This change makes the code less sensitive to the exact type of the mode,
i.e. it forces a conversion where necessary. This becomes important
when wrappers like scalar_int_mode and scalar_mode can also be used
instead of machine_mode.
Using rtx_mode_t also abstracts away the representation. The fact that
it's a std::pair rather than a custom class isn't important to users of
the interface.
gcc/
2016-11-18 Richard Sandiford <richard.sandiford@arm.com>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>