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).
  • No meetings scheduled for next week

MCPs/FCPs

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-compiler this time.

T-types stable / T-types beta

  • No beta nominations for T-types this time.
  • No stable nominations for T-types this time.

PRs S-waiting-on-team

T-compiler

Issues of Note

Short Summary

P-critical

T-compiler

  • No P-critical issues for T-compiler this time.

T-types

  • No P-critical issues for T-types this time.

P-high regressions

P-high beta regressions

  • "🐛 Symbol multiply defined since nightly-2023-12-02 with custom builtins." rust#118609

Unassigned P-high nightly regressions

  • No unassigned P-high nightly regressions this time.

Performance logs

triage logs for 2024-01-02

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

T-compiler

  • No I-compiler-nominated issues this time.

RFC

  • 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

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