Merge rayon-rs#1027

1027: Use const-TLS for the `WorkerThread` pointer (MSRV 1.59) r=cuviper a=cuviper

This enables more efficient code -- stabilized in rust-lang/rust#91355.


Co-authored-by: Josh Stone <cuviper@gmail.com>

Author: bors[bot]

.github/workflows/ci.yaml

@@ -8,11 +8,11 @@ on:
 jobs:
 
   check:
-    name: Check (1.56.0)
+    name: Check (1.59.0)
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: dtolnay/rust-toolchain@1.56.0
+      - uses: dtolnay/rust-toolchain@1.59.0
       - run: cp ci/compat-Cargo.lock ./Cargo.lock
       - run: cargo check --verbose --locked
 

.github/workflows/pr.yaml

@@ -8,11 +8,11 @@ env:
 jobs:
 
   check:
-    name: Check (1.56.0)
+    name: Check (1.59.0)
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: dtolnay/rust-toolchain@1.56.0
+      - uses: dtolnay/rust-toolchain@1.59.0
       - run: cp ci/compat-Cargo.lock ./Cargo.lock
       - run: cargo check --verbose --locked
 

Cargo.toml

@@ -4,7 +4,7 @@ version = "1.6.1"
 authors = ["Niko Matsakis <niko@alum.mit.edu>",
            "Josh Stone <cuviper@gmail.com>"]
 description = "Simple work-stealing parallelism for Rust"
-rust-version = "1.56"
+rust-version = "1.59"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rayon-rs/rayon"

README.md

@@ -2,7 +2,7 @@
 
 [![Rayon crate](https://img.shields.io/crates/v/rayon.svg)](https://crates.io/crates/rayon)
 [![Rayon documentation](https://docs.rs/rayon/badge.svg)](https://docs.rs/rayon)
-![minimum rustc 1.56](https://img.shields.io/badge/rustc-1.56+-red.svg)
+![minimum rustc 1.59](https://img.shields.io/badge/rustc-1.59+-red.svg)
 [![build status](https://github.com/rayon-rs/rayon/workflows/master/badge.svg)](https://github.com/rayon-rs/rayon/actions)
 [![Join the chat at https://gitter.im/rayon-rs/Lobby](https://badges.gitter.im/rayon-rs/Lobby.svg)](https://gitter.im/rayon-rs/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
@@ -84,7 +84,7 @@ just add:
 use rayon::prelude::*;
 ```
 
-Rayon currently requires `rustc 1.56.0` or greater.
+Rayon currently requires `rustc 1.59.0` or greater.
 
 ### Usage with WebAssembly
 

RELEASES.md

@@ -1,3 +1,7 @@
+# Unreleased
+
+- The minimum supported `rustc` is now 1.59.
+
 # Release rayon-core 1.10.2 (2023-01-22)
 
 - Fixed miri-reported UB for SharedReadOnly tags protected by a call.

bors.toml

@@ -1,5 +1,5 @@
 status = [
-  "Check (1.56.0)",
+  "Check (1.59.0)",
   "Test (ubuntu-latest, stable)",
   "Test (ubuntu-latest, stable-i686)",
   "Test (ubuntu-latest, beta)",

rayon-core/Cargo.toml

@@ -7,7 +7,7 @@ description = "Core APIs for Rayon"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rayon-rs/rayon"
 documentation = "https://docs.rs/rayon/"
-rust-version = "1.56"
+rust-version = "1.59"
 edition = "2021"
 links = "rayon-core"
 build = "build.rs"

rayon-core/README.md

@@ -8,4 +8,4 @@ Please see [Rayon Docs] for details about using Rayon.
 
 [Rayon Docs]: https://docs.rs/rayon/
 
-Rayon-core currently requires `rustc 1.56.0` or greater.
+Rayon-core currently requires `rustc 1.59.0` or greater.

rayon-core/src/registry.rs

@@ -686,7 +686,7 @@ pub(super) struct WorkerThread {
 // worker is fully unwound. Using an unsafe pointer avoids the need
 // for a RefCell<T> etc.
 thread_local! {
-    static WORKER_THREAD_STATE: Cell<*const WorkerThread> = Cell::new(ptr::null());
+    static WORKER_THREAD_STATE: Cell<*const WorkerThread> = const { Cell::new(ptr::null()) };
 }
 
 impl From<ThreadBuilder> for WorkerThread {

rayon-demo/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-rust-version = "1.56"
+rust-version = "1.59"
 edition = "2021"
 name = "rayon-demo"
 version = "0.0.0"