http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56982
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-16 16:04:10 UTC --- At RTL time (besides it being a pessimization), the thing is that _3 is assigned a pseudo (compared to before the change, where it had only a single use and thus has been TERed), that pseudo is initialized from *e, and initialized to 1 in the bb where the PHI had 1, and the pseudo is spilled to the stack. So it will initially contain the 0 value (correct), then that is overwritten with 1 (fine for the first setjmp returning case), but when setjmp returns second time, the value is still 1 rather than 0. So the questions are: - is it desirable that uncprop does anything to SSA_NAME_VAR == NULL phis? - shouldn't something like that be not performed if current function calls setjmp (or more narrowly, if there is a returns twice function somewhere in between the considered setter and user)? - what other optimizations might be similarly problematic across returns twice calls?
