Re: [PATCH v5 2/2] x86/asm/bitops: __ffs,ffz: use __builtin_ctzl to evaluate constant expressions

[Borislav Petkov]

On Tue, Aug 23, 2022 at 10:12:17AM -0700, Nick Desaulniers wrote:
> Callers of these need to guard against zero input, as the pre-existing
> comment notes:
> 
> >> Undefined if no bit exists, so code should check against 0 first.

This is just silly.

And then there's

 * ffs(value) returns 0 if value is 0 or the position of the first
 * set bit if value is nonzero. The first (least significant) bit
 * is at position 1.
 */
static __always_inline int ffs(int x)

Can we unify the two and move the guard against 0 inside the function
or, like ffs() does, have it return 0 if value is 0?

-- 
Regards/Gruss,
    Boris.

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