diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 916c8e5d187c2a2b4c64748e8ba36ddc37a78e4a..eee90ed2c1c1134bddf09c9154102e8f78b40eb0 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -446,7 +446,7 @@ class RustBuild(object):
         self.nix_deps_dir = None
         self.rustc_commit = None
 
-    def download_toolchain(self, stage0=True, rustc_channel=None):
+    def download_toolchain(self, rustc_channel=None):
         """Fetch the build system for Rust, written in Rust
 
         This method will build a cache directory, then it will fetch the
@@ -458,35 +458,26 @@ class RustBuild(object):
         """
         if rustc_channel is None:
             rustc_channel = self.stage0_compiler.version
-        bin_root = self.bin_root(stage0)
+        bin_root = self.bin_root()
 
         key = self.stage0_compiler.date
-        if not stage0:
-            key += str(self.rustc_commit)
-        if self.rustc(stage0).startswith(bin_root) and \
-                (not os.path.exists(self.rustc(stage0)) or
-                 self.program_out_of_date(self.rustc_stamp(stage0), key)):
+        if self.rustc().startswith(bin_root) and \
+                (not os.path.exists(self.rustc()) or
+                 self.program_out_of_date(self.rustc_stamp(), key)):
             if os.path.exists(bin_root):
                 shutil.rmtree(bin_root)
             tarball_suffix = '.tar.xz' if support_xz() else '.tar.gz'
             filename = "rust-std-{}-{}{}".format(
                 rustc_channel, self.build, tarball_suffix)
             pattern = "rust-std-{}".format(self.build)
-            self._download_component_helper(filename, pattern, tarball_suffix, stage0)
+            self._download_component_helper(filename, pattern, tarball_suffix)
             filename = "rustc-{}-{}{}".format(rustc_channel, self.build,
                                               tarball_suffix)
-            self._download_component_helper(filename, "rustc", tarball_suffix, stage0)
-            # download-rustc doesn't need its own cargo, it can just use beta's.
-            if stage0:
-                filename = "cargo-{}-{}{}".format(rustc_channel, self.build,
-                                                tarball_suffix)
-                self._download_component_helper(filename, "cargo", tarball_suffix)
-                self.fix_bin_or_dylib("{}/bin/cargo".format(bin_root))
-            else:
-                filename = "rustc-dev-{}-{}{}".format(rustc_channel, self.build, tarball_suffix)
-                self._download_component_helper(
-                    filename, "rustc-dev", tarball_suffix, stage0
-                )
+            self._download_component_helper(filename, "rustc", tarball_suffix)
+            filename = "cargo-{}-{}{}".format(rustc_channel, self.build,
+                                            tarball_suffix)
+            self._download_component_helper(filename, "cargo", tarball_suffix)
+            self.fix_bin_or_dylib("{}/bin/cargo".format(bin_root))
 
             self.fix_bin_or_dylib("{}/bin/rustc".format(bin_root))
             self.fix_bin_or_dylib("{}/bin/rustdoc".format(bin_root))
@@ -494,7 +485,7 @@ class RustBuild(object):
             for lib in os.listdir(lib_dir):
                 if lib.endswith(".so"):
                     self.fix_bin_or_dylib(os.path.join(lib_dir, lib))
-            with output(self.rustc_stamp(stage0)) as rust_stamp:
+            with output(self.rustc_stamp()) as rust_stamp:
                 rust_stamp.write(key)
 
         if self.rustfmt() and self.rustfmt().startswith(bin_root) and (
@@ -518,24 +509,17 @@ class RustBuild(object):
                     rustfmt_stamp.write(self.stage0_rustfmt.channel())
 
     def _download_component_helper(
-        self, filename, pattern, tarball_suffix, stage0=True, key=None
+        self, filename, pattern, tarball_suffix, key=None
     ):
         if key is None:
-            if stage0:
-                key = self.stage0_compiler.date
-            else:
-                key = self.rustc_commit
+            key = self.stage0_compiler.date
         cache_dst = os.path.join(self.build_dir, "cache")
         rustc_cache = os.path.join(cache_dst, key)
         if not os.path.exists(rustc_cache):
             os.makedirs(rustc_cache)
 
-        if stage0:
-            base = self._download_url
-            url = "dist/{}".format(key)
-        else:
-            base = "https://ci-artifacts.rust-lang.org"
-            url = "rustc-builds/{}".format(self.rustc_commit)
+        base = self._download_url
+        url = "dist/{}".format(key)
         tarball = os.path.join(rustc_cache, filename)
         if not os.path.exists(tarball):
             get(
@@ -544,9 +528,9 @@ class RustBuild(object):
                 tarball,
                 self.checksums_sha256,
                 verbose=self.verbose,
-                do_verify=stage0,
+                do_verify=True,
             )
-        unpack(tarball, tarball_suffix, self.bin_root(stage0), match=pattern, verbose=self.verbose)
+        unpack(tarball, tarball_suffix, self.bin_root(), match=pattern, verbose=self.verbose)
 
     def fix_bin_or_dylib(self, fname):
         """Modifies the interpreter section of 'fname' to fix the dynamic linker,
@@ -689,17 +673,15 @@ class RustBuild(object):
         # FIXME: support downloading artifacts from the beta channel
         self.download_toolchain(False, "nightly")
 
-    def rustc_stamp(self, stage0):
+    def rustc_stamp(self):
         """Return the path for .rustc-stamp at the given stage
 
         >>> rb = RustBuild()
         >>> rb.build_dir = "build"
-        >>> rb.rustc_stamp(True) == os.path.join("build", "stage0", ".rustc-stamp")
-        True
-        >>> rb.rustc_stamp(False) == os.path.join("build", "ci-rustc", ".rustc-stamp")
+        >>> rb.rustc_stamp() == os.path.join("build", "stage0", ".rustc-stamp")
         True
         """
-        return os.path.join(self.bin_root(stage0), '.rustc-stamp')
+        return os.path.join(self.bin_root(), '.rustc-stamp')
 
     def rustfmt_stamp(self):
         """Return the path for .rustfmt-stamp
@@ -709,7 +691,7 @@ class RustBuild(object):
         >>> rb.rustfmt_stamp() == os.path.join("build", "stage0", ".rustfmt-stamp")
         True
         """
-        return os.path.join(self.bin_root(True), '.rustfmt-stamp')
+        return os.path.join(self.bin_root(), '.rustfmt-stamp')
 
     def program_out_of_date(self, stamp_path, key):
         """Check if the given program stamp is out of date"""
@@ -718,26 +700,21 @@ class RustBuild(object):
         with open(stamp_path, 'r') as stamp:
             return key != stamp.read()
 
-    def bin_root(self, stage0):
+    def bin_root(self):
         """Return the binary root directory for the given stage
 
         >>> rb = RustBuild()
         >>> rb.build_dir = "build"
-        >>> rb.bin_root(True) == os.path.join("build", "stage0")
-        True
-        >>> rb.bin_root(False) == os.path.join("build", "ci-rustc")
+        >>> rb.bin_root() == os.path.join("build", "stage0")
         True
 
         When the 'build' property is given should be a nested directory:
 
         >>> rb.build = "devel"
-        >>> rb.bin_root(True) == os.path.join("build", "devel", "stage0")
+        >>> rb.bin_root() == os.path.join("build", "devel", "stage0")
         True
         """
-        if stage0:
-            subdir = "stage0"
-        else:
-            subdir = "ci-rustc"
+        subdir = "stage0"
         return os.path.join(self.build_dir, self.build, subdir)
 
     def get_toml(self, key, section=None):
@@ -785,9 +762,9 @@ class RustBuild(object):
         """Return config path for cargo"""
         return self.program_config('cargo')
 
-    def rustc(self, stage0):
+    def rustc(self):
         """Return config path for rustc"""
-        return self.program_config('rustc', stage0)
+        return self.program_config('rustc')
 
     def rustfmt(self):
         """Return config path for rustfmt"""
@@ -795,7 +772,7 @@ class RustBuild(object):
             return None
         return self.program_config('rustfmt')
 
-    def program_config(self, program, stage0=True):
+    def program_config(self, program):
         """Return config path for the given program at the given stage
 
         >>> rb = RustBuild()
@@ -803,19 +780,15 @@ class RustBuild(object):
         >>> rb.program_config('rustc')
         'rustc'
         >>> rb.config_toml = ''
-        >>> cargo_path = rb.program_config('cargo', True)
-        >>> cargo_path.rstrip(".exe") == os.path.join(rb.bin_root(True),
-        ... "bin", "cargo")
-        True
-        >>> cargo_path = rb.program_config('cargo', False)
-        >>> cargo_path.rstrip(".exe") == os.path.join(rb.bin_root(False),
+        >>> cargo_path = rb.program_config('cargo')
+        >>> cargo_path.rstrip(".exe") == os.path.join(rb.bin_root(),
         ... "bin", "cargo")
         True
         """
         config = self.get_toml(program)
         if config:
             return os.path.expanduser(config)
-        return os.path.join(self.bin_root(stage0), "bin", "{}{}".format(
+        return os.path.join(self.bin_root(), "bin", "{}{}".format(
             program, self.exe_suffix()))
 
     @staticmethod
@@ -871,14 +844,14 @@ class RustBuild(object):
         if "CARGO_BUILD_TARGET" in env:
             del env["CARGO_BUILD_TARGET"]
         env["CARGO_TARGET_DIR"] = build_dir
-        env["RUSTC"] = self.rustc(True)
-        env["LD_LIBRARY_PATH"] = os.path.join(self.bin_root(True), "lib") + \
+        env["RUSTC"] = self.rustc()
+        env["LD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
             (os.pathsep + env["LD_LIBRARY_PATH"]) \
             if "LD_LIBRARY_PATH" in env else ""
-        env["DYLD_LIBRARY_PATH"] = os.path.join(self.bin_root(True), "lib") + \
+        env["DYLD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
             (os.pathsep + env["DYLD_LIBRARY_PATH"]) \
             if "DYLD_LIBRARY_PATH" in env else ""
-        env["LIBRARY_PATH"] = os.path.join(self.bin_root(True), "lib") + \
+        env["LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
             (os.pathsep + env["LIBRARY_PATH"]) \
             if "LIBRARY_PATH" in env else ""
 
@@ -900,7 +873,7 @@ class RustBuild(object):
         if self.get_toml("deny-warnings", "rust") != "false":
             env["RUSTFLAGS"] += " -Dwarnings"
 
-        env["PATH"] = os.path.join(self.bin_root(True), "bin") + \
+        env["PATH"] = os.path.join(self.bin_root(), "bin") + \
             os.pathsep + env["PATH"]
         if not os.path.isfile(self.cargo()):
             raise Exception("no cargo executable found at `{}`".format(
@@ -1172,7 +1145,7 @@ def bootstrap(help_triggered):
     # Fetch/build the bootstrap
     build.download_toolchain()
     # Download the master compiler if `download-rustc` is set
-    build.maybe_download_ci_toolchain()
+    # build.maybe_download_ci_toolchain()
     sys.stdout.flush()
     build.ensure_vendored()
     build.build_bootstrap()
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index a0ce200883d3c570a39c8b41cd8a45739a94132f..94918cb318f9b71080f9ee182c7cca0573127823 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -915,15 +915,12 @@ fn download_with_retries(&self, tempfile: &str, url: &str) {
         }
     }
 
-    pub(crate) fn unpack(&self, tarball: &Path, dst: &Path) {
+    pub(crate) fn unpack(&self, tarball: &Path, dst: &Path, pattern: &str) {
         println!("extracting {} to {}", tarball.display(), dst.display());
         if !dst.exists() {
             t!(fs::create_dir_all(dst));
         }
 
-        // FIXME: will need to be a parameter once `download-rustc` is moved to rustbuild
-        const MATCH: &str = "rust-dev";
-
         // `tarball` ends with `.tar.xz`; strip that suffix
         // example: `rust-dev-nightly-x86_64-unknown-linux-gnu`
         let uncompressed_filename =
@@ -943,10 +940,10 @@ pub(crate) fn unpack(&self, tarball: &Path, dst: &Path) {
                 continue;
             }
             let mut short_path = t!(original_path.strip_prefix(directory_prefix));
-            if !short_path.starts_with(MATCH) {
+            if !short_path.starts_with(pattern) {
                 continue;
             }
-            short_path = t!(short_path.strip_prefix(MATCH));
+            short_path = t!(short_path.strip_prefix(pattern));
             let dst_path = dst.join(short_path);
             self.verbose(&format!("extracting {} to {}", original_path.display(), dst.display()));
             if !t!(member.unpack_in(dst)) {
@@ -1022,7 +1019,7 @@ fn run(self, builder: &Builder<'_>) -> Interned<PathBuf> {
                     .join("lib");
                 // Avoid deleting the rustlib/ directory we just copied
                 // (in `impl Step for Sysroot`).
-                if !builder.config.download_rustc {
+                if !builder.download_rustc() {
                     let _ = fs::remove_dir_all(&sysroot);
                     t!(fs::create_dir_all(&sysroot));
                 }
@@ -1179,6 +1176,10 @@ pub(crate) fn llvm_link_shared(&self) -> bool {
         Config::llvm_link_shared(self)
     }
 
+    pub(crate) fn download_rustc(&self) -> bool {
+        Config::download_rustc(self)
+    }
+
     /// Prepares an invocation of `cargo` to be run.
     ///
     /// This will create a `Command` that represents a pending execution of
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 0b430f64e1edc94ee2622f7b4a9b5b750ff76bff..f1960e39a41c7296b370ee78e5693f107adc25c2 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -42,8 +42,10 @@ impl Step for Std {
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         // When downloading stage1, the standard library has already been copied to the sysroot, so
         // there's no need to rebuild it.
-        let download_rustc = run.builder.config.download_rustc;
-        run.all_krates("test").path("library").default_condition(!download_rustc)
+        let builder = run.builder;
+        run.all_krates("test")
+            .path("library")
+            .lazy_default_condition(Box::new(|| !builder.download_rustc()))
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -66,7 +68,7 @@ fn run(self, builder: &Builder<'_>) {
         // Don't recompile them.
         // NOTE: the ABI of the beta compiler is different from the ABI of the downloaded compiler,
         // so its artifacts can't be reused.
-        if builder.config.download_rustc && compiler.stage != 0 {
+        if builder.download_rustc() && compiler.stage != 0 {
             return;
         }
 
@@ -551,7 +553,7 @@ fn run(self, builder: &Builder<'_>) {
 
         // NOTE: the ABI of the beta compiler is different from the ABI of the downloaded compiler,
         // so its artifacts can't be reused.
-        if builder.config.download_rustc && compiler.stage != 0 {
+        if builder.download_rustc() && compiler.stage != 0 {
             // Copy the existing artifacts instead of rebuilding them.
             // NOTE: this path is only taken for tools linking to rustc-dev.
             builder.ensure(Sysroot { compiler });
@@ -995,7 +997,7 @@ fn run(self, builder: &Builder<'_>) -> Interned<PathBuf> {
         t!(fs::create_dir_all(&sysroot));
 
         // If we're downloading a compiler from CI, we can use the same compiler for all stages other than 0.
-        if builder.config.download_rustc && compiler.stage != 0 {
+        if builder.download_rustc() && compiler.stage != 0 {
             assert_eq!(
                 builder.config.build, compiler.host,
                 "Cross-compiling is not yet supported with `download-rustc`",
@@ -1090,7 +1092,7 @@ fn run(self, builder: &Builder<'_>) -> Compiler {
         let build_compiler = builder.compiler(target_compiler.stage - 1, builder.config.build);
 
         // If we're downloading a compiler from CI, we can use the same compiler for all stages other than 0.
-        if builder.config.download_rustc {
+        if builder.download_rustc() {
             builder.ensure(Sysroot { compiler: target_compiler });
             return target_compiler;
         }
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 843d276cd7a88d201beaa91bfcc11755914ce5b3..f51a6481e43fc36f4eaf331043ad7c9b6e340296 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -7,9 +7,11 @@
 use std::cmp;
 use std::collections::{HashMap, HashSet};
 use std::env;
+use std::ffi::OsStr;
 use std::fmt;
 use std::fs;
 use std::path::{Path, PathBuf};
+use std::process::{exit, Command};
 use std::str::FromStr;
 
 use crate::builder::{Builder, TaskPath};
@@ -17,7 +19,8 @@
 use crate::channel::GitInfo;
 pub use crate::flags::Subcommand;
 use crate::flags::{Color, Flags};
-use crate::util::{exe, t};
+use crate::util::{exe, output, program_out_of_date, t};
+use once_cell::sync::OnceCell;
 use serde::{Deserialize, Deserializer};
 
 macro_rules! check_ci_llvm {
@@ -81,7 +84,11 @@ pub struct Config {
     pub cmd: Subcommand,
     pub incremental: bool,
     pub dry_run: bool,
-    pub download_rustc: bool,
+    /// `None` if we shouldn't download CI compiler artifacts, or the commit to download if we should.
+    #[cfg(not(test))]
+    download_rustc_commit: Option<String>,
+    #[cfg(test)]
+    pub download_rustc_commit: Option<String>,
 
     pub deny_warnings: bool,
     pub backtrace_on_ice: bool,
@@ -1080,7 +1087,8 @@ pub fn parse(args: &[String]) -> 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 = env::var("BOOTSTRAP_DOWNLOAD_RUSTC").as_deref() == Ok("1");
+            config.download_rustc_commit =
+                download_ci_rustc_commit(rust.download_rustc, config.verbose > 0);
         } else {
             config.rust_profile_use = flags.rust_profile_use;
             config.rust_profile_generate = flags.rust_profile_generate;
@@ -1192,7 +1200,7 @@ pub fn parse(args: &[String]) -> Config {
         let default = config.channel == "dev";
         config.ignore_git = ignore_git.unwrap_or(default);
 
-        let download_rustc = config.download_rustc;
+        let download_rustc = config.download_rustc_commit.is_some();
         // See https://github.com/rust-lang/compiler-team/issues/326
         config.stage = match config.cmd {
             Subcommand::Check { .. } => flags.stage.or(build.check_stage).unwrap_or(0),
@@ -1309,6 +1317,23 @@ pub(crate) fn llvm_link_shared(builder: &Builder<'_>) -> bool {
         llvm_link_shared
     }
 
+    /// Return whether we will use a downloaded, pre-compiled version of rustc, or just build from source.
+    pub(crate) fn download_rustc(builder: &Builder<'_>) -> bool {
+        static DOWNLOAD_RUSTC: OnceCell<bool> = OnceCell::new();
+        if builder.config.dry_run && DOWNLOAD_RUSTC.get().is_none() {
+            // avoid trying to actually download the commit
+            return false;
+        }
+
+        *DOWNLOAD_RUSTC.get_or_init(|| match &builder.config.download_rustc_commit {
+            None => false,
+            Some(commit) => {
+                download_ci_rustc(builder, commit);
+                true
+            }
+        })
+    }
+
     pub fn verbose(&self) -> bool {
         self.verbose > 0
     }
@@ -1358,3 +1383,116 @@ fn threads_from_config(v: u32) -> u32 {
         n => n,
     }
 }
+
+/// Returns the commit to download, or `None` if we shouldn't download CI artifacts.
+fn download_ci_rustc_commit(download_rustc: Option<StringOrBool>, verbose: bool) -> Option<String> {
+    // If `download-rustc` is not set, default to rebuilding.
+    let if_unchanged = match download_rustc {
+        None | Some(StringOrBool::Bool(false)) => return None,
+        Some(StringOrBool::Bool(true)) => false,
+        Some(StringOrBool::String(s)) if s == "if-unchanged" => true,
+        Some(StringOrBool::String(other)) => {
+            panic!("unrecognized option for download-rustc: {}", other)
+        }
+    };
+
+    // Handle running from a directory other than the top level
+    let top_level = output(Command::new("git").args(&["rev-parse", "--show-toplevel"]));
+    let top_level = top_level.trim_end();
+    let compiler = format!("{top_level}/compiler/");
+    let library = format!("{top_level}/library/");
+
+    // Look for a version to compare to based on the current commit.
+    // Only commits merged by bors will have CI artifacts.
+    let merge_base = output(Command::new("git").args(&[
+        "rev-list",
+        "--author=bors@rust-lang.org",
+        "-n1",
+        "--first-parent",
+        "HEAD",
+    ]));
+    let commit = merge_base.trim_end();
+    if commit.is_empty() {
+        println!("error: could not find commit hash for downloading rustc");
+        println!("help: maybe your repository history is too shallow?");
+        println!("help: consider disabling `download-rustc`");
+        println!("help: or fetch enough history to include one upstream commit");
+        exit(1);
+    }
+
+    // Warn if there were changes to the compiler or standard library since the ancestor commit.
+    let has_changes = !t!(Command::new("git")
+        .args(&["diff-index", "--quiet", &commit, "--", &compiler, &library])
+        .status())
+    .success();
+    if has_changes {
+        if if_unchanged {
+            if verbose {
+                println!(
+                    "warning: saw changes to compiler/ or library/ since {commit}; \
+                          ignoring `download-rustc`"
+                );
+            }
+            return None;
+        }
+        println!(
+            "warning: `download-rustc` is enabled, but there are changes to \
+                  compiler/ or library/"
+        );
+    }
+
+    Some(commit.to_string())
+}
+
+fn download_ci_rustc(builder: &Builder<'_>, commit: &str) {
+    builder.verbose(&format!("using downloaded stage2 artifacts from CI (commit {commit})"));
+    // FIXME: support downloading artifacts from the beta channel
+    const CHANNEL: &str = "nightly";
+    let host = builder.config.build.triple;
+    let bin_root = builder.out.join(host).join("ci-rustc");
+    let rustc_stamp = bin_root.join(".rustc-stamp");
+
+    if !bin_root.join("bin").join("rustc").exists() || program_out_of_date(&rustc_stamp, commit) {
+        if bin_root.exists() {
+            t!(fs::remove_dir_all(&bin_root));
+        }
+        let filename = format!("rust-std-{CHANNEL}-{host}.tar.xz");
+        let pattern = format!("rust-std-{host}");
+        download_component(builder, filename, &pattern, commit);
+        let filename = format!("rustc-{CHANNEL}-{host}.tar.xz");
+        download_component(builder, filename, "rustc", commit);
+        // download-rustc doesn't need its own cargo, it can just use beta's.
+        let filename = format!("rustc-dev-{CHANNEL}-{host}.tar.xz");
+        download_component(builder, filename, "rustc-dev", commit);
+
+        builder.fix_bin_or_dylib(&bin_root.join("bin").join("rustc"));
+        builder.fix_bin_or_dylib(&bin_root.join("bin").join("rustdoc"));
+        let lib_dir = bin_root.join("lib");
+        for lib in t!(fs::read_dir(lib_dir)) {
+            let lib = t!(lib);
+            if lib.path().extension() == Some(OsStr::new("so")) {
+                builder.fix_bin_or_dylib(&lib.path());
+            }
+        }
+        t!(fs::write(rustc_stamp, commit));
+    }
+}
+
+/// Download a single component of a CI-built toolchain (not necessarily a published nightly).
+// NOTE: intentionally takes an owned string to avoid downloading multiple times by accident
+fn download_component(builder: &Builder<'_>, filename: String, prefix: &str, commit: &str) {
+    let cache_dst = builder.out.join("cache");
+    let rustc_cache = cache_dst.join(commit);
+    if !rustc_cache.exists() {
+        t!(fs::create_dir_all(&rustc_cache));
+    }
+
+    let base = "https://ci-artifacts.rust-lang.org";
+    let url = format!("rustc-builds/{commit}");
+    let tarball = rustc_cache.join(&filename);
+    if !tarball.exists() {
+        builder.download_component(base, &format!("{url}/{filename}"), &tarball);
+    }
+    let bin_root = builder.out.join(builder.config.build.triple).join("ci-rustc");
+    builder.unpack(&tarball, &bin_root, prefix)
+}
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index 5bb94f297c81410f2bc4e5200611ac7dca2cbe74..d7211b2c2af2f9ba46f2651dfaaf6491ae32fa5e 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -182,7 +182,7 @@ fn download_ci_llvm(builder: &Builder<'_>, llvm_sha: &str) {
         builder.download_component(base, &format!("{}/{}", url, filename), &tarball);
     }
     let llvm_root = builder.config.ci_llvm_root();
-    builder.unpack(&tarball, &llvm_root);
+    builder.unpack(&tarball, &llvm_root, "rust-dev");
 }
 
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index bc851568f896b95076ef5926dc01af6f66d380ae..99e9e8794e30bc0e74d6c65b09aaf4b631e984a1 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -2058,7 +2058,7 @@ fn run(self, builder: &Builder<'_>) {
         let test_kind = self.test_kind;
         let target = self.host;
 
-        let compiler = if builder.config.download_rustc {
+        let compiler = if builder.download_rustc() {
             builder.compiler(builder.top_stage, target)
         } else {
             // Use the previous stage compiler to reuse the artifacts that are
@@ -2127,7 +2127,7 @@ fn run(self, builder: &Builder<'_>) {
         // with.
         //
         // Note that this set the host libdir for `download_rustc`, which uses a normal rust distribution.
-        let libdir = if builder.config.download_rustc {
+        let libdir = if builder.download_rustc() {
             builder.rustc_libdir(compiler)
         } else {
             builder.sysroot_libdir(compiler, target).to_path_buf()
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index 3b30e6de12a63abed65ed9388ea05a4e339e63ee..e1b78904646490899e03e43526c24406fb8a6cac 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -516,7 +516,7 @@ fn run(self, builder: &Builder<'_>) -> PathBuf {
         builder.ensure(compile::Rustc { compiler: build_compiler, target: target_compiler.host });
         // NOTE: this implies that `download-rustc` is pretty useless when compiling with the stage0
         // compiler, since you do just as much work.
-        if !builder.config.dry_run && builder.config.download_rustc && build_compiler.stage == 0 {
+        if !builder.config.dry_run && builder.download_rustc() && build_compiler.stage == 0 {
             println!(
                 "warning: `download-rustc` does nothing when building stage1 tools; consider using `--stage 2` instead"
             );