http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54900
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |aldyh at gcc dot gnu.org, | |jakub at gcc dot gnu.org --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-10-11 11:59:14 UTC --- This is ifcvt.c in action. This is the if (!set_b && MEM_P (orig_x)) case where we already do some checks: if (noce_mem_write_may_trap_or_fault_p (orig_x)) return FALSE; and if (!noce_can_store_speculate_p (test_bb, orig_x)) return FALSE; I'd say noce_can_store_speculate_p is buggy, it uses if (memory_modified_in_insn_p (mem, insn)) return true; but memory_modified_in_insn_p is pessimistic, it doesn't tell whether mem is surely set, but whether it might be set. I guess it would need to use note_stores that would just do rtx_equal_p on the addresses or similarly prove it is surely (and unconditionally) written. So even note_stores might not be the right thing, perhaps just looking at single_set SET_DEST. And avoiding inline asm, that doesn't have to store unconditionally.