Re: [PATCH v9 03/15] xen/bitops: implement fls{l}() in common logic

[Oleksii K.]

On Wed, 2024-05-15 at 11:09 +0200, Jan Beulich wrote:
> But this then needs carrying through to ...
> 
> > --- a/xen/arch/arm/include/asm/arm64/bitops.h
> > +++ b/xen/arch/arm/include/asm/arm64/bitops.h
> > @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long
> > __ffs(unsigned long word)
> >    */
> >   #define ffz(x)  __ffs(~(x))
> >   
> > -static inline int flsl(unsigned long x)
> > +static inline int arch_flsl(unsigned long x)
> 
> ... e.g. here. You don't want to introduce signed/unsigned
> mismatches.
Is it critical for x86 to return int for flsl() and fls() or I can
update the return type for x86 too?

   static always_inline int arch_flsl(unsigned long x)
   {
       long r;
   
       asm ( "bsr %1,%0\n\t"
             "jnz 1f\n\t"
             "mov $-1,%0\n"
             "1:" : "=r" (r) : "rm" (x));
       return (int)r+1;
   }
   #define arch_flsl arch_flsl
   
   static always_inline int arch_fls(unsigned int x)
   {
       int r;
   
       asm ( "bsr %1,%0\n\t"
             "jnz 1f\n\t"
             "mov $-1,%0\n"
             "1:" : "=r" (r) : "rm" (x));
       return r + 1;
   }
   #define arch_fls arch_fls

Any specific reason why 'long' and 'int' types for r are used?

~ Oleksii