[PATCH 1/2] sbi: Introduce sbi_hartmask_weight

[Xiang W]

在 2025-03-14五的 17:30 +0100，Andrew Jones写道：
> Provide a function to count the number of set bits in a hartmask,
> which builds on a new function for the same that operates on a
> bitmask. While at it, improve the performance of sbi_popcount()
> which is used in the implementation.
> 
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
> ---
>  include/sbi/sbi_bitmap.h   | 13 +++++++++++++
>  include/sbi/sbi_bitops.h   | 22 +++++++++++++++-------
>  include/sbi/sbi_hartmask.h | 11 +++++++++++
>  3 files changed, 39 insertions(+), 7 deletions(-)
> 
> diff --git a/include/sbi/sbi_bitmap.h b/include/sbi/sbi_bitmap.h
> index 354476c9dd81..596bcc7daa87 100644
> --- a/include/sbi/sbi_bitmap.h
> +++ b/include/sbi/sbi_bitmap.h
> @@ -130,4 +130,17 @@ static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1,
>  		__bitmap_xor(dst, src1, src2, nbits);
>  }
>  
> +static inline int bitmap_weight(const unsigned long *src, int nbits)
> +{
> +	int i, res = 0;
> +
> +	for (i = 0; i < nbits / BITS_PER_LONG; i++)
> +		res += sbi_popcount(src[i]);
> +
> +	if (nbits % BITS_PER_LONG)
> +		res += sbi_popcount(src[i] & BITMAP_LAST_WORD_MASK(nbits));
> +
> +	return res;
> +}
> +
>  #endif
> diff --git a/include/sbi/sbi_bitops.h b/include/sbi/sbi_bitops.h
> index 3ddac777d887..d7825e81ea05 100644
> --- a/include/sbi/sbi_bitops.h
> +++ b/include/sbi/sbi_bitops.h
> @@ -125,14 +125,22 @@ static inline unsigned long sbi_fls(unsigned long word)
>   */
>  static inline unsigned long sbi_popcount(unsigned long word)
>  {
> -	unsigned long count = 0;
> +	unsigned long count;
>  
> -	while (word) {
> -		word &= word - 1;
> -		count++;
> -	}
> -
> -	return count;
> +#if BITS_PER_LONG == 64
> +	count = word - ((word >> 1) & 0x5555555555555555ul);
> +	count = (count & 0x3333333333333333ul) + ((count >> 2) & 0x3333333333333333ul);
> +	count = (count + (count >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
> +	count = count + (count >> 8);
> +	count = count + (count >> 16);
> +	return (count + (count >> 32)) & 0x00000000000000FFul;
> +#else
> +	count = word - ((word >> 1) & 0x55555555);
> +	count = (count & 0x33333333) + ((count >> 2) & 0x33333333);
> +	count = (count + (count >> 4)) & 0x0F0F0F0F;
> +	count = count + (count >> 8);
> +	return (count + (count >> 16)) & 0x000000FF;
> +#endif
This is an optimisation that can be put into a separate patch

Regards,
Xiang W

>  }
>  
>  #define for_each_set_bit(bit, addr, size) \
> diff --git a/include/sbi/sbi_hartmask.h b/include/sbi/sbi_hartmask.h
> index 07a8c076bd0a..200ab6e53e4c 100644
> --- a/include/sbi/sbi_hartmask.h
> +++ b/include/sbi/sbi_hartmask.h
> @@ -181,6 +181,17 @@ static inline void sbi_hartmask_xor(struct sbi_hartmask *dstp,
>  		   sbi_hartmask_bits(src2p), SBI_HARTMASK_MAX_BITS);
>  }
>  
> +/**
> + * Count of bits in *srcp
> + * @param srcp the hartmask to count bits in
> + *
> + * Return: count of bits set in *srcp
> + */
> +static inline int sbi_hartmask_weight(const struct sbi_hartmask *srcp)
> +{
> +	return bitmap_weight(sbi_hartmask_bits(srcp), SBI_HARTMASK_MAX_BITS);
> +}
> +
>  /**
>   * Iterate over each HART index in hartmask
>   * __i hart index
> -- 
> 2.48.1
>