https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100672
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Zdenek Sojka from comment #7)
> (In reply to Richard Biener from comment #2)
> > Maybe sth is wrong with the testcase? clang also results in an abort.
> > Isn't
> > right-shift of negative values undefined?
> >
>
> Thank you for having a look.
>
> I believe the behavior is fully defined. The vectors are unsigned, and the
> conversion to unsigned is done by adding 2**64; this behaves the same:
>
> $ cat testcase.c
> typedef unsigned long long __attribute__((__vector_size__ (32))) V;
>
> V
> foo (V v)
> {
> return -(v >> 1);
but this is a logical right shift, thus gives 0x7ff...e, ...
and negating that doesn't yield 1.
> }
>
> int
> main (void)
> {
> V v = foo ((V) { 0xfffffffffffffffe, 0xfffffffffffffffc,
> 0xfffffffffffffffa, 0xfffffffffffffff8 });
> if (v[0] != 1 || v[1] != 2 || v[2] != 3 || v[3] != 4)
> __builtin_abort ();
> return 0;
> }
>
> Maybe clang behaves the same since the behavior was the same in the moment
> when clang was forked.
