Merge ref '269d5b56bcfd' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: 269d5b5
Filtered ref: a221b1d3ebb78ec8a01dcb1fe6bb165378e2f5c9

This merge was created using https://github.com/rust-lang/josh-sync.

Author: The Miri Cronjob Bot

alloc/src/boxed.rs

@@ -2128,11 +2128,6 @@ impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> {
 
 #[stable(feature = "box_error", since = "1.8.0")]
 impl<E: Error> Error for Box<E> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn Error> {
         Error::cause(&**self)

alloc/src/boxed/convert.rs

@@ -608,12 +608,7 @@ impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a> {
     fn from(err: String) -> Box<dyn Error + Send + Sync + 'a> {
         struct StringError(String);
 
-        impl Error for StringError {
-            #[allow(deprecated)]
-            fn description(&self) -> &str {
-                &self.0
-            }
-        }
+        impl Error for StringError {}
 
         impl fmt::Display for StringError {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

alloc/src/collections/btree/map.rs

@@ -40,30 +40,15 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 /// An ordered map based on a [B-Tree].
 ///
-/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
-/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
-/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
-/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
-/// is done is *very* inefficient for modern computer architectures. In particular, every element
-/// is stored in its own individually heap-allocated node. This means that every single insertion
-/// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
-/// are both notably expensive things to do in practice, we are forced to, at the very least,
-/// reconsider the BST strategy.
-///
-/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
-/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
-/// searches. However, this does mean that searches will have to do *more* comparisons on average.
-/// The precise number of comparisons depends on the node search strategy used. For optimal cache
-/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
-/// the node using binary search. As a compromise, one could also perform a linear search
-/// that initially only checks every i<sup>th</sup> element for some choice of i.
+/// Given a key type with a [total order], an ordered map stores its entries in key order.
+/// That means that keys must be of a type that implements the [`Ord`] trait,
+/// such that two keys can always be compared to determine their [`Ordering`].
+/// Examples of keys with a total order are strings with lexicographical order,
+/// and numbers with their natural order.
 ///
-/// Currently, our implementation simply performs naive linear search. This provides excellent
-/// performance on *small* nodes of elements which are cheap to compare. However in the future we
-/// would like to further explore choosing the optimal search strategy based on the choice of B,
-/// and possibly other factors. Using linear search, searching for a random element is expected
-/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
-/// however, performance is excellent.
+/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
+/// [`BTreeMap::keys`] produce their items in key order, and take worst-case logarithmic and
+/// amortized constant time per item returned.
 ///
 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
@@ -72,14 +57,6 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// `BTreeMap` that observed the logic error and not result in undefined behavior. This could
 /// include panics, incorrect results, aborts, memory leaks, and non-termination.
 ///
-/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
-/// [`BTreeMap::keys`] produce their items in order by key, and take worst-case logarithmic and
-/// amortized constant time per item returned.
-///
-/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
-/// [`Cell`]: core::cell::Cell
-/// [`RefCell`]: core::cell::RefCell
-///
 /// # Examples
 ///
 /// ```
@@ -169,6 +146,43 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// // modify an entry before an insert with in-place mutation
 /// player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
 /// ```
+///
+/// # Background
+///
+/// A B-tree is (like) a [binary search tree], but adapted to the natural granularity that modern
+/// machines like to consume data at. This means that each node contains an entire array of elements,
+/// instead of just a single element.
+///
+/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
+/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
+/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum number of
+/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
+/// is done is *very* inefficient for modern computer architectures. In particular, every element
+/// is stored in its own individually heap-allocated node. This means that every single insertion
+/// triggers a heap-allocation, and every comparison is a potential cache-miss due to the indirection.
+/// Since both heap-allocations and cache-misses are notably expensive in practice, we are forced to,
+/// at the very least, reconsider the BST strategy.
+///
+/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
+/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
+/// searches. However, this does mean that searches will have to do *more* comparisons on average.
+/// The precise number of comparisons depends on the node search strategy used. For optimal cache
+/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
+/// the node using binary search. As a compromise, one could also perform a linear search
+/// that initially only checks every i<sup>th</sup> element for some choice of i.
+///
+/// Currently, our implementation simply performs naive linear search. This provides excellent
+/// performance on *small* nodes of elements which are cheap to compare. However in the future we
+/// would like to further explore choosing the optimal search strategy based on the choice of B,
+/// and possibly other factors. Using linear search, searching for a random element is expected
+/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
+/// however, performance is excellent.
+///
+/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
+/// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
+/// [total order]: https://en.wikipedia.org/wiki/Total_order
+/// [`Cell`]: core::cell::Cell
+/// [`RefCell`]: core::cell::RefCell
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "BTreeMap")]
 #[rustc_insignificant_dtor]

alloc/src/collections/btree/map/entry.rs

@@ -136,10 +136,6 @@ impl<'a, K: Debug + Ord, V: Debug, A: Allocator + Clone> fmt::Display
 impl<'a, K: core::fmt::Debug + Ord, V: core::fmt::Debug> core::error::Error
     for crate::collections::btree_map::OccupiedError<'a, K, V>
 {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "key already exists"
-    }
 }
 
 impl<'a, K: Ord, V, A: Allocator + Clone> Entry<'a, K, V, A> {

alloc/src/ffi/c_str.rs

@@ -1061,17 +1061,10 @@ impl IntoStringError {
     }
 }
 
-impl IntoStringError {
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-}
-
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl fmt::Display for IntoStringError {
-    #[allow(deprecated, deprecated_in_future)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.description().fmt(f)
+        "C string contained non-utf8 bytes".fmt(f)
     }
 }
 
@@ -1291,23 +1284,13 @@ impl PartialEq<CString> for Cow<'_, CStr> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl core::error::Error for NulError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "nul byte found in data"
-    }
-}
+impl core::error::Error for NulError {}
 
 #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
 impl core::error::Error for FromVecWithNulError {}
 
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl core::error::Error for IntoStringError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-
     fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
         Some(&self.error)
     }

alloc/src/raw_vec/mod.rs

@@ -155,7 +155,7 @@ impl RawVecInner<Global> {
 }
 
 // Tiny Vecs are dumb. Skip to:
-// - 8 if the element size is 1, because any heap allocators is likely
+// - 8 if the element size is 1, because any heap allocator is likely
 //   to round up a request of less than 8 bytes to at least 8 bytes.
 // - 4 if elements are moderate-sized (<= 1 KiB).
 // - 1 otherwise, to avoid wasting too much space for very short Vecs.

alloc/src/string.rs

@@ -2285,20 +2285,10 @@ impl fmt::Display for FromUtf16Error {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for FromUtf8Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "invalid utf-8"
-    }
-}
+impl Error for FromUtf8Error {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for FromUtf16Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "invalid utf-16"
-    }
-}
+impl Error for FromUtf16Error {}
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]

alloc/src/sync.rs

@@ -4113,11 +4113,6 @@ impl<T: ?Sized, A: Allocator> Drop for UniqueArcUninit<T, A> {
 
 #[stable(feature = "arc_error", since = "1.52.0")]
 impl<T: core::error::Error + ?Sized> core::error::Error for Arc<T> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        core::error::Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn core::error::Error> {
         core::error::Error::cause(&**self)

compiler-builtins/compiler-builtins/README.md

@@ -10,6 +10,16 @@ to be added as an explicit dependency in `Cargo.toml`.
 
 [`compiler-rt`]: https://github.com/llvm/llvm-project/tree/1b1dc505057322f4fa1110ef4f53c44347f52986/compiler-rt
 
+## Configuration
+
+`compiler-builtins` can be configured with the following environment variables when the `c` feature
+is enabled:
+
+- `LLVM_COMPILER_RT_LIB`
+- `RUST_COMPILER_RT_ROOT`
+
+See `build.rs` for details.
+
 ## Contributing
 
 See [CONTRIBUTING.md](CONTRIBUTING.md).

compiler-builtins/compiler-builtins/build.rs

@@ -540,20 +540,28 @@ mod c {
             sources.extend(&[("__emutls_get_address", "emutls.c")]);
         }
 
+        // Optionally, link against a prebuilt llvm compiler-rt containing the builtins
+        // library. Only the builtins library is required. On many platforms, this is
+        // available as a library named libclang_rt.builtins.a.
+        let link_against_prebuilt_rt = env::var_os("LLVM_COMPILER_RT_LIB").is_some();
+
         // When compiling the C code we require the user to tell us where the
         // source code is, and this is largely done so when we're compiling as
         // part of rust-lang/rust we can use the same llvm-project repository as
         // rust-lang/rust.
         let root = match env::var_os("RUST_COMPILER_RT_ROOT") {
             Some(s) => PathBuf::from(s),
+            // If a prebuild libcompiler-rt is provided, set a valid
+            // path to simplify later logic. Nothing should be compiled.
+            None if link_against_prebuilt_rt => PathBuf::new(),
             None => {
                 panic!(
                     "RUST_COMPILER_RT_ROOT is not set. You may need to run \
                     `ci/download-compiler-rt.sh`."
                 );
             }
         };
-        if !root.exists() {
+        if !link_against_prebuilt_rt && !root.exists() {
             panic!("RUST_COMPILER_RT_ROOT={} does not exist", root.display());
         }
 
@@ -569,7 +577,7 @@ mod c {
         let src_dir = root.join("lib/builtins");
         if target.arch == "aarch64" && target.env != "msvc" && target.os != "uefi" {
             // See below for why we're building these as separate libraries.
-            build_aarch64_out_of_line_atomics_libraries(&src_dir, cfg);
+            build_aarch64_out_of_line_atomics_libraries(&src_dir, cfg, link_against_prebuilt_rt);
 
             // Some run-time CPU feature detection is necessary, as well.
             let cpu_model_src = if src_dir.join("cpu_model.c").exists() {
@@ -583,20 +591,45 @@ mod c {
         let mut added_sources = HashSet::new();
         for (sym, src) in sources.map.iter() {
             let src = src_dir.join(src);
-            if added_sources.insert(src.clone()) {
+            if !link_against_prebuilt_rt && added_sources.insert(src.clone()) {
                 cfg.file(&src);
                 println!("cargo:rerun-if-changed={}", src.display());
             }
             println!("cargo:rustc-cfg={}=\"optimized-c\"", sym);
         }
 
-        cfg.compile("libcompiler-rt.a");
+        if link_against_prebuilt_rt {
+            let rt_builtins_ext = PathBuf::from(env::var_os("LLVM_COMPILER_RT_LIB").unwrap());
+            if !rt_builtins_ext.exists() {
+                panic!(
+                    "LLVM_COMPILER_RT_LIB={} does not exist",
+                    rt_builtins_ext.display()
+                );
+            }
+            if let Some(dir) = rt_builtins_ext.parent() {
+                println!("cargo::rustc-link-search=native={}", dir.display());
+            }
+            if let Some(lib) = rt_builtins_ext.file_name() {
+                println!(
+                    "cargo::rustc-link-lib=static:+verbatim={}",
+                    lib.to_str().unwrap()
+                );
+            }
+        } else {
+            cfg.compile("libcompiler-rt.a");
+        }
     }
 
-    fn build_aarch64_out_of_line_atomics_libraries(builtins_dir: &Path, cfg: &mut cc::Build) {
+    fn build_aarch64_out_of_line_atomics_libraries(
+        builtins_dir: &Path,
+        cfg: &mut cc::Build,
+        link_against_prebuilt_rt: bool,
+    ) {
         let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
         let outlined_atomics_file = builtins_dir.join("aarch64").join("lse.S");
-        println!("cargo:rerun-if-changed={}", outlined_atomics_file.display());
+        if !link_against_prebuilt_rt {
+            println!("cargo:rerun-if-changed={}", outlined_atomics_file.display());
+        }
 
         cfg.include(&builtins_dir);
 
@@ -609,6 +642,13 @@ mod c {
                 for (model_number, model_name) in
                     &[(1, "relax"), (2, "acq"), (3, "rel"), (4, "acq_rel")]
                 {
+                    let sym = format!("__aarch64_{}{}_{}", instruction_type, size, model_name);
+                    println!("cargo:rustc-cfg={}=\"optimized-c\"", sym);
+
+                    if link_against_prebuilt_rt {
+                        continue;
+                    }
+
                     // The original compiler-rt build system compiles the same
                     // source file multiple times with different compiler
                     // options. Here we do something slightly different: we
@@ -632,9 +672,6 @@ mod c {
                     .unwrap();
                     drop(file);
                     cfg.file(path);
-
-                    let sym = format!("__aarch64_{}{}_{}", instruction_type, size, model_name);
-                    println!("cargo:rustc-cfg={}=\"optimized-c\"", sym);
                 }
             }
         }