Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

31 files changed, 1028 insertions, 501 deletions

diff --git a/src/bootstrap/CHANGELOG.md b/src/bootstrap/CHANGELOG.md
index 64b74ecc9..4105fa5ec 100644
--- a/src/bootstrap/CHANGELOG.md
+++ b/src/bootstrap/CHANGELOG.md
@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Several unsupported `./configure` options have been removed: `optimize`, `parallel-compiler`. These can still be enabled with `--set`, although it isn't recommended.
 - `remote-test-server`'s `verbose` argument has been removed in favor of the `--verbose` flag
 - `remote-test-server`'s `remote` argument has been removed in favor of the `--bind` flag. Use `--bind 0.0.0.0:12345` to replicate the behavior of the `remote` argument.
+- `x.py fmt` now formats only files modified between the merge-base of HEAD and the last commit in the master branch of the rust-lang repository and the current working directory. To restore old behaviour, use `x.py fmt .`. The check mode is not affected by this change. [#105702](https://github.com/rust-lang/rust/pull/105702)
 
 ### Non-breaking changes
 
diff --git a/src/bootstrap/Cargo.lock b/src/bootstrap/Cargo.lock
index efe8ae316..4a0ba5925 100644
--- a/src/bootstrap/Cargo.lock
+++ b/src/bootstrap/Cargo.lock
@@ -36,6 +36,7 @@ dependencies = [
 name = "bootstrap"
 version = "0.0.0"
 dependencies = [
+ "build_helper",
  "cc",
  "cmake",
  "fd-lock",
@@ -71,6 +72,10 @@ dependencies = [
 ]
 
 [[package]]
+name = "build_helper"
+version = "0.1.0"
+
+[[package]]
 name = "cc"
 version = "1.0.73"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index ccc7ec1fc..22ceeca94 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -29,12 +29,8 @@ name = "sccache-plus-cl"
 path = "bin/sccache-plus-cl.rs"
 test = false
 
-[[bin]]
-name = "llvm-config-wrapper"
-path = "bin/llvm-config-wrapper.rs"
-test = false
-
 [dependencies]
+build_helper = { path = "../tools/build_helper" }
 cmake = "0.1.38"
 fd-lock = "3.0.8"
 filetime = "0.2"
diff --git a/src/bootstrap/README.md b/src/bootstrap/README.md
index 985727bdd..8dce9e79e 100644
--- a/src/bootstrap/README.md
+++ b/src/bootstrap/README.md
@@ -59,10 +59,10 @@ The script accepts commands, flags, and arguments to determine what to do:
   ./x.py test tidy
 
   # execute the UI test suite
-  ./x.py test src/test/ui
+  ./x.py test tests/ui
 
   # execute only some tests in the UI test suite
-  ./x.py test src/test/ui --test-args substring-of-test-name
+  ./x.py test tests/ui --test-args substring-of-test-name
 
   # execute tests in the standard library in stage0
   ./x.py test --stage 0 library/std
@@ -80,18 +80,12 @@ The script accepts commands, flags, and arguments to determine what to do:
 
 ## Configuring rustbuild
 
-There are currently two methods for configuring the rustbuild build system.
-
-First, rustbuild offers a TOML-based configuration system with a `config.toml`
+rustbuild offers a TOML-based configuration system with a `config.toml`
 file. An example of this configuration can be found at `config.toml.example`,
 and the configuration file can also be passed as `--config path/to/config.toml`
 if the build system is being invoked manually (via the python script).
 
-Next, the `./configure` options serialized in `config.mk` will be
-parsed and read. That is, if any `./configure` options are passed, they'll be
-handled naturally. `./configure` should almost never be used for local
-installations, and is primarily useful for CI. Prefer to customize behavior
-using `config.toml`.
+You can generate a config.toml using `./configure` options if you want to automate creating the file without having to edit it.
 
 Finally, rustbuild makes use of the [cc-rs crate] which has [its own
 method][env-vars] of configuring C compilers and C flags via environment
diff --git a/src/bootstrap/bin/llvm-config-wrapper.rs b/src/bootstrap/bin/llvm-config-wrapper.rs
deleted file mode 100644
index 89984bb55..000000000
--- a/src/bootstrap/bin/llvm-config-wrapper.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-// The sheer existence of this file is an awful hack. See the comments in
-// `src/bootstrap/native.rs` for why this is needed when compiling LLD.
-
-use std::env;
-use std::io::{self, Write};
-use std::process::{self, Command, Stdio};
-
-fn main() {
-    let real_llvm_config = env::var_os("LLVM_CONFIG_REAL").unwrap();
-    let mut cmd = Command::new(real_llvm_config);
-    cmd.args(env::args().skip(1)).stderr(Stdio::piped());
-    let output = cmd.output().expect("failed to spawn llvm-config");
-    let mut stdout = String::from_utf8_lossy(&output.stdout);
-
-    if let Ok(to_replace) = env::var("LLVM_CONFIG_SHIM_REPLACE") {
-        if let Ok(replace_with) = env::var("LLVM_CONFIG_SHIM_REPLACE_WITH") {
-            stdout = stdout.replace(&to_replace, &replace_with).into();
-        }
-    }
-
-    print!("{}", stdout.replace("\\", "/"));
-    io::stdout().flush().unwrap();
-    process::exit(output.status.code().unwrap_or(1));
-}
diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 1d5260228..9611c866d 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -154,6 +154,41 @@ fn main() {
         cmd.arg("-Z").arg("force-unstable-if-unmarked");
     }
 
+    // allow-features is handled from within this rustc wrapper because of
+    // issues with build scripts. Some packages use build scripts to
+    // dynamically detect if certain nightly features are available.
+    // There are different ways this causes problems:
+    //
+    // * rustix runs `rustc` on a small test program to see if the feature is
+    //   available (and sets a `cfg` if it is). It does not honor
+    //   CARGO_ENCODED_RUSTFLAGS.
+    // * proc-macro2 detects if `rustc -vV` says "nighty" or "dev" and enables
+    //   nightly features. It will scan CARGO_ENCODED_RUSTFLAGS for
+    //   -Zallow-features. Unfortunately CARGO_ENCODED_RUSTFLAGS is not set
+    //   for build-dependencies when --target is used.
+    //
+    // The issues above means we can't just use RUSTFLAGS, and we can't use
+    // `cargo -Zallow-features=…`. Passing it through here ensures that it
+    // always gets set. Unfortunately that also means we need to enable more
+    // features than we really want (like those for proc-macro2), but there
+    // isn't much of a way around it.
+    //
+    // I think it is unfortunate that build scripts are doing this at all,
+    // since changes to nightly features can cause crates to break even if the
+    // user didn't want or care about the use of the nightly features. I think
+    // nightly features should be opt-in only. Unfortunately the dynamic
+    // checks are now too wide spread that we just need to deal with it.
+    //
+    // If you want to try to remove this, I suggest working with the crate
+    // authors to remove the dynamic checking. Another option is to pursue
+    // https://github.com/rust-lang/cargo/issues/11244 and
+    // https://github.com/rust-lang/cargo/issues/4423, which will likely be
+    // very difficult, but could help expose -Zallow-features into build
+    // scripts so they could try to honor them.
+    if let Ok(allow_features) = env::var("RUSTC_ALLOW_FEATURES") {
+        cmd.arg(format!("-Zallow-features={allow_features}"));
+    }
+
     if let Ok(flags) = env::var("MAGIC_EXTRA_RUSTFLAGS") {
         for flag in flags.split(' ') {
             cmd.arg(flag);
diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 2d5018d93..9cf43fc7a 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -753,6 +753,9 @@ class RustBuild(object):
             target_features += ["-crt-static"]
         if target_features:
             env["RUSTFLAGS"] += " -C target-feature=" + (",".join(target_features))
+        target_linker = self.get_toml("linker", build_section)
+        if target_linker is not None:
+            env["RUSTFLAGS"] += " -C linker=" + target_linker
         env["RUSTFLAGS"] += " -Wrust_2018_idioms -Wunused_lifetimes"
         env["RUSTFLAGS"] += " -Wsemicolon_in_expressions_from_macros"
         if self.get_toml("deny-warnings", "rust") != "false":
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 8ee6d49da..b4fc1d4f2 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -13,17 +13,18 @@ use std::time::{Duration, Instant};
 
 use crate::cache::{Cache, Interned, INTERNER};
 use crate::config::{SplitDebuginfo, TargetSelection};
-use crate::dist;
 use crate::doc;
 use crate::flags::{Color, Subcommand};
 use crate::install;
 use crate::native;
 use crate::run;
+use crate::setup;
 use crate::test;
 use crate::tool::{self, SourceType};
 use crate::util::{self, add_dylib_path, add_link_lib_path, exe, libdir, output, t};
 use crate::EXTRA_CHECK_CFGS;
 use crate::{check, compile, Crate};
+use crate::{clean, dist};
 use crate::{Build, CLang, DocTests, GitRepo, Mode};
 
 pub use crate::Compiler;
@@ -95,6 +96,35 @@ impl RunConfig<'_> {
     pub fn build_triple(&self) -> TargetSelection {
         self.builder.build.build
     }
+
+    /// Return a list of crate names selected by `run.paths`.
+    pub fn cargo_crates_in_set(&self) -> Interned<Vec<String>> {
+        let mut crates = Vec::new();
+        for krate in &self.paths {
+            let path = krate.assert_single_path();
+            let crate_name = self.builder.crate_paths[&path.path];
+            crates.push(crate_name.to_string());
+        }
+        INTERNER.intern_list(crates)
+    }
+}
+
+/// A description of the crates in this set, suitable for passing to `builder.info`.
+///
+/// `crates` should be generated by [`RunConfig::cargo_crates_in_set`].
+pub fn crate_description(crates: &[impl AsRef<str>]) -> String {
+    if crates.is_empty() {
+        return "".into();
+    }
+
+    let mut descr = String::from(" {");
+    descr.push_str(crates[0].as_ref());
+    for krate in &crates[1..] {
+        descr.push_str(", ");
+        descr.push_str(krate.as_ref());
+    }
+    descr.push('}');
+    descr
 }
 
 struct StepDescription {
@@ -161,9 +191,9 @@ pub enum PathSet {
     /// A "suite" of paths.
     ///
     /// These can match as a path suffix (like `Set`), or as a prefix. For
-    /// example, a command-line value of `src/test/ui/abi/variadic-ffi.rs`
-    /// will match `src/test/ui`. A command-line value of `ui` would also
-    /// match `src/test/ui`.
+    /// example, a command-line value of `tests/ui/abi/variadic-ffi.rs`
+    /// will match `tests/ui`. A command-line value of `ui` would also
+    /// match `tests/ui`.
     Suite(TaskPath),
 }
 
@@ -433,8 +463,11 @@ impl<'a> ShouldRun<'a> {
 
     // single alias, which does not correspond to any on-disk path
     pub fn alias(mut self, alias: &str) -> Self {
+        // exceptional case for `Kind::Setup` because its `library`
+        // and `compiler` options would otherwise naively match with
+        // `compiler` and `library` folders respectively.
         assert!(
-            !self.builder.src.join(alias).exists(),
+            self.kind == Kind::Setup || !self.builder.src.join(alias).exists(),
             "use `builder.path()` for real paths: {}",
             alias
         );
@@ -629,6 +662,7 @@ impl<'a> Builder<'a> {
                 crate::toolstate::ToolStateCheck,
                 test::ExpandYamlAnchors,
                 test::Tidy,
+                test::TidySelfTest,
                 test::Ui,
                 test::RunPassValgrind,
                 test::MirOpt,
@@ -698,6 +732,7 @@ impl<'a> Builder<'a> {
                 doc::RustdocBook,
                 doc::RustByExample,
                 doc::RustcBook,
+                doc::Cargo,
                 doc::CargoBook,
                 doc::Clippy,
                 doc::ClippyBook,
@@ -744,6 +779,7 @@ impl<'a> Builder<'a> {
                 install::RustDemangler,
                 install::Clippy,
                 install::Miri,
+                install::LlvmTools,
                 install::Analysis,
                 install::Src,
                 install::Rustc
@@ -757,8 +793,10 @@ impl<'a> Builder<'a> {
                 run::CollectLicenseMetadata,
                 run::GenerateCopyright,
             ),
-            // These commands either don't use paths, or they're special-cased in Build::build()
-            Kind::Clean | Kind::Format | Kind::Setup => vec![],
+            Kind::Setup => describe!(setup::Profile),
+            Kind::Clean => describe!(clean::CleanAll, clean::Rustc, clean::Std),
+            // special-cased in Build::build()
+            Kind::Format => vec![],
         }
     }
 
@@ -820,10 +858,12 @@ impl<'a> Builder<'a> {
             Subcommand::Dist { ref paths } => (Kind::Dist, &paths[..]),
             Subcommand::Install { ref paths } => (Kind::Install, &paths[..]),
             Subcommand::Run { ref paths, .. } => (Kind::Run, &paths[..]),
+            Subcommand::Clean { ref paths, .. } => (Kind::Clean, &paths[..]),
             Subcommand::Format { .. } => (Kind::Format, &[][..]),
-            Subcommand::Clean { .. } | Subcommand::Setup { .. } => {
-                panic!()
-            }
+            Subcommand::Setup { profile: ref path } => (
+                Kind::Setup,
+                path.as_ref().map_or([].as_slice(), |path| std::slice::from_ref(path)),
+            ),
         };
 
         Self::new_internal(build, kind, paths.to_owned())
@@ -1058,7 +1098,7 @@ impl<'a> Builder<'a> {
     /// check build or dry-run, where there's no need to build all of LLVM.
     fn llvm_config(&self, target: TargetSelection) -> Option<PathBuf> {
         if self.config.llvm_enabled() && self.kind != Kind::Check && !self.config.dry_run() {
-            let llvm_config = self.ensure(native::Llvm { target });
+            let native::LlvmResult { llvm_config, .. } = self.ensure(native::Llvm { target });
             if llvm_config.is_file() {
                 return Some(llvm_config);
             }
@@ -1066,6 +1106,62 @@ impl<'a> Builder<'a> {
         None
     }
 
+    /// Like `cargo`, but only passes flags that are valid for all commands.
+    pub fn bare_cargo(
+        &self,
+        compiler: Compiler,
+        mode: Mode,
+        target: TargetSelection,
+        cmd: &str,
+    ) -> Command {
+        let mut cargo = Command::new(&self.initial_cargo);
+        // Run cargo from the source root so it can find .cargo/config.
+        // This matters when using vendoring and the working directory is outside the repository.
+        cargo.current_dir(&self.src);
+
+        let out_dir = self.stage_out(compiler, mode);
+        cargo.env("CARGO_TARGET_DIR", &out_dir).arg(cmd);
+
+        // Found with `rg "init_env_logger\("`. If anyone uses `init_env_logger`
+        // from out of tree it shouldn't matter, since x.py is only used for
+        // building in-tree.
+        let color_logs = ["RUSTDOC_LOG_COLOR", "RUSTC_LOG_COLOR", "RUST_LOG_COLOR"];
+        match self.build.config.color {
+            Color::Always => {
+                cargo.arg("--color=always");
+                for log in &color_logs {
+                    cargo.env(log, "always");
+                }
+            }
+            Color::Never => {
+                cargo.arg("--color=never");
+                for log in &color_logs {
+                    cargo.env(log, "never");
+                }
+            }
+            Color::Auto => {} // nothing to do
+        }
+
+        if cmd != "install" {
+            cargo.arg("--target").arg(target.rustc_target_arg());
+        } else {
+            assert_eq!(target, compiler.host);
+        }
+
+        if self.config.rust_optimize {
+            // FIXME: cargo bench/install do not accept `--release`
+            if cmd != "bench" && cmd != "install" {
+                cargo.arg("--release");
+            }
+        }
+
+        // Remove make-related flags to ensure Cargo can correctly set things up
+        cargo.env_remove("MAKEFLAGS");
+        cargo.env_remove("MFLAGS");
+
+        cargo
+    }
+
     /// Prepares an invocation of `cargo` to be run.
     ///
     /// This will create a `Command` that represents a pending execution of
@@ -1081,11 +1177,8 @@ impl<'a> Builder<'a> {
         target: TargetSelection,
         cmd: &str,
     ) -> Cargo {
-        let mut cargo = Command::new(&self.initial_cargo);
+        let mut cargo = self.bare_cargo(compiler, mode, target, cmd);
         let out_dir = self.stage_out(compiler, mode);
-        // Run cargo from the source root so it can find .cargo/config.
-        // This matters when using vendoring and the working directory is outside the repository.
-        cargo.current_dir(&self.src);
 
         // Codegen backends are not yet tracked by -Zbinary-dep-depinfo,
         // so we need to explicitly clear out if they've been updated.
@@ -1110,8 +1203,6 @@ impl<'a> Builder<'a> {
             self.clear_if_dirty(&my_out, &rustdoc);
         }
 
-        cargo.env("CARGO_TARGET_DIR", &out_dir).arg(cmd);
-
         let profile_var = |name: &str| {
             let profile = if self.config.rust_optimize { "RELEASE" } else { "DEV" };
             format!("CARGO_PROFILE_{}_{}", profile, name)
@@ -1124,32 +1215,6 @@ impl<'a> Builder<'a> {
             cargo.env("REAL_LIBRARY_PATH", e);
         }
 
-        // Found with `rg "init_env_logger\("`. If anyone uses `init_env_logger`
-        // from out of tree it shouldn't matter, since x.py is only used for
-        // building in-tree.
-        let color_logs = ["RUSTDOC_LOG_COLOR", "RUSTC_LOG_COLOR", "RUST_LOG_COLOR"];
-        match self.build.config.color {
-            Color::Always => {
-                cargo.arg("--color=always");
-                for log in &color_logs {
-                    cargo.env(log, "always");
-                }
-            }
-            Color::Never => {
-                cargo.arg("--color=never");
-                for log in &color_logs {
-                    cargo.env(log, "never");
-                }
-            }
-            Color::Auto => {} // nothing to do
-        }
-
-        if cmd != "install" {
-            cargo.arg("--target").arg(target.rustc_target_arg());
-        } else {
-            assert_eq!(target, compiler.host);
-        }
-
         // Set a flag for `check`/`clippy`/`fix`, so that certain build
         // scripts can do less work (i.e. not building/requiring LLVM).
         if cmd == "check" || cmd == "clippy" || cmd == "fix" {
@@ -1316,23 +1381,31 @@ impl<'a> Builder<'a> {
         // this), as well as #63012 which is the tracking issue for this
         // feature on the rustc side.
         cargo.arg("-Zbinary-dep-depinfo");
-        match mode {
-            Mode::ToolBootstrap => {
-                // Restrict the allowed features to those passed by rustbuild, so we don't depend on nightly accidentally.
-                rustflags.arg("-Zallow-features=binary-dep-depinfo");
+        let allow_features = match mode {
+            Mode::ToolBootstrap | Mode::ToolStd => {
+                // Restrict the allowed features so we don't depend on nightly
+                // accidentally.
+                //
+                // binary-dep-depinfo is used by rustbuild itself for all
+                // compilations.
+                //
+                // Lots of tools depend on proc_macro2 and proc-macro-error.
+                // Those have build scripts which assume nightly features are
+                // available if the `rustc` version is "nighty" or "dev". See
+                // bin/rustc.rs for why that is a problem. Instead of labeling
+                // those features for each individual tool that needs them,
+                // just blanket allow them here.
+                //
+                // If this is ever removed, be sure to add something else in
+                // its place to keep the restrictions in place (or make a way
+                // to unset RUSTC_BOOTSTRAP).
+                "binary-dep-depinfo,proc_macro_span,proc_macro_span_shrink,proc_macro_diagnostic"
+                    .to_string()
             }
-            Mode::ToolStd => {
-                // Right now this is just compiletest and a few other tools that build on stable.
-                // Allow them to use `feature(test)`, but nothing else.
-                rustflags.arg("-Zallow-features=binary-dep-depinfo,test,proc_macro_internals,proc_macro_diagnostic,proc_macro_span");
-            }
-            Mode::Std | Mode::Rustc | Mode::Codegen | Mode::ToolRustc => {}
-        }
+            Mode::Std | Mode::Rustc | Mode::Codegen | Mode::ToolRustc => String::new(),
+        };
 
         cargo.arg("-j").arg(self.jobs().to_string());
-        // Remove make-related flags to ensure Cargo can correctly set things up
-        cargo.env_remove("MAKEFLAGS");
-        cargo.env_remove("MFLAGS");
 
         // FIXME: Temporary fix for https://github.com/rust-lang/cargo/issues/3005
         // Force cargo to output binaries with disambiguating hashes in the name
@@ -1816,13 +1889,6 @@ impl<'a> Builder<'a> {
             }
         }
 
-        if self.config.rust_optimize {
-            // FIXME: cargo bench/install do not accept `--release`
-            if cmd != "bench" && cmd != "install" {
-                cargo.arg("--release");
-            }
-        }
-
         if self.config.locked_deps {
             cargo.arg("--locked");
         }
@@ -1853,11 +1919,14 @@ impl<'a> Builder<'a> {
             };
 
             if let Some(limit) = limit {
-                rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={}", limit));
+                if stage == 0 || self.config.default_codegen_backend().unwrap_or_default() == "llvm"
+                {
+                    rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={}", limit));
+                }
             }
         }
 
-        Cargo { command: cargo, rustflags, rustdocflags }
+        Cargo { command: cargo, rustflags, rustdocflags, allow_features }
     }
 
     /// Ensure that a given step is built, returning its output. This will
@@ -2036,6 +2105,7 @@ pub struct Cargo {
     command: Command,
     rustflags: Rustflags,
     rustdocflags: Rustflags,
+    allow_features: String,
 }
 
 impl Cargo {
@@ -2080,6 +2150,18 @@ impl Cargo {
         self.command.current_dir(dir);
         self
     }
+
+    /// Adds nightly-only features that this invocation is allowed to use.
+    ///
+    /// By default, all nightly features are allowed. Once this is called, it
+    /// will be restricted to the given set.
+    pub fn allow_features(&mut self, features: &str) -> &mut Cargo {
+        if !self.allow_features.is_empty() {
+            self.allow_features.push(',');
+        }
+        self.allow_features.push_str(features);
+        self
+    }
 }
 
 impl From<Cargo> for Command {
@@ -2094,6 +2176,10 @@ impl From<Cargo> for Command {
             cargo.command.env("RUSTDOCFLAGS", rustdocflags);
         }
 
+        if !cargo.allow_features.is_empty() {
+            cargo.command.env("RUSTC_ALLOW_FEATURES", cargo.allow_features);
+        }
+
         cargo.command
     }
 }
diff --git a/src/bootstrap/builder/tests.rs b/src/bootstrap/builder/tests.rs
index 5f21d2b00..d5fcd1075 100644
--- a/src/bootstrap/builder/tests.rs
+++ b/src/bootstrap/builder/tests.rs
@@ -78,7 +78,7 @@ macro_rules! rustc {
 #[test]
 fn test_valid() {
     // make sure multi suite paths are accepted
-    check_cli(["test", "src/test/ui/attr-start.rs", "src/test/ui/attr-shebang.rs"]);
+    check_cli(["test", "tests/ui/attr-start.rs", "tests/ui/attr-shebang.rs"]);
 }
 
 #[test]
diff --git a/src/bootstrap/cc_detect.rs b/src/bootstrap/cc_detect.rs
index 7128d542a..65c882fb8 100644
--- a/src/bootstrap/cc_detect.rs
+++ b/src/bootstrap/cc_detect.rs
@@ -47,6 +47,8 @@ fn cc2ar(cc: &Path, target: TargetSelection) -> Option<PathBuf> {
         Some(PathBuf::from("ar"))
     } else if target.contains("vxworks") {
         Some(PathBuf::from("wr-ar"))
+    } else if target.contains("android") {
+        Some(cc.parent().unwrap().join(PathBuf::from("llvm-ar")))
     } else {
         let parent = cc.parent().unwrap();
         let file = cc.file_name().unwrap().to_str().unwrap();
@@ -219,12 +221,22 @@ fn set_compiler(
 }
 
 pub(crate) fn ndk_compiler(compiler: Language, triple: &str, ndk: &Path) -> PathBuf {
-    let triple_translated = triple
-        .replace("armv7neon", "arm")
-        .replace("armv7", "arm")
-        .replace("thumbv7neon", "arm")
-        .replace("thumbv7", "arm");
-    let compiler = format!("{}-{}", triple_translated, compiler.clang());
+    let mut triple_iter = triple.split("-");
+    let triple_translated = if let Some(arch) = triple_iter.next() {
+        let arch_new = match arch {
+            "arm" | "armv7" | "armv7neon" | "thumbv7" | "thumbv7neon" => "armv7a",
+            other => other,
+        };
+        std::iter::once(arch_new).chain(triple_iter).collect::<Vec<&str>>().join("-")
+    } else {
+        triple.to_string()
+    };
+
+    // API 19 is the earliest API level supported by NDK r25b but AArch64 and x86_64 support
+    // begins at API level 21.
+    let api_level =
+        if triple.contains("aarch64") || triple.contains("x86_64") { "21" } else { "19" };
+    let compiler = format!("{}{}-{}", triple_translated, api_level, compiler.clang());
     ndk.join("bin").join(compiler)
 }
 
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 2e1bd8d6d..4b8a58e87 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -101,7 +101,7 @@ impl Step for Std {
         std_cargo(builder, target, compiler.stage, &mut cargo);
 
         builder.info(&format!(
-            "Checking stage{} std artifacts ({} -> {})",
+            "Checking stage{} library artifacts ({} -> {})",
             builder.top_stage, &compiler.host, target
         ));
         run_cargo(
@@ -111,6 +111,7 @@ impl Step for Std {
             &libstd_stamp(builder, compiler, target),
             vec![],
             true,
+            false,
         );
 
         // We skip populating the sysroot in non-zero stage because that'll lead
@@ -157,7 +158,7 @@ impl Step for Std {
         }
 
         builder.info(&format!(
-            "Checking stage{} std test/bench/example targets ({} -> {})",
+            "Checking stage{} library test/bench/example targets ({} -> {})",
             builder.top_stage, &compiler.host, target
         ));
         run_cargo(
@@ -167,6 +168,7 @@ impl Step for Std {
             &libstd_test_stamp(builder, compiler, target),
             vec![],
             true,
+            false,
         );
     }
 }
@@ -243,6 +245,7 @@ impl Step for Rustc {
             &librustc_stamp(builder, compiler, target),
             vec![],
             true,
+            false,
         );
 
         let libdir = builder.sysroot_libdir(compiler, target);
@@ -303,6 +306,7 @@ impl Step for CodegenBackend {
             &codegen_backend_stamp(builder, compiler, target, backend),
             vec![],
             true,
+            false,
         );
     }
 }
@@ -342,9 +346,7 @@ impl Step for RustAnalyzer {
             &["rust-analyzer/in-rust-tree".to_owned()],
         );
 
-        cargo.rustflag(
-            "-Zallow-features=proc_macro_internals,proc_macro_diagnostic,proc_macro_span",
-        );
+        cargo.allow_features(crate::tool::RustAnalyzer::ALLOW_FEATURES);
 
         // For ./x.py clippy, don't check those targets because
         // linting tests and benchmarks can produce very noisy results
@@ -359,7 +361,15 @@ impl Step for RustAnalyzer {
             "Checking stage{} {} artifacts ({} -> {})",
             compiler.stage, "rust-analyzer", &compiler.host.triple, target.triple
         ));
-        run_cargo(builder, cargo, args(builder), &stamp(builder, compiler, target), vec![], true);
+        run_cargo(
+            builder,
+            cargo,
+            args(builder),
+            &stamp(builder, compiler, target),
+            vec![],
+            true,
+            false,
+        );
 
         /// Cargo's output path in a given stage, compiled by a particular
         /// compiler for the specified target.
@@ -432,6 +442,7 @@ macro_rules! tool_check_step {
                     &stamp(builder, compiler, target),
                     vec![],
                     true,
+                    false,
                 );
 
                 /// Cargo's output path in a given stage, compiled by a particular
diff --git a/src/bootstrap/clean.rs b/src/bootstrap/clean.rs
index 069f3d6ac..468efc111 100644
--- a/src/bootstrap/clean.rs
+++ b/src/bootstrap/clean.rs
@@ -9,10 +9,81 @@ use std::fs;
 use std::io::{self, ErrorKind};
 use std::path::Path;
 
+use crate::builder::{crate_description, Builder, RunConfig, ShouldRun, Step};
+use crate::cache::Interned;
 use crate::util::t;
-use crate::Build;
+use crate::{Build, Compiler, Mode, Subcommand};
 
-pub fn clean(build: &Build, all: bool) {
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct CleanAll {}
+
+impl Step for CleanAll {
+    const DEFAULT: bool = true;
+    type Output = ();
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(CleanAll {})
+    }
+
+    fn run(self, builder: &Builder<'_>) -> Self::Output {
+        let Subcommand::Clean { all, .. } = builder.config.cmd else { unreachable!("wrong subcommand?") };
+        clean_default(builder.build, all)
+    }
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.never() // handled by DEFAULT
+    }
+}
+
+macro_rules! clean_crate_tree {
+    ( $( $name:ident, $mode:path, $root_crate:literal);+ $(;)? ) => { $(
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+        pub struct $name {
+            compiler: Compiler,
+            crates: Interned<Vec<String>>,
+        }
+
+        impl Step for $name {
+            type Output = ();
+
+            fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+                let crates = run.builder.in_tree_crates($root_crate, None);
+                run.crates(crates)
+            }
+
+            fn make_run(run: RunConfig<'_>) {
+                let builder = run.builder;
+                let compiler = builder.compiler(builder.top_stage, run.target);
+                builder.ensure(Self { crates: run.cargo_crates_in_set(), compiler });
+            }
+
+            fn run(self, builder: &Builder<'_>) -> Self::Output {
+                let compiler = self.compiler;
+                let target = compiler.host;
+                let mut cargo = builder.bare_cargo(compiler, $mode, target, "clean");
+                for krate in &*self.crates {
+                    cargo.arg(krate);
+                }
+
+                builder.info(&format!(
+                    "Cleaning{} stage{} {} artifacts ({} -> {})",
+                    crate_description(&self.crates), compiler.stage, stringify!($name).to_lowercase(), &compiler.host, target,
+                ));
+
+                // NOTE: doesn't use `run_cargo` because we don't want to save a stamp file,
+                // and doesn't use `stream_cargo` to avoid passing `--message-format` which `clean` doesn't accept.
+                builder.run(&mut cargo);
+            }
+        }
+    )+ }
+}
+
+clean_crate_tree! {
+    Rustc, Mode::Rustc, "rustc-main";
+    Std, Mode::Std, "test";
+}
+
+fn clean_default(build: &Build, all: bool) {
     rm_rf("tmp".as_ref());
 
     if all {
@@ -21,6 +92,7 @@ pub fn clean(build: &Build, all: bool) {
         rm_rf(&build.out.join("tmp"));
         rm_rf(&build.out.join("dist"));
         rm_rf(&build.out.join("bootstrap"));
+        rm_rf(&build.out.join("rustfmt.stamp"));
 
         for host in &build.hosts {
             let entries = match build.out.join(host.triple).read_dir() {
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 0deed3f99..68d1db016 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -18,6 +18,7 @@ use std::str;
 
 use serde::Deserialize;
 
+use crate::builder::crate_description;
 use crate::builder::Cargo;
 use crate::builder::{Builder, Kind, RunConfig, ShouldRun, Step};
 use crate::cache::{Interned, INTERNER};
@@ -46,17 +47,6 @@ impl Std {
     }
 }
 
-/// Return a `-p=x -p=y` string suitable for passing to a cargo invocation.
-fn build_crates_in_set(run: &RunConfig<'_>) -> Interned<Vec<String>> {
-    let mut crates = Vec::new();
-    for krate in &run.paths {
-        let path = krate.assert_single_path();
-        let crate_name = run.builder.crate_paths[&path.path];
-        crates.push(format!("-p={crate_name}"));
-    }
-    INTERNER.intern_list(crates)
-}
-
 impl Step for Std {
     type Output = ();
     const DEFAULT: bool = true;
@@ -76,7 +66,7 @@ impl Step for Std {
         // Build all crates anyway, as if they hadn't passed the other args.
         let has_library =
             run.paths.iter().any(|set| set.assert_single_path().path.ends_with("library"));
-        let crates = if has_library { Default::default() } else { build_crates_in_set(&run) };
+        let crates = if has_library { Default::default() } else { run.cargo_crates_in_set() };
         run.builder.ensure(Std {
             compiler: run.builder.compiler(run.builder.top_stage, run.build_triple()),
             target: run.target,
@@ -121,7 +111,10 @@ impl Step for Std {
         let compiler_to_use = builder.compiler_for(compiler.stage, compiler.host, target);
         if compiler_to_use != compiler {
             builder.ensure(Std::new(compiler_to_use, target));
-            builder.info(&format!("Uplifting stage1 std ({} -> {})", compiler_to_use.host, target));
+            builder.info(&format!(
+                "Uplifting stage1 library ({} -> {})",
+                compiler_to_use.host, target
+            ));
 
             // Even if we're not building std this stage, the new sysroot must
             // still contain the third party objects needed by various targets.
@@ -137,18 +130,25 @@ impl Step for Std {
 
         let mut cargo = builder.cargo(compiler, Mode::Std, SourceType::InTree, target, "build");
         std_cargo(builder, target, compiler.stage, &mut cargo);
+        for krate in &*self.crates {
+            cargo.arg("-p").arg(krate);
+        }
 
         builder.info(&format!(
-            "Building stage{} std artifacts ({} -> {})",
-            compiler.stage, &compiler.host, target
+            "Building{} stage{} library artifacts ({} -> {})",
+            crate_description(&self.crates),
+            compiler.stage,
+            &compiler.host,
+            target,
         ));
         run_cargo(
             builder,
             cargo,
-            self.crates.to_vec(),
+            vec![],
             &libstd_stamp(builder, compiler, target),
             target_deps,
             false,
+            false,
         );
 
         builder.ensure(StdLink::from_std(
@@ -321,8 +321,15 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
         ""
     };
 
+    let mut features = String::new();
+
+    // Cranelift doesn't support `asm`.
+    if stage != 0 && builder.config.default_codegen_backend().unwrap_or_default() == "cranelift" {
+        features += " compiler-builtins-no-asm";
+    }
+
     if builder.no_std(target) == Some(true) {
-        let mut features = "compiler-builtins-mem".to_string();
+        features += " compiler-builtins-mem";
         if !target.starts_with("bpf") {
             features.push_str(compiler_builtins_c_feature);
         }
@@ -335,7 +342,7 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
             .arg("--features")
             .arg(features);
     } else {
-        let mut features = builder.std_features(target);
+        features += &builder.std_features(target);
         features.push_str(compiler_builtins_c_feature);
 
         cargo
@@ -429,7 +436,7 @@ impl Step for StdLink {
         let target_compiler = self.target_compiler;
         let target = self.target;
         builder.info(&format!(
-            "Copying stage{} std from stage{} ({} -> {} / {})",
+            "Copying stage{} library from stage{} ({} -> {} / {})",
             target_compiler.stage, compiler.stage, &compiler.host, target_compiler.host, target
         ));
         let libdir = builder.sysroot_libdir(target_compiler, target);
@@ -596,7 +603,7 @@ impl Step for Rustc {
     }
 
     fn make_run(run: RunConfig<'_>) {
-        let crates = build_crates_in_set(&run);
+        let crates = run.cargo_crates_in_set();
         run.builder.ensure(Rustc {
             compiler: run.builder.compiler(run.builder.top_stage, run.build_triple()),
             target: run.target,
@@ -695,7 +702,8 @@ impl Step for Rustc {
             ));
         }
 
-        // cfg(bootstrap): remove if condition once the bootstrap compiler supports dylib LTO
+        // We currently don't support cross-crate LTO in stage0. This also isn't hugely necessary
+        // and may just be a time sink.
         if compiler.stage != 0 {
             match builder.config.rust_lto {
                 RustcLto::Thin | RustcLto::Fat => {
@@ -717,17 +725,25 @@ impl Step for Rustc {
             }
         }
 
+        for krate in &*self.crates {
+            cargo.arg("-p").arg(krate);
+        }
+
         builder.info(&format!(
-            "Building stage{} compiler artifacts ({} -> {})",
-            compiler.stage, &compiler.host, target
+            "Building{} stage{} compiler artifacts ({} -> {})",
+            crate_description(&self.crates),
+            compiler.stage,
+            &compiler.host,
+            target,
         ));
         run_cargo(
             builder,
             cargo,
-            self.crates.to_vec(),
+            vec![],
             &librustc_stamp(builder, compiler, target),
             vec![],
             false,
+            true, // Only ship rustc_driver.so and .rmeta files, not all intermediate .rlib files.
         );
 
         builder.ensure(RustcLink::from_rustc(
@@ -754,7 +770,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
         .env("CFG_RELEASE_CHANNEL", &builder.config.channel)
         .env("CFG_VERSION", builder.rust_version());
 
-    if let Some(backend) = builder.config.rust_codegen_backends.get(0) {
+    if let Some(backend) = builder.config.default_codegen_backend() {
         cargo.env("CFG_DEFAULT_CODEGEN_BACKEND", backend);
     }
 
@@ -805,7 +821,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
         if builder.is_rust_llvm(target) {
             cargo.env("LLVM_RUSTLLVM", "1");
         }
-        let llvm_config = builder.ensure(native::Llvm { target });
+        let native::LlvmResult { llvm_config, .. } = builder.ensure(native::Llvm { target });
         cargo.env("LLVM_CONFIG", &llvm_config);
         if let Some(s) = target_config.and_then(|c| c.llvm_config.as_ref()) {
             cargo.env("CFG_LLVM_ROOT", s);
@@ -984,7 +1000,7 @@ impl Step for CodegenBackend {
             "Building stage{} codegen backend {} ({} -> {})",
             compiler.stage, backend, &compiler.host, target
         ));
-        let files = run_cargo(builder, cargo, vec![], &tmp_stamp, vec![], false);
+        let files = run_cargo(builder, cargo, vec![], &tmp_stamp, vec![], false, false);
         if builder.config.dry_run() {
             return;
         }
@@ -1177,7 +1193,7 @@ impl Step for Sysroot {
             );
             if builder.config.rust_remap_debuginfo {
                 eprintln!(
-                    "warning: some `src/test/ui` tests will fail when lacking `{}`",
+                    "warning: some `tests/ui` tests will fail when lacking `{}`",
                     sysroot_lib_rustlib_src_rust.display(),
                 );
             }
@@ -1341,9 +1357,10 @@ impl Step for Assemble {
         }
 
         if builder.config.rust_codegen_backends.contains(&INTERNER.intern_str("llvm")) {
-            let llvm_config_bin = builder.ensure(native::Llvm { target: target_compiler.host });
+            let native::LlvmResult { llvm_config, .. } =
+                builder.ensure(native::Llvm { target: target_compiler.host });
             if !builder.config.dry_run() {
-                let llvm_bin_dir = output(Command::new(llvm_config_bin).arg("--bindir"));
+                let llvm_bin_dir = output(Command::new(llvm_config).arg("--bindir"));
                 let llvm_bin_dir = Path::new(llvm_bin_dir.trim());
 
                 // Since we've already built the LLVM tools, install them to the sysroot.
@@ -1411,6 +1428,7 @@ pub fn run_cargo(
     stamp: &Path,
     additional_target_deps: Vec<(PathBuf, DependencyType)>,
     is_check: bool,
+    rlib_only_metadata: bool,
 ) -> Vec<PathBuf> {
     if builder.config.dry_run() {
         return Vec::new();
@@ -1444,13 +1462,35 @@ pub fn run_cargo(
         };
         for filename in filenames {
             // Skip files like executables
-            if !(filename.ends_with(".rlib")
-                || filename.ends_with(".lib")
+            let mut keep = false;
+            if filename.ends_with(".lib")
                 || filename.ends_with(".a")
                 || is_debug_info(&filename)
                 || is_dylib(&filename)
-                || (is_check && filename.ends_with(".rmeta")))
             {
+                // Always keep native libraries, rust dylibs and debuginfo
+                keep = true;
+            }
+            if is_check && filename.ends_with(".rmeta") {
+                // During check builds we need to keep crate metadata
+                keep = true;
+            } else if rlib_only_metadata {
+                if filename.contains("jemalloc_sys") || filename.contains("rustc_smir") {
+                    // jemalloc_sys and rustc_smir are not linked into librustc_driver.so,
+                    // so we need to distribute them as rlib to be able to use them.
+                    keep |= filename.ends_with(".rlib");
+                } else {
+                    // Distribute the rest of the rustc crates as rmeta files only to reduce
+                    // the tarball sizes by about 50%. The object files are linked into
+                    // librustc_driver.so, so it is still possible to link against them.
+                    keep |= filename.ends_with(".rmeta");
+                }
+            } else {
+                // In all other cases keep all rlibs
+                keep |= filename.ends_with(".rlib");
+            }
+
+            if !keep {
                 continue;
             }
 
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index d8c15c76e..b41d60d51 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -3,6 +3,9 @@
 //! This module implements parsing `config.toml` configuration files to tweak
 //! how the build runs.
 
+#[cfg(test)]
+mod tests;
+
 use std::cell::{Cell, RefCell};
 use std::cmp;
 use std::collections::{HashMap, HashSet};
@@ -46,10 +49,7 @@ pub enum DryRun {
 
 /// Global configuration for the entire build and/or bootstrap.
 ///
-/// This structure is derived from a combination of both `config.toml` and
-/// `config.mk`. As of the time of this writing it's unlikely that `config.toml`
-/// is used all that much, so this is primarily filled out by `config.mk` which
-/// is generated from `./configure`.
+/// This structure is parsed from `config.toml`, and some of the fields are inferred from `git` or build-time parameters.
 ///
 /// Note that this structure is not decoded directly into, but rather it is
 /// filled out from the decoded forms of the structs below. For documentation
@@ -635,6 +635,7 @@ define_config! {
         dist_stage: Option<u32> = "dist-stage",
         bench_stage: Option<u32> = "bench-stage",
         patch_binaries_for_nix: Option<bool> = "patch-binaries-for-nix",
+        // NOTE: only parsed by bootstrap.py, `--feature build-metrics` enables metrics unconditionally
         metrics: Option<bool> = "metrics",
     }
 }
@@ -696,7 +697,7 @@ define_config! {
     }
 }
 
-#[derive(Deserialize)]
+#[derive(Debug, Deserialize)]
 #[serde(untagged)]
 enum StringOrBool {
     String(String),
@@ -822,6 +823,29 @@ impl Config {
     }
 
     pub fn parse(args: &[String]) -> Config {
+        #[cfg(test)]
+        let get_toml = |_: &_| TomlConfig::default();
+        #[cfg(not(test))]
+        let get_toml = |file: &Path| {
+            let contents =
+                t!(fs::read_to_string(file), format!("config file {} not found", file.display()));
+            // Deserialize to Value and then TomlConfig to prevent the Deserialize impl of
+            // TomlConfig and sub types to be monomorphized 5x by toml.
+            match toml::from_str(&contents)
+                .and_then(|table: toml::Value| TomlConfig::deserialize(table))
+            {
+                Ok(table) => table,
+                Err(err) => {
+                    eprintln!("failed to parse TOML configuration '{}': {}", file.display(), err);
+                    crate::detail_exit(2);
+                }
+            }
+        };
+
+        Self::parse_inner(args, get_toml)
+    }
+
+    fn parse_inner<'a>(args: &[String], get_toml: impl 'a + Fn(&Path) -> TomlConfig) -> Config {
         let flags = Flags::parse(&args);
         let mut config = Config::default_opts();
 
@@ -907,25 +931,6 @@ impl Config {
 
         config.stage0_metadata = t!(serde_json::from_slice::<Stage0Metadata>(&stage0_json));
 
-        #[cfg(test)]
-        let get_toml = |_| TomlConfig::default();
-        #[cfg(not(test))]
-        let get_toml = |file: &Path| {
-            let contents =
-                t!(fs::read_to_string(file), format!("config file {} not found", file.display()));
-            // Deserialize to Value and then TomlConfig to prevent the Deserialize impl of
-            // TomlConfig and sub types to be monomorphized 5x by toml.
-            match toml::from_str(&contents)
-                .and_then(|table: toml::Value| TomlConfig::deserialize(table))
-            {
-                Ok(table) => table,
-                Err(err) => {
-                    eprintln!("failed to parse TOML configuration '{}': {}", file.display(), err);
-                    crate::detail_exit(2);
-                }
-            }
-        };
-
         // Read from `--config`, then `RUST_BOOTSTRAP_CONFIG`, then `./config.toml`, then `config.toml` in the root directory.
         let toml_path = flags
             .config
@@ -1063,6 +1068,79 @@ impl Config {
         let mut optimize = None;
         let mut ignore_git = None;
 
+        if let Some(rust) = toml.rust {
+            debug = rust.debug;
+            debug_assertions = rust.debug_assertions;
+            debug_assertions_std = rust.debug_assertions_std;
+            overflow_checks = rust.overflow_checks;
+            overflow_checks_std = rust.overflow_checks_std;
+            debug_logging = rust.debug_logging;
+            debuginfo_level = rust.debuginfo_level;
+            debuginfo_level_rustc = rust.debuginfo_level_rustc;
+            debuginfo_level_std = rust.debuginfo_level_std;
+            debuginfo_level_tools = rust.debuginfo_level_tools;
+            debuginfo_level_tests = rust.debuginfo_level_tests;
+            config.rust_split_debuginfo = rust
+                .split_debuginfo
+                .as_deref()
+                .map(SplitDebuginfo::from_str)
+                .map(|v| v.expect("invalid value for rust.split_debuginfo"))
+                .unwrap_or(SplitDebuginfo::default_for_platform(&config.build.triple));
+            optimize = rust.optimize;
+            ignore_git = rust.ignore_git;
+            config.rust_new_symbol_mangling = rust.new_symbol_mangling;
+            set(&mut config.rust_optimize_tests, rust.optimize_tests);
+            set(&mut config.codegen_tests, rust.codegen_tests);
+            set(&mut config.rust_rpath, rust.rpath);
+            set(&mut config.jemalloc, rust.jemalloc);
+            set(&mut config.test_compare_mode, rust.test_compare_mode);
+            set(&mut config.backtrace, rust.backtrace);
+            set(&mut config.channel, rust.channel);
+            config.description = rust.description;
+            set(&mut config.rust_dist_src, rust.dist_src);
+            set(&mut config.verbose_tests, rust.verbose_tests);
+            // in the case "false" is set explicitly, do not overwrite the command line args
+            if let Some(true) = rust.incremental {
+                config.incremental = true;
+            }
+            set(&mut config.use_lld, rust.use_lld);
+            set(&mut config.lld_enabled, rust.lld);
+            set(&mut config.llvm_tools_enabled, rust.llvm_tools);
+            config.rustc_parallel = rust.parallel_compiler.unwrap_or(false);
+            config.rustc_default_linker = rust.default_linker;
+            config.musl_root = rust.musl_root.map(PathBuf::from);
+            config.save_toolstates = rust.save_toolstates.map(PathBuf::from);
+            set(&mut config.deny_warnings, flags.deny_warnings.or(rust.deny_warnings));
+            set(&mut config.backtrace_on_ice, rust.backtrace_on_ice);
+            set(&mut config.rust_verify_llvm_ir, rust.verify_llvm_ir);
+            config.rust_thin_lto_import_instr_limit = rust.thin_lto_import_instr_limit;
+            set(&mut config.rust_remap_debuginfo, rust.remap_debuginfo);
+            set(&mut config.control_flow_guard, rust.control_flow_guard);
+            config.llvm_libunwind_default = rust
+                .llvm_libunwind
+                .map(|v| v.parse().expect("failed to parse rust.llvm-libunwind"));
+
+            if let Some(ref backends) = rust.codegen_backends {
+                config.rust_codegen_backends =
+                    backends.iter().map(|s| INTERNER.intern_str(s)).collect();
+            }
+
+            config.rust_codegen_units = rust.codegen_units.map(threads_from_config);
+            config.rust_codegen_units_std = rust.codegen_units_std.map(threads_from_config);
+            config.rust_profile_use = flags.rust_profile_use.or(rust.profile_use);
+            config.rust_profile_generate = flags.rust_profile_generate.or(rust.profile_generate);
+            config.download_rustc_commit = config.download_ci_rustc_commit(rust.download_rustc);
+
+            config.rust_lto = rust
+                .lto
+                .as_deref()
+                .map(|value| RustcLto::from_str(value).unwrap())
+                .unwrap_or_default();
+        } else {
+            config.rust_profile_use = flags.rust_profile_use;
+            config.rust_profile_generate = flags.rust_profile_generate;
+        }
+
         if let Some(llvm) = toml.llvm {
             match llvm.ccache {
                 Some(StringOrBool::String(ref s)) => config.ccache = Some(s.to_string()),
@@ -1099,13 +1177,17 @@ impl Config {
             config.llvm_polly = llvm.polly.unwrap_or(false);
             config.llvm_clang = llvm.clang.unwrap_or(false);
             config.llvm_build_config = llvm.build_config.clone().unwrap_or(Default::default());
+
+            let asserts = llvm_assertions.unwrap_or(false);
             config.llvm_from_ci = match llvm.download_ci_llvm {
                 Some(StringOrBool::String(s)) => {
                     assert!(s == "if-available", "unknown option `{}` for download-ci-llvm", s);
-                    crate::native::is_ci_llvm_available(&config, llvm_assertions.unwrap_or(false))
+                    crate::native::is_ci_llvm_available(&config, asserts)
                 }
                 Some(StringOrBool::Bool(b)) => b,
-                None => false,
+                None => {
+                    config.channel == "dev" && crate::native::is_ci_llvm_available(&config, asserts)
+                }
             };
 
             if config.llvm_from_ci {
@@ -1145,79 +1227,9 @@ impl Config {
                 // the link step) with each stage.
                 config.llvm_link_shared.set(Some(true));
             }
-        }
-
-        if let Some(rust) = toml.rust {
-            debug = rust.debug;
-            debug_assertions = rust.debug_assertions;
-            debug_assertions_std = rust.debug_assertions_std;
-            overflow_checks = rust.overflow_checks;
-            overflow_checks_std = rust.overflow_checks_std;
-            debug_logging = rust.debug_logging;
-            debuginfo_level = rust.debuginfo_level;
-            debuginfo_level_rustc = rust.debuginfo_level_rustc;
-            debuginfo_level_std = rust.debuginfo_level_std;
-            debuginfo_level_tools = rust.debuginfo_level_tools;
-            debuginfo_level_tests = rust.debuginfo_level_tests;
-            config.rust_split_debuginfo = rust
-                .split_debuginfo
-                .as_deref()
-                .map(SplitDebuginfo::from_str)
-                .map(|v| v.expect("invalid value for rust.split_debuginfo"))
-                .unwrap_or(SplitDebuginfo::default_for_platform(&config.build.triple));
-            optimize = rust.optimize;
-            ignore_git = rust.ignore_git;
-            config.rust_new_symbol_mangling = rust.new_symbol_mangling;
-            set(&mut config.rust_optimize_tests, rust.optimize_tests);
-            set(&mut config.codegen_tests, rust.codegen_tests);
-            set(&mut config.rust_rpath, rust.rpath);
-            set(&mut config.jemalloc, rust.jemalloc);
-            set(&mut config.test_compare_mode, rust.test_compare_mode);
-            set(&mut config.backtrace, rust.backtrace);
-            set(&mut config.channel, rust.channel);
-            config.description = rust.description;
-            set(&mut config.rust_dist_src, rust.dist_src);
-            set(&mut config.verbose_tests, rust.verbose_tests);
-            // in the case "false" is set explicitly, do not overwrite the command line args
-            if let Some(true) = rust.incremental {
-                config.incremental = true;
-            }
-            set(&mut config.use_lld, rust.use_lld);
-            set(&mut config.lld_enabled, rust.lld);
-            set(&mut config.llvm_tools_enabled, rust.llvm_tools);
-            config.rustc_parallel = rust.parallel_compiler.unwrap_or(false);
-            config.rustc_default_linker = rust.default_linker;
-            config.musl_root = rust.musl_root.map(PathBuf::from);
-            config.save_toolstates = rust.save_toolstates.map(PathBuf::from);
-            set(&mut config.deny_warnings, flags.deny_warnings.or(rust.deny_warnings));
-            set(&mut config.backtrace_on_ice, rust.backtrace_on_ice);
-            set(&mut config.rust_verify_llvm_ir, rust.verify_llvm_ir);
-            config.rust_thin_lto_import_instr_limit = rust.thin_lto_import_instr_limit;
-            set(&mut config.rust_remap_debuginfo, rust.remap_debuginfo);
-            set(&mut config.control_flow_guard, rust.control_flow_guard);
-            config.llvm_libunwind_default = rust
-                .llvm_libunwind
-                .map(|v| v.parse().expect("failed to parse rust.llvm-libunwind"));
-
-            if let Some(ref backends) = rust.codegen_backends {
-                config.rust_codegen_backends =
-                    backends.iter().map(|s| INTERNER.intern_str(s)).collect();
-            }
-
-            config.rust_codegen_units = rust.codegen_units.map(threads_from_config);
-            config.rust_codegen_units_std = rust.codegen_units_std.map(threads_from_config);
-            config.rust_profile_use = flags.rust_profile_use.or(rust.profile_use);
-            config.rust_profile_generate = flags.rust_profile_generate.or(rust.profile_generate);
-            config.download_rustc_commit = config.download_ci_rustc_commit(rust.download_rustc);
-
-            config.rust_lto = rust
-                .lto
-                .as_deref()
-                .map(|value| RustcLto::from_str(value).unwrap())
-                .unwrap_or_default();
         } else {
-            config.rust_profile_use = flags.rust_profile_use;
-            config.rust_profile_generate = flags.rust_profile_generate;
+            config.llvm_from_ci =
+                config.channel == "dev" && crate::native::is_ci_llvm_available(&config, false);
         }
 
         if let Some(t) = toml.target {
@@ -1596,6 +1608,10 @@ impl Config {
         self.submodules.unwrap_or(rust_info.is_managed_git_subrepository())
     }
 
+    pub fn default_codegen_backend(&self) -> Option<Interned<String>> {
+        self.rust_codegen_backends.get(0).cloned()
+    }
+
     /// Returns the commit to download, or `None` if we shouldn't download CI artifacts.
     fn download_ci_rustc_commit(&self, download_rustc: Option<StringOrBool>) -> Option<String> {
         // If `download-rustc` is not set, default to rebuilding.
diff --git a/src/bootstrap/config/tests.rs b/src/bootstrap/config/tests.rs
new file mode 100644
index 000000000..c30c91317
--- /dev/null
+++ b/src/bootstrap/config/tests.rs
@@ -0,0 +1,24 @@
+use super::{Config, TomlConfig};
+use std::path::Path;
+
+fn toml(config: &str) -> impl '_ + Fn(&Path) -> TomlConfig {
+    |&_| toml::from_str(config).unwrap()
+}
+
+fn parse(config: &str) -> Config {
+    Config::parse_inner(&["check".to_owned(), "--config=/does/not/exist".to_owned()], toml(config))
+}
+
+#[test]
+fn download_ci_llvm() {
+    let parse_llvm = |s| parse(s).llvm_from_ci;
+    let if_available = parse_llvm("llvm.download-ci-llvm = \"if-available\"");
+
+    assert!(parse_llvm("llvm.download-ci-llvm = true"));
+    assert!(!parse_llvm("llvm.download-ci-llvm = false"));
+    assert_eq!(parse_llvm(""), if_available);
+    assert_eq!(parse_llvm("rust.channel = \"dev\""), if_available);
+    assert!(!parse_llvm("rust.channel = \"stable\""));
+}
+
+// FIXME: add test for detecting `src` and `out`
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index 6b139decb..0af329e70 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -45,7 +45,7 @@ o("llvm-static-stdcpp", "llvm.static-libstdcpp", "statically link to libstdc++ f
 o("llvm-link-shared", "llvm.link-shared", "prefer shared linking to LLVM (llvm-config --link-shared)")
 o("rpath", "rust.rpath", "build rpaths into rustc itself")
 o("llvm-version-check", "llvm.version-check", "check if the LLVM version is supported, build anyway")
-o("codegen-tests", "rust.codegen-tests", "run the src/test/codegen tests")
+o("codegen-tests", "rust.codegen-tests", "run the tests/codegen tests")
 o("option-checking", None, "complain about unrecognized options in this configure script")
 o("ninja", "llvm.ninja", "build LLVM using the Ninja generator (for MSVC, requires building in the correct environment)")
 o("locked-deps", "build.locked-deps", "force Cargo.lock to be up to date")
@@ -405,7 +405,9 @@ if 'target' in config:
         configured_targets.append(target)
 for target in configured_targets:
     targets[target] = sections['target'][:]
-    targets[target][0] = targets[target][0].replace("x86_64-unknown-linux-gnu", "'{}'".format(target))
+    # For `.` to be valid TOML, it needs to be quoted. But `bootstrap.py` doesn't use a proper TOML parser and fails to parse the target.
+    # Avoid using quotes unless it's necessary.
+    targets[target][0] = targets[target][0].replace("x86_64-unknown-linux-gnu", "'{}'".format(target) if "." in target else target)
 
 
 def is_number(value):
diff --git a/src/bootstrap/defaults/config.user.toml b/src/bootstrap/defaults/config.user.toml
index 6647061d8..48ae2fe44 100644
--- a/src/bootstrap/defaults/config.user.toml
+++ b/src/bootstrap/defaults/config.user.toml
@@ -7,3 +7,7 @@ test-stage = 2
 doc-stage = 2
 # When compiling from source, you usually want all tools.
 extended = true
+
+[llvm]
+# Most users installing from source want to build all parts of the project from source, not just rustc itself.
+download-ci-llvm = false
diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index 3cb0eccd3..6594b23c5 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -24,6 +24,7 @@ use crate::channel;
 use crate::compile;
 use crate::config::TargetSelection;
 use crate::doc::DocumentationFormat;
+use crate::native;
 use crate::tarball::{GeneratedTarball, OverlayKind, Tarball};
 use crate::tool::{self, Tool};
 use crate::util::{exe, is_dylib, output, t, timeit};
@@ -951,7 +952,7 @@ impl Step for PlainSourceTarball {
             "Cargo.toml",
             "Cargo.lock",
         ];
-        let src_dirs = ["src", "compiler", "library"];
+        let src_dirs = ["src", "compiler", "library", "tests"];
 
         copy_src_dirs(builder, &builder.src, &src_dirs, &[], &plain_dst_src);
 
@@ -1129,12 +1130,6 @@ impl Step for RustAnalyzer {
         let compiler = self.compiler;
         let target = self.target;
 
-        if target.contains("riscv64") {
-            // riscv64 currently has an LLVM bug that makes rust-analyzer unable
-            // to build. See #74813 for details.
-            return None;
-        }
-
         let rust_analyzer = builder
             .ensure(tool::RustAnalyzer { compiler, target })
             .expect("rust-analyzer always builds");
@@ -1927,7 +1922,9 @@ fn maybe_install_llvm(builder: &Builder<'_>, target: TargetSelection, dst_libdir
             builder.install(&llvm_dylib_path, dst_libdir, 0o644);
         }
         !builder.config.dry_run()
-    } else if let Ok(llvm_config) = crate::native::prebuilt_llvm_config(builder, target) {
+    } else if let Ok(native::LlvmResult { llvm_config, .. }) =
+        native::prebuilt_llvm_config(builder, target)
+    {
         let mut cmd = Command::new(llvm_config);
         cmd.arg("--libfiles");
         builder.verbose(&format!("running {:?}", cmd));
@@ -2064,6 +2061,9 @@ impl Step for RustDev {
 
         builder.ensure(crate::native::Llvm { target });
 
+        // We want to package `lld` to use it with `download-ci-llvm`.
+        builder.ensure(crate::native::Lld { target });
+
         let src_bindir = builder.llvm_out(target).join("bin");
         // If updating this list, you likely want to change
         // src/bootstrap/download-ci-llvm-stamp as well, otherwise local users
@@ -2137,7 +2137,7 @@ impl Step for Bootstrap {
         let tarball = Tarball::new(builder, "bootstrap", &target.triple);
 
         let bootstrap_outdir = &builder.bootstrap_out;
-        for file in &["bootstrap", "llvm-config-wrapper", "rustc", "rustdoc", "sccache-plus-cl"] {
+        for file in &["bootstrap", "rustc", "rustdoc", "sccache-plus-cl"] {
             tarball.add_file(bootstrap_outdir.join(exe(file, target)), "bootstrap/bin", 0o755);
         }
 
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 2c6fd1e1d..9bad9046e 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -12,6 +12,7 @@ use std::fs;
 use std::io;
 use std::path::{Path, PathBuf};
 
+use crate::builder::crate_description;
 use crate::builder::{Builder, Compiler, Kind, RunConfig, ShouldRun, Step};
 use crate::cache::{Interned, INTERNER};
 use crate::compile;
@@ -506,7 +507,11 @@ impl Step for Std {
         // Look for library/std, library/core etc in the `x.py doc` arguments and
         // open the corresponding rendered docs.
         for requested_crate in requested_crates {
-            if STD_PUBLIC_CRATES.iter().any(|k| *k == requested_crate.as_str()) {
+            if requested_crate == "library" {
+                // For `x.py doc library --open`, open `std` by default.
+                let index = out.join("std").join("index.html");
+                builder.open_in_browser(index);
+            } else if STD_PUBLIC_CRATES.iter().any(|&k| k == requested_crate) {
                 let index = out.join(requested_crate).join("index.html");
                 builder.open_in_browser(index);
             }
@@ -554,7 +559,8 @@ fn doc_std(
     requested_crates: &[String],
 ) {
     builder.info(&format!(
-        "Documenting stage{} std ({}) in {} format",
+        "Documenting{} stage{} library ({}) in {} format",
+        crate_description(requested_crates),
         stage,
         target,
         format.as_str()
@@ -729,7 +735,7 @@ impl Step for Rustc {
 }
 
 macro_rules! tool_doc {
-    ($tool: ident, $should_run: literal, $path: literal, [$($krate: literal),+ $(,)?] $(,)?) => {
+    ($tool: ident, $should_run: literal, $path: literal, $(rustc_tool = $rustc_tool:literal, )? $(in_tree = $in_tree:literal, )? [$($krate: literal),+ $(,)?] $(,)?) => {
         #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
         pub struct $tool {
             target: TargetSelection,
@@ -763,13 +769,24 @@ macro_rules! tool_doc {
                 let out = builder.compiler_doc_out(target);
                 t!(fs::create_dir_all(&out));
 
-                // Build rustc docs so that we generate relative links.
-                builder.ensure(Rustc { stage, target });
-                // Rustdoc needs the rustc sysroot available to build.
-                // FIXME: is there a way to only ensure `check::Rustc` here? Last time I tried it failed
-                // with strange errors, but only on a full bors test ...
                 let compiler = builder.compiler(stage, builder.config.build);
-                builder.ensure(compile::Rustc::new(compiler, target));
+                builder.ensure(compile::Std::new(compiler, target));
+
+                if true $(&& $rustc_tool)? {
+                    // Build rustc docs so that we generate relative links.
+                    builder.ensure(Rustc { stage, target });
+
+                    // Rustdoc needs the rustc sysroot available to build.
+                    // FIXME: is there a way to only ensure `check::Rustc` here? Last time I tried it failed
+                    // with strange errors, but only on a full bors test ...
+                    builder.ensure(compile::Rustc::new(compiler, target));
+                }
+
+                let source_type = if true $(&& $in_tree)? {
+                    SourceType::InTree
+                } else {
+                    SourceType::Submodule
+                };
 
                 builder.info(
                     &format!(
@@ -781,9 +798,15 @@ macro_rules! tool_doc {
                 );
 
                 // Symlink compiler docs to the output directory of rustdoc documentation.
-                let out_dir = builder.stage_out(compiler, Mode::ToolRustc).join(target.triple).join("doc");
-                t!(fs::create_dir_all(&out_dir));
-                t!(symlink_dir_force(&builder.config, &out, &out_dir));
+                let out_dirs = [
+                    builder.stage_out(compiler, Mode::ToolRustc).join(target.triple).join("doc"),
+                    // Cargo uses a different directory for proc macros.
+                    builder.stage_out(compiler, Mode::ToolRustc).join("doc"),
+                ];
+                for out_dir in out_dirs {
+                    t!(fs::create_dir_all(&out_dir));
+                    t!(symlink_dir_force(&builder.config, &out, &out_dir));
+                }
 
                 // Build cargo command.
                 let mut cargo = prepare_tool_cargo(
@@ -793,7 +816,7 @@ macro_rules! tool_doc {
                     target,
                     "doc",
                     $path,
-                    SourceType::InTree,
+                    source_type,
                     &[],
                 );
 
@@ -824,6 +847,30 @@ tool_doc!(
 );
 tool_doc!(Clippy, "clippy", "src/tools/clippy", ["clippy_utils"]);
 tool_doc!(Miri, "miri", "src/tools/miri", ["miri"]);
+tool_doc!(
+    Cargo,
+    "cargo",
+    "src/tools/cargo",
+    rustc_tool = false,
+    in_tree = false,
+    [
+        "cargo",
+        "cargo-platform",
+        "cargo-util",
+        "crates-io",
+        "cargo-test-macro",
+        "cargo-test-support",
+        "cargo-credential",
+        "cargo-credential-1password",
+        "mdman",
+        // FIXME: this trips a license check in tidy.
+        // "resolver-tests",
+        // FIXME: we should probably document these, but they're different per-platform so we can't use `tool_doc`.
+        // "cargo-credential-gnome-secret",
+        // "cargo-credential-macos-keychain",
+        // "cargo-credential-wincred",
+    ]
+);
 
 #[derive(Ord, PartialOrd, Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct ErrorIndex {
diff --git a/src/bootstrap/download-ci-llvm-stamp b/src/bootstrap/download-ci-llvm-stamp
index d19a1ae95..94630e40f 100644
--- a/src/bootstrap/download-ci-llvm-stamp
+++ b/src/bootstrap/download-ci-llvm-stamp
@@ -1,4 +1,4 @@
 Change this file to make users of the `download-ci-llvm` configuration download
 a new version of LLVM from CI, even if the LLVM submodule hasn’t changed.
 
-Last change is for: https://github.com/rust-lang/rust/pull/102790
+Last change is for: https://github.com/rust-lang/rust/pull/104748
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index 37a8eb884..52c3dc0bf 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -130,6 +130,7 @@ pub enum Subcommand {
         test_args: Vec<String>,
     },
     Clean {
+        paths: Vec<PathBuf>,
         all: bool,
     },
     Dist {
@@ -143,7 +144,7 @@ pub enum Subcommand {
         args: Vec<String>,
     },
     Setup {
-        profile: Option<Profile>,
+        profile: Option<PathBuf>,
     },
 }
 
@@ -351,22 +352,32 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
 
         // fn usage()
         let usage = |exit_code: i32, opts: &Options, verbose: bool, subcommand_help: &str| -> ! {
-            let config = Config::parse(&["build".to_string()]);
-            let build = Build::new(config);
-            let paths = Builder::get_help(&build, subcommand);
-
             println!("{}", opts.usage(subcommand_help));
-            if let Some(s) = paths {
-                if verbose {
+            if verbose {
+                // We have an unfortunate situation here: some Steps use `builder.in_tree_crates` to determine their paths.
+                // To determine those crates, we need to run `cargo metadata`, which means we need all submodules to be checked out.
+                // That takes a while to run, so only do it when paths were explicitly requested, not on all CLI errors.
+                // `Build::new` won't load submodules for the `setup` command.
+                let cmd = if verbose {
+                    println!("note: updating submodules before printing available paths");
+                    "build"
+                } else {
+                    "setup"
+                };
+                let config = Config::parse(&[cmd.to_string()]);
+                let build = Build::new(config);
+                let paths = Builder::get_help(&build, subcommand);
+
+                if let Some(s) = paths {
                     println!("{}", s);
                 } else {
-                    println!(
-                        "Run `./x.py {} -h -v` to see a list of available paths.",
-                        subcommand.as_str()
-                    );
+                    panic!("No paths available for subcommand `{}`", subcommand.as_str());
                 }
-            } else if verbose {
-                panic!("No paths available for subcommand `{}`", subcommand.as_str());
+            } else {
+                println!(
+                    "Run `./x.py {} -h -v` to see a list of available paths.",
+                    subcommand.as_str()
+                );
             }
             crate::detail_exit(exit_code);
         };
@@ -476,13 +487,13 @@ Arguments:
     This subcommand accepts a number of paths to test directories that
     should be compiled and run. For example:
 
-        ./x.py test src/test/ui
+        ./x.py test tests/ui
         ./x.py test library/std --test-args hash_map
         ./x.py test library/std --stage 0 --no-doc
-        ./x.py test src/test/ui --bless
-        ./x.py test src/test/ui --compare-mode chalk
+        ./x.py test tests/ui --bless
+        ./x.py test tests/ui --compare-mode chalk
 
-    Note that `test src/test/* --stage N` does NOT depend on `build compiler/rustc --stage N`;
+    Note that `test tests/* --stage N` does NOT depend on `build compiler/rustc --stage N`;
     just like `build library/std --stage N` it tests the compiler produced by the previous
     stage.
 
@@ -601,14 +612,7 @@ Arguments:
                 open: matches.opt_present("open"),
                 json: matches.opt_present("json"),
             },
-            Kind::Clean => {
-                if !paths.is_empty() {
-                    println!("\nclean does not take a path argument\n");
-                    usage(1, &opts, verbose, &subcommand_help);
-                }
-
-                Subcommand::Clean { all: matches.opt_present("all") }
-            }
+            Kind::Clean => Subcommand::Clean { all: matches.opt_present("all"), paths },
             Kind::Format => Subcommand::Format { check: matches.opt_present("check"), paths },
             Kind::Dist => Subcommand::Dist { paths },
             Kind::Install => Subcommand::Install { paths },
@@ -621,7 +625,7 @@ Arguments:
             }
             Kind::Setup => {
                 let profile = if paths.len() > 1 {
-                    println!("\nat most one profile can be passed to setup\n");
+                    eprintln!("\nerror: At most one profile can be passed to setup\n");
                     usage(1, &opts, verbose, &subcommand_help)
                 } else if let Some(path) = paths.pop() {
                     let profile_string = t!(path.into_os_string().into_string().map_err(
diff --git a/src/bootstrap/format.rs b/src/bootstrap/format.rs
index 5e7264fe7..bfc57a85c 100644
--- a/src/bootstrap/format.rs
+++ b/src/bootstrap/format.rs
@@ -1,14 +1,15 @@
 //! Runs rustfmt on the repository.
 
 use crate::builder::Builder;
-use crate::util::{output, t};
+use crate::util::{output, output_result, program_out_of_date, t};
+use build_helper::git::updated_master_branch;
 use ignore::WalkBuilder;
 use std::collections::VecDeque;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use std::sync::mpsc::SyncSender;
 
-fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl FnMut() {
+fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl FnMut(bool) -> bool {
     let mut cmd = Command::new(&rustfmt);
     // avoid the submodule config paths from coming into play,
     // we only allow a single global config for the workspace for now
@@ -23,7 +24,13 @@ fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl F
     let cmd_debug = format!("{:?}", cmd);
     let mut cmd = cmd.spawn().expect("running rustfmt");
     // poor man's async: return a closure that'll wait for rustfmt's completion
-    move || {
+    move |block: bool| -> bool {
+        if !block {
+            match cmd.try_wait() {
+                Ok(Some(_)) => {}
+                _ => return false,
+            }
+        }
         let status = cmd.wait().unwrap();
         if !status.success() {
             eprintln!(
@@ -34,7 +41,62 @@ fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl F
             );
             crate::detail_exit(1);
         }
+        true
+    }
+}
+
+fn get_rustfmt_version(build: &Builder<'_>) -> Option<(String, PathBuf)> {
+    let stamp_file = build.out.join("rustfmt.stamp");
+
+    let mut cmd = Command::new(match build.initial_rustfmt() {
+        Some(p) => p,
+        None => return None,
+    });
+    cmd.arg("--version");
+    let output = match cmd.output() {
+        Ok(status) => status,
+        Err(_) => return None,
+    };
+    if !output.status.success() {
+        return None;
+    }
+    Some((String::from_utf8(output.stdout).unwrap(), stamp_file))
+}
+
+/// Return whether the format cache can be reused.
+fn verify_rustfmt_version(build: &Builder<'_>) -> bool {
+    let Some((version, stamp_file)) = get_rustfmt_version(build) else {return false;};
+    !program_out_of_date(&stamp_file, &version)
+}
+
+/// Updates the last rustfmt version used
+fn update_rustfmt_version(build: &Builder<'_>) {
+    let Some((version, stamp_file)) = get_rustfmt_version(build) else {return;};
+    t!(std::fs::write(stamp_file, version))
+}
+
+/// Returns the Rust files modified between the `merge-base` of HEAD and
+/// rust-lang/master and what is now on the disk.
+///
+/// Returns `None` if all files should be formatted.
+fn get_modified_rs_files(build: &Builder<'_>) -> Result<Option<Vec<String>>, String> {
+    let Ok(updated_master) = updated_master_branch(Some(&build.config.src)) else { return Ok(None); };
+
+    if !verify_rustfmt_version(build) {
+        return Ok(None);
     }
+
+    let merge_base =
+        output_result(build.config.git().arg("merge-base").arg(&updated_master).arg("HEAD"))?;
+    Ok(Some(
+        output_result(
+            build.config.git().arg("diff-index").arg("--name-only").arg(merge_base.trim()),
+        )?
+        .lines()
+        .map(|s| s.trim().to_owned())
+        .filter(|f| Path::new(f).extension().map_or(false, |ext| ext == "rs"))
+        .collect(),
+    ))
 }
 
 #[derive(serde::Deserialize)]
@@ -71,6 +133,9 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
         Ok(status) => status.success(),
         Err(_) => false,
     };
+
+    let mut paths = paths.to_vec();
+
     if git_available {
         let in_working_tree = match build
             .config
@@ -103,12 +168,32 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
                 // preventing the latter from being formatted.
                 ignore_fmt.add(&format!("!/{}", untracked_path)).expect(&untracked_path);
             }
+            if !check && paths.is_empty() {
+                match get_modified_rs_files(build) {
+                    Ok(Some(files)) => {
+                        for file in files {
+                            println!("formatting modified file {file}");
+                            ignore_fmt.add(&format!("/{file}")).expect(&file);
+                        }
+                    }
+                    Ok(None) => {}
+                    Err(err) => {
+                        println!(
+                            "WARN: Something went wrong when running git commands:\n{err}\n\
+                            Falling back to formatting all files."
+                        );
+                        // Something went wrong when getting the version. Just format all the files.
+                        paths.push(".".into());
+                    }
+                }
+            }
         } else {
             println!("Not in git tree. Skipping git-aware format checks");
         }
     } else {
         println!("Could not find usable git. Skipping git-aware format checks");
     }
+
     let ignore_fmt = ignore_fmt.build().unwrap();
 
     let rustfmt_path = build.initial_rustfmt().unwrap_or_else(|| {
@@ -146,15 +231,23 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
             let child = rustfmt(&src, &rustfmt_path, paths.as_slice(), check);
             children.push_back(child);
 
+            // poll completion before waiting
+            for i in (0..children.len()).rev() {
+                if children[i](false) {
+                    children.swap_remove_back(i);
+                    break;
+                }
+            }
+
             if children.len() >= max_processes {
                 // await oldest child
-                children.pop_front().unwrap()();
+                children.pop_front().unwrap()(true);
             }
         }
 
         // await remaining children
         for mut child in children {
-            child();
+            child(true);
         }
     });
 
@@ -172,4 +265,7 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
     drop(tx);
 
     thread.join().unwrap();
+    if !check {
+        update_rustfmt_version(build);
+    }
 }
diff --git a/src/bootstrap/install.rs b/src/bootstrap/install.rs
index 38426f3a4..1815a0973 100644
--- a/src/bootstrap/install.rs
+++ b/src/bootstrap/install.rs
@@ -209,6 +209,12 @@ install!((self, builder, _config),
             );
         }
     };
+    LlvmTools, alias = "llvm-tools", Self::should_build(_config), only_hosts: true, {
+        let tarball = builder
+            .ensure(dist::LlvmTools { target: self.target })
+            .expect("missing llvm-tools");
+        install_sh(builder, "llvm-tools", self.compiler.stage, Some(self.target), &tarball);
+    };
     Rustfmt, alias = "rustfmt", Self::should_build(_config), only_hosts: true, {
         if let Some(tarball) = builder.ensure(dist::Rustfmt {
             compiler: self.compiler,
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 3ed534523..0474ab344 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -108,10 +108,12 @@ use std::collections::{HashMap, HashSet};
 use std::env;
 use std::fs::{self, File};
 use std::io;
+use std::io::ErrorKind;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str;
 
+use build_helper::ci::CiEnv;
 use channel::GitInfo;
 use config::{DryRun, Target};
 use filetime::FileTime;
@@ -119,7 +121,9 @@ use once_cell::sync::OnceCell;
 
 use crate::builder::Kind;
 use crate::config::{LlvmLibunwind, TargetSelection};
-use crate::util::{exe, libdir, mtime, output, run, run_suppressed, try_run_suppressed, CiEnv};
+use crate::util::{
+    exe, libdir, mtime, output, run, run_suppressed, symlink_dir, try_run_suppressed,
+};
 
 mod bolt;
 mod builder;
@@ -199,6 +203,7 @@ const EXTRA_CHECK_CFGS: &[(Option<Mode>, &'static str, Option<&[&'static str]>)]
     (None, "bootstrap", None),
     (Some(Mode::Rustc), "parallel_compiler", None),
     (Some(Mode::ToolRustc), "parallel_compiler", None),
+    (Some(Mode::ToolRustc), "emulate_second_only_system", None),
     (Some(Mode::Codegen), "parallel_compiler", None),
     (Some(Mode::Std), "stdarch_intel_sde", None),
     (Some(Mode::Std), "no_fp_fmt_parse", None),
@@ -586,6 +591,21 @@ impl Build {
             metadata::build(&mut build);
         }
 
+        // Make a symbolic link so we can use a consistent directory in the documentation.
+        let build_triple = build.out.join(&build.build.triple);
+        t!(fs::create_dir_all(&build_triple));
+        let host = build.out.join("host");
+        if let Err(e) = symlink_dir(&build.config, &build_triple, &host) {
+            if e.kind() != ErrorKind::AlreadyExists {
+                panic!(
+                    "symlink_dir({} => {}) failed with {}",
+                    host.display(),
+                    build_triple.display(),
+                    e
+                );
+            }
+        }
+
         build
     }
 
@@ -709,14 +729,6 @@ impl Build {
             return format::format(&builder::Builder::new(&self), *check, &paths);
         }
 
-        if let Subcommand::Clean { all } = self.config.cmd {
-            return clean::clean(self, all);
-        }
-
-        if let Subcommand::Setup { profile } = &self.config.cmd {
-            return setup::setup(&self.config, *profile);
-        }
-
         // Download rustfmt early so that it can be used in rust-analyzer configs.
         let _ = &builder::Builder::new(&self).initial_rustfmt();
 
@@ -782,7 +794,7 @@ impl Build {
     /// Gets the space-separated set of activated features for the standard
     /// library.
     fn std_features(&self, target: TargetSelection) -> String {
-        let mut features = "panic-unwind".to_string();
+        let mut features = " panic-unwind".to_string();
 
         match self.config.llvm_libunwind(target) {
             LlvmLibunwind::InTree => features.push_str(" llvm-libunwind"),
@@ -1386,7 +1398,10 @@ impl Build {
         let mut list = vec![INTERNER.intern_str(root)];
         let mut visited = HashSet::new();
         while let Some(krate) = list.pop() {
-            let krate = &self.crates[&krate];
+            let krate = self
+                .crates
+                .get(&krate)
+                .unwrap_or_else(|| panic!("metadata missing for {krate}: {:?}", self.crates));
             ret.push(krate);
             for dep in &krate.deps {
                 if !self.crates.contains_key(dep) {
@@ -1639,10 +1654,10 @@ fn chmod(_path: &Path, _perms: u32) {}
 /// If the test is running and code is an error code, it will cause a panic.
 fn detail_exit(code: i32) -> ! {
     // if in test and code is an error code, panic with status code provided
-    if cfg!(test) && code != 0 {
+    if cfg!(test) {
         panic!("status code: {}", code);
     } else {
-        //otherwise,exit with provided status code
+        // otherwise,exit with provided status code
         std::process::exit(code);
     }
 }
diff --git a/src/bootstrap/mk/Makefile.in b/src/bootstrap/mk/Makefile.in
index 9a08a7be0..d54a21b9f 100644
--- a/src/bootstrap/mk/Makefile.in
+++ b/src/bootstrap/mk/Makefile.in
@@ -57,13 +57,8 @@ tidy:
 prepare:
 	$(Q)$(BOOTSTRAP) build --stage 2 nonexistent/path/to/trigger/cargo/metadata
 
-check-stage2-T-arm-linux-androideabi-H-x86_64-unknown-linux-gnu:
-	$(Q)$(BOOTSTRAP) test --stage 2 --target arm-linux-androideabi
-check-stage2-T-x86_64-unknown-linux-musl-H-x86_64-unknown-linux-gnu:
-	$(Q)$(BOOTSTRAP) test --stage 2 --target x86_64-unknown-linux-musl
-
 TESTS_IN_2 := \
-	src/test/ui \
+	tests/ui \
 	src/tools/linkchecker
 
 ## MSVC native builders
@@ -77,7 +72,7 @@ ci-subset-2:
 ## MingW native builders
 
 TESTS_IN_MINGW_2 := \
-	src/test/ui
+	tests/ui
 
 ci-mingw-subset-1:
 	$(Q)$(CFG_SRC_DIR)/x test --stage 2 $(TESTS_IN_MINGW_2:%=--exclude %)
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index f6c453ebe..e0d1504c9 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -24,9 +24,20 @@ use crate::util::get_clang_cl_resource_dir;
 use crate::util::{self, exe, output, t, up_to_date};
 use crate::{CLang, GitRepo};
 
+use build_helper::ci::CiEnv;
+
+#[derive(Clone)]
+pub struct LlvmResult {
+    /// Path to llvm-config binary.
+    /// NB: This is always the host llvm-config!
+    pub llvm_config: PathBuf,
+    /// Path to LLVM cmake directory for the target.
+    pub llvm_cmake_dir: PathBuf,
+}
+
 pub struct Meta {
     stamp: HashStamp,
-    build_llvm_config: PathBuf,
+    res: LlvmResult,
     out_dir: PathBuf,
     root: String,
 }
@@ -54,17 +65,17 @@ impl LdFlags {
     }
 }
 
-// This returns whether we've already previously built LLVM.
-//
-// It's used to avoid busting caches during x.py check -- if we've already built
-// LLVM, it's fine for us to not try to avoid doing so.
-//
-// This will return the llvm-config if it can get it (but it will not build it
-// if not).
+/// This returns whether we've already previously built LLVM.
+///
+/// It's used to avoid busting caches during x.py check -- if we've already built
+/// LLVM, it's fine for us to not try to avoid doing so.
+///
+/// This will return the llvm-config if it can get it (but it will not build it
+/// if not).
 pub fn prebuilt_llvm_config(
     builder: &Builder<'_>,
     target: TargetSelection,
-) -> Result<PathBuf, Meta> {
+) -> Result<LlvmResult, Meta> {
     builder.config.maybe_download_ci_llvm();
 
     // If we're using a custom LLVM bail out here, but we can only use a
@@ -72,7 +83,14 @@ pub fn prebuilt_llvm_config(
     if let Some(config) = builder.config.target_config.get(&target) {
         if let Some(ref s) = config.llvm_config {
             check_llvm_version(builder, s);
-            return Ok(s.to_path_buf());
+            let llvm_config = s.to_path_buf();
+            let mut llvm_cmake_dir = llvm_config.clone();
+            llvm_cmake_dir.pop();
+            llvm_cmake_dir.pop();
+            llvm_cmake_dir.push("lib");
+            llvm_cmake_dir.push("cmake");
+            llvm_cmake_dir.push("llvm");
+            return Ok(LlvmResult { llvm_config, llvm_cmake_dir });
         }
     }
 
@@ -84,8 +102,9 @@ pub fn prebuilt_llvm_config(
         llvm_config_ret_dir.push("build");
     }
     llvm_config_ret_dir.push("bin");
-
     let build_llvm_config = llvm_config_ret_dir.join(exe("llvm-config", builder.config.build));
+    let llvm_cmake_dir = out_dir.join("lib/cmake/llvm");
+    let res = LlvmResult { llvm_config: build_llvm_config, llvm_cmake_dir };
 
     let stamp = out_dir.join("llvm-finished-building");
     let stamp = HashStamp::new(stamp, builder.in_tree_llvm_info.sha());
@@ -96,7 +115,7 @@ pub fn prebuilt_llvm_config(
                 Using a potentially stale build of LLVM; \
                 This may not behave well.",
         );
-        return Ok(build_llvm_config);
+        return Ok(res);
     }
 
     if stamp.is_done() {
@@ -110,10 +129,10 @@ pub fn prebuilt_llvm_config(
                 stamp.path.display()
             ));
         }
-        return Ok(build_llvm_config);
+        return Ok(res);
     }
 
-    Err(Meta { stamp, build_llvm_config, out_dir, root: root.into() })
+    Err(Meta { stamp, res, out_dir, root: root.into() })
 }
 
 /// This retrieves the LLVM sha we *want* to use, according to git history.
@@ -200,7 +219,7 @@ pub(crate) fn is_ci_llvm_available(config: &Config, asserts: bool) -> bool {
         return false;
     }
 
-    if crate::util::CiEnv::is_ci() {
+    if CiEnv::is_ci() {
         // We assume we have access to git, so it's okay to unconditionally pass
         // `true` here.
         let llvm_sha = detect_llvm_sha(config, true);
@@ -223,7 +242,7 @@ pub struct Llvm {
 }
 
 impl Step for Llvm {
-    type Output = PathBuf; // path to llvm-config
+    type Output = LlvmResult;
 
     const ONLY_HOSTS: bool = true;
 
@@ -236,7 +255,7 @@ impl Step for Llvm {
     }
 
     /// Compile LLVM for `target`.
-    fn run(self, builder: &Builder<'_>) -> PathBuf {
+    fn run(self, builder: &Builder<'_>) -> LlvmResult {
         let target = self.target;
         let target_native = if self.target.starts_with("riscv") {
             // RISC-V target triples in Rust is not named the same as C compiler target triples.
@@ -252,11 +271,10 @@ impl Step for Llvm {
             target.to_string()
         };
 
-        let Meta { stamp, build_llvm_config, out_dir, root } =
-            match prebuilt_llvm_config(builder, target) {
-                Ok(p) => return p,
-                Err(m) => m,
-            };
+        let Meta { stamp, res, out_dir, root } = match prebuilt_llvm_config(builder, target) {
+            Ok(p) => return p,
+            Err(m) => m,
+        };
 
         builder.update_submodule(&Path::new("src").join("llvm-project"));
         if builder.llvm_link_shared() && target.contains("windows") {
@@ -430,7 +448,8 @@ impl Step for Llvm {
 
         // https://llvm.org/docs/HowToCrossCompileLLVM.html
         if target != builder.config.build {
-            let llvm_config = builder.ensure(Llvm { target: builder.config.build });
+            let LlvmResult { llvm_config, .. } =
+                builder.ensure(Llvm { target: builder.config.build });
             if !builder.config.dry_run() {
                 let llvm_bindir = output(Command::new(&llvm_config).arg("--bindir"));
                 let host_bin = Path::new(llvm_bindir.trim());
@@ -480,7 +499,7 @@ impl Step for Llvm {
         //        tools and libs on all platforms.
 
         if builder.config.dry_run() {
-            return build_llvm_config;
+            return res;
         }
 
         cfg.build();
@@ -490,7 +509,7 @@ impl Step for Llvm {
         // for a versioned path like libLLVM-14.dylib. Manually create a symbolic
         // link to make llvm-config happy.
         if builder.llvm_link_shared() && target.contains("apple-darwin") {
-            let mut cmd = Command::new(&build_llvm_config);
+            let mut cmd = Command::new(&res.llvm_config);
             let version = output(cmd.arg("--version"));
             let major = version.split('.').next().unwrap();
             let lib_name = match llvm_version_suffix {
@@ -509,18 +528,18 @@ impl Step for Llvm {
         // LLVM after a configuration change, so to rebuild it the build files have to be removed,
         // which will also remove these modified files.
         if builder.config.llvm_bolt_profile_generate {
-            instrument_with_bolt_inplace(&get_built_llvm_lib_path(&build_llvm_config));
+            instrument_with_bolt_inplace(&get_built_llvm_lib_path(&res.llvm_config));
         }
         if let Some(path) = &builder.config.llvm_bolt_profile_use {
             optimize_library_with_bolt_inplace(
-                &get_built_llvm_lib_path(&build_llvm_config),
+                &get_built_llvm_lib_path(&res.llvm_config),
                 &Path::new(path),
             );
         }
 
         t!(stamp.write());
 
-        build_llvm_config
+        res
     }
 }
 
@@ -600,6 +619,9 @@ fn configure_cmake(
             if target.starts_with("aarch64") {
                 // macOS uses a different name for building arm64
                 cfg.define("CMAKE_OSX_ARCHITECTURES", "arm64");
+            } else if target.starts_with("i686") {
+                // macOS uses a different name for building i386
+                cfg.define("CMAKE_OSX_ARCHITECTURES", "i386");
             } else {
                 cfg.define("CMAKE_OSX_ARCHITECTURES", target.triple.split('-').next().unwrap());
             }
@@ -803,7 +825,21 @@ impl Step for Lld {
         }
         let target = self.target;
 
-        let llvm_config = builder.ensure(Llvm { target: self.target });
+        let LlvmResult { llvm_config, llvm_cmake_dir } = builder.ensure(Llvm { target });
+
+        // The `dist` step packages LLD next to LLVM's binaries for download-ci-llvm. The root path
+        // we usually expect here is `./build/$triple/ci-llvm/`, with the binaries in its `bin`
+        // subfolder. We check if that's the case, and if LLD's binary already exists there next to
+        // `llvm-config`: if so, we can use it instead of building LLVM/LLD from source.
+        let ci_llvm_bin = llvm_config.parent().unwrap();
+        if ci_llvm_bin.is_dir() && ci_llvm_bin.file_name().unwrap() == "bin" {
+            let lld_path = ci_llvm_bin.join(exe("lld", target));
+            if lld_path.exists() {
+                // The following steps copying `lld` as `rust-lld` to the sysroot, expect it in the
+                // `bin` subfolder of this step's out dir.
+                return ci_llvm_bin.parent().unwrap().to_path_buf();
+            }
+        }
 
         let out_dir = builder.lld_out(target);
         let done_stamp = out_dir.join("lld-finished-building");
@@ -834,22 +870,6 @@ impl Step for Lld {
         configure_cmake(builder, target, &mut cfg, true, ldflags);
         configure_llvm(builder, target, &mut cfg);
 
-        // This is an awful, awful hack. Discovered when we migrated to using
-        // clang-cl to compile LLVM/LLD it turns out that LLD, when built out of
-        // tree, will execute `llvm-config --cmakedir` and then tell CMake about
-        // that directory for later processing. Unfortunately if this path has
-        // forward slashes in it (which it basically always does on Windows)
-        // then CMake will hit a syntax error later on as... something isn't
-        // escaped it seems?
-        //
-        // Instead of attempting to fix this problem in upstream CMake and/or
-        // LLVM/LLD we just hack around it here. This thin wrapper will take the
-        // output from llvm-config and replace all instances of `\` with `/` to
-        // ensure we don't hit the same bugs with escaping. It means that you
-        // can't build on a system where your paths require `\` on Windows, but
-        // there's probably a lot of reasons you can't do that other than this.
-        let llvm_config_shim = env::current_exe().unwrap().with_file_name("llvm-config-wrapper");
-
         // Re-use the same flags as llvm to control the level of debug information
         // generated for lld.
         let profile = match (builder.config.llvm_optimize, builder.config.llvm_release_debuginfo) {
@@ -860,36 +880,17 @@ impl Step for Lld {
 
         cfg.out_dir(&out_dir)
             .profile(profile)
-            .env("LLVM_CONFIG_REAL", &llvm_config)
-            .define("LLVM_CONFIG_PATH", llvm_config_shim)
+            .define("LLVM_CMAKE_DIR", llvm_cmake_dir)
             .define("LLVM_INCLUDE_TESTS", "OFF");
 
-        // While we're using this horrible workaround to shim the execution of
-        // llvm-config, let's just pile on more. I can't seem to figure out how
-        // to build LLD as a standalone project and also cross-compile it at the
-        // same time. It wants a natively executable `llvm-config` to learn
-        // about LLVM, but then it learns about all the host configuration of
-        // LLVM and tries to link to host LLVM libraries.
-        //
-        // To work around that we tell our shim to replace anything with the
-        // build target with the actual target instead. This'll break parts of
-        // LLD though which try to execute host tools, such as llvm-tblgen, so
-        // we specifically tell it where to find those. This is likely super
-        // brittle and will break over time. If anyone knows better how to
-        // cross-compile LLD it would be much appreciated to fix this!
         if target != builder.config.build {
-            cfg.env("LLVM_CONFIG_SHIM_REPLACE", &builder.config.build.triple)
-                .env("LLVM_CONFIG_SHIM_REPLACE_WITH", &target.triple)
-                .define(
-                    "LLVM_TABLEGEN_EXE",
-                    llvm_config.with_file_name("llvm-tblgen").with_extension(EXE_EXTENSION),
-                );
+            // Use the host llvm-tblgen binary.
+            cfg.define(
+                "LLVM_TABLEGEN_EXE",
+                llvm_config.with_file_name("llvm-tblgen").with_extension(EXE_EXTENSION),
+            );
         }
 
-        // Explicitly set C++ standard, because upstream doesn't do so
-        // for standalone builds.
-        cfg.define("CMAKE_CXX_STANDARD", "14");
-
         cfg.build();
 
         t!(File::create(&done_stamp));
@@ -906,7 +907,7 @@ impl Step for TestHelpers {
     type Output = ();
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.path("src/test/auxiliary/rust_test_helpers.c")
+        run.path("tests/auxiliary/rust_test_helpers.c")
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -928,7 +929,7 @@ impl Step for TestHelpers {
             self.target
         };
         let dst = builder.test_helpers_out(target);
-        let src = builder.src.join("src/test/auxiliary/rust_test_helpers.c");
+        let src = builder.src.join("tests/auxiliary/rust_test_helpers.c");
         if up_to_date(&src, &dst.join("librust_test_helpers.a")) {
             return;
         }
@@ -957,7 +958,7 @@ impl Step for TestHelpers {
             .opt_level(0)
             .warnings(false)
             .debug(false)
-            .file(builder.src.join("src/test/auxiliary/rust_test_helpers.c"))
+            .file(builder.src.join("tests/auxiliary/rust_test_helpers.c"))
             .compile("rust_test_helpers");
     }
 }
@@ -991,7 +992,7 @@ impl Step for Sanitizers {
             return runtimes;
         }
 
-        let llvm_config = builder.ensure(Llvm { target: builder.config.build });
+        let LlvmResult { llvm_config, .. } = builder.ensure(Llvm { target: builder.config.build });
         if builder.config.dry_run() {
             return runtimes;
         }
@@ -1086,12 +1087,12 @@ fn supported_sanitizers(
 
     match &*target.triple {
         "aarch64-apple-darwin" => darwin_libs("osx", &["asan", "lsan", "tsan"]),
-        "aarch64-fuchsia" => common_libs("fuchsia", "aarch64", &["asan"]),
+        "aarch64-unknown-fuchsia" => common_libs("fuchsia", "aarch64", &["asan"]),
         "aarch64-unknown-linux-gnu" => {
             common_libs("linux", "aarch64", &["asan", "lsan", "msan", "tsan", "hwasan"])
         }
         "x86_64-apple-darwin" => darwin_libs("osx", &["asan", "lsan", "tsan"]),
-        "x86_64-fuchsia" => common_libs("fuchsia", "x86_64", &["asan"]),
+        "x86_64-unknown-fuchsia" => common_libs("fuchsia", "x86_64", &["asan"]),
         "x86_64-unknown-freebsd" => common_libs("freebsd", "x86_64", &["asan", "msan", "tsan"]),
         "x86_64-unknown-netbsd" => {
             common_libs("netbsd", "x86_64", &["asan", "lsan", "msan", "tsan"])
diff --git a/src/bootstrap/run.rs b/src/bootstrap/run.rs
index 05de51f8c..e02808545 100644
--- a/src/bootstrap/run.rs
+++ b/src/bootstrap/run.rs
@@ -105,6 +105,7 @@ impl Step for BumpStage0 {
 
     fn run(self, builder: &Builder<'_>) -> Self::Output {
         let mut cmd = builder.tool_cmd(Tool::BumpStage0);
+        cmd.args(builder.config.cmd.args());
         builder.run(&mut cmd);
     }
 }
diff --git a/src/bootstrap/setup.rs b/src/bootstrap/setup.rs
index c7f98a7d0..004601cb6 100644
--- a/src/bootstrap/setup.rs
+++ b/src/bootstrap/setup.rs
@@ -1,3 +1,4 @@
+use crate::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::Config;
 use crate::{t, VERSION};
 use std::env::consts::EXE_SUFFIX;
@@ -9,7 +10,7 @@ use std::process::Command;
 use std::str::FromStr;
 use std::{fmt, fs, io};
 
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 pub enum Profile {
     Compiler,
     Codegen,
@@ -48,6 +49,16 @@ impl Profile {
         }
         out
     }
+
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Profile::Compiler => "compiler",
+            Profile::Codegen => "codegen",
+            Profile::Library => "library",
+            Profile::Tools => "tools",
+            Profile::User => "user",
+        }
+    }
 }
 
 impl FromStr for Profile {
@@ -69,24 +80,62 @@ impl FromStr for Profile {
 
 impl fmt::Display for Profile {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Profile::Compiler => write!(f, "compiler"),
-            Profile::Codegen => write!(f, "codegen"),
-            Profile::Library => write!(f, "library"),
-            Profile::User => write!(f, "user"),
-            Profile::Tools => write!(f, "tools"),
+        f.write_str(self.as_str())
+    }
+}
+
+impl Step for Profile {
+    type Output = ();
+    const DEFAULT: bool = true;
+
+    fn should_run(mut run: ShouldRun<'_>) -> ShouldRun<'_> {
+        for choice in Profile::all() {
+            run = run.alias(choice.as_str());
         }
+        run
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        if run.builder.config.dry_run() {
+            return;
+        }
+
+        // for Profile, `run.paths` will have 1 and only 1 element
+        // this is because we only accept at most 1 path from user input.
+        // If user calls `x.py setup` without arguments, the interactive TUI
+        // will guide user to provide one.
+        let profile = if run.paths.len() > 1 {
+            // HACK: `builder` runs this step with all paths if no path was passed.
+            t!(interactive_path())
+        } else {
+            run.paths
+                .first()
+                .unwrap()
+                .assert_single_path()
+                .path
+                .as_path()
+                .as_os_str()
+                .to_str()
+                .unwrap()
+                .parse()
+                .unwrap()
+        };
+
+        run.builder.ensure(profile);
+    }
+
+    fn run(self, builder: &Builder<'_>) {
+        setup(&builder.build.config, self)
     }
 }
 
-pub fn setup(config: &Config, profile: Option<Profile>) {
-    let profile = profile.unwrap_or_else(|| t!(interactive_path()));
+pub fn setup(config: &Config, profile: Profile) {
     let stage_path =
         ["build", config.build.rustc_target_arg(), "stage1"].join(&MAIN_SEPARATOR.to_string());
 
     if !rustup_installed() && profile != Profile::User {
         eprintln!("`rustup` is not installed; cannot link `stage1` toolchain");
-    } else if stage_dir_exists(&stage_path[..]) {
+    } else if stage_dir_exists(&stage_path[..]) && !config.dry_run() {
         attempt_toolchain_link(&stage_path[..]);
     }
 
@@ -95,7 +144,7 @@ pub fn setup(config: &Config, profile: Option<Profile>) {
         Profile::Tools => &[
             "check",
             "build",
-            "test src/test/rustdoc*",
+            "test tests/rustdoc*",
             "test src/tools/clippy",
             "test src/tools/miri",
             "test src/tools/rustfmt",
@@ -104,7 +153,9 @@ pub fn setup(config: &Config, profile: Option<Profile>) {
         Profile::User => &["dist", "build"],
     };
 
-    t!(install_git_hook_maybe(&config));
+    if !config.dry_run() {
+        t!(install_git_hook_maybe(&config));
+    }
 
     println!();
 
@@ -144,6 +195,7 @@ fn setup_config_toml(path: &PathBuf, profile: Profile, config: &Config) {
     changelog-seen = {}\n",
         profile, VERSION
     );
+
     t!(fs::write(path, settings));
 
     let include_path = profile.include_path(&config.src);
@@ -299,7 +351,7 @@ pub fn interactive_path() -> io::Result<Profile> {
     Ok(template)
 }
 
-// install a git hook to automatically run tidy --bless, if they want
+// install a git hook to automatically run tidy, if they want
 fn install_git_hook_maybe(config: &Config) -> io::Result<()> {
     let git = t!(config.git().args(&["rev-parse", "--git-common-dir"]).output().map(|output| {
         assert!(output.status.success(), "failed to run `git`");
@@ -315,7 +367,7 @@ fn install_git_hook_maybe(config: &Config) -> io::Result<()> {
     println!();
     println!(
         "Rust's CI will automatically fail if it doesn't pass `tidy`, the internal tool for ensuring code quality.
-If you'd like, x.py can install a git hook for you that will automatically run `tidy --bless` before
+If you'd like, x.py can install a git hook for you that will automatically run `test tidy` before
 pushing your code to ensure your code is up to par. If you decide later that this behavior is
 undesirable, simply delete the `pre-push` file from .git/hooks."
     );
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 39cedfdac..6078e39ac 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -11,6 +11,7 @@ use std::iter;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
+use crate::builder::crate_description;
 use crate::builder::{Builder, Compiler, Kind, RunConfig, ShouldRun, Step};
 use crate::cache::Interned;
 use crate::compile;
@@ -377,6 +378,7 @@ impl Step for RustAnalyzer {
             SourceType::InTree,
             &["sysroot-abi".to_owned()],
         );
+        cargo.allow_features(tool::RustAnalyzer::ALLOW_FEATURES);
 
         let dir = builder.src.join(workspace_path);
         // needed by rust-analyzer to find its own text fixtures, cf.
@@ -689,7 +691,7 @@ impl Step for CompiletestTest {
         // We need `ToolStd` for the locally-built sysroot because
         // compiletest uses unstable features of the `test` crate.
         builder.ensure(compile::Std::new(compiler, host));
-        let cargo = tool::prepare_tool_cargo(
+        let mut cargo = tool::prepare_tool_cargo(
             builder,
             compiler,
             Mode::ToolStd,
@@ -699,6 +701,7 @@ impl Step for CompiletestTest {
             SourceType::InTree,
             &[],
         );
+        cargo.allow_features("test");
 
         try_run(builder, &mut cargo.into());
     }
@@ -840,7 +843,7 @@ impl Step for RustdocJSStd {
     const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.suite_path("src/test/rustdoc-js-std")
+        run.suite_path("tests/rustdoc-js-std")
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -859,10 +862,10 @@ impl Step for RustdocJSStd {
                 .arg("--doc-folder")
                 .arg(builder.doc_out(self.target))
                 .arg("--test-folder")
-                .arg(builder.src.join("src/test/rustdoc-js-std"));
+                .arg(builder.src.join("tests/rustdoc-js-std"));
             for path in &builder.paths {
                 if let Some(p) =
-                    util::is_valid_test_suite_arg(path, "src/test/rustdoc-js-std", builder)
+                    util::is_valid_test_suite_arg(path, "tests/rustdoc-js-std", builder)
                 {
                     if !p.ends_with(".js") {
                         eprintln!("A non-js file was given: `{}`", path.display());
@@ -878,7 +881,7 @@ impl Step for RustdocJSStd {
             });
             builder.run(&mut command);
         } else {
-            builder.info("No nodejs found, skipping \"src/test/rustdoc-js-std\" tests");
+            builder.info("No nodejs found, skipping \"tests/rustdoc-js-std\" tests");
         }
     }
 }
@@ -895,7 +898,7 @@ impl Step for RustdocJSNotStd {
     const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.suite_path("src/test/rustdoc-js")
+        run.suite_path("tests/rustdoc-js")
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -910,11 +913,11 @@ impl Step for RustdocJSNotStd {
                 target: self.target,
                 mode: "js-doc-test",
                 suite: "rustdoc-js",
-                path: "src/test/rustdoc-js",
+                path: "tests/rustdoc-js",
                 compare_mode: None,
             });
         } else {
-            builder.info("No nodejs found, skipping \"src/test/rustdoc-js\" tests");
+            builder.info("No nodejs found, skipping \"tests/rustdoc-js\" tests");
         }
     }
 }
@@ -975,7 +978,7 @@ impl Step for RustdocGUI {
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         let builder = run.builder;
-        let run = run.suite_path("src/test/rustdoc-gui");
+        let run = run.suite_path("tests/rustdoc-gui");
         run.lazy_default_condition(Box::new(move || {
             builder.config.nodejs.is_some()
                 && builder
@@ -1024,7 +1027,7 @@ impl Step for RustdocGUI {
         // We remove existing folder to be sure there won't be artifacts remaining.
         builder.clear_if_dirty(&out_dir, &builder.rustdoc(self.compiler));
 
-        let src_path = builder.build.src.join("src/test/rustdoc-gui/src");
+        let src_path = builder.build.src.join("tests/rustdoc-gui/src");
         // We generate docs for the libraries present in the rustdoc-gui's src folder.
         for entry in src_path.read_dir().expect("read_dir call failed") {
             if let Ok(entry) = entry {
@@ -1048,7 +1051,7 @@ impl Step for RustdocGUI {
                 if entry.file_name() == "link_to_definition" {
                     cargo.env("RUSTDOCFLAGS", "-Zunstable-options --generate-link-to-definition");
                 } else if entry.file_name() == "scrape_examples" {
-                    cargo.arg("-Zrustdoc-scrape-examples=examples");
+                    cargo.arg("-Zrustdoc-scrape-examples");
                 }
                 builder.run(&mut cargo);
             }
@@ -1063,9 +1066,9 @@ impl Step for RustdocGUI {
             .arg("--doc-folder")
             .arg(out_dir.join("doc"))
             .arg("--tests-folder")
-            .arg(builder.build.src.join("src/test/rustdoc-gui"));
+            .arg(builder.build.src.join("tests/rustdoc-gui"));
         for path in &builder.paths {
-            if let Some(p) = util::is_valid_test_suite_arg(path, "src/test/rustdoc-gui", builder) {
+            if let Some(p) = util::is_valid_test_suite_arg(path, "tests/rustdoc-gui", builder) {
                 if !p.ends_with(".goml") {
                     eprintln!("A non-goml file was given: `{}`", path.display());
                     panic!("Cannot run rustdoc-gui tests");
@@ -1142,6 +1145,40 @@ help: to skip test's attempt to check tidiness, pass `--exclude src/tools/tidy`
     }
 }
 
+/// Runs tidy's own tests.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TidySelfTest;
+
+impl Step for TidySelfTest {
+    type Output = ();
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.alias("tidyselftest")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(TidySelfTest);
+    }
+
+    fn run(self, builder: &Builder<'_>) {
+        let bootstrap_host = builder.config.build;
+        let compiler = builder.compiler(0, bootstrap_host);
+        let cargo = tool::prepare_tool_cargo(
+            builder,
+            compiler,
+            Mode::ToolBootstrap,
+            bootstrap_host,
+            "test",
+            "src/tools/tidy",
+            SourceType::InTree,
+            &[],
+        );
+        try_run(builder, &mut cargo.into());
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct ExpandYamlAnchors;
 
@@ -1273,59 +1310,51 @@ macro_rules! test_definitions {
     };
 }
 
-default_test!(Ui { path: "src/test/ui", mode: "ui", suite: "ui" });
+default_test!(Ui { path: "tests/ui", mode: "ui", suite: "ui" });
 
 default_test!(RunPassValgrind {
-    path: "src/test/run-pass-valgrind",
+    path: "tests/run-pass-valgrind",
     mode: "run-pass-valgrind",
     suite: "run-pass-valgrind"
 });
 
-default_test!(MirOpt { path: "src/test/mir-opt", mode: "mir-opt", suite: "mir-opt" });
+default_test!(MirOpt { path: "tests/mir-opt", mode: "mir-opt", suite: "mir-opt" });
 
-default_test!(Codegen { path: "src/test/codegen", mode: "codegen", suite: "codegen" });
+default_test!(Codegen { path: "tests/codegen", mode: "codegen", suite: "codegen" });
 
 default_test!(CodegenUnits {
-    path: "src/test/codegen-units",
+    path: "tests/codegen-units",
     mode: "codegen-units",
     suite: "codegen-units"
 });
 
-default_test!(Incremental {
-    path: "src/test/incremental",
-    mode: "incremental",
-    suite: "incremental"
-});
+default_test!(Incremental { path: "tests/incremental", mode: "incremental", suite: "incremental" });
 
 default_test_with_compare_mode!(Debuginfo {
-    path: "src/test/debuginfo",
+    path: "tests/debuginfo",
     mode: "debuginfo",
     suite: "debuginfo",
     compare_mode: "split-dwarf"
 });
 
-host_test!(UiFullDeps { path: "src/test/ui-fulldeps", mode: "ui", suite: "ui-fulldeps" });
+host_test!(UiFullDeps { path: "tests/ui-fulldeps", mode: "ui", suite: "ui-fulldeps" });
 
-host_test!(Rustdoc { path: "src/test/rustdoc", mode: "rustdoc", suite: "rustdoc" });
-host_test!(RustdocUi { path: "src/test/rustdoc-ui", mode: "ui", suite: "rustdoc-ui" });
+host_test!(Rustdoc { path: "tests/rustdoc", mode: "rustdoc", suite: "rustdoc" });
+host_test!(RustdocUi { path: "tests/rustdoc-ui", mode: "ui", suite: "rustdoc-ui" });
 
-host_test!(RustdocJson {
-    path: "src/test/rustdoc-json",
-    mode: "rustdoc-json",
-    suite: "rustdoc-json"
-});
+host_test!(RustdocJson { path: "tests/rustdoc-json", mode: "rustdoc-json", suite: "rustdoc-json" });
 
-host_test!(Pretty { path: "src/test/pretty", mode: "pretty", suite: "pretty" });
+host_test!(Pretty { path: "tests/pretty", mode: "pretty", suite: "pretty" });
 
-default_test!(RunMake { path: "src/test/run-make", mode: "run-make", suite: "run-make" });
+default_test!(RunMake { path: "tests/run-make", mode: "run-make", suite: "run-make" });
 
 host_test!(RunMakeFullDeps {
-    path: "src/test/run-make-fulldeps",
+    path: "tests/run-make-fulldeps",
     mode: "run-make",
     suite: "run-make-fulldeps"
 });
 
-default_test!(Assembly { path: "src/test/assembly", mode: "assembly", suite: "assembly" });
+default_test!(Assembly { path: "tests/assembly", mode: "assembly", suite: "assembly" });
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 struct Compiletest {
@@ -1437,7 +1466,7 @@ note: if you're sure you want to do this, please open an issue as to why. In the
             cmd.arg("--rust-demangler-path").arg(rust_demangler);
         }
 
-        cmd.arg("--src-base").arg(builder.src.join("src/test").join(suite));
+        cmd.arg("--src-base").arg(builder.src.join("tests").join(suite));
         cmd.arg("--build-base").arg(testdir(builder, compiler.host).join(suite));
         cmd.arg("--sysroot-base").arg(builder.sysroot(compiler));
         cmd.arg("--stage-id").arg(format!("stage{}-{}", compiler.stage, target));
@@ -1575,7 +1604,8 @@ note: if you're sure you want to do this, please open an issue as to why. In the
         let mut llvm_components_passed = false;
         let mut copts_passed = false;
         if builder.config.llvm_enabled() {
-            let llvm_config = builder.ensure(native::Llvm { target: builder.config.build });
+            let native::LlvmResult { llvm_config, .. } =
+                builder.ensure(native::Llvm { target: builder.config.build });
             if !builder.config.dry_run() {
                 let llvm_version = output(Command::new(&llvm_config).arg("--version"));
                 let llvm_components = output(Command::new(&llvm_config).arg("--components"));
@@ -1900,7 +1930,7 @@ impl Step for ErrorIndex {
     fn make_run(run: RunConfig<'_>) {
         // error_index_generator depends on librustdoc. Use the compiler that
         // is normally used to build rustdoc for other tests (like compiletest
-        // tests in src/test/rustdoc) so that it shares the same artifacts.
+        // tests in tests/rustdoc) so that it shares the same artifacts.
         let compiler = run.builder.compiler(run.builder.top_stage, run.builder.config.build);
         run.builder.ensure(ErrorIndex { compiler });
     }
@@ -2153,8 +2183,12 @@ impl Step for Crate {
         }
 
         builder.info(&format!(
-            "{} {:?} stage{} ({} -> {})",
-            test_kind, self.crates, compiler.stage, &compiler.host, target
+            "{}{} stage{} ({} -> {})",
+            test_kind,
+            crate_description(&self.crates),
+            compiler.stage,
+            &compiler.host,
+            target
         ));
         let _time = util::timeit(&builder);
         try_run(builder, &mut cargo.into());
@@ -2193,7 +2227,7 @@ impl Step for CrateRustdoc {
             builder.compiler(builder.top_stage, target)
         } else {
             // Use the previous stage compiler to reuse the artifacts that are
-            // created when running compiletest for src/test/rustdoc. If this used
+            // created when running compiletest for tests/rustdoc. If this used
             // `compiler`, then it would cause rustdoc to be built *again*, which
             // isn't really necessary.
             builder.compiler_for(builder.top_stage, target, target)
@@ -2309,7 +2343,7 @@ impl Step for CrateRustdocJsonTypes {
         let target = self.host;
 
         // Use the previous stage compiler to reuse the artifacts that are
-        // created when running compiletest for src/test/rustdoc. If this used
+        // created when running compiletest for tests/rustdoc. If this used
         // `compiler`, then it would cause rustdoc to be built *again*, which
         // isn't really necessary.
         let compiler = builder.compiler_for(builder.top_stage, target, target);
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index e0be4c432..9a2100c2f 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -29,6 +29,8 @@ struct ToolBuild {
     is_optional_tool: bool,
     source_type: SourceType,
     extra_features: Vec<String>,
+    /// Nightly-only features that are allowed (comma-separated list).
+    allow_features: &'static str,
 }
 
 impl Step for ToolBuild {
@@ -59,7 +61,7 @@ impl Step for ToolBuild {
             _ => panic!("unexpected Mode for tool build"),
         }
 
-        let cargo = prepare_tool_cargo(
+        let mut cargo = prepare_tool_cargo(
             builder,
             compiler,
             self.mode,
@@ -69,6 +71,9 @@ impl Step for ToolBuild {
             self.source_type,
             &self.extra_features,
         );
+        if !self.allow_features.is_empty() {
+            cargo.allow_features(self.allow_features);
+        }
 
         builder.info(&format!("Building stage{} tool {} ({})", compiler.stage, tool, target));
         let mut duplicates = Vec::new();
@@ -292,6 +297,7 @@ macro_rules! bootstrap_tool {
         $name:ident, $path:expr, $tool_name:expr
         $(,is_external_tool = $external:expr)*
         $(,is_unstable_tool = $unstable:expr)*
+        $(,allow_features = $allow_features:expr)?
         ;
     )+) => {
         #[derive(Copy, PartialEq, Eq, Clone)]
@@ -355,6 +361,7 @@ macro_rules! bootstrap_tool {
                         SourceType::InTree
                     },
                     extra_features: vec![],
+                    allow_features: concat!($($allow_features)*),
                 }).expect("expected to build -- essential tool")
             }
         }
@@ -368,7 +375,7 @@ bootstrap_tool!(
     Tidy, "src/tools/tidy", "tidy";
     Linkchecker, "src/tools/linkchecker", "linkchecker";
     CargoTest, "src/tools/cargotest", "cargotest";
-    Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true;
+    Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true, allow_features = "test";
     BuildManifest, "src/tools/build-manifest", "build-manifest";
     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
     RustInstaller, "src/tools/rust-installer", "rust-installer", is_external_tool = true;
@@ -435,6 +442,7 @@ impl Step for ErrorIndex {
                 is_optional_tool: false,
                 source_type: SourceType::InTree,
                 extra_features: Vec::new(),
+                allow_features: "",
             })
             .expect("expected to build -- essential tool")
     }
@@ -471,6 +479,7 @@ impl Step for RemoteTestServer {
                 is_optional_tool: false,
                 source_type: SourceType::InTree,
                 extra_features: Vec::new(),
+                allow_features: "",
             })
             .expect("expected to build -- essential tool")
     }
@@ -622,6 +631,7 @@ impl Step for Cargo {
                 is_optional_tool: false,
                 source_type: SourceType::Submodule,
                 extra_features: Vec::new(),
+                allow_features: "",
             })
             .expect("expected to build -- essential tool");
 
@@ -637,6 +647,7 @@ impl Step for Cargo {
                 is_optional_tool: true,
                 source_type: SourceType::Submodule,
                 extra_features: Vec::new(),
+                allow_features: "",
             });
         };
 
@@ -684,6 +695,7 @@ impl Step for LldWrapper {
                 is_optional_tool: false,
                 source_type: SourceType::InTree,
                 extra_features: Vec::new(),
+                allow_features: "",
             })
             .expect("expected to build -- essential tool");
 
@@ -697,6 +709,11 @@ pub struct RustAnalyzer {
     pub target: TargetSelection,
 }
 
+impl RustAnalyzer {
+    pub const ALLOW_FEATURES: &str =
+        "proc_macro_internals,proc_macro_diagnostic,proc_macro_span,proc_macro_span_shrink";
+}
+
 impl Step for RustAnalyzer {
     type Output = Option<PathBuf>;
     const DEFAULT: bool = true;
@@ -731,6 +748,7 @@ impl Step for RustAnalyzer {
             extra_features: vec!["rust-analyzer/in-rust-tree".to_owned()],
             is_optional_tool: false,
             source_type: SourceType::InTree,
+            allow_features: RustAnalyzer::ALLOW_FEATURES,
         })
     }
 }
@@ -747,19 +765,9 @@ impl Step for RustAnalyzerProcMacroSrv {
     const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        let builder = run.builder;
-
         // Allow building `rust-analyzer-proc-macro-srv` both as part of the `rust-analyzer` and as a stand-alone tool.
         run.path("src/tools/rust-analyzer")
             .path("src/tools/rust-analyzer/crates/proc-macro-srv-cli")
-            .default_condition(
-                builder.config.extended
-                    && builder.config.tools.as_ref().map_or(true, |tools| {
-                        tools.iter().any(|tool| {
-                            tool == "rust-analyzer" || tool == "rust-analyzer-proc-macro-srv"
-                        })
-                    }),
-            )
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -779,6 +787,7 @@ impl Step for RustAnalyzerProcMacroSrv {
             extra_features: vec!["proc-macro-srv/sysroot-abi".to_owned()],
             is_optional_tool: false,
             source_type: SourceType::InTree,
+            allow_features: RustAnalyzer::ALLOW_FEATURES,
         })?;
 
         // Copy `rust-analyzer-proc-macro-srv` to `<sysroot>/libexec/`
@@ -798,6 +807,7 @@ macro_rules! tool_extended {
        $tool_name:expr,
        stable = $stable:expr
        $(,tool_std = $tool_std:literal)?
+       $(,allow_features = $allow_features:expr)?
        ;)+) => {
         $(
             #[derive(Debug, Clone, Hash, PartialEq, Eq)]
@@ -849,6 +859,7 @@ macro_rules! tool_extended {
                     extra_features: $sel.extra_features,
                     is_optional_tool: true,
                     source_type: SourceType::InTree,
+                    allow_features: concat!($($allow_features)*),
                 })
             }
         }
diff --git a/src/bootstrap/util.rs b/src/bootstrap/util.rs
index 582207832..93e53d383 100644
--- a/src/bootstrap/util.rs
+++ b/src/bootstrap/util.rs
@@ -255,35 +255,6 @@ pub enum CiEnv {
     GitHubActions,
 }
 
-impl CiEnv {
-    /// Obtains the current CI environment.
-    pub fn current() -> CiEnv {
-        if env::var("TF_BUILD").map_or(false, |e| e == "True") {
-            CiEnv::AzurePipelines
-        } else if env::var("GITHUB_ACTIONS").map_or(false, |e| e == "true") {
-            CiEnv::GitHubActions
-        } else {
-            CiEnv::None
-        }
-    }
-
-    pub fn is_ci() -> bool {
-        Self::current() != CiEnv::None
-    }
-
-    /// If in a CI environment, forces the command to run with colors.
-    pub fn force_coloring_in_ci(self, cmd: &mut Command) {
-        if self != CiEnv::None {
-            // Due to use of stamp/docker, the output stream of rustbuild is not
-            // a TTY in CI, so coloring is by-default turned off.
-            // The explicit `TERM=xterm` environment is needed for
-            // `--color always` to actually work. This env var was lost when
-            // compiling through the Makefile. Very strange.
-            cmd.env("TERM", "xterm").args(&["--color", "always"]);
-        }
-    }
-}
-
 pub fn forcing_clang_based_tests() -> bool {
     if let Some(var) = env::var_os("RUSTBUILD_FORCE_CLANG_BASED_TESTS") {
         match &var.to_string_lossy().to_lowercase()[..] {
@@ -441,6 +412,23 @@ pub fn output(cmd: &mut Command) -> String {
     String::from_utf8(output.stdout).unwrap()
 }
 
+pub fn output_result(cmd: &mut Command) -> Result<String, String> {
+    let output = match cmd.stderr(Stdio::inherit()).output() {
+        Ok(status) => status,
+        Err(e) => return Err(format!("failed to run command: {:?}: {}", cmd, e)),
+    };
+    if !output.status.success() {
+        return Err(format!(
+            "command did not execute successfully: {:?}\n\
+             expected success, got: {}\n{}",
+            cmd,
+            output.status,
+            String::from_utf8(output.stderr).map_err(|err| format!("{err:?}"))?
+        ));
+    }
+    Ok(String::from_utf8(output.stdout).map_err(|err| format!("{err:?}"))?)
+}
+
 /// Returns the last-modified time for `path`, or zero if it doesn't exist.
 pub fn mtime(path: &Path) -> SystemTime {
     fs::metadata(path).and_then(|f| f.modified()).unwrap_or(UNIX_EPOCH)