Remove `GCX_PTR`.

We store an `ImplicitCtxt` pointer in a thread-local value (TLV). This allows
implicit access to a `GlobalCtxt` and some other things.

We also store a `GlobalCtxt` pointer in `GCX_PTR`. This is always the same
`GlobalCtxt` as the one within the `ImplicitCtxt` pointer in TLV. `GCX_PTR`
is only used in the parallel compiler's `handle_deadlock()` function.

This commit does the following.
- It removes `GCX_PTR`.
- It also adds `ImplicitCtxt::new()`, which constructs an `ImplicitCtxt` from a
  `GlobalCtxt`. `ImplicitCtxt::new()` + `tls::enter_context()` is now
  equivalent to the old `tls::enter_global()`.
- Makes `tls::get_tlv()` public for the parallel compiler, because it's
  now used in `handle_deadlock()`.

2 files changed, 15 insertions, 17 deletions

diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 125a020de37..3a562847d3e 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -752,7 +752,8 @@ impl<'tcx> QueryContext<'tcx> {
     where
         F: FnOnce(TyCtxt<'tcx>) -> R,
     {
-        ty::tls::enter_global(self.0, f)
+        let icx = ty::tls::ImplicitCtxt::new(self.0);
+        ty::tls::enter_context(&icx, |_| f(icx.tcx))
     }
 
     pub fn print_stats(&mut self) {
@@ -811,8 +812,9 @@ pub fn create_global_ctxt<'tcx>(
     });
 
     // Do some initialization of the DepGraph that can only be done with the tcx available.
-    ty::tls::enter_global(&gcx, |tcx| {
-        tcx.sess.time("dep_graph_tcx_init", || rustc_incremental::dep_graph_tcx_init(tcx));
+    let icx = ty::tls::ImplicitCtxt::new(&gcx);
+    ty::tls::enter_context(&icx, |_| {
+        icx.tcx.sess.time("dep_graph_tcx_init", || rustc_incremental::dep_graph_tcx_init(icx.tcx));
     });
 
     QueryContext(gcx)
diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
index 5b648608b6b..bbb2f9d8b25 100644
--- a/src/librustc_interface/util.rs
+++ b/src/librustc_interface/util.rs
@@ -10,10 +10,9 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 #[cfg(parallel_compiler)]
 use rustc_data_structures::jobserver;
 use rustc_data_structures::stable_hasher::StableHasher;
-use rustc_data_structures::sync::{Lock, Lrc};
+use rustc_data_structures::sync::Lrc;
 use rustc_errors::registry::Registry;
 use rustc_metadata::dynamic_lib::DynamicLibrary;
-use rustc_middle::ty;
 use rustc_resolve::{self, Resolver};
 use rustc_session as session;
 use rustc_session::config::{self, CrateType};
@@ -144,12 +143,10 @@ pub fn setup_callbacks_and_run_in_thread_pool_with_globals<F: FnOnce() -> R + Se
 
     let main_handler = move || {
         rustc_ast::with_session_globals(edition, || {
-            ty::tls::GCX_PTR.set(&Lock::new(0), || {
-                if let Some(stderr) = stderr {
-                    io::set_panic(Some(box Sink(stderr.clone())));
-                }
-                f()
-            })
+            if let Some(stderr) = stderr {
+                io::set_panic(Some(box Sink(stderr.clone())));
+            }
+            f()
         })
     };
 
@@ -163,6 +160,7 @@ pub fn setup_callbacks_and_run_in_thread_pool_with_globals<F: FnOnce() -> R + Se
     stderr: &Option<Arc<Mutex<Vec<u8>>>>,
     f: F,
 ) -> R {
+    use rustc_middle::ty;
     crate::callbacks::setup_callbacks();
 
     let mut config = rayon::ThreadPoolBuilder::new()
@@ -189,12 +187,10 @@ pub fn setup_callbacks_and_run_in_thread_pool_with_globals<F: FnOnce() -> R + Se
                 let main_handler = move |thread: rayon::ThreadBuilder| {
                     rustc_ast::SESSION_GLOBALS.set(ast_session_globals, || {
                         rustc_span::SESSION_GLOBALS.set(span_session_globals, || {
-                            ty::tls::GCX_PTR.set(&Lock::new(0), || {
-                                if let Some(stderr) = stderr {
-                                    io::set_panic(Some(box Sink(stderr.clone())));
-                                }
-                                thread.run()
-                            })
+                            if let Some(stderr) = stderr {
+                                io::set_panic(Some(box Sink(stderr.clone())));
+                            }
+                            thread.run()
                         })
                     })
                 };