bootstrap for parallel compiler

Author: SparrowLii

src/bootstrap/config.rs

@@ -1133,7 +1133,7 @@ impl Config {
             set(&mut config.use_lld, rust.use_lld);
             set(&mut config.lld_enabled, rust.lld);
             set(&mut config.llvm_tools_enabled, rust.llvm_tools);
-            config.rustc_parallel = rust.parallel_compiler.unwrap_or(false);
+            config.rustc_parallel = rust.parallel_compiler.unwrap_or(true);
             config.rustc_default_linker = rust.default_linker;
             config.musl_root = rust.musl_root.map(PathBuf::from);
             config.save_toolstates = rust.save_toolstates.map(PathBuf::from);

src/librustdoc/clean/utils.rs

@@ -470,12 +470,6 @@ pub(crate) fn get_auto_trait_and_blanket_impls(
     cx: &mut DocContext<'_>,
     item_def_id: DefId,
 ) -> impl Iterator<Item = Item> {
-    // FIXME: To be removed once `parallel_compiler` bugs are fixed!
-    // More information in <https://github.com/rust-lang/rust/pull/106930>.
-    if cfg!(parallel_compiler) {
-        return vec![].into_iter().chain(vec![].into_iter());
-    }
-
     let auto_impls = cx
         .sess()
         .prof