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Merged
merged 2 commits into from
Aug 26, 2025
Merged

Remove unnecessary stage2 host builds from cross-compiled dist builders #145874

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598387b
Add snapshot test for cross-compiled dist without docs
Kobzol Aug 26, 2025
c7f90c1
Do not unnecessarily build stage2 host rustc in some dist builders
Kobzol Aug 26, 2025
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20 changes: 16 additions & 4 deletions src/bootstrap/src/core/build_steps/dist.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -764,10 +764,22 @@ pub struct Std {

impl Std {
pub fn new(builder: &Builder<'_>, target: TargetSelection) -> Self {
Std {
build_compiler: builder.compiler(builder.top_stage, builder.config.host_target),
target,
}
// This is an important optimization mainly for CI.
// Normally, to build stage N libstd, we need stage N rustc.
// However, if we know that we will uplift libstd from stage 1 anyway, building the stage N
// rustc can be wasteful.
// In particular, if we do a cross-compiling dist stage 2 build from T1 to T2, we need:
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@hkBst hkBst Aug 26, 2025 •
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Does 'T' stand for target? I suggest spelling it out whatever it is. Alternatives: machine, arch(itecture)

// - stage 2 libstd for T2 (uplifted from stage 1, where it was built by T1 rustc)
// - stage 2 rustc for T2
// However, without this optimization, we would also build stage 2 rustc for **T1**, which
// is completely wasteful.
let build_compiler =
if compile::Std::should_be_uplifted_from_stage_1(builder, builder.top_stage, target) {
builder.compiler(1, builder.host_target)
} else {
builder.compiler(builder.top_stage, builder.host_target)
};
Std { build_compiler, target }
}
}

Expand Down
3 changes: 1 addition & 2 deletions src/bootstrap/src/core/builder/mod.rs
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Expand Up @@ -145,8 +145,7 @@ pub trait Step: 'static + Clone + Debug + PartialEq + Eq + Hash {
}

/// Metadata that describes an executed step, mostly for testing and tracing.
#[allow(unused)]
#[derive(Debug, PartialEq, Eq)]
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct StepMetadata {
name: String,
kind: Kind,
Expand Down
120 changes: 95 additions & 25 deletions src/bootstrap/src/core/builder/tests.rs
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Expand Up @@ -1133,8 +1133,7 @@ mod snapshot {
[dist] mingw <host>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <host>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
[dist] src <>
[dist] reproducible-artifacts <host>
Expand Down Expand Up @@ -1198,8 +1197,7 @@ mod snapshot {
[build] rustc 1 <host> -> rust-analyzer-proc-macro-srv 2 <host>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <host>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
[dist] rustc 1 <host> -> analysis 2 <host>
[dist] src <>
Expand All @@ -1216,7 +1214,6 @@ mod snapshot {
[build] rustc 1 <host> -> miri 2 <host>
[build] rustc 1 <host> -> cargo-miri 2 <host>
[dist] rustc 1 <host> -> miri 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> extended 2 <host>
[dist] reproducible-artifacts <host>
");
Expand Down Expand Up @@ -1287,8 +1284,7 @@ mod snapshot {
[dist] mingw <target1>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <host>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[build] rustc 2 <host> -> std 2 <target1>
[dist] rustc 2 <host> -> std 2 <target1>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
Expand Down Expand Up @@ -1350,8 +1346,7 @@ mod snapshot {
[dist] rustc <host>
[build] rustdoc 2 <target1>
[dist] rustc <target1>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <target1>
[dist] src <>
Expand Down Expand Up @@ -1433,10 +1428,8 @@ mod snapshot {
[dist] rustc <host>
[build] rustdoc 2 <target1>
[dist] rustc <target1>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[build] rustc 2 <host> -> std 2 <target1>
[dist] rustc 2 <host> -> std 2 <target1>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> std 1 <target1>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <target1>
[dist] src <>
Expand Down Expand Up @@ -1490,10 +1483,8 @@ mod snapshot {
");
}

/// This also serves as an important regression test for <https://github.com/rust-lang/rust/issues/138123>
/// and <https://github.com/rust-lang/rust/issues/138004>.
#[test]
fn dist_all_cross() {
fn dist_all_cross_extended() {
let ctx = TestCtx::new();
insta::assert_snapshot!(
ctx
Expand Down Expand Up @@ -1545,8 +1536,7 @@ mod snapshot {
[build] rustc 1 <host> -> rust-analyzer-proc-macro-srv 2 <target1>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <target1>
[build] rustc 2 <host> -> std 2 <target1>
[dist] rustc 2 <host> -> std 2 <target1>
[dist] rustc 1 <host> -> std 1 <target1>
[dist] rustc 1 <host> -> rustc-dev 2 <target1>
[dist] rustc 1 <host> -> analysis 2 <target1>
[dist] src <>
Expand All @@ -1564,15 +1554,82 @@ mod snapshot {
[build] rustc 1 <host> -> cargo-miri 2 <target1>
[dist] rustc 1 <host> -> miri 2 <target1>
[build] rustc 1 <host> -> LlvmBitcodeLinker 2 <target1>
[dist] rustc 1 <host> -> std 1 <target1>
[doc] rustc 2 <target1> -> std 2 <target1> crates=[]
[dist] rustc 1 <host> -> extended 2 <target1>
[dist] reproducible-artifacts <target1>
");
}

// Enable dist cranelift tarball by default with `x dist` if cranelift is enabled in
// `rust.codegen-backends`.
/// Simulates e.g. the powerpc64 builder, which is fully cross-compiled from x64, but it does
/// not build docs. Crutically, it shouldn't build host stage 2 rustc.
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Crucially or Critically?

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Haha :D Thanks, I'll fix it in a followup PR.

///
/// This is a regression test for <https://github.com/rust-lang/rust/issues/138123>
/// and <https://github.com/rust-lang/rust/issues/138004>.
#[test]
fn dist_all_cross_extended_no_docs() {
let ctx = TestCtx::new();
let steps = ctx
.config("dist")
.hosts(&[TEST_TRIPLE_1])
.targets(&[TEST_TRIPLE_1])
.args(&[
"--set",
"rust.channel=nightly",
"--set",
"build.extended=true",
"--set",
"build.docs=false",
])
.get_steps();

// Make sure that we don't build stage2 host rustc
steps.assert_no_match(|m| {
m.name == "rustc"
&& m.built_by.map(|b| b.stage) == Some(1)
&& *m.target.triple == host_target()
});

insta::assert_snapshot!(
steps.render(), @r"
[dist] mingw <target1>
[build] llvm <host>
[build] llvm <target1>
[build] rustc 0 <host> -> rustc 1 <host>
[build] rustc 0 <host> -> WasmComponentLd 1 <host>
[build] rustc 1 <host> -> std 1 <target1>
[build] rustc 1 <host> -> std 1 <host>
[build] rustc 1 <host> -> rustc 2 <target1>
[build] rustc 1 <host> -> WasmComponentLd 2 <target1>
[build] rustdoc 2 <target1>
[build] rustc 1 <host> -> rust-analyzer-proc-macro-srv 2 <target1>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[build] rustc 0 <host> -> RustInstaller 1 <host>
[dist] rustc <target1>
[dist] rustc 1 <host> -> std 1 <target1>
[dist] rustc 1 <host> -> rustc-dev 2 <target1>
[dist] rustc 1 <host> -> analysis 2 <target1>
[dist] src <>
[build] rustc 1 <host> -> cargo 2 <target1>
[dist] rustc 1 <host> -> cargo 2 <target1>
[build] rustc 1 <host> -> rust-analyzer 2 <target1>
[dist] rustc 1 <host> -> rust-analyzer 2 <target1>
[build] rustc 1 <host> -> rustfmt 2 <target1>
[build] rustc 1 <host> -> cargo-fmt 2 <target1>
[dist] rustc 1 <host> -> rustfmt 2 <target1>
[build] rustc 1 <host> -> clippy-driver 2 <target1>
[build] rustc 1 <host> -> cargo-clippy 2 <target1>
[dist] rustc 1 <host> -> clippy 2 <target1>
[build] rustc 1 <host> -> miri 2 <target1>
[build] rustc 1 <host> -> cargo-miri 2 <target1>
[dist] rustc 1 <host> -> miri 2 <target1>
[build] rustc 1 <host> -> LlvmBitcodeLinker 2 <target1>
[dist] rustc 1 <host> -> extended 2 <target1>
[dist] reproducible-artifacts <target1>
");
}

/// Enable dist cranelift tarball by default with `x dist` if cranelift is enabled in
/// `rust.codegen-backends`.
#[test]
fn dist_cranelift_by_default() {
let ctx = TestCtx::new();
Expand Down Expand Up @@ -1619,8 +1676,7 @@ mod snapshot {
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <host>
[dist] rustc 1 <host> -> rustc_codegen_cranelift 2 <host>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[dist] rustc 1 <host> -> rustc-dev 2 <host>
[dist] src <>
[dist] reproducible-artifacts <host>
Expand Down Expand Up @@ -2351,8 +2407,7 @@ mod snapshot {
[doc] rustc 1 <host> -> releases 2 <host>
[build] rustc 0 <host> -> RustInstaller 1 <host>
[dist] docs <host>
[build] rustc 2 <host> -> std 2 <host>
[dist] rustc 2 <host> -> std 2 <host>
[dist] rustc 1 <host> -> std 1 <host>
[build] rustc 1 <host> -> rust-analyzer-proc-macro-srv 2 <host>
[build] rustc 0 <host> -> GenerateCopyright 1 <host>
[dist] rustc <host>
Expand Down Expand Up @@ -2426,6 +2481,21 @@ impl ExecutedSteps {
}
}

/// Make sure that no metadata matches the given `func`.
#[track_caller]
fn assert_no_match<F>(&self, func: F)
where
F: Fn(StepMetadata) -> bool,
{
for metadata in self.steps.iter().filter_map(|s| s.metadata.clone()) {
if func(metadata.clone()) {
panic!(
"Metadata {metadata:?} was found, even though it should have not been present"
);
}
}
}

fn contains(&self, metadata: &StepMetadata) -> bool {
self.steps
.iter()
Expand Down
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