Introduce new bootstrap config section for PGO configuration by Kobzol · Pull Request #158912 · rust-lang/rust

Kobzol · 2026-07-07T14:15:59Z

The handling of PGO profiles in bootstrap was a bit messy, we had CLI flags, but those were hardcoded only for rustc and LLVM, and also a separate rust.profile-use/profile-generate options, though I'm not sure if anyone ever used them.

I wanted to generalize this a bit, to allow experimenting with PGO optimizing also other parts of the toolchain (e.g. rustdoc, clippy, cargo). This PR introduces a new [pgo] section in the bootstrap config, which allows specifying PGO profiles using the config file, currently for rustc and LLVM.

It can be also set through the command-line using e.g. --set pgo.rustc.use=/tmp/foo.

Best reviewed commit by commit.

r? @jieyouxu

Kobzol · 2026-07-07T14:16:16Z

@bors try @rust-timer queue

Introduce new bootstrap config section for PGO configuration

rust-bors · 2026-07-07T14:26:26Z

💔 Test for 1b53849 failed: CI. Failed job:

try - dist-x86_64-linux-quick (web logs, enhanced plaintext logs)

Kobzol · 2026-07-07T14:34:23Z

@bors try

Introduce new bootstrap config section for PGO configuration

rust-bors · 2026-07-07T16:42:58Z

☀️ Try build successful (CI)
Build commit: f74b2a3 (f74b2a373248202435989c77fcf0ce204e8bd5a5)
Base parent: f10db29 (f10db292a3733b5c67c8da8c7661195ff4b05774)

rust-timer · 2026-07-07T18:55:40Z

Finished benchmarking commit (f74b2a3): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

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

Max RSS (memory usage)

This perf run didn't have relevant results for this metric.

Cycles

Results (secondary 3.5%)

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)	3.5%	[2.0%, 5.2%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.1%, 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)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	61
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	24
All ❌✅ (primary)	-0.1%	[-0.1%, -0.0%]	61

Bootstrap: 487.206s -> 488.631s (0.29%)
Artifact size: 388.97 MiB -> 388.95 MiB (-0.01%)

rustbot · 2026-07-07T18:57:15Z

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

This PR modifies bootstrap.example.toml.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp.

jieyouxu

Thanks
@bors r+

View changes since this review

rust-bors · 2026-07-08T11:52:12Z

📌 Commit 1f6b1d5 has been approved by jieyouxu

It is now in the queue for this repository.

@jieyouxu

…youxu Introduce new bootstrap config section for PGO configuration The handling of PGO profiles in bootstrap was a bit messy, we had CLI flags, but those were hardcoded only for rustc and LLVM, and also a separate `rust.profile-use/profile-generate` options, though I'm not sure if anyone ever used them. I wanted to generalize this a bit, to allow experimenting with PGO optimizing also other parts of the toolchain (e.g. rustdoc, clippy, cargo). This PR introduces a new `[pgo]` section in the bootstrap config, which allows specifying PGO profiles using the config file, currently for `rustc` and LLVM. It can be also set through the command-line using e.g. `--set pgo.rustc.use=/tmp/foo`. Best reviewed commit by commit. r? @jieyouxu

@jieyouxu

…youxu Introduce new bootstrap config section for PGO configuration The handling of PGO profiles in bootstrap was a bit messy, we had CLI flags, but those were hardcoded only for rustc and LLVM, and also a separate `rust.profile-use/profile-generate` options, though I'm not sure if anyone ever used them. I wanted to generalize this a bit, to allow experimenting with PGO optimizing also other parts of the toolchain (e.g. rustdoc, clippy, cargo). This PR introduces a new `[pgo]` section in the bootstrap config, which allows specifying PGO profiles using the config file, currently for `rustc` and LLVM. It can be also set through the command-line using e.g. `--set pgo.rustc.use=/tmp/foo`. Best reviewed commit by commit. r? @jieyouxu

@jieyouxu

…youxu Introduce new bootstrap config section for PGO configuration The handling of PGO profiles in bootstrap was a bit messy, we had CLI flags, but those were hardcoded only for rustc and LLVM, and also a separate `rust.profile-use/profile-generate` options, though I'm not sure if anyone ever used them. I wanted to generalize this a bit, to allow experimenting with PGO optimizing also other parts of the toolchain (e.g. rustdoc, clippy, cargo). This PR introduces a new `[pgo]` section in the bootstrap config, which allows specifying PGO profiles using the config file, currently for `rustc` and LLVM. It can be also set through the command-line using e.g. `--set pgo.rustc.use=/tmp/foo`. Best reviewed commit by commit. r? @jieyouxu

@jieyouxu

…youxu Introduce new bootstrap config section for PGO configuration The handling of PGO profiles in bootstrap was a bit messy, we had CLI flags, but those were hardcoded only for rustc and LLVM, and also a separate `rust.profile-use/profile-generate` options, though I'm not sure if anyone ever used them. I wanted to generalize this a bit, to allow experimenting with PGO optimizing also other parts of the toolchain (e.g. rustdoc, clippy, cargo). This PR introduces a new `[pgo]` section in the bootstrap config, which allows specifying PGO profiles using the config file, currently for `rustc` and LLVM. It can be also set through the command-line using e.g. `--set pgo.rustc.use=/tmp/foo`. Best reviewed commit by commit. r? @jieyouxu

…uwer Rollup of 25 pull requests Successful merges: - #158871 (add relnotes for 1.97.0) - #158968 (stdarch subtree update) - #154445 (rustdoc: Represent `--output-format=json` coverage and ir differently) - #156370 (Reject linked dylib EII default overrides) - #157153 (allow `Allocator`s to be used as `#[global_allocator]`s) - #158495 (Rename HAS_CT_PROJECTION to HAS_CONST_ALIAS) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158655 (Fix coroutine MIR saved local remapping) - #158666 (Carry the `b_offset` inside `BackendRepr::ScalarPair`) - #158912 (Introduce new bootstrap config section for PGO configuration) - #158920 (Update wasm-component-ld to 0.5.26) - #158926 (wrapping_sh* methods: clarify underspecified reference) - #158927 (add core test run with `-Zforce-intrinsic-fallback`) - #158932 (Do not build the compiler when invoking `x perf compare`) - #158937 (Emit the emscripten entry point as `__main_argc_argv`) - #151379 (Stabilize `VecDeque::retain_back` from `truncate_front`) - #156548 ( Library support for aarch64-unknown-linux-pauthtest target) - #158307 (CI job for parallel frontend ui tests) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158741 (Simplify `Option::into_flat_iter` signature) - #158807 (Add regression test for CString::clone_into unwind safety) - #158862 (Fix the span for parameter suggestion ) - #158883 (tests: fix enum-match.rs to handle LLVM 23)

jhpratt · 2026-07-08T23:31:03Z

@bors r- #158977 (comment)

failed to parse override `pgo.rustc.generate="C:\a\rust\rust\opt-artifacts\rustc-pgo"`: `invalid escape character in string: `a` at line 1 column 24
Bootstrap failed while executing `build --target x86_64-pc-windows-msvc --host x86_64-pc-windows-msvc --stage 2 library/std --set pgo.rustc.generate="C:\a\rust\rust\opt-artifacts\rustc-pgo"`
Build completed unsuccessfully in 0:00:00
[2026-07-08T23:12:54.979Z INFO  opt_dist::timer] Section `Stage 1 (Rustc PGO) > Build PGO instrumented rustc and LLVM` ended: FAIL (0.35s)`
[2026-07-08T23:12:54.979Z INFO  opt_dist::timer] Section `Stage 1 (Rustc PGO)` ended: FAIL (0.35s)`

rust-bors · 2026-07-08T23:31:10Z

This pull request was unapproved.

This PR was contained in a rollup (#158977), which was unapproved.

View changes since this unapproval

Kobzol added 3 commits July 7, 2026 15:51

Add new PGO config section to bootstrap

017255b

Port LLVM PGO to the new PGO config section

33da2c8

Use the new bootstrap PGO options in opt-dist

b576701

rustbot assigned jieyouxu Jul 7, 2026

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Jul 7, 2026

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rust-bors Bot pushed a commit that referenced this pull request Jul 7, 2026

Auto merge of #158912 - Kobzol:bootstrap-pgo-config, r=<try>

1b53849

Introduce new bootstrap config section for PGO configuration

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rust-bors Bot pushed a commit that referenced this pull request Jul 7, 2026

Auto merge of #158912 - Kobzol:bootstrap-pgo-config, r=<try>

f74b2a3

Introduce new bootstrap config section for PGO configuration

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 7, 2026

Kobzol marked this pull request as ready for review July 7, 2026 18:57

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 7, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 7, 2026

Fix bootstrap example TOML

1f6b1d5

Kobzol force-pushed the bootstrap-pgo-config branch from 3fbde4b to 1f6b1d5 Compare July 8, 2026 06:46

jieyouxu approved these changes Jul 8, 2026

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rust-bors Bot added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Jul 8, 2026

rust-bors Bot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 8, 2026

JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 12 pull requests #158963

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JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 14 pull requests #158971

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JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 25 pull requests #158973

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JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 25 pull requests #158977

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rust-bors Bot 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 8, 2026

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rust-timer commented Jul 7, 2026

Overall result: ❌ regressions - no action needed

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