Re: [PATCH bpf-next v2 0/4] bpf: replace min/max fields with struct cnum{32,64}

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2026-04-24 at 07:27 -0700, Alexei Starovoitov wrote:
> On Fri Apr 24, 2026 at 1:17 AM PDT, Eduard Zingerman wrote:
> > This RFC replaces s64, u64, s32, u32 scalar range domains tracked by
> > verifier by a pair of circular numbers (cnums): one for 64-bit domain
> > and another for 32-bit domain. Each cnum represents a range as a
> > single arc on the circular number line, from which signed and unsigned
> > bounds are derived on demand. See also wrapped intervals
> > representation as in [1].
> > 
> > The use of such representation simplifies arithmetic and conditions
> > handling in verifier.c and allows to express 32 <-> 64 bit deductions
> > in a more mathematically rigorous way.
> > 
> > [1] https://jorgenavas.github.io/papers/ACM-TOPLAS-wrapped.pdf
> > 
> > Changelog
> > =========
> > RFCv1 -> v2:
> > - Dropped RFC tag.
> > - Dropped cnum{32,64}_mul(), too much complexity and no veristat
> >   or selftests gains.
> 
> Nice. Less complexity the better.
> I think it's also strong signal that _div(), _mod() versions are not
> needed either.

It might be the case, yes.
The 'union' function from RFCv1 would be needed later,
if we plan to build data flow analyses on top of cnums.
I have v3 with fixes in comments on stand-by.
Hope to hear some thoughts from Shung-Hsi, Paul, Harishankar.