Tools built by the bootstrap compiler must be built by it

This avoids building compilers that we don't need -- most tools will work
just fine with the downloaded compiler.

Author: Mark-Simulacrum

src/bootstrap/doc.rs

@@ -883,7 +883,11 @@ impl Step for ErrorIndex {
         builder.info(&format!("Documenting error index ({})", target));
         let out = builder.doc_out(target);
         t!(fs::create_dir_all(&out));
-        let mut index = builder.tool_cmd(Tool::ErrorIndex);
+        let compiler = builder.compiler(2, builder.config.build);
+        let mut index = tool::ErrorIndex::command(
+            builder,
+            compiler,
+        );
         index.arg("html");
         index.arg(out.join("error-index.html"));
 

src/bootstrap/test.rs

@@ -414,7 +414,6 @@ impl Step for Miri {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct CompiletestTest {
-    stage: u32,
     host: Interned<String>,
 }
 
@@ -427,16 +426,14 @@ impl Step for CompiletestTest {
 
     fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(CompiletestTest {
-            stage: run.builder.top_stage,
             host: run.target,
         });
     }
 
     /// Runs `cargo test` for compiletest.
     fn run(self, builder: &Builder<'_>) {
-        let stage = self.stage;
         let host = self.host;
-        let compiler = builder.compiler(stage, host);
+        let compiler = builder.compiler(0, host);
 
         let mut cargo = tool::prepare_tool_cargo(builder,
                                                  compiler,
@@ -1426,7 +1423,10 @@ impl Step for ErrorIndex {
         t!(fs::create_dir_all(&dir));
         let output = dir.join("error-index.md");
 
-        let mut tool = builder.tool_cmd(Tool::ErrorIndex);
+        let mut tool = tool::ErrorIndex::command(
+            builder,
+            builder.compiler(compiler.stage, builder.config.build),
+        );
         tool.arg("markdown")
             .arg(&output)
             .env("CFG_BUILD", &builder.config.build)

src/bootstrap/tool.rs

@@ -250,9 +250,9 @@ pub fn prepare_tool_cargo(
     cargo
 }
 
-macro_rules! tool {
+macro_rules! bootstrap_tool {
     ($(
-        $name:ident, $path:expr, $tool_name:expr, $mode:expr
+        $name:ident, $path:expr, $tool_name:expr
         $(,llvm_tools = $llvm:expr)*
         $(,is_external_tool = $external:expr)*
         ;
@@ -266,10 +266,7 @@ macro_rules! tool {
 
         impl Tool {
             pub fn get_mode(&self) -> Mode {
-                let mode = match self {
-                    $(Tool::$name => $mode,)+
-                };
-                mode
+                Mode::ToolBootstrap
             }
 
             /// Whether this tool requires LLVM to run
@@ -282,27 +279,15 @@ macro_rules! tool {
 
         impl<'a> Builder<'a> {
             pub fn tool_exe(&self, tool: Tool) -> PathBuf {
-                let stage = self.tool_default_stage(tool);
                 match tool {
                     $(Tool::$name =>
                         self.ensure($name {
-                            compiler: self.compiler(stage, self.config.build),
+                            compiler: self.compiler(0, self.config.build),
                             target: self.config.build,
                         }),
                     )+
                 }
             }
-
-            pub fn tool_default_stage(&self, tool: Tool) -> u32 {
-                // Compile the error-index in the same stage as rustdoc to avoid
-                // recompiling rustdoc twice if we can. Otherwise compile
-                // everything else in stage0 as there's no need to rebootstrap
-                // everything.
-                match tool {
-                    Tool::ErrorIndex if self.top_stage >= 2 => self.top_stage,
-                    _ => 0,
-                }
-            }
         }
 
         $(
@@ -321,7 +306,8 @@ macro_rules! tool {
 
             fn make_run(run: RunConfig<'_>) {
                 run.builder.ensure($name {
-                    compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
+                    // snapshot compiler
+                    compiler: run.builder.compiler(0, run.builder.config.build),
                     target: run.target,
                 });
             }
@@ -331,7 +317,7 @@ macro_rules! tool {
                     compiler: self.compiler,
                     target: self.target,
                     tool: $tool_name,
-                    mode: $mode,
+                    mode: Mode::ToolBootstrap,
                     path: $path,
                     is_optional_tool: false,
                     source_type: if false $(|| $external)* {
@@ -347,21 +333,67 @@ macro_rules! tool {
     }
 }
 
-tool!(
-    Rustbook, "src/tools/rustbook", "rustbook", Mode::ToolBootstrap;
-    ErrorIndex, "src/tools/error_index_generator", "error_index_generator", Mode::ToolRustc;
-    UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen", Mode::ToolBootstrap;
-    Tidy, "src/tools/tidy", "tidy", Mode::ToolBootstrap;
-    Linkchecker, "src/tools/linkchecker", "linkchecker", Mode::ToolBootstrap;
-    CargoTest, "src/tools/cargotest", "cargotest", Mode::ToolBootstrap;
-    Compiletest, "src/tools/compiletest", "compiletest", Mode::ToolBootstrap, llvm_tools = true;
-    BuildManifest, "src/tools/build-manifest", "build-manifest", Mode::ToolBootstrap;
-    RemoteTestClient, "src/tools/remote-test-client", "remote-test-client", Mode::ToolBootstrap;
-    RustInstaller, "src/tools/rust-installer", "fabricate", Mode::ToolBootstrap,
-        is_external_tool = true;
-    RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes", Mode::ToolBootstrap;
+bootstrap_tool!(
+    Rustbook, "src/tools/rustbook", "rustbook";
+    UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen";
+    Tidy, "src/tools/tidy", "tidy";
+    Linkchecker, "src/tools/linkchecker", "linkchecker";
+    CargoTest, "src/tools/cargotest", "cargotest";
+    Compiletest, "src/tools/compiletest", "compiletest", llvm_tools = true;
+    BuildManifest, "src/tools/build-manifest", "build-manifest";
+    RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
+    RustInstaller, "src/tools/rust-installer", "fabricate", is_external_tool = true;
+    RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes";
 );
 
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+pub struct ErrorIndex {
+    pub compiler: Compiler,
+}
+
+impl ErrorIndex {
+    pub fn command(builder: &Builder<'_>, compiler: Compiler) -> Command {
+        let mut cmd = Command::new(builder.ensure(ErrorIndex {
+            compiler
+        }));
+        add_lib_path(
+            vec![PathBuf::from(&builder.sysroot_libdir(compiler, compiler.host))],
+            &mut cmd,
+        );
+        cmd
+    }
+}
+
+impl Step for ErrorIndex {
+    type Output = PathBuf;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/error_index_generator")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        // Compile the error-index in the same stage as rustdoc to avoid
+        // recompiling rustdoc twice if we can.
+        let stage = if run.builder.top_stage >= 2 { run.builder.top_stage } else { 0 };
+        run.builder.ensure(ErrorIndex {
+            compiler: run.builder.compiler(stage, run.builder.config.build),
+        });
+    }
+
+    fn run(self, builder: &Builder<'_>) -> PathBuf {
+        builder.ensure(ToolBuild {
+            compiler: self.compiler,
+            target: self.compiler.host,
+            tool: "error_index_generator",
+            mode: Mode::ToolRustc,
+            path: "src/tools/error_index_generator",
+            is_optional_tool: false,
+            source_type: SourceType::InTree,
+            extra_features: Vec::new(),
+        }).expect("expected to build -- essential tool")
+    }
+}
+
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct RemoteTestServer {
     pub compiler: Compiler,
@@ -625,7 +657,7 @@ impl<'a> Builder<'a> {
     /// `host`.
     pub fn tool_cmd(&self, tool: Tool) -> Command {
         let mut cmd = Command::new(self.tool_exe(tool));
-        let compiler = self.compiler(self.tool_default_stage(tool), self.config.build);
+        let compiler = self.compiler(0, self.config.build);
         self.prepare_tool_cmd(compiler, tool, &mut cmd);
         cmd
     }
@@ -637,7 +669,7 @@ impl<'a> Builder<'a> {
     fn prepare_tool_cmd(&self, compiler: Compiler, tool: Tool, cmd: &mut Command) {
         let host = &compiler.host;
         let mut lib_paths: Vec<PathBuf> = vec![
-            if compiler.stage == 0 && tool != Tool::ErrorIndex {
+            if compiler.stage == 0 {
                 self.build.rustc_snapshot_libdir()
             } else {
                 PathBuf::from(&self.sysroot_libdir(compiler, compiler.host))