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Commit 6a409dd

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jyn514onur-ozkan
authored andcommitted
add a new optimized_compiler_builtins option
in particular, this makes the `c` feature for compiler-builtins an explicit opt-in, rather than silently detected by whether `llvm-project` is checked out on disk. exposing this is necessary because the `cc` crate doesn't support cross-compiling to MSVC, and we want people to be able to run `x check --target foo` regardless of whether they have a c toolchain available. this also uses the new option in CI, where we *do* want to optimize compiler_builtins. the new option is off by default for the `dev` channel and on otherwise.
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-5
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7 files changed

+47
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‎config.example.toml

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@@ -339,6 +339,14 @@
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# on this runtime, such as `-C profile-generate` or `-C instrument-coverage`).
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#profiler = false
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# Use the optimized LLVM C intrinsics for `compiler_builtins`, rather than Rust intrinsics.
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# Requires the LLVM submodule to be managed by bootstrap (i.e. not external) so that `compiler-rt`
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# sources are available.
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#
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# Setting this to `false` generates slower code, but removes the requirement for a C toolchain in
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# order to run `x check`.
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#optimized-compiler-builtins = if rust.channel == "dev" { false } else { true }
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# Indicates whether the native libraries linked into Cargo will be statically
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# linked or not.
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#cargo-native-static = false

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

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@@ -382,9 +382,7 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
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// Determine if we're going to compile in optimized C intrinsics to
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// the `compiler-builtins` crate. These intrinsics live in LLVM's
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// `compiler-rt` repository, but our `src/llvm-project` submodule isn't
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// always checked out, so we need to conditionally look for this. (e.g. if
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// an external LLVM is used we skip the LLVM submodule checkout).
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// `compiler-rt` repository.
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//
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// Note that this shouldn't affect the correctness of `compiler-builtins`,
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// but only its speed. Some intrinsics in C haven't been translated to Rust
@@ -395,8 +393,21 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
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// If `compiler-rt` is available ensure that the `c` feature of the
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// `compiler-builtins` crate is enabled and it's configured to learn where
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// `compiler-rt` is located.
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let compiler_builtins_root = builder.src.join("src/llvm-project/compiler-rt");
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let compiler_builtins_c_feature = if compiler_builtins_root.exists() {
396+
let compiler_builtins_c_feature = if builder.config.optimized_compiler_builtins {
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// NOTE: this interacts strangely with `llvm-has-rust-patches`. In that case, we enforce `submodules = false`, so this is a no-op.
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// But, the user could still decide to manually use an in-tree submodule.
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//
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// NOTE: if we're using system llvm, we'll end up building a version of `compiler-rt` that doesn't match the LLVM we're linking to.
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// That's probably ok? At least, the difference wasn't enforced before. There's a comment in
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// the compiler_builtins build script that makes me nervous, though:
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// https://github.com/rust-lang/compiler-builtins/blob/31ee4544dbe47903ce771270d6e3bea8654e9e50/build.rs#L575-L579
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builder.update_submodule(&Path::new("src").join("llvm-project"));
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let compiler_builtins_root = builder.src.join("src/llvm-project/compiler-rt");
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if !compiler_builtins_root.exists() {
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panic!(
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"need LLVM sources available to build `compiler-rt`, but they weren't present; consider enabling `build.submodules = true` or disabling `optimized-compiler-builtins`"
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);
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}
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// Note that `libprofiler_builtins/build.rs` also computes this so if
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// you're changing something here please also change that.
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cargo.env("RUST_COMPILER_RT_ROOT", &compiler_builtins_root);

‎src/bootstrap/src/core/config/config.rs

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@@ -178,6 +178,8 @@ pub struct Config {
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pub patch_binaries_for_nix: Option<bool>,
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pub stage0_metadata: Stage0Metadata,
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pub android_ndk: Option<PathBuf>,
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/// Whether to use the `c` feature of the `compiler_builtins` crate.
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pub optimized_compiler_builtins: bool,
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pub stdout_is_tty: bool,
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pub stderr_is_tty: bool,
@@ -848,6 +850,7 @@ define_config! {
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// NOTE: only parsed by bootstrap.py, `--feature build-metrics` enables metrics unconditionally
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metrics: Option<bool> = "metrics",
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android_ndk: Option<PathBuf> = "android-ndk",
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optimized_compiler_builtins: Option<bool> = "optimized-compiler-builtins",
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}
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}
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@@ -1396,6 +1399,7 @@ impl Config {
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// This field is only used by bootstrap.py
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metrics: _,
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android_ndk,
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optimized_compiler_builtins,
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} = toml.build.unwrap_or_default();
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14011405
if let Some(file_build) = build {
@@ -1916,6 +1920,8 @@ impl Config {
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config.rust_debuginfo_level_std = with_defaults(debuginfo_level_std);
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config.rust_debuginfo_level_tools = with_defaults(debuginfo_level_tools);
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config.rust_debuginfo_level_tests = debuginfo_level_tests.unwrap_or(DebuginfoLevel::None);
1923+
config.optimized_compiler_builtins =
1924+
optimized_compiler_builtins.unwrap_or(config.channel != "dev");
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19201926
let download_rustc = config.download_rustc_commit.is_some();
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// See https://github.com/rust-lang/compiler-team/issues/326

‎src/bootstrap/src/utils/change_tracker.rs

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@@ -106,4 +106,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
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severity: ChangeSeverity::Info,
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summary: "The dist.missing-tools config option was deprecated, as it was unused. If you are using it, remove it from your config, it will be removed soon.",
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},
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ChangeInfo {
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change_id: 102579,
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severity: ChangeSeverity::Warning,
112+
summary: "A new `optimized-compiler-builtins` option has been introduced. Whether to build llvm's `compiler-rt` from source is no longer implicitly controlled by git state. See the PR for more details.",
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},
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];

‎src/ci/docker/host-x86_64/disabled/dist-x86_64-haiku/Dockerfile

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@@ -47,4 +47,6 @@ ENV RUST_CONFIGURE_ARGS --disable-jemalloc \
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--set=$TARGET.cc=x86_64-unknown-haiku-gcc \
4848
--set=$TARGET.cxx=x86_64-unknown-haiku-g++ \
4949
--set=$TARGET.llvm-config=/bin/llvm-config-haiku
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ENV EXTERNAL_LLVM 1
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ENV SCRIPT python3 ../x.py dist --host=$HOST --target=$HOST

‎src/ci/docker/host-x86_64/x86_64-gnu-llvm-17/Dockerfile

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@@ -40,6 +40,7 @@ RUN sh /scripts/sccache.sh
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# We are disabling CI LLVM since this builder is intentionally using a host
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# LLVM, rather than the typical src/llvm-project LLVM.
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ENV NO_DOWNLOAD_CI_LLVM 1
43+
ENV EXTERNAL_LLVM 1
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# Using llvm-link-shared due to libffi issues -- see #34486
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ENV RUST_CONFIGURE_ARGS \

‎src/ci/run.sh

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@@ -80,6 +80,15 @@ fi
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# space required for CI artifacts.
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RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --dist-compression-formats=xz"
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83+
# Enable the `c` feature for compiler_builtins, but only when the `compiler-rt` source is available
84+
# (to avoid spending a lot of time cloning llvm)
85+
if [ "$EXTERNAL_LLVM" = "" ]; then
86+
RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set build.optimized-compiler-builtins"
87+
elif [ "$DEPLOY$DEPLOY_ALT" = "1" ]; then
88+
echo "error: dist builds should always use optimized compiler-rt!" >&2
89+
exit 1
90+
fi
91+
8392
if [ "$DIST_SRC" = "" ]; then
8493
RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-dist-src"
8594
fi

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