Streamline CrateMetadataRef construction in provide_one!.

[nnethercote]

cstore.get_crate_data() creates a CrateMetadataRef, which is exactly what we need. The current code is very confused and does several unnecessary things: mapping the FreezeReadGuard and calling CStore::from_tcx a second time to construct a second CrateMetadataRef.

This is a small perf win.

r? @mu001999

[nnethercote]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 58e1a01 (58e1a01ba68db8f3f8e788e25c2fa9a2b69e480e, parent: 9ec5d5f32e19d250c7fbeaa90978c79105b39dee)

[rust-timer]

Finished benchmarking commit (58e1a01): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@bors rollup=never
@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-1.2%, -0.3%]	14
Improvements ✅ (secondary)	-0.7%	[-1.3%, -0.2%]	28
All ❌✅ (primary)	-0.5%	[-1.2%, -0.3%]	14

Max RSS (memory usage)

Results (primary 2.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Cycles

Results (secondary -9.7%)

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)	4.5%	[4.5%, 4.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-12.6%	[-18.7%, -3.5%]	5
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 489.594s -> 490.743s (0.23%)
Artifact size: 394.45 MiB -> 394.43 MiB (-0.01%)

[nnethercote]

Perf results show small but clear perf wins, mostly for doc builds.

[mu001999]

Cool! @bors r+

[rust-bors]

📌 Commit cb3df68 has been approved by mu001999

It is now in the queue for this repository.

[bjorn3]

r? @bjorn3

@bors r+

[rust-bors]

📌 Commit cb3df68 has been approved by bjorn3

It is now in the queue for this repository.

[bjorn3]

Somehow I didn't see your approval at all mu001999. Let me give credit back to you.

@bors r=mu001999

[rust-bors]

📌 Commit cb3df68 has been approved by mu001999

It is now in the queue for this repository.

[nnethercote]

Three approvals so far! It's a popular PR 😄