Since DIV and IDIV can generate exceptions, we need an additional output
parameter indicating whether an execption has occured.  To avoid increasing
register pressure on i386, we use %rsi, which is already allocated for
the fastop code pointer.

Gleb: added comment about fop usage as exception indication.
Signed-off-by: Avi Kivity <avi.kivity@gmail.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>