Rollup of 7 pull requests

CONTRIBUTING.md

@@ -12,6 +12,15 @@ Documentation for contributing to the compiler or tooling is located in the [Gui
 Development][rustc-dev-guide], commonly known as the [rustc-dev-guide]. Documentation for the
 standard library in the [Standard library developers Guide][std-dev-guide], commonly known as the [std-dev-guide].
 
+## Making changes to subtrees and submodules
+
+For submodules, changes need to be made against the repository corresponding the
+submodule, and not the main `rust-lang/rust` repository.
+
+For subtrees, prefer sending a PR against the subtree's repository if it does
+not need to be made against the main `rust-lang/rust` repostory (e.g. a
+rustc-dev-guide change that does not accompany a compiler change).
+
 ## About the [rustc-dev-guide]
 
 The [rustc-dev-guide] is meant to help document how rustc –the Rust compiler– works,

compiler/rustc_codegen_cranelift/rust-toolchain

@@ -1,4 +1,4 @@
 [toolchain]
-channel = "nightly-2025-01-10"
+channel = "nightly-2025-01-20"
 components = ["rust-src", "rustc-dev", "llvm-tools"]
 profile = "minimal"

compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh

@@ -176,12 +176,11 @@ diff --git a/src/tools/run-make-support/src/rustdoc.rs b/src/tools/run-make-supp
 index 9607ff02f96..b7d97caf9a2 100644
 --- a/src/tools/run-make-support/src/external_deps/rustdoc.rs
 +++ b/src/tools/run-make-support/src/external_deps/rustdoc.rs
-@@ -34,8 +34,6 @@ pub fn bare() -> Self {
+@@ -34,7 +34,6 @@ pub fn bare() -> Self {
      #[track_caller]
      pub fn new() -> Self {
          let mut cmd = setup_common();
--        let target_rpath_dir = env_var_os("TARGET_RPATH_DIR");
--        cmd.arg(format!("-L{}", target_rpath_dir.to_string_lossy()));
+-        cmd.arg("-L").arg(env_var_os("TARGET_RPATH_DIR"));
          Self { cmd }
      }
 

compiler/rustc_codegen_cranelift/src/driver/aot.rs

@@ -333,9 +333,17 @@ fn make_module(sess: &Session, name: String) -> UnwindModule<ObjectModule> {
 
     let mut builder =
         ObjectBuilder::new(isa, name + ".o", cranelift_module::default_libcall_names()).unwrap();
+
+    // Disable function sections by default on MSVC as it causes significant slowdowns with link.exe.
+    // Maybe link.exe has exponential behavior when there are many sections with the same name? Also
+    // explicitly disable it on MinGW as rustc already disables it by default on MinGW and as such
+    // isn't tested. If rustc enables it in the future on MinGW, we can re-enable it too once it has
+    // been on MinGW.
+    let default_function_sections = sess.target.function_sections && !sess.target.is_like_windows;
     builder.per_function_section(
-        sess.opts.unstable_opts.function_sections.unwrap_or(sess.target.function_sections),
+        sess.opts.unstable_opts.function_sections.unwrap_or(default_function_sections),
     );
+
     UnwindModule::new(ObjectModule::new(builder), true)
 }
 

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -1,4 +1,5 @@
 //! Codegen of intrinsics. This includes `extern "rust-intrinsic"`,
+//! functions marked with the `#[rustc_intrinsic]` attribute
 //! and LLVM intrinsics that have symbol names starting with `llvm.`.
 
 macro_rules! intrinsic_args {

compiler/rustc_driver_impl/src/lib.rs

@@ -53,7 +53,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_session::config::{
     CG_OPTIONS, ErrorOutputType, Input, OptionDesc, OutFileName, OutputType, UnstableOptions,
-    Z_OPTIONS, nightly_options,
+    Z_OPTIONS, nightly_options, parse_target_triple,
 };
 use rustc_session::getopts::{self, Matches};
 use rustc_session::lint::{Lint, LintId};
@@ -916,13 +916,7 @@ pub fn version_at_macro_invocation(
         safe_println!("host: {}", config::host_tuple());
         safe_println!("release: {release}");
 
-        let debug_flags = matches.opt_strs("Z");
-        let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
-        let opts = config::Options::default();
-        let sysroot = filesearch::materialize_sysroot(opts.maybe_sysroot.clone());
-        let target = config::build_target_config(early_dcx, &opts, &sysroot);
-
-        get_codegen_backend(early_dcx, &sysroot, backend_name, &target).print_version();
+        get_backend_from_raw_matches(early_dcx, matches).print_version();
     }
 }
 
@@ -1125,19 +1119,32 @@ pub fn describe_flag_categories(early_dcx: &EarlyDiagCtxt, matches: &Matches) ->
     }
 
     if cg_flags.iter().any(|x| *x == "passes=list") {
-        let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
-
-        let opts = config::Options::default();
-        let sysroot = filesearch::materialize_sysroot(opts.maybe_sysroot.clone());
-        let target = config::build_target_config(early_dcx, &opts, &sysroot);
-
-        get_codegen_backend(early_dcx, &sysroot, backend_name, &target).print_passes();
+        get_backend_from_raw_matches(early_dcx, matches).print_passes();
         return true;
     }
 
     false
 }
 
+/// Get the codegen backend based on the raw [`Matches`].
+///
+/// `rustc -vV` and `rustc -Cpasses=list` need to get the codegen backend before we have parsed all
+/// arguments and created a [`Session`]. This function reads `-Zcodegen-backend`, `--target` and
+/// `--sysroot` without validating any other arguments and loads the codegen backend based on these
+/// arguments.
+fn get_backend_from_raw_matches(
+    early_dcx: &EarlyDiagCtxt,
+    matches: &Matches,
+) -> Box<dyn CodegenBackend> {
+    let debug_flags = matches.opt_strs("Z");
+    let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
+    let target = parse_target_triple(early_dcx, matches);
+    let sysroot = filesearch::materialize_sysroot(matches.opt_str("sysroot").map(PathBuf::from));
+    let target = config::build_target_config(early_dcx, &target, &sysroot);
+
+    get_codegen_backend(early_dcx, &sysroot, backend_name, &target)
+}
+
 fn describe_debug_flags() {
     safe_println!("\nAvailable options:\n");
     print_flag_list("-Z", config::Z_OPTIONS);

compiler/rustc_interface/src/interface.rs

@@ -383,7 +383,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
     crate::callbacks::setup_callbacks();
 
     let sysroot = filesearch::materialize_sysroot(config.opts.maybe_sysroot.clone());
-    let target = config::build_target_config(&early_dcx, &config.opts, &sysroot);
+    let target = config::build_target_config(&early_dcx, &config.opts.target_triple, &sysroot);
     let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
     let path_mapping = config.opts.file_path_mapping();
     let hash_kind = config.opts.unstable_opts.src_hash_algorithm(&target);

compiler/rustc_interface/src/tests.rs

@@ -42,7 +42,8 @@ where
     let matches = optgroups().parse(args).unwrap();
     let sessopts = build_session_options(&mut early_dcx, &matches);
     let sysroot = filesearch::materialize_sysroot(sessopts.maybe_sysroot.clone());
-    let target = rustc_session::config::build_target_config(&early_dcx, &sessopts, &sysroot);
+    let target =
+        rustc_session::config::build_target_config(&early_dcx, &sessopts.target_triple, &sysroot);
     let hash_kind = sessopts.unstable_opts.src_hash_algorithm(&target);
     let checksum_hash_kind = sessopts.unstable_opts.checksum_hash_algorithm();
     let sm_inputs = Some(SourceMapInputs {

compiler/rustc_session/src/config.rs

@@ -1346,8 +1346,12 @@ pub fn build_configuration(sess: &Session, mut user_cfg: Cfg) -> Cfg {
     user_cfg
 }
 
-pub fn build_target_config(early_dcx: &EarlyDiagCtxt, opts: &Options, sysroot: &Path) -> Target {
-    match Target::search(&opts.target_triple, sysroot) {
+pub fn build_target_config(
+    early_dcx: &EarlyDiagCtxt,
+    target: &TargetTuple,
+    sysroot: &Path,
+) -> Target {
+    match Target::search(target, sysroot) {
         Ok((target, warnings)) => {
             for warning in warnings.warning_messages() {
                 early_dcx.early_warn(warning)

library/core/src/hint.rs

@@ -597,3 +597,138 @@ pub const fn black_box<T>(dummy: T) -> T {
 pub const fn must_use<T>(value: T) -> T {
     value
 }
+
+/// Hints to the compiler that a branch condition is likely to be true.
+/// Returns the value passed to it.
+///
+/// It can be used with `if` or boolean `match` expressions.
+///
+/// When used outside of a branch condition, it may still influence a nearby branch, but
+/// probably will not have any effect.
+///
+/// It can also be applied to parts of expressions, such as `likely(a) && unlikely(b)`, or to
+/// compound expressions, such as `likely(a && b)`. When applied to compound expressions, it has
+/// the following effect:
+/// ```text
+///     likely(!a) => !unlikely(a)
+///     likely(a && b) => likely(a) && likely(b)
+///     likely(a || b) => a || likely(b)
+/// ```
+///
+/// See also the function [`cold_path()`] which may be more appropriate for idiomatic Rust code.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(likely_unlikely)]
+/// use core::hint::likely;
+///
+/// fn foo(x: i32) {
+///     if likely(x > 0) {
+///         println!("this branch is likely to be taken");
+///     } else {
+///         println!("this branch is unlikely to be taken");
+///     }
+///
+///     match likely(x > 0) {
+///         true => println!("this branch is likely to be taken"),
+///         false => println!("this branch is unlikely to be taken"),
+///     }
+///
+///     // Use outside of a branch condition may still influence a nearby branch
+///     let cond = likely(x != 0);
+///     if cond {
+///         println!("this branch is likely to be taken");
+///     }
+/// }
+/// ```
+///
+///
+#[unstable(feature = "likely_unlikely", issue = "26179")]
+#[inline(always)]
+pub const fn likely(b: bool) -> bool {
+    crate::intrinsics::likely(b)
+}
+
+/// Hints to the compiler that a branch condition is unlikely to be true.
+/// Returns the value passed to it.
+///
+/// It can be used with `if` or boolean `match` expressions.
+///
+/// When used outside of a branch condition, it may still influence a nearby branch, but
+/// probably will not have any effect.
+///
+/// It can also be applied to parts of expressions, such as `likely(a) && unlikely(b)`, or to
+/// compound expressions, such as `unlikely(a && b)`. When applied to compound expressions, it has
+/// the following effect:
+/// ```text
+///     unlikely(!a) => !likely(a)
+///     unlikely(a && b) => a && unlikely(b)
+///     unlikely(a || b) => unlikely(a) || unlikely(b)
+/// ```
+///
+/// See also the function [`cold_path()`] which may be more appropriate for idiomatic Rust code.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(likely_unlikely)]
+/// use core::hint::unlikely;
+///
+/// fn foo(x: i32) {
+///     if unlikely(x > 0) {
+///         println!("this branch is unlikely to be taken");
+///     } else {
+///         println!("this branch is likely to be taken");
+///     }
+///
+///     match unlikely(x > 0) {
+///         true => println!("this branch is unlikely to be taken"),
+///         false => println!("this branch is likely to be taken"),
+///     }
+///
+///     // Use outside of a branch condition may still influence a nearby branch
+///     let cond = unlikely(x != 0);
+///     if cond {
+///         println!("this branch is likely to be taken");
+///     }
+/// }
+/// ```
+#[unstable(feature = "likely_unlikely", issue = "26179")]
+#[inline(always)]
+pub const fn unlikely(b: bool) -> bool {
+    crate::intrinsics::unlikely(b)
+}
+
+/// Hints to the compiler that given path is cold, i.e., unlikely to be taken. The compiler may
+/// choose to optimize paths that are not cold at the expense of paths that are cold.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(cold_path)]
+/// use core::hint::cold_path;
+///
+/// fn foo(x: &[i32]) {
+///     if let Some(first) = x.get(0) {
+///         // this is the fast path
+///     } else {
+///         // this path is unlikely
+///         cold_path();
+///     }
+/// }
+///
+/// fn bar(x: i32) -> i32 {
+///     match x {
+///         1 => 10,
+///         2 => 100,
+///         3 => { cold_path(); 1000 }, // this branch is unlikely
+///         _ => { cold_path(); 10000 }, // this is also unlikely
+///     }
+/// }
+/// ```
+#[unstable(feature = "cold_path", issue = "26179")]
+#[inline(always)]
+pub const fn cold_path() {
+    crate::intrinsics::cold_path()
+}

library/core/src/net/ip_addr.rs

@@ -1539,8 +1539,9 @@ impl Ipv6Addr {
     /// // Addresses reserved for benchmarking (`2001:2::/48`)
     /// assert_eq!(Ipv6Addr::new(0x2001, 2, 0, 0, 0, 0, 0, 1,).is_global(), false);
     ///
-    /// // Addresses reserved for documentation (`2001:db8::/32`)
+    /// // Addresses reserved for documentation (`2001:db8::/32` and `3fff::/20`)
     /// assert_eq!(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1).is_global(), false);
+    /// assert_eq!(Ipv6Addr::new(0x3fff, 0, 0, 0, 0, 0, 0, 0).is_global(), false);
     ///
     /// // Unique local addresses (`fc00::/7`)
     /// assert_eq!(Ipv6Addr::new(0xfc02, 0, 0, 0, 0, 0, 0, 1).is_global(), false);
@@ -1686,11 +1687,12 @@ impl Ipv6Addr {
     }
 
     /// Returns [`true`] if this is an address reserved for documentation
-    /// (`2001:db8::/32`).
+    /// (`2001:db8::/32` and `3fff::/20`).
     ///
-    /// This property is defined in [IETF RFC 3849].
+    /// This property is defined by [IETF RFC 3849] and [IETF RFC 9637].
     ///
     /// [IETF RFC 3849]: https://tools.ietf.org/html/rfc3849
+    /// [IETF RFC 9637]: https://tools.ietf.org/html/rfc9637
     ///
     /// # Examples
     ///
@@ -1701,12 +1703,13 @@ impl Ipv6Addr {
     ///
     /// assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff).is_documentation(), false);
     /// assert_eq!(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 0).is_documentation(), true);
+    /// assert_eq!(Ipv6Addr::new(0x3fff, 0, 0, 0, 0, 0, 0, 0).is_documentation(), true);
     /// ```
     #[unstable(feature = "ip", issue = "27709")]
     #[must_use]
     #[inline]
     pub const fn is_documentation(&self) -> bool {
-        (self.segments()[0] == 0x2001) && (self.segments()[1] == 0xdb8)
+        matches!(self.segments(), [0x2001, 0xdb8, ..] | [0x3fff, 0..=0x0fff, ..])
     }
 
     /// Returns [`true`] if this is an address reserved for benchmarking (`2001:2::/48`).

library/core/tests/net/ip_addr.rs

@@ -332,6 +332,7 @@ fn ip_properties() {
     check!("ff08::", global | multicast);
     check!("ff0e::", global | multicast);
     check!("2001:db8:85a3::8a2e:370:7334", doc);
+    check!("3fff:fff:ffff:ffff:ffff:ffff:ffff:ffff", doc);
     check!("2001:2::ac32:23ff:21", benchmarking);
     check!("102:304:506:708:90a:b0c:d0e:f10", global);
 }
@@ -790,6 +791,15 @@ fn ipv6_properties() {
         documentation
     );
 
+    check!(
+        "3fff:fff:ffff:ffff:ffff:ffff:ffff:ffff",
+        &[
+            0x3f, 0xff, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+            0xff, 0xff
+        ],
+        documentation
+    );
+
     check!(
         "2001:2::ac32:23ff:21",
         &[0x20, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0xac, 0x32, 0x23, 0xff, 0, 0x21],

src/tools/miri/tests/fail/intrinsics/copy_overlapping.rs

@@ -1,9 +1,8 @@
 #![feature(intrinsics)]
 
 // Directly call intrinsic to avoid debug assertions in libstd
-extern "rust-intrinsic" {
-    fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
-}
+#[rustc_intrinsic]
+unsafe fn copy_nonoverlapping<T>(_src: *const T, _dst: *mut T, _count: usize);
 
 fn main() {
     let mut data = [0u8; 16];

src/tools/miri/tests/fail/intrinsics/copy_unaligned.rs

@@ -1,9 +1,8 @@
 #![feature(intrinsics)]
 
 // Directly call intrinsic to avoid debug assertions in libstd
-extern "rust-intrinsic" {
-    fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
-}
+#[rustc_intrinsic]
+unsafe fn copy_nonoverlapping<T>(_src: *const T, _dst: *mut T, _count: usize);
 
 fn main() {
     let mut data = [0u16; 8];

src/tools/miri/tests/fail/intrinsics/ctlz_nonzero.rs

@@ -1,9 +1,8 @@
 #![feature(intrinsics)]
 
 mod rusti {
-    extern "rust-intrinsic" {
-        pub fn ctlz_nonzero<T>(x: T) -> u32;
-    }
+    #[rustc_intrinsic]
+    pub unsafe fn ctlz_nonzero<T>(_x: T) -> u32;
 }
 
 pub fn main() {