diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 20c89f99b2b0c..dcc4134b2f306 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -310,7 +310,7 @@ impl<'a> Builder<'a> {
                 tool::Compiletest, tool::RemoteTestServer, tool::RemoteTestClient,
                 tool::RustInstaller, tool::Cargo, tool::Rls, tool::Rustdoc, tool::Clippy,
                 native::Llvm, tool::Rustfmt, tool::Miri, native::Lld),
-            Kind::Check => describe!(check::Std, check::Test, check::Rustc),
+            Kind::Check => describe!(check::Std, check::Test, check::Rustc, check::CodegenBackend),
             Kind::Test => describe!(test::Tidy, test::Bootstrap, test::Ui, test::RunPass,
                 test::CompileFail, test::ParseFail, test::RunFail, test::RunPassValgrind,
                 test::MirOpt, test::Codegen, test::CodegenUnits, test::Incremental, test::Debuginfo,
@@ -834,7 +834,7 @@ impl<'a> Builder<'a> {
         cargo
     }
 
-    /// Ensure that a given step is built, returning it's output. This will
+    /// Ensure that a given step is built, returning its output. This will
     /// cache the step, so it is safe (and good!) to call this as often as
     /// needed to ensure that all dependencies are built.
     pub fn ensure<S: Step>(&'a self, step: S) -> S::Output {
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index adebd424d7eb6..b155cb826b644 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -10,10 +10,12 @@
 
 //! Implementation of compiling the compiler and standard library, in "check" mode.
 
-use compile::{run_cargo, std_cargo, test_cargo, rustc_cargo, add_to_sysroot};
+use compile::{run_cargo, std_cargo, test_cargo, rustc_cargo, rustc_cargo_env, add_to_sysroot};
+use compile::compiler_file;
 use builder::{RunConfig, Builder, ShouldRun, Step};
 use {Compiler, Mode};
-use cache::Interned;
+use native;
+use cache::{INTERNER, Interned};
 use std::path::PathBuf;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
@@ -104,6 +106,97 @@ impl Step for Rustc {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct CodegenBackend {
+    pub target: Interned<String>,
+    pub backend: Interned<String>,
+}
+
+impl Step for CodegenBackend {
+    type Output = ();
+    const ONLY_HOSTS: bool = true;
+    const DEFAULT: bool = true;
+
+    fn should_run(run: ShouldRun) -> ShouldRun {
+        run.all_krates("rustc_trans")
+    }
+
+    fn make_run(run: RunConfig) {
+        let backend = run.builder.config.rust_codegen_backends.get(0);
+        let backend = backend.cloned().unwrap_or_else(|| {
+            INTERNER.intern_str("llvm")
+        });
+        run.builder.ensure(CodegenBackend {
+            target: run.target,
+            backend,
+        });
+    }
+
+    fn run(self, builder: &Builder) {
+        let build = builder.build;
+        let compiler = builder.compiler(0, build.build);
+        let target = self.target;
+
+        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "check");
+        let mut features = build.rustc_features().to_string();
+        cargo.arg("--manifest-path").arg(build.src.join("src/librustc_trans/Cargo.toml"));
+        rustc_cargo_env(build, &mut cargo);
+
+        match &*self.backend {
+            "llvm" | "emscripten" => {
+                // Build LLVM for our target. This will implicitly build the
+                // host LLVM if necessary.
+                let llvm_config = builder.ensure(native::Llvm {
+                    target,
+                    emscripten: self.backend == "emscripten",
+                });
+
+                if self.backend == "emscripten" {
+                    features.push_str(" emscripten");
+                }
+
+                // Pass down configuration from the LLVM build into the build of
+                // librustc_llvm and librustc_trans.
+                if build.is_rust_llvm(target) {
+                    cargo.env("LLVM_RUSTLLVM", "1");
+                }
+                cargo.env("LLVM_CONFIG", &llvm_config);
+                if self.backend != "emscripten" {
+                    let target_config = build.config.target_config.get(&target);
+                    if let Some(s) = target_config.and_then(|c| c.llvm_config.as_ref()) {
+                        cargo.env("CFG_LLVM_ROOT", s);
+                    }
+                }
+                // Building with a static libstdc++ is only supported on linux right now,
+                // not for MSVC or macOS
+                if build.config.llvm_static_stdcpp &&
+                   !target.contains("freebsd") &&
+                   !target.contains("windows") &&
+                   !target.contains("apple") {
+                    let file = compiler_file(build,
+                                             build.cxx(target).unwrap(),
+                                             target,
+                                             "libstdc++.a");
+                    cargo.env("LLVM_STATIC_STDCPP", file);
+                }
+                if build.config.llvm_link_shared {
+                    cargo.env("LLVM_LINK_SHARED", "1");
+                }
+            }
+            _ => panic!("unknown backend: {}", self.backend),
+        }
+
+        let tmp_stamp = build.cargo_out(compiler, Mode::Librustc, target)
+            .join(".tmp.stamp");
+
+        let _folder = build.fold_output(|| format!("stage{}-rustc_trans", compiler.stage));
+        run_cargo(build,
+                  cargo.arg("--features").arg(features),
+                  &tmp_stamp,
+                  true);
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct Test {
     pub target: Interned<String>,
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 07bce77af8d24..12fd57d9531f2 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -519,7 +519,7 @@ pub fn rustc_cargo(builder: &Builder, cargo: &mut Command) {
     rustc_cargo_env(builder, cargo);
 }
 
-fn rustc_cargo_env(builder: &Builder, cargo: &mut Command) {
+pub fn rustc_cargo_env(builder: &Builder, cargo: &mut Command) {
     // Set some configuration variables picked up by build scripts and
     // the compiler alike
     cargo.env("CFG_RELEASE", builder.rust_release())
@@ -614,7 +614,7 @@ impl Step for CodegenBackend {
         run.builder.ensure(CodegenBackend {
             compiler: run.builder.compiler(run.builder.top_stage, run.host),
             target: run.target,
-            backend
+            backend,
         });
     }
 
@@ -803,7 +803,7 @@ fn codegen_backend_stamp(builder: &Builder,
         .join(format!(".librustc_trans-{}.stamp", backend))
 }
 
-fn compiler_file(builder: &Builder,
+pub fn compiler_file(builder: &Builder,
                  compiler: &Path,
                  target: Interned<String>,
                  file: &str) -> PathBuf {