On Wed, Oct 18, 2017 at 06:30:23AM -0500, Segher Boessenkool wrote: > On Wed, Oct 18, 2017 at 11:10:48AM +0000, Bernd Edlinger wrote: > > A memory clobber would also make rtx_moveable_p return false, > > thru the following case: > > > > case MEM: > > if (type == OP_IN && MEM_READONLY_P (x)) > > return rtx_moveable_p (&XEXP (x, 0), OP_IN); > > return false; > > > > ... > > > > case CLOBBER: > > return rtx_moveable_p (&SET_DEST (x), OP_OUT); > > > > > > because that memory clobber is in a parallel statement > > together with the ASM_OUTPUT. > > > > Right? > > Yes, that looks correct. And a memory clobber of course _should_ make > the insn non-moveable as well -- it's an unknown side effect all by > itself :-)
Actually, it is not a side effect... Just kind of behaves like it. But it does *not* prevent the asm from being deleted, for example. Segher
