[Bug rtl-optimization/85925] [7/8/9 regression] Mis-compilation at -02, masking with 257 goes wrong in combine

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85925

--- Comment #17 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
On further thoughts, it might be possible to rescue the mechanism because the
problem here is that a ZERO_EXTRACT is happily rewritten from SI to HImode,
thus breaking the WORD_REGISTER_OPERATIONS semantics.  So a patch selectively
disabling the mechanism for problematic operations might be better and less
pessimizing.