Hi,
On Mon, 8 Oct 2018, Paul Koning wrote:
> > So all you'd actually have to say is
> >
> > void f1(void)
> > {
> > *i; *j;
> > __builtin_memcpy (i, j, 32);
> > }
>
> No, that doesn't help. Not even if I make it:
>
> void f1(void)
> {
> k = *i + *j;
> __builtin_memcpy (i, j, 4);
> }
>
> The first line does word aligned references to *i and *j, but the memcpy
> stubbornly remains a byte move.
k is a global, so the loads from i/j can't be optimized away? If so, now
you have a missed optimization bug ;-) Might be non-trivial to fix for
general situations (basically the natural alignment can only be inferred
in regions that are dominated by such accesses, but not e.g. for:
if (cond()) k = *i+*j;
memcpy(i,j,4);
as cond() might be always false).
Ciao,
Michael.
