This reverts most of c7360f4b02.
Unlike the other floating-point registers, these values are callee-saved
(see "System V Application Binary Interface, AMD64 Architecture
Supplement" section 3.2.1.) So we need to preserve their values and not
reset defaults on context switch.
EMMS, as the previous changes used, does not suffice to clear
exceptions. We could use FNCLEX instead, but we need to reset
x87 state on context switch anyway, so use FNINIT. Do not
reinstate FNCLEX in the exception handler since it will
be executed on context switch anyway.
We also need to ensure a clean initial state, so take care of that
in arch_thread_init.
See also:
* remarks in 396b74228e
* as well as 53e2dc0f85Fixes#19454 and #18624. Doesn't regress #18656 and #19063.
Doesn't seem to affect #19450.
Change-Id: I7179f1ec7304e7aed09ff80f6773e53d5dbdf5f9
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9081
Reviewed-by: Jérôme Duval <[email protected]>
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>
Augustin Cavalier
4c76039f6f