Auto merge of #143641 - Kobzol:tool-target, r=jieyouxu

Add `ToolTarget` to bootstrap

Oh, you thought I'm done with refactoring bootstrap tools? Na-ah, think again! After the failure of https://github.com/rust-lang/rust/pull/143581, `ToolTarget` is back with a vengeance. This time, I implemented the test changes and tool cleanups without forcing these tools to be built with the stage0 compiler.

There are still some small wins though, `LlvmBitcodeLinker` now starts at stage 1, and not stage 2. Cargo should also be ported to this new mode, but I'm leaving that for a follow-up PR.

Hopefully X-th time's the charm :crossed_fingers:

r? `@jieyouxu`

11 files changed, 408 insertions, 166 deletions

diff --git a/src/bootstrap/README.md b/src/bootstrap/README.md
index 6ce4c6d62fa..2965174b45b 100644
--- a/src/bootstrap/README.md
+++ b/src/bootstrap/README.md
@@ -105,7 +105,7 @@ build/
       debuginfo/
       ...
 
-    # Bootstrap host tools (which are always compiled with the stage0 compiler)
+    # Host tools (which are always compiled with the stage0 compiler)
     # are stored here.
     bootstrap-tools/
 
diff --git a/src/bootstrap/src/core/build_steps/check.rs b/src/bootstrap/src/core/build_steps/check.rs
index 3278b55305c..1d30886a86a 100644
--- a/src/bootstrap/src/core/build_steps/check.rs
+++ b/src/bootstrap/src/core/build_steps/check.rs
@@ -4,7 +4,10 @@ use crate::core::build_steps::compile::{
     add_to_sysroot, run_cargo, rustc_cargo, rustc_cargo_env, std_cargo, std_crates_for_run_make,
 };
 use crate::core::build_steps::tool;
-use crate::core::build_steps::tool::{COMPILETEST_ALLOW_FEATURES, SourceType, prepare_tool_cargo};
+use crate::core::build_steps::tool::{
+    COMPILETEST_ALLOW_FEATURES, SourceType, ToolTargetBuildMode, get_tool_target_compiler,
+    prepare_tool_cargo,
+};
 use crate::core::builder::{
     self, Alias, Builder, Kind, RunConfig, ShouldRun, Step, StepMetadata, crate_description,
 };
@@ -252,8 +255,10 @@ fn prepare_compiler_for_check(
     mode: Mode,
 ) -> Compiler {
     let host = builder.host_target;
+
     match mode {
         Mode::ToolBootstrap => builder.compiler(0, host),
+        Mode::ToolTarget => get_tool_target_compiler(builder, ToolTargetBuildMode::Build(target)),
         Mode::ToolStd => {
             if builder.config.compile_time_deps {
                 // When --compile-time-deps is passed, we can't use any rustc
diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 09bb2e35bda..85847cac446 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -19,7 +19,7 @@ use serde_derive::Deserialize;
 use tracing::{instrument, span};
 
 use crate::core::build_steps::gcc::{Gcc, add_cg_gcc_cargo_flags};
-use crate::core::build_steps::tool::SourceType;
+use crate::core::build_steps::tool::{SourceType, copy_lld_artifacts};
 use crate::core::build_steps::{dist, llvm};
 use crate::core::builder;
 use crate::core::builder::{
@@ -2050,19 +2050,20 @@ impl Step for Assemble {
             }
         }
 
-        let maybe_install_llvm_bitcode_linker = |compiler| {
+        let maybe_install_llvm_bitcode_linker = || {
             if builder.config.llvm_bitcode_linker_enabled {
                 trace!("llvm-bitcode-linker enabled, installing");
-                let llvm_bitcode_linker =
-                    builder.ensure(crate::core::build_steps::tool::LlvmBitcodeLinker {
-                        build_compiler: compiler,
-                        target: target_compiler.host,
-                    });
+                let llvm_bitcode_linker = builder.ensure(
+                    crate::core::build_steps::tool::LlvmBitcodeLinker::from_target_compiler(
+                        builder,
+                        target_compiler,
+                    ),
+                );
 
                 // Copy the llvm-bitcode-linker to the self-contained binary directory
                 let bindir_self_contained = builder
-                    .sysroot(compiler)
-                    .join(format!("lib/rustlib/{}/bin/self-contained", compiler.host));
+                    .sysroot(target_compiler)
+                    .join(format!("lib/rustlib/{}/bin/self-contained", target_compiler.host));
                 let tool_exe = exe("llvm-bitcode-linker", target_compiler.host);
 
                 t!(fs::create_dir_all(&bindir_self_contained));
@@ -2089,9 +2090,9 @@ impl Step for Assemble {
                 builder.info(&format!("Creating a sysroot for stage{stage} compiler (use `rustup toolchain link 'name' build/host/stage{stage}`)", stage = target_compiler.stage));
             }
 
-            let mut precompiled_compiler = target_compiler;
-            precompiled_compiler.forced_compiler(true);
-            maybe_install_llvm_bitcode_linker(precompiled_compiler);
+            // FIXME: this is incomplete, we do not copy a bunch of other stuff to the downloaded
+            // sysroot...
+            maybe_install_llvm_bitcode_linker();
 
             return target_compiler;
         }
@@ -2256,10 +2257,12 @@ impl Step for Assemble {
         copy_codegen_backends_to_sysroot(builder, build_compiler, target_compiler);
 
         if builder.config.lld_enabled {
-            builder.ensure(crate::core::build_steps::tool::LldWrapper {
-                build_compiler,
-                target_compiler,
-            });
+            let lld_wrapper =
+                builder.ensure(crate::core::build_steps::tool::LldWrapper::for_use_by_compiler(
+                    builder,
+                    target_compiler,
+                ));
+            copy_lld_artifacts(builder, lld_wrapper, target_compiler);
         }
 
         if builder.config.llvm_enabled(target_compiler.host) && builder.config.llvm_tools_enabled {
@@ -2284,15 +2287,14 @@ impl Step for Assemble {
         }
 
         // In addition to `rust-lld` also install `wasm-component-ld` when
-        // LLD is enabled. This is a relatively small binary that primarily
-        // delegates to the `rust-lld` binary for linking and then runs
-        // logic to create the final binary. This is used by the
-        // `wasm32-wasip2` target of Rust.
+        // is enabled. This is used by the `wasm32-wasip2` target of Rust.
         if builder.tool_enabled("wasm-component-ld") {
-            let wasm_component = builder.ensure(crate::core::build_steps::tool::WasmComponentLd {
-                compiler: build_compiler,
-                target: target_compiler.host,
-            });
+            let wasm_component = builder.ensure(
+                crate::core::build_steps::tool::WasmComponentLd::for_use_by_compiler(
+                    builder,
+                    target_compiler,
+                ),
+            );
             builder.copy_link(
                 &wasm_component.tool_path,
                 &libdir_bin.join(wasm_component.tool_path.file_name().unwrap()),
@@ -2300,7 +2302,7 @@ impl Step for Assemble {
             );
         }
 
-        maybe_install_llvm_bitcode_linker(target_compiler);
+        maybe_install_llvm_bitcode_linker();
 
         // Ensure that `libLLVM.so` ends up in the newly build compiler directory,
         // so that it can be found when the newly built `rustc` is run.
diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
index 8b2d65ace50..39e4fb2ac01 100644
--- a/src/bootstrap/src/core/build_steps/dist.rs
+++ b/src/bootstrap/src/core/build_steps/dist.rs
@@ -1575,7 +1575,10 @@ impl Step for Extended {
             compiler: builder.compiler(stage, target),
             backend: "cranelift".to_string(),
         });
-        add_component!("llvm-bitcode-linker" => LlvmBitcodeLinker {compiler, target});
+        add_component!("llvm-bitcode-linker" => LlvmBitcodeLinker {
+            build_compiler: compiler,
+            target
+        });
 
         let etc = builder.src.join("src/etc/installer");
 
@@ -2341,9 +2344,13 @@ impl Step for LlvmTools {
     }
 }
 
+/// Distributes the `llvm-bitcode-linker` tool so that it can be used by a compiler whose host
+/// is `target`.
 #[derive(Debug, PartialOrd, Ord, Clone, Hash, PartialEq, Eq)]
 pub struct LlvmBitcodeLinker {
-    pub compiler: Compiler,
+    /// The linker will be compiled by this compiler.
+    pub build_compiler: Compiler,
+    /// The linker will by usable by rustc on this host.
     pub target: TargetSelection,
 }
 
@@ -2359,9 +2366,8 @@ impl Step for LlvmBitcodeLinker {
 
     fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(LlvmBitcodeLinker {
-            compiler: run.builder.compiler_for(
-                run.builder.top_stage,
-                run.builder.config.host_target,
+            build_compiler: tool::LlvmBitcodeLinker::get_build_compiler_for_target(
+                run.builder,
                 run.target,
             ),
             target: run.target,
@@ -2369,13 +2375,10 @@ impl Step for LlvmBitcodeLinker {
     }
 
     fn run(self, builder: &Builder<'_>) -> Option<GeneratedTarball> {
-        let compiler = self.compiler;
         let target = self.target;
 
-        builder.ensure(compile::Rustc::new(compiler, target));
-
-        let llbc_linker =
-            builder.ensure(tool::LlvmBitcodeLinker { build_compiler: compiler, target });
+        let llbc_linker = builder
+            .ensure(tool::LlvmBitcodeLinker::from_build_compiler(self.build_compiler, target));
 
         let self_contained_bin_dir = format!("lib/rustlib/{}/bin/self-contained", target.triple);
 
diff --git a/src/bootstrap/src/core/build_steps/install.rs b/src/bootstrap/src/core/build_steps/install.rs
index 4434d6658eb..4156b49a8b3 100644
--- a/src/bootstrap/src/core/build_steps/install.rs
+++ b/src/bootstrap/src/core/build_steps/install.rs
@@ -287,7 +287,7 @@ install!((self, builder, _config),
         }
     };
     LlvmBitcodeLinker, alias = "llvm-bitcode-linker", Self::should_build(_config), only_hosts: true, {
-        if let Some(tarball) = builder.ensure(dist::LlvmBitcodeLinker { compiler: self.compiler, target: self.target }) {
+        if let Some(tarball) = builder.ensure(dist::LlvmBitcodeLinker { build_compiler: self.compiler, target: self.target }) {
             install_sh(builder, "llvm-bitcode-linker", self.compiler.stage, Some(self.target), &tarball);
         } else {
             builder.info(
diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index 9e7ea5c115f..98f11116279 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -2945,7 +2945,8 @@ impl Step for RemoteCopyLibs {
 
         builder.info(&format!("REMOTE copy libs to emulator ({target})"));
 
-        let remote_test_server = builder.ensure(tool::RemoteTestServer { compiler, target });
+        let remote_test_server =
+            builder.ensure(tool::RemoteTestServer { build_compiler: compiler, target });
 
         // Spawn the emulator and wait for it to come online
         let tool = builder.tool_exe(Tool::RemoteTestClient);
diff --git a/src/bootstrap/src/core/build_steps/tool.rs b/src/bootstrap/src/core/build_steps/tool.rs
index 1c994b0ccfc..f5fa33b98f3 100644
--- a/src/bootstrap/src/core/build_steps/tool.rs
+++ b/src/bootstrap/src/core/build_steps/tool.rs
@@ -42,7 +42,8 @@ pub enum ToolArtifactKind {
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 struct ToolBuild {
-    compiler: Compiler,
+    /// Compiler that will build this tool.
+    build_compiler: Compiler,
     target: TargetSelection,
     tool: &'static str,
     path: &'static str,
@@ -112,34 +113,34 @@ impl Step for ToolBuild {
         let mut tool = self.tool;
         let path = self.path;
 
-        let target_compiler = self.compiler;
-        self.compiler = if self.mode == Mode::ToolRustc {
-            get_tool_rustc_compiler(builder, self.compiler)
+        let target_compiler = self.build_compiler;
+        self.build_compiler = if self.mode == Mode::ToolRustc {
+            get_tool_rustc_compiler(builder, self.build_compiler)
         } else {
-            self.compiler
+            self.build_compiler
         };
 
         match self.mode {
             Mode::ToolRustc => {
                 // If compiler was forced, its artifacts should have been prepared earlier.
-                if !self.compiler.is_forced_compiler() {
-                    builder.std(self.compiler, self.compiler.host);
-                    builder.ensure(compile::Rustc::new(self.compiler, target));
+                if !self.build_compiler.is_forced_compiler() {
+                    builder.std(self.build_compiler, self.build_compiler.host);
+                    builder.ensure(compile::Rustc::new(self.build_compiler, target));
                 }
             }
             Mode::ToolStd => {
                 // If compiler was forced, its artifacts should have been prepared earlier.
-                if !self.compiler.is_forced_compiler() {
-                    builder.std(self.compiler, target)
+                if !self.build_compiler.is_forced_compiler() {
+                    builder.std(self.build_compiler, target);
                 }
             }
-            Mode::ToolBootstrap => {} // uses downloaded stage0 compiler libs
+            Mode::ToolBootstrap | Mode::ToolTarget => {} // uses downloaded stage0 compiler libs
             _ => panic!("unexpected Mode for tool build"),
         }
 
         let mut cargo = prepare_tool_cargo(
             builder,
-            self.compiler,
+            self.build_compiler,
             self.mode,
             target,
             Kind::Build,
@@ -161,7 +162,7 @@ impl Step for ToolBuild {
 
         // Rustc tools (miri, clippy, cargo, rustfmt, rust-analyzer)
         // could use the additional optimizations.
-        if self.mode == Mode::ToolRustc && is_lto_stage(&self.compiler) {
+        if self.mode == Mode::ToolRustc && is_lto_stage(&self.build_compiler) {
             let lto = match builder.config.rust_lto {
                 RustcLto::Off => Some("off"),
                 RustcLto::Thin => Some("thin"),
@@ -183,8 +184,9 @@ impl Step for ToolBuild {
             Kind::Build,
             self.mode,
             self.tool,
-            self.compiler.stage,
-            &self.compiler.host,
+            // A stage N tool is built with the stage N-1 compiler.
+            self.build_compiler.stage + 1,
+            &self.build_compiler.host,
             &self.target,
         );
 
@@ -207,14 +209,14 @@ impl Step for ToolBuild {
             }
             let tool_path = match self.artifact_kind {
                 ToolArtifactKind::Binary => {
-                    copy_link_tool_bin(builder, self.compiler, self.target, self.mode, tool)
+                    copy_link_tool_bin(builder, self.build_compiler, self.target, self.mode, tool)
                 }
                 ToolArtifactKind::Library => builder
-                    .cargo_out(self.compiler, self.mode, self.target)
+                    .cargo_out(self.build_compiler, self.mode, self.target)
                     .join(format!("lib{tool}.rlib")),
             };
 
-            ToolBuildResult { tool_path, build_compiler: self.compiler, target_compiler }
+            ToolBuildResult { tool_path, build_compiler: self.build_compiler, target_compiler }
         }
     }
 }
@@ -365,6 +367,47 @@ pub(crate) fn get_tool_rustc_compiler(
     builder.compiler(target_compiler.stage.saturating_sub(1), builder.config.host_target)
 }
 
+/// Determines how to build a `ToolTarget`, i.e. which compiler should be used to compile it.
+/// The compiler stage is automatically bumped if we need to cross-compile a stage 1 tool.
+pub enum ToolTargetBuildMode {
+    /// Build the tool using rustc that corresponds to the selected CLI stage.
+    Build(TargetSelection),
+    /// Build the tool so that it can be attached to the sysroot of the passed compiler.
+    /// Since we always dist stage 2+, the compiler that builds the tool in this case has to be
+    /// stage 1+.
+    Dist(Compiler),
+}
+
+/// Returns compiler that is able to compile a `ToolTarget` tool with the given `mode`.
+pub(crate) fn get_tool_target_compiler(
+    builder: &Builder<'_>,
+    mode: ToolTargetBuildMode,
+) -> Compiler {
+    let (target, build_compiler_stage) = match mode {
+        ToolTargetBuildMode::Build(target) => {
+            assert!(builder.top_stage > 0);
+            // If we want to build a stage N tool, we need to compile it with stage N-1 rustc
+            (target, builder.top_stage - 1)
+        }
+        ToolTargetBuildMode::Dist(target_compiler) => {
+            assert!(target_compiler.stage > 0);
+            // If we want to dist a stage N rustc, we want to attach stage N tool to it.
+            // And to build that tool, we need to compile it with stage N-1 rustc
+            (target_compiler.host, target_compiler.stage - 1)
+        }
+    };
+
+    let compiler = if builder.host_target == target {
+        builder.compiler(build_compiler_stage, builder.host_target)
+    } else {
+        // If we are cross-compiling a stage 1 tool, we cannot do that with a stage 0 compiler,
+        // so we auto-bump the tool's stage to 2, which means we need a stage 1 compiler.
+        builder.compiler(build_compiler_stage.max(1), builder.host_target)
+    };
+    builder.std(compiler, target);
+    compiler
+}
+
 /// Links a built tool binary with the given `name` from the build directory to the
 /// tools directory.
 fn copy_link_tool_bin(
@@ -451,7 +494,7 @@ macro_rules! bootstrap_tool {
                 let compiletest_wants_stage0 = $tool_name == "compiletest" && builder.config.compiletest_use_stage0_libtest;
 
                 builder.ensure(ToolBuild {
-                    compiler: self.compiler,
+                    build_compiler: self.compiler,
                     target: self.target,
                     tool: $tool_name,
                     mode: if is_unstable && !compiletest_wants_stage0 {
@@ -521,7 +564,6 @@ bootstrap_tool!(
     // rustdoc-gui-test has a crate dependency on compiletest, so it needs the same unstable features.
     RustdocGUITest, "src/tools/rustdoc-gui-test", "rustdoc-gui-test", is_unstable_tool = true, allow_features = COMPILETEST_ALLOW_FEATURES;
     CoverageDump, "src/tools/coverage-dump", "coverage-dump";
-    WasmComponentLd, "src/tools/wasm-component-ld", "wasm-component-ld", is_unstable_tool = true, allow_features = "min_specialization";
     UnicodeTableGenerator, "src/tools/unicode-table-generator", "unicode-table-generator";
     FeaturesStatusDump, "src/tools/features-status-dump", "features-status-dump";
     OptimizedDist, "src/tools/opt-dist", "opt-dist", submodules = &["src/tools/rustc-perf"];
@@ -560,7 +602,7 @@ impl Step for RustcPerf {
         builder.require_submodule("src/tools/rustc-perf", None);
 
         let tool = ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.compiler,
             target: self.target,
             tool: "collector",
             mode: Mode::ToolBootstrap,
@@ -576,7 +618,7 @@ impl Step for RustcPerf {
         let res = builder.ensure(tool.clone());
         // We also need to symlink the `rustc-fake` binary to the corresponding directory,
         // because `collector` expects it in the same directory.
-        copy_link_tool_bin(builder, tool.compiler, tool.target, tool.mode, "rustc-fake");
+        copy_link_tool_bin(builder, tool.build_compiler, tool.target, tool.mode, "rustc-fake");
 
         res
     }
@@ -620,7 +662,7 @@ impl Step for ErrorIndex {
 
     fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
         builder.ensure(ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.compiler,
             target: self.compiler.host,
             tool: "error_index_generator",
             mode: Mode::ToolRustc,
@@ -636,7 +678,7 @@ impl Step for ErrorIndex {
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct RemoteTestServer {
-    pub compiler: Compiler,
+    pub build_compiler: Compiler,
     pub target: TargetSelection,
 }
 
@@ -649,17 +691,20 @@ impl Step for RemoteTestServer {
 
     fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(RemoteTestServer {
-            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.host_target),
+            build_compiler: get_tool_target_compiler(
+                run.builder,
+                ToolTargetBuildMode::Build(run.target),
+            ),
             target: run.target,
         });
     }
 
     fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
         builder.ensure(ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.build_compiler,
             target: self.target,
             tool: "remote-test-server",
-            mode: Mode::ToolStd,
+            mode: Mode::ToolTarget,
             path: "src/tools/remote-test-server",
             source_type: SourceType::InTree,
             extra_features: Vec::new(),
@@ -668,6 +713,10 @@ impl Step for RemoteTestServer {
             artifact_kind: ToolArtifactKind::Binary,
         })
     }
+
+    fn metadata(&self) -> Option<StepMetadata> {
+        Some(StepMetadata::build("remote-test-server", self.target).built_by(self.build_compiler))
+    }
 }
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
@@ -757,7 +806,7 @@ impl Step for Rustdoc {
 
         let ToolBuildResult { tool_path, build_compiler, target_compiler } =
             builder.ensure(ToolBuild {
-                compiler: target_compiler,
+                build_compiler: target_compiler,
                 target,
                 // Cargo adds a number of paths to the dylib search path on windows, which results in
                 // the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
@@ -825,7 +874,7 @@ impl Step for Cargo {
         builder.build.require_submodule("src/tools/cargo", None);
 
         builder.ensure(ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.compiler,
             target: self.target,
             tool: "cargo",
             mode: Mode::ToolRustc,
@@ -839,17 +888,50 @@ impl Step for Cargo {
     }
 }
 
+/// Represents a built LldWrapper, the `lld-wrapper` tool itself, and a directory
+/// containing a build of LLD.
+#[derive(Clone)]
+pub struct BuiltLldWrapper {
+    tool: ToolBuildResult,
+    lld_dir: PathBuf,
+}
+
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct LldWrapper {
     pub build_compiler: Compiler,
-    pub target_compiler: Compiler,
+    pub target: TargetSelection,
+}
+
+impl LldWrapper {
+    /// Returns `LldWrapper` that should be **used** by the passed compiler.
+    pub fn for_use_by_compiler(builder: &Builder<'_>, target_compiler: Compiler) -> Self {
+        Self {
+            build_compiler: get_tool_target_compiler(
+                builder,
+                ToolTargetBuildMode::Dist(target_compiler),
+            ),
+            target: target_compiler.host,
+        }
+    }
 }
 
 impl Step for LldWrapper {
-    type Output = ToolBuildResult;
+    type Output = BuiltLldWrapper;
+
+    const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.never()
+        run.path("src/tools/lld-wrapper")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(LldWrapper {
+            build_compiler: get_tool_target_compiler(
+                run.builder,
+                ToolTargetBuildMode::Build(run.target),
+            ),
+            target: run.target,
+        });
     }
 
     #[cfg_attr(
@@ -858,25 +940,16 @@ impl Step for LldWrapper {
             level = "debug",
             name = "LldWrapper::run",
             skip_all,
-            fields(build_compiler = ?self.build_compiler, target_compiler = ?self.target_compiler),
+            fields(build_compiler = ?self.build_compiler),
         ),
     )]
-    fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
-        if builder.config.dry_run() {
-            return ToolBuildResult {
-                tool_path: Default::default(),
-                build_compiler: self.build_compiler,
-                target_compiler: self.target_compiler,
-            };
-        }
-
-        let target = self.target_compiler.host;
-
-        let tool_result = builder.ensure(ToolBuild {
-            compiler: self.build_compiler,
-            target,
+    fn run(self, builder: &Builder<'_>) -> Self::Output {
+        let lld_dir = builder.ensure(llvm::Lld { target: self.target });
+        let tool = builder.ensure(ToolBuild {
+            build_compiler: self.build_compiler,
+            target: self.target,
             tool: "lld-wrapper",
-            mode: Mode::ToolStd,
+            mode: Mode::ToolTarget,
             path: "src/tools/lld-wrapper",
             source_type: SourceType::InTree,
             extra_features: Vec::new(),
@@ -884,38 +957,110 @@ impl Step for LldWrapper {
             cargo_args: Vec::new(),
             artifact_kind: ToolArtifactKind::Binary,
         });
+        BuiltLldWrapper { tool, lld_dir }
+    }
 
-        let libdir_bin = builder.sysroot_target_bindir(self.target_compiler, target);
-        t!(fs::create_dir_all(&libdir_bin));
+    fn metadata(&self) -> Option<StepMetadata> {
+        Some(StepMetadata::build("LldWrapper", self.target).built_by(self.build_compiler))
+    }
+}
 
-        let lld_install = builder.ensure(llvm::Lld { target });
-        let src_exe = exe("lld", target);
-        let dst_exe = exe("rust-lld", target);
+pub(crate) fn copy_lld_artifacts(
+    builder: &Builder<'_>,
+    lld_wrapper: BuiltLldWrapper,
+    target_compiler: Compiler,
+) {
+    let target = target_compiler.host;
 
+    let libdir_bin = builder.sysroot_target_bindir(target_compiler, target);
+    t!(fs::create_dir_all(&libdir_bin));
+
+    let src_exe = exe("lld", target);
+    let dst_exe = exe("rust-lld", target);
+
+    builder.copy_link(
+        &lld_wrapper.lld_dir.join("bin").join(src_exe),
+        &libdir_bin.join(dst_exe),
+        FileType::Executable,
+    );
+    let self_contained_lld_dir = libdir_bin.join("gcc-ld");
+    t!(fs::create_dir_all(&self_contained_lld_dir));
+
+    for name in crate::LLD_FILE_NAMES {
         builder.copy_link(
-            &lld_install.join("bin").join(src_exe),
-            &libdir_bin.join(dst_exe),
+            &lld_wrapper.tool.tool_path,
+            &self_contained_lld_dir.join(exe(name, target)),
             FileType::Executable,
         );
-        let self_contained_lld_dir = libdir_bin.join("gcc-ld");
-        t!(fs::create_dir_all(&self_contained_lld_dir));
-
-        for name in crate::LLD_FILE_NAMES {
-            builder.copy_link(
-                &tool_result.tool_path,
-                &self_contained_lld_dir.join(exe(name, target)),
-                FileType::Executable,
-            );
+    }
+}
+
+/// Builds the `wasm-component-ld` linker wrapper, which is shipped with rustc to be executed on the
+/// host platform where rustc runs.
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+pub struct WasmComponentLd {
+    build_compiler: Compiler,
+    target: TargetSelection,
+}
+
+impl WasmComponentLd {
+    /// Returns `WasmComponentLd` that should be **used** by the passed compiler.
+    pub fn for_use_by_compiler(builder: &Builder<'_>, target_compiler: Compiler) -> Self {
+        Self {
+            build_compiler: get_tool_target_compiler(
+                builder,
+                ToolTargetBuildMode::Dist(target_compiler),
+            ),
+            target: target_compiler.host,
         }
+    }
+}
+
+impl Step for WasmComponentLd {
+    type Output = ToolBuildResult;
+
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/wasm-component-ld")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(WasmComponentLd {
+            build_compiler: get_tool_target_compiler(
+                run.builder,
+                ToolTargetBuildMode::Build(run.target),
+            ),
+            target: run.target,
+        });
+    }
 
-        tool_result
+    #[cfg_attr(
+        feature = "tracing",
+        instrument(
+            level = "debug",
+            name = "WasmComponentLd::run",
+            skip_all,
+            fields(build_compiler = ?self.build_compiler),
+        ),
+    )]
+    fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
+        builder.ensure(ToolBuild {
+            build_compiler: self.build_compiler,
+            target: self.target,
+            tool: "wasm-component-ld",
+            mode: Mode::ToolTarget,
+            path: "src/tools/wasm-component-ld",
+            source_type: SourceType::InTree,
+            extra_features: vec![],
+            allow_features: "",
+            cargo_args: vec![],
+            artifact_kind: ToolArtifactKind::Binary,
+        })
     }
 
     fn metadata(&self) -> Option<StepMetadata> {
-        Some(
-            StepMetadata::build("LldWrapper", self.target_compiler.host)
-                .built_by(self.build_compiler),
-        )
+        Some(StepMetadata::build("WasmComponentLd", self.target).built_by(self.build_compiler))
     }
 }
 
@@ -948,7 +1093,7 @@ impl Step for RustAnalyzer {
 
     fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
         builder.ensure(ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.compiler,
             target: self.target,
             tool: "rust-analyzer",
             mode: Mode::ToolRustc,
@@ -993,7 +1138,7 @@ impl Step for RustAnalyzerProcMacroSrv {
 
     fn run(self, builder: &Builder<'_>) -> Option<ToolBuildResult> {
         let tool_result = builder.ensure(ToolBuild {
-            compiler: self.compiler,
+            build_compiler: self.compiler,
             target: self.target,
             tool: "rust-analyzer-proc-macro-srv",
             mode: Mode::ToolRustc,
@@ -1021,8 +1166,35 @@ impl Step for RustAnalyzerProcMacroSrv {
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct LlvmBitcodeLinker {
-    pub build_compiler: Compiler,
-    pub target: TargetSelection,
+    build_compiler: Compiler,
+    target: TargetSelection,
+}
+
+impl LlvmBitcodeLinker {
+    /// Returns `LlvmBitcodeLinker` that will be **compiled** by the passed compiler, for the given
+    /// `target`.
+    pub fn from_build_compiler(build_compiler: Compiler, target: TargetSelection) -> Self {
+        Self { build_compiler, target }
+    }
+
+    /// Returns `LlvmBitcodeLinker` that should be **used** by the passed compiler.
+    pub fn from_target_compiler(builder: &Builder<'_>, target_compiler: Compiler) -> Self {
+        Self {
+            build_compiler: get_tool_target_compiler(
+                builder,
+                ToolTargetBuildMode::Dist(target_compiler),
+            ),
+            target: target_compiler.host,
+        }
+    }
+
+    /// Return a compiler that is able to build this tool for the given `target`.
+    pub fn get_build_compiler_for_target(
+        builder: &Builder<'_>,
+        target: TargetSelection,
+    ) -> Compiler {
+        get_tool_target_compiler(builder, ToolTargetBuildMode::Build(target))
+    }
 }
 
 impl Step for LlvmBitcodeLinker {
@@ -1038,9 +1210,7 @@ impl Step for LlvmBitcodeLinker {
 
     fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(LlvmBitcodeLinker {
-            build_compiler: run
-                .builder
-                .compiler(run.builder.top_stage, run.builder.config.host_target),
+            build_compiler: Self::get_build_compiler_for_target(run.builder, run.target),
             target: run.target,
         });
     }
@@ -1051,10 +1221,10 @@ impl Step for LlvmBitcodeLinker {
     )]
     fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
         builder.ensure(ToolBuild {
-            compiler: self.build_compiler,
+            build_compiler: self.build_compiler,
             target: self.target,
             tool: "llvm-bitcode-linker",
-            mode: Mode::ToolRustc,
+            mode: Mode::ToolTarget,
             path: "src/tools/llvm-bitcode-linker",
             source_type: SourceType::InTree,
             extra_features: vec![],
@@ -1239,7 +1409,7 @@ fn run_tool_build_step(
 
     let ToolBuildResult { tool_path, build_compiler, target_compiler } =
         builder.ensure(ToolBuild {
-            compiler,
+            build_compiler: compiler,
             target,
             tool: tool_name,
             mode: Mode::ToolRustc,
@@ -1338,7 +1508,7 @@ impl Step for TestFloatParse {
         let compiler = builder.compiler(builder.top_stage, bootstrap_host);
 
         builder.ensure(ToolBuild {
-            compiler,
+            build_compiler: compiler,
             target: bootstrap_host,
             tool: "test-float-parse",
             mode: Mode::ToolStd,
diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index a3b471ca56e..badd5f24dba 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -537,7 +537,7 @@ impl Builder<'_> {
             }
         }
 
-        let stage = if compiler.stage == 0 && self.local_rebuild {
+        let build_compiler_stage = if compiler.stage == 0 && self.local_rebuild {
             // Assume the local-rebuild rustc already has stage1 features.
             1
         } else {
@@ -545,15 +545,17 @@ impl Builder<'_> {
         };
 
         // We synthetically interpret a stage0 compiler used to build tools as a
-        // "raw" compiler in that it's the exact snapshot we download. Normally
-        // the stage0 build means it uses libraries build by the stage0
-        // compiler, but for tools we just use the precompiled libraries that
-        // we've downloaded
-        let use_snapshot = mode == Mode::ToolBootstrap;
-        assert!(!use_snapshot || stage == 0 || self.local_rebuild);
-
-        let maybe_sysroot = self.sysroot(compiler);
-        let sysroot = if use_snapshot { self.rustc_snapshot_sysroot() } else { &maybe_sysroot };
+        // "raw" compiler in that it's the exact snapshot we download. For things like
+        // ToolRustc, we would have to use the artificial stage0-sysroot compiler instead.
+        let use_snapshot =
+            mode == Mode::ToolBootstrap || (mode == Mode::ToolTarget && build_compiler_stage == 0);
+        assert!(!use_snapshot || build_compiler_stage == 0 || self.local_rebuild);
+
+        let sysroot = if use_snapshot {
+            self.rustc_snapshot_sysroot().to_path_buf()
+        } else {
+            self.sysroot(compiler)
+        };
         let libdir = self.rustc_libdir(compiler);
 
         let sysroot_str = sysroot.as_os_str().to_str().expect("sysroot should be UTF-8");
@@ -562,7 +564,7 @@ impl Builder<'_> {
         }
 
         let mut rustflags = Rustflags::new(target);
-        if stage != 0 {
+        if build_compiler_stage != 0 {
             if let Ok(s) = env::var("CARGOFLAGS_NOT_BOOTSTRAP") {
                 cargo.args(s.split_whitespace());
             }
@@ -604,7 +606,7 @@ impl Builder<'_> {
         // sysroot. Passing this cfg enables raw-dylib support instead, which makes the native
         // library unnecessary. This can be removed when windows-rs enables raw-dylib
         // unconditionally.
-        if let Mode::Rustc | Mode::ToolRustc | Mode::ToolBootstrap = mode {
+        if let Mode::Rustc | Mode::ToolRustc | Mode::ToolBootstrap | Mode::ToolTarget = mode {
             rustflags.arg("--cfg=windows_raw_dylib");
         }
 
@@ -657,7 +659,7 @@ impl Builder<'_> {
         // FIXME(rust-lang/cargo#5754) we shouldn't be using special command arguments
         // to the host invocation here, but rather Cargo should know what flags to pass rustc
         // itself.
-        if stage == 0 {
+        if build_compiler_stage == 0 {
             hostflags.arg("--cfg=bootstrap");
         }
 
@@ -666,7 +668,7 @@ impl Builder<'_> {
         // #71458.
         let mut rustdocflags = rustflags.clone();
         rustdocflags.propagate_cargo_env("RUSTDOCFLAGS");
-        if stage == 0 {
+        if build_compiler_stage == 0 {
             rustdocflags.env("RUSTDOCFLAGS_BOOTSTRAP");
         } else {
             rustdocflags.env("RUSTDOCFLAGS_NOT_BOOTSTRAP");
@@ -677,7 +679,7 @@ impl Builder<'_> {
         }
 
         match mode {
-            Mode::Std | Mode::ToolBootstrap | Mode::ToolStd => {}
+            Mode::Std | Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolTarget => {}
             Mode::Rustc | Mode::Codegen | Mode::ToolRustc => {
                 // Build proc macros both for the host and the target unless proc-macros are not
                 // supported by the target.
@@ -719,7 +721,7 @@ impl Builder<'_> {
         // feature on the rustc side.
         cargo.arg("-Zbinary-dep-depinfo");
         let allow_features = match mode {
-            Mode::ToolBootstrap | Mode::ToolStd => {
+            Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolTarget => {
                 // Restrict the allowed features so we don't depend on nightly
                 // accidentally.
                 //
@@ -833,7 +835,7 @@ impl Builder<'_> {
         cargo
             .env("RUSTBUILD_NATIVE_DIR", self.native_dir(target))
             .env("RUSTC_REAL", self.rustc(compiler))
-            .env("RUSTC_STAGE", stage.to_string())
+            .env("RUSTC_STAGE", build_compiler_stage.to_string())
             .env("RUSTC_SYSROOT", sysroot)
             .env("RUSTC_LIBDIR", libdir)
             .env("RUSTDOC", self.bootstrap_out.join("rustdoc"))
@@ -878,7 +880,7 @@ impl Builder<'_> {
         let debuginfo_level = match mode {
             Mode::Rustc | Mode::Codegen => self.config.rust_debuginfo_level_rustc,
             Mode::Std => self.config.rust_debuginfo_level_std,
-            Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolRustc => {
+            Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolRustc | Mode::ToolTarget => {
                 self.config.rust_debuginfo_level_tools
             }
         };
@@ -890,11 +892,10 @@ impl Builder<'_> {
             profile_var("DEBUG_ASSERTIONS"),
             match mode {
                 Mode::Std => self.config.std_debug_assertions,
-                Mode::Rustc => self.config.rustc_debug_assertions,
-                Mode::Codegen => self.config.rustc_debug_assertions,
-                Mode::ToolBootstrap => self.config.tools_debug_assertions,
-                Mode::ToolStd => self.config.tools_debug_assertions,
-                Mode::ToolRustc => self.config.tools_debug_assertions,
+                Mode::Rustc | Mode::Codegen => self.config.rustc_debug_assertions,
+                Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolRustc | Mode::ToolTarget => {
+                    self.config.tools_debug_assertions
+                }
             }
             .to_string(),
         );
@@ -965,7 +966,11 @@ impl Builder<'_> {
                     cargo.env("CFG_VIRTUAL_RUSTC_DEV_SOURCE_BASE_DIR", map_to);
                 }
             }
-            Mode::Std | Mode::ToolBootstrap | Mode::ToolRustc | Mode::ToolStd => {
+            Mode::Std
+            | Mode::ToolBootstrap
+            | Mode::ToolRustc
+            | Mode::ToolStd
+            | Mode::ToolTarget => {
                 if let Some(ref map_to) =
                     self.build.debuginfo_map_to(GitRepo::Rustc, RemapScheme::NonCompiler)
                 {
@@ -1280,7 +1285,7 @@ impl Builder<'_> {
             };
 
             if let Some(limit) = limit
-                && (stage == 0
+                && (build_compiler_stage == 0
                     || self.config.default_codegen_backend(target).unwrap_or_default() == "llvm")
             {
                 rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={limit}"));
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index 1b75d00b30e..d73e2bce25b 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -963,6 +963,7 @@ impl<'a> Builder<'a> {
                 tool::RemoteTestServer,
                 tool::RemoteTestClient,
                 tool::RustInstaller,
+                tool::FeaturesStatusDump,
                 tool::Cargo,
                 tool::RustAnalyzer,
                 tool::RustAnalyzerProcMacroSrv,
@@ -984,6 +985,8 @@ impl<'a> Builder<'a> {
                 tool::CoverageDump,
                 tool::LlvmBitcodeLinker,
                 tool::RustcPerf,
+                tool::WasmComponentLd,
+                tool::LldWrapper
             ),
             Kind::Clippy => describe!(
                 clippy::Std,
diff --git a/src/bootstrap/src/core/builder/tests.rs b/src/bootstrap/src/core/builder/tests.rs
index 51a90649692..2f8cdd2f8c8 100644
--- a/src/bootstrap/src/core/builder/tests.rs
+++ b/src/bootstrap/src/core/builder/tests.rs
@@ -769,11 +769,11 @@ mod snapshot {
         [build] llvm <host>
         [build] rustc 0 <host> -> rustc 1 <host>
         [build] rustc 0 <host> -> LldWrapper 1 <host>
-        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
+        [build] rustc 0 <host> -> LlvmBitcodeLinker 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
         [build] rustc 1 <host> -> rustc 2 <host>
         [build] rustc 1 <host> -> LldWrapper 2 <host>
-        [build] rustc 2 <host> -> LlvmBitcodeLinker 3 <host>
+        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
         [build] rustc 2 <host> -> std 2 <host>
         [build] rustdoc 1 <host>
         "
@@ -793,17 +793,17 @@ mod snapshot {
         [build] llvm <host>
         [build] rustc 0 <host> -> rustc 1 <host>
         [build] rustc 0 <host> -> LldWrapper 1 <host>
-        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
+        [build] rustc 0 <host> -> LlvmBitcodeLinker 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
         [build] rustc 1 <host> -> rustc 2 <host>
         [build] rustc 1 <host> -> LldWrapper 2 <host>
-        [build] rustc 2 <host> -> LlvmBitcodeLinker 3 <host>
+        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
         [build] rustc 1 <host> -> std 1 <target1>
         [build] rustc 2 <host> -> std 2 <target1>
         [build] llvm <target1>
         [build] rustc 1 <host> -> rustc 2 <target1>
         [build] rustc 1 <host> -> LldWrapper 2 <target1>
-        [build] rustc 2 <target1> -> LlvmBitcodeLinker 3 <target1>
+        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <target1>
         [build] rustdoc 1 <target1>
         "
         );
@@ -1062,18 +1062,28 @@ mod snapshot {
     fn dist_extended() {
         let ctx = TestCtx::new();
         insta::assert_snapshot!(
-            ctx
-                .config("dist")
-                .args(&["--set", "build.extended=true"])
-                .render_steps(), @r"
+            ctx.config("dist")
+            .args(&[
+                "--set",
+                "build.extended=true",
+                "--set",
+                "rust.llvm-bitcode-linker=true",
+                "--set",
+                "rust.lld=true",
+            ])
+            .render_steps(), @r"
         [build] rustc 0 <host> -> UnstableBookGen 1 <host>
         [build] rustc 0 <host> -> Rustbook 1 <host>
         [build] llvm <host>
         [build] rustc 0 <host> -> rustc 1 <host>
+        [build] rustc 0 <host> -> LldWrapper 1 <host>
         [build] rustc 0 <host> -> WasmComponentLd 1 <host>
+        [build] rustc 0 <host> -> LlvmBitcodeLinker 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
         [build] rustc 1 <host> -> rustc 2 <host>
+        [build] rustc 1 <host> -> LldWrapper 2 <host>
         [build] rustc 1 <host> -> WasmComponentLd 2 <host>
+        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
         [build] rustdoc 1 <host>
         [doc] std 2 <host> crates=[alloc,compiler_builtins,core,panic_abort,panic_unwind,proc_macro,std,sysroot,test,unwind]
         [build] rustc 2 <host> -> std 2 <host>
@@ -1092,7 +1102,6 @@ mod snapshot {
         [build] rustc 0 <host> -> cargo-clippy 1 <host>
         [build] rustc 0 <host> -> miri 1 <host>
         [build] rustc 0 <host> -> cargo-miri 1 <host>
-        [build] rustc 1 <host> -> LlvmBitcodeLinker 2 <host>
         ");
     }
 
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 44be51815c7..63aab4d116a 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -253,12 +253,24 @@ pub enum Mode {
     /// These tools are intended to be only executed on the host system that
     /// invokes bootstrap, and they thus cannot be cross-compiled.
     ///
-    /// They are always built using the stage0 compiler, and typically they
+    /// They are always built using the stage0 compiler, and they
     /// can be compiled with stable Rust.
     ///
     /// These tools also essentially do not participate in staging.
     ToolBootstrap,
 
+    /// Build a cross-compilable helper tool. These tools do not depend on unstable features or
+    /// compiler internals, but they might be cross-compilable (so we cannot build them using the
+    /// stage0 compiler, unlike `ToolBootstrap`).
+    ///
+    /// Some of these tools are also shipped in our `dist` archives.
+    /// While we could compile them using the stage0 compiler when not cross-compiling, we instead
+    /// use the in-tree compiler (and std) to build them, so that we can ship e.g. std security
+    /// fixes and avoid depending fully on stage0 for the artifacts that we ship.
+    ///
+    /// This mode is used e.g. for linkers and linker tools invoked by rustc on its host target.
+    ToolTarget,
+
     /// Build a tool which uses the locally built std, placing output in the
     /// "stageN-tools" directory. Its usage is quite rare, mainly used by
     /// compiletest which needs libtest.
@@ -273,11 +285,21 @@ pub enum Mode {
 
 impl Mode {
     pub fn is_tool(&self) -> bool {
-        matches!(self, Mode::ToolBootstrap | Mode::ToolRustc | Mode::ToolStd)
+        match self {
+            Mode::ToolBootstrap | Mode::ToolRustc | Mode::ToolStd | Mode::ToolTarget => true,
+            Mode::Std | Mode::Codegen | Mode::Rustc => false,
+        }
     }
 
     pub fn must_support_dlopen(&self) -> bool {
-        matches!(self, Mode::Std | Mode::Codegen)
+        match self {
+            Mode::Std | Mode::Codegen => true,
+            Mode::ToolBootstrap
+            | Mode::ToolRustc
+            | Mode::ToolStd
+            | Mode::ToolTarget
+            | Mode::Rustc => false,
+        }
     }
 }
 
@@ -802,17 +824,39 @@ impl Build {
     /// stage when running with a particular host compiler.
     ///
     /// The mode indicates what the root directory is for.
-    fn stage_out(&self, compiler: Compiler, mode: Mode) -> PathBuf {
-        let suffix = match mode {
-            Mode::Std => "-std",
-            Mode::Rustc => "-rustc",
-            Mode::Codegen => "-codegen",
-            Mode::ToolBootstrap => {
-                return self.out.join(compiler.host).join("bootstrap-tools");
+    fn stage_out(&self, build_compiler: Compiler, mode: Mode) -> PathBuf {
+        use std::fmt::Write;
+
+        fn bootstrap_tool() -> (Option<u32>, &'static str) {
+            (None, "bootstrap-tools")
+        }
+        fn staged_tool(build_compiler: Compiler) -> (Option<u32>, &'static str) {
+            (Some(build_compiler.stage), "tools")
+        }
+
+        let (stage, suffix) = match mode {
+            Mode::Std => (Some(build_compiler.stage), "std"),
+            Mode::Rustc => (Some(build_compiler.stage), "rustc"),
+            Mode::Codegen => (Some(build_compiler.stage), "codegen"),
+            Mode::ToolBootstrap => bootstrap_tool(),
+            Mode::ToolStd | Mode::ToolRustc => (Some(build_compiler.stage), "tools"),
+            Mode::ToolTarget => {
+                // If we're not cross-compiling (the common case), share the target directory with
+                // bootstrap tools to reuse the build cache.
+                if build_compiler.stage == 0 {
+                    bootstrap_tool()
+                } else {
+                    staged_tool(build_compiler)
+                }
             }
-            Mode::ToolStd | Mode::ToolRustc => "-tools",
         };
-        self.out.join(compiler.host).join(format!("stage{}{}", compiler.stage, suffix))
+        let path = self.out.join(build_compiler.host);
+        let mut dir_name = String::new();
+        if let Some(stage) = stage {
+            write!(dir_name, "stage{stage}-").unwrap();
+        }
+        dir_name.push_str(suffix);
+        path.join(dir_name)
     }
 
     /// Returns the root output directory for all Cargo output in a given stage,