They save and restore what setjmp and longjmp do without the signal mask. _longjmp keeps the current MXCSR exception flags and takes the other MXCSR bits from the buffer, as the bundled libc.prx's _longjmp (J03093718, 0x1153e0) and FreeBSD's ___longjmp do, and on Windows it moves the TEB stack bounds as longjmp does. _setjmp writes 0 where setjmp marks a saved mask, so longjmp restores none from its buffer.
