linux-kernel - Re: [PATCH] LoongArch: vDSO: vgetrandom-chacha: Make use of the t8 register

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Message-ID: <CAAhV-H4uacrS-kgvvrTQAGxdsGDsjDeE=eb6BcdCjRdgw8HLRg@mail.gmail.com>
Date: Tue, 25 Feb 2025 20:43:23 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Xi Ruoyao <xry111@...111.site>
Cc: WANG Xuerui <kernel@...0n.name>, "Jason A. Donenfeld" <Jason@...c4.com>, linux-crypto@...r.kernel.org, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: vDSO: vgetrandom-chacha: Make use of the t8 register

Applied, thanks.

Huacai

On Fri, Feb 21, 2025 at 7:34 PM Xi Ruoyao <xry111@...111.site> wrote:
>
> So we don't need to reuse a register and rematerialize a constant.  I
> couldn't count :(.
>
> Signed-off-by: Xi Ruoyao <xry111@...111.site>
> ---
>
> Tested with vdso_test_getrandom and vdso_test_chacha.
>
>  arch/loongarch/vdso/vgetrandom-chacha.S | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/arch/loongarch/vdso/vgetrandom-chacha.S b/arch/loongarch/vdso/vgetrandom-chacha.S
> index c2733e6c3a8d..c4dd2bab8825 100644
> --- a/arch/loongarch/vdso/vgetrandom-chacha.S
> +++ b/arch/loongarch/vdso/vgetrandom-chacha.S
> @@ -58,9 +58,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>  #define copy0          t5
>  #define copy1          t6
>  #define copy2          t7
> -
> -/* Reuse i as copy3 */
> -#define copy3          i
> +#define copy3          t8
>
>  /* Packs to be used with OP_4REG */
>  #define line0          state0, state1, state2, state3
> @@ -99,6 +97,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>         li.w            copy0, 0x61707865
>         li.w            copy1, 0x3320646e
>         li.w            copy2, 0x79622d32
> +       li.w            copy3, 0x6b206574
>
>         ld.w            cnt_lo, counter, 0
>         ld.w            cnt_hi, counter, 4
> @@ -108,7 +107,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>         move            state0, copy0
>         move            state1, copy1
>         move            state2, copy2
> -       li.w            state3, 0x6b206574
> +       move            state3, copy3
>
>         /* state[4,5,..,11] = key */
>         ld.w            state4, key, 0
> @@ -167,12 +166,6 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>         addi.w          i, i, -1
>         bnez            i, .Lpermute
>
> -       /*
> -        * copy[3] = "expa", materialize it here because copy[3] shares the
> -        * same register with i which just became dead.
> -        */
> -       li.w            copy3, 0x6b206574
> -
>         /* output[0,1,2,3] = copy[0,1,2,3] + state[0,1,2,3] */
>         OP_4REG add.w   line0, copy
>         st.w            state0, output, 0
> --
> 2.48.1
>