From 2d854f9c340df887e30896f49270ae81feb3e227 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Wed, 2 Mar 2022 15:22:32 +0100
Subject: [PATCH] Remove num_cpus dependency from bootstrap, build-manifest and
 rustc_session

---
 Cargo.lock                            | 3 ---
 compiler/rustc_session/Cargo.toml     | 1 -
 compiler/rustc_session/src/options.rs | 2 +-
 src/bootstrap/Cargo.toml              | 1 -
 src/bootstrap/config.rs               | 2 +-
 src/bootstrap/flags.rs                | 2 +-
 src/bootstrap/lib.rs                  | 4 +++-
 src/tools/build-manifest/Cargo.toml   | 1 -
 src/tools/build-manifest/src/main.rs  | 2 +-
 9 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index f0c6e371c38be..716f4d7501467 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -221,7 +221,6 @@ dependencies = [
  "getopts",
  "ignore",
  "libc",
- "num_cpus",
  "once_cell",
  "opener",
  "pretty_assertions",
@@ -249,7 +248,6 @@ dependencies = [
  "anyhow",
  "flate2",
  "hex 0.4.2",
- "num_cpus",
  "rayon",
  "serde",
  "serde_json",
@@ -4241,7 +4239,6 @@ name = "rustc_session"
 version = "0.0.0"
 dependencies = [
  "getopts",
- "num_cpus",
  "rustc_ast",
  "rustc_data_structures",
  "rustc_errors",
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index 37cfc4a0dc3c2..6b1eaa4d399d9 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -15,6 +15,5 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_span = { path = "../rustc_span" }
 rustc_fs_util = { path = "../rustc_fs_util" }
-num_cpus = "1.0"
 rustc_ast = { path = "../rustc_ast" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index c2b13346cd6c9..43123d30ad5c6 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -551,7 +551,7 @@ mod parse {
     crate fn parse_threads(slot: &mut usize, v: Option<&str>) -> bool {
         match v.and_then(|s| s.parse().ok()) {
             Some(0) => {
-                *slot = ::num_cpus::get();
+                *slot = std::thread::available_parallelism().map_or(1, std::num::NonZeroUsize::get);
                 true
             }
             Some(i) => {
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 592a137e379de..02efc08cc791f 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -37,7 +37,6 @@ test = false
 build_helper = { path = "../build_helper" }
 cmake = "0.1.38"
 filetime = "0.2"
-num_cpus = "1.0"
 getopts = "0.2.19"
 cc = "1.0.69"
 libc = "0.2"
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index d6f77fe6cd6d0..ce76ccd57551d 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -1187,7 +1187,7 @@ fn set<T>(field: &mut T, val: Option<T>) {
 
 fn threads_from_config(v: u32) -> u32 {
     match v {
-        0 => num_cpus::get() as u32,
+        0 => std::thread::available_parallelism().map_or(1, std::num::NonZeroUsize::get) as u32,
         n => n,
     }
 }
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index 9180c5f03af68..74528f2752f5f 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -208,7 +208,7 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
         let j_msg = format!(
             "number of jobs to run in parallel; \
              defaults to {} (this host's logical CPU count)",
-            num_cpus::get()
+            std::thread::available_parallelism().map_or(1, std::num::NonZeroUsize::get)
         );
         opts.optopt("j", "jobs", &j_msg, "JOBS");
         opts.optflag("h", "help", "print this help message");
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 86339c8d7f88d..6a58de40181c2 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -917,7 +917,9 @@ impl Build {
     /// Returns the number of parallel jobs that have been configured for this
     /// build.
     fn jobs(&self) -> u32 {
-        self.config.jobs.unwrap_or_else(|| num_cpus::get() as u32)
+        self.config.jobs.unwrap_or_else(|| {
+            std::thread::available_parallelism().map_or(1, std::num::NonZeroUsize::get) as u32
+        })
     }
 
     fn debuginfo_map_to(&self, which: GitRepo) -> Option<String> {
diff --git a/src/tools/build-manifest/Cargo.toml b/src/tools/build-manifest/Cargo.toml
index c022d3aa0acd7..c437bde5ae69a 100644
--- a/src/tools/build-manifest/Cargo.toml
+++ b/src/tools/build-manifest/Cargo.toml
@@ -13,4 +13,3 @@ tar = "0.4.29"
 sha2 = "0.10.1"
 rayon = "1.5.1"
 hex = "0.4.2"
-num_cpus = "1.13.0"
diff --git a/src/tools/build-manifest/src/main.rs b/src/tools/build-manifest/src/main.rs
index 8a62146abfc4e..378efeb644375 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -208,7 +208,7 @@ fn main() {
     let num_threads = if let Some(num) = env::var_os("BUILD_MANIFEST_NUM_THREADS") {
         num.to_str().unwrap().parse().expect("invalid number for BUILD_MANIFEST_NUM_THREADS")
     } else {
-        num_cpus::get()
+        std::thread::available_parallelism().map_or(1, std::num::NonZeroUsize::get)
     };
     rayon::ThreadPoolBuilder::new()
         .num_threads(num_threads)