[perf] defer the unconditional output resolution

[Randl]

Saw a ~twofold speedup locally for https://github.com/rust-lang/rust/blob/main/tests/ui/try-trait/deep-try-chain-issue-153583.rs
Probably minor for general use cases, but seems free?

[rustbot]

r? @petrochenkov

rustbot has assigned @petrochenkov.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler
• compiler expanded to 75 candidates
• Random selection from 17 candidates

[Kobzol]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 13954f7 (13954f77cd08a51e4639eabf7bf5b2e10b2bbcb3)
Base parent: c47bb2f (c47bb2f39658c00b109693df9611d7238bedf6fa)

[rust-timer]

Finished benchmarking commit (13954f7): 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 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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-1.5%, -0.2%]	13
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (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)	-	-	0
Regressions ❌ (secondary)	0.9%	[0.9%, 0.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.4%, -0.4%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -0.3%, 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)	0.6%	[0.4%, 0.7%]	3
Regressions ❌ (secondary)	0.9%	[0.4%, 1.2%]	3
Improvements ✅ (primary)	-0.7%	[-1.2%, -0.4%]	6
Improvements ✅ (secondary)	-0.7%	[-1.7%, -0.4%]	7
All ❌✅ (primary)	-0.3%	[-1.2%, 0.7%]	9

Binary size

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

Bootstrap: 490.834s -> 491.917s (0.22%)
Artifact size: 390.52 MiB -> 390.51 MiB (-0.00%)

[petrochenkov]

Nice.
@bors r+

[rust-bors]

📌 Commit a4a0f29 has been approved by petrochenkov

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: petrochenkov
Duration: 3h 12m 47s
Pushing b04d3c8 to main...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 8c3a200 (parent) -> b04d3c8 (this PR)

Test differences

Show 2 test diffs

2 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard b04d3c8c22822b7f10dab5a563b4e2afff1861c1 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. x86_64-gnu-gcc-core-tests: 17m 13s -> 8m 32s (-50.4%)
2. dist-x86_64-apple: 4h 50m -> 2h 24m (-50.3%)
3. x86_64-gnu-next-trait-solver-polonius: 39m 47s -> 57m 40s (+45.0%)
4. optional-x86_64-gnu-autodiff: 52m 12s -> 35m 45s (-31.5%)
5. dist-arm-linux-gnueabi: 1h 9m -> 1h 30m (+30.0%)
6. pr-check-2: 39m 16s -> 28m 55s (-26.4%)
7. dist-x86_64-msvc: 1h 45m -> 2h 11m (+24.8%)
8. i686-msvc-1: 2h 56m -> 2h 14m (-23.9%)
9. dist-powerpc64-linux-musl: 1h 37m -> 1h 14m (-23.7%)
10. dist-loongarch64-musl: 1h 29m -> 1h 51m (+23.6%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (b04d3c8): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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
Improvements ✅ (secondary)	-0.6%	[-1.5%, -0.2%]	12
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -0.7%, 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)	0.5%	[0.5%, 0.5%]	1
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-1.7%	[-6.1%, -0.4%]	5
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	1

Cycles

Results (primary 0.9%, secondary 1.6%)

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

	mean	range	count
Regressions ❌ (primary)	1.3%	[0.5%, 2.8%]	11
Regressions ❌ (secondary)	2.7%	[0.4%, 15.4%]	15
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	3
Improvements ✅ (secondary)	-2.3%	[-4.0%, -0.7%]	4
All ❌✅ (primary)	0.9%	[-0.7%, 2.8%]	14

Binary size

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

Bootstrap: 488.148s -> 491.057s (0.60%)
Artifact size: 390.38 MiB -> 390.41 MiB (0.01%)