These are widened to a wider UADDE/USUBE, with the overflow value
unused, and with the same synthesis of a new overflow value as for the
O operations.
Reviewed By: paquette
Differential Revision: https://reviews.llvm.org/D95326
This makes G_SADDE and G_SSUBE legal in preparation for further work
legalizing overflowing operations. It's fine that they don't have an
instruction selector implementation yet, because G_UADDE and G_USUBE are
already legal on AArch64 without an instruction selector implementation. This
completes the set of G_[SU]{ADD,SUB}[EO] operations on AArch64.
Reviewed By: paquette
Differential Revision: https://reviews.llvm.org/D95325