http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54369
Steve Ellcey <sje at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|WAITING |NEW --- Comment #2 from Steve Ellcey <sje at gcc dot gnu.org> 2012-08-31 00:30:01 UTC --- I think I see where delete_related_insns is going wrong. We call it with a JUMP instruction that we want to remove because we are just jumping to the next instruction (a label) which we would get to anyway without the jump, then after delete_related_insns removes the jump it checks the label it was jumping to, and if it finds no uses it calls delete_related_insns with that label. When delete_related_insns is called with a label, it assumes it can remove all the code after that label as unreachable. But the code after the label can be reached by the default fall-through code sequence. So after removing a jump and finding a label with no uses we should call delete_insn with that label, not delete_related_insns. So my proposed fix would be: diff --git a/gcc/jump.c b/gcc/jump.c index 9721fe1..fa3d65a 100644 --- a/gcc/jump.c +++ b/gcc/jump.c @@ -1207,7 +1207,7 @@ delete_related_insns (rtx insn) /* This can delete NEXT or PREV, either directly if NEXT is JUMP_LABEL (INSN), or indirectly through more levels of jumps. */ - delete_related_insns (lab); + delete_insn (lab); else if (tablejump_p (insn, NULL, &lab_next)) { /* If we're deleting the tablejump, delete the dispatch table.