As per the arm Procedure Call Standard for the Arm Architecture
section 6.1.2 [1], VFP registers s16-s31 (d8-d15, q4-q7) must be
preserved across subroutine calls.
The current setjmp/longjmp implementations preserve only the core
registers, with the jump buffer size too small to store the required
co-processor registers.
In accordance with the C Library ABI for the Arm Architecture
section 6.11 [2], this patch sets _JBTYPE to long long adjusting
_JBLEN to 20.
It also emits vfp load/store instructions depending on architectural
support, predicated at compile time on ACLE feature-test macros.
[1] https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst
[2] https://github.com/ARM-software/abi-aa/blob/main/clibabi32/clibabi32.rst
15ad816ddd