2024-06-18 Triage Log

Regressions outnumbered the improvements this week, but most of the regressions were deemed worth it for one reason or another. Overall, compiler performance didn't end up changing very much.

Triage done by @rylev. Revision range: b5b13568..c2932aaf

Summary:

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.4%[0.2%, 1.0%]63
Regressions ❌
(secondary)		0.7%[0.2%, 2.4%]70
Improvements ✅
(primary)		-0.6%[-1.2%, -0.2%]8
Improvements ✅
(secondary)		-1.1%[-5.2%, -0.2%]7
All ❌✅ (primary)0.3%[-1.2%, 1.0%]71

5 Regressions, 2 Improvements, 7 Mixed; 2 of them in rollups 58 artifact comparisons made in total

Regressions

Print token::Interpolated with token stream pretty printing. #125174 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.3%[0.2%, 0.4%]9
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.3%[0.2%, 0.4%]9
  • No discussion of the perf run done before merging, so I asked the author/reviewer for their thoughts.
  • It seems like most libc benchmarks were negatively impacted while no other benchmarks were. I'm not quite sure why that would be.

Add TyCtxt::is_lang_item, use it in the compiler #126491 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.3%[0.2%, 0.4%]10
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.3%[0.2%, 0.4%]10
  • The change was deemed worth it despite the perf regression.

Indicate in non_local_defs lint that the macro needs to change #125722 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.2%[0.2%, 0.2%]6
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.2%[0.2%, 0.2%]6
  • Only the diesel benchmark is affected, which is somewhat expected as it triggers the lint many many times (over 150 times).

Rollup of 6 pull requests #126605 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.3%[0.3%, 0.4%]6
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.3%[0.3%, 0.4%]6
  • The benchmarks impacted seem to now swing wildly back and forth with every run so this isn't a perf regression per say.

Migrate inaccessible-temp-dir, output-with-hyphens and issue-10971-temps-dir run-make tests to rmake #126279 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.3%[0.3%, 0.3%]6
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.3%[0.3%, 0.3%]6
  • This has to be noise, this PR only modified tests.

Improvements

Migrate link-arg, link-dedup and issue-26092 run-make tests to rmake format #125500 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		--0
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		-0.4%[-0.4%, -0.3%]6
Improvements ✅
(secondary)		--0
All ❌✅ (primary)-0.4%[-0.4%, -0.3%]6

Migrate extern-flag-fun, incremental-debugger-visualiser and incremental-session-fail run-make tests to rmake.rs #126490 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		--0
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		-0.3%[-0.4%, -0.3%]6
Improvements ✅
(secondary)		--0
All ❌✅ (primary)-0.3%[-0.4%, -0.3%]6

Mixed

Add SingleUseConsts mir-opt pass #125910 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.4%[0.3%, 0.4%]2
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		-0.3%[-0.4%, -0.2%]4
Improvements ✅
(secondary)		-2.3%[-2.9%, -1.7%]2
All ❌✅ (primary)-0.1%[-0.4%, 0.4%]6
  • Wash on instruction counts, but nice binary size wins. The cycles improvements on tt-muncher is noise returning back to normal.

Make ObligationEmittingRelations emit Goal rather than Obligation #126130 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		--0
Regressions ❌
(secondary)		0.4%[0.1%, 0.6%]14
Improvements ✅
(primary)		-0.2%[-0.2%, -0.2%]1
Improvements ✅
(secondary)		--0
All ❌✅ (primary)-0.2%[-0.2%, -0.2%]1
  • I'm asssuming the perf regression was deemed acceptable since these only occurred in stress tests?

Tait must be constrained if in sig #113169 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.7%[0.7%, 0.7%]1
Regressions ❌
(secondary)		--0
Improvements ✅
(primary)		-0.3%[-0.4%, -0.3%]2
Improvements ✅
(secondary)		--0
All ❌✅ (primary)-0.0%[-0.4%, 0.7%]3
  • Probably noise + we need the fix

Extend SCC construction to enable extra functionality #125069 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.2%[0.2%, 0.3%]6
Regressions ❌
(secondary)		0.5%[0.1%, 1.0%]10
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		-0.3%[-0.3%, -0.3%]2
All ❌✅ (primary)0.2%[0.2%, 0.3%]6
  • The perf regressions were brought down since the first perf run, but there's still instruction count regressions in primary benchmarks here (albeit not large ones). I asked the author/reviewer for thoughts.

Remove superfluous UbChecks from SliceIndex methods #126299 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.4%[0.2%, 0.6%]4
Regressions ❌
(secondary)		0.8%[0.5%, 1.3%]5
Improvements ✅
(primary)		-0.4%[-0.6%, -0.2%]3
Improvements ✅
(secondary)		-0.6%[-0.8%, -0.4%]7
All ❌✅ (primary)0.1%[-0.6%, 0.6%]7
  • Perf is largely a wash and was expected to have far reach consequences since it changes how slices are codegened.

rustc_span: Optimize more hygiene operations using Span::map_ctxt #126543 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		0.2%[0.2%, 0.2%]1
Regressions ❌
(secondary)		0.3%[0.2%, 0.4%]3
Improvements ✅
(primary)		-1.1%[-1.4%, -0.3%]4
Improvements ✅
(secondary)		-0.3%[-0.3%, -0.2%]3
All ❌✅ (primary)-0.8%[-1.4%, 0.2%]5
  • Improvements outweigh the regressions which all seemed to be reversed sometime soon after this landed.

Rollup of 3 pull requests #126581 (Comparison Link)

(instructions:u)meanrangecount
Regressions ❌
(primary)		--0
Regressions ❌
(secondary)		1.3%[1.3%, 1.3%]1
Improvements ✅
(primary)		-0.3%[-0.4%, -0.2%]6
Improvements ✅
(secondary)		--0
All ❌✅ (primary)-0.3%[-0.4%, -0.2%]6
  • Regression might be noise (and isn‘t big enough to care about even if it isn’t)