On Tue, Aug 25, 2020 at 5:19 PM Arvind Sankar <[email protected]> wrote: > > 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.
Thanks for taking care and your patch. I have tested this on top of Linux v5.9-rc2 with LLVM toolchain v11.0.0-rc2 (ThinLTO). Tested-by: Sedat Dilek <[email protected]> - Sedat -
