[Bug rtl-optimization/79279] combine/simplify_set: wrong call to REG_CANNOT_CHANGE_MODE_P

[aurelien.buhrig.gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79279

Aurelien Buhrig <aurelien.buhrig.gcc at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #2 from Aurelien Buhrig <aurelien.buhrig.gcc at gmail dot com> ---
According to the above gcc-patches discussion, 
checking m2 -> m1 is required to be sure that the new reg:m2 interpreted as m1
is valid. 

So both checks would be needed. But although the m1 -> m2 transformation is
invalid, this change should be filtered by predicates (from general_operand)
which wasn't.

So no need to fix, unless maybe speeding up the combine process.