Clean code and move check for GCC backend build in dist.rs directly

Author: GuillaumeGomez

src/bootstrap/src/core/build_steps/dist.rs

@@ -2273,7 +2273,9 @@ impl Step for RustDev {
         tarball.permit_symlinks(true);
 
         builder.ensure(crate::core::build_steps::llvm::Llvm { target });
-        builder.ensure(crate::core::build_steps::gcc::Gcc { target });
+        if target.contains("linux") && target.contains("x86_64") {
+            builder.ensure(crate::core::build_steps::gcc::Gcc { target });
+        }
 
         let src_bindir = builder.llvm_out(target).join("bin");
         // If updating this, you likely want to change

src/bootstrap/src/core/build_steps/gcc.rs

@@ -35,15 +35,12 @@ pub enum GccBuildStatus {
 /// It's used to avoid busting caches during x.py check -- if we've already built
 /// GCC, it's fine for us to not try to avoid doing so.
 pub fn prebuilt_gcc_config(builder: &Builder<'_>, target: TargetSelection) -> GccBuildStatus {
-    // If we have gcc submodule initialized already, sync it.
-    builder.update_existing_submodule("src/gcc");
+    // Initialize the gcc submodule if not initialized already.
+    builder.update_submodule("src/gcc");
 
     // FIXME (GuillaumeGomez): To be done once gccjit has been built in the CI.
     // builder.config.maybe_download_ci_gcc();
 
-    // Initialize the gcc submodule if not initialized already.
-    builder.update_submodule("src/gcc");
-
     let root = "src/gcc";
     let out_dir = builder.gcc_out(target).join("build");
     let install_dir = builder.gcc_out(target).join("install");
@@ -77,84 +74,6 @@ pub fn prebuilt_gcc_config(builder: &Builder<'_>, target: TargetSelection) -> Gc
     GccBuildStatus::ShouldBuild(Meta { stamp, out_dir, install_dir, root: root.into() })
 }
 
-// FIXME (GuillaumeGomez): When gcc-ci-download option is added, uncomment this code.
-// /// This retrieves the GCC sha we *want* to use, according to git history.
-// pub(crate) fn detect_gcc_sha(config: &Config, is_git: bool) -> String {
-//     let gcc_sha = if is_git {
-//         // We proceed in 2 steps. First we get the closest commit that is actually upstream. Then we
-//         // walk back further to the last bors merge commit that actually changed GCC. The first
-//         // step will fail on CI because only the `auto` branch exists; we just fall back to `HEAD`
-//         // in that case.
-//         let closest_upstream = get_git_merge_base(&config.git_config(), Some(&config.src))
-//             .unwrap_or_else(|_| "HEAD".into());
-//         let mut rev_list = config.git();
-//         rev_list.args(&[
-//             PathBuf::from("rev-list"),
-//             format!("--author={}", config.stage0_metadata.config.git_merge_commit_email).into(),
-//             "-n1".into(),
-//             "--first-parent".into(),
-//             closest_upstream.into(),
-//             "--".into(),
-//             config.src.join("src/gcc"),
-//             config.src.join("src/bootstrap/download-ci-gcc-stamp"),
-//             // the GCC shared object file is named `gcc-12-rust-{version}-nightly`
-//             config.src.join("src/version"),
-//         ]);
-//         output(&mut rev_list).trim().to_owned()
-//     } else if let Some(info) = channel::read_commit_info_file(&config.src) {
-//         info.sha.trim().to_owned()
-//     } else {
-//         "".to_owned()
-//     };
-
-//     if gcc_sha.is_empty() {
-//         eprintln!("error: could not find commit hash for downloading GCC");
-//         eprintln!("HELP: maybe your repository history is too shallow?");
-//         eprintln!("HELP: consider disabling `download-ci-gcc`");
-//         eprintln!("HELP: or fetch enough history to include one upstream commit");
-//         panic!();
-//     }
-
-//     gcc_sha
-// }
-
-// /// Returns whether the CI-found GCC is currently usable.
-// ///
-// /// This checks both the build triple platform to confirm we're usable at all,
-// /// and then verifies if the current HEAD matches the detected GCC SHA head,
-// /// in which case GCC is indicated as not available.
-// pub(crate) fn is_ci_gcc_available(config: &Config, asserts: bool) -> bool {
-//     let supported_platforms = [
-//         // tier 1
-//         ("x86_64-unknown-linux-gnu", true),
-//     ];
-
-//     if !supported_platforms.contains(&(&*config.build.triple, asserts))
-//         && (asserts || !supported_platforms.contains(&(&*config.build.triple, true)))
-//     {
-//         return false;
-//     }
-
-//     if is_ci_gcc_modified(config) {
-//         eprintln!("Detected GCC as non-available: running in CI and modified GCC in this change");
-//         return false;
-//     }
-
-//     true
-// }
-
-// /// Returns true if we're running in CI with modified GCC (and thus can't download it)
-// pub(crate) fn is_ci_gcc_modified(config: &Config) -> bool {
-//     CiEnv::is_ci() && config.rust_info.is_managed_git_subrepository() && {
-//         // We assume we have access to git, so it's okay to unconditionally pass
-//         // `true` here.
-//         let gcc_sha = detect_gcc_sha(config, true);
-//         let head_sha = output(config.git().arg("rev-parse").arg("HEAD"));
-//         let head_sha = head_sha.trim();
-//         gcc_sha == head_sha
-//     }
-// }
-
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct Gcc {
     pub target: TargetSelection,
@@ -176,12 +95,8 @@ impl Step for Gcc {
     /// Compile GCC for `target`.
     fn run(self, builder: &Builder<'_>) -> bool {
         let target = self.target;
-        if !target.contains("linux") || !target.contains("x86_64") {
-            return false;
-        }
 
-        // If GCC has already been built or been downloaded through download-ci-gcc, we avoid
-        // building it again.
+        // If GCC has already been built, we avoid building it again.
         let Meta { stamp, out_dir, install_dir, root } = match prebuilt_gcc_config(builder, target)
         {
             GccBuildStatus::AlreadyBuilt => return true,