target-openrisc: Write back result before FPE exception

The architecture manual is unclear about this, but the or1ksim
does writeback before the exception.  This requires splitting
the helpers in half, with the exception raised by the second.

Acked-by: Stafford Horne <shorne@gmail.com>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>
3 files changed