Make GlobalCtxt implement Sync

src/bootstrap/bin/rustc.rs

@@ -262,6 +262,10 @@ fn main() {
         }
     }
 
+    if env::var_os("RUSTC_PARALLEL_QUERIES").is_some() {
+        cmd.arg("--cfg").arg("parallel_queries");
+    }
+
     let color = match env::var("RUSTC_COLOR") {
         Ok(s) => usize::from_str(&s).expect("RUSTC_COLOR should be an integer"),
         Err(_) => 0,

src/bootstrap/compile.rs

@@ -561,6 +561,9 @@ pub fn rustc_cargo(build: &Build,
     if let Some(ref s) = build.config.rustc_default_linker {
         cargo.env("CFG_DEFAULT_LINKER", s);
     }
+    if build.config.rustc_parallel_queries {
+        cargo.env("RUSTC_PARALLEL_QUERIES", "1");
+    }
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]

src/bootstrap/config.rs

@@ -87,6 +87,7 @@ pub struct Config {
     pub rust_debuginfo_lines: bool,
     pub rust_debuginfo_only_std: bool,
     pub rust_rpath: bool,
+    pub rustc_parallel_queries: bool,
     pub rustc_default_linker: Option<String>,
     pub rust_optimize_tests: bool,
     pub rust_debuginfo_tests: bool,
@@ -266,6 +267,7 @@ struct Rust {
     debuginfo: Option<bool>,
     debuginfo_lines: Option<bool>,
     debuginfo_only_std: Option<bool>,
+    experimental_parallel_queries: Option<bool>,
     debug_jemalloc: Option<bool>,
     use_jemalloc: Option<bool>,
     backtrace: Option<bool>,
@@ -474,6 +476,7 @@ impl Config {
             set(&mut config.rust_dist_src, rust.dist_src);
             set(&mut config.quiet_tests, rust.quiet_tests);
             set(&mut config.test_miri, rust.test_miri);
+            config.rustc_parallel_queries = rust.experimental_parallel_queries.unwrap_or(false);
             config.rustc_default_linker = rust.default_linker.clone();
             config.musl_root = rust.musl_root.clone().map(PathBuf::from);
             config.save_toolstates = rust.save_toolstates.clone().map(PathBuf::from);

src/libarena/Cargo.toml

@@ -7,3 +7,6 @@ version = "0.0.0"
 name = "arena"
 path = "lib.rs"
 crate-type = ["dylib"]
+
+[dependencies]
+rustc_data_structures = { path = "../librustc_data_structures" }