The new formulation makes better use of add-with-carry type insns
that the host may have. Use gcc's sign adjustment trick to avoid
having to perform a 128-bit negation.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Replace some x86_64 specific inline assembly with something that
all 64-bit hosts ought to optimize well. At worst this becomes
a call to the gcc __multi3 routine, which is no worse than our
implementation in util/host-utils.c.
With gcc 4.7, we get identical code generation for x86_64. We
now get native multiplication on ia64 and s390x hosts. With minor
improvements to gcc we can get it for ppc64 as well.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
