From: Zeng Zhaoxiu <zhaoxiu.z...@gmail.com> Date: Mon, 28 Mar 2016 13:44:03 +0800
> 在 2016年03月28日 10:43, David Miller 写道: >> From: "zhaoxiu.zeng" <zhaoxiu.z...@gmail.com> >> Date: Sun, 27 Mar 2016 14:43:10 +0800 >> >>> + >>> +/* >>> + * parityN: returns the parity of a N-bit word, >>> + * i.e. the number of 1-bits in x modulo 2. >>> + */ >>> + >>> +#define __arch_parity4(w) (__arch_hweight8((w) & 0xf) & 1) >>> +#define __arch_parity8(w) (__arch_hweight8(w) & 1) >>> +#define __arch_parity16(w) (__arch_hweight16(w) & 1) >>> +#define __arch_parity32(w) (__arch_hweight32(w) & 1) >>> +#define __arch_parity64(w) ((unsigned int)__arch_hweight64(w) & 1) >> This looks like asm-generic/ material to me. > > This is generic for the architectures which have popcount instruction, > but more higher costs than asm-generic/ for others. Which is why said stanza's in the asm-generic header should be triggered by a CPP define or similar.
