movmem pattern and missed alignment

[Jakub Jelinek]

On Tue, Oct 09, 2018 at 11:08:44AM +0200, Richard Biener wrote:
> On Tue, Oct 9, 2018 at 11:00 AM Alexander Monakov <amonakov@ispras.ru> wrote:
> >
> > On Tue, 9 Oct 2018, Richard Biener wrote:
> > >
> > > then we cannot set the alignment of i_1 at/after k = *i_1 because doing so would
> > > affect the alignment test which we'd then optimize away.  We'd need to introduce
> > > a SSA copy to get a new SSA name but that would be optimized away quickly.
> >
> > We preserve __builtin_assume_aligned up to pass-fold-all-builtins, so would it
> > work to emit it just before the memcpy
> >
> >   i_2 = __builtin_assume_aligned(i_1, 4);
> >   __builtin_memcpy(j, i_2, 32);
> >
> > in theory?
> 
> That's still before RTL expansion so I'm not sure that is enough.

But we likely won't invalidate the computed SSA_NAME_INFO afterwards.

	Jakub