mv compiler to compiler/

compiler/rustc_data_structures/src/jobserver.rs

@@ -0,0 +1,42 @@
+pub use jobserver_crate::Client;
+use lazy_static::lazy_static;
+
+lazy_static! {
+    // We can only call `from_env` once per process
+
+    // Note that this is unsafe because it may misinterpret file descriptors
+    // on Unix as jobserver file descriptors. We hopefully execute this near
+    // the beginning of the process though to ensure we don't get false
+    // positives, or in other words we try to execute this before we open
+    // any file descriptors ourselves.
+    //
+    // Pick a "reasonable maximum" if we don't otherwise have
+    // a jobserver in our environment, capping out at 32 so we
+    // don't take everything down by hogging the process run queue.
+    // The fixed number is used to have deterministic compilation
+    // across machines.
+    //
+    // Also note that we stick this in a global because there could be
+    // multiple rustc instances in this process, and the jobserver is
+    // per-process.
+    static ref GLOBAL_CLIENT: Client = unsafe {
+        Client::from_env().unwrap_or_else(|| {
+            let client = Client::new(32).expect("failed to create jobserver");
+            // Acquire a token for the main thread which we can release later
+            client.acquire_raw().ok();
+            client
+        })
+    };
+}
+
+pub fn client() -> Client {
+    GLOBAL_CLIENT.clone()
+}
+
+pub fn acquire_thread() {
+    GLOBAL_CLIENT.acquire_raw().ok();
+}
+
+pub fn release_thread() {
+    GLOBAL_CLIENT.release_raw().ok();
+}