Re: [PATCH v3 3/3] LoongArch: BPF: Optimize 32-bit operations using native instructions

[Tiezhu Yang]

On 2026/10/27 上午10:02, Hengqi Chen wrote:
> On Fri, Oct 16, 2026 at 4:10 PM Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> wrote:
> > Currently, the LoongArch BPF JIT emits numerous redundant zero and sign
> > extensions across 32-bit operations, bloating the final JIT image size
> > and also leading to runtime overhead, particularly in the division and
> > modulo operations. Thus, it is necessary to optimize 32-bit operations
> > by emitting LoongArch native 32-bit word instructions.

...

> > +               if (cpu_has_div32) {
> > +                       if (!off)
> > +                               emit_insn(ctx, divwu, dst, dst, src);
> > +                       else
> > +                               emit_insn(ctx, divw, dst, dst, src);
>
> For ALU32 SDIV, off != 0, it seems like there is a overflow in S32_MIN / -1.
> verifier_sdiv.c has related test cases but annotate with
> __arch_x86_64, so it is not run on LoongArch.

After enabling the signed division and modulo overflow tests for
LoongArch, here are the test results:

$ sudo ./test_progs -t verifier_sdiv | grep "MIN/-1"
#731/121 verifier_sdiv/SDIV64, overflow r/r, LLONG_MIN/-1:OK
#731/123 verifier_sdiv/SDIV64, overflow r/i, LLONG_MIN/-1:OK
#731/125 verifier_sdiv/SDIV32, overflow r/r, INT_MIN/-1:OK
#731/127 verifier_sdiv/SDIV32, overflow r/i, INT_MIN/-1:OK
#731/129 verifier_sdiv/SMOD64, overflow r/r, LLONG_MIN/-1:OK
#731/131 verifier_sdiv/SMOD64, overflow r/i, LLONG_MIN/-1:OK
#731/133 verifier_sdiv/SMOD32, overflow r/r, INT_MIN/-1:OK
#731/135 verifier_sdiv/SMOD32, overflow r/i, INT_MIN/-1:OK

That is to say, the current jit code is no problem.

Thanks,
Tiezhu