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        // At build time, cg_gcc has to link to libgccjit.so (the unversioned symbol).
36        // However, at runtime, it will by default look for libgccjit.so.0.
37        // So when we install the built libgccjit.so file to the target `directory`, we add it there
38        // with the `.0` suffix.
39        let mut target_filename = self.libgccjit.file_name().unwrap().to_str().unwrap().to_string();
40        target_filename.push_str(".0");
41
42        let dst = directory.join(target_filename);
43        builder.copy_link(&self.libgccjit, &dst, FileType::NativeLibrary);
44    }
45}
46
47impl Step for Gcc {
48    type Output = GccOutput;
49
50    const IS_HOST: bool = true;
51
52    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
53        run.path("src/gcc").alias("gcc")
54    }
55
56    fn make_run(run: RunConfig<'_>) {
57        run.builder.ensure(Gcc { target: run.target });
58    }
59
60    /// Compile GCC (specifically `libgccjit`) for `target`.
61    fn run(self, builder: &Builder<'_>) -> Self::Output {
62        let target = self.target;
63
64        // If GCC has already been built, we avoid building it again.
65        let metadata = match get_gcc_build_status(builder, target) {
66            GccBuildStatus::AlreadyBuilt(path) => return GccOutput { libgccjit: path },
67            GccBuildStatus::ShouldBuild(m) => m,
68        };
69
70        let _guard = builder.msg_unstaged(Kind::Build, "GCC", target);
71        t!(metadata.stamp.remove());
72        let _time = helpers::timeit(builder);
73
74        let libgccjit_path = libgccjit_built_path(&metadata.install_dir);
75        if builder.config.dry_run() {
76            return GccOutput { libgccjit: libgccjit_path };
77        }
78
79        build_gcc(&metadata, builder, target);
80
81        t!(metadata.stamp.write());
82
83        GccOutput { libgccjit: libgccjit_path }
84    }
85}
86
87pub struct Meta {
88    stamp: BuildStamp,
89    out_dir: PathBuf,
90    install_dir: PathBuf,
91    root: PathBuf,
92}
93
94pub enum GccBuildStatus {
95    /// libgccjit is already built at this path
96    AlreadyBuilt(PathBuf),
97    ShouldBuild(Meta),
98}
99
100/// Tries to download GCC from CI if it is enabled and GCC artifacts
101/// are available for the given target.
102/// Returns a path to the libgccjit.so file.
103#[cfg(not(test))]
104fn try_download_gcc(builder: &Builder<'_>, target: TargetSelection) -> Option<PathBuf> {
105    use build_helper::git::PathFreshness;
106
107    // Try to download GCC from CI if configured and available
108    if !matches!(builder.config.gcc_ci_mode, crate::core::config::GccCiMode::DownloadFromCi) {
109        return None;
110    }
111    if target != "x86_64-unknown-linux-gnu" {
112        eprintln!("GCC CI download is only available for the `x86_64-unknown-linux-gnu` target");
113        return None;
114    }
115    let source = detect_gcc_freshness(
116        &builder.config,
117        builder.config.rust_info.is_managed_git_subrepository(),
118    );
119    builder.verbose(|| {
120        eprintln!("GCC freshness: {source:?}");
121    });
122    match source {
123        PathFreshness::LastModifiedUpstream { upstream } => {
124            // Download from upstream CI
125            let root = ci_gcc_root(&builder.config, target);
126            let gcc_stamp = BuildStamp::new(&root).with_prefix("gcc").add_stamp(&upstream);
127            if !gcc_stamp.is_up_to_date() && !builder.config.dry_run() {
128                builder.config.download_ci_gcc(&upstream, &root);
129                t!(gcc_stamp.write());
130            }
131
132            let libgccjit = root.join("lib").join("libgccjit.so");
133            Some(libgccjit)
134        }
135        PathFreshness::HasLocalModifications { .. } => {
136            // We have local modifications, rebuild GCC.
137            eprintln!("Found local GCC modifications, GCC will *not* be downloaded");
138            None
139        }
140        PathFreshness::MissingUpstream => {
141            eprintln!("error: could not find commit hash for downloading GCC");
142            eprintln!("HELP: maybe your repository history is too shallow?");
143            eprintln!("HELP: consider disabling `download-ci-gcc`");
144            eprintln!("HELP: or fetch enough history to include one upstream commit");
145            None
146        }
147    }
148}
149
150#[cfg(test)]
151fn try_download_gcc(_builder: &Builder<'_>, _target: TargetSelection) -> Option<PathBuf> {
152    None
153}
154
155/// This returns information about whether GCC should be built or if it's already built.
156/// It transparently handles downloading GCC from CI if needed.
157///
158/// It's used to avoid busting caches during x.py check -- if we've already built
159/// GCC, it's fine for us to not try to avoid doing so.
160pub fn get_gcc_build_status(builder: &Builder<'_>, target: TargetSelection) -> GccBuildStatus {
161    if let Some(path) = try_download_gcc(builder, target) {
162        return GccBuildStatus::AlreadyBuilt(path);
163    }
164
165    static STAMP_HASH_MEMO: OnceLock<String> = OnceLock::new();
166    let smart_stamp_hash = STAMP_HASH_MEMO.get_or_init(|| {
167        generate_smart_stamp_hash(
168            builder,
169            &builder.config.src.join("src/gcc"),
170            builder.in_tree_gcc_info.sha().unwrap_or_default(),
171        )
172    });
173
174    // Initialize the gcc submodule if not initialized already.
175    builder.config.update_submodule("src/gcc");
176
177    let root = builder.src.join("src/gcc");
178    let out_dir = builder.gcc_out(target).join("build");
179    let install_dir = builder.gcc_out(target).join("install");
180
181    let stamp = BuildStamp::new(&out_dir).with_prefix("gcc").add_stamp(smart_stamp_hash);
182
183    if stamp.is_up_to_date() {
184        if stamp.stamp().is_empty() {
185            builder.info(
186                "Could not determine the GCC submodule commit hash. \
187                     Assuming that an GCC rebuild is not necessary.",
188            );
189            builder.info(&format!(
190                "To force GCC to rebuild, remove the file `{}`",
191                stamp.path().display()
192            ));
193        }
194        let path = libgccjit_built_path(&install_dir);
195        if path.is_file() {
196            return GccBuildStatus::AlreadyBuilt(path);
197        } else {
198            builder.info(&format!(
199                "GCC stamp is up-to-date, but the libgccjit.so file was not found at `{}`",
200                path.display(),
201            ));
202        }
203    }
204
205    GccBuildStatus::ShouldBuild(Meta { stamp, out_dir, install_dir, root })
206}
207
208/// Returns the path to a libgccjit.so file in the install directory of GCC.
209fn libgccjit_built_path(install_dir: &Path) -> PathBuf {
210    install_dir.join("lib/libgccjit.so")
211}
212
213fn build_gcc(metadata: &Meta, builder: &Builder<'_>, target: TargetSelection) {
214    if builder.build.cc_tool(target).is_like_clang()
215        || builder.build.cxx_tool(target).is_like_clang()
216    {
217        panic!(
218            "Attempting to build GCC using Clang, which is known to misbehave. Please use GCC as the host C/C++ compiler. "
219        );
220    }
221
222    let Meta { stamp: _, out_dir, install_dir, root } = metadata;
223
224    t!(fs::create_dir_all(out_dir));
225    t!(fs::create_dir_all(install_dir));
226
227    // GCC creates files (e.g. symlinks to the downloaded dependencies)
228    // in the source directory, which does not work with our CI/Docker setup, where we mount
229    // source directories as read-only on Linux.
230    // And in general, we shouldn't be modifying the source directories if possible, even for local
231    // builds.
232    // Therefore, we first copy the whole source directory to the build directory, and perform the
233    // build from there.
234    let src_dir = builder.gcc_out(target).join("src");
235    if src_dir.exists() {
236        builder.remove_dir(&src_dir);
237    }
238    builder.create_dir(&src_dir);
239    builder.cp_link_r(root, &src_dir);
240
241    command(src_dir.join("contrib/download_prerequisites")).current_dir(&src_dir).run(builder);
242    let mut configure_cmd = command(src_dir.join("configure"));
243    configure_cmd
244        .current_dir(out_dir)
245        .arg("--enable-host-shared")
246        .arg("--enable-languages=c,jit,lto")
247        .arg("--enable-checking=release")
248        .arg("--disable-bootstrap")
249        .arg("--disable-multilib")
250        .arg(format!("--prefix={}", install_dir.display()));
251
252    let cc = builder.build.cc(target).display().to_string();
253    let cc = builder
254        .build
255        .config
256        .ccache
257        .as_ref()
258        .map_or_else(|| cc.clone(), |ccache| format!("{ccache} {cc}"));
259    configure_cmd.env("CC", cc);
260
261    if let Ok(ref cxx) = builder.build.cxx(target) {
262        let cxx = cxx.display().to_string();
263        let cxx = builder
264            .build
265            .config
266            .ccache
267            .as_ref()
268            .map_or_else(|| cxx.clone(), |ccache| format!("{ccache} {cxx}"));
269        configure_cmd.env("CXX", cxx);
270    }
271    configure_cmd.run(builder);
272
273    command("make")
274        .current_dir(out_dir)
275        .arg("--silent")
276        .arg(format!("-j{}", builder.jobs()))
277        .run_capture_stdout(builder);
278    command("make").current_dir(out_dir).arg("--silent").arg("install").run_capture_stdout(builder);
279}
280
281/// Configures a Cargo invocation so that it can build the GCC codegen backend.
282pub fn add_cg_gcc_cargo_flags(cargo: &mut Cargo, gcc: &GccOutput) {
283    // Add the path to libgccjit.so to the linker search paths.
284    cargo.rustflag(&format!("-L{}", gcc.libgccjit.parent().unwrap().to_str().unwrap()));
285}
286
287/// The absolute path to the downloaded GCC artifacts.
288#[cfg(not(test))]
289fn ci_gcc_root(config: &crate::Config, target: TargetSelection) -> PathBuf {
290    config.out.join(target).join("ci-gcc")
291}
292
293/// Detect whether GCC sources have been modified locally or not.
294#[cfg(not(test))]
295fn detect_gcc_freshness(config: &crate::Config, is_git: bool) -> build_helper::git::PathFreshness {
296    use build_helper::git::PathFreshness;
297
298    if is_git {
299        config.check_path_modifications(&["src/gcc", "src/bootstrap/download-ci-gcc-stamp"])
300    } else if let Some(info) = crate::utils::channel::read_commit_info_file(&config.src) {
301        PathFreshness::LastModifiedUpstream { upstream: info.sha.trim().to_owned() }
302    } else {
303        PathFreshness::MissingUpstream
304    }
305}
bootstrap/core/build_steps/gcc.rs

bootstrap/core/build_steps/
gcc.rs
