diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index ffa582737ca8c..faa14a6c573e3 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -36,7 +36,7 @@ use crate::builder::gpu_offload::scalar_width;
 use crate::common::AsCCharPtr;
 use crate::errors::{
     CopyBitcode, FromLlvmDiag, FromLlvmOptimizationDiag, LlvmError, ParseTargetMachineConfig,
-    UnknownCompression, WithLlvmError, WriteBytecode,
+    UnsupportedCompression, WithLlvmError, WriteBytecode,
 };
 use crate::llvm::diagnostic::OptimizationDiagnosticKind::*;
 use crate::llvm::{self, DiagnosticInfo};
@@ -248,7 +248,7 @@ pub(crate) fn target_machine_factory(
             if llvm::LLVMRustLLVMHasZlibCompression() {
                 llvm::CompressionKind::Zlib
             } else {
-                sess.dcx().emit_warn(UnknownCompression { algorithm: "zlib" });
+                sess.dcx().emit_warn(UnsupportedCompression { algorithm: "zlib" });
                 llvm::CompressionKind::None
             }
         }
@@ -256,7 +256,7 @@ pub(crate) fn target_machine_factory(
             if llvm::LLVMRustLLVMHasZstdCompression() {
                 llvm::CompressionKind::Zstd
             } else {
-                sess.dcx().emit_warn(UnknownCompression { algorithm: "zstd" });
+                sess.dcx().emit_warn(UnsupportedCompression { algorithm: "zstd" });
                 llvm::CompressionKind::None
             }
         }
diff --git a/compiler/rustc_codegen_llvm/src/errors.rs b/compiler/rustc_codegen_llvm/src/errors.rs
index 9fb406516f66a..880abb3fbc248 100644
--- a/compiler/rustc_codegen_llvm/src/errors.rs
+++ b/compiler/rustc_codegen_llvm/src/errors.rs
@@ -182,9 +182,9 @@ pub(crate) struct CopyBitcode {
 
 #[derive(Diagnostic)]
 #[diag(
-    "unknown debuginfo compression algorithm {$algorithm} - will fall back to uncompressed debuginfo"
+    "unsupported debuginfo compression algorithm {$algorithm} - will fall back to uncompressed debuginfo"
 )]
-pub(crate) struct UnknownCompression {
+pub(crate) struct UnsupportedCompression {
     pub algorithm: &'static str,
 }
 
diff --git a/compiler/rustc_middle/src/dep_graph/serialized.rs b/compiler/rustc_middle/src/dep_graph/serialized.rs
index 8a4ac4b5e5acd..2f3d9eac7386c 100644
--- a/compiler/rustc_middle/src/dep_graph/serialized.rs
+++ b/compiler/rustc_middle/src/dep_graph/serialized.rs
@@ -43,7 +43,7 @@ use std::cell::RefCell;
 use std::cmp::max;
 use std::sync::Arc;
 use std::sync::atomic::Ordering;
-use std::{iter, mem, u64};
+use std::{iter, mem};
 
 use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint};
 use rustc_data_structures::fx::FxHashMap;
diff --git a/library/alloc/src/collections/binary_heap/mod.rs b/library/alloc/src/collections/binary_heap/mod.rs
index 4ddfcde57280e..d46b1972b5b00 100644
--- a/library/alloc/src/collections/binary_heap/mod.rs
+++ b/library/alloc/src/collections/binary_heap/mod.rs
@@ -1364,6 +1364,37 @@ impl<T, A: Allocator> BinaryHeap<T, A> {
         self.data.as_slice()
     }
 
+    /// Returns a mutable slice of all values in the underlying vector.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the slice remains a max-heap, i.e. for all indices
+    /// `0 < i < slice.len()`, `slice[(i - 1) / 2] >= slice[i]`, before the borrow ends
+    /// and the binary heap is used.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(binary_heap_as_mut_slice)]
+    ///
+    /// use std::collections::BinaryHeap;
+    ///
+    /// let mut heap = BinaryHeap::<u32>::from([1, 2, 3, 4, 5, 6, 7]);
+    ///
+    /// unsafe {
+    ///     for value in heap.as_mut_slice() {
+    ///         *value = (*value).saturating_mul(2);
+    ///     }
+    /// }
+    /// ```
+    #[must_use]
+    #[unstable(feature = "binary_heap_as_mut_slice", issue = "154009")]
+    pub unsafe fn as_mut_slice(&mut self) -> &mut [T] {
+        self.data.as_mut_slice()
+    }
+
     /// Consumes the `BinaryHeap` and returns the underlying vector
     /// in arbitrary order.
     ///
diff --git a/library/core/src/iter/adapters/intersperse.rs b/library/core/src/iter/adapters/intersperse.rs
index bb94ed0a0a170..f64dea2df862c 100644
--- a/library/core/src/iter/adapters/intersperse.rs
+++ b/library/core/src/iter/adapters/intersperse.rs
@@ -1,5 +1,4 @@
 use crate::fmt;
-use crate::iter::{Fuse, FusedIterator};
 
 /// An iterator adapter that places a separator between all elements.
 ///
@@ -14,15 +13,7 @@ where
     started: bool,
     separator: I::Item,
     next_item: Option<I::Item>,
-    iter: Fuse<I>,
-}
-
-#[unstable(feature = "iter_intersperse", issue = "79524")]
-impl<I> FusedIterator for Intersperse<I>
-where
-    I: FusedIterator,
-    I::Item: Clone,
-{
+    iter: I,
 }
 
 impl<I: Iterator> Intersperse<I>
@@ -30,7 +21,7 @@ where
     I::Item: Clone,
 {
     pub(in crate::iter) fn new(iter: I, separator: I::Item) -> Self {
-        Self { started: false, separator, next_item: None, iter: iter.fuse() }
+        Self { started: false, separator, next_item: None, iter }
     }
 }
 
@@ -57,8 +48,9 @@ where
                 }
             }
         } else {
-            self.started = true;
-            self.iter.next()
+            let item = self.iter.next();
+            self.started = item.is_some();
+            item
         }
     }
 
@@ -95,15 +87,7 @@ where
     started: bool,
     separator: G,
     next_item: Option<I::Item>,
-    iter: Fuse<I>,
-}
-
-#[unstable(feature = "iter_intersperse", issue = "79524")]
-impl<I, G> FusedIterator for IntersperseWith<I, G>
-where
-    I: FusedIterator,
-    G: FnMut() -> I::Item,
-{
+    iter: I,
 }
 
 #[unstable(feature = "iter_intersperse", issue = "79524")]
@@ -146,7 +130,7 @@ where
     G: FnMut() -> I::Item,
 {
     pub(in crate::iter) fn new(iter: I, separator: G) -> Self {
-        Self { started: false, separator, next_item: None, iter: iter.fuse() }
+        Self { started: false, separator, next_item: None, iter }
     }
 }
 
@@ -173,8 +157,9 @@ where
                 }
             }
         } else {
-            self.started = true;
-            self.iter.next()
+            let item = self.iter.next();
+            self.started = item.is_some();
+            item
         }
     }
 
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 2e82f45771823..11b1c04ce0e20 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -635,11 +635,24 @@ pub const trait Iterator {
     /// of the original iterator.
     ///
     /// Specifically on fused iterators, it is guaranteed that the new iterator
-    /// places a copy of `separator` between adjacent `Some(_)` items. However,
-    /// for non-fused iterators, [`intersperse`] will create a new iterator that
-    /// is a fused version of the original iterator and place a copy of `separator`
-    /// between adjacent `Some(_)` items. This behavior for non-fused iterators
-    /// is subject to change.
+    /// places a copy of `separator` between *adjacent* `Some(_)` items. For non-fused iterators,
+    /// it is guaranteed that [`intersperse`] will create a new iterator that places a copy
+    /// of `separator` between `Some(_)` items, particularly just right before the subsequent
+    /// `Some(_)` item.
+    ///
+    /// For example, consider the following non-fused iterator:
+    ///
+    /// ```text
+    /// Some(1) -> Some(2) -> None -> Some(3) -> Some(4) -> ...
+    /// ```
+    ///
+    /// If this non-fused iterator were to be interspersed with `0`,
+    /// then the interspersed iterator will produce:
+    ///
+    /// ```text
+    /// Some(1) -> Some(0) -> Some(2) -> None -> Some(0) -> Some(3) -> Some(0) ->
+    /// Some(4) -> ...
+    /// ```
     ///
     /// In case `separator` does not implement [`Clone`] or needs to be
     /// computed every time, use [`intersperse_with`].
@@ -688,10 +701,23 @@ pub const trait Iterator {
     ///
     /// Specifically on fused iterators, it is guaranteed that the new iterator
     /// places an item generated by `separator` between adjacent `Some(_)` items.
-    /// However, for non-fused iterators, [`intersperse_with`] will create a new
-    /// iterator that is a fused version of the original iterator and place an item
-    /// generated by `separator` between adjacent `Some(_)` items. This
-    /// behavior for non-fused iterators is subject to change.
+    /// For non-fused iterators, it is guaranteed that [`intersperse_with`] will
+    /// create a new iterator that places an item generated by `separator` between `Some(_)`
+    /// items, particularly just right before the subsequent `Some(_)` item.
+    ///
+    /// For example, consider the following non-fused iterator:
+    ///
+    /// ```text
+    /// Some(1) -> Some(2) -> None -> Some(3) -> Some(4) -> ...
+    /// ```
+    ///
+    /// If this non-fused iterator were to be interspersed with a `separator` closure
+    /// that returns `0` repeatedly, the interspersed iterator will produce:
+    ///
+    /// ```text
+    /// Some(1) -> Some(0) -> Some(2) -> None -> Some(0) -> Some(3) -> Some(0) ->
+    /// Some(4) -> ...
+    /// ```
     ///
     /// The `separator` closure will be called exactly once each time an item
     /// is placed between two adjacent items from the underlying iterator;
diff --git a/library/coretests/tests/array.rs b/library/coretests/tests/array.rs
index 2b4429092e98b..5a24f02cbf3d9 100644
--- a/library/coretests/tests/array.rs
+++ b/library/coretests/tests/array.rs
@@ -646,7 +646,7 @@ fn array_mixed_equality_integers() {
 
 #[test]
 fn array_mixed_equality_nans() {
-    let array3: [f32; 3] = [1.0, std::f32::NAN, 3.0];
+    let array3: [f32; 3] = [1.0, f32::NAN, 3.0];
 
     let slice3: &[f32] = &{ array3 };
     assert!(!(array3 == slice3));
diff --git a/library/coretests/tests/iter/adapters/intersperse.rs b/library/coretests/tests/iter/adapters/intersperse.rs
index df6be79308be7..bcb7709077cd7 100644
--- a/library/coretests/tests/iter/adapters/intersperse.rs
+++ b/library/coretests/tests/iter/adapters/intersperse.rs
@@ -153,10 +153,6 @@ fn test_try_fold_specialization_intersperse_err() {
     assert_eq!(iter.next(), None);
 }
 
-// FIXME(iter_intersperse): `intersperse` current behavior may change for
-// non-fused iterators, so this test will likely have to
-// be adjusted; see PR #152855 and issue #79524
-// if `intersperse` doesn't change, remove this FIXME.
 #[test]
 fn test_non_fused_iterator_intersperse() {
     #[derive(Debug)]
@@ -183,24 +179,26 @@ fn test_non_fused_iterator_intersperse() {
     }
 
     let counter = 0;
-    // places a 2 between `Some(_)` items
+    // places a 1 between `Some(_)` items
     let non_fused_iter = TestCounter { counter };
-    let mut intersperse_iter = non_fused_iter.intersperse(2);
-    // Since `intersperse` currently transforms the original
-    // iterator into a fused iterator, this intersperse_iter
-    // should always have `None`
-    for _ in 0..counter + 6 {
-        assert_eq!(intersperse_iter.next(), None);
-    }
+    let mut intersperse_iter = non_fused_iter.intersperse(1);
+    // Interspersed iter produces:
+    // `None` -> `Some(2)` -> `None` -> `Some(1)` -> Some(4)` -> `None` ->  `Some(1)` ->
+    // `Some(6)` -> and then `None` endlessly
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(2));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(4));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(6));
+    assert_eq!(intersperse_iter.next(), None);
 
-    // Extra check to make sure it is `None` after processing 6 items
+    // Extra check to make sure it is `None` after processing all items
     assert_eq!(intersperse_iter.next(), None);
 }
 
-// FIXME(iter_intersperse): `intersperse` current behavior may change for
-// non-fused iterators, so this test will likely have to
-// be adjusted; see PR #152855 and issue #79524
-// if `intersperse` doesn't change, remove this FIXME.
 #[test]
 fn test_non_fused_iterator_intersperse_2() {
     #[derive(Debug)]
@@ -228,35 +226,26 @@ fn test_non_fused_iterator_intersperse_2() {
     }
 
     let counter = 0;
-    // places a 2 between `Some(_)` items
+    // places a 100 between `Some(_)` items
     let non_fused_iter = TestCounter { counter };
-    let mut intersperse_iter = non_fused_iter.intersperse(2);
-    // Since `intersperse` currently transforms the original
-    // iterator into a fused iterator, this interspersed iter
-    // will be `Some(1)` -> `Some(2)` -> `Some(2)` -> and then
-    // `None` endlessly
-    let mut items_processed = 0;
-    for num in 0..counter + 6 {
-        if num < 3 {
-            if num % 2 != 0 {
-                assert_eq!(intersperse_iter.next(), Some(2));
-            } else {
-                items_processed += 1;
-                assert_eq!(intersperse_iter.next(), Some(items_processed));
-            }
-        } else {
-            assert_eq!(intersperse_iter.next(), None);
-        }
-    }
+    let mut intersperse_iter = non_fused_iter.intersperse(100);
+    // Interspersed iter produces:
+    // `Some(1)` -> `Some(100)` -> `Some(2)` -> `None` -> `Some(100)`
+    //  -> `Some(4)` -> `Some(100)` -> `Some(5)` -> `None` endlessly
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(2));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(4));
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(5));
+    assert_eq!(intersperse_iter.next(), None);
 
     // Extra check to make sure it is `None` after processing 6 items
     assert_eq!(intersperse_iter.next(), None);
 }
 
-// FIXME(iter_intersperse): `intersperse_with` current behavior may change for
-// non-fused iterators, so this test will likely have to
-// be adjusted; see PR #152855 and issue #79524
-// if `intersperse_with` doesn't change, remove this FIXME.
 #[test]
 fn test_non_fused_iterator_intersperse_with() {
     #[derive(Debug)]
@@ -285,22 +274,24 @@ fn test_non_fused_iterator_intersperse_with() {
     let counter = 0;
     let non_fused_iter = TestCounter { counter };
     // places a 2 between `Some(_)` items
-    let mut intersperse_iter = non_fused_iter.intersperse_with(|| 2);
-    // Since `intersperse` currently transforms the original
-    // iterator into a fused iterator, this intersperse_iter
-    // should always have `None`
-    for _ in 0..counter + 6 {
-        assert_eq!(intersperse_iter.next(), None);
-    }
+    let mut intersperse_iter = non_fused_iter.intersperse_with(|| 1);
+    // Interspersed iter produces:
+    // `None` -> `Some(2)` -> `None` -> `Some(1)` -> Some(4)` -> `None` ->  `Some(1)` ->
+    // `Some(6)` -> and then `None` endlessly
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(2));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(4));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(6));
+    assert_eq!(intersperse_iter.next(), None);
 
     // Extra check to make sure it is `None` after processing 6 items
     assert_eq!(intersperse_iter.next(), None);
 }
 
-// FIXME(iter_intersperse): `intersperse_with` current behavior may change for
-// non-fused iterators, so this test will likely have to
-// be adjusted; see PR #152855 and issue #79524
-// if `intersperse_with` doesn't change, remove this FIXME.
 #[test]
 fn test_non_fused_iterator_intersperse_with_2() {
     #[derive(Debug)]
@@ -328,26 +319,21 @@ fn test_non_fused_iterator_intersperse_with_2() {
     }
 
     let counter = 0;
-    // places a 2 between `Some(_)` items
+    // places a 100 between `Some(_)` items
     let non_fused_iter = TestCounter { counter };
-    let mut intersperse_iter = non_fused_iter.intersperse(2);
-    // Since `intersperse` currently transforms the original
-    // iterator into a fused iterator, this interspersed iter
-    // will be `Some(1)` -> `Some(2)` -> `Some(2)` -> and then
-    // `None` endlessly
-    let mut items_processed = 0;
-    for num in 0..counter + 6 {
-        if num < 3 {
-            if num % 2 != 0 {
-                assert_eq!(intersperse_iter.next(), Some(2));
-            } else {
-                items_processed += 1;
-                assert_eq!(intersperse_iter.next(), Some(items_processed));
-            }
-        } else {
-            assert_eq!(intersperse_iter.next(), None);
-        }
-    }
+    let mut intersperse_iter = non_fused_iter.intersperse_with(|| 100);
+    // Interspersed iter produces:
+    // `Some(1)` -> `Some(100)` -> `Some(2)` -> `None` -> `Some(100)`
+    //  -> `Some(4)` -> `Some(100)` -> `Some(5)` -> `None` endlessly
+    assert_eq!(intersperse_iter.next(), Some(1));
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(2));
+    assert_eq!(intersperse_iter.next(), None);
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(4));
+    assert_eq!(intersperse_iter.next(), Some(100));
+    assert_eq!(intersperse_iter.next(), Some(5));
+    assert_eq!(intersperse_iter.next(), None);
 
     // Extra check to make sure it is `None` after processing 6 items
     assert_eq!(intersperse_iter.next(), None);
diff --git a/library/coretests/tests/num/int_macros.rs b/library/coretests/tests/num/int_macros.rs
index 37336f49ef1b6..2b641f595eba4 100644
--- a/library/coretests/tests/num/int_macros.rs
+++ b/library/coretests/tests/num/int_macros.rs
@@ -2,7 +2,8 @@ macro_rules! int_module {
     ($T:ident, $U:ident) => {
         use core::num::ParseIntError;
         use core::ops::{BitAnd, BitOr, BitXor, Not, Shl, Shr};
-        use core::$T::*;
+        const MAX: $T = $T::MAX;
+        const MIN: $T = $T::MIN;
 
         const UMAX: $U = $U::MAX;
 
diff --git a/library/coretests/tests/num/uint_macros.rs b/library/coretests/tests/num/uint_macros.rs
index 240c66fd5c715..8dfa0924bd369 100644
--- a/library/coretests/tests/num/uint_macros.rs
+++ b/library/coretests/tests/num/uint_macros.rs
@@ -2,15 +2,14 @@ macro_rules! uint_module {
     ($T:ident) => {
         use core::num::ParseIntError;
         use core::ops::{BitAnd, BitOr, BitXor, Not, Shl, Shr};
-        use core::$T::*;
 
         use crate::num;
 
         #[test]
         fn test_overflows() {
-            assert!(MAX > 0);
-            assert!(MIN <= 0);
-            assert!((MIN + MAX).wrapping_add(1) == 0);
+            assert!($T::MAX > 0);
+            assert!($T::MIN <= 0);
+            assert!(($T::MIN + $T::MAX).wrapping_add(1) == 0);
         }
 
         #[test]
@@ -25,7 +24,7 @@ macro_rules! uint_module {
             assert!(0b0110 as $T == (0b1100 as $T).bitxor(0b1010 as $T));
             assert!(0b1110 as $T == (0b0111 as $T).shl(1));
             assert!(0b0111 as $T == (0b1110 as $T).shr(1));
-            assert!(MAX - (0b1011 as $T) == (0b1011 as $T).not());
+            assert!($T::MAX - (0b1011 as $T) == (0b1011 as $T).not());
         }
 
         const A: $T = 0b0101100;
@@ -361,7 +360,7 @@ macro_rules! uint_module {
                     assert_eq_const_safe!($T: R.wrapping_pow(2), 1 as $T);
                     assert_eq_const_safe!(Option<$T>: R.checked_pow(2), None);
                     assert_eq_const_safe!(($T, bool): R.overflowing_pow(2), (1 as $T, true));
-                    assert_eq_const_safe!($T: R.saturating_pow(2), MAX);
+                    assert_eq_const_safe!($T: R.saturating_pow(2), $T::MAX);
                 }
             }
 
@@ -468,14 +467,14 @@ macro_rules! uint_module {
             fn test_next_multiple_of() {
                 assert_eq_const_safe!($T: (16 as $T).next_multiple_of(8), 16);
                 assert_eq_const_safe!($T: (23 as $T).next_multiple_of(8), 24);
-                assert_eq_const_safe!($T: MAX.next_multiple_of(1), MAX);
+                assert_eq_const_safe!($T: $T::MAX.next_multiple_of(1), $T::MAX);
             }
 
             fn test_checked_next_multiple_of() {
                 assert_eq_const_safe!(Option<$T>: (16 as $T).checked_next_multiple_of(8), Some(16));
                 assert_eq_const_safe!(Option<$T>: (23 as $T).checked_next_multiple_of(8), Some(24));
                 assert_eq_const_safe!(Option<$T>: (1 as $T).checked_next_multiple_of(0), None);
-                assert_eq_const_safe!(Option<$T>: MAX.checked_next_multiple_of(2), None);
+                assert_eq_const_safe!(Option<$T>: $T::MAX.checked_next_multiple_of(2), None);
             }
 
             fn test_is_next_multiple_of() {
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 1b7a41d697367..7a8ccdbc5043b 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -62,7 +62,7 @@ path = "../windows_link"
 rand = { version = "0.9.0", default-features = false, features = ["alloc"] }
 rand_xorshift = "0.4.0"
 
-[target.'cfg(any(all(target_family = "wasm", target_os = "unknown"), target_os = "xous", target_os = "vexos", all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
+[target.'cfg(any(all(target_family = "wasm", not(any(unix, target_os = "wasi"))), target_os = "xous", target_os = "vexos", all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
 dlmalloc = { version = "0.2.10", features = ['rustc-dep-of-std'] }
 
 [target.x86_64-fortanix-unknown-sgx.dependencies]
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index edf0127a665e3..d3e4417656e9a 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -15,7 +15,7 @@ use crate::ffi::{OsStr, OsString};
 use crate::num::NonZero;
 use crate::ops::Try;
 use crate::path::{Path, PathBuf};
-use crate::sys::{env as env_imp, os as os_imp};
+use crate::sys::{env as env_imp, paths as paths_imp};
 use crate::{array, fmt, io, sys};
 
 /// Returns the current working directory as a [`PathBuf`].
@@ -51,7 +51,7 @@ use crate::{array, fmt, io, sys};
 #[doc(alias = "GetCurrentDirectory")]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn current_dir() -> io::Result<PathBuf> {
-    os_imp::getcwd()
+    paths_imp::getcwd()
 }
 
 /// Changes the current working directory to the specified path.
@@ -78,7 +78,7 @@ pub fn current_dir() -> io::Result<PathBuf> {
 #[doc(alias = "chdir", alias = "SetCurrentDirectory", alias = "SetCurrentDirectoryW")]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn set_current_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
-    os_imp::chdir(path.as_ref())
+    paths_imp::chdir(path.as_ref())
 }
 
 /// An iterator over a snapshot of the environment variables of this process.
@@ -444,7 +444,7 @@ pub unsafe fn remove_var<K: AsRef<OsStr>>(key: K) {
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "env", since = "1.0.0")]
 pub struct SplitPaths<'a> {
-    inner: os_imp::SplitPaths<'a>,
+    inner: paths_imp::SplitPaths<'a>,
 }
 
 /// Parses input according to platform conventions for the `PATH`
@@ -480,7 +480,7 @@ pub struct SplitPaths<'a> {
 /// ```
 #[stable(feature = "env", since = "1.0.0")]
 pub fn split_paths<T: AsRef<OsStr> + ?Sized>(unparsed: &T) -> SplitPaths<'_> {
-    SplitPaths { inner: os_imp::split_paths(unparsed.as_ref()) }
+    SplitPaths { inner: paths_imp::split_paths(unparsed.as_ref()) }
 }
 
 #[stable(feature = "env", since = "1.0.0")]
@@ -508,7 +508,7 @@ impl fmt::Debug for SplitPaths<'_> {
 #[derive(Debug)]
 #[stable(feature = "env", since = "1.0.0")]
 pub struct JoinPathsError {
-    inner: os_imp::JoinPathsError,
+    inner: paths_imp::JoinPathsError,
 }
 
 /// Joins a collection of [`Path`]s appropriately for the `PATH`
@@ -579,7 +579,7 @@ where
     I: IntoIterator<Item = T>,
     T: AsRef<OsStr>,
 {
-    os_imp::join_paths(paths.into_iter()).map_err(|e| JoinPathsError { inner: e })
+    paths_imp::join_paths(paths.into_iter()).map_err(|e| JoinPathsError { inner: e })
 }
 
 #[stable(feature = "env", since = "1.0.0")]
@@ -641,7 +641,7 @@ impl Error for JoinPathsError {
 #[must_use]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn home_dir() -> Option<PathBuf> {
-    os_imp::home_dir()
+    paths_imp::home_dir()
 }
 
 /// Returns the path of a temporary directory.
@@ -701,7 +701,7 @@ pub fn home_dir() -> Option<PathBuf> {
 #[doc(alias = "GetTempPath", alias = "GetTempPath2")]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn temp_dir() -> PathBuf {
-    os_imp::temp_dir()
+    paths_imp::temp_dir()
 }
 
 /// Returns the full filesystem path of the current running executable.
@@ -752,7 +752,7 @@ pub fn temp_dir() -> PathBuf {
 /// ```
 #[stable(feature = "env", since = "1.0.0")]
 pub fn current_exe() -> io::Result<PathBuf> {
-    os_imp::current_exe()
+    paths_imp::current_exe()
 }
 
 /// An iterator over the arguments of a process, yielding a [`String`] value for
diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 885bf376b98ad..9643d3fcae662 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -815,7 +815,8 @@ impl File {
 
     /// Acquire an exclusive lock on the file. Blocks until the lock can be acquired.
     ///
-    /// This acquires an exclusive lock; no other file handle to this file may acquire another lock.
+    /// This acquires an exclusive lock; no other file handle to this file, in this or any other
+    /// process, may acquire another lock.
     ///
     /// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
     /// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
@@ -868,8 +869,8 @@ impl File {
 
     /// Acquire a shared (non-exclusive) lock on the file. Blocks until the lock can be acquired.
     ///
-    /// This acquires a shared lock; more than one file handle may hold a shared lock, but none may
-    /// hold an exclusive lock at the same time.
+    /// This acquires a shared lock; more than one file handle, in this or any other process, may
+    /// hold a shared lock, but none may hold an exclusive lock at the same time.
     ///
     /// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
     /// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
@@ -923,7 +924,8 @@ impl File {
     /// Returns `Err(TryLockError::WouldBlock)` if a different lock is already held on this file
     /// (via another handle/descriptor).
     ///
-    /// This acquires an exclusive lock; no other file handle to this file may acquire another lock.
+    /// This acquires an exclusive lock; no other file handle to this file, in this or any other
+    /// process, may acquire another lock.
     ///
     /// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
     /// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
@@ -987,8 +989,8 @@ impl File {
     /// Returns `Err(TryLockError::WouldBlock)` if a different lock is already held on this file
     /// (via another handle/descriptor).
     ///
-    /// This acquires a shared lock; more than one file handle may hold a shared lock, but none may
-    /// hold an exclusive lock at the same time.
+    /// This acquires a shared lock; more than one file handle, in this or any other process, may
+    /// hold a shared lock, but none may hold an exclusive lock at the same time.
     ///
     /// This lock may be advisory or mandatory. This lock is meant to interact with [`lock`],
     /// [`try_lock`], [`lock_shared`], [`try_lock_shared`], and [`unlock`]. Its interactions with
diff --git a/library/std/src/sys/args/windows.rs b/library/std/src/sys/args/windows.rs
index c1988657ff1b1..3c6995e372784 100644
--- a/library/std/src/sys/args/windows.rs
+++ b/library/std/src/sys/args/windows.rs
@@ -12,9 +12,9 @@ use crate::num::NonZero;
 use crate::os::windows::prelude::*;
 use crate::path::{Path, PathBuf};
 use crate::sys::helpers::WStrUnits;
-use crate::sys::pal::os::current_exe;
 use crate::sys::pal::{ensure_no_nuls, fill_utf16_buf};
 use crate::sys::path::get_long_path;
+use crate::sys::paths::current_exe;
 use crate::sys::{AsInner, c, to_u16s};
 use crate::{io, iter, ptr};
 
diff --git a/library/std/src/sys/env/unix.rs b/library/std/src/sys/env/unix.rs
index 66805ce3fa71e..7a19f97b3ad50 100644
--- a/library/std/src/sys/env/unix.rs
+++ b/library/std/src/sys/env/unix.rs
@@ -38,8 +38,25 @@ pub unsafe fn environ() -> *mut *const *const c_char {
     unsafe { libc::_NSGetEnviron() as *mut *const *const c_char }
 }
 
+// On FreeBSD, environ comes from CRT rather than libc
+#[cfg(target_os = "freebsd")]
+pub unsafe fn environ() -> *mut *const *const c_char {
+    use crate::sync::LazyLock;
+
+    struct Environ(*mut *const *const c_char);
+    unsafe impl Send for Environ {}
+    unsafe impl Sync for Environ {}
+
+    static ENVIRON: LazyLock<Environ> = LazyLock::new(|| {
+        Environ(unsafe {
+            libc::dlsym(libc::RTLD_DEFAULT, c"environ".as_ptr()) as *mut *const *const c_char
+        })
+    });
+    ENVIRON.0
+}
+
 // Use the `environ` static which is part of POSIX.
-#[cfg(not(target_vendor = "apple"))]
+#[cfg(not(any(target_os = "freebsd", target_vendor = "apple")))]
 pub unsafe fn environ() -> *mut *const *const c_char {
     unsafe extern "C" {
         static mut environ: *const *const c_char;
diff --git a/library/std/src/sys/io/error/windows.rs b/library/std/src/sys/io/error/windows.rs
index d7607082a30a0..c093443f30339 100644
--- a/library/std/src/sys/io/error/windows.rs
+++ b/library/std/src/sys/io/error/windows.rs
@@ -1,6 +1,9 @@
 use crate::sys::pal::{api, c};
 use crate::{io, ptr};
 
+#[cfg(test)]
+mod tests;
+
 pub fn errno() -> i32 {
     api::get_last_error().code as i32
 }
diff --git a/library/std/src/sys/pal/windows/os/tests.rs b/library/std/src/sys/io/error/windows/tests.rs
similarity index 93%
rename from library/std/src/sys/pal/windows/os/tests.rs
rename to library/std/src/sys/io/error/windows/tests.rs
index 458d6e11c2098..7fc545ad00666 100644
--- a/library/std/src/sys/pal/windows/os/tests.rs
+++ b/library/std/src/sys/io/error/windows/tests.rs
@@ -1,5 +1,5 @@
 use crate::io::Error;
-use crate::sys::c;
+use crate::sys::pal::c;
 
 // tests `error_string` above
 #[test]
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index 5ad23972860bb..fe0c103952414 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -18,6 +18,7 @@ pub mod io;
 pub mod net;
 pub mod os_str;
 pub mod path;
+pub mod paths;
 pub mod pipe;
 pub mod platform_version;
 pub mod process;
diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs
index f10a090a6e919..b18dc5b103b59 100644
--- a/library/std/src/sys/pal/hermit/mod.rs
+++ b/library/std/src/sys/pal/hermit/mod.rs
@@ -22,7 +22,6 @@ use crate::os::raw::c_char;
 use crate::sys::env;
 
 pub mod futex;
-pub mod os;
 pub mod time;
 
 pub fn unsupported<T>() -> io::Result<T> {
diff --git a/library/std/src/sys/pal/hermit/os.rs b/library/std/src/sys/pal/hermit/os.rs
deleted file mode 100644
index 188caded55d48..0000000000000
--- a/library/std/src/sys/pal/hermit/os.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-use crate::ffi::{OsStr, OsString};
-use crate::marker::PhantomData;
-use crate::path::{self, PathBuf};
-use crate::sys::unsupported;
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    Ok(PathBuf::from("/"))
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    unsupported()
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on hermit yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    PathBuf::from("/tmp")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/motor/mod.rs b/library/std/src/sys/pal/motor/mod.rs
index a520375a4bbff..705413cbe0a79 100644
--- a/library/std/src/sys/pal/motor/mod.rs
+++ b/library/std/src/sys/pal/motor/mod.rs
@@ -1,7 +1,5 @@
 #![allow(unsafe_op_in_unsafe_fn)]
 
-pub mod os;
-
 pub use moto_rt::futex;
 
 use crate::io;
diff --git a/library/std/src/sys/pal/motor/os.rs b/library/std/src/sys/pal/motor/os.rs
deleted file mode 100644
index 0af579303306e..0000000000000
--- a/library/std/src/sys/pal/motor/os.rs
+++ /dev/null
@@ -1,64 +0,0 @@
-use super::map_motor_error;
-use crate::error::Error as StdError;
-use crate::ffi::{OsStr, OsString};
-use crate::marker::PhantomData;
-use crate::os::motor::ffi::OsStrExt;
-use crate::path::{self, PathBuf};
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    moto_rt::fs::getcwd().map(PathBuf::from).map_err(map_motor_error)
-}
-
-pub fn chdir(path: &path::Path) -> io::Result<()> {
-    moto_rt::fs::chdir(path.as_os_str().as_str()).map_err(map_motor_error)
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on this platform yet".fmt(f)
-    }
-}
-
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    moto_rt::process::current_exe().map(PathBuf::from).map_err(map_motor_error)
-}
-
-pub fn temp_dir() -> PathBuf {
-    PathBuf::from(moto_rt::fs::TEMP_DIR)
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/sgx/mod.rs b/library/std/src/sys/pal/sgx/mod.rs
index 1de3ca4a5d79c..2b284cc40b94b 100644
--- a/library/std/src/sys/pal/sgx/mod.rs
+++ b/library/std/src/sys/pal/sgx/mod.rs
@@ -10,7 +10,6 @@ use crate::sync::atomic::{Atomic, AtomicBool, Ordering};
 
 pub mod abi;
 mod libunwind_integration;
-pub mod os;
 pub mod thread_parking;
 pub mod waitqueue;
 
diff --git a/library/std/src/sys/pal/sgx/os.rs b/library/std/src/sys/pal/sgx/os.rs
deleted file mode 100644
index 5b0af37a3d373..0000000000000
--- a/library/std/src/sys/pal/sgx/os.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-use crate::ffi::{OsStr, OsString};
-use crate::marker::PhantomData;
-use crate::path::{self, PathBuf};
-use crate::sys::{sgx_ineffective, unsupported};
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    sgx_ineffective(())
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported in SGX yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem in SGX")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/solid/mod.rs b/library/std/src/sys/pal/solid/mod.rs
index 1376af8304cf6..c3f9e47945901 100644
--- a/library/std/src/sys/pal/solid/mod.rs
+++ b/library/std/src/sys/pal/solid/mod.rs
@@ -19,7 +19,6 @@ pub mod itron {
 // `error` is `pub(crate)` so that it can be accessed by `itron/error.rs` as
 // `crate::sys::error`
 pub(crate) mod error;
-pub mod os;
 pub use self::itron::thread_parking;
 
 // SAFETY: must be called only once during runtime initialization.
diff --git a/library/std/src/sys/pal/solid/os.rs b/library/std/src/sys/pal/solid/os.rs
deleted file mode 100644
index 79bb91b179969..0000000000000
--- a/library/std/src/sys/pal/solid/os.rs
+++ /dev/null
@@ -1,56 +0,0 @@
-use super::unsupported;
-use crate::ffi::{OsStr, OsString};
-use crate::path::{self, PathBuf};
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    unsupported()
-}
-
-pub struct SplitPaths<'a>(&'a !);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        *self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on this platform yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    panic!("no standard temporary directory on this platform")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/teeos/mod.rs b/library/std/src/sys/pal/teeos/mod.rs
index 7d2ecdbf7ec4b..5caed277dbf59 100644
--- a/library/std/src/sys/pal/teeos/mod.rs
+++ b/library/std/src/sys/pal/teeos/mod.rs
@@ -7,7 +7,6 @@
 #![allow(dead_code)]
 
 pub mod conf;
-pub mod os;
 #[path = "../unix/time.rs"]
 pub mod time;
 
diff --git a/library/std/src/sys/pal/teeos/os.rs b/library/std/src/sys/pal/teeos/os.rs
deleted file mode 100644
index c86fa555e4117..0000000000000
--- a/library/std/src/sys/pal/teeos/os.rs
+++ /dev/null
@@ -1,62 +0,0 @@
-//! Implementation of `std::os` functionality for teeos
-
-use core::marker::PhantomData;
-
-use super::unsupported;
-use crate::ffi::{OsStr, OsString};
-use crate::path::PathBuf;
-use crate::{fmt, io, path};
-
-// Everything below are stubs and copied from unsupported.rs
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    unsupported()
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on this platform yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem on this platform")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/trusty/mod.rs b/library/std/src/sys/pal/trusty/mod.rs
index b785c2dbb7892..ec2d938ed8367 100644
--- a/library/std/src/sys/pal/trusty/mod.rs
+++ b/library/std/src/sys/pal/trusty/mod.rs
@@ -3,7 +3,5 @@
 #[path = "../unsupported/common.rs"]
 #[deny(unsafe_op_in_unsafe_fn)]
 mod common;
-#[path = "../unsupported/os.rs"]
-pub mod os;
 
 pub use common::*;
diff --git a/library/std/src/sys/pal/uefi/mod.rs b/library/std/src/sys/pal/uefi/mod.rs
index e4a8f50e4274d..67499d2c6f17c 100644
--- a/library/std/src/sys/pal/uefi/mod.rs
+++ b/library/std/src/sys/pal/uefi/mod.rs
@@ -14,7 +14,6 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
 pub mod helpers;
-pub mod os;
 pub mod system_time;
 
 #[cfg(test)]
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index 9931b4de0b9bf..0be150a0bfaa8 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -8,7 +8,6 @@ pub mod fuchsia;
 pub mod futex;
 #[cfg(target_os = "linux")]
 pub mod linux;
-pub mod os;
 pub mod stack_overflow;
 pub mod sync;
 pub mod thread_parking;
diff --git a/library/std/src/sys/pal/unix/stack_overflow.rs b/library/std/src/sys/pal/unix/stack_overflow.rs
index 632f619655b37..5d53de7fb7e21 100644
--- a/library/std/src/sys/pal/unix/stack_overflow.rs
+++ b/library/std/src/sys/pal/unix/stack_overflow.rs
@@ -429,6 +429,11 @@ mod imp {
 
     #[forbid(unsafe_op_in_unsafe_fn)]
     unsafe fn install_main_guard_linux(page_size: usize) -> Option<Range<usize>> {
+        // See the corresponding conditional in init().
+        // Avoid stack_start_aligned, which makes slow syscalls to read /proc/self/maps
+        if cfg!(panic = "immediate-abort") {
+            return None;
+        }
         // Linux doesn't allocate the whole stack right away, and
         // the kernel has its own stack-guard mechanism to fault
         // when growing too close to an existing mapping. If we map
@@ -456,6 +461,10 @@ mod imp {
     #[forbid(unsafe_op_in_unsafe_fn)]
     #[cfg(target_os = "freebsd")]
     unsafe fn install_main_guard_freebsd(page_size: usize) -> Option<Range<usize>> {
+        // See the corresponding conditional in install_main_guard_linux().
+        if cfg!(panic = "immediate-abort") {
+            return None;
+        }
         // FreeBSD's stack autogrows, and optionally includes a guard page
         // at the bottom. If we try to remap the bottom of the stack
         // ourselves, FreeBSD's guard page moves upwards. So we'll just use
@@ -489,6 +498,10 @@ mod imp {
 
     #[forbid(unsafe_op_in_unsafe_fn)]
     unsafe fn install_main_guard_bsds(page_size: usize) -> Option<Range<usize>> {
+        // See the corresponding conditional in install_main_guard_linux().
+        if cfg!(panic = "immediate-abort") {
+            return None;
+        }
         // OpenBSD stack already includes a guard page, and stack is
         // immutable.
         // NetBSD stack includes the guard page.
diff --git a/library/std/src/sys/pal/unsupported/mod.rs b/library/std/src/sys/pal/unsupported/mod.rs
index 0f157819d5a66..c4b14ab44436f 100644
--- a/library/std/src/sys/pal/unsupported/mod.rs
+++ b/library/std/src/sys/pal/unsupported/mod.rs
@@ -1,6 +1,4 @@
 #![deny(unsafe_op_in_unsafe_fn)]
 
-pub mod os;
-
 mod common;
 pub use common::*;
diff --git a/library/std/src/sys/pal/unsupported/os.rs b/library/std/src/sys/pal/unsupported/os.rs
deleted file mode 100644
index fe8addeafd2bc..0000000000000
--- a/library/std/src/sys/pal/unsupported/os.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-use super::unsupported;
-use crate::ffi::{OsStr, OsString};
-use crate::marker::PhantomData;
-use crate::path::{self, PathBuf};
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    unsupported()
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on this platform yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem on this platform")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/vexos/mod.rs b/library/std/src/sys/pal/vexos/mod.rs
index d1380ab8dff14..61bbe78f718af 100644
--- a/library/std/src/sys/pal/vexos/mod.rs
+++ b/library/std/src/sys/pal/vexos/mod.rs
@@ -1,6 +1,3 @@
-#[path = "../unsupported/os.rs"]
-pub mod os;
-
 #[expect(dead_code)]
 #[path = "../unsupported/common.rs"]
 mod unsupported_common;
diff --git a/library/std/src/sys/pal/wasi/mod.rs b/library/std/src/sys/pal/wasi/mod.rs
index 66d91078a5d54..6f60993509253 100644
--- a/library/std/src/sys/pal/wasi/mod.rs
+++ b/library/std/src/sys/pal/wasi/mod.rs
@@ -10,7 +10,6 @@ pub mod conf;
 #[allow(unused)]
 #[path = "../wasm/atomics/futex.rs"]
 pub mod futex;
-pub mod os;
 pub mod stack_overflow;
 #[path = "../unix/time.rs"]
 pub mod time;
diff --git a/library/std/src/sys/pal/wasm/mod.rs b/library/std/src/sys/pal/wasm/mod.rs
index 5f56eddd6a819..24a2ab8eca30f 100644
--- a/library/std/src/sys/pal/wasm/mod.rs
+++ b/library/std/src/sys/pal/wasm/mod.rs
@@ -16,9 +16,6 @@
 
 #![deny(unsafe_op_in_unsafe_fn)]
 
-#[path = "../unsupported/os.rs"]
-pub mod os;
-
 #[cfg(target_feature = "atomics")]
 #[path = "atomics/futex.rs"]
 pub mod futex;
diff --git a/library/std/src/sys/pal/windows/mod.rs b/library/std/src/sys/pal/windows/mod.rs
index 0cd9152614716..b67ba37749789 100644
--- a/library/std/src/sys/pal/windows/mod.rs
+++ b/library/std/src/sys/pal/windows/mod.rs
@@ -18,7 +18,6 @@ pub mod c;
 #[cfg(not(target_vendor = "win7"))]
 pub mod futex;
 pub mod handle;
-pub mod os;
 pub mod time;
 cfg_select! {
     // We don't care about printing nice error messages for panic=immediate-abort
diff --git a/library/std/src/sys/pal/xous/mod.rs b/library/std/src/sys/pal/xous/mod.rs
index 9b22fb88c998d..b5b3fd91b4fa6 100644
--- a/library/std/src/sys/pal/xous/mod.rs
+++ b/library/std/src/sys/pal/xous/mod.rs
@@ -1,6 +1,5 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-pub mod os;
 pub mod params;
 
 #[path = "../unsupported/common.rs"]
diff --git a/library/std/src/sys/pal/xous/os.rs b/library/std/src/sys/pal/xous/os.rs
deleted file mode 100644
index fe8addeafd2bc..0000000000000
--- a/library/std/src/sys/pal/xous/os.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-use super::unsupported;
-use crate::ffi::{OsStr, OsString};
-use crate::marker::PhantomData;
-use crate::path::{self, PathBuf};
-use crate::{fmt, io};
-
-pub fn getcwd() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn chdir(_: &path::Path) -> io::Result<()> {
-    unsupported()
-}
-
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on this platform yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
-pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem on this platform")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
-}
diff --git a/library/std/src/sys/pal/zkvm/mod.rs b/library/std/src/sys/pal/zkvm/mod.rs
index 1b18adb811d95..1a64d3c93d701 100644
--- a/library/std/src/sys/pal/zkvm/mod.rs
+++ b/library/std/src/sys/pal/zkvm/mod.rs
@@ -11,7 +11,6 @@
 pub const WORD_SIZE: usize = size_of::<u32>();
 
 pub mod abi;
-pub mod os;
 
 use crate::io as std_io;
 
diff --git a/library/std/src/sys/paths/hermit.rs b/library/std/src/sys/paths/hermit.rs
new file mode 100644
index 0000000000000..36f667d300539
--- /dev/null
+++ b/library/std/src/sys/paths/hermit.rs
@@ -0,0 +1,10 @@
+use crate::io;
+use crate::path::PathBuf;
+
+pub fn getcwd() -> io::Result<PathBuf> {
+    Ok(PathBuf::from("/"))
+}
+
+pub fn temp_dir() -> PathBuf {
+    PathBuf::from("/tmp")
+}
diff --git a/library/std/src/sys/paths/mod.rs b/library/std/src/sys/paths/mod.rs
new file mode 100644
index 0000000000000..8880a837af7f9
--- /dev/null
+++ b/library/std/src/sys/paths/mod.rs
@@ -0,0 +1,59 @@
+cfg_select! {
+    target_os = "hermit" => {
+        mod hermit;
+        #[expect(dead_code)]
+        mod unsupported;
+        mod imp {
+            pub use super::hermit::{getcwd, temp_dir};
+            pub use super::unsupported::{chdir, SplitPaths, split_paths, JoinPathsError, join_paths, current_exe, home_dir};
+        }
+    }
+    target_os = "motor" => {
+        mod motor;
+        #[expect(dead_code)]
+        mod unsupported;
+        mod imp {
+            pub use super::motor::{getcwd, chdir, current_exe, temp_dir};
+            pub use super::unsupported::{SplitPaths, split_paths, JoinPathsError, join_paths, home_dir};
+        }
+    }
+    all(target_vendor = "fortanix", target_env = "sgx") => {
+        mod sgx;
+        #[expect(dead_code)]
+        mod unsupported;
+        mod imp {
+            pub use super::sgx::chdir;
+            pub use super::unsupported::{getcwd, SplitPaths, split_paths, JoinPathsError, join_paths, current_exe, temp_dir, home_dir};
+        }
+    }
+    target_os = "uefi" => {
+        mod uefi;
+        use uefi as imp;
+    }
+    target_family = "unix" => {
+        mod unix;
+        use unix as imp;
+    }
+    target_os = "wasi" => {
+        mod wasi;
+        #[expect(dead_code)]
+        mod unsupported;
+        mod imp {
+            pub use super::wasi::{getcwd, chdir, temp_dir};
+            pub use super::unsupported::{current_exe, SplitPaths, split_paths, JoinPathsError, join_paths, home_dir};
+        }
+    }
+    target_os = "windows" => {
+        mod windows;
+        use windows as imp;
+    }
+    _ => {
+        mod unsupported;
+        use unsupported as imp;
+    }
+}
+
+pub use imp::{
+    JoinPathsError, SplitPaths, chdir, current_exe, getcwd, home_dir, join_paths, split_paths,
+    temp_dir,
+};
diff --git a/library/std/src/sys/paths/motor.rs b/library/std/src/sys/paths/motor.rs
new file mode 100644
index 0000000000000..33d746b13d592
--- /dev/null
+++ b/library/std/src/sys/paths/motor.rs
@@ -0,0 +1,20 @@
+use crate::io;
+use crate::os::motor::ffi::OsStrExt;
+use crate::path::{self, PathBuf};
+use crate::sys::pal::map_motor_error;
+
+pub fn getcwd() -> io::Result<PathBuf> {
+    moto_rt::fs::getcwd().map(PathBuf::from).map_err(map_motor_error)
+}
+
+pub fn chdir(path: &path::Path) -> io::Result<()> {
+    moto_rt::fs::chdir(path.as_os_str().as_str()).map_err(map_motor_error)
+}
+
+pub fn current_exe() -> io::Result<PathBuf> {
+    moto_rt::process::current_exe().map(PathBuf::from).map_err(map_motor_error)
+}
+
+pub fn temp_dir() -> PathBuf {
+    PathBuf::from(moto_rt::fs::TEMP_DIR)
+}
diff --git a/library/std/src/sys/paths/sgx.rs b/library/std/src/sys/paths/sgx.rs
new file mode 100644
index 0000000000000..6a4cbe93b1b88
--- /dev/null
+++ b/library/std/src/sys/paths/sgx.rs
@@ -0,0 +1,7 @@
+use crate::io;
+use crate::path::Path;
+use crate::sys::pal::sgx_ineffective;
+
+pub fn chdir(_: &Path) -> io::Result<()> {
+    sgx_ineffective(())
+}
diff --git a/library/std/src/sys/pal/uefi/os.rs b/library/std/src/sys/paths/uefi.rs
similarity index 96%
rename from library/std/src/sys/pal/uefi/os.rs
rename to library/std/src/sys/paths/uefi.rs
index b25be430a3f83..7fddcfdff7724 100644
--- a/library/std/src/sys/pal/uefi/os.rs
+++ b/library/std/src/sys/paths/uefi.rs
@@ -1,9 +1,9 @@
 use r_efi::efi::protocols::{device_path, loaded_image_device_path};
 
-use super::{helpers, unsupported_err};
 use crate::ffi::{OsStr, OsString};
 use crate::os::uefi::ffi::{OsStrExt, OsStringExt};
 use crate::path::{self, PathBuf};
+use crate::sys::pal::{helpers, unsupported_err};
 use crate::{fmt, io};
 
 const PATHS_SEP: u16 = b';' as u16;
@@ -115,7 +115,7 @@ pub fn current_exe() -> io::Result<PathBuf> {
 }
 
 pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem on this platform")
+    panic!("UEFI doesn't have a dedicated temp directory")
 }
 
 pub fn home_dir() -> Option<PathBuf> {
diff --git a/library/std/src/sys/pal/unix/os.rs b/library/std/src/sys/paths/unix.rs
similarity index 99%
rename from library/std/src/sys/pal/unix/os.rs
rename to library/std/src/sys/paths/unix.rs
index f69614c2077cd..544d495340db7 100644
--- a/library/std/src/sys/pal/unix/os.rs
+++ b/library/std/src/sys/paths/unix.rs
@@ -7,8 +7,8 @@ use libc::{c_char, c_int, c_void};
 use crate::ffi::{CStr, OsStr, OsString};
 use crate::os::unix::prelude::*;
 use crate::path::{self, PathBuf};
-use crate::sys::cvt;
 use crate::sys::helpers::run_path_with_cstr;
+use crate::sys::pal::cvt;
 use crate::{fmt, io, iter, mem, ptr, slice, str};
 
 const PATH_SEPARATOR: u8 = b':';
@@ -47,7 +47,7 @@ pub fn getcwd() -> io::Result<PathBuf> {
 
 #[cfg(target_os = "espidf")]
 pub fn chdir(_p: &path::Path) -> io::Result<()> {
-    super::unsupported::unsupported()
+    crate::sys::pal::unsupported::unsupported()
 }
 
 #[cfg(not(target_os = "espidf"))]
@@ -372,7 +372,7 @@ pub fn current_exe() -> io::Result<PathBuf> {
 
 #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "vita"))]
 pub fn current_exe() -> io::Result<PathBuf> {
-    super::unsupported::unsupported()
+    crate::sys::pal::unsupported::unsupported()
 }
 
 #[cfg(target_os = "fuchsia")]
diff --git a/library/std/src/sys/pal/zkvm/os.rs b/library/std/src/sys/paths/unsupported.rs
similarity index 97%
rename from library/std/src/sys/pal/zkvm/os.rs
rename to library/std/src/sys/paths/unsupported.rs
index fe8addeafd2bc..024830a254fd7 100644
--- a/library/std/src/sys/pal/zkvm/os.rs
+++ b/library/std/src/sys/paths/unsupported.rs
@@ -1,7 +1,7 @@
-use super::unsupported;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
+use crate::sys::pal::unsupported;
 use crate::{fmt, io};
 
 pub fn getcwd() -> io::Result<PathBuf> {
diff --git a/library/std/src/sys/pal/wasi/os.rs b/library/std/src/sys/paths/wasi.rs
similarity index 59%
rename from library/std/src/sys/pal/wasi/os.rs
rename to library/std/src/sys/paths/wasi.rs
index b1c26acc68cb9..1e1f951cd6793 100644
--- a/library/std/src/sys/pal/wasi/os.rs
+++ b/library/std/src/sys/paths/wasi.rs
@@ -1,12 +1,10 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-use crate::ffi::{CStr, OsStr, OsString};
-use crate::marker::PhantomData;
+use crate::ffi::{CStr, OsString};
+use crate::io;
 use crate::os::wasi::prelude::*;
 use crate::path::{self, PathBuf};
 use crate::sys::helpers::run_path_with_cstr;
-use crate::sys::unsupported;
-use crate::{fmt, io};
 
 pub fn getcwd() -> io::Result<PathBuf> {
     let mut buf = Vec::with_capacity(512);
@@ -42,46 +40,6 @@ pub fn chdir(p: &path::Path) -> io::Result<()> {
     }
 }
 
-pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
-
-pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
-    panic!("unsupported")
-}
-
-impl<'a> Iterator for SplitPaths<'a> {
-    type Item = PathBuf;
-    fn next(&mut self) -> Option<PathBuf> {
-        self.0
-    }
-}
-
-#[derive(Debug)]
-pub struct JoinPathsError;
-
-pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
-where
-    I: Iterator<Item = T>,
-    T: AsRef<OsStr>,
-{
-    Err(JoinPathsError)
-}
-
-impl fmt::Display for JoinPathsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        "not supported on wasm yet".fmt(f)
-    }
-}
-
-impl crate::error::Error for JoinPathsError {}
-
-pub fn current_exe() -> io::Result<PathBuf> {
-    unsupported()
-}
-
 pub fn temp_dir() -> PathBuf {
-    panic!("no filesystem on wasm")
-}
-
-pub fn home_dir() -> Option<PathBuf> {
-    None
+    panic!("not supported by WASI yet")
 }
diff --git a/library/std/src/sys/pal/windows/os.rs b/library/std/src/sys/paths/windows.rs
similarity index 87%
rename from library/std/src/sys/pal/windows/os.rs
rename to library/std/src/sys/paths/windows.rs
index 30cad2a05683c..cfdc93847a97a 100644
--- a/library/std/src/sys/pal/windows/os.rs
+++ b/library/std/src/sys/paths/windows.rs
@@ -2,17 +2,13 @@
 
 #![allow(nonstandard_style)]
 
-#[cfg(test)]
-mod tests;
-
-use super::api;
-#[cfg(not(target_vendor = "uwp"))]
-use super::api::WinError;
 use crate::ffi::{OsStr, OsString};
 use crate::os::windows::ffi::EncodeWide;
 use crate::os::windows::prelude::*;
 use crate::path::{self, PathBuf};
-use crate::sys::pal::{c, cvt};
+#[cfg(not(target_vendor = "uwp"))]
+use crate::sys::pal::api::WinError;
+use crate::sys::pal::{api, c, cvt, fill_utf16_buf, os2path};
 use crate::{fmt, io, ptr};
 
 pub struct SplitPaths<'a> {
@@ -56,11 +52,7 @@ impl<'a> Iterator for SplitPaths<'a> {
             }
         }
 
-        if !must_yield && in_progress.is_empty() {
-            None
-        } else {
-            Some(super::os2path(&in_progress))
-        }
+        if !must_yield && in_progress.is_empty() { None } else { Some(os2path(&in_progress)) }
     }
 }
 
@@ -104,14 +96,11 @@ impl fmt::Display for JoinPathsError {
 impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
-    super::fill_utf16_buf(
-        |buf, sz| unsafe { c::GetModuleFileNameW(ptr::null_mut(), buf, sz) },
-        super::os2path,
-    )
+    fill_utf16_buf(|buf, sz| unsafe { c::GetModuleFileNameW(ptr::null_mut(), buf, sz) }, os2path)
 }
 
 pub fn getcwd() -> io::Result<PathBuf> {
-    super::fill_utf16_buf(|buf, sz| unsafe { c::GetCurrentDirectoryW(sz, buf) }, super::os2path)
+    fill_utf16_buf(|buf, sz| unsafe { c::GetCurrentDirectoryW(sz, buf) }, os2path)
 }
 
 pub fn chdir(p: &path::Path) -> io::Result<()> {
@@ -123,7 +112,7 @@ pub fn chdir(p: &path::Path) -> io::Result<()> {
 }
 
 pub fn temp_dir() -> PathBuf {
-    super::fill_utf16_buf(|buf, sz| unsafe { c::GetTempPath2W(sz, buf) }, super::os2path).unwrap()
+    fill_utf16_buf(|buf, sz| unsafe { c::GetTempPath2W(sz, buf) }, os2path).unwrap()
 }
 
 #[cfg(all(not(target_vendor = "uwp"), not(target_vendor = "win7")))]
@@ -132,7 +121,7 @@ fn home_dir_crt() -> Option<PathBuf> {
         // Defined in processthreadsapi.h.
         const CURRENT_PROCESS_TOKEN: usize = -4_isize as usize;
 
-        super::fill_utf16_buf(
+        fill_utf16_buf(
             |buf, mut sz| {
                 // GetUserProfileDirectoryW does not quite use the usual protocol for
                 // negotiating the buffer size, so we have to translate.
@@ -146,7 +135,7 @@ fn home_dir_crt() -> Option<PathBuf> {
                     _ => sz - 1, // sz includes the null terminator
                 }
             },
-            super::os2path,
+            os2path,
         )
         .ok()
     }
@@ -163,7 +152,7 @@ fn home_dir_crt() -> Option<PathBuf> {
             return None;
         }
         let _handle = Handle::from_raw_handle(token);
-        super::fill_utf16_buf(
+        fill_utf16_buf(
             |buf, mut sz| {
                 match c::GetUserProfileDirectoryW(token, buf, &mut sz) {
                     0 if api::get_last_error() != WinError::INSUFFICIENT_BUFFER => 0,
@@ -171,7 +160,7 @@ fn home_dir_crt() -> Option<PathBuf> {
                     _ => sz - 1, // sz includes the null terminator
                 }
             },
-            super::os2path,
+            os2path,
         )
         .ok()
     }
diff --git a/library/stdarch/crates/core_arch/src/mips/msa.rs b/library/stdarch/crates/core_arch/src/mips/msa.rs
index 563e121a7badb..6246433da5585 100644
--- a/library/stdarch/crates/core_arch/src/mips/msa.rs
+++ b/library/stdarch/crates/core_arch/src/mips/msa.rs
@@ -9187,7 +9187,6 @@ mod tests {
         core_arch::{mips::msa::*, simd::*},
         mem,
     };
-    use std::{f32, f64};
     use stdarch_test::simd_test;
 
     #[simd_test(enable = "msa")]
diff --git a/src/tools/rustfmt/src/vertical.rs b/src/tools/rustfmt/src/vertical.rs
index 21e34d29710fb..fd9a4a7db6a78 100644
--- a/src/tools/rustfmt/src/vertical.rs
+++ b/src/tools/rustfmt/src/vertical.rs
@@ -198,7 +198,7 @@ fn struct_field_prefix_max_min_width<T: AlignedItem>(
                 .rewrite_prefix(context, shape)
                 .map(|field_str| trimmed_last_line_width(&field_str))
         })
-        .fold_ok((0, ::std::usize::MAX), |(max_len, min_len), len| {
+        .fold_ok((0, usize::MAX), |(max_len, min_len), len| {
             (cmp::max(max_len, len), cmp::min(min_len, len))
         })
         .unwrap_or((0, 0))
diff --git a/tests/run-make/compressed-debuginfo/rmake.rs b/tests/run-make/compressed-debuginfo/rmake.rs
index 5ba1a1852d51b..c8bde9cfa221f 100644
--- a/tests/run-make/compressed-debuginfo/rmake.rs
+++ b/tests/run-make/compressed-debuginfo/rmake.rs
@@ -23,7 +23,7 @@ fn check_compression(compression: &str, to_find: &str) {
         } else {
             assert_contains(
                 stderr,
-                format!("unknown debuginfo compression algorithm {compression}"),
+                format!("unsupported debuginfo compression algorithm {compression}"),
             );
         }
     });
diff --git a/tests/ui/consts/issue-90762.rs b/tests/ui/consts/issue-90762.rs
index db40e50d4995f..cc060366b80bf 100644
--- a/tests/ui/consts/issue-90762.rs
+++ b/tests/ui/consts/issue-90762.rs
@@ -27,5 +27,5 @@ fn main() {
     for (i, b) in FOO.iter().enumerate() {
         assert!(b.load(Ordering::Relaxed), "{} not set", i);
     }
-    assert_eq!(BAR.fetch_add(1, Ordering::Relaxed), usize::max_value());
+    assert_eq!(BAR.fetch_add(1, Ordering::Relaxed), usize::MAX);
 }
diff --git a/tests/ui/issues/issue-44056.rs b/tests/ui/lto/lto-avx-target-feature.rs
similarity index 72%
rename from tests/ui/issues/issue-44056.rs
rename to tests/ui/lto/lto-avx-target-feature.rs
index 37d7b00cf7f0e..37a8ce67dcfcf 100644
--- a/tests/ui/issues/issue-44056.rs
+++ b/tests/ui/lto/lto-avx-target-feature.rs
@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/44056>
 //@ build-pass (FIXME(55996): should be run on targets supporting avx)
 //@ only-x86_64
 //@ no-prefer-dynamic
diff --git a/tests/ui/issues/issue-51947.rs b/tests/ui/lto/lto-weak-merge-functions.rs
similarity index 82%
rename from tests/ui/issues/issue-51947.rs
rename to tests/ui/lto/lto-weak-merge-functions.rs
index eda48aa5cf47a..bf16fbc834354 100644
--- a/tests/ui/issues/issue-51947.rs
+++ b/tests/ui/lto/lto-weak-merge-functions.rs
@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/51947>
 //@ build-pass
 
 #![crate_type = "lib"]