diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index c9c9c73c84af2..9300b94156acb 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -806,7 +806,7 @@ impl<'a> Builder<'a> {
             );
         }
 
-        if mode == Mode::Tool {
+        if mode.is_tool() {
             // Tools like cargo and rls don't get debuginfo by default right now, but this can be
             // enabled in the config.  Adding debuginfo makes them several times larger.
             if self.config.rust_debuginfo_tools {
@@ -871,7 +871,7 @@ impl<'a> Builder<'a> {
         //
         // If LLVM support is disabled we need to use the snapshot compiler to compile
         // build scripts, as the new compiler doesn't support executables.
-        if mode == Mode::Libstd || !self.config.llvm_enabled {
+        if mode == Mode::Std || !self.config.llvm_enabled {
             cargo
                 .env("RUSTC_SNAPSHOT", &self.initial_rustc)
                 .env("RUSTC_SNAPSHOT_LIBDIR", self.rustc_snapshot_libdir());
@@ -903,7 +903,7 @@ impl<'a> Builder<'a> {
         cargo.env("RUSTC_VERBOSE", format!("{}", self.verbosity));
 
         // in std, we want to avoid denying warnings for stage 0 as that makes cfg's painful.
-        if self.config.deny_warnings && !(mode == Mode::Libstd && stage == 0) {
+        if self.config.deny_warnings && !(mode == Mode::Std && stage == 0) {
             cargo.env("RUSTC_DENY_WARNINGS", "1");
         }
 
@@ -963,7 +963,7 @@ impl<'a> Builder<'a> {
         }
 
         if cmd == "build"
-            && mode == Mode::Libstd
+            && mode == Mode::Std
             && self.config.extended
             && compiler.is_final_stage(self)
         {
@@ -1012,7 +1012,7 @@ impl<'a> Builder<'a> {
         // be resolved because MinGW has the import library. The downside is we
         // don't get newer functions from Windows, but we don't use any of them
         // anyway.
-        if mode != Mode::Tool {
+        if !mode.is_tool() {
             cargo.env("WINAPI_NO_BUNDLED_LIBRARIES", "1");
         }
 
@@ -1751,7 +1751,7 @@ mod __test {
             &[test::Crate {
                 compiler: Compiler { host, stage: 0 },
                 target: host,
-                mode: Mode::Libstd,
+                mode: Mode::Std,
                 test_kind: test::TestKind::Test,
                 krate: INTERNER.intern_str("std"),
             },]
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index a516af58b1eab..b3ccb3cc3c926 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -40,10 +40,10 @@ impl Step for Std {
         let target = self.target;
         let compiler = builder.compiler(0, builder.config.build);
 
-        let out_dir = builder.stage_out(compiler, Mode::Libstd);
+        let out_dir = builder.stage_out(compiler, Mode::Std);
         builder.clear_if_dirty(&out_dir, &builder.rustc(compiler));
 
-        let mut cargo = builder.cargo(compiler, Mode::Libstd, target, "check");
+        let mut cargo = builder.cargo(compiler, Mode::Std, target, "check");
         std_cargo(builder, &compiler, target, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-std", compiler.stage));
@@ -87,11 +87,11 @@ impl Step for Rustc {
         let compiler = builder.compiler(0, builder.config.build);
         let target = self.target;
 
-        let stage_out = builder.stage_out(compiler, Mode::Librustc);
+        let stage_out = builder.stage_out(compiler, Mode::Rustc);
         builder.clear_if_dirty(&stage_out, &libstd_stamp(builder, compiler, target));
         builder.clear_if_dirty(&stage_out, &libtest_stamp(builder, compiler, target));
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "check");
+        let mut cargo = builder.cargo(compiler, Mode::Rustc, target, "check");
         rustc_cargo(builder, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-rustc", compiler.stage));
@@ -137,7 +137,7 @@ impl Step for CodegenBackend {
         let target = self.target;
         let backend = self.backend;
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "check");
+        let mut cargo = builder.cargo(compiler, Mode::Codegen, target, "check");
         let features = builder.rustc_features().to_string();
         cargo.arg("--manifest-path").arg(builder.src.join("src/librustc_codegen_llvm/Cargo.toml"));
         rustc_cargo_env(builder, &mut cargo);
@@ -175,10 +175,10 @@ impl Step for Test {
         let compiler = builder.compiler(0, builder.config.build);
         let target = self.target;
 
-        let out_dir = builder.stage_out(compiler, Mode::Libtest);
+        let out_dir = builder.stage_out(compiler, Mode::Test);
         builder.clear_if_dirty(&out_dir, &libstd_stamp(builder, compiler, target));
 
-        let mut cargo = builder.cargo(compiler, Mode::Libtest, target, "check");
+        let mut cargo = builder.cargo(compiler, Mode::Test, target, "check");
         test_cargo(builder, &compiler, target, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-test", compiler.stage));
@@ -219,6 +219,7 @@ impl Step for Rustdoc {
 
         let mut cargo = prepare_tool_cargo(builder,
                                            compiler,
+                                           Mode::ToolRustc,
                                            target,
                                            "check",
                                            "src/tools/rustdoc");
@@ -236,7 +237,7 @@ impl Step for Rustdoc {
         builder.ensure(tool::CleanTools {
             compiler,
             target,
-            mode: Mode::Tool,
+            cause: Mode::Rustc,
         });
     }
 }
@@ -244,19 +245,19 @@ impl Step for Rustdoc {
 /// Cargo's output path for the standard library in a given stage, compiled
 /// by a particular compiler for the specified target.
 pub fn libstd_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Libstd, target).join(".libstd-check.stamp")
+    builder.cargo_out(compiler, Mode::Std, target).join(".libstd-check.stamp")
 }
 
 /// Cargo's output path for libtest in a given stage, compiled by a particular
 /// compiler for the specified target.
 pub fn libtest_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Libtest, target).join(".libtest-check.stamp")
+    builder.cargo_out(compiler, Mode::Test, target).join(".libtest-check.stamp")
 }
 
 /// Cargo's output path for librustc in a given stage, compiled by a particular
 /// compiler for the specified target.
 pub fn librustc_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Librustc, target).join(".librustc-check.stamp")
+    builder.cargo_out(compiler, Mode::Rustc, target).join(".librustc-check.stamp")
 }
 
 /// Cargo's output path for librustc_codegen_llvm in a given stage, compiled by a particular
@@ -265,12 +266,12 @@ fn codegen_backend_stamp(builder: &Builder,
                          compiler: Compiler,
                          target: Interned<String>,
                          backend: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Librustc, target)
+    builder.cargo_out(compiler, Mode::Codegen, target)
          .join(format!(".librustc_codegen_llvm-{}-check.stamp", backend))
 }
 
 /// Cargo's output path for rustdoc in a given stage, compiled by a particular
 /// compiler for the specified target.
 pub fn rustdoc_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Tool, target).join(".rustdoc-check.stamp")
+    builder.cargo_out(compiler, Mode::ToolRustc, target).join(".rustdoc-check.stamp")
 }
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 231ed9d40d2de..11d9154ba696c 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -98,9 +98,9 @@ impl Step for Std {
             copy_musl_third_party_objects(builder, target, &libdir);
         }
 
-        let out_dir = builder.cargo_out(compiler, Mode::Libstd, target);
+        let out_dir = builder.cargo_out(compiler, Mode::Std, target);
         builder.clear_if_dirty(&out_dir, &builder.rustc(compiler));
-        let mut cargo = builder.cargo(compiler, Mode::Libstd, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Std, target, "build");
         std_cargo(builder, &compiler, target, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-std", compiler.stage));
@@ -240,7 +240,7 @@ impl Step for StdLink {
         builder.ensure(tool::CleanTools {
             compiler: target_compiler,
             target,
-            mode: Mode::Libstd,
+            cause: Mode::Std,
         });
     }
 }
@@ -368,9 +368,9 @@ impl Step for Test {
             return;
         }
 
-        let out_dir = builder.cargo_out(compiler, Mode::Libtest, target);
+        let out_dir = builder.cargo_out(compiler, Mode::Test, target);
         builder.clear_if_dirty(&out_dir, &libstd_stamp(builder, compiler, target));
-        let mut cargo = builder.cargo(compiler, Mode::Libtest, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Test, target, "build");
         test_cargo(builder, &compiler, target, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-test", compiler.stage));
@@ -431,7 +431,7 @@ impl Step for TestLink {
         builder.ensure(tool::CleanTools {
             compiler: target_compiler,
             target,
-            mode: Mode::Libtest,
+            cause: Mode::Test,
         });
     }
 }
@@ -489,11 +489,11 @@ impl Step for Rustc {
             compiler: builder.compiler(self.compiler.stage, builder.config.build),
             target: builder.config.build,
         });
-        let cargo_out = builder.cargo_out(compiler, Mode::Librustc, target);
+        let cargo_out = builder.cargo_out(compiler, Mode::Rustc, target);
         builder.clear_if_dirty(&cargo_out, &libstd_stamp(builder, compiler, target));
         builder.clear_if_dirty(&cargo_out, &libtest_stamp(builder, compiler, target));
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Rustc, target, "build");
         rustc_cargo(builder, &mut cargo);
 
         let _folder = builder.fold_output(|| format!("stage{}-rustc", compiler.stage));
@@ -585,7 +585,7 @@ impl Step for RustcLink {
         builder.ensure(tool::CleanTools {
             compiler: target_compiler,
             target,
-            mode: Mode::Librustc,
+            cause: Mode::Rustc,
         });
     }
 }
@@ -634,7 +634,7 @@ impl Step for CodegenBackend {
             return;
         }
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Codegen, target, "build");
         let mut features = builder.rustc_features().to_string();
         cargo.arg("--manifest-path")
             .arg(builder.src.join("src/librustc_codegen_llvm/Cargo.toml"));
@@ -642,7 +642,7 @@ impl Step for CodegenBackend {
 
         features += &build_codegen_backend(&builder, &mut cargo, &compiler, target, backend);
 
-        let tmp_stamp = builder.cargo_out(compiler, Mode::Librustc, target)
+        let tmp_stamp = builder.cargo_out(compiler, Mode::Codegen, target)
             .join(".tmp.stamp");
 
         let _folder = builder.fold_output(|| format!("stage{}-rustc_codegen_llvm", compiler.stage));
@@ -793,19 +793,19 @@ fn copy_lld_to_sysroot(builder: &Builder,
 /// Cargo's output path for the standard library in a given stage, compiled
 /// by a particular compiler for the specified target.
 pub fn libstd_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Libstd, target).join(".libstd.stamp")
+    builder.cargo_out(compiler, Mode::Std, target).join(".libstd.stamp")
 }
 
 /// Cargo's output path for libtest in a given stage, compiled by a particular
 /// compiler for the specified target.
 pub fn libtest_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Libtest, target).join(".libtest.stamp")
+    builder.cargo_out(compiler, Mode::Test, target).join(".libtest.stamp")
 }
 
 /// Cargo's output path for librustc in a given stage, compiled by a particular
 /// compiler for the specified target.
 pub fn librustc_stamp(builder: &Builder, compiler: Compiler, target: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Librustc, target).join(".librustc.stamp")
+    builder.cargo_out(compiler, Mode::Rustc, target).join(".librustc.stamp")
 }
 
 /// Cargo's output path for librustc_codegen_llvm in a given stage, compiled by a particular
@@ -814,7 +814,7 @@ fn codegen_backend_stamp(builder: &Builder,
                          compiler: Compiler,
                          target: Interned<String>,
                          backend: Interned<String>) -> PathBuf {
-    builder.cargo_out(compiler, Mode::Librustc, target)
+    builder.cargo_out(compiler, Mode::Codegen, target)
         .join(format!(".librustc_codegen_llvm-{}.stamp", backend))
 }
 
@@ -971,7 +971,7 @@ impl Step for Assemble {
         }
 
         // Link the compiler binary itself into place
-        let out_dir = builder.cargo_out(build_compiler, Mode::Librustc, host);
+        let out_dir = builder.cargo_out(build_compiler, Mode::Rustc, host);
         let rustc = out_dir.join(exe("rustc_binary", &*host));
         let bindir = sysroot.join("bin");
         t!(fs::create_dir_all(&bindir));
diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index 82ba03ec7773c..7341137e20d72 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -722,7 +722,7 @@ impl Step for Analysis {
 
         let image = tmpdir(builder).join(format!("{}-{}-image", name, target));
 
-        let src = builder.stage_out(compiler, Mode::Libstd)
+        let src = builder.stage_out(compiler, Mode::Std)
             .join(target).join(builder.cargo_dir()).join("deps");
 
         let image_src = src.join("save-analysis");
@@ -953,7 +953,7 @@ impl Step for PlainSourceTarball {
             if !has_cargo_vendor {
                 let mut cmd = builder.cargo(
                     builder.compiler(0, builder.config.build),
-                    Mode::Tool,
+                    Mode::ToolRustc,
                     builder.config.build,
                     "install"
                 );
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index cb22993852159..19599b33ebe26 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -463,7 +463,7 @@ impl Step for Std {
         };
 
         builder.ensure(compile::Std { compiler, target });
-        let out_dir = builder.stage_out(compiler, Mode::Libstd)
+        let out_dir = builder.stage_out(compiler, Mode::Std)
                            .join(target).join("doc");
 
         // Here what we're doing is creating a *symlink* (directory junction on
@@ -483,7 +483,7 @@ impl Step for Std {
         builder.clear_if_dirty(&my_out, &rustdoc);
         t!(symlink_dir_force(&builder.config, &my_out, &out_dir));
 
-        let mut cargo = builder.cargo(compiler, Mode::Libstd, target, "doc");
+        let mut cargo = builder.cargo(compiler, Mode::Std, target, "doc");
         compile::std_cargo(builder, &compiler, target, &mut cargo);
 
         // Keep a whitelist so we do not build internal stdlib crates, these will be
@@ -546,7 +546,7 @@ impl Step for Test {
         builder.ensure(Std { stage, target });
 
         builder.ensure(compile::Test { compiler, target });
-        let out_dir = builder.stage_out(compiler, Mode::Libtest)
+        let out_dir = builder.stage_out(compiler, Mode::Test)
                            .join(target).join("doc");
 
         // See docs in std above for why we symlink
@@ -554,7 +554,7 @@ impl Step for Test {
         builder.clear_if_dirty(&my_out, &rustdoc);
         t!(symlink_dir_force(&builder.config, &my_out, &out_dir));
 
-        let mut cargo = builder.cargo(compiler, Mode::Libtest, target, "doc");
+        let mut cargo = builder.cargo(compiler, Mode::Test, target, "doc");
         compile::test_cargo(builder, &compiler, target, &mut cargo);
 
         cargo.arg("--no-deps").arg("-p").arg("test");
@@ -614,7 +614,7 @@ impl Step for WhitelistedRustc {
         builder.ensure(Std { stage, target });
 
         builder.ensure(compile::Rustc { compiler, target });
-        let out_dir = builder.stage_out(compiler, Mode::Librustc)
+        let out_dir = builder.stage_out(compiler, Mode::Rustc)
                            .join(target).join("doc");
 
         // See docs in std above for why we symlink
@@ -622,7 +622,7 @@ impl Step for WhitelistedRustc {
         builder.clear_if_dirty(&my_out, &rustdoc);
         t!(symlink_dir_force(&builder.config, &my_out, &out_dir));
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "doc");
+        let mut cargo = builder.cargo(compiler, Mode::Rustc, target, "doc");
         compile::rustc_cargo(builder, &mut cargo);
 
         // We don't want to build docs for internal compiler dependencies in this
@@ -698,12 +698,12 @@ impl Step for Rustc {
 
         // We do not symlink to the same shared folder that already contains std library
         // documentation from previous steps as we do not want to include that.
-        let out_dir = builder.stage_out(compiler, Mode::Librustc).join(target).join("doc");
+        let out_dir = builder.stage_out(compiler, Mode::Rustc).join(target).join("doc");
         builder.clear_if_dirty(&out, &rustdoc);
         t!(symlink_dir_force(&builder.config, &out, &out_dir));
 
         // Build cargo command.
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "doc");
+        let mut cargo = builder.cargo(compiler, Mode::Rustc, target, "doc");
         cargo.env("RUSTDOCFLAGS", "--document-private-items");
         compile::rustc_cargo(builder, &mut cargo);
 
@@ -799,13 +799,15 @@ impl Step for Rustdoc {
         builder.ensure(tool::Rustdoc { host: compiler.host });
 
         // Symlink compiler docs to the output directory of rustdoc documentation.
-        let out_dir = builder.stage_out(compiler, Mode::Tool).join(target).join("doc");
+        let out_dir = builder.stage_out(compiler, Mode::ToolRustc).join(target).join("doc");
         t!(fs::create_dir_all(&out_dir));
         builder.clear_if_dirty(&out, &rustdoc);
         t!(symlink_dir_force(&builder.config, &out, &out_dir));
 
         // Build cargo command.
-        let mut cargo = prepare_tool_cargo(builder, compiler, target, "doc", "src/tools/rustdoc");
+        let mut cargo = prepare_tool_cargo(
+            builder, compiler, Mode::ToolRustc, target, "doc", "src/tools/rustdoc");
+
         cargo.env("RUSTDOCFLAGS", "--document-private-items");
         builder.run(&mut cargo);
     }
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index f64161fb0272c..d16d7a520659b 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -307,16 +307,30 @@ impl Crate {
 #[derive(Debug, Hash, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub enum Mode {
     /// Build the standard library, placing output in the "stageN-std" directory.
-    Libstd,
+    Std,
 
     /// Build libtest, placing output in the "stageN-test" directory.
-    Libtest,
+    Test,
 
-    /// Build librustc and compiler libraries, placing output in the "stageN-rustc" directory.
-    Librustc,
+    /// Build librustc, and compiler libraries, placing output in the "stageN-rustc" directory.
+    Rustc,
 
-    /// Build some tool, placing output in the "stageN-tools" directory.
-    Tool,
+    /// Build codegen libraries, placing output in the "stageN-codegen" directory
+    Codegen,
+
+    /// Build some tools, placing output in the "stageN-tools" directory.
+    ToolStd,
+    ToolTest,
+    ToolRustc,
+}
+
+impl Mode {
+    pub fn is_tool(&self) -> bool {
+        match self {
+            Mode::ToolStd | Mode::ToolTest | Mode::ToolRustc => true,
+            _ => false
+        }
+    }
 }
 
 impl Build {
@@ -517,10 +531,11 @@ impl Build {
     /// The mode indicates what the root directory is for.
     fn stage_out(&self, compiler: Compiler, mode: Mode) -> PathBuf {
         let suffix = match mode {
-            Mode::Libstd => "-std",
-            Mode::Libtest => "-test",
-            Mode::Tool => "-tools",
-            Mode::Librustc => "-rustc",
+            Mode::Std => "-std",
+            Mode::Test => "-test",
+            Mode::Codegen => "-rustc",
+            Mode::Rustc => "-rustc",
+            Mode::ToolStd | Mode::ToolTest | Mode::ToolRustc => "-tools",
         };
         self.out.join(&*compiler.host)
                 .join(format!("stage{}{}", compiler.stage, suffix))
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index c94cb57603206..a0b6222421d71 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -222,7 +222,7 @@ impl Step for Cargo {
             compiler,
             target: self.host,
         });
-        let mut cargo = builder.cargo(compiler, Mode::Tool, self.host, "test");
+        let mut cargo = builder.cargo(compiler, Mode::ToolRustc, self.host, "test");
         cargo
             .arg("--manifest-path")
             .arg(builder.src.join("src/tools/cargo/Cargo.toml"));
@@ -281,7 +281,12 @@ impl Step for Rls {
             return;
         }
 
-        let mut cargo = tool::prepare_tool_cargo(builder, compiler, host, "test", "src/tools/rls");
+        let mut cargo = tool::prepare_tool_cargo(builder,
+                                                 compiler,
+                                                 Mode::ToolRustc,
+                                                 host,
+                                                 "test",
+                                                 "src/tools/rls");
 
         // Don't build tests dynamically, just a pain to work with
         cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");
@@ -331,8 +336,12 @@ impl Step for Rustfmt {
             return;
         }
 
-        let mut cargo =
-            tool::prepare_tool_cargo(builder, compiler, host, "test", "src/tools/rustfmt");
+        let mut cargo = tool::prepare_tool_cargo(builder,
+                                                 compiler,
+                                                 Mode::ToolRustc,
+                                                 host,
+                                                 "test",
+                                                 "src/tools/rustfmt");
 
         // Don't build tests dynamically, just a pain to work with
         cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");
@@ -383,7 +392,7 @@ impl Step for Miri {
             extra_features: Vec::new(),
         });
         if let Some(miri) = miri {
-            let mut cargo = builder.cargo(compiler, Mode::Tool, host, "test");
+            let mut cargo = builder.cargo(compiler, Mode::ToolRustc, host, "test");
             cargo
                 .arg("--manifest-path")
                 .arg(builder.src.join("src/tools/miri/Cargo.toml"));
@@ -441,7 +450,7 @@ impl Step for Clippy {
             extra_features: Vec::new(),
         });
         if let Some(clippy) = clippy {
-            let mut cargo = builder.cargo(compiler, Mode::Tool, host, "test");
+            let mut cargo = builder.cargo(compiler, Mode::ToolRustc, host, "test");
             cargo
                 .arg("--manifest-path")
                 .arg(builder.src.join("src/tools/clippy/Cargo.toml"));
@@ -453,7 +462,7 @@ impl Step for Clippy {
             cargo.env("RUSTC_TEST_SUITE", builder.rustc(compiler));
             cargo.env("RUSTC_LIB_PATH", builder.rustc_libdir(compiler));
             let host_libs = builder
-                .stage_out(compiler, Mode::Tool)
+                .stage_out(compiler, Mode::ToolRustc)
                 .join(builder.cargo_dir());
             cargo.env("HOST_LIBS", host_libs);
             // clippy tests need to find the driver
@@ -1434,7 +1443,7 @@ impl Step for CrateLibrustc {
         builder.ensure(Crate {
             compiler: self.compiler,
             target: self.target,
-            mode: Mode::Librustc,
+            mode: Mode::Rustc,
             test_kind: self.test_kind,
             krate: self.krate,
         });
@@ -1485,7 +1494,7 @@ impl Step for CrateNotDefault {
         builder.ensure(Crate {
             compiler: self.compiler,
             target: self.target,
-            mode: Mode::Libstd,
+            mode: Mode::Std,
             test_kind: self.test_kind,
             krate: INTERNER.intern_str(self.krate),
         });
@@ -1538,12 +1547,12 @@ impl Step for Crate {
 
         for krate in builder.in_tree_crates("std") {
             if run.path.ends_with(&krate.local_path(&builder)) {
-                make(Mode::Libstd, krate);
+                make(Mode::Std, krate);
             }
         }
         for krate in builder.in_tree_crates("test") {
             if run.path.ends_with(&krate.local_path(&builder)) {
-                make(Mode::Libtest, krate);
+                make(Mode::Test, krate);
             }
         }
     }
@@ -1578,13 +1587,13 @@ impl Step for Crate {
 
         let mut cargo = builder.cargo(compiler, mode, target, test_kind.subcommand());
         match mode {
-            Mode::Libstd => {
+            Mode::Std => {
                 compile::std_cargo(builder, &compiler, target, &mut cargo);
             }
-            Mode::Libtest => {
+            Mode::Test => {
                 compile::test_cargo(builder, &compiler, target, &mut cargo);
             }
-            Mode::Librustc => {
+            Mode::Rustc => {
                 builder.ensure(compile::Rustc { compiler, target });
                 compile::rustc_cargo(builder, &mut cargo);
             }
@@ -1718,13 +1727,12 @@ impl Step for CrateRustdoc {
         let compiler = builder.compiler(builder.top_stage, self.host);
         let target = compiler.host;
 
-        let mut cargo = tool::prepare_tool_cargo(
-            builder,
-            compiler,
-            target,
-            test_kind.subcommand(),
-            "src/tools/rustdoc",
-        );
+        let mut cargo = tool::prepare_tool_cargo(builder,
+                                                 compiler,
+                                                 Mode::ToolRustc,
+                                                 target,
+                                                 test_kind.subcommand(),
+                                                 "src/tools/rustdoc");
         if test_kind.subcommand() == "test" && !builder.fail_fast {
             cargo.arg("--no-fail-fast");
         }
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index 29f37b36e2a8c..d4a2e96cc0d3f 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -28,7 +28,7 @@ use toolstate::ToolState;
 pub struct CleanTools {
     pub compiler: Compiler,
     pub target: Interned<String>,
-    pub mode: Mode,
+    pub cause: Mode,
 }
 
 impl Step for CleanTools {
@@ -41,23 +41,23 @@ impl Step for CleanTools {
     fn run(self, builder: &Builder) {
         let compiler = self.compiler;
         let target = self.target;
-        let mode = self.mode;
+        let cause = self.cause;
 
         // This is for the original compiler, but if we're forced to use stage 1, then
         // std/test/rustc stamps won't exist in stage 2, so we need to get those from stage 1, since
         // we copy the libs forward.
-        let tools_dir = builder.stage_out(compiler, Mode::Tool);
+        let tools_dir = builder.stage_out(compiler, Mode::ToolRustc);
         let compiler = if builder.force_use_stage1(compiler, target) {
             builder.compiler(1, compiler.host)
         } else {
             compiler
         };
 
-        for &cur_mode in &[Mode::Libstd, Mode::Libtest, Mode::Librustc] {
+        for &cur_mode in &[Mode::Std, Mode::Test, Mode::Rustc] {
             let stamp = match cur_mode {
-                Mode::Libstd => libstd_stamp(builder, compiler, target),
-                Mode::Libtest => libtest_stamp(builder, compiler, target),
-                Mode::Librustc => librustc_stamp(builder, compiler, target),
+                Mode::Std => libstd_stamp(builder, compiler, target),
+                Mode::Test => libtest_stamp(builder, compiler, target),
+                Mode::Rustc => librustc_stamp(builder, compiler, target),
                 _ => panic!(),
             };
 
@@ -67,7 +67,7 @@ impl Step for CleanTools {
 
             // If we are a rustc tool, and std changed, we also need to clear ourselves out -- our
             // dependencies depend on std. Therefore, we iterate up until our own mode.
-            if mode == cur_mode {
+            if cause == cur_mode {
                 break;
             }
         }
@@ -104,13 +104,13 @@ impl Step for ToolBuild {
         let is_ext_tool = self.is_ext_tool;
 
         match self.mode {
-            Mode::Libstd => builder.ensure(compile::Std { compiler, target }),
-            Mode::Libtest => builder.ensure(compile::Test { compiler, target }),
-            Mode::Librustc => builder.ensure(compile::Rustc { compiler, target }),
-            Mode::Tool => panic!("unexpected Mode::Tool for tool build")
+            Mode::ToolStd => builder.ensure(compile::Std { compiler, target }),
+            Mode::ToolTest => builder.ensure(compile::Test { compiler, target }),
+            Mode::ToolRustc => builder.ensure(compile::Rustc { compiler, target }),
+            _ => panic!("unexpected Mode for tool build")
         }
 
-        let mut cargo = prepare_tool_cargo(builder, compiler, target, "build", path);
+        let mut cargo = prepare_tool_cargo(builder, compiler, self.mode, target, "build", path);
         cargo.arg("--features").arg(self.extra_features.join(" "));
 
         let _folder = builder.fold_output(|| format!("stage{}-{}", compiler.stage, tool));
@@ -202,7 +202,7 @@ impl Step for ToolBuild {
                 return None;
             }
         } else {
-            let cargo_out = builder.cargo_out(compiler, Mode::Tool, target)
+            let cargo_out = builder.cargo_out(compiler, self.mode, target)
                 .join(exe(tool, &compiler.host));
             let bin = builder.tools_dir(compiler).join(exe(tool, &compiler.host));
             builder.copy(&cargo_out, &bin);
@@ -214,11 +214,12 @@ impl Step for ToolBuild {
 pub fn prepare_tool_cargo(
     builder: &Builder,
     compiler: Compiler,
+    mode: Mode,
     target: Interned<String>,
     command: &'static str,
     path: &'static str,
 ) -> Command {
-    let mut cargo = builder.cargo(compiler, Mode::Tool, target, command);
+    let mut cargo = builder.cargo(compiler, mode, target, command);
     let dir = builder.src.join(path);
     cargo.arg("--manifest-path").arg(dir.join("Cargo.toml"));
 
@@ -261,6 +262,15 @@ macro_rules! tool {
             )+
         }
 
+        impl Tool {
+            pub fn get_mode(&self) -> Mode {
+                let mode = match self {
+                    $(Tool::$name => $mode,)+
+                };
+                mode
+            }
+        }
+
         impl<'a> Builder<'a> {
             pub fn tool_exe(&self, tool: Tool) -> PathBuf {
                 let stage = self.tool_default_stage(tool);
@@ -324,17 +334,17 @@ macro_rules! tool {
 }
 
 tool!(
-    Rustbook, "src/tools/rustbook", "rustbook", Mode::Librustc;
-    ErrorIndex, "src/tools/error_index_generator", "error_index_generator", Mode::Librustc;
-    UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen", Mode::Libstd;
-    Tidy, "src/tools/tidy", "tidy", Mode::Libstd;
-    Linkchecker, "src/tools/linkchecker", "linkchecker", Mode::Libstd;
-    CargoTest, "src/tools/cargotest", "cargotest", Mode::Libstd;
-    Compiletest, "src/tools/compiletest", "compiletest", Mode::Libtest;
-    BuildManifest, "src/tools/build-manifest", "build-manifest", Mode::Libstd;
-    RemoteTestClient, "src/tools/remote-test-client", "remote-test-client", Mode::Libstd;
-    RustInstaller, "src/tools/rust-installer", "fabricate", Mode::Libstd;
-    RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes", Mode::Libstd;
+    Rustbook, "src/tools/rustbook", "rustbook", Mode::ToolRustc;
+    ErrorIndex, "src/tools/error_index_generator", "error_index_generator", Mode::ToolRustc;
+    UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen", Mode::ToolStd;
+    Tidy, "src/tools/tidy", "tidy", Mode::ToolStd;
+    Linkchecker, "src/tools/linkchecker", "linkchecker", Mode::ToolStd;
+    CargoTest, "src/tools/cargotest", "cargotest", Mode::ToolStd;
+    Compiletest, "src/tools/compiletest", "compiletest", Mode::ToolTest;
+    BuildManifest, "src/tools/build-manifest", "build-manifest", Mode::ToolStd;
+    RemoteTestClient, "src/tools/remote-test-client", "remote-test-client", Mode::ToolStd;
+    RustInstaller, "src/tools/rust-installer", "fabricate", Mode::ToolStd;
+    RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes", Mode::ToolStd;
 );
 
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
@@ -362,7 +372,7 @@ impl Step for RemoteTestServer {
             compiler: self.compiler,
             target: self.target,
             tool: "remote-test-server",
-            mode: Mode::Libstd,
+            mode: Mode::ToolStd,
             path: "src/tools/remote-test-server",
             is_ext_tool: false,
             extra_features: Vec::new(),
@@ -414,6 +424,7 @@ impl Step for Rustdoc {
 
         let mut cargo = prepare_tool_cargo(builder,
                                            build_compiler,
+                                           Mode::ToolRustc,
                                            target,
                                            "build",
                                            "src/tools/rustdoc");
@@ -430,7 +441,7 @@ impl Step for Rustdoc {
         // 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"
         // rustdoc a different name.
-        let tool_rustdoc = builder.cargo_out(build_compiler, Mode::Tool, target)
+        let tool_rustdoc = builder.cargo_out(build_compiler, Mode::ToolRustc, target)
             .join(exe("rustdoc_tool_binary", &target_compiler.host));
 
         // don't create a stage0-sysroot/bin directory.
@@ -485,7 +496,7 @@ impl Step for Cargo {
             compiler: self.compiler,
             target: self.target,
             tool: "cargo",
-            mode: Mode::Librustc,
+            mode: Mode::ToolRustc,
             path: "src/tools/cargo",
             is_ext_tool: false,
             extra_features: Vec::new(),
@@ -533,7 +544,7 @@ macro_rules! tool_extended {
                     compiler: $sel.compiler,
                     target: $sel.target,
                     tool: $tool_name,
-                    mode: Mode::Librustc,
+                    mode: Mode::ToolRustc,
                     path: $path,
                     extra_features: $sel.extra_features,
                     is_ext_tool: true,
@@ -575,7 +586,7 @@ impl<'a> Builder<'a> {
     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);
-        self.prepare_tool_cmd(compiler, &mut cmd);
+        self.prepare_tool_cmd(compiler, tool.get_mode(), &mut cmd);
         cmd
     }
 
@@ -583,11 +594,11 @@ impl<'a> Builder<'a> {
     ///
     /// Notably this munges the dynamic library lookup path to point to the
     /// right location to run `compiler`.
-    fn prepare_tool_cmd(&self, compiler: Compiler, cmd: &mut Command) {
+    fn prepare_tool_cmd(&self, compiler: Compiler, mode: Mode, cmd: &mut Command) {
         let host = &compiler.host;
         let mut lib_paths: Vec<PathBuf> = vec![
             PathBuf::from(&self.sysroot_libdir(compiler, compiler.host)),
-            self.cargo_out(compiler, Mode::Tool, *host).join("deps"),
+            self.cargo_out(compiler, mode, *host).join("deps"),
         ];
 
         // On MSVC a tool may invoke a C compiler (e.g. compiletest in run-make