Auto merge of rust-lang#131455 - onur-ozkan:debug, r=<try>

debug

**DO NOT MERGE**

try-build: aarch64-apple

compiler/rustc_serialize/src/serialize.rs

@@ -325,7 +325,7 @@ impl<D: Decoder, const N: usize> Decodable<D> for [u8; N] {
     }
 }
 
-impl<'a, S: Encoder, T: Encodable<S>> Encodable<S> for Cow<'a, [T]>
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Cow<'_, [T]>
 where
     [T]: ToOwned<Owned = Vec<T>>,
 {
@@ -345,14 +345,14 @@ where
     }
 }
 
-impl<'a, S: Encoder> Encodable<S> for Cow<'a, str> {
+impl<S: Encoder> Encodable<S> for Cow<'_, str> {
     fn encode(&self, s: &mut S) {
         let val: &str = self;
         val.encode(s)
     }
 }
 
-impl<'a, D: Decoder> Decodable<D> for Cow<'a, str> {
+impl<D: Decoder> Decodable<D> for Cow<'_, str> {
     fn decode(d: &mut D) -> Cow<'static, str> {
         let v: String = Decodable::decode(d);
         Cow::Owned(v)

src/bootstrap/src/core/build_steps/llvm.rs

@@ -20,10 +20,9 @@ use build_helper::git::get_closest_merge_commit;
 
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::core::config::{Config, TargetSelection};
-use crate::utils::channel;
 use crate::utils::exec::command;
 use crate::utils::helpers::{
-    self, HashStamp, exe, get_clang_cl_resource_dir, output, t, unhashed_basename, up_to_date,
+    self, HashStamp, exe, get_clang_cl_resource_dir, t, unhashed_basename, up_to_date,
 };
 use crate::{CLang, GitRepo, Kind, generate_smart_stamp_hash};
 
@@ -157,6 +156,7 @@ pub fn prebuilt_llvm_config(
 }
 
 /// This retrieves the LLVM sha we *want* to use, according to git history.
+#[cfg(not(feature = "bootstrap-self-test"))]
 pub(crate) fn detect_llvm_sha(config: &Config, is_git: bool) -> String {
     let llvm_sha = if is_git {
         get_closest_merge_commit(Some(&config.src), &config.git_config(), &[
@@ -166,7 +166,7 @@ pub(crate) fn detect_llvm_sha(config: &Config, is_git: bool) -> String {
             config.src.join("src/version"),
         ])
         .unwrap()
-    } else if let Some(info) = channel::read_commit_info_file(&config.src) {
+    } else if let Some(info) = crate::utils::channel::read_commit_info_file(&config.src) {
         info.sha.trim().to_owned()
     } else {
         "".to_owned()
@@ -242,15 +242,40 @@ pub(crate) fn is_ci_llvm_available(config: &Config, asserts: bool) -> bool {
 
 /// Returns true if we're running in CI with modified LLVM (and thus can't download it)
 pub(crate) fn is_ci_llvm_modified(config: &Config) -> bool {
-    CiEnv::is_rust_lang_managed_ci_job() && config.rust_info.is_managed_git_subrepository() && {
-        // We assume we have access to git, so it's okay to unconditionally pass
-        // `true` here.
-        let llvm_sha = detect_llvm_sha(config, true);
-        let head_sha =
-            output(helpers::git(Some(&config.src)).arg("rev-parse").arg("HEAD").as_command_mut());
-        let head_sha = head_sha.trim();
-        llvm_sha == head_sha
+    // If not running in a CI environment, return false.
+    if !CiEnv::is_ci() {
+        return false;
+    }
+
+    // In rust-lang/rust managed CI, assert the existence of the LLVM submodule.
+    if CiEnv::is_rust_lang_managed_ci_job() {
+        assert!(
+            config.in_tree_llvm_info.is_managed_git_subrepository(),
+            "LLVM submodule must be fetched in rust-lang/rust managed CI builders."
+        );
     }
+    // If LLVM submodule isn't present, skip the change check as it won't work.
+    else if !config.in_tree_llvm_info.is_managed_git_subrepository() {
+        return false;
+    }
+
+    let commit = t!(get_closest_merge_commit(Some(&config.src), &config.git_config(), &[]));
+
+    #[allow(clippy::let_and_return)] // makes it look more clear
+    let is_modified = !t!(helpers::git(Some(&config.src))
+        .args(["diff-index", "--quiet", &commit])
+        .arg("--")
+        .args([
+            config.src.join("src/llvm-project"),
+            config.src.join("src/bootstrap/download-ci-llvm-stamp"),
+            // the LLVM shared object file is named `LLVM-12-rust-{version}-nightly`
+            config.src.join("src/version"),
+        ])
+        .as_command_mut()
+        .status())
+    .success();
+
+    is_modified
 }
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]

src/bootstrap/src/core/builder/tests.rs

@@ -216,6 +216,12 @@ fn alias_and_path_for_library() {
 
 #[test]
 fn ci_rustc_if_unchanged_logic() {
+    if env::var_os("NO_DOWNLOAD_CI_RUSTC").is_some_and(|s| s == "1" || s == "true") {
+        // FIXME: Find the actual reason.
+        println!("This test is incompatible in runners configured with `NO_DOWNLOAD_CI_RUSTC`.");
+        return;
+    }
+
     let config = Config::parse_inner(
         Flags::parse(&[
             "build".to_owned(),

src/bootstrap/src/core/config/config.rs

@@ -2399,6 +2399,13 @@ impl Config {
                 Some(commit) => {
                     self.download_ci_rustc(commit);
 
+                    // We never enable `download-rustc` without `download-ci-llvm`. If `self.llvm_from_ci` is false,
+                    // it means the "if-unchanged" logic has detected some changes in the LLVM submodule.
+                    if CiEnv::is_ci() && !self.llvm_from_ci {
+                        println!("WARNING: LLVM submodule has changes, `download-rustc` will be disabled.");
+                        return None;
+                    }
+
                     if let Some(config_path) = &self.config {
                         let ci_config_toml = match self.get_builder_toml("ci-rustc") {
                             Ok(ci_config_toml) => ci_config_toml,