This introduces 128-bit addition helpers and adds the following instructions. * Multiply-Add Low Doubleword (maddld) * Multiply-Add High Doubleword (maddhd) * Multiply-Add High Doubleword Unsigned (maddhdu) Change-Id: I04e6ea5fb4978b341a6e648424de2930ad41f449 Signed-off-by: Sandipan Das <sandipan@linux.ibm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40905 Reviewed-by: Boris Shingarov <shingarov@labware.com> Maintainer: Jason Lowe-Power <power.jg@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>