Alexei Starovoitov wrote:
> On Thu, Sep 24, 2020 at 11:45 AM John Fastabend
> <john.fastabend@xxxxxxxxx> wrote:
> >
> > In BPF_AND and BPF_OR alu cases we have this pattern when the src and dst
> > tnum is a constant.
> >
> > 1 dst_reg->var_off = tnum_[op](dst_reg->var_off, src_reg.var_off)
> > 2 scalar32_min_max_[op]
> > 3 if (known) return
> > 4 scalar_min_max_[op]
> > 5 if (known)
> > 6 __mark_reg_known(dst_reg,
> > dst_reg->var_off.value [op] src_reg.var_off.value)
> >
> > The result is in 1 we calculate the var_off value and store it in the
> > dst_reg. Then in 6 we duplicate this logic doing the op again on the
> > value.
> >
> > The duplication comes from the the tnum_[op] handlers because they have
> > already done the value calcuation. For example this is tnum_and().
> >
> > struct tnum tnum_and(struct tnum a, struct tnum b)
> > {
> > u64 alpha, beta, v;
> >
> > alpha = a.value | a.mask;
> > beta = b.value | b.mask;
> > v = a.value & b.value;
> > return TNUM(v, alpha & beta & ~v);
> > }
> >
> > So lets remove the redundant op calculation. Its confusing for readers
> > and unnecessary. Its also not harmful because those ops have the
> > property, r1 & r1 = r1 and r1 | r1 = r1.
> >
> > Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
>
> Applied. Thanks for the follow up.
> In the future please always cc bpf@vger for two reasons:
> - to get proper 'Link:' integrated in git commit
> - to get them into a new instance of
> https://patchwork.kernel.org/project/bpf/list
+1
> which we will start using soon to send automatic 'applied' emails.
Apologies, I updated some scripts and unfortunately typo dropped a '-'
and cut off bpf@vger from the CC list. Also I just used it to land
two more patches without bpf@vger happy to resend with CC included
if folks want. Sorry for the extra work/noise.
Thanks.
