https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104480
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Version|unknown |12.0
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I don't think [intro.memory]/3 (wherever that should point to?) is realized
this way on CPUs with a less strong memory ordering guarantee than x86. And we
definitely do not ensure atomicity or commit order unless you use atomic access
primitives.
So I think this is invalid. As Andrew says we're happily combining
void foo (double * __restrict a, double *b)
{
a[0] = b[0];
a[1] = b[1];
}
into
movupd (%rsi), %xmm0
movups %xmm0, (%rdi)
since forever using vectorization which would have the exact same issue
when the store crosses a cacheline boundary.
