[perf] Reuse existing trait reference instead of recreating it.

[obi1kenobi]

Effectively, do one step of common subexpression elimination, manually. We can reuse the existing interned reference made a few lines prior, without needing to recreate it.

r? @lcnr

AI disclosure: The optimization opportunity here was discovered as part of a systematic probe for missed optimizations using a combination of both traditional and AI tools. The code here was initially prototyped and vetted by AI tools, followed by additional manual work. I stand behind the quality of the code I'm submitting, and I vouch it's as good or better than if no AI tools were in the loop.

[Zalathar]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 4a90c30 (4a90c30649a165543d68cdd23bfae7a76e5bd4a8)
Base parent: 1ed2df6 (1ed2df61a19042f231709eb05d032ae9e2cb2084)

[rust-timer]

Finished benchmarking commit (4a90c30): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.3%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.1%	[-7.5%, -0.1%]	10
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	4

Max RSS (memory usage)

Results (secondary -1.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-4.9%, -0.4%]	6
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 1.5%, secondary -0.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.6%, 2.7%]	6
Regressions ❌ (secondary)	1.5%	[0.5%, 3.8%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.5%	[-3.6%, -0.4%]	11
All ❌✅ (primary)	1.5%	[0.6%, 2.7%]	6

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.825s -> 491.303s (0.30%)
Artifact size: 391.14 MiB -> 391.36 MiB (0.06%)

[lcnr]

any reason this is still a draft? r=me after

[lcnr]

next-solver perf is absolutely wonderful, big fan

@bors r+ rollup=never

[rust-bors]

📌 Commit 8d8e996 has been approved by lcnr

It is now in the queue for this repository.