Split IncrCompSession out of Session by bjorn3 · Pull Request #159225 · rust-lang/rust

bjorn3 · 2026-07-13T13:52:37Z

This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session.

Based on #159000
Part of rust-lang/compiler-team#908

rustbot · 2026-07-13T13:52:41Z

rustc_codegen_gcc is developed in its own repository. If possible, consider making this change to rust-lang/rustc_codegen_gcc instead.

cc @antoyo, @GuillaumeGomez

rustbot · 2026-07-13T13:52:43Z

r? @jackh726

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bjorn3 · 2026-07-21T09:34:47Z

#159000 has landed.

@rustbot ready

This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session.

rustbot · 2026-07-23T10:19:29Z

This PR was rebased onto a different main 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.

bjorn3 · 2026-08-04T14:10:20Z

It's been a couple of weeks since this became ready for review.

r? compiler

oli-obk · 2026-08-05T07:06:04Z

 ) -> WorkProductMap {
    let mut work_products = WorkProductMap::default();

    if sess.opts.incremental.is_none() || sess.opts.unstable_opts.disable_incr_comp_backend_caching


kinda sucks that we have both incr_comp_session as an Option, and the flag that need to be in sync everywhere, and we're randomly checking one or the other. Tho I guess with the unwraps we are asserting that we're doing everything right

View changes since the review

oli-obk · 2026-08-05T07:09:11Z

@bors r+ rollup

rust-bors · 2026-08-05T07:09:14Z

📌 Commit f9679fa has been approved by oli-obk

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

Reason for tree closure: manually handling queue due to backlog

…oli-obk Split IncrCompSession out of Session This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session. Based on rust-lang#159000 Part of rust-lang/compiler-team#908

…uwer Rollup of 22 pull requests Successful merges: - #158147 (std: fix stack buffer overflow in Windows junction_point) - #159784 (Hint that memchr returns an in-bounds index) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

…oli-obk Split IncrCompSession out of Session This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session. Based on rust-lang#159000 Part of rust-lang/compiler-team#908

…uwer Rollup of 25 pull requests Successful merges: - #154585 (treat no_mangle_generic_items as hard error instead of lint warning) - #158147 (std: fix stack buffer overflow in Windows junction_point) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #158762 (Emit thumb code on VEX V5) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160516 (Add regression test for HRTB projection in closure) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160523 (Add regression test for opaque type) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

…uwer Rollup of 25 pull requests Successful merges: - #158147 (std: fix stack buffer overflow in Windows junction_point) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #158762 (Emit thumb code on VEX V5) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160501 (Add bootstrap CLI snapshot test for testing miri) - #160516 (Add regression test for HRTB projection in closure) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160523 (Add regression test for opaque type) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

Rollup merge of #159225 - bjorn3:split_incr_comp_session, r=oli-obk Split IncrCompSession out of Session This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session. Based on #159000 Part of rust-lang/compiler-team#908

JonathanBrouwer · 2026-08-06T20:15:20Z

@rust-timer build dc6c721

rust-timer · 2026-08-06T22:11:46Z

Finished benchmarking commit (dc6c721): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)	1.9%	[1.4%, 2.5%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.6%, -0.2%]	10
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 2.5%, secondary 25.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	25.0%	[1.2%, 30.9%]	13
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.5%	[2.5%, 2.5%]	1

Cycles

Results (primary 3.5%, secondary 12.6%)

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

	mean	range	count
Regressions ❌ (primary)	3.5%	[3.5%, 3.5%]	1
Regressions ❌ (secondary)	17.0%	[2.1%, 31.9%]	15
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-9.3%	[-14.4%, -3.3%]	3
All ❌✅ (primary)	3.5%	[3.5%, 3.5%]	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%]	21
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	21

Bootstrap: 454.551s -> 457.97s (0.75%)
Artifact size: 399.93 MiB -> 399.07 MiB (-0.22%)

rustbot assigned jackh726 Jul 13, 2026

bjorn3 marked this pull request as draft July 13, 2026 13:52

rustbot 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 Jul 13, 2026

bjorn3 added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Jul 13, 2026

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This was referenced Jul 14, 2026

Build a new incr comp session dir from scratch every time #159287

Open

Move LTO from the codegen coordinator thread to link_binary rust-lang/compiler-team#908

Closed

bjorn3 added the A-incr-comp Area: Incremental compilation label Jul 14, 2026

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bjorn3 force-pushed the split_incr_comp_session branch 2 times, most recently from da7be36 to 5b8856f Compare July 21, 2026 09:31

bjorn3 marked this pull request as ready for review July 21, 2026 09:34

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 Jul 21, 2026

bjorn3 removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Jul 21, 2026

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bjorn3 force-pushed the split_incr_comp_session branch from 5b8856f to b87b61a Compare July 21, 2026 09:58

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bjorn3 force-pushed the split_incr_comp_session branch from b87b61a to 20a013f Compare July 21, 2026 13:47

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Split IncrCompSession out of Session

f9679fa

This will allow introducing a separate incr comp session dir for the post LTO artifacts in the future. In addition it statically encodes the lifetime of the incr comp session rather than requiring an enum behind a mutex stored in the Session.

bjorn3 force-pushed the split_incr_comp_session branch from 20a013f to f9679fa Compare July 23, 2026 10:19

rustbot assigned oli-obk and unassigned jackh726 Aug 4, 2026

oli-obk reviewed Aug 5, 2026

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rust-bors Bot 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 Aug 5, 2026

jhpratt mentioned this pull request Aug 5, 2026

Rollup of 16 pull requests #160549

Closed

JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 22 pull requests #160554

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JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 25 pull requests #160557

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JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 25 pull requests #160559

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rust-bors Bot merged commit 900f0bc into rust-lang:main Aug 5, 2026
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rustbot added this to the 1.99.0 milestone Aug 5, 2026

bjorn3 deleted the split_incr_comp_session branch August 5, 2026 18:40

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rustbot added the perf-regression Performance regression. label Aug 6, 2026

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rust-timer commented Aug 6, 2026

Overall result: ❌✅ regressions and improvements - please read:

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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bjorn3 commented Jul 13, 2026 •

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