linux-kernel - Re: [PATCH] powerpc/mm/hash: Code cleanup

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Date: Thu, 25 Jan 2024 19:17:39 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>
To: Kunwu Chan <chentao@...inos.cn>, mpe@...erman.id.au, npiggin@...il.com,
 christophe.leroy@...roup.eu, naveen.n.rao@...ux.ibm.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/mm/hash: Code cleanup

On 1/25/24 3:16 PM, Kunwu Chan wrote:
> This part was commented in about 17 years before.
> If there are no plans to enable this part code in the future,
> we can remove this dead code.
> 
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
> ---
>  arch/powerpc/include/asm/book3s/64/mmu-hash.h | 22 -------------------
>  1 file changed, 22 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> index 1c4eebbc69c9..d39ec7134a78 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> @@ -731,26 +731,6 @@ struct hash_mm_context {
>  #endif /* CONFIG_PPC_SUBPAGE_PROT */
>  };
>  
> -#if 0
> -/*
> - * The code below is equivalent to this function for arguments
> - * < 2^VSID_BITS, which is all this should ever be called
> - * with.  However gcc is not clever enough to compute the
> - * modulus (2^n-1) without a second multiply.
> - */
> -#define vsid_scramble(protovsid, size) \
> -	((((protovsid) * VSID_MULTIPLIER_##size) % VSID_MODULUS_##size))
> -
> -/* simplified form avoiding mod operation */
> -#define vsid_scramble(protovsid, size) \
> -	({								 \
> -		unsigned long x;					 \
> -		x = (protovsid) * VSID_MULTIPLIER_##size;		 \
> -		x = (x >> VSID_BITS_##size) + (x & VSID_MODULUS_##size); \
> -		(x + ((x+1) >> VSID_BITS_##size)) & VSID_MODULUS_##size; \
> -	})
> -
> -#else /* 1 */
>  static inline unsigned long vsid_scramble(unsigned long protovsid,
>  				  unsigned long vsid_multiplier, int vsid_bits)
>  {
> @@ -764,8 +744,6 @@ static inline unsigned long vsid_scramble(unsigned long protovsid,
>  	return (vsid + ((vsid + 1) >> vsid_bits)) & vsid_modulus;
>  }
>  
> -#endif /* 1 */
> -
>  /* Returns the segment size indicator for a user address */
>  static inline int user_segment_size(unsigned long addr)
>  {

That was done to make sure one can follow the actual compiled code better. 

-aneesh