugs.webkit.org/show_bug.cgi?id=194853

Regards,
Xan
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