https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97708
--- Comment #29 from Segher Boessenkool <segher at gcc dot gnu.org> --- (In reply to Richard Biener from comment #26) > So it would need to be diagnosed in the FE (only), making a + 0 valid and > a not. Eh. We do not *have* to diagnose anything, certainly not things that just happen to work (if "a+0" is optimised to just "a", say). But it would be good if we could diagnose the obvious and certainly wrong cases we do not do now -- like a register asm that does not match the operand constraint!