diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 70e4a69a07d..ca86aeb8100 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -109,6 +109,12 @@ fn main() {
 
         cmd.arg("-Zexternal-macro-backtrace");
 
+        // Link crates to the proc macro crate for the target, but use a host proc macro crate
+        // to actually run the macros
+        if env::var_os("RUST_DUAL_PROC_MACROS").is_some() {
+            cmd.arg("-Zdual-proc-macros");
+        }
+
         // When we build Rust dylibs they're all intended for intermediate
         // usage, so make sure we pass the -Cprefer-dynamic flag instead of
         // linking all deps statically into the dylib.
@@ -258,13 +264,6 @@ fn main() {
             }
         }
 
-        // Force all crates compiled by this compiler to (a) be unstable and (b)
-        // allow the `rustc_private` feature to link to other unstable crates
-        // also in the sysroot.
-        if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() {
-            cmd.arg("-Z").arg("force-unstable-if-unmarked");
-        }
-
         if let Ok(map) = env::var("RUSTC_DEBUGINFO_MAP") {
             cmd.arg("--remap-path-prefix").arg(&map);
         }
@@ -284,6 +283,14 @@ fn main() {
         }
     }
 
+    // Force all crates compiled by this compiler to (a) be unstable and (b)
+    // allow the `rustc_private` feature to link to other unstable crates
+    // also in the sysroot. We also do this for host crates, since those
+    // may be proc macros, in which case we might ship them.
+    if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() && (stage != "0" || target.is_some()) {
+        cmd.arg("-Z").arg("force-unstable-if-unmarked");
+    }
+
     if env::var_os("RUSTC_PARALLEL_COMPILER").is_some() {
         cmd.arg("--cfg").arg("parallel_compiler");
     }
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 7e6c0a9f52a..eb1a2a59fa3 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -812,6 +812,17 @@ impl<'a> Builder<'a> {
             cargo.env("RUST_CHECK", "1");
         }
 
+        match mode {
+            Mode::Std | Mode::Test | Mode::ToolBootstrap | Mode::ToolStd | Mode::ToolTest=> {},
+            Mode::Rustc | Mode::Codegen | Mode::ToolRustc => {
+                // Build proc macros both for the host and the target
+                if target != compiler.host && cmd != "check" {
+                    cargo.arg("-Zdual-proc-macros");
+                    cargo.env("RUST_DUAL_PROC_MACROS", "1");
+                }
+            },
+        }
+
         cargo.arg("-j").arg(self.jobs().to_string());
         // Remove make-related flags to ensure Cargo can correctly set things up
         cargo.env_remove("MAKEFLAGS");
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 20370372082..a30b465698e 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -42,7 +42,8 @@ impl Step for Std {
                   true);
 
         let libdir = builder.sysroot_libdir(compiler, target);
-        add_to_sysroot(&builder, &libdir, &libstd_stamp(builder, compiler, target));
+        let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+        add_to_sysroot(&builder, &libdir, &hostdir, &libstd_stamp(builder, compiler, target));
     }
 }
 
@@ -88,7 +89,8 @@ impl Step for Rustc {
                   true);
 
         let libdir = builder.sysroot_libdir(compiler, target);
-        add_to_sysroot(&builder, &libdir, &librustc_stamp(builder, compiler, target));
+        let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+        add_to_sysroot(&builder, &libdir, &hostdir, &librustc_stamp(builder, compiler, target));
     }
 }
 
@@ -175,7 +177,8 @@ impl Step for Test {
                   true);
 
         let libdir = builder.sysroot_libdir(compiler, target);
-        add_to_sysroot(builder, &libdir, &libtest_stamp(builder, compiler, target));
+        let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+        add_to_sysroot(builder, &libdir, &hostdir, &libtest_stamp(builder, compiler, target));
     }
 }
 
@@ -222,7 +225,8 @@ impl Step for Rustdoc {
                   true);
 
         let libdir = builder.sysroot_libdir(compiler, target);
-        add_to_sysroot(&builder, &libdir, &rustdoc_stamp(builder, compiler, target));
+        let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+        add_to_sysroot(&builder, &libdir, &hostdir, &rustdoc_stamp(builder, compiler, target));
         builder.cargo(compiler, Mode::ToolRustc, target, "clean");
     }
 }
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 249a1831890..9498dbb5952 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -224,7 +224,8 @@ impl Step for StdLink {
                 target_compiler.host,
                 target));
         let libdir = builder.sysroot_libdir(target_compiler, target);
-        add_to_sysroot(builder, &libdir, &libstd_stamp(builder, compiler, target));
+        let hostdir = builder.sysroot_libdir(target_compiler, compiler.host);
+        add_to_sysroot(builder, &libdir, &hostdir, &libstd_stamp(builder, compiler, target));
 
         if builder.config.sanitizers && compiler.stage != 0 && target == "x86_64-apple-darwin" {
             // The sanitizers are only built in stage1 or above, so the dylibs will
@@ -431,8 +432,12 @@ impl Step for TestLink {
                 &compiler.host,
                 target_compiler.host,
                 target));
-        add_to_sysroot(builder, &builder.sysroot_libdir(target_compiler, target),
-                    &libtest_stamp(builder, compiler, target));
+        add_to_sysroot(
+            builder,
+            &builder.sysroot_libdir(target_compiler, target),
+            &builder.sysroot_libdir(target_compiler, compiler.host),
+            &libtest_stamp(builder, compiler, target)
+        );
 
         builder.cargo(target_compiler, Mode::ToolTest, target, "clean");
     }
@@ -496,8 +501,8 @@ impl Step for Rustc {
             return;
         }
 
-        // Ensure that build scripts have a std to link against.
-        builder.ensure(Std {
+        // Ensure that build scripts and proc macros have a std / libproc_macro to link against.
+        builder.ensure(Test {
             compiler: builder.compiler(self.compiler.stage, builder.config.build),
             target: builder.config.build,
         });
@@ -592,8 +597,12 @@ impl Step for RustcLink {
                  &compiler.host,
                  target_compiler.host,
                  target));
-        add_to_sysroot(builder, &builder.sysroot_libdir(target_compiler, target),
-                       &librustc_stamp(builder, compiler, target));
+        add_to_sysroot(
+            builder,
+            &builder.sysroot_libdir(target_compiler, target),
+            &builder.sysroot_libdir(target_compiler, compiler.host),
+            &librustc_stamp(builder, compiler, target)
+        );
         builder.cargo(target_compiler, Mode::ToolRustc, target, "clean");
     }
 }
@@ -1015,10 +1024,20 @@ impl Step for Assemble {
 ///
 /// For a particular stage this will link the file listed in `stamp` into the
 /// `sysroot_dst` provided.
-pub fn add_to_sysroot(builder: &Builder<'_>, sysroot_dst: &Path, stamp: &Path) {
+pub fn add_to_sysroot(
+    builder: &Builder<'_>,
+    sysroot_dst: &Path,
+    sysroot_host_dst: &Path,
+    stamp: &Path
+) {
     t!(fs::create_dir_all(&sysroot_dst));
-    for path in builder.read_stamp_file(stamp) {
-        builder.copy(&path, &sysroot_dst.join(path.file_name().unwrap()));
+    t!(fs::create_dir_all(&sysroot_host_dst));
+    for (path, host) in builder.read_stamp_file(stamp) {
+        if host {
+            builder.copy(&path, &sysroot_host_dst.join(path.file_name().unwrap()));
+        } else {
+            builder.copy(&path, &sysroot_dst.join(path.file_name().unwrap()));
+        }
     }
 }
 
@@ -1047,8 +1066,14 @@ pub fn run_cargo(builder: &Builder<'_>,
     let mut deps = Vec::new();
     let mut toplevel = Vec::new();
     let ok = stream_cargo(builder, cargo, &mut |msg| {
-        let filenames = match msg {
-            CargoMessage::CompilerArtifact { filenames, .. } => filenames,
+        let (filenames, crate_types) = match msg {
+            CargoMessage::CompilerArtifact {
+                filenames,
+                target: CargoTarget {
+                    crate_types,
+                },
+                ..
+            } => (filenames, crate_types),
             _ => return,
         };
         for filename in filenames {
@@ -1063,15 +1088,19 @@ pub fn run_cargo(builder: &Builder<'_>,
             let filename = Path::new(&*filename);
 
             // If this was an output file in the "host dir" we don't actually
-            // worry about it, it's not relevant for us.
+            // worry about it, it's not relevant for us
             if filename.starts_with(&host_root_dir) {
+                // Unless it's a proc macro used in the compiler
+                if crate_types.iter().any(|t| t == "proc-macro") {
+                    deps.push((filename.to_path_buf(), true));
+                }
                 continue;
             }
 
             // If this was output in the `deps` dir then this is a precise file
             // name (hash included) so we start tracking it.
             if filename.starts_with(&target_deps_dir) {
-                deps.push(filename.to_path_buf());
+                deps.push((filename.to_path_buf(), false));
                 continue;
             }
 
@@ -1124,10 +1153,10 @@ pub fn run_cargo(builder: &Builder<'_>,
             let candidate = format!("{}.lib", path_to_add);
             let candidate = PathBuf::from(candidate);
             if candidate.exists() {
-                deps.push(candidate);
+                deps.push((candidate, false));
             }
         }
-        deps.push(path_to_add.into());
+        deps.push((path_to_add.into(), false));
     }
 
     // Now we want to update the contents of the stamp file, if necessary. First
@@ -1140,12 +1169,13 @@ pub fn run_cargo(builder: &Builder<'_>,
     let mut new_contents = Vec::new();
     let mut max = None;
     let mut max_path = None;
-    for dep in deps.iter() {
+    for (dep, proc_macro) in deps.iter() {
         let mtime = mtime(dep);
         if Some(mtime) > max {
             max = Some(mtime);
             max_path = Some(dep.clone());
         }
+        new_contents.extend(if *proc_macro { b"h" } else { b"t" });
         new_contents.extend(dep.to_str().unwrap().as_bytes());
         new_contents.extend(b"\0");
     }
@@ -1157,7 +1187,7 @@ pub fn run_cargo(builder: &Builder<'_>,
     if contents_equal && max <= stamp_mtime {
         builder.verbose(&format!("not updating {:?}; contents equal and {:?} <= {:?}",
                 stamp, max, stamp_mtime));
-        return deps
+        return deps.into_iter().map(|(d, _)| d).collect()
     }
     if max > stamp_mtime {
         builder.verbose(&format!("updating {:?} as {:?} changed", stamp, max_path));
@@ -1165,7 +1195,7 @@ pub fn run_cargo(builder: &Builder<'_>,
         builder.verbose(&format!("updating {:?} as deps changed", stamp));
     }
     t!(fs::write(&stamp, &new_contents));
-    deps
+    deps.into_iter().map(|(d, _)| d).collect()
 }
 
 pub fn stream_cargo(
@@ -1211,6 +1241,11 @@ pub fn stream_cargo(
     status.success()
 }
 
+#[derive(Deserialize)]
+pub struct CargoTarget<'a> {
+    crate_types: Vec<Cow<'a, str>>,
+}
+
 #[derive(Deserialize)]
 #[serde(tag = "reason", rename_all = "kebab-case")]
 pub enum CargoMessage<'a> {
@@ -1218,6 +1253,7 @@ pub enum CargoMessage<'a> {
         package_id: Cow<'a, str>,
         features: Vec<Cow<'a, str>>,
         filenames: Vec<Cow<'a, str>>,
+        target: CargoTarget<'a>,
     },
     BuildScriptExecuted {
         package_id: Cow<'a, str>,
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 84e2c5aab54..9317a40545e 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -1129,7 +1129,7 @@ impl Build {
         ret
     }
 
-    fn read_stamp_file(&self, stamp: &Path) -> Vec<PathBuf> {
+    fn read_stamp_file(&self, stamp: &Path) -> Vec<(PathBuf, bool)> {
         if self.config.dry_run {
             return Vec::new();
         }
@@ -1142,8 +1142,9 @@ impl Build {
             if part.is_empty() {
                 continue
             }
-            let path = PathBuf::from(t!(str::from_utf8(part)));
-            paths.push(path);
+            let host = part[0] as char == 'h';
+            let path = PathBuf::from(t!(str::from_utf8(&part[1..])));
+            paths.push((path, host));
         }
         paths
     }
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 51412f79c3d..6e37bf33452 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -213,7 +213,7 @@ impl Step for Cargo {
         });
         let mut cargo = tool::prepare_tool_cargo(builder,
                                                  compiler,
-                                                 Mode::ToolRustc,
+                                                 Mode::ToolStd,
                                                  self.host,
                                                  "test",
                                                  "src/tools/cargo",
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index fc1a17d5466..b12ccc4f39d 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -91,7 +91,8 @@ impl Step for ToolBuild {
                 compile::CargoMessage::CompilerArtifact {
                     package_id,
                     features,
-                    filenames
+                    filenames,
+                    target: _,
                 } => {
                     (package_id, features, filenames)
                 }
@@ -513,7 +514,7 @@ impl Step for Cargo {
             compiler: self.compiler,
             target: self.target,
             tool: "cargo",
-            mode: Mode::ToolRustc,
+            mode: Mode::ToolStd,
             path: "src/tools/cargo",
             is_optional_tool: false,
             source_type: SourceType::Submodule,