bootstrap/core/build_steps/
gcc.rs

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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::core::builder::{Builder, Cargo, Kind, RunConfig, ShouldRun, Step};
16use crate::core::config::TargetSelection;
17use crate::utils::build_stamp::{BuildStamp, generate_smart_stamp_hash};
18use crate::utils::exec::command;
19use crate::utils::helpers::{self, t};
20
21#[derive(Debug, Clone, Hash, PartialEq, Eq)]
22pub struct Gcc {
23    pub target: TargetSelection,
24}
25
26#[derive(Clone)]
27pub struct GccOutput {
28    pub libgccjit: PathBuf,
29}
30
31impl Step for Gcc {
32    type Output = GccOutput;
33
34    const ONLY_HOSTS: bool = true;
35
36    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
37        run.path("src/gcc").alias("gcc")
38    }
39
40    fn make_run(run: RunConfig<'_>) {
41        run.builder.ensure(Gcc { target: run.target });
42    }
43
44    /// Compile GCC (specifically `libgccjit`) for `target`.
45    fn run(self, builder: &Builder<'_>) -> Self::Output {
46        let target = self.target;
47
48        // If GCC has already been built, we avoid building it again.
49        let metadata = match get_gcc_build_status(builder, target) {
50            GccBuildStatus::AlreadyBuilt(path) => return GccOutput { libgccjit: path },
51            GccBuildStatus::ShouldBuild(m) => m,
52        };
53
54        let _guard = builder.msg_unstaged(Kind::Build, "GCC", target);
55        t!(metadata.stamp.remove());
56        let _time = helpers::timeit(builder);
57
58        let libgccjit_path = libgccjit_built_path(&metadata.install_dir);
59        if builder.config.dry_run() {
60            return GccOutput { libgccjit: libgccjit_path };
61        }
62
63        build_gcc(&metadata, builder, target);
64        create_lib_alias(builder, &libgccjit_path);
65
66        t!(metadata.stamp.write());
67
68        GccOutput { libgccjit: libgccjit_path }
69    }
70}
71
72/// Creates a libgccjit.so.0 alias next to libgccjit.so if it does not
73/// already exist
74fn create_lib_alias(builder: &Builder<'_>, libgccjit: &PathBuf) {
75    let lib_alias = libgccjit.parent().unwrap().join("libgccjit.so.0");
76    if !lib_alias.exists() {
77        t!(builder.symlink_file(libgccjit, lib_alias));
78    }
79}
80
81pub struct Meta {
82    stamp: BuildStamp,
83    out_dir: PathBuf,
84    install_dir: PathBuf,
85    root: PathBuf,
86}
87
88pub enum GccBuildStatus {
89    /// libgccjit is already built at this path
90    AlreadyBuilt(PathBuf),
91    ShouldBuild(Meta),
92}
93
94/// Tries to download GCC from CI if it is enabled and GCC artifacts
95/// are available for the given target.
96/// Returns a path to the libgccjit.so file.
97#[cfg(not(test))]
98fn try_download_gcc(builder: &Builder<'_>, target: TargetSelection) -> Option<PathBuf> {
99    // Try to download GCC from CI if configured and available
100    if !matches!(builder.config.gcc_ci_mode, crate::core::config::GccCiMode::DownloadFromCi) {
101        return None;
102    }
103    if target != "x86_64-unknown-linux-gnu" {
104        eprintln!("GCC CI download is only available for the `x86_64-unknown-linux-gnu` target");
105        return None;
106    }
107    let sha =
108        detect_gcc_sha(&builder.config, builder.config.rust_info.is_managed_git_subrepository());
109    let root = ci_gcc_root(&builder.config);
110    let gcc_stamp = BuildStamp::new(&root).with_prefix("gcc").add_stamp(&sha);
111    if !gcc_stamp.is_up_to_date() && !builder.config.dry_run() {
112        builder.config.download_ci_gcc(&sha, &root);
113        t!(gcc_stamp.write());
114    }
115
116    let libgccjit = root.join("lib").join("libgccjit.so");
117    create_lib_alias(builder, &libgccjit);
118    Some(libgccjit)
119}
120
121#[cfg(test)]
122fn try_download_gcc(_builder: &Builder<'_>, _target: TargetSelection) -> Option<PathBuf> {
123    None
124}
125
126/// This returns information about whether GCC should be built or if it's already built.
127/// It transparently handles downloading GCC from CI if needed.
128///
129/// It's used to avoid busting caches during x.py check -- if we've already built
130/// GCC, it's fine for us to not try to avoid doing so.
131pub fn get_gcc_build_status(builder: &Builder<'_>, target: TargetSelection) -> GccBuildStatus {
132    if let Some(path) = try_download_gcc(builder, target) {
133        return GccBuildStatus::AlreadyBuilt(path);
134    }
135
136    static STAMP_HASH_MEMO: OnceLock<String> = OnceLock::new();
137    let smart_stamp_hash = STAMP_HASH_MEMO.get_or_init(|| {
138        generate_smart_stamp_hash(
139            builder,
140            &builder.config.src.join("src/gcc"),
141            builder.in_tree_gcc_info.sha().unwrap_or_default(),
142        )
143    });
144
145    // Initialize the gcc submodule if not initialized already.
146    builder.config.update_submodule("src/gcc");
147
148    let root = builder.src.join("src/gcc");
149    let out_dir = builder.gcc_out(target).join("build");
150    let install_dir = builder.gcc_out(target).join("install");
151
152    let stamp = BuildStamp::new(&out_dir).with_prefix("gcc").add_stamp(smart_stamp_hash);
153
154    if stamp.is_up_to_date() {
155        if stamp.stamp().is_empty() {
156            builder.info(
157                "Could not determine the GCC submodule commit hash. \
158                     Assuming that an GCC rebuild is not necessary.",
159            );
160            builder.info(&format!(
161                "To force GCC to rebuild, remove the file `{}`",
162                stamp.path().display()
163            ));
164        }
165        let path = libgccjit_built_path(&install_dir);
166        if path.is_file() {
167            return GccBuildStatus::AlreadyBuilt(path);
168        } else {
169            builder.info(&format!(
170                "GCC stamp is up-to-date, but the libgccjit.so file was not found at `{}`",
171                path.display(),
172            ));
173        }
174    }
175
176    GccBuildStatus::ShouldBuild(Meta { stamp, out_dir, install_dir, root })
177}
178
179/// Returns the path to a libgccjit.so file in the install directory of GCC.
180fn libgccjit_built_path(install_dir: &Path) -> PathBuf {
181    install_dir.join("lib/libgccjit.so")
182}
183
184fn build_gcc(metadata: &Meta, builder: &Builder<'_>, target: TargetSelection) {
185    if builder.build.cc_tool(target).is_like_clang()
186        || builder.build.cxx_tool(target).is_like_clang()
187    {
188        panic!(
189            "Attempting to build GCC using Clang, which is known to misbehave. Please use GCC as the host C/C++ compiler. "
190        );
191    }
192
193    let Meta { stamp: _, out_dir, install_dir, root } = metadata;
194
195    t!(fs::create_dir_all(out_dir));
196    t!(fs::create_dir_all(install_dir));
197
198    // GCC creates files (e.g. symlinks to the downloaded dependencies)
199    // in the source directory, which does not work with our CI setup, where we mount
200    // source directories as read-only on Linux.
201    // Therefore, as a part of the build in CI, we first copy the whole source directory
202    // to the build directory, and perform the build from there.
203    let src_dir = if builder.config.is_running_on_ci {
204        let src_dir = builder.gcc_out(target).join("src");
205        if src_dir.exists() {
206            builder.remove_dir(&src_dir);
207        }
208        builder.create_dir(&src_dir);
209        builder.cp_link_r(root, &src_dir);
210        src_dir
211    } else {
212        root.clone()
213    };
214
215    command(src_dir.join("contrib/download_prerequisites")).current_dir(&src_dir).run(builder);
216    let mut configure_cmd = command(src_dir.join("configure"));
217    configure_cmd
218        .current_dir(out_dir)
219        .arg("--enable-host-shared")
220        .arg("--enable-languages=c,jit,lto")
221        .arg("--enable-checking=release")
222        .arg("--disable-bootstrap")
223        .arg("--disable-multilib")
224        .arg(format!("--prefix={}", install_dir.display()));
225
226    let cc = builder.build.cc(target).display().to_string();
227    let cc = builder
228        .build
229        .config
230        .ccache
231        .as_ref()
232        .map_or_else(|| cc.clone(), |ccache| format!("{ccache} {cc}"));
233    configure_cmd.env("CC", cc);
234
235    if let Ok(ref cxx) = builder.build.cxx(target) {
236        let cxx = cxx.display().to_string();
237        let cxx = builder
238            .build
239            .config
240            .ccache
241            .as_ref()
242            .map_or_else(|| cxx.clone(), |ccache| format!("{ccache} {cxx}"));
243        configure_cmd.env("CXX", cxx);
244    }
245    configure_cmd.run(builder);
246
247    command("make")
248        .current_dir(out_dir)
249        .arg("--silent")
250        .arg(format!("-j{}", builder.jobs()))
251        .run_capture_stdout(builder);
252    command("make").current_dir(out_dir).arg("--silent").arg("install").run_capture_stdout(builder);
253}
254
255/// Configures a Cargo invocation so that it can build the GCC codegen backend.
256pub fn add_cg_gcc_cargo_flags(cargo: &mut Cargo, gcc: &GccOutput) {
257    // Add the path to libgccjit.so to the linker search paths.
258    cargo.rustflag(&format!("-L{}", gcc.libgccjit.parent().unwrap().to_str().unwrap()));
259}
260
261/// The absolute path to the downloaded GCC artifacts.
262#[cfg(not(test))]
263fn ci_gcc_root(config: &crate::Config) -> PathBuf {
264    config.out.join(config.build).join("ci-gcc")
265}
266
267/// This retrieves the GCC sha we *want* to use, according to git history.
268#[cfg(not(test))]
269fn detect_gcc_sha(config: &crate::Config, is_git: bool) -> String {
270    use build_helper::git::get_closest_merge_commit;
271
272    let gcc_sha = if is_git {
273        get_closest_merge_commit(
274            Some(&config.src),
275            &config.git_config(),
276            &["src/gcc", "src/bootstrap/download-ci-gcc-stamp"],
277        )
278        .unwrap()
279    } else if let Some(info) = crate::utils::channel::read_commit_info_file(&config.src) {
280        info.sha.trim().to_owned()
281    } else {
282        "".to_owned()
283    };
284
285    if gcc_sha.is_empty() {
286        eprintln!("error: could not find commit hash for downloading GCC");
287        eprintln!("HELP: maybe your repository history is too shallow?");
288        eprintln!("HELP: consider disabling `download-ci-gcc`");
289        eprintln!("HELP: or fetch enough history to include one upstream commit");
290        panic!();
291    }
292
293    gcc_sha
294}
bootstrap/core/build_steps/gcc.rs

bootstrap/core/build_steps/
gcc.rs
