bootstrap/core/build_steps/
gcc.rs

1//! Compilation of native dependencies like GCC.
2//!
3//! Native projects like GCC unfortunately aren't suited just yet for
4//! compilation in build scripts that Cargo has. This is because the
5//! compilation takes a *very* long time but also because we don't want to
6//! compile GCC 3 times as part of a normal bootstrap (we want it cached).
7//!
8//! GCC and compiler-rt are essentially just wired up to everything else to
9//! ensure that they're always in place if needed.
10
11use std::fs;
12use std::path::{Path, PathBuf};
13use std::sync::OnceLock;
14
15use crate::FileType;
16use crate::core::builder::{Builder, Cargo, Kind, RunConfig, ShouldRun, Step};
17use crate::core::config::TargetSelection;
18use crate::utils::build_stamp::{BuildStamp, generate_smart_stamp_hash};
19use crate::utils::exec::command;
20use crate::utils::helpers::{self, t};
21
22#[derive(Debug, Clone, Hash, PartialEq, Eq)]
23pub struct Gcc {
24    pub target: TargetSelection,
25}
26
27#[derive(Clone)]
28pub struct GccOutput {
29    pub libgccjit: PathBuf,
30    target: TargetSelection,
31}
32
33impl GccOutput {
34    /// Install the required libgccjit library file(s) to the specified `path`.
35    pub fn install_to(&self, builder: &Builder<'_>, directory: &Path) {
36        if builder.config.dry_run() {
37            return;
38        }
39
40        let target_filename = self.libgccjit.file_name().unwrap().to_str().unwrap().to_string();
41
42        // If we build libgccjit ourselves, then `self.libgccjit` can actually be a symlink.
43        // In that case, we have to resolve it first, otherwise we'd create a symlink to a symlink,
44        // which wouldn't work.
45        let actual_libgccjit_path = t!(
46            self.libgccjit.canonicalize(),
47            format!("Cannot find libgccjit at {}", self.libgccjit.display())
48        );
49
50        let dest_dir = directory.join("rustlib").join(self.target).join("lib");
51        t!(fs::create_dir_all(&dest_dir));
52        let dst = dest_dir.join(target_filename);
53        builder.copy_link(&actual_libgccjit_path, &dst, FileType::NativeLibrary);
54    }
55}
56
57impl Step for Gcc {
58    type Output = GccOutput;
59
60    const IS_HOST: bool = true;
61
62    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
63        run.path("src/gcc").alias("gcc")
64    }
65
66    fn make_run(run: RunConfig<'_>) {
67        run.builder.ensure(Gcc { target: run.target });
68    }
69
70    /// Compile GCC (specifically `libgccjit`) for `target`.
71    fn run(self, builder: &Builder<'_>) -> Self::Output {
72        let target = self.target;
73
74        // If GCC has already been built, we avoid building it again.
75        let metadata = match get_gcc_build_status(builder, target) {
76            GccBuildStatus::AlreadyBuilt(path) => return GccOutput { libgccjit: path, target },
77            GccBuildStatus::ShouldBuild(m) => m,
78        };
79
80        let _guard = builder.msg_unstaged(Kind::Build, "GCC", target);
81        t!(metadata.stamp.remove());
82        let _time = helpers::timeit(builder);
83
84        let libgccjit_path = libgccjit_built_path(&metadata.install_dir);
85        if builder.config.dry_run() {
86            return GccOutput { libgccjit: libgccjit_path, target };
87        }
88
89        build_gcc(&metadata, builder, target);
90
91        t!(metadata.stamp.write());
92
93        GccOutput { libgccjit: libgccjit_path, target }
94    }
95}
96
97pub struct Meta {
98    stamp: BuildStamp,
99    out_dir: PathBuf,
100    install_dir: PathBuf,
101    root: PathBuf,
102}
103
104pub enum GccBuildStatus {
105    /// libgccjit is already built at this path
106    AlreadyBuilt(PathBuf),
107    ShouldBuild(Meta),
108}
109
110/// Tries to download GCC from CI if it is enabled and GCC artifacts
111/// are available for the given target.
112/// Returns a path to the libgccjit.so file.
113#[cfg(not(test))]
114fn try_download_gcc(builder: &Builder<'_>, target: TargetSelection) -> Option<PathBuf> {
115    use build_helper::git::PathFreshness;
116
117    // Try to download GCC from CI if configured and available
118    if !matches!(builder.config.gcc_ci_mode, crate::core::config::GccCiMode::DownloadFromCi) {
119        return None;
120    }
121    if target != "x86_64-unknown-linux-gnu" {
122        eprintln!("GCC CI download is only available for the `x86_64-unknown-linux-gnu` target");
123        return None;
124    }
125    let source = detect_gcc_freshness(
126        &builder.config,
127        builder.config.rust_info.is_managed_git_subrepository(),
128    );
129    builder.do_if_verbose(|| {
130        eprintln!("GCC freshness: {source:?}");
131    });
132    match source {
133        PathFreshness::LastModifiedUpstream { upstream } => {
134            // Download from upstream CI
135            let root = ci_gcc_root(&builder.config, target);
136            let gcc_stamp = BuildStamp::new(&root).with_prefix("gcc").add_stamp(&upstream);
137            if !gcc_stamp.is_up_to_date() && !builder.config.dry_run() {
138                builder.config.download_ci_gcc(&upstream, &root);
139                t!(gcc_stamp.write());
140            }
141
142            let libgccjit = root.join("lib").join("libgccjit.so");
143            Some(libgccjit)
144        }
145        PathFreshness::HasLocalModifications { .. } => {
146            // We have local modifications, rebuild GCC.
147            eprintln!("Found local GCC modifications, GCC will *not* be downloaded");
148            None
149        }
150        PathFreshness::MissingUpstream => {
151            eprintln!("error: could not find commit hash for downloading GCC");
152            eprintln!("HELP: maybe your repository history is too shallow?");
153            eprintln!("HELP: consider disabling `download-ci-gcc`");
154            eprintln!("HELP: or fetch enough history to include one upstream commit");
155            None
156        }
157    }
158}
159
160#[cfg(test)]
161fn try_download_gcc(_builder: &Builder<'_>, _target: TargetSelection) -> Option<PathBuf> {
162    None
163}
164
165/// This returns information about whether GCC should be built or if it's already built.
166/// It transparently handles downloading GCC from CI if needed.
167///
168/// It's used to avoid busting caches during x.py check -- if we've already built
169/// GCC, it's fine for us to not try to avoid doing so.
170pub fn get_gcc_build_status(builder: &Builder<'_>, target: TargetSelection) -> GccBuildStatus {
171    if let Some(path) = try_download_gcc(builder, target) {
172        return GccBuildStatus::AlreadyBuilt(path);
173    }
174
175    static STAMP_HASH_MEMO: OnceLock<String> = OnceLock::new();
176    let smart_stamp_hash = STAMP_HASH_MEMO.get_or_init(|| {
177        generate_smart_stamp_hash(
178            builder,
179            &builder.config.src.join("src/gcc"),
180            builder.in_tree_gcc_info.sha().unwrap_or_default(),
181        )
182    });
183
184    // Initialize the gcc submodule if not initialized already.
185    builder.config.update_submodule("src/gcc");
186
187    let root = builder.src.join("src/gcc");
188    let out_dir = builder.gcc_out(target).join("build");
189    let install_dir = builder.gcc_out(target).join("install");
190
191    let stamp = BuildStamp::new(&out_dir).with_prefix("gcc").add_stamp(smart_stamp_hash);
192
193    if stamp.is_up_to_date() {
194        if stamp.stamp().is_empty() {
195            builder.info(
196                "Could not determine the GCC submodule commit hash. \
197                     Assuming that an GCC rebuild is not necessary.",
198            );
199            builder.info(&format!(
200                "To force GCC to rebuild, remove the file `{}`",
201                stamp.path().display()
202            ));
203        }
204        let path = libgccjit_built_path(&install_dir);
205        if path.is_file() {
206            return GccBuildStatus::AlreadyBuilt(path);
207        } else {
208            builder.info(&format!(
209                "GCC stamp is up-to-date, but the libgccjit.so file was not found at `{}`",
210                path.display(),
211            ));
212        }
213    }
214
215    GccBuildStatus::ShouldBuild(Meta { stamp, out_dir, install_dir, root })
216}
217
218/// Returns the path to a libgccjit.so file in the install directory of GCC.
219fn libgccjit_built_path(install_dir: &Path) -> PathBuf {
220    install_dir.join("lib/libgccjit.so")
221}
222
223fn build_gcc(metadata: &Meta, builder: &Builder<'_>, target: TargetSelection) {
224    if builder.build.cc_tool(target).is_like_clang()
225        || builder.build.cxx_tool(target).is_like_clang()
226    {
227        panic!(
228            "Attempting to build GCC using Clang, which is known to misbehave. Please use GCC as the host C/C++ compiler. "
229        );
230    }
231
232    let Meta { stamp: _, out_dir, install_dir, root } = metadata;
233
234    t!(fs::create_dir_all(out_dir));
235    t!(fs::create_dir_all(install_dir));
236
237    // GCC creates files (e.g. symlinks to the downloaded dependencies)
238    // in the source directory, which does not work with our CI/Docker setup, where we mount
239    // source directories as read-only on Linux.
240    // And in general, we shouldn't be modifying the source directories if possible, even for local
241    // builds.
242    // Therefore, we first copy the whole source directory to the build directory, and perform the
243    // build from there.
244    let src_dir = builder.gcc_out(target).join("src");
245    if src_dir.exists() {
246        builder.remove_dir(&src_dir);
247    }
248    builder.create_dir(&src_dir);
249    builder.cp_link_r(root, &src_dir);
250
251    command(src_dir.join("contrib/download_prerequisites")).current_dir(&src_dir).run(builder);
252    let mut configure_cmd = command(src_dir.join("configure"));
253    configure_cmd
254        .current_dir(out_dir)
255        .arg("--enable-host-shared")
256        .arg("--enable-languages=c,jit,lto")
257        .arg("--enable-checking=release")
258        .arg("--disable-bootstrap")
259        .arg("--disable-multilib")
260        .arg(format!("--prefix={}", install_dir.display()));
261
262    let cc = builder.build.cc(target).display().to_string();
263    let cc = builder
264        .build
265        .config
266        .ccache
267        .as_ref()
268        .map_or_else(|| cc.clone(), |ccache| format!("{ccache} {cc}"));
269    configure_cmd.env("CC", cc);
270
271    if let Ok(ref cxx) = builder.build.cxx(target) {
272        let cxx = cxx.display().to_string();
273        let cxx = builder
274            .build
275            .config
276            .ccache
277            .as_ref()
278            .map_or_else(|| cxx.clone(), |ccache| format!("{ccache} {cxx}"));
279        configure_cmd.env("CXX", cxx);
280    }
281    configure_cmd.run(builder);
282
283    command("make")
284        .current_dir(out_dir)
285        .arg("--silent")
286        .arg(format!("-j{}", builder.jobs()))
287        .run_capture_stdout(builder);
288    command("make").current_dir(out_dir).arg("--silent").arg("install").run_capture_stdout(builder);
289}
290
291/// Configures a Cargo invocation so that it can build the GCC codegen backend.
292pub fn add_cg_gcc_cargo_flags(cargo: &mut Cargo, gcc: &GccOutput) {
293    // Add the path to libgccjit.so to the linker search paths.
294    cargo.rustflag(&format!("-L{}", gcc.libgccjit.parent().unwrap().to_str().unwrap()));
295}
296
297/// The absolute path to the downloaded GCC artifacts.
298#[cfg(not(test))]
299fn ci_gcc_root(config: &crate::Config, target: TargetSelection) -> PathBuf {
300    config.out.join(target).join("ci-gcc")
301}
302
303/// Detect whether GCC sources have been modified locally or not.
304#[cfg(not(test))]
305fn detect_gcc_freshness(config: &crate::Config, is_git: bool) -> build_helper::git::PathFreshness {
306    use build_helper::git::PathFreshness;
307
308    if is_git {
309        config.check_path_modifications(&["src/gcc", "src/bootstrap/download-ci-gcc-stamp"])
310    } else if let Some(info) = crate::utils::channel::read_commit_info_file(&config.src) {
311        PathFreshness::LastModifiedUpstream { upstream: info.sha.trim().to_owned() }
312    } else {
313        PathFreshness::MissingUpstream
314    }
315}
bootstrap/core/build_steps/gcc.rs

bootstrap/core/build_steps/
gcc.rs
