Auto merge of #84833 - Mark-Simulacrum:thread-local-consts, r=varkor

"const" initialized thread locals in rustc

This appears to give a slight speedup on many of our benchmarks.

5 files changed, 8 insertions, 6 deletions

diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 45ea07a3db6..597a4fd0f52 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -50,6 +50,7 @@
 #![feature(control_flow_enum)]
 #![feature(associated_type_defaults)]
 #![feature(iter_zip)]
+#![feature(thread_local_const_init)]
 #![recursion_limit = "512"]
 
 #[macro_use]
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index b414618f7d5..10f7cc87c7c 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1705,7 +1705,7 @@ pub mod tls {
     #[cfg(not(parallel_compiler))]
     thread_local! {
         /// A thread local variable that stores a pointer to the current `ImplicitCtxt`.
-        static TLV: Cell<usize> = Cell::new(0);
+        static TLV: Cell<usize> = const { Cell::new(0) };
     }
 
     /// Sets TLV to `value` during the call to `f`.
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 1989c91a879..174ec481ae9 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -55,10 +55,10 @@ macro_rules! define_scoped_cx {
 }
 
 thread_local! {
-    static FORCE_IMPL_FILENAME_LINE: Cell<bool> = Cell::new(false);
-    static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = Cell::new(false);
-    static NO_TRIMMED_PATH: Cell<bool> = Cell::new(false);
-    static NO_QUERIES: Cell<bool> = Cell::new(false);
+    static FORCE_IMPL_FILENAME_LINE: Cell<bool> = const { Cell::new(false) };
+    static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = const { Cell::new(false) };
+    static NO_TRIMMED_PATH: Cell<bool> = const { Cell::new(false) };
+    static NO_QUERIES: Cell<bool> = const { Cell::new(false) };
 }
 
 /// Avoids running any queries during any prints that occur
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index f75fe22767f..8b611626fca 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -1330,7 +1330,7 @@ fn update_disambiguator(expn_id: ExpnId) {
             // This cache is only used by `DummyHashStableContext`,
             // so we won't pollute the cache values of the normal `StableHashingContext`
             thread_local! {
-                static CACHE: ExpnIdCache = Default::default();
+                static CACHE: ExpnIdCache = const { ExpnIdCache::new(Vec::new()) };
             }
 
             &CACHE
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index d30236ec3ec..e0bc7544246 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -20,6 +20,7 @@
 #![feature(negative_impls)]
 #![feature(nll)]
 #![feature(min_specialization)]
+#![feature(thread_local_const_init)]
 
 #[macro_use]
 extern crate rustc_macros;