On Thu, May 7, 2020 at 7:38 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Tue, May 05, 2020 at 11:07:24AM -0700, hpa@xxxxxxxxx wrote:
> > On May 5, 2020 10:44:22 AM PDT, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
>
> > >@@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long *addr)
> > > if (__builtin_constant_p(nr)) {
> > > asm volatile(LOCK_PREFIX "orb %1,%0"
> > > : CONST_MASK_ADDR(nr, addr)
> > >- : "iq" (CONST_MASK(nr) & 0xff)
> > >+ : "iq" ((u8)(CONST_MASK(nr) & 0xff))
> > > : "memory");
> > > } else {
> > > asm volatile(LOCK_PREFIX __ASM_SIZE(bts) " %1,%0"
> > >@@ -74,7 +74,7 @@ arch_clear_bit(long nr, volatile unsigned long *addr)
> > > if (__builtin_constant_p(nr)) {
> > > asm volatile(LOCK_PREFIX "andb %1,%0"
> > > : CONST_MASK_ADDR(nr, addr)
> > >- : "iq" (CONST_MASK(nr) ^ 0xff));
> > >+ : "iq" ((u8)(CONST_MASK(nr) ^ 0xff)));
> > > } else {
> > > asm volatile(LOCK_PREFIX __ASM_SIZE(btr) " %1,%0"
> > > : : RLONG_ADDR(addr), "Ir" (nr) : "memory");
> >
> > Drop & 0xff and change ^ 0xff to ~.
>
> But then we're back to sparse being unhappy, no? The thing with ~ is
> that it will set high bits which will be truncated, which makes sparse
> sad.
This change will make sparse happy and allow these cleanups:
#define CONST_MASK(nr) ((u8)1 << ((nr) & 7))
Tested with GCC 9.3.1.
--
Brian Gerst
