Refactor remove_noop_landing_pads in two loops.#147099

cjgillot · 2025-09-27T16:48:17Z

The point is to avoid clearing the CFG cache as often.

r? @ghost for perf

cjgillot · 2025-09-27T18:45:40Z

Refactor remove_noop_landing_pads in two loops.

rust-bors · 2025-09-27T21:00:14Z

☀️ Try build successful (CI)
Build commit: 5213325 (5213325055e9098e603acc425fb95c1d0f350769, parent: ade84871f718ea20a6460d28e82290353b4bf3d2)

rust-timer · 2025-09-27T22:10:29Z

Finished benchmarking commit (5213325): comparison URL.

Overall result: ✅ improvements - 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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -1.1%)

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)	0.7%	[0.7%, 0.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-3.0%, -3.0%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 2.1%)

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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 469.268s -> 471.818s (0.54%)
Artifact size: 388.12 MiB -> 388.15 MiB (0.01%)

rustbot · 2025-09-28T04:45:49Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

cjgillot · 2025-09-28T04:46:11Z

r? compiler

lcnr · 2025-09-30T09:16:15Z

compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs

+
+        // This is a post-order traversal, so that if A post-dominates B
+        // then A will be visited before B.
+        for &bb in body.basic_blocks.reverse_postorder().iter().rev() {


why body.basic_blocks.reverse_postorder().iter().rev() instead** of traversal::postorder(body)?

r=me otherwise

94b2c30 uses traversal::postorder, which simplifies some things too.

rustbot · 2025-10-04T17:03:38Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

lcnr · 2025-10-06T13:36:37Z

@bors r+

bors · 2025-10-06T13:36:41Z

📌 Commit 94b2c30 has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-10-07T03:31:30Z

⌛ Testing commit 94b2c30 with merge d773bd0...

bors · 2025-10-07T06:41:04Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing d773bd0 to master...

github-actions · 2025-10-07T06:44:25Z

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 ff5be13 (parent) -> d773bd0 (this PR)

Test differences

No test diffs found

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard d773bd07d63a74adcf25ea5f4aae986be94cac5e --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

aarch64-apple: 9667.0s -> 6935.4s (-28.3%)
dist-x86_64-apple: 8503.2s -> 6142.2s (-27.8%)
x86_64-rust-for-linux: 3106.3s -> 2618.6s (-15.7%)
i686-gnu-2: 6426.8s -> 5441.2s (-15.3%)
x86_64-gnu-llvm-20: 2731.0s -> 2360.8s (-13.6%)
dist-x86_64-msvc-alt: 9571.9s -> 10835.9s (13.2%)
i686-gnu-nopt-1: 8186.1s -> 7179.9s (-12.3%)
arm-android: 6418.5s -> 5878.8s (-8.4%)
aarch64-gnu-llvm-20-2: 2405.9s -> 2217.6s (-7.8%)
aarch64-gnu-debug: 4225.7s -> 3908.5s (-7.5%)

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 · 2025-10-07T07:59:50Z

Finished benchmarking commit (d773bd0): 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)	-0.4%	[-0.6%, -0.1%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -0.1%)

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)	1.0%	[1.0%, 1.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-2.8%, -2.8%]	1
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 473.87s -> 473.455s (-0.09%)
Artifact size: 388.40 MiB -> 388.39 MiB (-0.00%)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 27, 2025

cjgillot force-pushed the split-nop-landing branch from 35adce2 to 9bb173f Compare September 27, 2025 16:48

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rust-bors bot added a commit that referenced this pull request Sep 27, 2025

Auto merge of #147099 - cjgillot:split-nop-landing, r=<try>

5213325

Refactor remove_noop_landing_pads in two loops.

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 27, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 27, 2025

cjgillot marked this pull request as ready for review September 28, 2025 04:45

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 28, 2025

rustbot assigned lcnr Sep 28, 2025

lcnr reviewed Sep 30, 2025

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lcnr added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 30, 2025

cjgillot added 3 commits October 4, 2025 16:59

Refactor remove_noop_landing_pads in two loops.

cf341ea

Create resume block later.

1ac5d4c

Use traversal::postorder.

94b2c30

cjgillot force-pushed the split-nop-landing branch from 9bb173f to 94b2c30 Compare October 4, 2025 17:03

cjgillot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 4, 2025

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 6, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 7, 2025

bors merged commit d773bd0 into rust-lang:master Oct 7, 2025
11 checks passed

rustbot added this to the 1.92.0 milestone Oct 7, 2025

cjgillot deleted the split-nop-landing branch October 7, 2025 10:15

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rust-timer commented Sep 27, 2025

Overall result: ✅ improvements - no action needed

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Test differences

Job duration changes

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rust-timer commented Oct 7, 2025

Overall result: ✅ improvements - no action needed

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