T-compiler Meeting Agenda 2024-01-04
Announcements
- Reminder: if you see a PR/issue that seems like there might be legal implications due to copyright/IP/etc, please let us know (or at least message @davidtwco or @Wesley Wiser so we can pass it along).
Other WG meetings (calendar link)
- No meetings scheduled for next week
MCPs/FCPs
- New MCPs (take a look, see if you like them!)
- “Start using clippy on rustc” compiler-team#709
- “Promote tier 3
*-pc-windows-gnullvmtargets to tier 2” compiler-team#710
WG checkins
No checkins this week
Backport nominations
T-compiler stable / T-compiler beta
- [beta] Fix: Properly set vendor in i686-win7-windows-msvc target" rustc#119544
- No stable nominations for
T-compilerthis time.
- No beta nominations for
T-typesthis time. - No stable nominations for
T-typesthis time.
PRs S-waiting-on-team
- Other issues in progress or waiting on other teams
Issues of Note
Short Summary
- 0 T-compiler P-critical issues
- 60 T-compiler P-high issues
- 0 P-critical, 1 P-high, 3 P-medium, 0 P-low regression-from-stable-to-beta
- 0 P-critical, 0 P-high, 2 P-medium, 2 P-low regression-from-stable-to-nightly
- 0 P-critical, 41 P-high, 100 P-medium, 18 P-low regression-from-stable-to-stable
P-critical
- No
P-criticalissues forT-compilerthis time.
- No
P-criticalissues forT-typesthis time.
P-high regressions
- “🐛 Symbol multiply defined since nightly-2023-12-02 with custom builtins.” rust#118609
Unassigned P-high nightly regressions
- No unassigned
P-highnightly regressions this time.
Performance logs
Overall, this week had very few regressions and a moderate amount of improvements. The two biggest improvements came in how metadata was being encoded including a change to only store StableCrateId once in DefPathTable which yielded a 0.3% average improvement across 79 different benchmarks.
Triage done by @rylev. Revision range: 1ab783112..67b6975
Summary:
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | 0.7% | [0.3%, 1.5%] | 8 |
| Regressions (secondary) | 0.8% | [0.2%, 1.3%] | 23 |
| Improvements (primary) | -0.6% | [-2.6%, -0.2%] | 121 |
| Improvements (secondary) | -5.2% | [-62.5%, -0.2%] | 53 |
| All (primary) | -0.5% | [-2.6%, 1.5%] | 129 |
2 Regressions, 3 Improvements, 1 Mixed; 0 of them in rollups 46 artifact comparisons made in total
Regressions
Emit better suggestions for &T == T and T == &T #118431 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | 24.0% | [18.1%, 29.5%] | 3 |
| Regressions (secondary) | - | - | 0 |
| Improvements (primary) | - | - | 0 |
| Improvements (secondary) | - | - | 0 |
| All (primary) | 24.0% | [18.1%, 29.5%] | 3 |
- Blip in the perf infrastructure that was reversed in the next run
rustc_lint: Enforce rustc::potential_query_instability lint #119251 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | 0.2% | [0.2%, 0.3%] | 2 |
| Regressions (secondary) | 0.3% | [0.2%, 0.4%] | 8 |
| Improvements (primary) | - | - | 0 |
| Improvements (secondary) | - | - | 0 |
| All (primary) | 0.2% | [0.2%, 0.3%] | 2 |
- Small regression that might just be worth it. There is discussion in #119488 on whether to do a partial revert, but so far the argument is being made to just accept the small regression.
Improvements
Suggest = to == in more cases, even in the face of reference mismatch #119328 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | - | - | 0 |
| Regressions (secondary) | - | - | 0 |
| Improvements (primary) | -19.2% | [-22.7%, -15.3%] | 3 |
| Improvements (secondary) | - | - | 0 |
| All (primary) | -19.2% | [-22.7%, -15.3%] | 3 |
- Reversal of perf infrastructure blip in previous run
Only store StableCrateId once in DefPathTable. #119259 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | 0.8% | [0.8%, 0.8%] | 1 |
| Regressions (secondary) | - | - | 0 |
| Improvements (primary) | -0.3% | [-0.6%, -0.2%] | 78 |
| Improvements (secondary) | -0.4% | [-0.6%, -0.3%] | 16 |
| All (primary) | -0.3% | [-0.6%, 0.8%] | 79 |
Shrink span encoding further #119367 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | - | - | 0 |
| Regressions (secondary) | - | - | 0 |
| Improvements (primary) | -0.3% | [-0.5%, -0.2%] | 27 |
| Improvements (secondary) | -0.5% | [-0.6%, -0.3%] | 11 |
| All (primary) | -0.3% | [-0.5%, -0.2%] | 27 |
Mixed
Implement constant propagation on top of MIR SSA analysis #116012 (Comparison Link)
| (instructions:u) | mean | range | count |
|---|---|---|---|
| Regressions (primary) | 0.7% | [0.2%, 1.9%] | 10 |
| Regressions (secondary) | 0.6% | [0.2%, 1.1%] | 15 |
| Improvements (primary) | -0.6% | [-2.6%, -0.2%] | 26 |
| Improvements (secondary) | -31.2% | [-62.1%, -0.2%] | 8 |
| All (primary) | -0.2% | [-2.6%, 1.9%] | 36 |
- Change has positive impacts on runtime performance and the improvements outweigh the regressions
Nominated Issues
- No I-compiler-nominated issues this time.
- No I-compiler-nominated RFCs this time.
Oldest PRs waiting for review
None this week
Next week’s WG checkins
TODO
Next meetings' agenda draft: hackmd link