tree a4b3b7cfe0e0d8fe23008b5c44a5d4ff43081738
parent 6b5a1f74e50170e64104135490dc32b657483594
author Chris Zankel <chris@zankel.net> 1390975791 -0800
committer Chris Zankel <chris@zankel.net> 1391032046 -0800

xtensa: fix fast_syscall_spill_registers

The original implementation could clobber registers under certain conditions.

The Xtensa processor architecture uses windowed registers and the original
implementation was using a4 as a temporary register, which under certain
conditions could be register a0 of the oldest window frame, and didn't always
restore the content correctly.

By moving the _spill_registers routine inside the fast system call, it frees
up one more register (the return address is not required anymore) for the
spill routine.

Signed-off-by: Chris Zankel <chris@zankel.net>