Hi Arvind, On Sun, Aug 23, 2020 at 11:25 PM Arvind Sankar <nived...@alum.mit.edu> 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 <nived...@alum.mit.edu> > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82602 A lore link to the other discussion would be nice here for context. > + * 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. > + * 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? Cheers, Miguel
