Re: [PATCH] LoongArch: implement count_{leading,trailing}_zeros

[Lulu Cheng <chenglulu@loongson.cn>]

Looks good to me!

Thanks!

在 2022/10/12 下午10:23, Xi Ruoyao 写道:
> LoongArch always support clz and ctz instructions, so we can always use
> __builtin_{clz,ctz} for count_{leading,trailing}_zeros.  This improves
> the code of libgcc, and also benefits Glibc once we merge longlong.h
> there.
>
> Bootstrapped and regtested on loongarch64-linux-gnu.
>
> include/ChangeLog:
>
> 	* longlong.h [__loongarch__] (count_leading_zeros): Define.
> 	[__loongarch__] (count_trailing_zeros): Likewise.
> 	[__loongarch__] (COUNT_LEADING_ZEROS_0): Likewise.
> ---
>   include/longlong.h | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
>
> diff --git a/include/longlong.h b/include/longlong.h
> index 64a7b10f9b2..c3a6f1e7eaa 100644
> --- a/include/longlong.h
> +++ b/include/longlong.h
> @@ -593,6 +593,18 @@ extern UDItype __umulsidi3 (USItype, USItype);
>   #define UMUL_TIME 14
>   #endif
>   
> +#ifdef __loongarch__
> +# if W_TYPE_SIZE == 32
> +#  define count_leading_zeros(count, x)  ((count) = __builtin_clz (x))
> +#  define count_trailing_zeros(count, x) ((count) = __builtin_ctz (x))
> +#  define COUNT_LEADING_ZEROS_0 32
> +# elif W_TYPE_SIZE == 64
> +#  define count_leading_zeros(count, x)  ((count) = __builtin_clzll (x))
> +#  define count_trailing_zeros(count, x) ((count) = __builtin_ctzll (x))
> +#  define COUNT_LEADING_ZEROS_0 64
> +# endif
> +#endif
> +
>   #if defined (__M32R__) && W_TYPE_SIZE == 32
>   #define add_ssaaaa(sh, sl, ah, al, bh, bl) \
>     /* The cmp clears the condition bit.  */ \