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

bootstrap/core/build_steps/
gcc.rs
