> On Oct 8, 2018, at 1:29 PM, Andrew Haley <a...@redhat.com> wrote:
>
> On 10/08/2018 06:20 PM, Michael Matz wrote:
>> Only if you somewhere visibly add accesses to *i and *j. Without them you
>> only have the "accesses" via memcpy, and as Richi says, those don't imply
>> any alignment requirements. The i and j pointers might validly be char*
>> pointers in disguise and hence be in fact only 1-aligned. I.e. there's
>> nothing in your small example program from which GCC can infer that those
>> two global pointers are in fact 2-aligned.
>
> 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.
paul
