LRA: identify biggest access mode for hard_regs and use it in split_reg
PR target/70083
* lra-lives.c (process_bb_lives): Also update biggest mode for hard
regs.
(lra_create_live_ranges_1): initialize hard register biggest_mode to
VOIDmode.
* lra-constraints.c (split_reg): For hard regs, try to find the
biggest single-register mode used in the function.
testsuite/
PR target/70083
* gcc.dg/torture/pr70083.c: New test.
* gcc.target/i386/pr70083.c: New test.