Merge pull request #4034 from rust-lang/rustup-2024-11-15

Automatic Rustup

16 files changed, 269 insertions, 75 deletions

diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index ba505089a00..7950f1004a2 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -40,7 +40,7 @@ test = false
 cc = "=1.1.22"
 cmake = "=0.1.48"
 
-build_helper = { path = "../tools/build_helper" }
+build_helper = { path = "../build_helper" }
 clap = { version = "4.4", default-features = false, features = ["std", "usage", "help", "derive", "error-context"] }
 clap_complete = "4.4"
 fd-lock = "4.0"
diff --git a/src/bootstrap/bootstrap_test.py b/src/bootstrap/bootstrap_test.py
index 706f2c5bf07..70ed12b96e8 100644
--- a/src/bootstrap/bootstrap_test.py
+++ b/src/bootstrap/bootstrap_test.py
@@ -5,6 +5,7 @@ Run these with `x test bootstrap`, or `python -m unittest src/bootstrap/bootstra
 from __future__ import absolute_import, division, print_function
 import os
 import unittest
+from unittest.mock import patch
 import tempfile
 import hashlib
 import sys
@@ -99,6 +100,52 @@ class ProgramOutOfDate(unittest.TestCase):
         self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
 
+class ParseArgsInConfigure(unittest.TestCase):
+    """Test if `parse_args` function in `configure.py` works properly"""
+    @patch("configure.err")
+    def test_unknown_args(self, err):
+        # It should be print an error message if the argument doesn't start with '--'
+        configure.parse_args(["enable-full-tools"])
+        err.assert_called_with("Option 'enable-full-tools' is not recognized")
+        err.reset_mock()
+        # It should be print an error message if the argument is not recognized
+        configure.parse_args(["--some-random-flag"])
+        err.assert_called_with("Option '--some-random-flag' is not recognized")
+
+    @patch("configure.err")
+    def test_need_value_args(self, err):
+        """It should print an error message if a required argument value is missing"""
+        configure.parse_args(["--target"])
+        err.assert_called_with("Option '--target' needs a value (--target=val)")
+
+    @patch("configure.err")
+    def test_option_checking(self, err):
+        # Options should be checked even if `--enable-option-checking` is not passed
+        configure.parse_args(["--target"])
+        err.assert_called_with("Option '--target' needs a value (--target=val)")
+        err.reset_mock()
+        # Options should be checked if `--enable-option-checking` is passed
+        configure.parse_args(["--enable-option-checking", "--target"])
+        err.assert_called_with("Option '--target' needs a value (--target=val)")
+        err.reset_mock()
+        # Options should not be checked if `--disable-option-checking` is passed
+        configure.parse_args(["--disable-option-checking", "--target"])
+        err.assert_not_called()
+
+    @patch("configure.parse_example_config", lambda known_args, _: known_args)
+    def test_known_args(self):
+        # It should contain known and correct arguments
+        known_args = configure.parse_args(["--enable-full-tools"])
+        self.assertTrue(known_args["full-tools"][0][1])
+        known_args = configure.parse_args(["--disable-full-tools"])
+        self.assertFalse(known_args["full-tools"][0][1])
+        # It should contain known arguments and their values
+        known_args = configure.parse_args(["--target=x86_64-unknown-linux-gnu"])
+        self.assertEqual(known_args["target"][0][1], "x86_64-unknown-linux-gnu")
+        known_args = configure.parse_args(["--target", "x86_64-unknown-linux-gnu"])
+        self.assertEqual(known_args["target"][0][1], "x86_64-unknown-linux-gnu")
+
+
 class GenerateAndParseConfig(unittest.TestCase):
     """Test that we can serialize and deserialize a config.toml file"""
     def test_no_args(self):
diff --git a/src/bootstrap/defaults/config.compiler.toml b/src/bootstrap/defaults/config.compiler.toml
index 147939d2047..57a0ca5a718 100644
--- a/src/bootstrap/defaults/config.compiler.toml
+++ b/src/bootstrap/defaults/config.compiler.toml
@@ -19,6 +19,7 @@ lto = "off"
 # Forces frame pointers to be used with `-Cforce-frame-pointers`.
 # This can be helpful for profiling at a small performance cost.
 frame-pointers = true
+download-rustc = false
 
 [llvm]
 # Having this set to true disrupts compiler development workflows for people who use `llvm.download-ci-llvm = true`
diff --git a/src/bootstrap/defaults/config.library.toml b/src/bootstrap/defaults/config.library.toml
index 5447565a4b0..67ceb220524 100644
--- a/src/bootstrap/defaults/config.library.toml
+++ b/src/bootstrap/defaults/config.library.toml
@@ -10,6 +10,7 @@ bench-stage = 0
 incremental = true
 # Make the compiler and standard library faster to build, at the expense of a ~20% runtime slowdown.
 lto = "off"
+download-rustc = false
 
 [llvm]
 # Will download LLVM from CI if available on your platform.
diff --git a/src/bootstrap/src/core/build_steps/clean.rs b/src/bootstrap/src/core/build_steps/clean.rs
index 040690623a1..d857de96cce 100644
--- a/src/bootstrap/src/core/build_steps/clean.rs
+++ b/src/bootstrap/src/core/build_steps/clean.rs
@@ -226,6 +226,8 @@ where
         Err(ref e) if e.kind() == ErrorKind::PermissionDenied => {
             let m = t!(path.symlink_metadata());
             let mut p = m.permissions();
+            // this os not unix, so clippy gives FP
+            #[expect(clippy::permissions_set_readonly_false)]
             p.set_readonly(false);
             t!(fs::set_permissions(path, p));
             f(path).unwrap_or_else(|e| {
diff --git a/src/bootstrap/src/core/build_steps/clippy.rs b/src/bootstrap/src/core/build_steps/clippy.rs
index cd198c425c0..0884d86cc6d 100644
--- a/src/bootstrap/src/core/build_steps/clippy.rs
+++ b/src/bootstrap/src/core/build_steps/clippy.rs
@@ -20,14 +20,12 @@ const IGNORED_RULES_FOR_STD_AND_RUSTC: &[&str] = &[
     "wrong_self_convention",
 ];
 
-fn lint_args(builder: &Builder<'_>, ignored_rules: &[&str]) -> Vec<String> {
+fn lint_args(builder: &Builder<'_>, config: &LintConfig, ignored_rules: &[&str]) -> Vec<String> {
     fn strings<'a>(arr: &'a [&str]) -> impl Iterator<Item = String> + 'a {
         arr.iter().copied().map(String::from)
     }
 
-    let Subcommand::Clippy { fix, allow_dirty, allow_staged, allow, deny, warn, forbid } =
-        &builder.config.cmd
-    else {
+    let Subcommand::Clippy { fix, allow_dirty, allow_staged, .. } = &builder.config.cmd else {
         unreachable!("clippy::lint_args can only be called from `clippy` subcommands.");
     };
 
@@ -53,12 +51,12 @@ fn lint_args(builder: &Builder<'_>, ignored_rules: &[&str]) -> Vec<String> {
 
     args.extend(strings(&["--"]));
 
-    if deny.is_empty() && forbid.is_empty() {
+    if config.deny.is_empty() && config.forbid.is_empty() {
         args.extend(strings(&["--cap-lints", "warn"]));
     }
 
     let all_args = std::env::args().collect::<Vec<_>>();
-    args.extend(get_clippy_rules_in_order(&all_args, allow, deny, warn, forbid));
+    args.extend(get_clippy_rules_in_order(&all_args, config));
 
     args.extend(ignored_rules.iter().map(|lint| format!("-Aclippy::{}", lint)));
     args.extend(builder.config.free_args.clone());
@@ -68,21 +66,17 @@ fn lint_args(builder: &Builder<'_>, ignored_rules: &[&str]) -> Vec<String> {
 /// We need to keep the order of the given clippy lint rules before passing them.
 /// Since clap doesn't offer any useful interface for this purpose out of the box,
 /// we have to handle it manually.
-pub(crate) fn get_clippy_rules_in_order(
-    all_args: &[String],
-    allow_rules: &[String],
-    deny_rules: &[String],
-    warn_rules: &[String],
-    forbid_rules: &[String],
-) -> Vec<String> {
+pub fn get_clippy_rules_in_order(all_args: &[String], config: &LintConfig) -> Vec<String> {
     let mut result = vec![];
 
     for (prefix, item) in
-        [("-A", allow_rules), ("-D", deny_rules), ("-W", warn_rules), ("-F", forbid_rules)]
+        [("-A", &config.allow), ("-D", &config.deny), ("-W", &config.warn), ("-F", &config.forbid)]
     {
         item.iter().for_each(|v| {
             let rule = format!("{prefix}{v}");
-            let position = all_args.iter().position(|t| t == &rule).unwrap();
+            // Arguments added by bootstrap in LintConfig won't show up in the all_args list, so
+            // put them at the end of the command line.
+            let position = all_args.iter().position(|t| t == &rule || t == v).unwrap_or(usize::MAX);
             result.push((position, rule));
         });
     }
@@ -92,8 +86,41 @@ pub(crate) fn get_clippy_rules_in_order(
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct LintConfig {
+    pub allow: Vec<String>,
+    pub warn: Vec<String>,
+    pub deny: Vec<String>,
+    pub forbid: Vec<String>,
+}
+
+impl LintConfig {
+    fn new(builder: &Builder<'_>) -> Self {
+        match builder.config.cmd.clone() {
+            Subcommand::Clippy { allow, deny, warn, forbid, .. } => {
+                Self { allow, warn, deny, forbid }
+            }
+            _ => unreachable!("LintConfig can only be called from `clippy` subcommands."),
+        }
+    }
+
+    fn merge(&self, other: &Self) -> Self {
+        let merged = |self_attr: &[String], other_attr: &[String]| -> Vec<String> {
+            self_attr.iter().cloned().chain(other_attr.iter().cloned()).collect()
+        };
+        // This is written this way to ensure we get a compiler error if we add a new field.
+        Self {
+            allow: merged(&self.allow, &other.allow),
+            warn: merged(&self.warn, &other.warn),
+            deny: merged(&self.deny, &other.deny),
+            forbid: merged(&self.forbid, &other.forbid),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Std {
     pub target: TargetSelection,
+    config: LintConfig,
     /// Whether to lint only a subset of crates.
     crates: Vec<String>,
 }
@@ -108,7 +135,8 @@ impl Step for Std {
 
     fn make_run(run: RunConfig<'_>) {
         let crates = std_crates_for_run_make(&run);
-        run.builder.ensure(Std { target: run.target, crates });
+        let config = LintConfig::new(run.builder);
+        run.builder.ensure(Std { target: run.target, config, crates });
     }
 
     fn run(self, builder: &Builder<'_>) {
@@ -138,7 +166,7 @@ impl Step for Std {
         run_cargo(
             builder,
             cargo,
-            lint_args(builder, IGNORED_RULES_FOR_STD_AND_RUSTC),
+            lint_args(builder, &self.config, IGNORED_RULES_FOR_STD_AND_RUSTC),
             &libstd_stamp(builder, compiler, target),
             vec![],
             true,
@@ -150,6 +178,7 @@ impl Step for Std {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Rustc {
     pub target: TargetSelection,
+    config: LintConfig,
     /// Whether to lint only a subset of crates.
     crates: Vec<String>,
 }
@@ -165,7 +194,8 @@ impl Step for Rustc {
 
     fn make_run(run: RunConfig<'_>) {
         let crates = run.make_run_crates(Alias::Compiler);
-        run.builder.ensure(Rustc { target: run.target, crates });
+        let config = LintConfig::new(run.builder);
+        run.builder.ensure(Rustc { target: run.target, config, crates });
     }
 
     /// Lints the compiler.
@@ -212,7 +242,7 @@ impl Step for Rustc {
         run_cargo(
             builder,
             cargo,
-            lint_args(builder, IGNORED_RULES_FOR_STD_AND_RUSTC),
+            lint_args(builder, &self.config, IGNORED_RULES_FOR_STD_AND_RUSTC),
             &librustc_stamp(builder, compiler, target),
             vec![],
             true,
@@ -232,6 +262,7 @@ macro_rules! lint_any {
         #[derive(Debug, Clone, Hash, PartialEq, Eq)]
         pub struct $name {
             pub target: TargetSelection,
+            config: LintConfig,
         }
 
         impl Step for $name {
@@ -243,8 +274,10 @@ macro_rules! lint_any {
             }
 
             fn make_run(run: RunConfig<'_>) {
+                let config = LintConfig::new(run.builder);
                 run.builder.ensure($name {
                     target: run.target,
+                    config,
                 });
             }
 
@@ -281,7 +314,7 @@ macro_rules! lint_any {
                 run_cargo(
                     builder,
                     cargo,
-                    lint_args(builder, &[]),
+                    lint_args(builder, &self.config, &[]),
                     &stamp,
                     vec![],
                     true,
@@ -295,7 +328,7 @@ macro_rules! lint_any {
 
 lint_any!(
     Bootstrap, "src/bootstrap", "bootstrap";
-    BuildHelper, "src/tools/build_helper", "build_helper";
+    BuildHelper, "src/build_helper", "build_helper";
     BuildManifest, "src/tools/build-manifest", "build-manifest";
     CargoMiri, "src/tools/miri/cargo-miri", "cargo-miri";
     Clippy, "src/tools/clippy", "clippy";
@@ -319,3 +352,58 @@ lint_any!(
     Tidy, "src/tools/tidy", "tidy";
     TestFloatParse, "src/etc/test-float-parse", "test-float-parse";
 );
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct CI {
+    target: TargetSelection,
+    config: LintConfig,
+}
+
+impl Step for CI {
+    type Output = ();
+    const DEFAULT: bool = false;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.alias("ci")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        let config = LintConfig::new(run.builder);
+        run.builder.ensure(CI { target: run.target, config });
+    }
+
+    fn run(self, builder: &Builder<'_>) -> Self::Output {
+        builder.ensure(Bootstrap {
+            target: self.target,
+            config: self.config.merge(&LintConfig {
+                allow: vec![],
+                warn: vec![],
+                deny: vec!["warnings".into()],
+                forbid: vec![],
+            }),
+        });
+        let library_clippy_cfg = LintConfig {
+            allow: vec!["clippy::all".into()],
+            warn: vec![],
+            deny: vec!["clippy::correctness".into()],
+            forbid: vec![],
+        };
+        let compiler_clippy_cfg = LintConfig {
+            allow: vec!["clippy::all".into()],
+            warn: vec![],
+            deny: vec!["clippy::correctness".into(), "clippy::clone_on_ref_ptr".into()],
+            forbid: vec![],
+        };
+
+        builder.ensure(Std {
+            target: self.target,
+            config: self.config.merge(&library_clippy_cfg),
+            crates: vec![],
+        });
+        builder.ensure(Rustc {
+            target: self.target,
+            config: self.config.merge(&compiler_clippy_cfg),
+            crates: vec![],
+        });
+    }
+}
diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 3394f2a84a0..24be705f481 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -1976,9 +1976,13 @@ impl Step for Assemble {
             }
         }
 
-        {
-            // `llvm-strip` is used by rustc, which is actually just a symlink to `llvm-objcopy`,
-            // so copy and rename `llvm-objcopy`.
+        if builder.config.llvm_enabled(target_compiler.host) && builder.config.llvm_tools_enabled {
+            // `llvm-strip` is used by rustc, which is actually just a symlink to `llvm-objcopy`, so
+            // copy and rename `llvm-objcopy`.
+            //
+            // But only do so if llvm-tools are enabled, as bootstrap compiler might not contain any
+            // LLVM tools, e.g. for cg_clif.
+            // See <https://github.com/rust-lang/rust/issues/132719>.
             let src_exe = exe("llvm-objcopy", target_compiler.host);
             let dst_exe = exe("rust-objcopy", target_compiler.host);
             builder.copy_link(&libdir_bin.join(src_exe), &libdir_bin.join(dst_exe));
diff --git a/src/bootstrap/src/core/build_steps/doc.rs b/src/bootstrap/src/core/build_steps/doc.rs
index 69ec832a44a..8a9321f8e79 100644
--- a/src/bootstrap/src/core/build_steps/doc.rs
+++ b/src/bootstrap/src/core/build_steps/doc.rs
@@ -1030,7 +1030,7 @@ macro_rules! tool_doc {
 // NOTE: make sure to register these in `Builder::get_step_description`.
 tool_doc!(
     BuildHelper,
-    "src/tools/build_helper",
+    "src/build_helper",
     rustc_tool = false,
     is_library = true,
     crates = ["build_helper"]
diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index 2c36d8bab82..532c8f767eb 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -1354,7 +1354,7 @@ impl Step for CrateBuildHelper {
     const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.path("src/tools/build_helper")
+        run.path("src/build_helper")
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -1372,7 +1372,7 @@ impl Step for CrateBuildHelper {
             Mode::ToolBootstrap,
             host,
             Kind::Test,
-            "src/tools/build_helper",
+            "src/build_helper",
             SourceType::InTree,
             &[],
         );
diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index 134da5db96d..0688a1d6892 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -1198,15 +1198,6 @@ impl Builder<'_> {
             rustflags.arg("-Zinline-mir-preserve-debug");
         }
 
-        if self.config.rustc_parallel
-            && matches!(mode, Mode::ToolRustc | Mode::Rustc | Mode::Codegen)
-        {
-            // keep in sync with `bootstrap/lib.rs:Build::rustc_features`
-            // `cfg` option for rustc, `features` option for cargo, for conditional compilation
-            rustflags.arg("--cfg=parallel_compiler");
-            rustdocflags.arg("--cfg=parallel_compiler");
-        }
-
         Cargo {
             command: cargo,
             compiler,
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index f1b3cf6da13..d59e0fa7288 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -839,6 +839,7 @@ impl<'a> Builder<'a> {
                 clippy::RustInstaller,
                 clippy::TestFloatParse,
                 clippy::Tidy,
+                clippy::CI,
             ),
             Kind::Check | Kind::Fix => describe!(
                 check::Std,
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index a93038d51d3..95b1303fa71 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -28,6 +28,24 @@ use crate::utils::cache::{INTERNER, Interned};
 use crate::utils::channel::{self, GitInfo};
 use crate::utils::helpers::{self, exe, output, t};
 
+/// Each path in this list is considered "allowed" in the `download-rustc="if-unchanged"` logic.
+/// This means they can be modified and changes to these paths should never trigger a compiler build
+/// when "if-unchanged" is set.
+///
+/// NOTE: Paths must have the ":!" prefix to tell git to ignore changes in those paths during
+/// the diff check.
+///
+/// WARNING: Be cautious when adding paths to this list. If a path that influences the compiler build
+/// is added here, it will cause bootstrap to skip necessary rebuilds, which may lead to risky results.
+/// For example, "src/bootstrap" should never be included in this list as it plays a crucial role in the
+/// final output/compiler, which can be significantly affected by changes made to the bootstrap sources.
+#[rustfmt::skip] // We don't want rustfmt to oneline this list
+pub(crate) const RUSTC_IF_UNCHANGED_ALLOWED_PATHS: &[&str] = &[
+    ":!src/tools",
+    ":!tests",
+    ":!triagebot.toml",
+];
+
 macro_rules! check_ci_llvm {
     ($name:expr) => {
         assert!(
@@ -278,7 +296,6 @@ pub struct Config {
     pub rust_strip: bool,
     pub rust_frame_pointers: bool,
     pub rust_stack_protector: Option<String>,
-    pub rustc_parallel: bool,
     pub rustc_default_linker: Option<String>,
     pub rust_optimize_tests: bool,
     pub rust_dist_src: bool,
@@ -1224,7 +1241,6 @@ impl Config {
             bindir: "bin".into(),
             dist_include_mingw_linker: true,
             dist_compression_profile: "fast".into(),
-            rustc_parallel: true,
 
             stdout_is_tty: std::io::stdout().is_terminal(),
             stderr_is_tty: std::io::stderr().is_terminal(),
@@ -1668,6 +1684,14 @@ impl Config {
         let mut lld_enabled = None;
         let mut std_features = None;
 
+        let is_user_configured_rust_channel =
+            if let Some(channel) = toml.rust.as_ref().and_then(|r| r.channel.clone()) {
+                config.channel = channel;
+                true
+            } else {
+                false
+            };
+
         let default = config.channel == "dev";
         config.omit_git_hash = toml.rust.as_ref().and_then(|r| r.omit_git_hash).unwrap_or(default);
 
@@ -1685,8 +1709,6 @@ impl Config {
         config.in_tree_llvm_info = GitInfo::new(false, &config.src.join("src/llvm-project"));
         config.in_tree_gcc_info = GitInfo::new(false, &config.src.join("src/gcc"));
 
-        let mut is_user_configured_rust_channel = false;
-
         if let Some(rust) = toml.rust {
             let Rust {
                 optimize: optimize_toml,
@@ -1708,7 +1730,7 @@ impl Config {
                 parallel_compiler,
                 randomize_layout,
                 default_linker,
-                channel,
+                channel: _, // already handled above
                 description,
                 musl_root,
                 rpath,
@@ -1745,9 +1767,6 @@ impl Config {
                 std_features: std_features_toml,
             } = rust;
 
-            is_user_configured_rust_channel = channel.is_some();
-            set(&mut config.channel, channel.clone());
-
             config.download_rustc_commit =
                 config.download_ci_rustc_commit(download_rustc, config.llvm_assertions);
 
@@ -1788,8 +1807,14 @@ impl Config {
 
             config.rust_randomize_layout = randomize_layout.unwrap_or_default();
             config.llvm_tools_enabled = llvm_tools.unwrap_or(true);
-            config.rustc_parallel =
-                parallel_compiler.unwrap_or(config.channel == "dev" || config.channel == "nightly");
+
+            // FIXME: Remove this option at the end of 2024.
+            if parallel_compiler.is_some() {
+                println!(
+                    "WARNING: The `rust.parallel-compiler` option is deprecated and does nothing. The parallel compiler (with one thread) is now the default"
+                );
+            }
+
             config.llvm_enzyme =
                 llvm_enzyme.unwrap_or(config.channel == "dev" || config.channel == "nightly");
             config.rustc_default_linker = default_linker;
@@ -2775,32 +2800,33 @@ impl Config {
             }
         };
 
-        let mut files_to_track = vec!["compiler", "src/version", "src/stage0", "src/ci/channel"];
+        // RUSTC_IF_UNCHANGED_ALLOWED_PATHS
+        let mut allowed_paths = RUSTC_IF_UNCHANGED_ALLOWED_PATHS.to_vec();
 
-        // In CI, disable ci-rustc if there are changes in the library tree. But for non-CI, ignore
+        // In CI, disable ci-rustc if there are changes in the library tree. But for non-CI, allow
         // these changes to speed up the build process for library developers. This provides consistent
         // functionality for library developers between `download-rustc=true` and `download-rustc="if-unchanged"`
         // options.
-        if CiEnv::is_ci() {
-            files_to_track.push("library");
+        if !CiEnv::is_ci() {
+            allowed_paths.push(":!library");
         }
 
         // Look for a version to compare to based on the current commit.
         // Only commits merged by bors will have CI artifacts.
-        let commit =
-            match self.last_modified_commit(&files_to_track, "download-rustc", if_unchanged) {
-                Some(commit) => commit,
-                None => {
-                    if if_unchanged {
-                        return None;
-                    }
-                    println!("ERROR: could not find commit hash for downloading rustc");
-                    println!("HELP: maybe your repository history is too shallow?");
-                    println!("HELP: consider setting `rust.download-rustc=false` in config.toml");
-                    println!("HELP: or fetch enough history to include one upstream commit");
-                    crate::exit!(1);
+        let commit = match self.last_modified_commit(&allowed_paths, "download-rustc", if_unchanged)
+        {
+            Some(commit) => commit,
+            None => {
+                if if_unchanged {
+                    return None;
                 }
-            };
+                println!("ERROR: could not find commit hash for downloading rustc");
+                println!("HELP: maybe your repository history is too shallow?");
+                println!("HELP: consider setting `rust.download-rustc=false` in config.toml");
+                println!("HELP: or fetch enough history to include one upstream commit");
+                crate::exit!(1);
+            }
+        };
 
         if CiEnv::is_ci() && {
             let head_sha =
diff --git a/src/bootstrap/src/core/config/tests.rs b/src/bootstrap/src/core/config/tests.rs
index b6523a458e2..24f932a1724 100644
--- a/src/bootstrap/src/core/config/tests.rs
+++ b/src/bootstrap/src/core/config/tests.rs
@@ -8,8 +8,8 @@ use clap::CommandFactory;
 use serde::Deserialize;
 
 use super::flags::Flags;
-use super::{ChangeIdWrapper, Config};
-use crate::core::build_steps::clippy::get_clippy_rules_in_order;
+use super::{ChangeIdWrapper, Config, RUSTC_IF_UNCHANGED_ALLOWED_PATHS};
+use crate::core::build_steps::clippy::{LintConfig, get_clippy_rules_in_order};
 use crate::core::build_steps::llvm;
 use crate::core::config::{LldMode, Target, TargetSelection, TomlConfig};
 
@@ -309,9 +309,10 @@ fn order_of_clippy_rules() {
     ];
     let config = Config::parse(Flags::parse(&args));
 
-    let actual = match &config.cmd {
+    let actual = match config.cmd.clone() {
         crate::Subcommand::Clippy { allow, deny, warn, forbid, .. } => {
-            get_clippy_rules_in_order(&args, &allow, &deny, &warn, &forbid)
+            let cfg = LintConfig { allow, deny, warn, forbid };
+            get_clippy_rules_in_order(&args, &cfg)
         }
         _ => panic!("invalid subcommand"),
     };
@@ -327,6 +328,24 @@ fn order_of_clippy_rules() {
 }
 
 #[test]
+fn clippy_rule_separate_prefix() {
+    let args =
+        vec!["clippy".to_string(), "-A clippy:all".to_string(), "-W clippy::style".to_string()];
+    let config = Config::parse(Flags::parse(&args));
+
+    let actual = match config.cmd.clone() {
+        crate::Subcommand::Clippy { allow, deny, warn, forbid, .. } => {
+            let cfg = LintConfig { allow, deny, warn, forbid };
+            get_clippy_rules_in_order(&args, &cfg)
+        }
+        _ => panic!("invalid subcommand"),
+    };
+
+    let expected = vec!["-A clippy:all".to_string(), "-W clippy::style".to_string()];
+    assert_eq!(expected, actual);
+}
+
+#[test]
 fn verbose_tests_default_value() {
     let config = Config::parse(Flags::parse(&["build".into(), "compiler".into()]));
     assert_eq!(config.verbose_tests, false);
@@ -413,3 +432,18 @@ fn jobs_precedence() {
     );
     assert_eq!(config.jobs, Some(123));
 }
+
+#[test]
+fn check_rustc_if_unchanged_paths() {
+    let config = parse("");
+    let normalised_allowed_paths: Vec<_> = RUSTC_IF_UNCHANGED_ALLOWED_PATHS
+        .iter()
+        .map(|t| {
+            t.strip_prefix(":!").expect(&format!("{t} doesn't have ':!' prefix, but it should."))
+        })
+        .collect();
+
+    for p in normalised_allowed_paths {
+        assert!(config.src.join(p).exists(), "{p} doesn't exist.");
+    }
+}
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index ba74cabcd30..c384fd6bf43 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -80,11 +80,8 @@ const EXTRA_CHECK_CFGS: &[(Option<Mode>, &str, Option<&[&'static str]>)] = &[
     (Some(Mode::Rustc), "llvm_enzyme", None),
     (Some(Mode::Codegen), "llvm_enzyme", None),
     (Some(Mode::ToolRustc), "llvm_enzyme", None),
-    (Some(Mode::Rustc), "parallel_compiler", None),
-    (Some(Mode::ToolRustc), "parallel_compiler", None),
     (Some(Mode::ToolRustc), "rust_analyzer", None),
     (Some(Mode::ToolStd), "rust_analyzer", None),
-    (Some(Mode::Codegen), "parallel_compiler", None),
     // Any library specific cfgs like `target_os`, `target_arch` should be put in
     // priority the `[lints.rust.unexpected_cfgs.check-cfg]` table
     // in the appropriate `library/{std,alloc,core}/Cargo.toml`
@@ -695,9 +692,6 @@ impl Build {
             features.push("llvm");
         }
         // keep in sync with `bootstrap/compile.rs:rustc_cargo_env`
-        if self.config.rustc_parallel && check("rustc_use_parallel_compiler") {
-            features.push("rustc_use_parallel_compiler");
-        }
         if self.config.rust_randomize_layout {
             features.push("rustc_randomized_layouts");
         }
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index 0915ec15a2f..1d05f94e3be 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -291,6 +291,11 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         summary: "New option `llvm.offload` to control whether the llvm offload runtime for GPU support is built. Implicitly enables the openmp runtime as dependency.",
     },
     ChangeInfo {
+        change_id: 132282,
+        severity: ChangeSeverity::Warning,
+        summary: "Deprecated `rust.parallel_compiler` as the compiler now always defaults to being parallel (with 1 thread)",
+    },
+    ChangeInfo {
         change_id: 132494,
         severity: ChangeSeverity::Info,
         summary: "`download-rustc='if-unchanged'` is now a default option for library profile.",
diff --git a/src/bootstrap/src/utils/helpers.rs b/src/bootstrap/src/utils/helpers.rs
index 7162007e9f0..3fb2330469a 100644
--- a/src/bootstrap/src/utils/helpers.rs
+++ b/src/bootstrap/src/utils/helpers.rs
@@ -145,7 +145,7 @@ pub fn symlink_dir(config: &Config, original: &Path, link: &Path) -> io::Result<
 
     #[cfg(windows)]
     fn symlink_dir_inner(target: &Path, junction: &Path) -> io::Result<()> {
-        junction::create(&target, &junction)
+        junction::create(target, junction)
     }
 }