Don't fold in Instantiate when there's nothing to fold #142317

compiler-errors · 2025-06-10T21:49:08Z

Maybe this helps idk

r? lcnr

compiler-errors · 2025-06-10T21:49:14Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-10T21:49:18Z

⌛ Trying commit cbd67db with merge 4b9e637…

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

Don't fold in Instantiate when there's nothing to fold Maybe this helps idk r? lcnr

compiler-errors · 2025-06-10T22:12:13Z

i feel like ive tested this before lol

rust-bors · 2025-06-11T00:18:08Z

☀️ Try build successful (CI)
Build commit: 4b9e637 (4b9e63748fe7159cca76930c0864086580bb664a)

rust-timer · 2025-06-12T00:37:13Z

Finished benchmarking commit (4b9e637): 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)	0.3%	[0.1%, 0.5%]	2
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	4
Improvements ✅ (secondary)	-1.7%	[-3.4%, -0.1%]	12
All ❌✅ (primary)	-0.0%	[-0.3%, 0.5%]	6

Max RSS (memory usage)

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

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)	3.7%	[3.6%, 3.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.2%	[-1.2%, -1.2%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 755.415s -> 754.049s (-0.18%)
Artifact size: 372.14 MiB -> 372.20 MiB (0.02%)

compiler-errors · 2025-06-12T01:13:28Z

I think the perf wins outweigh the perf hits.

@rustbot ready

compiler-errors · 2025-06-12T01:18:22Z

compiler/rustc_type_ir/src/binder.rs

@@ -622,6 +622,10 @@ impl<I: Interner, T: TypeFoldable<I>> ty::EarlyBinder<I, T> {
    where
        A: SliceLike<Item = I::GenericArg>,
    {
+        // Nothing to fold.
+        if !cfg!(debug_assertions) && args.is_empty() {


We still fold if cfg!(debug_assertions) since the arg folder can detect out of bound arg instantiations, and that's useful in debug builds.

I believe that this is morally a debug assertion, since we never expect it in practice.

instead of still folding with debug assertions, check whether the value has params.

r=me after this nit

compiler-errors · 2025-06-13T19:03:37Z

@bors r=lcnr

bors · 2025-06-13T19:03:40Z

📌 Commit 2b52d65 has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-06-14T22:41:53Z

⌛ Testing commit 2b52d65 with merge 696433c...

Don't fold in Instantiate when there's nothing to fold Maybe this helps idk r? lcnr

bors · 2025-06-14T23:20:08Z

💔 Test failed - checks-actions

compiler-errors · 2025-06-26T00:08:47Z

@bors r=lcnr

I ended up turning the debug_assert into an assert since this "fixes" a bunch of crashes that I think we should continue to let ICE.

bors · 2025-06-26T00:08:50Z

📌 Commit d032119 has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-06-28T13:31:15Z

⌛ Testing commit d032119 with merge 7ba34c7...

bors · 2025-06-28T16:31:33Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 7ba34c7 to master...

github-actions · 2025-06-28T16:34:35Z

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 b63223c (parent) -> 7ba34c7 (this PR)

Test differences

Show 8 test diffs

8 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 7ba34c704529e7fcab80130c3fe40efe415d61b5 --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

x86_64-apple-2: 3249.6s -> 4664.6s (43.5%)
x86_64-rust-for-linux: 2529.2s -> 2989.7s (18.2%)
aarch64-gnu-debug: 3563.2s -> 4194.6s (17.7%)
i686-gnu-2: 5375.5s -> 6244.2s (16.2%)
mingw-check-1: 1525.7s -> 1748.4s (14.6%)
dist-apple-various: 5667.8s -> 6431.7s (13.5%)
x86_64-apple-1: 8791.0s -> 7634.6s (-13.2%)
x86_64-gnu-llvm-20-1: 3222.4s -> 3638.0s (12.9%)
x86_64-gnu-tools: 3324.1s -> 3713.2s (11.7%)
armhf-gnu: 4395.3s -> 4875.5s (10.9%)

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 · 2025-06-28T17:56:36Z

Finished benchmarking commit (7ba34c7): 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)	0.2%	[0.1%, 0.3%]	9
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	3
Improvements ✅ (secondary)	-2.6%	[-2.9%, -2.4%]	6
All ❌✅ (primary)	0.1%	[-0.3%, 0.3%]	12

Max RSS (memory usage)

Results (secondary 4.7%)

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)	4.7%	[4.7%, 4.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -3.2%)

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)	-3.2%	[-3.3%, -3.1%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 690.587s -> 689.948s (-0.09%)
Artifact size: 372.13 MiB -> 371.76 MiB (-0.10%)

rustbot assigned lcnr Jun 10, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 10, 2025

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rust-bors bot added a commit that referenced this pull request Jun 10, 2025

Auto merge of #142317 - compiler-errors:perf-fold, r=<try>

4b9e637

Don't fold in Instantiate when there's nothing to fold Maybe this helps idk r? lcnr

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 10, 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 12, 2025

compiler-errors commented Jun 12, 2025

View reviewed changes

compiler-errors force-pushed the perf-fold branch from cbd67db to 2b52d65 Compare June 13, 2025 18:02

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 Jun 13, 2025

bors added a commit that referenced this pull request Jun 14, 2025

Auto merge of #142317 - compiler-errors:perf-fold, r=lcnr

696433c

Don't fold in Instantiate when there's nothing to fold Maybe this helps idk r? lcnr

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bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 14, 2025

Don't fold in Instantiate when there's nothing to fold

d032119

compiler-errors force-pushed the perf-fold branch from 2b52d65 to d032119 Compare June 25, 2025 15:46

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 Jun 26, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Jun 28, 2025

bors merged commit 7ba34c7 into rust-lang:master Jun 28, 2025
11 checks passed

rustbot added this to the 1.90.0 milestone Jun 28, 2025

Don't fold in Instantiate when there's nothing to fold #142317

Don't fold in Instantiate when there's nothing to fold #142317

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rust-timer commented Jun 12, 2025

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

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compiler-errors commented Jun 13, 2025

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github-actions bot commented Jun 28, 2025

Test differences

Job duration changes

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rust-timer commented Jun 28, 2025

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

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compiler-errors commented Jun 26, 2025 •

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