Only compute recursive callees once. #142625

cjgillot · 2025-06-17T13:53:47Z

Inlining MIR in a cyclic call graph may create query cycles, which are ICEs. The current implementation mir_callgraph_reachable(inlining_candidate, being_optimized) checks if calling inlining_candidate may cycle back to being_optimized that we are currently inlining into.

This PR replaces this device with query mir_callgraph_cyclic(being_optimized) which searches the call graph for all cycles going back to being_optimized, and returns the set of functions involved in those cycles.

This is a tradeoff:

in the current implementation, we perform more walks, but shallower;
in this new implementation, we perform fewer walks, but exhaust the graph.

I'd have liked to compute this using some kind of SCC, but generic parameters make resolution path-dependent, so usual graph algorithms do not apply.

cjgillot · 2025-06-17T13:54:39Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-17T13:54:43Z

⌛ Trying commit cdc8ada with merge 3f9dff5…

To cancel the try build, run the command @bors2 try cancel.

Only compute recursive callees once. r? `@ghost`

rust-bors · 2025-06-17T16:22:52Z

☀️ Try build successful (CI)
Build commit: 3f9dff5 (3f9dff597570d85408b02e981414f2d9e3b31e2c, parent: 55d436467c351b56253deeba209ae2553d1c243f)

rust-timer · 2025-06-18T07:43:40Z

Finished benchmarking commit (3f9dff5): comparison URL.

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

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.4%	[0.3%, 0.7%]	3
Regressions ❌ (secondary)	0.3%	[0.3%, 0.4%]	2
Improvements ✅ (primary)	-1.4%	[-2.5%, -0.2%]	2
Improvements ✅ (secondary)	-0.8%	[-0.8%, -0.8%]	1
All ❌✅ (primary)	-0.3%	[-2.5%, 0.7%]	5

Max RSS (memory usage)

Results (primary 2.4%, secondary 2.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.4%	[2.4%, 2.4%]	1
Regressions ❌ (secondary)	2.9%	[2.9%, 2.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.4%	[2.4%, 2.4%]	1

Cycles

Results (primary 0.7%, secondary 5.2%)

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)	5.2%	[3.2%, 6.5%]	6
Improvements ✅ (primary)	-1.2%	[-1.2%, -1.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[-1.2%, 2.7%]	2

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%, 0.0%]	1
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	1

Bootstrap: 756.784s -> 694.525s (-8.23%)
Artifact size: 372.10 MiB -> 372.08 MiB (-0.00%)

cjgillot · 2025-06-18T11:39:11Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-18T11:39:15Z

⌛ Trying commit ff30243 with merge 7ff0e48…

To cancel the try build, run the command @bors2 try cancel.

Only compute recursive callees once. r? `@ghost`

rust-bors · 2025-06-18T11:56:44Z

💔 Test failed

CI ❌

cjgillot · 2025-06-18T12:35:18Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-18T12:35:22Z

⌛ Trying commit 85f8013 with merge 4a6d273…

To cancel the try build, run the command @bors2 try cancel.

Only compute recursive callees once. r? `@ghost`

rust-bors · 2025-06-18T15:08:21Z

☀️ Try build successful (CI)
Build commit: 4a6d273 (4a6d273a303167376359d3352604c36356b5253f, parent: 6f935a044d1ddeb6160494a6320d008d7c311aef)

rust-timer · 2025-06-18T21:55:37Z

Finished benchmarking commit (4a6d273): comparison URL.

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

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.4%	[0.3%, 0.6%]	3
Regressions ❌ (secondary)	0.3%	[0.3%, 0.4%]	2
Improvements ✅ (primary)	-1.3%	[-2.5%, -0.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-2.5%, 0.6%]	5

Max RSS (memory usage)

Results (primary 1.3%, 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)	1.3%	[1.3%, 1.3%]	1
Regressions ❌ (secondary)	2.8%	[1.3%, 4.3%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.3%	[1.3%, 1.3%]	1

Cycles

Results (primary -1.7%, 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)	-	-	0
Improvements ✅ (primary)	-1.7%	[-1.7%, -1.7%]	1
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-1.7%	[-1.7%, -1.7%]	1

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%, 0.0%]	1
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	1

Bootstrap: 693.627s -> 698.902s (0.76%)
Artifact size: 371.96 MiB -> 371.90 MiB (-0.02%)

cjgillot · 2025-06-23T08:47:51Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-23T08:47:54Z

⌛ Trying commit 2074013 with merge d01b453…

To cancel the try build, run the command @bors2 try cancel.

Only compute recursive callees once. r? `@ghost`

rust-bors · 2025-06-23T11:16:17Z

☀️ Try build successful (CI)
Build commit: d01b453 (d01b453f1a08967fc96d120e059c1a94c977941c, parent: 58d5e1169056f31553ecf680b009a5770eb0e859)

rust-timer · 2025-06-23T13:38:34Z

Finished benchmarking commit (d01b453): comparison URL.

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

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.4%	[0.3%, 0.5%]	3
Regressions ❌ (secondary)	0.3%	[0.3%, 0.4%]	2
Improvements ✅ (primary)	-1.0%	[-2.5%, -0.2%]	3
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-0.3%	[-2.5%, 0.5%]	6

Max RSS (memory usage)

Results (secondary 2.6%)

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)	2.6%	[2.3%, 2.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -1.6%, 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)	-1.6%	[-1.6%, -1.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.6%	[-1.6%, -1.6%]	1

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%, 0.0%]	1
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	1

Bootstrap: 688.673s -> 694.013s (0.78%)
Artifact size: 371.94 MiB -> 371.91 MiB (-0.01%)

rustbot · 2025-06-23T14:14:34Z

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

rustbot · 2025-06-23T14:14:36Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

petrochenkov · 2025-06-23T14:42:47Z

r? mir

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jun 17, 2025

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 18, 2025

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cjgillot force-pushed the inline-nocycle branch from ff30243 to 85f8013 Compare June 18, 2025 12:04

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cjgillot added 3 commits June 22, 2025 20:08

Only compute recursive callees once.

09aab29

Cache queries.

8a35c7a

Only store the LocalDefId instead of the whole instance.

2074013

cjgillot force-pushed the inline-nocycle branch from 85f8013 to 2074013 Compare June 23, 2025 08:47

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 23, 2025

cjgillot marked this pull request as ready for review June 23, 2025 14:14

rustbot assigned petrochenkov Jun 23, 2025

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 23, 2025

cjgillot added the A-mir-opt Area: MIR optimizations label Jun 23, 2025

rustbot assigned matthewjasper and unassigned petrochenkov Jun 23, 2025

Only compute recursive callees once. #142625

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Only compute recursive callees once. #142625

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

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