http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49234
--- Comment #16 from Aldy Hernandez <aldyh at gcc dot gnu.org> 2013-03-05 18:00:12 UTC --- Created attachment 29590 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29590 WIP: proposed patch special casing constant phi arguments Ian. Sure, I can handle SSA_NAME_VAR equality, but then we won't be able to handle self referential operations like the one in gcc.dg/Wstrict-overflow-12.c. For example, with your suggested approach (in this attached patch), we fail here: for (i = 1, bits = 1; i > 0; i += i) /* { dg-warning "assuming signed overflow does not occur" "correct warning" } */ ++bits; Because we encounter something like this which is perfectly valid with your approach: i_1 = PHI <1(2), i_4(3)>
