Add --compile-time-deps argument for x check #143785

bjorn3 · 2025-07-11T12:28:39Z

Together with skipping building C++ code in rustc_llvm for check, this reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m06s when the bootstrap compiler is already downloaded.

rustbot · 2025-07-11T12:28:44Z

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rustbot · 2025-07-11T12:28:46Z

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

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

This reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m34s when the bootstrap compiler is already downloaded.

This saves about 30s.

src/etc/completions/x.zsh

Kobzol · 2025-07-11T19:03:56Z

r? @Kobzol

I don't use RA much, so could you please walk me through what exactly this does? I know that RA/RustRover wanted this flag to only compile proc macros and compile + run build scripts to speed up the initial analysis of the crate. In RustRover it's not that critical, because it caches stuff heavily. If I understand it correctly, RA doesn't cache stuff between executions, so if you reopen the rustc project, it has to do x check from scratch to prime its analysis engine? And this will cause bootstrap to only do the minimum amount of work necessary to achieve that? So it only helps for the initial startup, but then if you make changes to rustc and RA runs x check in the background, it won't be applied?

ShoyuVanilla · 2025-07-11T19:31:51Z

r? @Kobzol

I don't use RA much, so could you please walk me through what exactly this does? I know that RA/RustRover wanted this flag to only compile proc macros and compile + run build scripts to speed up the initial analysis of the crate. In RustRover it's not that critical, because it caches stuff heavily. If I understand it correctly, RA doesn't cache stuff between executions, so if you reopen the rustc project, it has to do x check from scratch to prime its analysis engine? And this will cause bootstrap to only do the minimum amount of work necessary to achieve that? So it only helps for the initial startup, but then if you make changes to rustc and RA runs x check in the background, it won't be applied?

Basically you're correct but there are two things to clarify:

RA doesn't have persistent cache (yet) but it runs cargo check (--compile-time-deps) to build the necessary artifacts to the filesystem. So this is not directly related to cache priming and RA and RR can equally benefit from this.
And it only helps the very first run wrt build scripts and proc macro dependency changes. As mentioned above, all artifacts needed are built into filesystem and as you said, further interactions inside RA trigger cargo check without --compile-time-deps option and also leave artifacts to filesystem. Since then, any new runs won't benefit from this as there isn't anything to build when starting RA (though it might help slightly by reducing fingerprint checks)

Kobzol · 2025-07-11T19:35:34Z

I see. So it only helps if you open RA after clearing the build directory or changing the checked out rustc SHA a lot? 12 minutes sounds quite brutal, I wonder if the RA build script command should be changed to x check compiler instead of x check or something.

bjorn3 · 2025-07-11T19:43:10Z

So it only helps if you open RA after clearing the build directory or changing the checked out rustc SHA a lot?

Yes

I wonder if the RA build script command should be changed to x check compiler instead of x check or something.

That would hurt working on things other than rustc, like clippy, miri or rustfmt.

Kobzol

Could you please add a change_tracker.rs entry with Info level about this?

src/bootstrap/src/core/build_steps/compile.rs

Kobzol · 2025-07-12T12:37:37Z

Thanks! You can r=me once CI is green.

bjorn3 · 2025-07-12T15:52:54Z

@bors r=Kobzol

bors · 2025-07-12T15:52:57Z

📌 Commit 10bec8f has been approved by Kobzol

It is now in the queue for this repository.

…d, r=Kobzol Add --compile-time-deps argument for x check Together with skipping building C++ code in rustc_llvm for check, this reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m06s when the bootstrap compiler is already downloaded.

Rollup of 14 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143461 (make `cfg_select` a builtin macro) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143679 (Preserve the .debug_gdb_scripts section) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143704 (Be a bit more careful around exotic cycles in in the inliner) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

…d, r=Kobzol Add --compile-time-deps argument for x check Together with skipping building C++ code in rustc_llvm for check, this reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m06s when the bootstrap compiler is already downloaded.

Rollup of 13 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143461 (make `cfg_select` a builtin macro) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143679 (Preserve the .debug_gdb_scripts section) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

…d, r=Kobzol Add --compile-time-deps argument for x check Together with skipping building C++ code in rustc_llvm for check, this reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m06s when the bootstrap compiler is already downloaded.

Rollup of 11 pull requests Successful merges: - #143301 (`tests/ui`: A New Order [26/N]) - #143519 (Check assoc consts and tys later like assoc fns) - #143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - #143634 (interpret/allocation: expose init + write_wildcards on a range) - #143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - #143734 (Refactor resolve resolution bindings) - #143774 (constify `From` and `Into`) - #143785 (Add --compile-time-deps argument for x check) - #143786 (Fix fallback for CI_JOB_NAME) - #143825 (clippy: fix test filtering when TESTNAME is empty) - #143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #143785 - bjorn3:faster_ra_build_script_build, r=Kobzol Add --compile-time-deps argument for x check Together with skipping building C++ code in rustc_llvm for check, this reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m06s when the bootstrap compiler is already downloaded.

Rollup of 11 pull requests Successful merges: - rust-lang/rust#143301 (`tests/ui`: A New Order [26/N]) - rust-lang/rust#143519 (Check assoc consts and tys later like assoc fns) - rust-lang/rust#143554 (slice: Mark `rotate_left`, `rotate_right` unstably const) - rust-lang/rust#143634 (interpret/allocation: expose init + write_wildcards on a range) - rust-lang/rust#143685 (Resolve: merge `source_bindings` and `target_bindings` into `bindings`) - rust-lang/rust#143734 (Refactor resolve resolution bindings) - rust-lang/rust#143774 (constify `From` and `Into`) - rust-lang/rust#143785 (Add --compile-time-deps argument for x check) - rust-lang/rust#143786 (Fix fallback for CI_JOB_NAME) - rust-lang/rust#143825 (clippy: fix test filtering when TESTNAME is empty) - rust-lang/rust#143826 (Fix command trace) r? `@ghost` `@rustbot` modify labels: rollup

RalfJung · 2025-09-26T06:49:12Z

compiler/rustc_llvm/Cargo.toml

 # tidy-alphabetical-end
+
+[features]
+# Used by ./x.py check --compile-time-deps to skip building C++ code


Why is this only set with compile-time-deps? A regular check build also doesn't need the LLVM libraries, does it?

To not change existing behavior for ./x.py check. If this is also set for ./x.py check, that will no longer check if all C++ source files compile.

Hm, fair... I never change those files so it's kind of unnecessary, but then the same is true for the Rust files in rustc_llvm. But those ofc check a lot faster than they build whereas the C++ files always do a full build :/

With #146596 you may be able to disable the LLVM backend entirely for stage 1 builds if ./x.py miri were to use the bootstrap compiler for building the build scripts of the standard library.

Oh, funky. But most of the time I do need codegen as well (even Miri does, for build scripts and proc macros -- not sure if those can just use a different stage).

When bootstrap builds the standard library it uses different stages for build scripts and for the standard library itself. This does use a wrapper around rustc though.

rustbot assigned clubby789 Jul 11, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Jul 11, 2025

bjorn3 mentioned this pull request Jul 11, 2025

Allow disabling the FFI integration with a feature rust-lang/miri#4461

Open

bjorn3 force-pushed the faster_ra_build_script_build branch from dc7dab3 to 6f2d900 Compare July 11, 2025 12:33

Add --compile-time-deps argument for x check

3fe3edb

This reduces the amount of time it takes to do the x check for rust-analyzer analysis from 12m16s to 3m34s when the bootstrap compiler is already downloaded.

bjorn3 force-pushed the faster_ra_build_script_build branch from 6f2d900 to 3fe3edb Compare July 11, 2025 12:34

bjorn3 mentioned this pull request Jul 11, 2025

internal: Utilize cargo check --compile-time-deps rust-lang/rust-analyzer#20047

Merged

Avoid building C++ for rustc_llvm with --compile-time-deps

87958ad

This saves about 30s.

rustbot added the A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. label Jul 11, 2025

RalfJung reviewed Jul 11, 2025

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src/etc/completions/x.zsh Outdated Show resolved Hide resolved

Update description for flag

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rustbot assigned Kobzol and unassigned clubby789 Jul 11, 2025

Kobzol reviewed Jul 11, 2025

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src/bootstrap/src/core/build_steps/compile.rs Outdated Show resolved Hide resolved

Move --compile-time-deps

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bjorn3 force-pushed the faster_ra_build_script_build branch from df124d1 to ccc302b Compare July 12, 2025 12:34

Add change_tracker.rs entry

10bec8f

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 Jul 12, 2025

fmease mentioned this pull request Jul 13, 2025

Rollup of 14 pull requests #143866

Closed

matthiaskrgr mentioned this pull request Jul 13, 2025

Rollup of 13 pull requests #143876

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This was referenced Jul 13, 2025

Rollup of 12 pull requests #143886

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Rollup of 11 pull requests #143888

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bors merged commit b4b00c7 into rust-lang:master Jul 13, 2025
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rustbot added this to the 1.90.0 milestone Jul 13, 2025

bjorn3 deleted the faster_ra_build_script_build branch July 13, 2025 18:34

RalfJung reviewed Sep 26, 2025

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Add --compile-time-deps argument for x check #143785

Add --compile-time-deps argument for x check #143785

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