aio-libs / multidict / 37457516812

86%

push

github

Move md_eq() and md_eq_to_mapping() out of line (#1703)

<!-- Thank you for your contribution! -->

## What do these changes do?

Marks `md_eq()` and `md_eq_to_mapping()` in `hashtable.h` as `NOINLINE`,
so GCC stops inlining both into `multidict_tp_richcompare()`.
`_md_eq_to_mapping_scan()` is folded into `md_eq_to_mapping()`, which
now reads the table kind at run time instead of keeping a copy per kind.
Equality is not a hot path.

On the FT build this costs `d[key] = v` on an existing key 4
instructions: GCC emits one more out-of-line `Py_DECREF` call in
`md_replace_cs()`, which gives back what #1693 won. Either `NOINLINE`
alone is enough to trigger it, with or without the fold.

Pure Python has no equivalent.

## Are there changes in behavior for the user?

No.

## Is it a substantial burden for the maintainers to support this?

No.

## Related issue number

N/A

## Checklist

- [x] I think the code is well written
- [ ] Unit tests for the changes exist (N/A, no behavior change)
- [x] Documentation reflects the changes (N/A)
- [ ] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt` (N/A)
- [x] Add a new news fragment into the `CHANGES/` folder
- [x] `make doc-spelling` passes and any new technical words are added
to `docs/spelling_wordlist.txt`

Drafted with Claude Code (Claude Opus 5.5); reviewed by @asvetlov.

<details>
<summary>Agent run details (optional, for reviewers)</summary>

`.text` (GCC 15, pip build): GIL 244736 → 244416 (−320 B), FT 249936 →
250048 (+112 B).

Callgrind: `benchmarks/callgrind_driver.py --include-multidict-only`,
`PYTHONHASHSEED=0`, 3.14.7 and 3.14.7t. Every GIL C row is within ±0.1%.
FT rows that moved:

| op | FT |
| --- | --- |
| MultiDict `d[key] = v`, existing key | 442.4 → 446.4 (+0.9%) |
| MultiDict `d[istr] = v` | 981.1 → 985.1 (+0.4%) |
| CIMultiDict `pop` | 544.2 → 545.2 (+0.2%) |

The driver has no equality operation, so `==` was measured separately
(Ir per comparison, 20 keys, callgrin... (continued)

793 of 1586 branches covered (50.0%)

Branch coverage included in aggregate %.

9353 of 10217 relevant lines covered (91.54%)

1.83 hits per line