Auto merge of #100595 - matthiaskrgr:rollup-f1zur58, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #100031 (improve "try ignoring the field" diagnostic)
 - #100325 (Rustdoc-Json: Don't remove impls for items imported from private modules)
 - #100377 (Replace - with _ in fluent slugs to improve developer workflows)
 - #100458 (Adjust span of fn argument declaration)
 - #100514 (Delay span bug when failing to normalize negative coherence impl subject due to other malformed impls)
 - #100528 (Support 1st group of RISC-V Bitmanip backend target features)
 - #100559 (Parser simplifications)
 - #100568 (Fix STD build for ESP-IDF)
 - #100582 ([rustdoc] Fix handling of stripped enum variant in JSON output format)
 - #100586 (Reland changes replacing num_cpus with available_parallelism )

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

31 files changed, 232 insertions, 42 deletions

diff --git a/src/bootstrap/Cargo.lock b/src/bootstrap/Cargo.lock
index 664ffa1ddd2..84c06fdce70 100644
--- a/src/bootstrap/Cargo.lock
+++ b/src/bootstrap/Cargo.lock
@@ -53,7 +53,6 @@ dependencies = [
  "hex",
  "ignore",
  "libc",
- "num_cpus",
  "once_cell",
  "opener",
  "pretty_assertions",
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 84f6aaf99c1..2dad41bb18f 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -38,7 +38,6 @@ test = false
 cmake = "0.1.38"
 fd-lock = "3.0.6"
 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 c4983accc68..203db2d3876 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -1465,7 +1465,7 @@ 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 1edb513f0b6..789da748100 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -220,7 +220,7 @@ 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 a242243aaaf..dcfa92d1004 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -1008,7 +1008,9 @@ 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/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 5f3793ead42..1fedb0144d1 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -662,12 +662,10 @@ impl FromWithTcx<clean::Variant> for Variant {
             Tuple(fields) => Variant::Tuple(
                 fields
                     .into_iter()
-                    .map(|f| {
-                        if let clean::StructFieldItem(ty) = *f.kind {
-                            ty.into_tcx(tcx)
-                        } else {
-                            unreachable!()
-                        }
+                    .filter_map(|f| match *f.kind {
+                        clean::StructFieldItem(ty) => Some(ty.into_tcx(tcx)),
+                        clean::StrippedItem(_) => None,
+                        _ => unreachable!(),
                     })
                     .collect(),
             ),
diff --git a/src/librustdoc/passes/stripper.rs b/src/librustdoc/passes/stripper.rs
index 3f069e8393f..83ed3752a82 100644
--- a/src/librustdoc/passes/stripper.rs
+++ b/src/librustdoc/passes/stripper.rs
@@ -88,7 +88,17 @@ impl<'a> DocFolder for Stripper<'a> {
             }
 
             // handled in the `strip-priv-imports` pass
-            clean::ExternCrateItem { .. } | clean::ImportItem(..) => {}
+            clean::ExternCrateItem { .. } => {}
+            clean::ImportItem(ref imp) => {
+                // Because json doesn't inline imports from private modules, we need to mark
+                // the imported item as retained so it's impls won't be stripped.i
+                //
+                // FIXME: Is it necessary to check for json output here: See
+                // https://github.com/rust-lang/rust/pull/100325#discussion_r941495215
+                if let Some(did) = imp.source.did && self.is_json_output {
+                    self.retained.insert(did.into());
+                }
+            }
 
             clean::ImplItem(..) => {}
 
diff --git a/src/test/run-make/translation/broken.ftl b/src/test/run-make/translation/broken.ftl
index 1482dd2824a..4e358583528 100644
--- a/src/test/run-make/translation/broken.ftl
+++ b/src/test/run-make/translation/broken.ftl
@@ -1,3 +1,3 @@
 # `foo` isn't provided by this diagnostic so it is expected that the fallback message is used.
-parser-struct-literal-body-without-path = this is a {$foo} message
+parser_struct_literal_body_without_path = this is a {$foo} message
     .suggestion = this is a test suggestion
diff --git a/src/test/run-make/translation/missing.ftl b/src/test/run-make/translation/missing.ftl
index 43076b1d6ae..77bbda3575b 100644
--- a/src/test/run-make/translation/missing.ftl
+++ b/src/test/run-make/translation/missing.ftl
@@ -1,3 +1,3 @@
-# `parser-struct-literal-body-without-path` isn't provided by this resource at all, so the
+# `parser_struct_literal_body_without_path` isn't provided by this resource at all, so the
 # fallback should be used.
 foo = bar
diff --git a/src/test/run-make/translation/working.ftl b/src/test/run-make/translation/working.ftl
index 4681b879cda..d5ea8673875 100644
--- a/src/test/run-make/translation/working.ftl
+++ b/src/test/run-make/translation/working.ftl
@@ -1,2 +1,2 @@
-parser-struct-literal-body-without-path = this is a test message
+parser_struct_literal_body_without_path = this is a test message
     .suggestion = this is a test suggestion
diff --git a/src/test/rustdoc-json/enum_variant_hidden.rs b/src/test/rustdoc-json/enum_variant_hidden.rs
new file mode 100644
index 00000000000..96c96a975d3
--- /dev/null
+++ b/src/test/rustdoc-json/enum_variant_hidden.rs
@@ -0,0 +1,13 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/100529>.
+
+#![no_core]
+#![feature(no_core)]
+
+// @has enum_variant_hidden.json "$.index[*][?(@.name=='ParseError')]"
+// @has - "$.index[*][?(@.name=='UnexpectedEndTag')]"
+// @is - "$.index[*][?(@.name=='UnexpectedEndTag')].inner.variant_kind" '"tuple"'
+// @is - "$.index[*][?(@.name=='UnexpectedEndTag')].inner.variant_inner" []
+
+pub enum ParseError {
+    UnexpectedEndTag(#[doc(hidden)] u32),
+}
diff --git a/src/test/rustdoc-json/impls/import_from_private.rs b/src/test/rustdoc-json/impls/import_from_private.rs
new file mode 100644
index 00000000000..ef4d8aa39f8
--- /dev/null
+++ b/src/test/rustdoc-json/impls/import_from_private.rs
@@ -0,0 +1,24 @@
+// https://github.com/rust-lang/rust/issues/100252
+
+#![feature(no_core)]
+#![no_core]
+
+mod bar {
+    // @set baz = import_from_private.json "$.index[*][?(@.kind=='struct')].id"
+    pub struct Baz;
+    // @set impl = - "$.index[*][?(@.kind=='impl')].id"
+    impl Baz {
+        // @set doit = - "$.index[*][?(@.kind=='method')].id"
+        pub fn doit() {}
+    }
+}
+
+// @set import = - "$.index[*][?(@.kind=='import')].id"
+pub use bar::Baz;
+
+// FIXME(adotinthevoid): Use hasexact once #99474 lands
+
+// @has - "$.index[*][?(@.kind=='module')].inner.items[*]" $import
+// @is  - "$.index[*][?(@.kind=='import')].inner.id" $baz
+// @has - "$.index[*][?(@.kind=='struct')].inner.impls[*]" $impl
+// @has - "$.index[*][?(@.kind=='impl')].inner.items[*]" $doit
diff --git a/src/test/ui-fulldeps/fluent-messages/label-with-hyphens.ftl b/src/test/ui-fulldeps/fluent-messages/label-with-hyphens.ftl
new file mode 100644
index 00000000000..84b6c3e6c00
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/label-with-hyphens.ftl
@@ -0,0 +1,2 @@
+some_slug = hi
+    .label-has-hyphens = test
diff --git a/src/test/ui-fulldeps/fluent-messages/missing-message.ftl b/src/test/ui-fulldeps/fluent-messages/missing-message.ftl
index 372b1a2e453..74b2aa1d44d 100644
--- a/src/test/ui-fulldeps/fluent-messages/missing-message.ftl
+++ b/src/test/ui-fulldeps/fluent-messages/missing-message.ftl
@@ -1 +1 @@
-missing-message = 
+missing_message =
diff --git a/src/test/ui-fulldeps/fluent-messages/slug-with-hyphens.ftl b/src/test/ui-fulldeps/fluent-messages/slug-with-hyphens.ftl
new file mode 100644
index 00000000000..07517c9a243
--- /dev/null
+++ b/src/test/ui-fulldeps/fluent-messages/slug-with-hyphens.ftl
@@ -0,0 +1 @@
+this-slug-has-hyphens = hi
diff --git a/src/test/ui-fulldeps/fluent-messages/test.rs b/src/test/ui-fulldeps/fluent-messages/test.rs
index 0390a07850b..f0f35780666 100644
--- a/src/test/ui-fulldeps/fluent-messages/test.rs
+++ b/src/test/ui-fulldeps/fluent-messages/test.rs
@@ -55,6 +55,24 @@ mod duplicate {
     }
 }
 
+mod slug_with_hyphens {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        slug_with_hyphens => "./slug-with-hyphens.ftl",
+//~^ ERROR name `this-slug-has-hyphens` contains a '-' character
+    }
+}
+
+mod label_with_hyphens {
+    use super::fluent_messages;
+
+    fluent_messages! {
+        label_with_hyphens => "./label-with-hyphens.ftl",
+//~^ ERROR attribute `label-has-hyphens` contains a '-' character
+    }
+}
+
 mod valid {
     use super::fluent_messages;
 
diff --git a/src/test/ui-fulldeps/fluent-messages/test.stderr b/src/test/ui-fulldeps/fluent-messages/test.stderr
index 526bca43f69..856642c4818 100644
--- a/src/test/ui-fulldeps/fluent-messages/test.stderr
+++ b/src/test/ui-fulldeps/fluent-messages/test.stderr
@@ -22,11 +22,11 @@ LL |         missing_message => "./missing-message.ftl",
    |
    = help: see additional errors emitted
 
-error: expected a message field for "missing-message"
+error: expected a message field for "missing_message"
  --> ./missing-message.ftl:1:1
   |
-1 | missing-message = 
-  | ^^^^^^^^^^^^^^^^^^
+1 | missing_message =
+  | ^^^^^^^^^^^^^^^^^
   |
 
 error: overrides existing message: `key`
@@ -41,5 +41,21 @@ help: previously defined in this resource
 LL |         a => "./duplicate-a.ftl",
    |         ^
 
-error: aborting due to 4 previous errors
+error: name `this-slug-has-hyphens` contains a '-' character
+  --> $DIR/test.rs:62:9
+   |
+LL |         slug_with_hyphens => "./slug-with-hyphens.ftl",
+   |         ^^^^^^^^^^^^^^^^^
+   |
+   = help: replace any '-'s with '_'s
+
+error: attribute `label-has-hyphens` contains a '-' character
+  --> $DIR/test.rs:71:9
+   |
+LL |         label_with_hyphens => "./label-with-hyphens.ftl",
+   |         ^^^^^^^^^^^^^^^^^^
+   |
+   = help: replace any '-'s with '_'s
+
+error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/argument-suggestions/complex.stderr b/src/test/ui/argument-suggestions/complex.stderr
index fa030a8f49d..bf49e744458 100644
--- a/src/test/ui/argument-suggestions/complex.stderr
+++ b/src/test/ui/argument-suggestions/complex.stderr
@@ -8,7 +8,7 @@ note: function defined here
   --> $DIR/complex.rs:11:4
    |
 LL | fn complex(_i: u32, _s: &str, _e: E, _f: F, _g: G, _x: X, _y: Y, _z: Z ) {}
-   |    ^^^^^^^ -------  --------  -----  -----  -----  -----  -----  ------
+   |    ^^^^^^^ -------  --------  -----  -----  -----  -----  -----  -----
 help: did you mean
    |
 LL |   complex(/* u32 */, &"", /* E */, F::X2, G{}, X {}, Y {}, Z {});
diff --git a/src/test/ui/c-variadic/issue-86053-1.stderr b/src/test/ui/c-variadic/issue-86053-1.stderr
index 5d119bb8557..60b379faf4e 100644
--- a/src/test/ui/c-variadic/issue-86053-1.stderr
+++ b/src/test/ui/c-variadic/issue-86053-1.stderr
@@ -44,19 +44,19 @@ error: `...` must be the last argument of a C-variadic function
   --> $DIR/issue-86053-1.rs:11:12
    |
 LL |     self , ... ,   self ,   self , ... ) where F : FnOnce ( & 'a & 'b usize ) {
-   |            ^^^^
+   |            ^^^
 
 error: only foreign or `unsafe extern "C"` functions may be C-variadic
   --> $DIR/issue-86053-1.rs:11:12
    |
 LL |     self , ... ,   self ,   self , ... ) where F : FnOnce ( & 'a & 'b usize ) {
-   |            ^^^^
+   |            ^^^
 
 error: only foreign or `unsafe extern "C"` functions may be C-variadic
   --> $DIR/issue-86053-1.rs:11:36
    |
 LL |     self , ... ,   self ,   self , ... ) where F : FnOnce ( & 'a & 'b usize ) {
-   |                                    ^^^^
+   |                                    ^^^
 
 error[E0412]: cannot find type `F` in this scope
   --> $DIR/issue-86053-1.rs:11:48
diff --git a/src/test/ui/coherence/issue-100191-2.rs b/src/test/ui/coherence/issue-100191-2.rs
new file mode 100644
index 00000000000..1c8316f87fa
--- /dev/null
+++ b/src/test/ui/coherence/issue-100191-2.rs
@@ -0,0 +1,12 @@
+//~ ERROR overflow evaluating the requirement `T: Trait<_>`
+
+#![feature(specialization, with_negative_coherence)]
+#![allow(incomplete_features)]
+
+pub trait Trait<T> {}
+
+default impl<T, U> Trait<T> for U {}
+
+impl<T> Trait<<T as Iterator>::Item> for T {}
+
+fn main() {}
diff --git a/src/test/ui/coherence/issue-100191-2.stderr b/src/test/ui/coherence/issue-100191-2.stderr
new file mode 100644
index 00000000000..ea09fb15bdf
--- /dev/null
+++ b/src/test/ui/coherence/issue-100191-2.stderr
@@ -0,0 +1,14 @@
+error[E0275]: overflow evaluating the requirement `T: Trait<_>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_100191_2`)
+note: required because of the requirements on the impl of `Trait<_>` for `T`
+  --> $DIR/issue-100191-2.rs:8:20
+   |
+LL | default impl<T, U> Trait<T> for U {}
+   |                    ^^^^^^^^     ^
+   = note: 128 redundant requirements hidden
+   = note: required because of the requirements on the impl of `Trait<_>` for `T`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0275`.
diff --git a/src/test/ui/coherence/issue-100191.rs b/src/test/ui/coherence/issue-100191.rs
new file mode 100644
index 00000000000..e8597fde54d
--- /dev/null
+++ b/src/test/ui/coherence/issue-100191.rs
@@ -0,0 +1,21 @@
+#![crate_type = "lib"]
+#![feature(specialization, with_negative_coherence)]
+#![allow(incomplete_features)]
+
+trait X {}
+trait Y: X {}
+trait Z {
+    type Assoc: Y;
+}
+struct A<T>(T);
+
+impl<T> Y for T where T: X {}
+impl<T: X> Z for A<T> {
+    type Assoc = T;
+}
+
+// this impl is invalid, but causes an ICE anyway
+impl<T> From<<A<T> as Z>::Assoc> for T {}
+//~^ ERROR type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+
+fn main() {}
diff --git a/src/test/ui/coherence/issue-100191.stderr b/src/test/ui/coherence/issue-100191.stderr
new file mode 100644
index 00000000000..1adb0f1e4fa
--- /dev/null
+++ b/src/test/ui/coherence/issue-100191.stderr
@@ -0,0 +1,12 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/issue-100191.rs:18:6
+   |
+LL | impl<T> From<<A<T> as Z>::Assoc> for T {}
+   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0210`.
diff --git a/src/test/ui/suggestions/dont-try-removing-the-field.rs b/src/test/ui/suggestions/dont-try-removing-the-field.rs
new file mode 100644
index 00000000000..948aa2b94d9
--- /dev/null
+++ b/src/test/ui/suggestions/dont-try-removing-the-field.rs
@@ -0,0 +1,17 @@
+// run-pass
+
+#![allow(dead_code)]
+
+struct Foo {
+    foo: i32,
+    bar: i32,
+    baz: (),
+}
+
+fn use_foo(x: Foo) -> (i32, i32) {
+    let Foo { foo, bar, baz } = x; //~ WARNING unused variable: `baz`
+                                   //~| help: try ignoring the field
+    return (foo, bar);
+}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/dont-try-removing-the-field.stderr b/src/test/ui/suggestions/dont-try-removing-the-field.stderr
new file mode 100644
index 00000000000..263171a4ac4
--- /dev/null
+++ b/src/test/ui/suggestions/dont-try-removing-the-field.stderr
@@ -0,0 +1,10 @@
+warning: unused variable: `baz`
+  --> $DIR/dont-try-removing-the-field.rs:12:25
+   |
+LL |     let Foo { foo, bar, baz } = x;
+   |                         ^^^ help: try ignoring the field: `baz: _`
+   |
+   = note: `#[warn(unused_variables)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/suggestions/suggest-ref-macro.stderr b/src/test/ui/suggestions/suggest-ref-macro.stderr
index 84cbc93571a..17de49fbd84 100644
--- a/src/test/ui/suggestions/suggest-ref-macro.stderr
+++ b/src/test/ui/suggestions/suggest-ref-macro.stderr
@@ -10,14 +10,8 @@ LL | #[hello]
 note: function defined here
   --> $DIR/suggest-ref-macro.rs:8:1
    |
-LL |   #[hello]
-   |  _-^^^^^^^
-LL | | fn abc() {}
-LL | |
-LL | | fn x(_: &mut i32) {}
-LL | |
-LL | | macro_rules! bla {
-   | |_____________-
+LL | #[hello]
+   | ^^^^^^^^
    = note: this error originates in the attribute macro `hello` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
diff --git a/src/test/ui/suggestions/try-removing-the-field.rs b/src/test/ui/suggestions/try-removing-the-field.rs
new file mode 100644
index 00000000000..9d0573ca255
--- /dev/null
+++ b/src/test/ui/suggestions/try-removing-the-field.rs
@@ -0,0 +1,17 @@
+// run-pass
+
+#![allow(dead_code)]
+
+struct Foo {
+    foo: i32,
+    bar: (),
+    baz: (),
+}
+
+fn use_foo(x: Foo) -> i32 {
+    let Foo { foo, bar, .. } = x; //~ WARNING unused variable: `bar`
+                                  //~| help: try removing the field
+    return foo;
+}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/try-removing-the-field.stderr b/src/test/ui/suggestions/try-removing-the-field.stderr
new file mode 100644
index 00000000000..448a2c3d2ec
--- /dev/null
+++ b/src/test/ui/suggestions/try-removing-the-field.stderr
@@ -0,0 +1,12 @@
+warning: unused variable: `bar`
+  --> $DIR/try-removing-the-field.rs:12:20
+   |
+LL |     let Foo { foo, bar, .. } = x;
+   |                    ^^^-
+   |                    |
+   |                    help: try removing the field
+   |
+   = note: `#[warn(unused_variables)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/type/type-check/issue-88577-check-fn-with-more-than-65535-arguments.stderr b/src/test/ui/type/type-check/issue-88577-check-fn-with-more-than-65535-arguments.stderr
index 615fd2ccb04..847bc517ea3 100644
--- a/src/test/ui/type/type-check/issue-88577-check-fn-with-more-than-65535-arguments.stderr
+++ b/src/test/ui/type/type-check/issue-88577-check-fn-with-more-than-65535-arguments.stderr
@@ -1,13 +1,13 @@
 error: function can not have more than 65535 arguments
-  --> $DIR/issue-88577-check-fn-with-more-than-65535-arguments.rs:6:24
+  --> $DIR/issue-88577-check-fn-with-more-than-65535-arguments.rs:6:22
    |
-LL |           fn _f($($t: ()),*) {}
-   |  ________________________^
-LL | |     }
-LL | | }
-LL | |
-LL | | many_args!{[_]########## ######}
-   | |____________^
+LL |         fn _f($($t: ()),*) {}
+   |                      ^
+...
+LL | many_args!{[_]########## ######}
+   | -------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `many_args` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 
diff --git a/src/tools/build-manifest/Cargo.toml b/src/tools/build-manifest/Cargo.toml
index c022d3aa0ac..c437bde5ae6 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 efe3f2b618b..1a6760d8c68 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -210,7 +210,7 @@ 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)