From dcb20d7b6274c8e8f8088ef73cba138f529354f6 Mon Sep 17 00:00:00 2001
From: Daniel Bloom <daniel@wormholelabs.xyz>
Date: Sun, 13 Apr 2025 22:17:26 -0700
Subject: [PATCH 01/25] Add support for $crate to Ident

---
 proc_macro/src/bridge/symbol.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/proc_macro/src/bridge/symbol.rs b/proc_macro/src/bridge/symbol.rs
index 6a1cecd69fb5f..57ca7db9fcdd7 100644
--- a/proc_macro/src/bridge/symbol.rs
+++ b/proc_macro/src/bridge/symbol.rs
@@ -33,7 +33,7 @@ impl Symbol {
     /// Validates and normalizes before converting it to a symbol.
     pub(crate) fn new_ident(string: &str, is_raw: bool) -> Self {
         // Fast-path: check if this is a valid ASCII identifier
-        if Self::is_valid_ascii_ident(string.as_bytes()) {
+        if Self::is_valid_ascii_ident(string.as_bytes()) || string == "$crate" {
             if is_raw && !Self::can_be_raw(string) {
                 panic!("`{}` cannot be a raw identifier", string);
             }
@@ -79,7 +79,7 @@ impl Symbol {
     // Mimics the behavior of `Symbol::can_be_raw` from `rustc_span`
     fn can_be_raw(string: &str) -> bool {
         match string {
-            "_" | "super" | "self" | "Self" | "crate" => false,
+            "_" | "super" | "self" | "Self" | "crate" | "$crate" => false,
             _ => true,
         }
     }

From 22e1c2ac9ebe04ce5d4192362c1563a457cb7030 Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Sat, 14 Jun 2025 12:08:25 +0200
Subject: [PATCH 02/25] use `is_multiple_of` to check if an addr is aligned

---
 compiler-builtins/compiler-builtins/src/arm.rs | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/compiler-builtins/compiler-builtins/src/arm.rs b/compiler-builtins/compiler-builtins/src/arm.rs
index a7d84e49b3493..617cc8e507bd8 100644
--- a/compiler-builtins/compiler-builtins/src/arm.rs
+++ b/compiler-builtins/compiler-builtins/src/arm.rs
@@ -135,8 +135,8 @@ intrinsics! {
     /// eight bytes.
     #[cfg(not(target_vendor = "apple"))]
     pub unsafe extern "aapcs" fn __aeabi_memcpy8(dst: *mut u8, src: *const u8, n: usize) {
-        debug_assert!(dst.addr() & 7 == 0);
-        debug_assert!(src.addr() & 7 == 0);
+        debug_assert!(dst.addr().is_multiple_of(8));
+        debug_assert!(src.addr().is_multiple_of(8));
 
         // SAFETY: memcpy preconditions apply, less strict alignment.
         unsafe { __aeabi_memcpy4(dst, src, n) };
@@ -161,8 +161,8 @@ intrinsics! {
     /// four bytes.
     #[cfg(not(any(target_vendor = "apple", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memmove4(dst: *mut u8, src: *const u8, n: usize) {
-        debug_assert!(dst.addr() & 3 == 0);
-        debug_assert!(src.addr() & 3 == 0);
+        debug_assert!(dst.addr().is_multiple_of(4));
+        debug_assert!(src.addr().is_multiple_of(4));
 
         // SAFETY: same preconditions, less strict aligment.
         unsafe { __aeabi_memmove(dst, src, n) };
@@ -176,8 +176,8 @@ intrinsics! {
     /// eight bytes.
     #[cfg(not(any(target_vendor = "apple", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memmove8(dst: *mut u8, src: *const u8, n: usize) {
-        debug_assert!(dst.addr() & 7 == 0);
-        debug_assert!(src.addr() & 7 == 0);
+        debug_assert!(dst.addr().is_multiple_of(8));
+        debug_assert!(src.addr().is_multiple_of(8));
 
         // SAFETY: memmove preconditions apply, less strict alignment.
         unsafe { __aeabi_memmove(dst, src, n) };
@@ -236,7 +236,7 @@ intrinsics! {
     /// eight bytes.
     #[cfg(not(target_vendor = "apple"))]
     pub unsafe extern "aapcs" fn __aeabi_memset8(dst: *mut u8, n: usize, c: i32) {
-        debug_assert!(dst.addr() & 7 == 0);
+        debug_assert!(dst.addr().is_multiple_of(8));
 
         // SAFETY: memset preconditions apply, less strict alignment.
         unsafe { __aeabi_memset4(dst, n, c) };
@@ -261,7 +261,7 @@ intrinsics! {
     /// four bytes.
     #[cfg(not(any(target_vendor = "apple", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memclr4(dst: *mut u8, n: usize) {
-        debug_assert!(dst.addr() & 3 == 0);
+        debug_assert!(dst.addr().is_multiple_of(4));
 
         // SAFETY: memclr preconditions apply, less strict alignment.
         unsafe { __aeabi_memset4(dst, n, 0) };
@@ -275,7 +275,7 @@ intrinsics! {
     /// eight bytes.
     #[cfg(not(any(target_vendor = "apple", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memclr8(dst: *mut u8, n: usize) {
-        debug_assert!(dst.addr() & 7 == 0);
+        debug_assert!(dst.addr().is_multiple_of(8));
 
         // SAFETY: memclr preconditions apply, less strict alignment.
         unsafe { __aeabi_memset4(dst, n, 0) };

From cdb59e3442d88cf5110562bb79a30df751735e36 Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Sat, 14 Jun 2025 20:17:23 +0200
Subject: [PATCH 03/25] use `extern "custom"` on naked functions with a custom
 calling convention

---
 .../compiler-builtins/src/aarch64.rs              |  2 +-
 compiler-builtins/compiler-builtins/src/arm.rs    | 13 ++++++-------
 .../compiler-builtins/src/int/udiv.rs             |  2 +-
 compiler-builtins/compiler-builtins/src/lib.rs    |  1 +
 .../compiler-builtins/src/probestack.rs           | 15 +++------------
 compiler-builtins/compiler-builtins/src/x86.rs    | 10 +++++-----
 compiler-builtins/compiler-builtins/src/x86_64.rs |  4 ++--
 7 files changed, 19 insertions(+), 28 deletions(-)

diff --git a/compiler-builtins/compiler-builtins/src/aarch64.rs b/compiler-builtins/compiler-builtins/src/aarch64.rs
index 80392187c89b4..a72b30d29f0ba 100644
--- a/compiler-builtins/compiler-builtins/src/aarch64.rs
+++ b/compiler-builtins/compiler-builtins/src/aarch64.rs
@@ -5,7 +5,7 @@ use core::intrinsics;
 intrinsics! {
     #[unsafe(naked)]
     #[cfg(all(target_os = "uefi", not(feature = "no-asm")))]
-    pub unsafe extern "C" fn __chkstk() {
+    pub unsafe extern "custom" fn __chkstk() {
         core::arch::naked_asm!(
             ".p2align 2",
             "lsl    x16, x15, #4",
diff --git a/compiler-builtins/compiler-builtins/src/arm.rs b/compiler-builtins/compiler-builtins/src/arm.rs
index 617cc8e507bd8..fbec93ca4312e 100644
--- a/compiler-builtins/compiler-builtins/src/arm.rs
+++ b/compiler-builtins/compiler-builtins/src/arm.rs
@@ -9,11 +9,10 @@ unsafe extern "C" {
 }
 
 // SAFETY: these are defined in compiler-builtins
-// FIXME(extern_custom), this isn't always the correct ABI
-unsafe extern "aapcs" {
+unsafe extern "custom" {
     // AAPCS is not always the correct ABI for these intrinsics, but we only use this to
     // forward another `__aeabi_` call so it doesn't matter.
-    fn __aeabi_idiv(a: i32, b: i32) -> i32;
+    fn __aeabi_idiv();
 }
 
 intrinsics! {
@@ -21,7 +20,7 @@ intrinsics! {
     // custom calling convention which can't be implemented using a normal Rust function.
     #[unsafe(naked)]
     #[cfg(not(target_env = "msvc"))]
-    pub unsafe extern "C" fn __aeabi_uidivmod() {
+    pub unsafe extern "custom" fn __aeabi_uidivmod() {
         core::arch::naked_asm!(
             "push {{lr}}",
             "sub sp, sp, #4",
@@ -35,7 +34,7 @@ intrinsics! {
     }
 
     #[unsafe(naked)]
-    pub unsafe extern "C" fn __aeabi_uldivmod() {
+    pub unsafe extern "custom" fn __aeabi_uldivmod() {
         core::arch::naked_asm!(
             "push {{r4, lr}}",
             "sub sp, sp, #16",
@@ -51,7 +50,7 @@ intrinsics! {
     }
 
     #[unsafe(naked)]
-    pub unsafe extern "C" fn __aeabi_idivmod() {
+    pub unsafe extern "custom" fn __aeabi_idivmod() {
         core::arch::naked_asm!(
             "push {{r0, r1, r4, lr}}",
             "bl {trampoline}",
@@ -64,7 +63,7 @@ intrinsics! {
     }
 
     #[unsafe(naked)]
-    pub unsafe extern "C" fn __aeabi_ldivmod() {
+    pub unsafe extern "custom" fn __aeabi_ldivmod() {
         core::arch::naked_asm!(
             "push {{r4, lr}}",
             "sub sp, sp, #16",
diff --git a/compiler-builtins/compiler-builtins/src/int/udiv.rs b/compiler-builtins/compiler-builtins/src/int/udiv.rs
index b9dee63c4cc7a..017a81ac91490 100644
--- a/compiler-builtins/compiler-builtins/src/int/udiv.rs
+++ b/compiler-builtins/compiler-builtins/src/int/udiv.rs
@@ -44,7 +44,7 @@ intrinsics! {
     }
 
     #[unsafe(naked)]
-    pub unsafe extern "C" fn __udivmodqi4() {
+    pub unsafe extern "custom" fn __udivmodqi4() {
         // compute unsigned 8-bit `n / d` and `n % d`.
         //
         // Note: GCC implements a [non-standard calling convention](https://gcc.gnu.org/wiki/avr-gcc#Exceptions_to_the_Calling_Convention) for this function.
diff --git a/compiler-builtins/compiler-builtins/src/lib.rs b/compiler-builtins/compiler-builtins/src/lib.rs
index 1cec39d8b41bb..dd9920cae015f 100644
--- a/compiler-builtins/compiler-builtins/src/lib.rs
+++ b/compiler-builtins/compiler-builtins/src/lib.rs
@@ -1,5 +1,6 @@
 #![cfg_attr(feature = "compiler-builtins", compiler_builtins)]
 #![cfg_attr(all(target_family = "wasm"), feature(wasm_numeric_instr))]
+#![feature(abi_custom)]
 #![feature(abi_unadjusted)]
 #![feature(asm_experimental_arch)]
 #![feature(cfg_target_has_atomic)]
diff --git a/compiler-builtins/compiler-builtins/src/probestack.rs b/compiler-builtins/compiler-builtins/src/probestack.rs
index 1441fd73b8d6f..1d0010842cba1 100644
--- a/compiler-builtins/compiler-builtins/src/probestack.rs
+++ b/compiler-builtins/compiler-builtins/src/probestack.rs
@@ -52,15 +52,12 @@
 // Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
 // ensuring that if any pages are unmapped we'll make a page fault.
 //
-// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
-// it does not actually match `extern "C"`.
-//
 // The ABI here is that the stack frame size is located in `%rax`. Upon
 // return we're not supposed to modify `%rsp` or `%rax`.
 #[cfg(target_arch = "x86_64")]
 #[unsafe(naked)]
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_probestack() {
+pub unsafe extern "custom" fn __rust_probestack() {
     #[cfg(not(all(target_env = "sgx", target_vendor = "fortanix")))]
     macro_rules! ret {
         () => {
@@ -144,13 +141,10 @@ pub unsafe extern "C" fn __rust_probestack() {
 // that on Unix we're expected to restore everything as it was, this
 // function basically can't tamper with anything.
 //
-// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
-// it does not actually match `extern "C"`.
-//
 // The ABI here is the same as x86_64, except everything is 32-bits large.
 #[unsafe(naked)]
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_probestack() {
+pub unsafe extern "custom" fn __rust_probestack() {
     core::arch::naked_asm!(
         "
             .cfi_startproc
@@ -192,9 +186,6 @@ pub unsafe extern "C" fn __rust_probestack() {
 // probestack function will also do things like _chkstk in MSVC.
 // So we need to sub %ax %sp in probestack when arch is x86.
 //
-// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
-// it does not actually match `extern "C"`.
-//
 // REF: Rust commit(74e80468347)
 // rust\src\llvm-project\llvm\lib\Target\X86\X86FrameLowering.cpp: 805
 // Comments in LLVM:
@@ -203,7 +194,7 @@ pub unsafe extern "C" fn __rust_probestack() {
 //   themselves.
 #[unsafe(naked)]
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_probestack() {
+pub unsafe extern "custom" fn __rust_probestack() {
     core::arch::naked_asm!(
         "
             .cfi_startproc
diff --git a/compiler-builtins/compiler-builtins/src/x86.rs b/compiler-builtins/compiler-builtins/src/x86.rs
index 01152d9c79869..16e50922a9454 100644
--- a/compiler-builtins/compiler-builtins/src/x86.rs
+++ b/compiler-builtins/compiler-builtins/src/x86.rs
@@ -2,7 +2,7 @@
 
 use core::intrinsics;
 
-// NOTE These functions are implemented using assembly because they using a custom
+// NOTE These functions are implemented using assembly because they use a custom
 // calling convention which can't be implemented using a normal Rust function
 
 // NOTE These functions are never mangled as they are not tested against compiler-rt
@@ -13,10 +13,10 @@ intrinsics! {
         any(all(windows, target_env = "gnu"), target_os = "uefi"),
         not(feature = "no-asm")
     ))]
-    pub unsafe extern "C" fn __chkstk() {
+    pub unsafe extern "custom" fn __chkstk() {
         core::arch::naked_asm!(
-            "jmp __alloca", // Jump to __alloca since fallthrough may be unreliable"
-            options(att_syntax)
+            "jmp {}", // Jump to __alloca since fallthrough may be unreliable"
+            sym crate::x86::_alloca::_alloca,
         );
     }
 
@@ -25,7 +25,7 @@ intrinsics! {
         any(all(windows, target_env = "gnu"), target_os = "uefi"),
         not(feature = "no-asm")
     ))]
-    pub unsafe extern "C" fn _alloca() {
+    pub unsafe extern "custom" fn _alloca() {
         // __chkstk and _alloca are the same function
         core::arch::naked_asm!(
             "push   %ecx",
diff --git a/compiler-builtins/compiler-builtins/src/x86_64.rs b/compiler-builtins/compiler-builtins/src/x86_64.rs
index fc1190f79b237..9b7133b482e4e 100644
--- a/compiler-builtins/compiler-builtins/src/x86_64.rs
+++ b/compiler-builtins/compiler-builtins/src/x86_64.rs
@@ -2,7 +2,7 @@
 
 use core::intrinsics;
 
-// NOTE These functions are implemented using assembly because they using a custom
+// NOTE These functions are implemented using assembly because they use a custom
 // calling convention which can't be implemented using a normal Rust function
 
 // NOTE These functions are never mangled as they are not tested against compiler-rt
@@ -17,7 +17,7 @@ intrinsics! {
         ),
         not(feature = "no-asm")
     ))]
-    pub unsafe extern "C" fn ___chkstk_ms() {
+    pub unsafe extern "custom" fn ___chkstk_ms() {
         core::arch::naked_asm!(
             "push   %rcx",
             "push   %rax",

From 6160c941e4b8639c4f1b06481a23fd69a75255b6 Mon Sep 17 00:00:00 2001
From: Urgau <3616612+Urgau@users.noreply.github.com>
Date: Sun, 15 Jun 2025 00:43:17 +0200
Subject: [PATCH 04/25] Add minimal triagebot config

This PR adds a minimal `triagebot.toml` config to make contributions to
this repository respect upstream rust-lang/rust conventions and avoid
issues when syncing this subtree.
---
 compiler-builtins/triagebot.toml | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 compiler-builtins/triagebot.toml

diff --git a/compiler-builtins/triagebot.toml b/compiler-builtins/triagebot.toml
new file mode 100644
index 0000000000000..ecc05da019517
--- /dev/null
+++ b/compiler-builtins/triagebot.toml
@@ -0,0 +1,21 @@
+## See <https://forge.rust-lang.org/triagebot/index.html> for documentation
+## of these features.
+
+# Warns when a PR contains merge commits
+# Documentation at: https://forge.rust-lang.org/triagebot/no-merge.html
+[no-merges]
+exclude_titles = ["Update from"]
+
+# Canonicalize issue numbers to avoid closing the wrong issue
+# when commits are included in subtrees, as well as warning links in commits.
+# Documentation at: https://forge.rust-lang.org/triagebot/issue-links.html
+[issue-links]
+check-commits = false
+
+# Prevents mentions in commits to avoid users being spammed
+# Documentation at: https://forge.rust-lang.org/triagebot/no-mentions.html
+[no-mentions]
+
+# Enable issue transfers within the org
+# Documentation at: https://forge.rust-lang.org/triagebot/transfer.html
+[transfer]

From 4337073cf5acb38a90bbc64d6f278ebe1d22085e Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Sat, 14 Jun 2025 23:39:24 +0000
Subject: [PATCH 05/25] symcheck: Add a wrapper around an archive

Rather than re-opening the archive file for each check, add a wrapper
that keeps the data in memory. Additionally, collect the `--target`
argument so it can be used within this crate.
---
 .../crates/symbol-check/src/main.rs           | 104 ++++++++++++++----
 1 file changed, 80 insertions(+), 24 deletions(-)

diff --git a/compiler-builtins/crates/symbol-check/src/main.rs b/compiler-builtins/crates/symbol-check/src/main.rs
index d83cd318d6a95..843a943fb5f08 100644
--- a/compiler-builtins/crates/symbol-check/src/main.rs
+++ b/compiler-builtins/crates/symbol-check/src/main.rs
@@ -8,7 +8,9 @@ use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
 use object::read::archive::{ArchiveFile, ArchiveMember};
-use object::{Object, ObjectSymbol, Symbol, SymbolKind, SymbolScope, SymbolSection};
+use object::{
+    File as ObjFile, Object, ObjectSymbol, Symbol, SymbolKind, SymbolScope, SymbolSection,
+};
 use serde_json::Value;
 
 const CHECK_LIBRARIES: &[&str] = &["compiler_builtins", "builtins_test_intrinsics"];
@@ -28,13 +30,11 @@ fn main() {
     let args_ref = args.iter().map(String::as_str).collect::<Vec<_>>();
 
     match &args_ref[1..] {
-        ["build-and-check", rest @ ..] if !rest.is_empty() => {
-            let paths = exec_cargo_with_args(rest);
-            for path in paths {
-                println!("Checking {}", path.display());
-                verify_no_duplicates(&path);
-                verify_core_symbols(&path);
-            }
+        ["build-and-check", "--target", target, args @ ..] if !args.is_empty() => {
+            run_build_and_check(Some(target), args);
+        }
+        ["build-and-check", args @ ..] if !args.is_empty() => {
+            run_build_and_check(None, args);
         }
         _ => {
             println!("{USAGE}");
@@ -43,12 +43,42 @@ fn main() {
     }
 }
 
+fn run_build_and_check(target: Option<&str>, args: &[&str]) {
+    let paths = exec_cargo_with_args(target, args);
+    for path in paths {
+        println!("Checking {}", path.display());
+        let archive = Archive::from_path(&path);
+
+        verify_no_duplicates(&archive);
+        verify_core_symbols(&archive);
+    }
+}
+
+fn host_target() -> String {
+    let out = Command::new("rustc")
+        .arg("--version")
+        .arg("--verbose")
+        .output()
+        .unwrap();
+    assert!(out.status.success());
+    let out = String::from_utf8(out.stdout).unwrap();
+    out.lines()
+        .find_map(|s| s.strip_prefix("host: "))
+        .unwrap()
+        .to_owned()
+}
+
 /// Run `cargo build` with the provided additional arguments, collecting the list of created
 /// libraries.
-fn exec_cargo_with_args(args: &[&str]) -> Vec<PathBuf> {
+fn exec_cargo_with_args(target: Option<&str>, args: &[&str]) -> Vec<PathBuf> {
+    let mut host = String::new();
+    let target = target.unwrap_or_else(|| {
+        host = host_target();
+        host.as_str()
+    });
+
     let mut cmd = Command::new("cargo");
-    cmd.arg("build")
-        .arg("--message-format=json")
+    cmd.args(["build", "--target", target, "--message-format=json"])
         .args(args)
         .stdout(Stdio::piped());
 
@@ -133,12 +163,12 @@ impl SymInfo {
 /// Note that this will also locate cases where a symbol is weakly defined in more than one place.
 /// Technically there are no linker errors that will come from this, but it keeps our binary more
 /// straightforward and saves some distribution size.
-fn verify_no_duplicates(path: &Path) {
+fn verify_no_duplicates(archive: &Archive) {
     let mut syms = BTreeMap::<String, SymInfo>::new();
     let mut dups = Vec::new();
     let mut found_any = false;
 
-    for_each_symbol(path, |symbol, member| {
+    archive.for_each_symbol(|symbol, member| {
         // Only check defined globals
         if !symbol.is_global() || symbol.is_undefined() {
             return;
@@ -185,12 +215,12 @@ fn verify_no_duplicates(path: &Path) {
 }
 
 /// Ensure that there are no references to symbols from `core` that aren't also (somehow) defined.
-fn verify_core_symbols(path: &Path) {
+fn verify_core_symbols(archive: &Archive) {
     let mut defined = BTreeSet::new();
     let mut undefined = Vec::new();
     let mut has_symbols = false;
 
-    for_each_symbol(path, |symbol, member| {
+    archive.for_each_symbol(|symbol, member| {
         has_symbols = true;
 
         // Find only symbols from `core`
@@ -219,14 +249,40 @@ fn verify_core_symbols(path: &Path) {
     println!("    success: no undefined references to core found");
 }
 
-/// For a given archive path, do something with each symbol.
-fn for_each_symbol(path: &Path, mut f: impl FnMut(Symbol, &ArchiveMember)) {
-    let data = fs::read(path).expect("reading file failed");
-    let archive = ArchiveFile::parse(data.as_slice()).expect("archive parse failed");
-    for member in archive.members() {
-        let member = member.expect("failed to access member");
-        let obj_data = member.data(&*data).expect("failed to access object");
-        let obj = object::File::parse(obj_data).expect("failed to parse object");
-        obj.symbols().for_each(|sym| f(sym, &member));
+/// Thin wrapper for owning data used by `object`.
+struct Archive {
+    data: Vec<u8>,
+}
+
+impl Archive {
+    fn from_path(path: &Path) -> Self {
+        Self {
+            data: fs::read(path).expect("reading file failed"),
+        }
+    }
+
+    fn file(&self) -> ArchiveFile<'_> {
+        ArchiveFile::parse(self.data.as_slice()).expect("archive parse failed")
+    }
+
+    /// For a given archive, do something with each object file.
+    fn for_each_object(&self, mut f: impl FnMut(ObjFile, &ArchiveMember)) {
+        let archive = self.file();
+
+        for member in archive.members() {
+            let member = member.expect("failed to access member");
+            let obj_data = member
+                .data(self.data.as_slice())
+                .expect("failed to access object");
+            let obj = ObjFile::parse(obj_data).expect("failed to parse object");
+            f(obj, &member);
+        }
+    }
+
+    /// For a given archive, do something with each symbol.
+    fn for_each_symbol(&self, mut f: impl FnMut(Symbol, &ArchiveMember)) {
+        self.for_each_object(|obj, member| {
+            obj.symbols().for_each(|sym| f(sym, member));
+        });
     }
 }

From 8c27a34f376f143fa8762bc8784aa2b80d2d142c Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Tue, 24 Jun 2025 20:40:08 +0200
Subject: [PATCH 06/25] Use `asm_cfg` in `probestack`

cc https://www.github.com/rust-lang/rust/issues/140364
---
 .../compiler-builtins/src/lib.rs              |  1 +
 .../compiler-builtins/src/probestack.rs       | 35 +++++++------------
 2 files changed, 13 insertions(+), 23 deletions(-)

diff --git a/compiler-builtins/compiler-builtins/src/lib.rs b/compiler-builtins/compiler-builtins/src/lib.rs
index dd9920cae015f..fe0ad81dd3a3d 100644
--- a/compiler-builtins/compiler-builtins/src/lib.rs
+++ b/compiler-builtins/compiler-builtins/src/lib.rs
@@ -7,6 +7,7 @@
 #![feature(compiler_builtins)]
 #![feature(core_intrinsics)]
 #![feature(linkage)]
+#![feature(asm_cfg)]
 #![feature(naked_functions)]
 #![feature(repr_simd)]
 #![feature(macro_metavar_expr_concat)]
diff --git a/compiler-builtins/compiler-builtins/src/probestack.rs b/compiler-builtins/compiler-builtins/src/probestack.rs
index 1d0010842cba1..f4105dde57e66 100644
--- a/compiler-builtins/compiler-builtins/src/probestack.rs
+++ b/compiler-builtins/compiler-builtins/src/probestack.rs
@@ -58,27 +58,6 @@
 #[unsafe(naked)]
 #[rustc_std_internal_symbol]
 pub unsafe extern "custom" fn __rust_probestack() {
-    #[cfg(not(all(target_env = "sgx", target_vendor = "fortanix")))]
-    macro_rules! ret {
-        () => {
-            "ret"
-        };
-    }
-
-    #[cfg(all(target_env = "sgx", target_vendor = "fortanix"))]
-    macro_rules! ret {
-        // for this target, [manually patch for LVI].
-        //
-        // [manually patch for LVI]: https://software.intel.com/security-software-guidance/insights/deep-dive-load-value-injection#specialinstructions
-        () => {
-            "
-            pop %r11
-            lfence
-            jmp *%r11
-            "
-        };
-    }
-
     core::arch::naked_asm!(
         "
             .cfi_startproc
@@ -128,8 +107,18 @@ pub unsafe extern "custom" fn __rust_probestack() {
             .cfi_def_cfa_register %rsp
             .cfi_adjust_cfa_offset -8
     ",
-        ret!(),
-        "
+    #[cfg(not(all(target_env = "sgx", target_vendor = "fortanix")))]
+    "       ret",
+    #[cfg(all(target_env = "sgx", target_vendor = "fortanix"))]
+    "
+            // for this target, [manually patch for LVI].
+            //
+            // [manually patch for LVI]: https://software.intel.com/security-software-guidance/insights/deep-dive-load-value-injection#specialinstructions
+            pop %r11
+            lfence
+            jmp *%r11
+    ",
+    "
             .cfi_endproc
     ",
         options(att_syntax)

From e3fb5986b5fdbd5a59f7b0d117299a3f9c1196e8 Mon Sep 17 00:00:00 2001
From: quaternic <57393910+quaternic@users.noreply.github.com>
Date: Sun, 29 Jun 2025 06:53:07 +0300
Subject: [PATCH 07/25] apply suggestions for clippy::manual_is_multiple_of in
 libm-test

---
 compiler-builtins/libm-test/tests/z_extensive/run.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/compiler-builtins/libm-test/tests/z_extensive/run.rs b/compiler-builtins/libm-test/tests/z_extensive/run.rs
index f2ba6a4a0e3e6..e04e00c6d743a 100644
--- a/compiler-builtins/libm-test/tests/z_extensive/run.rs
+++ b/compiler-builtins/libm-test/tests/z_extensive/run.rs
@@ -197,15 +197,15 @@ impl Progress {
 
     fn update(&self, completed: u64, input: impl fmt::Debug) {
         // Infrequently update the progress bar.
-        if completed % 20_000 == 0 {
+        if completed.is_multiple_of(20_000) {
             self.pb.set_position(completed);
         }
 
-        if completed % 500_000 == 0 {
+        if completed.is_multiple_of(500_000) {
             self.pb.set_message(format!("input: {input:<24?}"));
         }
 
-        if !self.is_tty && completed % 5_000_000 == 0 {
+        if !self.is_tty && completed.is_multiple_of(5_000_000) {
             let len = self.pb.length().unwrap_or_default();
             eprintln!(
                 "[{elapsed:3?}s {percent:3.0}%] {name} \

From 9deadd6223598ff8be7ad2be59744c7f491ff6e9 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Sat, 14 Jun 2025 08:44:37 +0000
Subject: [PATCH 08/25] josh-sync: Replace `#xxxx`-style links in messages

Often our short summaries will pick up a Bors "Auto merge of #xxxx ...`
commit message. Replace these with something like `rust-lang/rust#1234`
to avoid broken links when going between repositories.
---
 compiler-builtins/crates/josh-sync/Cargo.toml |  1 +
 .../crates/josh-sync/src/sync.rs              | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/compiler-builtins/crates/josh-sync/Cargo.toml b/compiler-builtins/crates/josh-sync/Cargo.toml
index 1f3bb376d6d91..8e2e891db5426 100644
--- a/compiler-builtins/crates/josh-sync/Cargo.toml
+++ b/compiler-builtins/crates/josh-sync/Cargo.toml
@@ -5,3 +5,4 @@ publish = false
 
 [dependencies]
 directories = "6.0.0"
+regex-lite = "0.1.6"
diff --git a/compiler-builtins/crates/josh-sync/src/sync.rs b/compiler-builtins/crates/josh-sync/src/sync.rs
index 003cf187d8301..2d89d2d1cea2f 100644
--- a/compiler-builtins/crates/josh-sync/src/sync.rs
+++ b/compiler-builtins/crates/josh-sync/src/sync.rs
@@ -1,8 +1,11 @@
+use std::borrow::Cow;
 use std::net::{SocketAddr, TcpStream};
 use std::process::{Command, Stdio, exit};
 use std::time::Duration;
 use std::{env, fs, process, thread};
 
+use regex_lite::Regex;
+
 const JOSH_PORT: u16 = 42042;
 const DEFAULT_PR_BRANCH: &str = "update-builtins";
 
@@ -77,6 +80,7 @@ impl GitSync {
             "--depth=1",
         ]);
         let new_summary = check_output(["git", "log", "-1", "--format=%h %s", &new_upstream_base]);
+        let new_summary = replace_references(&new_summary, &self.upstream_repo);
 
         // Update rust-version file. As a separate commit, since making it part of
         // the merge has confused the heck out of josh in the past.
@@ -297,6 +301,13 @@ fn check_output_cfg(prog: &str, f: impl FnOnce(&mut Command) -> &mut Command) ->
     String::from_utf8(out.stdout.trim_ascii().to_vec()).expect("non-UTF8 output")
 }
 
+/// Replace `#1234`-style issue/PR references with `repo#1234` to ensure links work across
+/// repositories.
+fn replace_references<'a>(s: &'a str, repo: &str) -> Cow<'a, str> {
+    let re = Regex::new(r"\B(?P<id>#\d+)\b").unwrap();
+    re.replace(s, &format!("{repo}$id"))
+}
+
 /// Create a wrapper that stops Josh on drop.
 pub struct Josh(process::Child);
 
@@ -369,3 +380,22 @@ impl Drop for Josh {
         self.0.kill().expect("failed to SIGKILL josh-proxy");
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_replace() {
+        assert_eq!(replace_references("#1234", "r-l/rust"), "r-l/rust#1234");
+        assert_eq!(replace_references("#1234x", "r-l/rust"), "#1234x");
+        assert_eq!(
+            replace_references("merge #1234", "r-l/rust"),
+            "merge r-l/rust#1234"
+        );
+        assert_eq!(
+            replace_references("foo/bar#1234", "r-l/rust"),
+            "foo/bar#1234"
+        );
+    }
+}

From 5eabc591a777de04ae3281f454fc3aae5325f7a9 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Mon, 30 Jun 2025 18:58:43 -0700
Subject: [PATCH 09/25] Mention as_chunks in the docs for chunks

---
 core/src/slice/mod.rs | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/core/src/slice/mod.rs b/core/src/slice/mod.rs
index 3a3f44c6b8546..b472307871f6c 100644
--- a/core/src/slice/mod.rs
+++ b/core/src/slice/mod.rs
@@ -1120,6 +1120,9 @@ impl<T> [T] {
     /// `chunk_size` elements, and [`rchunks`] for the same iterator but starting at the end of the
     /// slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_chunks`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1137,6 +1140,7 @@ impl<T> [T] {
     ///
     /// [`chunks_exact`]: slice::chunks_exact
     /// [`rchunks`]: slice::rchunks
+    /// [`as_chunks`]: slice::as_chunks
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1156,6 +1160,9 @@ impl<T> [T] {
     /// exactly `chunk_size` elements, and [`rchunks_mut`] for the same iterator but starting at
     /// the end of the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_chunks_mut`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1177,6 +1184,7 @@ impl<T> [T] {
     ///
     /// [`chunks_exact_mut`]: slice::chunks_exact_mut
     /// [`rchunks_mut`]: slice::rchunks_mut
+    /// [`as_chunks_mut`]: slice::as_chunks_mut
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1199,6 +1207,9 @@ impl<T> [T] {
     /// See [`chunks`] for a variant of this iterator that also returns the remainder as a smaller
     /// chunk, and [`rchunks_exact`] for the same iterator but starting at the end of the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_chunks`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1216,6 +1227,7 @@ impl<T> [T] {
     ///
     /// [`chunks`]: slice::chunks
     /// [`rchunks_exact`]: slice::rchunks_exact
+    /// [`as_chunks`]: slice::chunks
     #[stable(feature = "chunks_exact", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1239,6 +1251,9 @@ impl<T> [T] {
     /// smaller chunk, and [`rchunks_exact_mut`] for the same iterator but starting at the end of
     /// the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_chunks_mut`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1260,6 +1275,7 @@ impl<T> [T] {
     ///
     /// [`chunks_mut`]: slice::chunks_mut
     /// [`rchunks_exact_mut`]: slice::rchunks_exact_mut
+    /// [`as_chunks_mut`]: slice::as_chunks_mut
     #[stable(feature = "chunks_exact", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1707,6 +1723,9 @@ impl<T> [T] {
     /// `chunk_size` elements, and [`chunks`] for the same iterator but starting at the beginning
     /// of the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_rchunks`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1724,6 +1743,7 @@ impl<T> [T] {
     ///
     /// [`rchunks_exact`]: slice::rchunks_exact
     /// [`chunks`]: slice::chunks
+    /// [`as_rchunks`]: slice::as_rchunks
     #[stable(feature = "rchunks", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1743,6 +1763,9 @@ impl<T> [T] {
     /// exactly `chunk_size` elements, and [`chunks_mut`] for the same iterator but starting at the
     /// beginning of the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_rchunks_mut`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1764,6 +1787,7 @@ impl<T> [T] {
     ///
     /// [`rchunks_exact_mut`]: slice::rchunks_exact_mut
     /// [`chunks_mut`]: slice::chunks_mut
+    /// [`as_rchunks_mut`]: slice::as_rchunks_mut
     #[stable(feature = "rchunks", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1787,6 +1811,9 @@ impl<T> [T] {
     /// chunk, and [`chunks_exact`] for the same iterator but starting at the beginning of the
     /// slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_rchunks`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1805,6 +1832,7 @@ impl<T> [T] {
     /// [`chunks`]: slice::chunks
     /// [`rchunks`]: slice::rchunks
     /// [`chunks_exact`]: slice::chunks_exact
+    /// [`as_rchunks`]: slice::as_rchunks
     #[stable(feature = "rchunks", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]
@@ -1828,6 +1856,9 @@ impl<T> [T] {
     /// smaller chunk, and [`chunks_exact_mut`] for the same iterator but starting at the beginning
     /// of the slice.
     ///
+    /// If your `chunk_size` is a constant, consider using [`as_rchunks_mut`] instead, which will
+    /// give references to arrays of exactly that length, rather than slices.
+    ///
     /// # Panics
     ///
     /// Panics if `chunk_size` is zero.
@@ -1850,6 +1881,7 @@ impl<T> [T] {
     /// [`chunks_mut`]: slice::chunks_mut
     /// [`rchunks_mut`]: slice::rchunks_mut
     /// [`chunks_exact_mut`]: slice::chunks_exact_mut
+    /// [`as_rchunks_mut`]: slice::as_rchunks_mut
     #[stable(feature = "rchunks", since = "1.31.0")]
     #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
     #[inline]

From b31092dfea71f8b763802a99b821cd077b38e676 Mon Sep 17 00:00:00 2001
From: quaternic <57393910+quaternic@users.noreply.github.com>
Date: Tue, 1 Jul 2025 11:07:48 +0300
Subject: [PATCH 10/25] libm: Improved integer utilities, implement shifts and
 bug fixes for i256 and u256

`i256` and `u256`
- operators now use the same overflow convention as primitives
- implement `<<` and `-` (previously just `>>` and `+`)
- implement `Ord` correctly (the previous `PartialOrd` was broken)
- correct `i256::SIGNED` to `true`

The `Int`-trait is extended with `trailing_zeros`, `carrying_add`, and
`borrowing_sub`.
---
 compiler-builtins/libm-test/benches/icount.rs |  18 ++-
 compiler-builtins/libm-test/tests/u256.rs     |  46 +++++-
 .../libm/src/math/support/big.rs              | 133 +++++++++++-------
 .../libm/src/math/support/big/tests.rs        |  63 ++++++++-
 .../libm/src/math/support/int_traits.rs       |  23 ++-
 5 files changed, 223 insertions(+), 60 deletions(-)

diff --git a/compiler-builtins/libm-test/benches/icount.rs b/compiler-builtins/libm-test/benches/icount.rs
index a0928a29f9992..02ee13f804f16 100644
--- a/compiler-builtins/libm-test/benches/icount.rs
+++ b/compiler-builtins/libm-test/benches/icount.rs
@@ -119,6 +119,22 @@ fn icount_bench_u256_add(cases: Vec<(u256, u256)>) {
     }
 }
 
+#[library_benchmark]
+#[bench::linspace(setup_u256_add())]
+fn icount_bench_u256_sub(cases: Vec<(u256, u256)>) {
+    for (x, y) in cases.iter().copied() {
+        black_box(black_box(x) - black_box(y));
+    }
+}
+
+#[library_benchmark]
+#[bench::linspace(setup_u256_shift())]
+fn icount_bench_u256_shl(cases: Vec<(u256, u32)>) {
+    for (x, y) in cases.iter().copied() {
+        black_box(black_box(x) << black_box(y));
+    }
+}
+
 #[library_benchmark]
 #[bench::linspace(setup_u256_shift())]
 fn icount_bench_u256_shr(cases: Vec<(u256, u32)>) {
@@ -129,7 +145,7 @@ fn icount_bench_u256_shr(cases: Vec<(u256, u32)>) {
 
 library_benchmark_group!(
     name = icount_bench_u128_group;
-    benchmarks = icount_bench_u128_widen_mul, icount_bench_u256_add, icount_bench_u256_shr
+    benchmarks = icount_bench_u128_widen_mul, icount_bench_u256_add, icount_bench_u256_sub, icount_bench_u256_shl, icount_bench_u256_shr
 );
 
 #[library_benchmark]
diff --git a/compiler-builtins/libm-test/tests/u256.rs b/compiler-builtins/libm-test/tests/u256.rs
index 8cbb3ad226f67..d1c5cfbcc586d 100644
--- a/compiler-builtins/libm-test/tests/u256.rs
+++ b/compiler-builtins/libm-test/tests/u256.rs
@@ -111,12 +111,54 @@ fn mp_u256_add() {
         let y = random_u256(&mut rng);
         assign_bigint(&mut bx, x);
         assign_bigint(&mut by, y);
-        let actual = x + y;
+        let actual = if u256::MAX - x >= y {
+            x + y
+        } else {
+            // otherwise (u256::MAX - x) < y, so the wrapped result is
+            // (x + y) - (u256::MAX + 1) == y - (u256::MAX - x) - 1
+            y - (u256::MAX - x) - 1_u128.widen()
+        };
         bx += &by;
         check_one(|| hexu(x), || Some(hexu(y)), actual, &mut bx);
     }
 }
 
+#[test]
+fn mp_u256_sub() {
+    let mut rng = ChaCha8Rng::from_seed(*SEED);
+    let mut bx = BigInt::new();
+    let mut by = BigInt::new();
+
+    for _ in 0..bigint_fuzz_iteration_count() {
+        let x = random_u256(&mut rng);
+        let y = random_u256(&mut rng);
+        assign_bigint(&mut bx, x);
+        assign_bigint(&mut by, y);
+
+        // since the operators (may) panic on overflow,
+        // we should test something that doesn't
+        let actual = if x >= y { x - y } else { y - x };
+        bx -= &by;
+        bx.abs_mut();
+        check_one(|| hexu(x), || Some(hexu(y)), actual, &mut bx);
+    }
+}
+
+#[test]
+fn mp_u256_shl() {
+    let mut rng = ChaCha8Rng::from_seed(*SEED);
+    let mut bx = BigInt::new();
+
+    for _ in 0..bigint_fuzz_iteration_count() {
+        let x = random_u256(&mut rng);
+        let shift: u32 = rng.random_range(0..256);
+        assign_bigint(&mut bx, x);
+        let actual = x << shift;
+        bx <<= shift;
+        check_one(|| hexu(x), || Some(shift.to_string()), actual, &mut bx);
+    }
+}
+
 #[test]
 fn mp_u256_shr() {
     let mut rng = ChaCha8Rng::from_seed(*SEED);
@@ -124,7 +166,7 @@ fn mp_u256_shr() {
 
     for _ in 0..bigint_fuzz_iteration_count() {
         let x = random_u256(&mut rng);
-        let shift: u32 = rng.random_range(0..255);
+        let shift: u32 = rng.random_range(0..256);
         assign_bigint(&mut bx, x);
         let actual = x >> shift;
         bx >>= shift;
diff --git a/compiler-builtins/libm/src/math/support/big.rs b/compiler-builtins/libm/src/math/support/big.rs
index 8a52d86cc9827..b7f1285424956 100644
--- a/compiler-builtins/libm/src/math/support/big.rs
+++ b/compiler-builtins/libm/src/math/support/big.rs
@@ -11,10 +11,10 @@ const U128_LO_MASK: u128 = u64::MAX as u128;
 
 /// A 256-bit unsigned integer represented as two 128-bit native-endian limbs.
 #[allow(non_camel_case_types)]
-#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
+#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Eq, Ord)]
 pub struct u256 {
-    pub lo: u128,
     pub hi: u128,
+    pub lo: u128,
 }
 
 impl u256 {
@@ -28,17 +28,17 @@ impl u256 {
     pub fn signed(self) -> i256 {
         i256 {
             lo: self.lo,
-            hi: self.hi,
+            hi: self.hi as i128,
         }
     }
 }
 
 /// A 256-bit signed integer represented as two 128-bit native-endian limbs.
 #[allow(non_camel_case_types)]
-#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
+#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Eq, Ord)]
 pub struct i256 {
+    pub hi: i128,
     pub lo: u128,
-    pub hi: u128,
 }
 
 impl i256 {
@@ -47,7 +47,7 @@ impl i256 {
     pub fn unsigned(self) -> u256 {
         u256 {
             lo: self.lo,
-            hi: self.hi,
+            hi: self.hi as u128,
         }
     }
 }
@@ -73,17 +73,17 @@ impl MinInt for i256 {
 
     type Unsigned = u256;
 
-    const SIGNED: bool = false;
+    const SIGNED: bool = true;
     const BITS: u32 = 256;
     const ZERO: Self = Self { lo: 0, hi: 0 };
     const ONE: Self = Self { lo: 1, hi: 0 };
     const MIN: Self = Self {
-        lo: 0,
-        hi: 1 << 127,
+        lo: u128::MIN,
+        hi: i128::MIN,
     };
     const MAX: Self = Self {
         lo: u128::MAX,
-        hi: u128::MAX >> 1,
+        hi: i128::MAX,
     };
 }
 
@@ -109,60 +109,86 @@ macro_rules! impl_common {
             }
         }
 
-        impl ops::Shl<u32> for $ty {
+        impl ops::Add<Self> for $ty {
             type Output = Self;
 
-            fn shl(self, _rhs: u32) -> Self::Output {
-                unimplemented!("only used to meet trait bounds")
+            fn add(self, rhs: Self) -> Self::Output {
+                let (lo, carry) = self.lo.overflowing_add(rhs.lo);
+                let (hi, of) = Int::carrying_add(self.hi, rhs.hi, carry);
+                debug_assert!(!of, "attempt to add with overflow");
+                Self { lo, hi }
             }
         }
-    };
-}
 
-impl_common!(i256);
-impl_common!(u256);
+        impl ops::Sub<Self> for $ty {
+            type Output = Self;
 
-impl ops::Add<Self> for u256 {
-    type Output = Self;
+            fn sub(self, rhs: Self) -> Self::Output {
+                let (lo, borrow) = self.lo.overflowing_sub(rhs.lo);
+                let (hi, of) = Int::borrowing_sub(self.hi, rhs.hi, borrow);
+                debug_assert!(!of, "attempt to subtract with overflow");
+                Self { lo, hi }
+            }
+        }
 
-    fn add(self, rhs: Self) -> Self::Output {
-        let (lo, carry) = self.lo.overflowing_add(rhs.lo);
-        let hi = self.hi.wrapping_add(carry as u128).wrapping_add(rhs.hi);
+        impl ops::Shl<u32> for $ty {
+            type Output = Self;
 
-        Self { lo, hi }
-    }
-}
+            fn shl(mut self, rhs: u32) -> Self::Output {
+                debug_assert!(rhs < Self::BITS, "attempt to shift left with overflow");
 
-impl ops::Shr<u32> for u256 {
-    type Output = Self;
+                let half_bits = Self::BITS / 2;
+                let low_mask = half_bits - 1;
+                let s = rhs & low_mask;
 
-    fn shr(mut self, rhs: u32) -> Self::Output {
-        debug_assert!(rhs < Self::BITS, "attempted to shift right with overflow");
-        if rhs >= Self::BITS {
-            return Self::ZERO;
-        }
+                let lo = self.lo;
+                let hi = self.hi;
 
-        if rhs == 0 {
-            return self;
-        }
+                self.lo = lo << s;
 
-        if rhs < 128 {
-            self.lo >>= rhs;
-            self.lo |= self.hi << (128 - rhs);
-        } else {
-            self.lo = self.hi >> (rhs - 128);
+                if rhs & half_bits == 0 {
+                    self.hi = (lo >> (low_mask ^ s) >> 1) as _;
+                    self.hi |= hi << s;
+                } else {
+                    self.hi = self.lo as _;
+                    self.lo = 0;
+                }
+                self
+            }
         }
 
-        if rhs < 128 {
-            self.hi >>= rhs;
-        } else {
-            self.hi = 0;
-        }
+        impl ops::Shr<u32> for $ty {
+            type Output = Self;
 
-        self
-    }
+            fn shr(mut self, rhs: u32) -> Self::Output {
+                debug_assert!(rhs < Self::BITS, "attempt to shift right with overflow");
+
+                let half_bits = Self::BITS / 2;
+                let low_mask = half_bits - 1;
+                let s = rhs & low_mask;
+
+                let lo = self.lo;
+                let hi = self.hi;
+
+                self.hi = hi >> s;
+
+                #[allow(unused_comparisons)]
+                if rhs & half_bits == 0 {
+                    self.lo = (hi << (low_mask ^ s) << 1) as _;
+                    self.lo |= lo >> s;
+                } else {
+                    self.lo = self.hi as _;
+                    self.hi = if hi < 0 { !0 } else { 0 };
+                }
+                self
+            }
+        }
+    };
 }
 
+impl_common!(i256);
+impl_common!(u256);
+
 impl HInt for u128 {
     type D = u256;
 
@@ -200,7 +226,7 @@ impl HInt for u128 {
     }
 
     fn widen_hi(self) -> Self::D {
-        self.widen() << <Self as MinInt>::BITS
+        u256 { lo: 0, hi: self }
     }
 }
 
@@ -208,11 +234,10 @@ impl HInt for i128 {
     type D = i256;
 
     fn widen(self) -> Self::D {
-        let mut ret = self.unsigned().zero_widen().signed();
-        if self.is_negative() {
-            ret.hi = u128::MAX;
+        i256 {
+            lo: self as u128,
+            hi: if self < 0 { -1 } else { 0 },
         }
-        ret
     }
 
     fn zero_widen(self) -> Self::D {
@@ -228,7 +253,7 @@ impl HInt for i128 {
     }
 
     fn widen_hi(self) -> Self::D {
-        self.widen() << <Self as MinInt>::BITS
+        i256 { lo: 0, hi: self }
     }
 }
 
@@ -252,6 +277,6 @@ impl DInt for i256 {
     }
 
     fn hi(self) -> Self::H {
-        self.hi as i128
+        self.hi
     }
 }
diff --git a/compiler-builtins/libm/src/math/support/big/tests.rs b/compiler-builtins/libm/src/math/support/big/tests.rs
index d2010f0216e35..d54706c726072 100644
--- a/compiler-builtins/libm/src/math/support/big/tests.rs
+++ b/compiler-builtins/libm/src/math/support/big/tests.rs
@@ -36,7 +36,7 @@ fn widen_i128() {
         (LOHI_SPLIT as i128).widen(),
         i256 {
             lo: LOHI_SPLIT,
-            hi: u128::MAX
+            hi: -1,
         }
     );
     assert_eq!((-1i128).zero_widen().unsigned(), (u128::MAX).widen());
@@ -275,3 +275,64 @@ fn shr_u256_overflow() {
     assert_eq!(u256::MAX >> 257, u256::ZERO);
     assert_eq!(u256::MAX >> u32::MAX, u256::ZERO);
 }
+
+#[test]
+fn u256_ord() {
+    let _1 = u256::ONE;
+    let _2 = _1 + _1;
+    for x in u8::MIN..u8::MAX {
+        let y = x + 1;
+        let wx = (x as u128).widen_hi();
+        let wy = (y as u128).widen_hi();
+        assert!([wx, wx + _1, wx + _2, wy, wy + _1, wy + _2].is_sorted());
+    }
+}
+#[test]
+fn i256_ord() {
+    let _1 = i256::ONE;
+    let _2 = _1 + _1;
+    for x in i8::MIN..i8::MAX {
+        let y = x + 1;
+        let wx = (x as i128).widen_hi();
+        let wy = (y as i128).widen_hi();
+        assert!([wx, wx + _1, wx + _2, wy - _2, wy - _1, wy].is_sorted());
+    }
+}
+
+#[test]
+fn u256_shifts() {
+    let _1 = u256::ONE;
+    for k in 0..255 {
+        let x = _1 << k;
+        let x2 = _1 << (k + 1);
+        assert!(x < x2);
+        assert_eq!(x << 1, x2);
+        assert_eq!(x + x, x2);
+        assert_eq!(x >> k, _1);
+        assert_eq!(x2 >> (k + 1), _1);
+    }
+}
+#[test]
+fn i256_shifts() {
+    let _1 = i256::ONE;
+    for k in 0..254 {
+        let x = _1 << k;
+        let x2 = _1 << (k + 1);
+        assert!(x < x2);
+        assert_eq!(x << 1, x2);
+        assert_eq!(x + x, x2);
+        assert_eq!(x >> k, _1);
+        assert_eq!(x2 >> (k + 1), _1);
+    }
+
+    let min = _1 << 255;
+    assert_eq!(min, i256::MIN);
+    let mut x = min;
+    for k in 0..255 {
+        assert_eq!(x, min >> k);
+        let y = x >> 1;
+        assert_eq!(y + y, x);
+        assert!(x < y);
+        x = y;
+    }
+}
diff --git a/compiler-builtins/libm/src/math/support/int_traits.rs b/compiler-builtins/libm/src/math/support/int_traits.rs
index 9b29e2f4561d5..9d8826dfed3fe 100644
--- a/compiler-builtins/libm/src/math/support/int_traits.rs
+++ b/compiler-builtins/libm/src/math/support/int_traits.rs
@@ -37,8 +37,6 @@ pub trait Int:
     + fmt::Display
     + fmt::Binary
     + fmt::LowerHex
-    + PartialEq
-    + PartialOrd
     + ops::AddAssign
     + ops::SubAssign
     + ops::MulAssign
@@ -102,7 +100,10 @@ pub trait Int:
     fn rotate_left(self, other: u32) -> Self;
     fn overflowing_add(self, other: Self) -> (Self, bool);
     fn overflowing_sub(self, other: Self) -> (Self, bool);
+    fn carrying_add(self, other: Self, carry: bool) -> (Self, bool);
+    fn borrowing_sub(self, other: Self, borrow: bool) -> (Self, bool);
     fn leading_zeros(self) -> u32;
+    fn trailing_zeros(self) -> u32;
     fn ilog2(self) -> u32;
 }
 
@@ -168,12 +169,30 @@ macro_rules! int_impl_common {
             <Self>::leading_zeros(self)
         }
 
+        fn trailing_zeros(self) -> u32 {
+            <Self>::trailing_zeros(self)
+        }
+
         fn ilog2(self) -> u32 {
             // On our older MSRV, this resolves to the trait method. Which won't actually work,
             // but this is only called behind other gates.
             #[allow(clippy::incompatible_msrv)]
             <Self>::ilog2(self)
         }
+
+        fn carrying_add(self, other: Self, carry: bool) -> (Self, bool) {
+            let (ab, of1) = self.overflowing_add(other);
+            let (abc, of2) = ab.overflowing_add(Self::from_bool(carry));
+            // `of1 && of2` is possible with signed integers if a negative sum
+            // overflows to `MAX` and adding the carry overflows again back to `MIN`
+            (abc, of1 ^ of2)
+        }
+
+        fn borrowing_sub(self, other: Self, borrow: bool) -> (Self, bool) {
+            let (ab, of1) = self.overflowing_sub(other);
+            let (abc, of2) = ab.overflowing_sub(Self::from_bool(borrow));
+            (abc, of1 ^ of2)
+        }
     };
 }
 

From add7b9128a2e8cad9ffb354957c7c1f46fc0d089 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Mon, 30 Jun 2025 16:53:21 -0500
Subject: [PATCH 11/25] Use the compiler to determine whether or not to enable
 `f16` and `f128`

Currently we whether or not to build and test `f16` and `f128` support
mostly based on the target triple. This isn't always accurate, however,
since support also varies by backend and the backend version.

Since recently, `rustc` is aware of this with the unstable config option
`target_has_reliable_{f16,f128}`, which better represents when the types
are actually expected to be available and usable. Switch our
compiler-builtins and libm configuration to use this by probing `rustc`
for the target's settings.

A few small `cfg` fixes are needed with this.
---
 .../builtins-test-intrinsics/build.rs         |  1 -
 .../builtins-test/benches/float_cmp.rs        |  2 +
 compiler-builtins/builtins-test/build.rs      |  1 -
 compiler-builtins/builtins-test/tests/conv.rs |  4 +-
 .../builtins-test/tests/div_rem.rs            |  4 +-
 compiler-builtins/compiler-builtins/build.rs  |  3 +-
 .../compiler-builtins/configure.rs            | 81 +++++++------------
 compiler-builtins/libm/configure.rs           | 81 +++++++------------
 8 files changed, 66 insertions(+), 111 deletions(-)

diff --git a/compiler-builtins/builtins-test-intrinsics/build.rs b/compiler-builtins/builtins-test-intrinsics/build.rs
index 89b126ff2b2ed..b82581262f7b0 100644
--- a/compiler-builtins/builtins-test-intrinsics/build.rs
+++ b/compiler-builtins/builtins-test-intrinsics/build.rs
@@ -6,6 +6,5 @@ fn main() {
     println!("cargo::rerun-if-changed=../configure.rs");
 
     let target = builtins_configure::Target::from_env();
-    builtins_configure::configure_f16_f128(&target);
     builtins_configure::configure_aliases(&target);
 }
diff --git a/compiler-builtins/builtins-test/benches/float_cmp.rs b/compiler-builtins/builtins-test/benches/float_cmp.rs
index 87a89efb5a4fe..da29b5d313263 100644
--- a/compiler-builtins/builtins-test/benches/float_cmp.rs
+++ b/compiler-builtins/builtins-test/benches/float_cmp.rs
@@ -177,6 +177,7 @@ float_bench! {
     ],
 }
 
+#[cfg(f128_enabled)]
 float_bench! {
     name: cmp_f128_gt,
     sig: (a: f128, b: f128) -> CmpResult,
@@ -189,6 +190,7 @@ float_bench! {
     asm: []
 }
 
+#[cfg(f128_enabled)]
 float_bench! {
     name: cmp_f128_unord,
     sig: (a: f128, b: f128) -> CmpResult,
diff --git a/compiler-builtins/builtins-test/build.rs b/compiler-builtins/builtins-test/build.rs
index e8f4eb4dd22eb..5b2dcd12ef86f 100644
--- a/compiler-builtins/builtins-test/build.rs
+++ b/compiler-builtins/builtins-test/build.rs
@@ -116,5 +116,4 @@ fn main() {
     }
 
     builtins_configure::configure_aliases(&target);
-    builtins_configure::configure_f16_f128(&target);
 }
diff --git a/compiler-builtins/builtins-test/tests/conv.rs b/compiler-builtins/builtins-test/tests/conv.rs
index 491915d9bb172..7d729364faefb 100644
--- a/compiler-builtins/builtins-test/tests/conv.rs
+++ b/compiler-builtins/builtins-test/tests/conv.rs
@@ -118,7 +118,7 @@ mod i_to_f {
         i128, __floattidf;
     }
 
-    #[cfg(not(feature = "no-f16-f128"))]
+    #[cfg(f128_enabled)]
     #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
     i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
         u32, __floatunsitf;
@@ -129,7 +129,7 @@ mod i_to_f {
         i128, __floattitf;
     }
 
-    #[cfg(not(feature = "no-f16-f128"))]
+    #[cfg(f128_enabled)]
     #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
     i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
         u32, __floatunsikf;
diff --git a/compiler-builtins/builtins-test/tests/div_rem.rs b/compiler-builtins/builtins-test/tests/div_rem.rs
index 5ae653cc90cc4..e8327f9b4b865 100644
--- a/compiler-builtins/builtins-test/tests/div_rem.rs
+++ b/compiler-builtins/builtins-test/tests/div_rem.rs
@@ -147,7 +147,7 @@ mod float_div {
         f64, __divdf3, Double, all();
     }
 
-    #[cfg(not(feature = "no-f16-f128"))]
+    #[cfg(f128_enabled)]
     #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
     float! {
         f128, __divtf3, Quad,
@@ -156,7 +156,7 @@ mod float_div {
         not(any(feature = "no-sys-f128", all(target_arch = "aarch64", target_os = "linux")));
     }
 
-    #[cfg(not(feature = "no-f16-f128"))]
+    #[cfg(f128_enabled)]
     #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
     float! {
         f128, __divkf3, Quad, not(feature = "no-sys-f128");
diff --git a/compiler-builtins/compiler-builtins/build.rs b/compiler-builtins/compiler-builtins/build.rs
index 018899faf1d44..8f51c12b535dc 100644
--- a/compiler-builtins/compiler-builtins/build.rs
+++ b/compiler-builtins/compiler-builtins/build.rs
@@ -2,7 +2,7 @@ mod configure;
 
 use std::env;
 
-use configure::{Target, configure_aliases, configure_f16_f128};
+use configure::{Target, configure_aliases};
 
 fn main() {
     println!("cargo::rerun-if-changed=build.rs");
@@ -12,7 +12,6 @@ fn main() {
     let cwd = env::current_dir().unwrap();
 
     configure_check_cfg();
-    configure_f16_f128(&target);
     configure_aliases(&target);
 
     configure_libm(&target);
diff --git a/compiler-builtins/compiler-builtins/configure.rs b/compiler-builtins/compiler-builtins/configure.rs
index d825f35a9aa05..a1e45080e7106 100644
--- a/compiler-builtins/compiler-builtins/configure.rs
+++ b/compiler-builtins/compiler-builtins/configure.rs
@@ -1,6 +1,7 @@
 // Configuration that is shared between `compiler_builtins` and `builtins_test`.
 
-use std::env;
+use std::process::{Command, Stdio};
+use std::{env, str};
 
 #[derive(Debug)]
 #[allow(dead_code)]
@@ -16,6 +17,8 @@ pub struct Target {
     pub pointer_width: u8,
     pub little_endian: bool,
     pub features: Vec<String>,
+    pub reliable_f128: bool,
+    pub reliable_f16: bool,
 }
 
 impl Target {
@@ -32,6 +35,19 @@ impl Target {
             .map(|s| s.to_lowercase().replace("_", "-"))
             .collect();
 
+        // Query rustc for options that Cargo does not provide env for. The bootstrap hack is used
+        // to get consistent output regardless of channel (`f16`/`f128` config options are hidden
+        // on stable otherwise).
+        let mut cmd = Command::new(env::var("RUSTC").unwrap());
+        cmd.args(["--print=cfg", "--target", &triple])
+            .env("RUSTC_BOOTSTRAP", "1")
+            .stderr(Stdio::inherit());
+        let out = cmd
+            .output()
+            .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
+        assert!(out.status.success(), "failed to run `{cmd:?}`");
+        let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
+
         Self {
             triple,
             triple_split,
@@ -51,6 +67,8 @@ impl Target {
                 .split(",")
                 .map(ToOwned::to_owned)
                 .collect(),
+            reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
+            reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
         }
     }
 
@@ -74,63 +92,24 @@ pub fn configure_aliases(target: &Target) {
     if target.triple_split[0] == "thumbv6m" || target.triple_split[0] == "thumbv8m.base" {
         println!("cargo:rustc-cfg=thumb_1")
     }
-}
-
-/// Configure whether or not `f16` and `f128` support should be enabled.
-pub fn configure_f16_f128(target: &Target) {
-    // Set whether or not `f16` and `f128` are supported at a basic level by LLVM. This only means
-    // that the backend will not crash when using these types and generates code that can be called
-    // without crashing (no infinite recursion). This does not mean that the platform doesn't have
-    // ABI or other bugs.
-    //
-    // We do this here rather than in `rust-lang/rust` because configuring via cargo features is
-    // not straightforward.
-    //
-    // Original source of this list:
-    // <https://github.com/rust-lang/compiler-builtins/pull/652#issuecomment-2266151350>
-    let f16_enabled = match target.arch.as_str() {
-        // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
-        "arm64ec" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/50374>
-        "s390x" => false,
-        // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981>
-        "csky" => false,
-        "hexagon" => false,
-        "powerpc" | "powerpc64" => false,
-        "sparc" | "sparc64" => false,
-        "wasm32" | "wasm64" => false,
-        // Most everything else works as of LLVM 19
-        _ => true,
-    };
 
-    let f128_enabled = match target.arch.as_str() {
-        // Unsupported (libcall is not supported) <https://github.com/llvm/llvm-project/issues/121122>
-        "amdgpu" => false,
-        // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
-        "arm64ec" => false,
-        // FIXME(llvm20): fixed by <https://github.com/llvm/llvm-project/pull/117525>
-        "mips64" | "mips64r6" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/95471>
-        "nvptx64" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/101545>
-        "powerpc64" if &target.os == "aix" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/41838>
-        "sparc" => false,
-        // Most everything else works as of LLVM 19
-        _ => true,
-    };
+    /* Not all backends support `f16` and `f128` to the same level on all architectures, so we
+     * need to disable things if the compiler may crash. See configuration at:
+     * * https://github.com/rust-lang/rust/blob/c65dccabacdfd6c8a7f7439eba13422fdd89b91e/compiler/rustc_codegen_llvm/src/llvm_util.rs#L367-L432
+     * * https://github.com/rust-lang/rustc_codegen_gcc/blob/4b5c44b14166083eef8d71f15f5ea1f53fc976a0/src/lib.rs#L496-L507
+     * * https://github.com/rust-lang/rustc_codegen_cranelift/blob/c713ffab3c6e28ab4b4dd4e392330f786ea657ad/src/lib.rs#L196-L226
+     */
 
-    // If the feature is set, disable these types.
-    let disable_both = env::var_os("CARGO_FEATURE_NO_F16_F128").is_some();
+    // If the feature is set, disable both of these types.
+    let no_f16_f128 = target.cargo_features.iter().any(|s| s == "no-f16-f128");
 
     println!("cargo::rustc-check-cfg=cfg(f16_enabled)");
-    println!("cargo::rustc-check-cfg=cfg(f128_enabled)");
-
-    if f16_enabled && !disable_both {
+    if target.reliable_f16 && !no_f16_f128 {
         println!("cargo::rustc-cfg=f16_enabled");
     }
 
-    if f128_enabled && !disable_both {
+    println!("cargo::rustc-check-cfg=cfg(f128_enabled)");
+    if target.reliable_f128 && !no_f16_f128 {
         println!("cargo::rustc-cfg=f128_enabled");
     }
 }
diff --git a/compiler-builtins/libm/configure.rs b/compiler-builtins/libm/configure.rs
index 2a497c7b11790..6562ecbe5db40 100644
--- a/compiler-builtins/libm/configure.rs
+++ b/compiler-builtins/libm/configure.rs
@@ -1,7 +1,8 @@
 // Configuration shared with both libm and libm-test
 
-use std::env;
 use std::path::PathBuf;
+use std::process::{Command, Stdio};
+use std::{env, str};
 
 #[allow(dead_code)]
 pub struct Config {
@@ -9,6 +10,7 @@ pub struct Config {
     pub out_dir: PathBuf,
     pub opt_level: String,
     pub cargo_features: Vec<String>,
+    pub target_triple: String,
     pub target_arch: String,
     pub target_env: String,
     pub target_family: Option<String>,
@@ -16,10 +18,13 @@ pub struct Config {
     pub target_string: String,
     pub target_vendor: String,
     pub target_features: Vec<String>,
+    pub reliable_f128: bool,
+    pub reliable_f16: bool,
 }
 
 impl Config {
     pub fn from_env() -> Self {
+        let target_triple = env::var("TARGET").unwrap();
         let target_features = env::var("CARGO_CFG_TARGET_FEATURE")
             .map(|feats| feats.split(',').map(ToOwned::to_owned).collect())
             .unwrap_or_default();
@@ -28,7 +33,21 @@ impl Config {
             .map(|s| s.to_lowercase().replace("_", "-"))
             .collect();
 
+        // Query rustc for options that Cargo does not provide env for. The bootstrap hack is used
+        // to get consistent output regardless of channel (`f16`/`f128` config options are hidden
+        // on stable otherwise).
+        let mut cmd = Command::new(env::var("RUSTC").unwrap());
+        cmd.args(["--print=cfg", "--target", &target_triple])
+            .env("RUSTC_BOOTSTRAP", "1")
+            .stderr(Stdio::inherit());
+        let out = cmd
+            .output()
+            .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
+        assert!(out.status.success(), "failed to run `{cmd:?}`");
+        let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
+
         Self {
+            target_triple,
             manifest_dir: PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap()),
             out_dir: PathBuf::from(env::var("OUT_DIR").unwrap()),
             opt_level: env::var("OPT_LEVEL").unwrap(),
@@ -40,6 +59,8 @@ impl Config {
             target_string: env::var("TARGET").unwrap(),
             target_vendor: env::var("CARGO_CFG_TARGET_VENDOR").unwrap(),
             target_features,
+            reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
+            reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
         }
     }
 }
@@ -128,62 +149,18 @@ fn emit_f16_f128_cfg(cfg: &Config) {
         return;
     }
 
-    // Set whether or not `f16` and `f128` are supported at a basic level by LLVM. This only means
-    // that the backend will not crash when using these types and generates code that can be called
-    // without crashing (no infinite recursion). This does not mean that the platform doesn't have
-    // ABI or other bugs.
-    //
-    // We do this here rather than in `rust-lang/rust` because configuring via cargo features is
-    // not straightforward.
-    //
-    // Original source of this list:
-    // <https://github.com/rust-lang/compiler-builtins/pull/652#issuecomment-2266151350>
-    let f16_enabled = match cfg.target_arch.as_str() {
-        // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
-        "arm64ec" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/50374>
-        "s390x" => false,
-        // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981>
-        // FIXME(llvm): loongarch fixed by <https://github.com/llvm/llvm-project/pull/107791>
-        "csky" => false,
-        "hexagon" => false,
-        "loongarch64" => false,
-        "mips" | "mips64" | "mips32r6" | "mips64r6" => false,
-        "powerpc" | "powerpc64" => false,
-        "sparc" | "sparc64" => false,
-        "wasm32" | "wasm64" => false,
-        // Most everything else works as of LLVM 19
-        _ => true,
-    };
-
-    let f128_enabled = match cfg.target_arch.as_str() {
-        // Unsupported (libcall is not supported) <https://github.com/llvm/llvm-project/issues/121122>
-        "amdgpu" => false,
-        // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
-        "arm64ec" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/96432>
-        "mips64" | "mips64r6" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/95471>
-        "nvptx64" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/101545>
-        "powerpc64" if &cfg.target_os == "aix" => false,
-        // Selection failure <https://github.com/llvm/llvm-project/issues/41838>
-        "sparc" => false,
-        // Most everything else works as of LLVM 19
-        _ => true,
-    };
-
-    // If the feature is set, disable these types.
-    let disable_both = env::var_os("CARGO_FEATURE_NO_F16_F128").is_some();
+    /* See the compiler-builtins configure file for info about the meaning of these options */
 
-    println!("cargo:rustc-check-cfg=cfg(f16_enabled)");
-    println!("cargo:rustc-check-cfg=cfg(f128_enabled)");
+    // If the feature is set, disable both of these types.
+    let no_f16_f128 = cfg.cargo_features.iter().any(|s| s == "no-f16-f128");
 
-    if f16_enabled && !disable_both {
+    println!("cargo:rustc-check-cfg=cfg(f16_enabled)");
+    if cfg.reliable_f16 && !no_f16_f128 {
         println!("cargo:rustc-cfg=f16_enabled");
     }
 
-    if f128_enabled && !disable_both {
+    println!("cargo:rustc-check-cfg=cfg(f128_enabled)");
+    if cfg.reliable_f128 && !no_f16_f128 {
         println!("cargo:rustc-cfg=f128_enabled");
     }
 }

From 2e3f8d4d55b69da6e09ffc567c7d7a3540958673 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 4 Jul 2025 16:53:19 -0500
Subject: [PATCH 12/25] Remove the `let_chains` feature now that it is stable

---
 compiler-builtins/crates/libm-macros/src/lib.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/compiler-builtins/crates/libm-macros/src/lib.rs b/compiler-builtins/crates/libm-macros/src/lib.rs
index 482da974ca89f..7efa1488f570e 100644
--- a/compiler-builtins/crates/libm-macros/src/lib.rs
+++ b/compiler-builtins/crates/libm-macros/src/lib.rs
@@ -1,5 +1,3 @@
-#![feature(let_chains)]
-
 mod enums;
 mod parse;
 mod shared;

From c59dd11c7c7cd3336c4bed3efe6434f8ab0fc211 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 4 Jul 2025 17:03:45 -0500
Subject: [PATCH 13/25] symcheck: Make `target` a positional argument

This makes it more obvious what we intend to check rather than looking
for `--target`.
---
 compiler-builtins/ci/run.sh                   | 27 ++++++--------
 .../crates/symbol-check/src/main.rs           | 37 ++++++++++++-------
 2 files changed, 35 insertions(+), 29 deletions(-)

diff --git a/compiler-builtins/ci/run.sh b/compiler-builtins/ci/run.sh
index 27b9686eac644..8b7965bb2056d 100755
--- a/compiler-builtins/ci/run.sh
+++ b/compiler-builtins/ci/run.sh
@@ -54,29 +54,26 @@ symcheck=(cargo run -p symbol-check --release)
 [[ "$target" = "wasm"* ]] && symcheck+=(--features wasm)
 symcheck+=(-- build-and-check)
 
-"${symcheck[@]}" -p compiler_builtins --target "$target"
-"${symcheck[@]}" -p compiler_builtins --target "$target" --release
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features c
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features c --release
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features no-asm
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features no-asm --release
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features no-f16-f128
-"${symcheck[@]}" -p compiler_builtins --target "$target" --features no-f16-f128 --release
+"${symcheck[@]}" "$target" -- -p compiler_builtins
+"${symcheck[@]}" "$target" -- -p compiler_builtins --release
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features c
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features c --release
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features no-asm
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features no-asm --release
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features no-f16-f128
+"${symcheck[@]}" "$target" -- -p compiler_builtins --features no-f16-f128 --release
 
 run_intrinsics_test() {
-    args=(
-        --target "$target" --verbose \
-        --manifest-path builtins-test-intrinsics/Cargo.toml
-    )
-    args+=( "$@" )
+    build_args=(--verbose --manifest-path builtins-test-intrinsics/Cargo.toml)
+    build_args+=("$@")
 
     # symcheck also checks the results of builtins-test-intrinsics
-    "${symcheck[@]}" "${args[@]}"
+    "${symcheck[@]}" "$target" -- "${build_args[@]}"
 
     # FIXME: we get access violations on Windows, our entrypoint may need to
     # be tweaked.
     if [ "${BUILD_ONLY:-}" != "1" ] && ! [[ "$target" = *"windows"* ]]; then
-        cargo run "${args[@]}"
+        cargo run --target "$target" "${build_args[@]}"
     fi
 }
 
diff --git a/compiler-builtins/crates/symbol-check/src/main.rs b/compiler-builtins/crates/symbol-check/src/main.rs
index 843a943fb5f08..f60d4f0d36f86 100644
--- a/compiler-builtins/crates/symbol-check/src/main.rs
+++ b/compiler-builtins/crates/symbol-check/src/main.rs
@@ -18,10 +18,12 @@ const CHECK_EXTENSIONS: &[Option<&str>] = &[Some("rlib"), Some("a"), Some("exe")
 
 const USAGE: &str = "Usage:
 
-    symbol-check build-and-check CARGO_ARGS ...
+    symbol-check build-and-check [TARGET] -- CARGO_BUILD_ARGS ...
 
-Cargo will get invoked with `CARGO_ARGS` and all output
+Cargo will get invoked with `CARGO_ARGS` and the specified target. All output
 `compiler_builtins*.rlib` files will be checked.
+
+If TARGET is not specified, the host target is used.
 ";
 
 fn main() {
@@ -30,11 +32,13 @@ fn main() {
     let args_ref = args.iter().map(String::as_str).collect::<Vec<_>>();
 
     match &args_ref[1..] {
-        ["build-and-check", "--target", target, args @ ..] if !args.is_empty() => {
-            run_build_and_check(Some(target), args);
+        ["build-and-check", target, "--", args @ ..] if !args.is_empty() => {
+            check_cargo_args(args);
+            run_build_and_check(target, args);
         }
-        ["build-and-check", args @ ..] if !args.is_empty() => {
-            run_build_and_check(None, args);
+        ["build-and-check", "--", args @ ..] if !args.is_empty() => {
+            check_cargo_args(args);
+            run_build_and_check(&host_target(), args);
         }
         _ => {
             println!("{USAGE}");
@@ -43,7 +47,18 @@ fn main() {
     }
 }
 
-fn run_build_and_check(target: Option<&str>, args: &[&str]) {
+/// Make sure `--target` isn't passed to avoid confusion (since it should be proivded only once,
+/// positionally).
+fn check_cargo_args(args: &[&str]) {
+    for arg in args {
+        assert!(
+            !arg.contains("--target"),
+            "target must be passed positionally. {USAGE}"
+        );
+    }
+}
+
+fn run_build_and_check(target: &str, args: &[&str]) {
     let paths = exec_cargo_with_args(target, args);
     for path in paths {
         println!("Checking {}", path.display());
@@ -70,13 +85,7 @@ fn host_target() -> String {
 
 /// Run `cargo build` with the provided additional arguments, collecting the list of created
 /// libraries.
-fn exec_cargo_with_args(target: Option<&str>, args: &[&str]) -> Vec<PathBuf> {
-    let mut host = String::new();
-    let target = target.unwrap_or_else(|| {
-        host = host_target();
-        host.as_str()
-    });
-
+fn exec_cargo_with_args(target: &str, args: &[&str]) -> Vec<PathBuf> {
     let mut cmd = Command::new("cargo");
     cmd.args(["build", "--target", target, "--message-format=json"])
         .args(args)

From d358eb3226cf32320e8e097ae66bb92eb956e67c Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 4 Jul 2025 18:10:27 -0500
Subject: [PATCH 14/25] symcheck: Improve diagnostics from spawned Cargo

Rather than printing the entire JSON dump, use the rendered version.
---
 .../crates/symbol-check/src/main.rs           | 29 ++++++++++++++-----
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/compiler-builtins/crates/symbol-check/src/main.rs b/compiler-builtins/crates/symbol-check/src/main.rs
index f60d4f0d36f86..1312a71797032 100644
--- a/compiler-builtins/crates/symbol-check/src/main.rs
+++ b/compiler-builtins/crates/symbol-check/src/main.rs
@@ -87,9 +87,14 @@ fn host_target() -> String {
 /// libraries.
 fn exec_cargo_with_args(target: &str, args: &[&str]) -> Vec<PathBuf> {
     let mut cmd = Command::new("cargo");
-    cmd.args(["build", "--target", target, "--message-format=json"])
-        .args(args)
-        .stdout(Stdio::piped());
+    cmd.args([
+        "build",
+        "--target",
+        target,
+        "--message-format=json-diagnostic-rendered-ansi",
+    ])
+    .args(args)
+    .stdout(Stdio::piped());
 
     println!("running: {cmd:?}");
     let mut child = cmd.spawn().expect("failed to launch Cargo");
@@ -100,11 +105,21 @@ fn exec_cargo_with_args(target: &str, args: &[&str]) -> Vec<PathBuf> {
 
     for line in reader.lines() {
         let line = line.expect("failed to read line");
-        println!("{line}"); // tee to stdout
-
-        // Select only steps that create files
         let j: Value = serde_json::from_str(&line).expect("failed to deserialize");
-        if j["reason"] != "compiler-artifact" {
+        let reason = &j["reason"];
+
+        // Forward output that is meant to be user-facing
+        if reason == "compiler-message" {
+            println!("{}", j["message"]["rendered"].as_str().unwrap());
+        } else if reason == "build-finished" {
+            println!("build finshed. success: {}", j["success"]);
+        } else if reason == "build-script-executed" {
+            let pretty = serde_json::to_string_pretty(&j).unwrap();
+            println!("build script output: {pretty}",);
+        }
+
+        // Only interested in the artifact list now
+        if reason != "compiler-artifact" {
             continue;
         }
 

From ac86ef8999b55104b18fa27e46f6f44bd6bafd2f Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 4 Jul 2025 19:30:31 -0500
Subject: [PATCH 15/25] Remove unused custom target JSON files

8521530f4938 ("Fix __divsi3 and __udivsi3 on thumbv6m targets") removed
tests that use these `thumb*-linux` target files in favor of tests that
use the `thumb*-none` targets, which are available via Rustup. The JSON
files haven't been used since then and are outdated, so remove them.
---
 compiler-builtins/thumbv6m-linux-eabi.json    | 28 -------------------
 compiler-builtins/thumbv7em-linux-eabi.json   | 27 ------------------
 compiler-builtins/thumbv7em-linux-eabihf.json | 28 -------------------
 compiler-builtins/thumbv7m-linux-eabi.json    | 27 ------------------
 4 files changed, 110 deletions(-)
 delete mode 100644 compiler-builtins/thumbv6m-linux-eabi.json
 delete mode 100644 compiler-builtins/thumbv7em-linux-eabi.json
 delete mode 100644 compiler-builtins/thumbv7em-linux-eabihf.json
 delete mode 100644 compiler-builtins/thumbv7m-linux-eabi.json

diff --git a/compiler-builtins/thumbv6m-linux-eabi.json b/compiler-builtins/thumbv6m-linux-eabi.json
deleted file mode 100644
index ac736eae686b4..0000000000000
--- a/compiler-builtins/thumbv6m-linux-eabi.json
+++ /dev/null
@@ -1,28 +0,0 @@
-{
-    "abi-blacklist": [
-        "stdcall",
-        "fastcall",
-        "vectorcall",
-        "win64",
-        "sysv64"
-    ],
-    "arch": "arm",
-    "data-layout": "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64",
-    "env": "",
-    "executables": true,
-    "features": "+strict-align",
-    "linker": "arm-none-eabi-gcc",
-    "linker-flavor": "gcc",
-    "llvm-target": "thumbv6m-none-eabi",
-    "max-atomic-width": 0,
-    "os": "linux",
-    "panic-strategy": "abort",
-    "pre-link-args": {
-        "gcc": ["-nostartfiles"]
-    },
-    "relocation-model": "static",
-    "target-endian": "little",
-    "target-pointer-width": "32",
-    "target-c-int-width": "32",
-    "vendor": ""
-}
diff --git a/compiler-builtins/thumbv7em-linux-eabi.json b/compiler-builtins/thumbv7em-linux-eabi.json
deleted file mode 100644
index b6d4a6bda7bac..0000000000000
--- a/compiler-builtins/thumbv7em-linux-eabi.json
+++ /dev/null
@@ -1,27 +0,0 @@
-{
-    "abi-blacklist": [
-        "stdcall",
-        "fastcall",
-        "vectorcall",
-        "win64",
-        "sysv64"
-    ],
-    "arch": "arm",
-    "data-layout": "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64",
-    "env": "",
-    "executables": true,
-    "linker": "arm-none-eabi-gcc",
-    "linker-flavor": "gcc",
-    "llvm-target": "thumbv7em-none-eabi",
-    "max-atomic-width": 32,
-    "os": "linux",
-    "panic-strategy": "abort",
-    "pre-link-args": {
-        "gcc": ["-nostartfiles"]
-    },
-    "relocation-model": "static",
-    "target-endian": "little",
-    "target-pointer-width": "32",
-    "target-c-int-width": "32",
-    "vendor": ""
-}
diff --git a/compiler-builtins/thumbv7em-linux-eabihf.json b/compiler-builtins/thumbv7em-linux-eabihf.json
deleted file mode 100644
index 81cfcd48d56ce..0000000000000
--- a/compiler-builtins/thumbv7em-linux-eabihf.json
+++ /dev/null
@@ -1,28 +0,0 @@
-{
-    "abi-blacklist": [
-        "stdcall",
-        "fastcall",
-        "vectorcall",
-        "win64",
-        "sysv64"
-    ],
-    "arch": "arm",
-    "data-layout": "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64",
-    "env": "",
-    "executables": true,
-    "features": "+vfp4,+d16,+fp-only-sp",
-    "linker": "arm-none-eabi-gcc",
-    "linker-flavor": "gcc",
-    "llvm-target": "thumbv7em-none-eabihf",
-    "max-atomic-width": 32,
-    "os": "linux",
-    "panic-strategy": "abort",
-    "pre-link-args": {
-        "gcc": ["-nostartfiles"]
-    },
-    "relocation-model": "static",
-    "target-endian": "little",
-    "target-pointer-width": "32",
-    "target-c-int-width": "32",
-    "vendor": ""
-}
diff --git a/compiler-builtins/thumbv7m-linux-eabi.json b/compiler-builtins/thumbv7m-linux-eabi.json
deleted file mode 100644
index abe037c5bef88..0000000000000
--- a/compiler-builtins/thumbv7m-linux-eabi.json
+++ /dev/null
@@ -1,27 +0,0 @@
-{
-    "abi-blacklist": [
-        "stdcall",
-        "fastcall",
-        "vectorcall",
-        "win64",
-        "sysv64"
-    ],
-    "arch": "arm",
-    "data-layout": "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64",
-    "env": "",
-    "executables": true,
-    "linker": "arm-none-eabi-gcc",
-    "linker-flavor": "gcc",
-    "llvm-target": "thumbv7m-none-eabi",
-    "max-atomic-width": 32,
-    "os": "linux",
-    "panic-strategy": "abort",
-    "pre-link-args": {
-        "gcc": ["-nostartfiles"]
-    },
-    "relocation-model": "static",
-    "target-endian": "little",
-    "target-pointer-width": "32",
-    "target-c-int-width": "32",
-    "vendor": ""
-}

From 9d4437f4b0360407733469b6de238c4991d90ec3 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 4 Jul 2025 19:42:18 -0500
Subject: [PATCH 16/25] Test building custom targets and resolve an issue
 probing `rustc`

The `rustc` probe done in our build scripts needs to pass `--target` to
get the correct configuration, which usually comes from the `TARGET`
environment variable. However, for targets specified via a `target.json`
file, `TARGET` gets set to the file name without an extension or path.
`rustc` will check a search path to attempt to locate the file, but this
is likely to fail since the directory where Cargo invokes build scripts
(and hence where those scripts invoke `rustc`) might not have any
relation to the JSON spec file.

Resolve this for now by leaving `f16` and `f128` disabled if the `rustc`
command fails. Result of the discussion at CARGO-14208 may eventually
provide a better solution.

A CI test is also added since custom JSON files are an edge case that
could fail in other ways. I verified this fails without the fix here.
The JSON file is the output for `thumbv7em-none-eabi`, just renamed so
`rustc` doesn't identify it.
---
 compiler-builtins/.github/workflows/main.yaml | 20 ++++++++++++++++
 .../compiler-builtins/configure.rs            | 13 ++++++++---
 .../etc/thumbv7em-none-eabi-renamed.json      | 23 +++++++++++++++++++
 compiler-builtins/libm/configure.rs           | 13 ++++++++---
 4 files changed, 63 insertions(+), 6 deletions(-)
 create mode 100644 compiler-builtins/etc/thumbv7em-none-eabi-renamed.json

diff --git a/compiler-builtins/.github/workflows/main.yaml b/compiler-builtins/.github/workflows/main.yaml
index 95b0962b08241..541c99c828dc0 100644
--- a/compiler-builtins/.github/workflows/main.yaml
+++ b/compiler-builtins/.github/workflows/main.yaml
@@ -195,6 +195,25 @@ jobs:
       run: ./ci/update-musl.sh
     - run: cargo clippy --workspace --all-targets
 
+  build-custom:
+    name: Build custom target
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      run: |
+        rustup update nightly --no-self-update
+        rustup default nightly
+        rustup component add rust-src
+    - uses: Swatinem/rust-cache@v2
+    - run: |
+        # Ensure we can build with custom target.json files (these can interact
+        # poorly with build scripts)
+        cargo build -p compiler_builtins -p libm \
+          --target etc/thumbv7em-none-eabi-renamed.json \
+          -Zbuild-std=core
+
   benchmarks:
     name: Benchmarks
     timeout-minutes: 20
@@ -331,6 +350,7 @@ jobs:
   success:
     needs:
       - benchmarks
+      - build-custom
       - clippy
       - extensive
       - miri
diff --git a/compiler-builtins/compiler-builtins/configure.rs b/compiler-builtins/compiler-builtins/configure.rs
index a1e45080e7106..9721ddf090c6f 100644
--- a/compiler-builtins/compiler-builtins/configure.rs
+++ b/compiler-builtins/compiler-builtins/configure.rs
@@ -45,9 +45,16 @@ impl Target {
         let out = cmd
             .output()
             .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
-        assert!(out.status.success(), "failed to run `{cmd:?}`");
         let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
 
+        // If we couldn't query `rustc` (e.g. a custom JSON target was used), make the safe
+        // choice and leave `f16` and `f128` disabled.
+        let rustc_output_ok = out.status.success();
+        let reliable_f128 =
+            rustc_output_ok && rustc_cfg.lines().any(|l| l == "target_has_reliable_f128");
+        let reliable_f16 =
+            rustc_output_ok && rustc_cfg.lines().any(|l| l == "target_has_reliable_f16");
+
         Self {
             triple,
             triple_split,
@@ -67,8 +74,8 @@ impl Target {
                 .split(",")
                 .map(ToOwned::to_owned)
                 .collect(),
-            reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
-            reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
+            reliable_f128,
+            reliable_f16,
         }
     }
 
diff --git a/compiler-builtins/etc/thumbv7em-none-eabi-renamed.json b/compiler-builtins/etc/thumbv7em-none-eabi-renamed.json
new file mode 100644
index 0000000000000..81273d44e4965
--- /dev/null
+++ b/compiler-builtins/etc/thumbv7em-none-eabi-renamed.json
@@ -0,0 +1,23 @@
+{
+  "abi": "eabi",
+  "arch": "arm",
+  "c-enum-min-bits": 8,
+  "crt-objects-fallback": "false",
+  "data-layout": "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64",
+  "emit-debug-gdb-scripts": false,
+  "frame-pointer": "always",
+  "linker": "rust-lld",
+  "linker-flavor": "gnu-lld",
+  "llvm-floatabi": "soft",
+  "llvm-target": "thumbv7em-none-eabi",
+  "max-atomic-width": 32,
+  "metadata": {
+    "description": "Bare ARMv7E-M",
+    "host_tools": false,
+    "std": false,
+    "tier": 2
+  },
+  "panic-strategy": "abort",
+  "relocation-model": "static",
+  "target-pointer-width": "32"
+}
diff --git a/compiler-builtins/libm/configure.rs b/compiler-builtins/libm/configure.rs
index 6562ecbe5db40..f9100d2d58b26 100644
--- a/compiler-builtins/libm/configure.rs
+++ b/compiler-builtins/libm/configure.rs
@@ -43,9 +43,16 @@ impl Config {
         let out = cmd
             .output()
             .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
-        assert!(out.status.success(), "failed to run `{cmd:?}`");
         let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
 
+        // If we couldn't query `rustc` (e.g. a custom JSON target was used), make the safe
+        // choice and leave `f16` and `f128` disabled.
+        let rustc_output_ok = out.status.success();
+        let reliable_f128 =
+            rustc_output_ok && rustc_cfg.lines().any(|l| l == "target_has_reliable_f128");
+        let reliable_f16 =
+            rustc_output_ok && rustc_cfg.lines().any(|l| l == "target_has_reliable_f16");
+
         Self {
             target_triple,
             manifest_dir: PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap()),
@@ -59,8 +66,8 @@ impl Config {
             target_string: env::var("TARGET").unwrap(),
             target_vendor: env::var("CARGO_CFG_TARGET_VENDOR").unwrap(),
             target_features,
-            reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
-            reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
+            reliable_f128,
+            reliable_f16,
         }
     }
 }

From 6d0d2d45179e255c106093738feb05159c6ad45d Mon Sep 17 00:00:00 2001
From: Oli Scherer <github333195615777966@oli-obk.de>
Date: Thu, 3 Jul 2025 09:14:56 +0000
Subject: [PATCH 17/25] Constify `Fn*` traits

---
 core/src/ops/function.rs | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/core/src/ops/function.rs b/core/src/ops/function.rs
index df48c104410ca..763b60d88e510 100644
--- a/core/src/ops/function.rs
+++ b/core/src/ops/function.rs
@@ -72,7 +72,8 @@ use crate::marker::Tuple;
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait Fn<Args: Tuple>: FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -159,7 +160,8 @@ pub trait Fn<Args: Tuple>: FnMut<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait FnMut<Args: Tuple>: FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -238,7 +240,8 @@ pub trait FnMut<Args: Tuple>: FnOnce<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-// FIXME(const_trait_impl) #[const_trait]
+#[const_trait]
+#[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
 pub trait FnOnce<Args: Tuple> {
     /// The returned type after the call operator is used.
     #[lang = "fn_once_output"]
@@ -254,9 +257,10 @@ mod impls {
     use crate::marker::Tuple;
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> Fn<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const Fn<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         extern "rust-call" fn call(&self, args: A) -> F::Output {
             (**self).call(args)
@@ -264,9 +268,10 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnMut<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnMut<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
             (**self).call(args)
@@ -274,9 +279,10 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnOnce<A> for &F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnOnce<A> for &F
     where
-        F: Fn<A>,
+        F: ~const Fn<A>,
     {
         type Output = F::Output;
 
@@ -286,9 +292,10 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnMut<A> for &mut F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnMut<A> for &mut F
     where
-        F: FnMut<A>,
+        F: ~const FnMut<A>,
     {
         extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
             (*self).call_mut(args)
@@ -296,9 +303,10 @@ mod impls {
     }
 
     #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A: Tuple, F: ?Sized> FnOnce<A> for &mut F
+    #[rustc_const_unstable(feature = "const_trait_impl", issue = "67792")]
+    impl<A: Tuple, F: ?Sized> const FnOnce<A> for &mut F
     where
-        F: FnMut<A>,
+        F: ~const FnMut<A>,
     {
         type Output = F::Output;
         extern "rust-call" fn call_once(self, args: A) -> F::Output {

From 1edc040b2d0a66dffdd180e13565e58e17e22790 Mon Sep 17 00:00:00 2001
From: Oli Scherer <github333195615777966@oli-obk.de>
Date: Tue, 8 Jul 2025 15:41:13 +0000
Subject: [PATCH 18/25] Remove `const_eval_select` hack

---
 core/src/intrinsics/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/intrinsics/mod.rs b/core/src/intrinsics/mod.rs
index 791d10eda6d0d..1ac0c7ff89b89 100644
--- a/core/src/intrinsics/mod.rs
+++ b/core/src/intrinsics/mod.rs
@@ -2279,7 +2279,7 @@ pub const fn const_eval_select<ARG: Tuple, F, G, RET>(
 ) -> RET
 where
     G: FnOnce<ARG, Output = RET>,
-    F: FnOnce<ARG, Output = RET>;
+    F: const FnOnce<ARG, Output = RET>;
 
 /// A macro to make it easier to invoke const_eval_select. Use as follows:
 /// ```rust,ignore (just a macro example)

From 8984877236567f34e9144adb716d890e65550cae Mon Sep 17 00:00:00 2001
From: George Tokmaji <tokmajigeorge@gmail.com>
Date: Tue, 8 Jul 2025 21:19:38 +0200
Subject: [PATCH 19/25] Win: Use exceptions with empty data for SEH panic
 exception copies instead of a new panic

For unwinding with SEH, we currently construct a C++ exception with the
panic data. Being a regular C++ exception, it interacts with the C++
exception handling machinery and can be retrieved via
`std::current_exception`, which needs to copy the exception. We can't
support that, so we panic, which throws another exception, which the
C++ runtime tries to copy and store into the exception_ptr, which panics
again, which causes the C++ runtime to store a `bad_exception` instance.

However, this doesn't work because the panics thrown by the copy
function will be dropped without being rethrown, and causes unnecessary
log spam in stderr. Fix this by directly throwing an exception without
data, which doesn't cause log spam and can be dropped without being
rethrown.
---
 panic_unwind/src/seh.rs | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/panic_unwind/src/seh.rs b/panic_unwind/src/seh.rs
index 003ac4f0cd37f..668e988abff39 100644
--- a/panic_unwind/src/seh.rs
+++ b/panic_unwind/src/seh.rs
@@ -61,6 +61,7 @@ struct Exception {
     // and its destructor is executed by the C++ runtime. When we take the Box
     // out of the exception, we need to leave the exception in a valid state
     // for its destructor to run without double-dropping the Box.
+    // We also construct this as None for copies of the exception.
     data: Option<Box<dyn Any + Send>>,
 }
 
@@ -264,7 +265,11 @@ static mut TYPE_DESCRIPTOR: _TypeDescriptor = _TypeDescriptor {
 // runtime under a try/catch block and the panic that we generate here will be
 // used as the result of the exception copy. This is used by the C++ runtime to
 // support capturing exceptions with std::exception_ptr, which we can't support
-// because Box<dyn Any> isn't clonable.
+// because Box<dyn Any> isn't clonable. Thus we throw an exception without data,
+// which the C++ runtime will attempt to copy, which will once again fail, and
+// a std::bad_exception instance ends up in the std::exception_ptr instance.
+// The lack of data doesn't matter because the exception will never be rethrown
+// - it is purely used to signal to the C++ runtime that copying failed.
 macro_rules! define_cleanup {
     ($abi:tt $abi2:tt) => {
         unsafe extern $abi fn exception_cleanup(e: *mut Exception) {
@@ -278,7 +283,9 @@ macro_rules! define_cleanup {
         unsafe extern $abi2 fn exception_copy(
             _dest: *mut Exception, _src: *mut Exception
         ) -> *mut Exception {
-            panic!("Rust panics cannot be copied");
+            unsafe {
+                throw_exception(None);
+            }
         }
     }
 }
@@ -291,6 +298,10 @@ cfg_if::cfg_if! {
 }
 
 pub(crate) unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
+    unsafe { throw_exception(Some(data)) }
+}
+
+unsafe fn throw_exception(data: Option<Box<dyn Any + Send>>) -> ! {
     use core::intrinsics::{AtomicOrdering, atomic_store};
 
     // _CxxThrowException executes entirely on this stack frame, so there's no
@@ -300,8 +311,7 @@ pub(crate) unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     // The ManuallyDrop is needed here since we don't want Exception to be
     // dropped when unwinding. Instead it will be dropped by exception_cleanup
     // which is invoked by the C++ runtime.
-    let mut exception =
-        ManuallyDrop::new(Exception { canary: (&raw const TYPE_DESCRIPTOR), data: Some(data) });
+    let mut exception = ManuallyDrop::new(Exception { canary: (&raw const TYPE_DESCRIPTOR), data });
     let throw_ptr = (&raw mut exception) as *mut _;
 
     // This... may seems surprising, and justifiably so. On 32-bit MSVC the

From 3dfa197a269b35870398f707bd095606c2135902 Mon Sep 17 00:00:00 2001
From: Moulins <arthur.heuillard@orange.fr>
Date: Tue, 8 Jul 2025 21:10:40 +0200
Subject: [PATCH 20/25] docs: document trait upcasting rules in `Unsize` trait

---
 core/src/marker.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/core/src/marker.rs b/core/src/marker.rs
index 2aeb0b0c31e46..f092916eb8c1c 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -210,6 +210,11 @@ pub trait PointeeSized {
 ///   - `Trait` is dyn-compatible[^1].
 ///   - The type is sized.
 ///   - The type outlives `'a`.
+/// - Trait objects `dyn TraitA + AutoA... + 'a` implement `Unsize<dyn TraitB + AutoB... + 'b>`
+///    if all of these conditions are met:
+///   - `TraitB` is a supertrait of `TraitA`.
+///   - `AutoB...` is a subset of `AutoA...`.
+///   - `'a` outlives `'b`.
 /// - Structs `Foo<..., T1, ..., Tn, ...>` implement `Unsize<Foo<..., U1, ..., Un, ...>>`
 /// where any number of (type and const) parameters may be changed if all of these conditions
 /// are met:

From b51e7ec29a8378fa9a86f440e4ddbce5ff052319 Mon Sep 17 00:00:00 2001
From: Josh Stone <jistone@redhat.com>
Date: Tue, 8 Jul 2025 16:38:35 -0700
Subject: [PATCH 21/25] Disable docs for `compiler-builtins` and `sysroot`

Bootstrap already had a manual doc filter for the `sysroot` crate, but
other library crates keep themselves out of the public docs by setting
`[lib] doc = false` in their manifest. This seems like a better solution
to hide `compiler-builtins` docs, and removes the `sysroot` hack too.
---
 compiler-builtins/compiler-builtins/Cargo.toml | 2 ++
 sysroot/Cargo.toml                             | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/compiler-builtins/compiler-builtins/Cargo.toml b/compiler-builtins/compiler-builtins/Cargo.toml
index c5446cd76e326..3ccb05f73fb84 100644
--- a/compiler-builtins/compiler-builtins/Cargo.toml
+++ b/compiler-builtins/compiler-builtins/Cargo.toml
@@ -19,6 +19,8 @@ links = "compiler-rt"
 bench = false
 doctest = false
 test = false
+# make sure this crate isn't included in public standard library docs
+doc = false
 
 [dependencies]
 core = { path = "../../core", optional = true }
diff --git a/sysroot/Cargo.toml b/sysroot/Cargo.toml
index 3adc022497167..514728887fbca 100644
--- a/sysroot/Cargo.toml
+++ b/sysroot/Cargo.toml
@@ -5,6 +5,10 @@ name = "sysroot"
 version = "0.0.0"
 edition = "2024"
 
+[lib]
+# make sure this crate isn't included in public standard library docs
+doc = false
+
 # this is a dummy crate to ensure that all required crates appear in the sysroot
 [dependencies]
 proc_macro = { path = "../proc_macro", public = true }

From 27b11c81a2bbb45aa82724b009703a02d92a3235 Mon Sep 17 00:00:00 2001
From: B I Mohammed Abbas <bimohammadabbas@gmail.com>
Date: Wed, 9 Jul 2025 09:54:08 +0530
Subject: [PATCH 22/25] Fix VxWorks build errors

---
 std/src/sys/fs/unix.rs         | 1 -
 std/src/sys/pal/unix/thread.rs | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/std/src/sys/fs/unix.rs b/std/src/sys/fs/unix.rs
index dc278274f00f4..b310db2dac485 100644
--- a/std/src/sys/fs/unix.rs
+++ b/std/src/sys/fs/unix.rs
@@ -1491,7 +1491,6 @@ impl File {
             target_os = "redox",
             target_os = "espidf",
             target_os = "horizon",
-            target_os = "vxworks",
             target_os = "nuttx",
         )))]
         let to_timespec = |time: Option<SystemTime>| match time {
diff --git a/std/src/sys/pal/unix/thread.rs b/std/src/sys/pal/unix/thread.rs
index 53f0d1eeda5bf..e4f5520d8a33e 100644
--- a/std/src/sys/pal/unix/thread.rs
+++ b/std/src/sys/pal/unix/thread.rs
@@ -222,7 +222,7 @@ impl Thread {
 
     #[cfg(target_os = "vxworks")]
     pub fn set_name(name: &CStr) {
-        let mut name = truncate_cstr::<{ libc::VX_TASK_RENAME_LENGTH - 1 }>(name);
+        let mut name = truncate_cstr::<{ (libc::VX_TASK_RENAME_LENGTH - 1) as usize }>(name);
         let res = unsafe { libc::taskNameSet(libc::taskIdSelf(), name.as_mut_ptr()) };
         debug_assert_eq!(res, libc::OK);
     }

From a53271a4942e987b7fbd569c6c5eb37b12e50a2c Mon Sep 17 00:00:00 2001
From: Oli Scherer <github333195615777966@oli-obk.de>
Date: Wed, 12 Mar 2025 10:26:37 +0000
Subject: [PATCH 23/25] Add opaque TypeId handles for CTFE

---
 core/Cargo.toml            |  2 -
 core/src/any.rs            | 84 ++++++++++++++++++++++++++------------
 core/src/intrinsics/mod.rs | 15 ++++++-
 coretests/tests/any.rs     |  8 ----
 std/Cargo.toml             |  2 -
 sysroot/Cargo.toml         |  1 -
 6 files changed, 71 insertions(+), 41 deletions(-)

diff --git a/core/Cargo.toml b/core/Cargo.toml
index f88661ee00151..3e34e03a61e91 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -23,8 +23,6 @@ optimize_for_size = []
 # Make `RefCell` store additional debugging information, which is printed out when
 # a borrow error occurs
 debug_refcell = []
-# Make `TypeId` store a reference to the name of the type, so that it can print that name.
-debug_typeid = []
 
 [lints.rust.unexpected_cfgs]
 level = "warn"
diff --git a/core/src/any.rs b/core/src/any.rs
index 01dce114592a1..39cdf6efda07a 100644
--- a/core/src/any.rs
+++ b/core/src/any.rs
@@ -707,19 +707,52 @@ impl dyn Any + Send + Sync {
 /// ```
 #[derive(Clone, Copy, Eq, PartialOrd, Ord)]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[lang = "type_id"]
 pub struct TypeId {
-    // We avoid using `u128` because that imposes higher alignment requirements on many platforms.
-    // See issue #115620 for more information.
-    t: (u64, u64),
-    #[cfg(feature = "debug_typeid")]
-    name: &'static str,
+    /// This needs to be an array of pointers, since there is provenance
+    /// in the first array field. This provenance knows exactly which type
+    /// the TypeId actually is, allowing CTFE and miri to operate based off it.
+    /// At runtime all the pointers in the array contain bits of the hash, making
+    /// the entire `TypeId` actually just be a `u128` hash of the type.
+    pub(crate) data: [*const (); 16 / size_of::<*const ()>()],
 }
 
+// SAFETY: the raw pointer is always an integer
 #[stable(feature = "rust1", since = "1.0.0")]
-impl PartialEq for TypeId {
+unsafe impl Send for TypeId {}
+// SAFETY: the raw pointer is always an integer
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl Sync for TypeId {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
+impl const PartialEq for TypeId {
     #[inline]
     fn eq(&self, other: &Self) -> bool {
-        self.t == other.t
+        #[cfg(miri)]
+        return crate::intrinsics::type_id_eq(*self, *other);
+        #[cfg(not(miri))]
+        {
+            let this = self;
+            crate::intrinsics::const_eval_select!(
+                @capture { this: &TypeId, other: &TypeId } -> bool:
+                if const {
+                    crate::intrinsics::type_id_eq(*this, *other)
+                } else {
+                    // Ideally we would just invoke `type_id_eq` unconditionally here,
+                    // but since we do not MIR inline intrinsics, because backends
+                    // may want to override them (and miri does!), MIR opts do not
+                    // clean up this call sufficiently for LLVM to turn repeated calls
+                    // of `TypeId` comparisons against one specific `TypeId` into
+                    // a lookup table.
+                    // SAFETY: We know that at runtime none of the bits have provenance and all bits
+                    // are initialized. So we can just convert the whole thing to a `u128` and compare that.
+                    unsafe {
+                        crate::mem::transmute::<_, u128>(*this) == crate::mem::transmute::<_, u128>(*other)
+                    }
+                }
+            )
+        }
     }
 }
 
@@ -742,19 +775,19 @@ impl TypeId {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
     pub const fn of<T: ?Sized + 'static>() -> TypeId {
-        let t: u128 = const { intrinsics::type_id::<T>() };
-        let t1 = (t >> 64) as u64;
-        let t2 = t as u64;
-
-        TypeId {
-            t: (t1, t2),
-            #[cfg(feature = "debug_typeid")]
-            name: type_name::<T>(),
-        }
+        const { intrinsics::type_id::<T>() }
     }
 
     fn as_u128(self) -> u128 {
-        u128::from(self.t.0) << 64 | u128::from(self.t.1)
+        let mut bytes = [0; 16];
+
+        // This is a provenance-stripping memcpy.
+        for (i, chunk) in self.data.iter().copied().enumerate() {
+            let chunk = chunk.expose_provenance().to_ne_bytes();
+            let start = i * chunk.len();
+            bytes[start..(start + chunk.len())].copy_from_slice(&chunk);
+        }
+        u128::from_ne_bytes(bytes)
     }
 }
 
@@ -774,22 +807,19 @@ impl hash::Hash for TypeId {
         // - It is correct to do so -- only hashing a subset of `self` is still
         //   compatible with an `Eq` implementation that considers the entire
         //   value, as ours does.
-        self.t.1.hash(state);
+        let data =
+        // SAFETY: The `offset` stays in-bounds, it just moves the pointer to the 2nd half of the `TypeId`.
+        // Only the first ptr-sized chunk ever has provenance, so that second half is always
+        // fine to read at integer type.
+            unsafe { crate::ptr::read_unaligned(self.data.as_ptr().cast::<u64>().offset(1)) };
+        data.hash(state);
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for TypeId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        #[cfg(feature = "debug_typeid")]
-        {
-            write!(f, "TypeId({:#034x} = {})", self.as_u128(), self.name)?;
-        }
-        #[cfg(not(feature = "debug_typeid"))]
-        {
-            write!(f, "TypeId({:#034x})", self.as_u128())?;
-        }
-        Ok(())
+        write!(f, "TypeId({:#034x})", self.as_u128())
     }
 }
 
diff --git a/core/src/intrinsics/mod.rs b/core/src/intrinsics/mod.rs
index 791d10eda6d0d..f5dcfeebed8fa 100644
--- a/core/src/intrinsics/mod.rs
+++ b/core/src/intrinsics/mod.rs
@@ -2724,7 +2724,20 @@ pub const fn type_name<T: ?Sized>() -> &'static str;
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic]
-pub const fn type_id<T: ?Sized + 'static>() -> u128;
+pub const fn type_id<T: ?Sized + 'static>() -> crate::any::TypeId;
+
+/// Tests (at compile-time) if two [`crate::any::TypeId`] instances identify the
+/// same type. This is necessary because at const-eval time the actual discriminating
+/// data is opaque and cannot be inspected directly.
+///
+/// The stabilized version of this intrinsic is the [PartialEq] impl for [`core::any::TypeId`].
+#[rustc_nounwind]
+#[unstable(feature = "core_intrinsics", issue = "none")]
+#[rustc_intrinsic]
+#[rustc_do_not_const_check]
+pub const fn type_id_eq(a: crate::any::TypeId, b: crate::any::TypeId) -> bool {
+    a.data == b.data
+}
 
 /// Lowers in MIR to `Rvalue::Aggregate` with `AggregateKind::RawPtr`.
 ///
diff --git a/coretests/tests/any.rs b/coretests/tests/any.rs
index 117ef0042380d..25002617d0bbd 100644
--- a/coretests/tests/any.rs
+++ b/coretests/tests/any.rs
@@ -118,14 +118,6 @@ fn any_unsized() {
     is_any::<[i32]>();
 }
 
-#[cfg(feature = "debug_typeid")]
-#[test]
-fn debug_typeid_includes_name() {
-    let type_id = TypeId::of::<[usize; 2]>();
-    let debug_str = format!("{type_id:?}");
-    assert!(debug_str.ends_with("= [usize; 2])"), "{debug_str:?} did not match");
-}
-
 #[test]
 fn distinct_type_names() {
     // https://github.com/rust-lang/rust/issues/84666
diff --git a/std/Cargo.toml b/std/Cargo.toml
index 3a75d3168713f..62ece4b696199 100644
--- a/std/Cargo.toml
+++ b/std/Cargo.toml
@@ -113,8 +113,6 @@ optimize_for_size = ["core/optimize_for_size", "alloc/optimize_for_size"]
 # Make `RefCell` store additional debugging information, which is printed out when
 # a borrow error occurs
 debug_refcell = ["core/debug_refcell"]
-# Make `TypeId` store a reference to the name of the type, so that it can print that name.
-debug_typeid = ["core/debug_typeid"]
 
 
 # Enable std_detect default features for stdarch/crates/std_detect:
diff --git a/sysroot/Cargo.toml b/sysroot/Cargo.toml
index 3adc022497167..c4937c36d4c9c 100644
--- a/sysroot/Cargo.toml
+++ b/sysroot/Cargo.toml
@@ -22,7 +22,6 @@ compiler-builtins-no-asm = ["std/compiler-builtins-no-asm"]
 compiler-builtins-no-f16-f128 = ["std/compiler-builtins-no-f16-f128"]
 compiler-builtins-mangled-names = ["std/compiler-builtins-mangled-names"]
 debug_refcell = ["std/debug_refcell"]
-debug_typeid = ["std/debug_typeid"]
 llvm-libunwind = ["std/llvm-libunwind"]
 system-llvm-libunwind = ["std/system-llvm-libunwind"]
 optimize_for_size = ["std/optimize_for_size"]

From cd8bab4ab23a34bdb3b744d1eac95b89112c7d39 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Sun, 29 Jun 2025 11:40:59 +0800
Subject: [PATCH 24/25] Remove uncessary parens in closure body with unused
 lint

---
 core/src/unicode/unicode_data.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/unicode/unicode_data.rs b/core/src/unicode/unicode_data.rs
index 25b9c6e0e0e94..b57234bbee9a2 100644
--- a/core/src/unicode/unicode_data.rs
+++ b/core/src/unicode/unicode_data.rs
@@ -82,7 +82,7 @@ unsafe fn skip_search<const SOR: usize, const OFFSETS: usize>(
     let needle = needle as u32;
 
     let last_idx =
-        match short_offset_runs.binary_search_by_key(&(needle << 11), |header| (header.0 << 11)) {
+        match short_offset_runs.binary_search_by_key(&(needle << 11), |header| header.0 << 11) {
             Ok(idx) => idx + 1,
             Err(idx) => idx,
         };

From 17be5de59aa13ddb7ab9a0ad186a0b21983f1aa4 Mon Sep 17 00:00:00 2001
From: Roger Curley <rocurley@gmail.com>
Date: Thu, 3 Jul 2025 15:18:57 -0400
Subject: [PATCH 25/25] Refactor nan tests

---
 coretests/tests/floats/f128.rs | 14 --------------
 coretests/tests/floats/f16.rs  | 14 --------------
 coretests/tests/floats/f32.rs  | 14 --------------
 coretests/tests/floats/f64.rs  | 14 --------------
 coretests/tests/floats/mod.rs  | 23 +++++++++++++++++++++++
 5 files changed, 23 insertions(+), 56 deletions(-)

diff --git a/coretests/tests/floats/f128.rs b/coretests/tests/floats/f128.rs
index cf78e8796a030..38df09a91c103 100644
--- a/coretests/tests/floats/f128.rs
+++ b/coretests/tests/floats/f128.rs
@@ -55,20 +55,6 @@ fn test_num_f128() {
 // FIXME(f16_f128,miri): many of these have to be disabled since miri does not yet support
 // the intrinsics.
 
-#[test]
-fn test_nan() {
-    let nan: f128 = f128::NAN;
-    assert!(nan.is_nan());
-    assert!(!nan.is_infinite());
-    assert!(!nan.is_finite());
-    assert!(nan.is_sign_positive());
-    assert!(!nan.is_sign_negative());
-    assert!(!nan.is_normal());
-    assert_eq!(Fp::Nan, nan.classify());
-    // Ensure the quiet bit is set.
-    assert!(nan.to_bits() & (1 << (f128::MANTISSA_DIGITS - 2)) != 0);
-}
-
 #[test]
 fn test_infinity() {
     let inf: f128 = f128::INFINITY;
diff --git a/coretests/tests/floats/f16.rs b/coretests/tests/floats/f16.rs
index 9e91b654304b6..f6749d796cca9 100644
--- a/coretests/tests/floats/f16.rs
+++ b/coretests/tests/floats/f16.rs
@@ -51,20 +51,6 @@ fn test_num_f16() {
 // FIXME(f16_f128,miri): many of these have to be disabled since miri does not yet support
 // the intrinsics.
 
-#[test]
-fn test_nan() {
-    let nan: f16 = f16::NAN;
-    assert!(nan.is_nan());
-    assert!(!nan.is_infinite());
-    assert!(!nan.is_finite());
-    assert!(nan.is_sign_positive());
-    assert!(!nan.is_sign_negative());
-    assert!(!nan.is_normal());
-    assert_eq!(Fp::Nan, nan.classify());
-    // Ensure the quiet bit is set.
-    assert!(nan.to_bits() & (1 << (f16::MANTISSA_DIGITS - 2)) != 0);
-}
-
 #[test]
 fn test_infinity() {
     let inf: f16 = f16::INFINITY;
diff --git a/coretests/tests/floats/f32.rs b/coretests/tests/floats/f32.rs
index d2724d12e3927..f5d5723fea455 100644
--- a/coretests/tests/floats/f32.rs
+++ b/coretests/tests/floats/f32.rs
@@ -35,20 +35,6 @@ fn test_num_f32() {
     super::test_num(10f32, 2f32);
 }
 
-#[test]
-fn test_nan() {
-    let nan: f32 = f32::NAN;
-    assert!(nan.is_nan());
-    assert!(!nan.is_infinite());
-    assert!(!nan.is_finite());
-    assert!(!nan.is_normal());
-    assert!(nan.is_sign_positive());
-    assert!(!nan.is_sign_negative());
-    assert_eq!(Fp::Nan, nan.classify());
-    // Ensure the quiet bit is set.
-    assert!(nan.to_bits() & (1 << (f32::MANTISSA_DIGITS - 2)) != 0);
-}
-
 #[test]
 fn test_infinity() {
     let inf: f32 = f32::INFINITY;
diff --git a/coretests/tests/floats/f64.rs b/coretests/tests/floats/f64.rs
index b2b2393a5279c..34af87c241e91 100644
--- a/coretests/tests/floats/f64.rs
+++ b/coretests/tests/floats/f64.rs
@@ -30,20 +30,6 @@ fn test_num_f64() {
     super::test_num(10f64, 2f64);
 }
 
-#[test]
-fn test_nan() {
-    let nan: f64 = f64::NAN;
-    assert!(nan.is_nan());
-    assert!(!nan.is_infinite());
-    assert!(!nan.is_finite());
-    assert!(!nan.is_normal());
-    assert!(nan.is_sign_positive());
-    assert!(!nan.is_sign_negative());
-    assert_eq!(Fp::Nan, nan.classify());
-    // Ensure the quiet bit is set.
-    assert!(nan.to_bits() & (1 << (f64::MANTISSA_DIGITS - 2)) != 0);
-}
-
 #[test]
 fn test_infinity() {
     let inf: f64 = f64::INFINITY;
diff --git a/coretests/tests/floats/mod.rs b/coretests/tests/floats/mod.rs
index 6b4f586fa9b6b..36743a7d6df9e 100644
--- a/coretests/tests/floats/mod.rs
+++ b/coretests/tests/floats/mod.rs
@@ -1,4 +1,5 @@
 use std::fmt;
+use std::num::FpCategory as Fp;
 use std::ops::{Add, Div, Mul, Rem, Sub};
 
 /// Set the default tolerance for float comparison based on the type.
@@ -187,6 +188,8 @@ macro_rules! float_test {
             mod const_ {
                 #[allow(unused)]
                 use super::Approx;
+                #[allow(unused)]
+                use std::num::FpCategory as Fp;
                 // Shadow the runtime versions of the macro with const-compatible versions.
                 #[allow(unused)]
                 use $crate::floats::{
@@ -250,6 +253,26 @@ mod f16;
 mod f32;
 mod f64;
 
+float_test! {
+    name: nan,
+    attrs: {
+        f16: #[cfg(any(miri, target_has_reliable_f16))],
+        f128: #[cfg(any(miri, target_has_reliable_f128))],
+    },
+    test<Float> {
+        let nan: Float = Float::NAN;
+        assert!(nan.is_nan());
+        assert!(!nan.is_infinite());
+        assert!(!nan.is_finite());
+        assert!(!nan.is_normal());
+        assert!(nan.is_sign_positive());
+        assert!(!nan.is_sign_negative());
+        assert!(matches!(nan.classify(), Fp::Nan));
+        // Ensure the quiet bit is set.
+        assert!(nan.to_bits() & (1 << (Float::MANTISSA_DIGITS - 2)) != 0);
+    }
+}
+
 float_test! {
     name: min,
     attrs: {