netfilter: nft_set_pipapo_avx2: restore performance optimization

The avx2 lookup routines get the next map index to process passes as a
function argument, but this isn't obvious because it's hidden in the
lookup macro.

Additionally, a recent LLM review pointed out following "bug":
 -------------------------------------------------------------
 >               b = nft_pipapo_avx2_refill(i_ul, &map[i_ul], fill, f->mt, last);
 >               if (last)
 > -                     return b;
 > +                     ret = b;
 >
 >               if (unlikely(ret == -1))
 >                       ret = b / XSAVE_YMM_SIZE;

 Does this change introduce a logic error when last=true and no match is
 found? [..]

 Should this be changed to an else-if structure instead?
 -------------------------------------------------------------

LLM sees a control-flow change, but there is none:

All call sites invoke nft_pipapo_avx2_refill() only when at least one
bit in the map is set, i.e. nft_pipapo_avx2_refill() never returns -1.

Add a runtime debug check that fires if we'd return -1 as additional
documentation and also make the suggested change, code might be easier
to understand this way.

In commit 17a20e09f086 ("netfilter: nft_set: remove one argument from
lookup and update functions") I incorrectly moved the "ret" scope into
the loop.

This has no effect on the correctness, but it can (depending on map sizes)
cause a redundant repeat of an earlier processing step.

Restore the intended 'pass map index' instead of always-0.  Note that I
did not see any change in performance numbers, but Stefano correctly
points out that the existing perf test likely lack a sparse intermediate
bitmap (between fields) with a lot of leading zeroes.

Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

0 files changed, 0 insertions, 0 deletions