On Mon, Aug 24, 2020 at 09:13:34PM +0200, Miguel Ojeda wrote: > Hi Arvind, > > On Sun, Aug 23, 2020 at 11:25 PM Arvind Sankar <[email protected]> wrote: > > > > - Using a dummy input operand with an arbitrary constant address for the > > read functions, instead of a global variable. This will prevent reads > > from being reordered across writes, while allowing memory loads to be > > cached/reordered across CRn reads, which should be safe. > > Assuming no surprises from compilers, this looks better than dealing > with different code for each compiler. > > > Signed-off-by: Arvind Sankar <[email protected]> > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82602 > > A lore link to the other discussion would be nice here for context. >
Ok. > > + * The compiler should not reorder volatile asm, however older versions of > > GCC > > + * had a bug (which was fixed in 8.1, 7.3 and 6.5) where they could > > sometimes > > I'd mention the state of GCC 5 here. > Ok. > > + * reorder volatile asm. The write functions are not a problem since they > > have > > + * memory clobbers preventing reordering. To prevent reads from being > > reordered > > + * with respect to writes, use a dummy memory operand. > > */ > > -extern unsigned long __force_order; > > + > > Spurious newline? > This was intentional, but I can remove it if people don't like the extra whitespace. I'll wait a few days for additional review comments before sending v2. Thanks.
