Rollup merge of rust-lang#85647 - rust-lang:revert-81601-llvm-on-demand, r=jyn514

Revert "Move llvm submodule updates to rustbuild"

Reverts rust-lang#81601

This updates LLVM a bit too eagerly -- and particularly on Windows, this can be slow. See discussion on [Zulip].

[Zulip]: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/x.2Epy.20always.20updates.20LLVM.20submodule

Author: JohnTitor

src/bootstrap/bootstrap.py

@@ -991,20 +991,28 @@ def update_submodules(self):
         ).decode(default_encoding).splitlines()]
         filtered_submodules = []
         submodules_names = []
+        llvm_checked_out = os.path.exists(os.path.join(self.rust_root, "src/llvm-project/.git"))
+        external_llvm_provided = self.get_toml('llvm-config') or self.downloading_llvm()
+        llvm_needed = not self.get_toml('codegen-backends', 'rust') \
+            or "llvm" in self.get_toml('codegen-backends', 'rust')
         for module in submodules:
-            # This is handled by native::Llvm in rustbuild, not here
             if module.endswith("llvm-project"):
-                continue
+                # Don't sync the llvm-project submodule if an external LLVM was
+                # provided, if we are downloading LLVM or if the LLVM backend is
+                # not being built. Also, if the submodule has been initialized
+                # already, sync it anyways so that it doesn't mess up contributor
+                # pull requests.
+                if external_llvm_provided or not llvm_needed:
+                    if self.get_toml('lld') != 'true' and not llvm_checked_out:
+                        continue
             check = self.check_submodule(module, slow_submodules)
             filtered_submodules.append((module, check))
             submodules_names.append(module)
         recorded = subprocess.Popen(["git", "ls-tree", "HEAD"] + submodules_names,
                                     cwd=self.rust_root, stdout=subprocess.PIPE)
         recorded = recorded.communicate()[0].decode(default_encoding).strip().splitlines()
-        # { filename: hash }
         recorded_submodules = {}
         for data in recorded:
-            # [mode, kind, hash, filename]
             data = data.split()
             recorded_submodules[data[3]] = data[2]
         for module in filtered_submodules:

src/bootstrap/lib.rs

@@ -472,22 +472,12 @@ impl Build {
         slice::from_ref(&self.build.triple)
     }
 
-    /// If the LLVM submodule has been initialized already, sync it unconditionally. This avoids
-    /// contributors checking in a submodule change by accident.
-    pub fn maybe_update_llvm_submodule(&self) {
-        if self.in_tree_llvm_info.is_git() {
-            native::update_llvm_submodule(self);
-        }
-    }
-
     /// Executes the entire build, as configured by the flags and configuration.
     pub fn build(&mut self) {
         unsafe {
             job::setup(self);
         }
 
-        self.maybe_update_llvm_submodule();
-
         if let Subcommand::Format { check, paths } = &self.config.cmd {
             return format::format(self, *check, &paths);
         }

src/bootstrap/native.rs

@@ -21,7 +21,7 @@ use build_helper::{output, t};
 use crate::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::config::TargetSelection;
 use crate::util::{self, exe};
-use crate::{Build, GitRepo};
+use crate::GitRepo;
 use build_helper::up_to_date;
 
 pub struct Meta {
@@ -91,85 +91,6 @@ pub fn prebuilt_llvm_config(
     Err(Meta { stamp, build_llvm_config, out_dir, root: root.into() })
 }
 
-// modified from `check_submodule` and `update_submodule` in bootstrap.py
-pub(crate) fn update_llvm_submodule(build: &Build) {
-    let llvm_project = &Path::new("src").join("llvm-project");
-
-    fn dir_is_empty(dir: &Path) -> bool {
-        t!(std::fs::read_dir(dir)).next().is_none()
-    }
-
-    // NOTE: The check for the empty directory is here because when running x.py
-    // the first time, the llvm submodule won't be checked out. Check it out
-    // now so we can build it.
-    if !build.in_tree_llvm_info.is_git() && !dir_is_empty(&build.config.src.join(llvm_project)) {
-        return;
-    }
-
-    // check_submodule
-    let checked_out = if build.config.fast_submodules {
-        Some(output(
-            Command::new("git")
-                .args(&["rev-parse", "HEAD"])
-                .current_dir(build.config.src.join(llvm_project)),
-        ))
-    } else {
-        None
-    };
-
-    // update_submodules
-    let recorded = output(
-        Command::new("git")
-            .args(&["ls-tree", "HEAD"])
-            .arg(llvm_project)
-            .current_dir(&build.config.src),
-    );
-    let hash =
-        recorded.split(' ').nth(2).unwrap_or_else(|| panic!("unexpected output `{}`", recorded));
-
-    // update_submodule
-    if let Some(llvm_hash) = checked_out {
-        if hash == llvm_hash {
-            // already checked out
-            return;
-        }
-    }
-
-    println!("Updating submodule {}", llvm_project.display());
-    build.run(
-        Command::new("git")
-            .args(&["submodule", "-q", "sync"])
-            .arg(llvm_project)
-            .current_dir(&build.config.src),
-    );
-
-    // Try passing `--progress` to start, then run git again without if that fails.
-    let update = |progress: bool| {
-        let mut git = Command::new("git");
-        git.args(&["submodule", "update", "--init", "--recursive"]);
-        if progress {
-            git.arg("--progress");
-        }
-        git.arg(llvm_project).current_dir(&build.config.src);
-        git
-    };
-    // NOTE: doesn't use `try_run` because this shouldn't print an error if it fails.
-    if !update(true).status().map_or(false, |status| status.success()) {
-        build.run(&mut update(false));
-    }
-
-    build.run(
-        Command::new("git")
-            .args(&["reset", "-q", "--hard"])
-            .current_dir(build.config.src.join(llvm_project)),
-    );
-    build.run(
-        Command::new("git")
-            .args(&["clean", "-qdfx"])
-            .current_dir(build.config.src.join(llvm_project)),
-    );
-}
-
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct Llvm {
     pub target: TargetSelection,
@@ -207,9 +128,6 @@ impl Step for Llvm {
                 Err(m) => m,
             };
 
-        if !builder.config.dry_run {
-            update_llvm_submodule(builder);
-        }
         if builder.config.llvm_link_shared
             && (target.contains("windows") || target.contains("apple-darwin"))
         {

src/build_helper/lib.rs

@@ -130,7 +130,6 @@ pub fn make(host: &str) -> PathBuf {
     }
 }
 
-#[track_caller]
 pub fn output(cmd: &mut Command) -> String {
     let output = match cmd.stderr(Stdio::inherit()).output() {
         Ok(status) => status,