[Bug tree-optimization/62156] memcmp doesn't see through memcpy at compile-time

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62156

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
Not much difference using __gnu_cxx::__vstring (no reference counting, small
string optimization):

__builtin_memcpy (&MEM[(struct __sso_string_base
*)&D.28720].D.23707._M_local_data, "foo", 3);
MEM[(size_type *)&D.28720 + 8B] = 3;
MEM[(char_type &)&D.28720 + 19] = 0;
__r_46 = __builtin_memcmp (&MEM[(struct __sso_string_base
*)&D.28720].D.23707._M_local_data, "bar", 3);