Only traverse reachable blocks in JumpThreading.

[cjgillot]

Fixes #131451

We only compute loop headers for reachable blocks. We shouldn't try to perform an opt on unreachable blocks anyway.

[rustbot]

r? @fee1-dead

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Use r? to explicitly pick a reviewer

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[compiler-errors]

@bors try @rust-timer queue

r=me after perf

[bors]

⌛ Trying commit 89b079d with merge c07ba10...

[bors]

☀️ Try build successful - checks-actions
Build commit: c07ba10 (c07ba10880fe4ac22aea41eae091bfd8a66e66dc)

[rust-timer]

Finished benchmarking commit (c07ba10): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in 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)	0.6%	[0.6%, 0.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[0.6%, 0.6%]	1

Max RSS (memory usage)

Results (primary 0.2%, secondary 4.3%)

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

	mean	range	count
Regressions ❌ (primary)	3.3%	[2.4%, 4.8%]	4
Regressions ❌ (secondary)	4.3%	[4.3%, 4.3%]	1
Improvements ✅ (primary)	-3.0%	[-3.6%, -2.2%]	4
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[-3.6%, 4.8%]	8

Cycles

Results (secondary -2.2%)

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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	2
All ❌✅ (primary)	-	-	0

Binary size

Results (primary 0.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.1%]	2
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[-0.0%, 0.1%]	3

Bootstrap: 755.712s -> 756.317s (0.08%)
Artifact size: 372.06 MiB -> 372.12 MiB (0.02%)

[compiler-errors]

@bors r+

[bors]

📌 Commit 89b079d has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit 89b079d with merge d4e1159...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing d4e1159 to master...

[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 ea34650 (parent) -> d4e1159 (this PR)

Test differences

Show 6 test diffs

Stage 1

• [crashes] tests/crashes/131451.rs: pass -> [missing] (J0)
• [ui] tests/ui/mir/unreachable-loop-jump-threading.rs: [missing] -> pass (J0)

Stage 2

• [crashes] tests/crashes/131451.rs: ignore (ignored if rustc wasn't built with debug assertions) -> [missing] (J1)
• [crashes] tests/crashes/131451.rs: pass -> [missing] (J2)
• [ui] tests/ui/mir/unreachable-loop-jump-threading.rs: [missing] -> pass (J2)
• [ui] tests/ui/mir/unreachable-loop-jump-threading.rs: [missing] -> ignore (ignored if rustc wasn't built with debug assertions) (J3)

Job group index

• J0: x86_64-gnu-llvm-19-3, x86_64-gnu-llvm-20-3
• J1: aarch64-apple, dist-i586-gnu-i586-i686-musl, test-various, x86_64-apple-1
• J2: aarch64-gnu, arm-android, armhf-gnu, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, x86_64-gnu, x86_64-gnu-llvm-19-2, x86_64-gnu-llvm-20-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
• J3: aarch64-apple, dist-i586-gnu-i586-i686-musl, test-various, x86_64-apple-2

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard d4e1159b8c97478778b09a4cc1c7adce5653b8bf --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. dist-x86_64-apple: 8947.3s -> 7078.8s (-20.9%)
2. x86_64-rust-for-linux: 2953.4s -> 2500.5s (-15.3%)
3. x86_64-gnu-tools: 3747.8s -> 3253.4s (-13.2%)
4. i686-gnu-1: 8090.1s -> 7180.3s (-11.2%)
5. mingw-check-1: 1727.4s -> 1544.6s (-10.6%)
6. x86_64-gnu-llvm-19-1: 3722.6s -> 3335.6s (-10.4%)
7. i686-gnu-nopt-1: 7949.7s -> 7151.4s (-10.0%)
8. dist-ohos-armv7: 4358.4s -> 3938.5s (-9.6%)
9. dist-powerpc-linux: 5264.7s -> 4774.8s (-9.3%)
10. x86_64-gnu-debug: 5911.3s -> 5380.9s (-9.0%)

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 (d4e1159): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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)	1.6%	[0.3%, 2.9%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	2
All ❌✅ (primary)	1.6%	[0.3%, 2.9%]	2

Max RSS (memory usage)

Results (primary -1.8%, secondary -3.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.0%, 2.5%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.5%	[-6.0%, -3.7%]	3
Improvements ✅ (secondary)	-3.6%	[-3.6%, -3.6%]	1
All ❌✅ (primary)	-1.8%	[-6.0%, 2.5%]	5

Cycles

Results (primary 3.0%, secondary 2.8%)

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

	mean	range	count
Regressions ❌ (primary)	3.0%	[3.0%, 3.0%]	1
Regressions ❌ (secondary)	2.8%	[2.8%, 2.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.0%	[3.0%, 3.0%]	1

Binary size

Results (primary 0.3%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.1%, 1.1%]	5
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	1
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	0.3%	[-0.2%, 1.1%]	6

Bootstrap: 691.091s -> 691.957s (0.13%)
Artifact size: 371.86 MiB -> 371.85 MiB (-0.00%)