Make the inliner recursion depth hack stronger

[saethlin]

We previously tried to introduce a more gentle version of this hack in github.com//pull/129714, but that wasn't enough because the problem was re-reported in #131960 (comment). So this increases the magic number from 2 to 8. Surely nobody will complain that they have a type whose depth grows more than 8 times faster than its call graph depth.

[saethlin]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 84baca6 (84baca666cf52534bd50188bd7c20b504018eace, parent: 5b9007bfc358817cf066ee27c6b440440727d3a7)

[rust-timer]

Finished benchmarking commit (84baca6): 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
Regressions ❌ (secondary)	0.4%	[0.1%, 1.1%]	7
Improvements ✅ (primary)	-1.2%	[-1.3%, -1.1%]	2
Improvements ✅ (secondary)	-0.5%	[-1.4%, -0.1%]	10
All ❌✅ (primary)	-1.2%	[-1.3%, -1.1%]	2

Max RSS (memory usage)

Results (primary -3.5%, secondary 3.9%)

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)	3.9%	[1.0%, 5.4%]	12
Improvements ✅ (primary)	-3.5%	[-5.4%, -2.3%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.5%	[-5.4%, -2.3%]	3

Cycles

Results (primary -4.2%, secondary -4.8%)

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)	3.4%	[2.3%, 4.1%]	3
Improvements ✅ (primary)	-4.2%	[-10.3%, -2.1%]	22
Improvements ✅ (secondary)	-5.7%	[-19.9%, -1.0%]	26
All ❌✅ (primary)	-4.2%	[-10.3%, -2.1%]	22

Binary size

Results (primary 0.2%, 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)	0.3%	[0.0%, 1.5%]	5
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	37
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	2
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	1
All ❌✅ (primary)	0.2%	[-0.1%, 1.5%]	7

Bootstrap: 478.827s -> 470.051s (-1.83%)
Artifact size: 388.10 MiB -> 388.49 MiB (0.10%)

[Kobzol]

(the cycle changes and bootstrap time are noise returning to normal).

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

[rustbot]

r? @petrochenkov

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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

[petrochenkov]

So this increases the magic number from 2 to 8

4 wasn't enough to fix the crash? :D

[petrochenkov]

@bors r+

[bors]

📌 Commit 9e379ff has been approved by petrochenkov

It is now in the queue for this repository.

[bors]

⌛ Testing commit 9e379ff with merge 0ec7cf7...

[rust-log-analyzer]

The job x86_64-rust-for-linux failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

   Compiling log v0.4.28
error[E0391]: cycle detected when whether the item should be made inlinable across crates
##[error]    --> /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1508:5
     |
1508 |     fn eq(&self, other: &Self) -> bool {
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |
note: ...which requires optimizing MIR for `gen::eq::<impl at /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1507:1: 1507:35>::eq`...
    --> /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1508:5
     |
1508 |     fn eq(&self, other: &Self) -> bool {
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires whether the item should be made inlinable across crates...
    --> /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1473:5
     |
1473 |     fn eq(&self, other: &Self) -> bool {
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires optimizing MIR for `gen::eq::<impl at /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1472:1: 1472:30>::eq`...
    --> /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/syn-2.0.106/src/gen/eq.rs:1473:5
     |
1473 |     fn eq(&self, other: &Self) -> bool {
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     = note: ...which again requires whether the item should be made inlinable across crates, completing the cycle
     = note: cycle used when reachability
     = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

For more information about this error, try `rustc --explain E0391`.
error: could not compile `syn` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
error: failed to compile `bindgen-cli v0.65.1`, intermediate artifacts can be found at `/tmp/cargo-install1OgzOd`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.
  local time: Tue Sep 30 02:28:20 UTC 2025
  network time: Tue, 30 Sep 2025 02:28:20 GMT
****************************************************************************
To find more information about this job, visit the following URL:

For more information how to resolve CI failures of this job, visit this link.

[bors]

💔 Test failed - checks-actions

[saethlin]

That is hilarious