Re: [PATCH bpf-next v1 3/4] LoongArch: Add BPF JIT support

[Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>]

On 08/22/2022 09:58 AM, Youling Tang wrote:
> On 08/20/2022 07:50 PM, Tiezhu Yang wrote:
> > BPF programs are normally handled by a BPF interpreter, add BPF JIT
> > support for LoongArch to allow the kernel to generate native code
> > when a program is loaded into the kernel, this will significantly
> > speed-up processing of BPF programs.

[...]

> > +#define DEF_EMIT_REG1I20_FORMAT(NAME, OP)                \
> > +static inline void emit_##NAME(union loongarch_instruction *insn,    \
> > +                   enum loongarch_gpr rd, int imm)        \
> > +{                                    \
> > +    insn->reg1i20_format.opcode = OP;                \
> > +    insn->reg1i20_format.immediate = imm;                \
> > +    insn->reg1i20_format.rd = rd;                    \
> > +}
> > +
> > +DEF_EMIT_REG1I20_FORMAT(lu12iw, lu12iw_op)
> > +DEF_EMIT_REG1I20_FORMAT(lu32id, lu32id_op)
>
> We can delete the larch_insn_gen_{lu32id, lu52id, jirl} functions in
> inst.c and use emit_xxx.
>
> The implementation of emit_plt_entry() is similarly modified as follows:
> struct plt_entry {
>         union loongarch_instruction lu12iw;
>         union loongarch_instruction lu32id;
>         union loongarch_instruction lu52id;
>         union loongarch_instruction jirl;
> };
>
> static inline struct plt_entry emit_plt_entry(unsigned long val)
> {
>         union loongarch_instruction *lu12iw, *lu32id, *lu52id, *jirl;
>
>         emit_lu32id(lu12iw, LOONGARCH_GPR_T1, ADDR_IMM(val, LU12IW));
>         emit_lu32id(lu32id, LOONGARCH_GPR_T1, ADDR_IMM(val, LU32ID));
>         emit_lu52id(lu52id, LOONGARCH_GPR_T1, LOONGARCH_GPR_T1,
> ADDR_IMM(val, LU52ID));
>         emit_jirl(jirl, LOONGARCH_GPR_T1, 0, (val & 0xfff) >> 2);
>
>         return (struct plt_entry) { *lu12iw, *lu32id, *lu52id, *jirl };
> }
>
> Thanks,
> Youling

Hi Youling,

Yes, this is the benefit we define the instructions in inst.h,
but these changes are not much related with this patch series,
I think we can do it after this patch series is merged.

Thanks,
Tiezhu