https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114591
--- Comment #9 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
>
> It looks that different modes of memory read confuse LRA to not CSE the read.
>
> IMO, if the preloaded value is later accessed in different modes, LRA should
> leave it. Alternatively, LRA should CSE memory accesses in different modes.
(insn 7 6 12 2 (set (reg:HI 101 [ _5 ])
(subreg:HI (reg:SI 98 [ v1.0_1 ]) 0)) "test.c":6:12 86
{*movhi_internal}
(expr_list:REG_DEAD (reg:SI 98 [ v1.0_1 ])
(nil)))
May be we should reduce cost from simple move instruction(with subreg?) when
calculating total_cost, since it's probably be eliminated by later rtl
optimization.
