[Bug tree-optimization/84794] memcpy/memmove between a struct and its first member not eliminated

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84794

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-03-12
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
 _2 = &p_4(D)->D.1965.b;

this should be canonicalized to

 _2 = p_4(D);

we don't do such canonicalization because it defeats __builtin_object_size

Eventually the laddress pass could apply such canonicalization more
aggressively
(still needs folding to trigger on the mem{cpy,move}).