linux-kernel - Re: [PATCH v3 1/5] LoongArch: Add the function to generate the beq and bne assembly instructions.

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Message-ID: <CAEyhmHSB32tPYbUKqqxFWQqnyDGcNPQsCqBKGdNRrn+U+jMimw@mail.gmail.com>
Date: Wed, 16 Jul 2025 19:33:51 +0800
From: Hengqi Chen <hengqi.chen@...il.com>
To: Chenghao Duan <duanchenghao@...inos.cn>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	yangtiezhu@...ngson.cn, chenhuacai@...nel.org, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, kernel@...0n.name, 
	linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev, bpf@...r.kernel.org, 
	guodongtai@...inos.cn, youling.tang@...ux.dev, jianghaoran@...inos.cn, 
	Youling Tang <tangyouling@...inos.cn>
Subject: Re: [PATCH v3 1/5] LoongArch: Add the function to generate the beq
 and bne assembly instructions.

On Wed, Jul 9, 2025 at 1:50 PM Chenghao Duan <duanchenghao@...inos.cn> wrote:
>
> Add branch jump function:
> larch_insn_gen_beq
> larch_insn_gen_bne
>

Please drop the period from subject line.
The commit message is kind of vague...

Maybe:
    LoongArch: Add larch_insn_gen_{beq,bne} helpers

    Add larch_insn_gen_beq() and larch_insn_gen_bne() helpers
    which will be used in BPF trampoline implementation.


> Co-developed-by: George Guo <guodongtai@...inos.cn>
> Signed-off-by: George Guo <guodongtai@...inos.cn>
> Co-developed-by: Youling Tang <tangyouling@...inos.cn>
> Signed-off-by: Youling Tang <tangyouling@...inos.cn>
> Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
> ---
>  arch/loongarch/include/asm/inst.h |  2 ++
>  arch/loongarch/kernel/inst.c      | 28 ++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
> index 3089785ca..2ae96a35d 100644
> --- a/arch/loongarch/include/asm/inst.h
> +++ b/arch/loongarch/include/asm/inst.h
> @@ -511,6 +511,8 @@ u32 larch_insn_gen_lu12iw(enum loongarch_gpr rd, int imm);
>  u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm);
>  u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
>  u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
> +u32 larch_insn_gen_beq(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
> +u32 larch_insn_gen_bne(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
>
>  static inline bool signed_imm_check(long val, unsigned int bit)
>  {
> diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
> index 14d7d700b..674e3b322 100644
> --- a/arch/loongarch/kernel/inst.c
> +++ b/arch/loongarch/kernel/inst.c
> @@ -336,3 +336,31 @@ u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm)
>
>         return insn.word;
>  }
> +
> +u32 larch_insn_gen_beq(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm)
> +{
> +       union loongarch_instruction insn;
> +
> +       if ((imm & 3) || imm < -SZ_128K || imm >= SZ_128K) {
> +               pr_warn("The generated beq instruction is out of range.\n");
> +               return INSN_BREAK;
> +       }
> +
> +       emit_beq(&insn, rj, rd, imm >> 2);
> +
> +       return insn.word;
> +}
> +
> +u32 larch_insn_gen_bne(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm)
> +{
> +       union loongarch_instruction insn;
> +
> +       if ((imm & 3) || imm < -SZ_128K || imm >= SZ_128K) {
> +               pr_warn("The generated bne instruction is out of range.\n");
> +               return INSN_BREAK;
> +       }
> +
> +       emit_bne(&insn, rj, rd, imm >> 2);
> +
> +       return insn.word;
> +}
> --
> 2.43.0
>