Merge pull request #2313 from jieyouxu/rustc-pull

Rustc pull

17 files changed, 444 insertions, 235 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/apple.rs b/compiler/rustc_codegen_ssa/src/back/apple.rs
index bfa7635a869..2c8b0ec418d 100644
--- a/compiler/rustc_codegen_ssa/src/back/apple.rs
+++ b/compiler/rustc_codegen_ssa/src/back/apple.rs
@@ -1,16 +1,40 @@
 use std::env;
+use std::ffi::OsString;
 use std::fmt::{Display, from_fn};
 use std::num::ParseIntError;
+use std::path::PathBuf;
+use std::process::Command;
 
+use itertools::Itertools;
 use rustc_middle::middle::exported_symbols::SymbolExportKind;
 use rustc_session::Session;
 use rustc_target::spec::Target;
+use tracing::debug;
 
-use crate::errors::AppleDeploymentTarget;
+use crate::errors::{AppleDeploymentTarget, XcrunError, XcrunSdkPathWarning};
+use crate::fluent_generated as fluent;
 
 #[cfg(test)]
 mod tests;
 
+/// The canonical name of the desired SDK for a given target.
+pub(super) fn sdk_name(target: &Target) -> &'static str {
+    match (&*target.os, &*target.abi) {
+        ("macos", "") => "MacOSX",
+        ("ios", "") => "iPhoneOS",
+        ("ios", "sim") => "iPhoneSimulator",
+        // Mac Catalyst uses the macOS SDK
+        ("ios", "macabi") => "MacOSX",
+        ("tvos", "") => "AppleTVOS",
+        ("tvos", "sim") => "AppleTVSimulator",
+        ("visionos", "") => "XROS",
+        ("visionos", "sim") => "XRSimulator",
+        ("watchos", "") => "WatchOS",
+        ("watchos", "sim") => "WatchSimulator",
+        (os, abi) => unreachable!("invalid os '{os}' / abi '{abi}' combination for Apple target"),
+    }
+}
+
 pub(super) fn macho_platform(target: &Target) -> u32 {
     match (&*target.os, &*target.abi) {
         ("macos", _) => object::macho::PLATFORM_MACOS,
@@ -253,3 +277,131 @@ pub(super) fn add_version_to_llvm_target(
         format!("{arch}-{vendor}-{os}{major}.{minor}.{patch}")
     }
 }
+
+pub(super) fn get_sdk_root(sess: &Session) -> Option<PathBuf> {
+    let sdk_name = sdk_name(&sess.target);
+
+    match xcrun_show_sdk_path(sdk_name, sess.verbose_internals()) {
+        Ok((path, stderr)) => {
+            // Emit extra stderr, such as if `-verbose` was passed, or if `xcrun` emitted a warning.
+            if !stderr.is_empty() {
+                sess.dcx().emit_warn(XcrunSdkPathWarning { sdk_name, stderr });
+            }
+            Some(path)
+        }
+        Err(err) => {
+            let mut diag = sess.dcx().create_err(err);
+
+            // Recognize common error cases, and give more Rust-specific error messages for those.
+            if let Some(developer_dir) = xcode_select_developer_dir() {
+                diag.arg("developer_dir", &developer_dir);
+                diag.note(fluent::codegen_ssa_xcrun_found_developer_dir);
+                if developer_dir.as_os_str().to_string_lossy().contains("CommandLineTools") {
+                    if sdk_name != "MacOSX" {
+                        diag.help(fluent::codegen_ssa_xcrun_command_line_tools_insufficient);
+                    }
+                }
+            } else {
+                diag.help(fluent::codegen_ssa_xcrun_no_developer_dir);
+            }
+
+            diag.emit();
+            None
+        }
+    }
+}
+
+/// Invoke `xcrun --sdk $sdk_name --show-sdk-path` to get the SDK path.
+///
+/// The exact logic that `xcrun` uses is unspecified (see `man xcrun` for a few details), and may
+/// change between macOS and Xcode versions, but it roughly boils down to finding the active
+/// developer directory, and then invoking `xcodebuild -sdk $sdk_name -version` to get the SDK
+/// details.
+///
+/// Finding the developer directory is roughly done by looking at, in order:
+/// - The `DEVELOPER_DIR` environment variable.
+/// - The `/var/db/xcode_select_link` symlink (set by `xcode-select --switch`).
+/// - `/Applications/Xcode.app` (hardcoded fallback path).
+/// - `/Library/Developer/CommandLineTools` (hardcoded fallback path).
+///
+/// Note that `xcrun` caches its result, but with a cold cache this whole operation can be quite
+/// slow, especially so the first time it's run after a reboot.
+fn xcrun_show_sdk_path(
+    sdk_name: &'static str,
+    verbose: bool,
+) -> Result<(PathBuf, String), XcrunError> {
+    let mut cmd = Command::new("xcrun");
+    if verbose {
+        cmd.arg("--verbose");
+    }
+    // The `--sdk` parameter is the same as in xcodebuild, namely either an absolute path to an SDK,
+    // or the (lowercase) canonical name of an SDK.
+    cmd.arg("--sdk");
+    cmd.arg(&sdk_name.to_lowercase());
+    cmd.arg("--show-sdk-path");
+
+    // We do not stream stdout/stderr lines directly to the user, since whether they are warnings or
+    // errors depends on the status code at the end.
+    let output = cmd.output().map_err(|error| XcrunError::FailedInvoking {
+        sdk_name,
+        command_formatted: format!("{cmd:?}"),
+        error,
+    })?;
+
+    // It is fine to do lossy conversion here, non-UTF-8 paths are quite rare on macOS nowadays
+    // (only possible with the HFS+ file system), and we only use it for error messages.
+    let stderr = String::from_utf8_lossy_owned(output.stderr);
+    if !stderr.is_empty() {
+        debug!(stderr, "original xcrun stderr");
+    }
+
+    // Some versions of `xcodebuild` output beefy errors when invoked via `xcrun`,
+    // but these are usually red herrings.
+    let stderr = stderr
+        .lines()
+        .filter(|line| {
+            !line.contains("Writing error result bundle")
+                && !line.contains("Requested but did not find extension point with identifier")
+        })
+        .join("\n");
+
+    if output.status.success() {
+        Ok((stdout_to_path(output.stdout), stderr))
+    } else {
+        // Output both stdout and stderr, since shims of `xcrun` (such as the one provided by
+        // nixpkgs), do not always use stderr for errors.
+        let stdout = String::from_utf8_lossy_owned(output.stdout).trim().to_string();
+        Err(XcrunError::Unsuccessful {
+            sdk_name,
+            command_formatted: format!("{cmd:?}"),
+            stdout,
+            stderr,
+        })
+    }
+}
+
+/// Invoke `xcode-select --print-path`, and return the current developer directory.
+///
+/// NOTE: We don't do any error handling here, this is only used as a canary in diagnostics (`xcrun`
+/// will have already emitted the relevant error information).
+fn xcode_select_developer_dir() -> Option<PathBuf> {
+    let mut cmd = Command::new("xcode-select");
+    cmd.arg("--print-path");
+    let output = cmd.output().ok()?;
+    if !output.status.success() {
+        return None;
+    }
+    Some(stdout_to_path(output.stdout))
+}
+
+fn stdout_to_path(mut stdout: Vec<u8>) -> PathBuf {
+    // Remove trailing newline.
+    if let Some(b'\n') = stdout.last() {
+        let _ = stdout.pop().unwrap();
+    }
+    #[cfg(unix)]
+    let path = <OsString as std::os::unix::ffi::OsStringExt>::from_vec(stdout);
+    #[cfg(not(unix))] // Unimportant, this is only used on macOS
+    let path = OsString::from(String::from_utf8(stdout).unwrap());
+    PathBuf::from(path)
+}
diff --git a/compiler/rustc_codegen_ssa/src/back/apple/tests.rs b/compiler/rustc_codegen_ssa/src/back/apple/tests.rs
index 7ccda5a8190..8df740a4bcf 100644
--- a/compiler/rustc_codegen_ssa/src/back/apple/tests.rs
+++ b/compiler/rustc_codegen_ssa/src/back/apple/tests.rs
@@ -1,4 +1,4 @@
-use super::{add_version_to_llvm_target, parse_version};
+use super::*;
 
 #[test]
 fn test_add_version_to_llvm_target() {
@@ -19,3 +19,69 @@ fn test_parse_version() {
     assert_eq!(parse_version("10.12.6"), Ok((10, 12, 6)));
     assert_eq!(parse_version("9999.99.99"), Ok((9999, 99, 99)));
 }
+
+#[test]
+#[cfg_attr(not(target_os = "macos"), ignore = "xcode-select is only available on macOS")]
+fn lookup_developer_dir() {
+    let _developer_dir = xcode_select_developer_dir().unwrap();
+}
+
+#[test]
+#[cfg_attr(not(target_os = "macos"), ignore = "xcrun is only available on macOS")]
+fn lookup_sdk() {
+    let (sdk_path, stderr) = xcrun_show_sdk_path("MacOSX", false).unwrap();
+    // Check that the found SDK is valid.
+    assert!(sdk_path.join("SDKSettings.plist").exists());
+    assert_eq!(stderr, "");
+
+    // Test that the SDK root is a subdir of the developer directory.
+    if let Some(developer_dir) = xcode_select_developer_dir() {
+        // Only run this test if SDKROOT is not set (otherwise xcrun may look up via. that).
+        if std::env::var_os("SDKROOT").is_some() {
+            assert!(sdk_path.starts_with(&developer_dir));
+        }
+    }
+}
+
+#[test]
+#[cfg_attr(not(target_os = "macos"), ignore = "xcrun is only available on macOS")]
+fn lookup_sdk_verbose() {
+    let (_, stderr) = xcrun_show_sdk_path("MacOSX", true).unwrap();
+    // Newer xcrun versions should emit something like this:
+    //
+    //     xcrun: note: looking up SDK with 'xcodebuild -sdk macosx -version Path'
+    //     xcrun: note: xcrun_db = '/var/.../xcrun_db'
+    //     xcrun: note: lookup resolved to: '...'
+    //     xcrun: note: database key is: ...
+    //
+    // Or if the value is already cached, something like this:
+    //
+    //     xcrun: note: database key is: ...
+    //     xcrun: note: lookup resolved in '/var/.../xcrun_db' : '...'
+    assert!(
+        stderr.contains("xcrun: note: lookup resolved"),
+        "stderr should contain lookup note: {stderr}",
+    );
+}
+
+#[test]
+#[cfg_attr(not(target_os = "macos"), ignore = "xcrun is only available on macOS")]
+fn try_lookup_invalid_sdk() {
+    // As a proxy for testing all the different ways that `xcrun` can fail,
+    // test the case where an SDK was not found.
+    let err = xcrun_show_sdk_path("invalid", false).unwrap_err();
+    let XcrunError::Unsuccessful { stderr, .. } = err else {
+        panic!("unexpected error kind: {err:?}");
+    };
+    // Either one of (depending on if using Command Line Tools or full Xcode):
+    // xcrun: error: SDK "invalid" cannot be located
+    // xcodebuild: error: SDK "invalid" cannot be located.
+    assert!(
+        stderr.contains(r#"error: SDK "invalid" cannot be located"#),
+        "stderr should contain xcodebuild note: {stderr}",
+    );
+    assert!(
+        stderr.contains("xcrun: error: unable to lookup item 'Path' in SDK 'invalid'"),
+        "stderr should contain xcrun note: {stderr}",
+    );
+}
diff --git a/compiler/rustc_codegen_ssa/src/back/archive.rs b/compiler/rustc_codegen_ssa/src/back/archive.rs
index 60af462b6b6..34c84c64070 100644
--- a/compiler/rustc_codegen_ssa/src/back/archive.rs
+++ b/compiler/rustc_codegen_ssa/src/back/archive.rs
@@ -389,11 +389,10 @@ impl<'a> ArchiveBuilder for ArArchiveBuilder<'a> {
         mut skip: Box<dyn FnMut(&str) -> bool + 'static>,
     ) -> io::Result<()> {
         let mut archive_path = archive_path.to_path_buf();
-        if self.sess.target.llvm_target.contains("-apple-macosx") {
-            if let Some(new_archive_path) = try_extract_macho_fat_archive(self.sess, &archive_path)?
-            {
-                archive_path = new_archive_path
-            }
+        if self.sess.target.llvm_target.contains("-apple-macosx")
+            && let Some(new_archive_path) = try_extract_macho_fat_archive(self.sess, &archive_path)?
+        {
+            archive_path = new_archive_path
         }
 
         if self.src_archives.iter().any(|archive| archive.0 == archive_path) {
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 5f85c10636e..7d411087241 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -151,17 +151,17 @@ pub fn link_binary(
                 sess.dcx().emit_artifact_notification(&out_filename, "link");
             }
 
-            if sess.prof.enabled() {
-                if let Some(artifact_name) = out_filename.file_name() {
-                    // Record size for self-profiling
-                    let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
-
-                    sess.prof.artifact_size(
-                        "linked_artifact",
-                        artifact_name.to_string_lossy(),
-                        file_size,
-                    );
-                }
+            if sess.prof.enabled()
+                && let Some(artifact_name) = out_filename.file_name()
+            {
+                // Record size for self-profiling
+                let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
+
+                sess.prof.artifact_size(
+                    "linked_artifact",
+                    artifact_name.to_string_lossy(),
+                    file_size,
+                );
             }
 
             if output.is_stdout() {
@@ -186,16 +186,12 @@ pub fn link_binary(
 
         let maybe_remove_temps_from_module =
             |preserve_objects: bool, preserve_dwarf_objects: bool, module: &CompiledModule| {
-                if !preserve_objects {
-                    if let Some(ref obj) = module.object {
-                        ensure_removed(sess.dcx(), obj);
-                    }
+                if !preserve_objects && let Some(ref obj) = module.object {
+                    ensure_removed(sess.dcx(), obj);
                 }
 
-                if !preserve_dwarf_objects {
-                    if let Some(ref dwo_obj) = module.dwarf_object {
-                        ensure_removed(sess.dcx(), dwo_obj);
-                    }
+                if !preserve_dwarf_objects && let Some(ref dwo_obj) = module.dwarf_object {
+                    ensure_removed(sess.dcx(), dwo_obj);
                 }
             };
 
@@ -298,7 +294,7 @@ fn link_rlib<'a>(
             let (metadata, metadata_position) = create_wrapper_file(
                 sess,
                 ".rmeta".to_string(),
-                codegen_results.metadata.raw_data(),
+                codegen_results.metadata.stub_or_full(),
             );
             let metadata = emit_wrapper_file(sess, &metadata, tmpdir, METADATA_FILENAME);
             match metadata_position {
@@ -674,7 +670,7 @@ fn link_natively(
 ) {
     info!("preparing {:?} to {:?}", crate_type, out_filename);
     let (linker_path, flavor) = linker_and_flavor(sess);
-    let self_contained_components = self_contained_components(sess, crate_type);
+    let self_contained_components = self_contained_components(sess, crate_type, &linker_path);
 
     // On AIX, we ship all libraries as .a big_af archive
     // the expected format is lib<name>.a(libname.so) for the actual
@@ -1498,7 +1494,8 @@ fn print_native_static_libs(
                 | NativeLibKind::Unspecified => {
                     let verbatim = lib.verbatim;
                     if sess.target.is_like_msvc {
-                        Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
+                        let (prefix, suffix) = sess.staticlib_components(verbatim);
+                        Some(format!("{prefix}{name}{suffix}"))
                     } else if sess.target.linker_flavor.is_gnu() {
                         Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
                     } else {
@@ -1563,17 +1560,13 @@ fn print_native_static_libs(
     match out {
         OutFileName::Real(path) => {
             out.overwrite(&lib_args.join(" "), sess);
-            if !lib_args.is_empty() {
-                sess.dcx().emit_note(errors::StaticLibraryNativeArtifactsToFile { path });
-            }
+            sess.dcx().emit_note(errors::StaticLibraryNativeArtifactsToFile { path });
         }
         OutFileName::Stdout => {
-            if !lib_args.is_empty() {
-                sess.dcx().emit_note(errors::StaticLibraryNativeArtifacts);
-                // Prefix for greppability
-                // Note: This must not be translated as tools are allowed to depend on this exact string.
-                sess.dcx().note(format!("native-static-libs: {}", lib_args.join(" ")));
-            }
+            sess.dcx().emit_note(errors::StaticLibraryNativeArtifacts);
+            // Prefix for greppability
+            // Note: This must not be translated as tools are allowed to depend on this exact string.
+            sess.dcx().note(format!("native-static-libs: {}", lib_args.join(" ")));
         }
     }
 }
@@ -1787,8 +1780,7 @@ fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
 }
 
 // Returns true if linker is located within sysroot
-fn detect_self_contained_mingw(sess: &Session) -> bool {
-    let (linker, _) = linker_and_flavor(sess);
+fn detect_self_contained_mingw(sess: &Session, linker: &Path) -> bool {
     // Assume `-C linker=rust-lld` as self-contained mode
     if linker == Path::new("rust-lld") {
         return true;
@@ -1796,7 +1788,7 @@ fn detect_self_contained_mingw(sess: &Session) -> bool {
     let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
         linker.with_extension("exe")
     } else {
-        linker
+        linker.to_path_buf()
     };
     for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
         let full_path = dir.join(&linker_with_extension);
@@ -1811,7 +1803,11 @@ fn detect_self_contained_mingw(sess: &Session) -> bool {
 /// Various toolchain components used during linking are used from rustc distribution
 /// instead of being found somewhere on the host system.
 /// We only provide such support for a very limited number of targets.
-fn self_contained_components(sess: &Session, crate_type: CrateType) -> LinkSelfContainedComponents {
+fn self_contained_components(
+    sess: &Session,
+    crate_type: CrateType,
+    linker: &Path,
+) -> LinkSelfContainedComponents {
     // Turn the backwards compatible bool values for `self_contained` into fully inferred
     // `LinkSelfContainedComponents`.
     let self_contained =
@@ -1840,7 +1836,7 @@ fn self_contained_components(sess: &Session, crate_type: CrateType) -> LinkSelfC
                 LinkSelfContainedDefault::InferredForMingw => {
                     sess.host == sess.target
                         && sess.target.vendor != "uwp"
-                        && detect_self_contained_mingw(sess)
+                        && detect_self_contained_mingw(sess, linker)
                 }
             }
         };
@@ -2116,11 +2112,11 @@ fn add_local_crate_metadata_objects(
     // When linking a dynamic library, we put the metadata into a section of the
     // executable. This metadata is in a separate object file from the main
     // object file, so we link that in here.
-    if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
-        if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
-        {
-            cmd.add_object(obj);
-        }
+    if matches!(crate_type, CrateType::Dylib | CrateType::ProcMacro)
+        && let Some(m) = &codegen_results.metadata_module
+        && let Some(obj) = &m.object
+    {
+        cmd.add_object(obj);
     }
 }
 
@@ -2540,10 +2536,11 @@ fn add_order_independent_options(
 
     cmd.output_filename(out_filename);
 
-    if crate_type == CrateType::Executable && sess.target.is_like_windows {
-        if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
-            cmd.subsystem(s);
-        }
+    if crate_type == CrateType::Executable
+        && sess.target.is_like_windows
+        && let Some(s) = &codegen_results.crate_info.windows_subsystem
+    {
+        cmd.subsystem(s);
     }
 
     // Try to strip as much out of the generated object by removing unused
@@ -3204,9 +3201,7 @@ fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavo
 }
 
 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) -> Option<PathBuf> {
-    let arch = &sess.target.arch;
     let os = &sess.target.os;
-    let llvm_target = &sess.target.llvm_target;
     if sess.target.vendor != "apple"
         || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "visionos" | "macos")
         || !matches!(flavor, LinkerFlavor::Darwin(..))
@@ -3218,37 +3213,7 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) ->
         return None;
     }
 
-    let sdk_name = match (arch.as_ref(), os.as_ref()) {
-        ("aarch64", "tvos") if llvm_target.ends_with("-simulator") => "appletvsimulator",
-        ("aarch64", "tvos") => "appletvos",
-        ("x86_64", "tvos") => "appletvsimulator",
-        ("arm", "ios") => "iphoneos",
-        ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
-        ("aarch64", "ios") if llvm_target.ends_with("-simulator") => "iphonesimulator",
-        ("aarch64", "ios") => "iphoneos",
-        ("x86", "ios") => "iphonesimulator",
-        ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
-        ("x86_64", "ios") => "iphonesimulator",
-        ("x86_64", "watchos") => "watchsimulator",
-        ("arm64_32", "watchos") => "watchos",
-        ("aarch64", "watchos") if llvm_target.ends_with("-simulator") => "watchsimulator",
-        ("aarch64", "watchos") => "watchos",
-        ("aarch64", "visionos") if llvm_target.ends_with("-simulator") => "xrsimulator",
-        ("aarch64", "visionos") => "xros",
-        ("arm", "watchos") => "watchos",
-        (_, "macos") => "macosx",
-        _ => {
-            sess.dcx().emit_err(errors::UnsupportedArch { arch, os });
-            return None;
-        }
-    };
-    let sdk_root = match get_apple_sdk_root(sdk_name) {
-        Ok(s) => s,
-        Err(e) => {
-            sess.dcx().emit_err(e);
-            return None;
-        }
-    };
+    let sdk_root = sess.time("get_apple_sdk_root", || get_apple_sdk_root(sess))?;
 
     match flavor {
         LinkerFlavor::Darwin(Cc::Yes, _) => {
@@ -3258,28 +3223,32 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) ->
             // This is admittedly a bit strange, as on most targets
             // `-isysroot` only applies to include header files, but on Apple
             // targets this also applies to libraries and frameworks.
-            cmd.cc_args(&["-isysroot", &sdk_root]);
+            cmd.cc_arg("-isysroot");
+            cmd.cc_arg(&sdk_root);
         }
         LinkerFlavor::Darwin(Cc::No, _) => {
-            cmd.link_args(&["-syslibroot", &sdk_root]);
+            cmd.link_arg("-syslibroot");
+            cmd.link_arg(&sdk_root);
         }
         _ => unreachable!(),
     }
 
-    Some(sdk_root.into())
+    Some(sdk_root)
 }
 
-fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootError<'_>> {
-    // Following what clang does
-    // (https://github.com/llvm/llvm-project/blob/
-    // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
-    // to allow the SDK path to be set. (For clang, xcrun sets
-    // SDKROOT; for rustc, the user or build system can set it, or we
-    // can fall back to checking for xcrun on PATH.)
+fn get_apple_sdk_root(sess: &Session) -> Option<PathBuf> {
     if let Ok(sdkroot) = env::var("SDKROOT") {
-        let p = Path::new(&sdkroot);
-        match sdk_name {
-            // Ignore `SDKROOT` if it's clearly set for the wrong platform.
+        let p = PathBuf::from(&sdkroot);
+
+        // Ignore invalid SDKs, similar to what clang does:
+        // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.6/clang/lib/Driver/ToolChains/Darwin.cpp#L2212-L2229
+        //
+        // NOTE: Things are complicated here by the fact that `rustc` can be run by Cargo to compile
+        // build scripts and proc-macros for the host, and thus we need to ignore SDKROOT if it's
+        // clearly set for the wrong platform.
+        //
+        // FIXME(madsmtm): Make this more robust (maybe read `SDKSettings.json` like Clang does?).
+        match &*apple::sdk_name(&sess.target).to_lowercase() {
             "appletvos"
                 if sdkroot.contains("TVSimulator.platform")
                     || sdkroot.contains("MacOSX.platform") => {}
@@ -3306,26 +3275,11 @@ fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootErro
                 if sdkroot.contains("XROS.platform") || sdkroot.contains("MacOSX.platform") => {}
             // Ignore `SDKROOT` if it's not a valid path.
             _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
-            _ => return Ok(sdkroot),
+            _ => return Some(p),
         }
     }
-    let res =
-        Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
-            |output| {
-                if output.status.success() {
-                    Ok(String::from_utf8(output.stdout).unwrap())
-                } else {
-                    let error = String::from_utf8(output.stderr);
-                    let error = format!("process exit with error: {}", error.unwrap());
-                    Err(io::Error::new(io::ErrorKind::Other, &error[..]))
-                }
-            },
-        );
 
-    match res {
-        Ok(output) => Ok(output.trim().to_string()),
-        Err(error) => Err(errors::AppleSdkRootError::SdkPath { sdk_name, error }),
-    }
+    apple::get_sdk_root(sess)
 }
 
 /// When using the linker flavors opting in to `lld`, add the necessary paths and arguments to
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index a8405a2aec9..bcf18cf57be 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -111,24 +111,22 @@ pub(crate) fn get_linker<'a>(
     // PATH for the child.
     let mut new_path = sess.get_tools_search_paths(self_contained);
     let mut msvc_changed_path = false;
-    if sess.target.is_like_msvc {
-        if let Some(ref tool) = msvc_tool {
-            cmd.args(tool.args());
-            for (k, v) in tool.env() {
-                if k == "PATH" {
-                    new_path.extend(env::split_paths(v));
-                    msvc_changed_path = true;
-                } else {
-                    cmd.env(k, v);
-                }
+    if sess.target.is_like_msvc
+        && let Some(ref tool) = msvc_tool
+    {
+        cmd.args(tool.args());
+        for (k, v) in tool.env() {
+            if k == "PATH" {
+                new_path.extend(env::split_paths(v));
+                msvc_changed_path = true;
+            } else {
+                cmd.env(k, v);
             }
         }
     }
 
-    if !msvc_changed_path {
-        if let Some(path) = env::var_os("PATH") {
-            new_path.extend(env::split_paths(&path));
-        }
+    if !msvc_changed_path && let Some(path) = env::var_os("PATH") {
+        new_path.extend(env::split_paths(&path));
     }
     cmd.env("PATH", env::join_paths(new_path).unwrap());
 
@@ -452,9 +450,10 @@ impl<'a> GccLinker<'a> {
                     // The output filename already contains `dll_suffix` so
                     // the resulting import library will have a name in the
                     // form of libfoo.dll.a
-                    let mut implib_name = OsString::from(&*self.sess.target.staticlib_prefix);
+                    let (prefix, suffix) = self.sess.staticlib_components(false);
+                    let mut implib_name = OsString::from(prefix);
                     implib_name.push(name);
-                    implib_name.push(&*self.sess.target.staticlib_suffix);
+                    implib_name.push(suffix);
                     let mut out_implib = OsString::from("--out-implib=");
                     out_implib.push(out_filename.with_file_name(implib_name));
                     self.link_arg(out_implib);
@@ -960,9 +959,9 @@ impl<'a> Linker for MsvcLinker<'a> {
         if let Some(path) = try_find_native_static_library(self.sess, name, verbatim) {
             self.link_staticlib_by_path(&path, whole_archive);
         } else {
-            let prefix = if whole_archive { "/WHOLEARCHIVE:" } else { "" };
-            let suffix = if verbatim { "" } else { ".lib" };
-            self.link_arg(format!("{prefix}{name}{suffix}"));
+            let opts = if whole_archive { "/WHOLEARCHIVE:" } else { "" };
+            let (prefix, suffix) = self.sess.staticlib_components(verbatim);
+            self.link_arg(format!("{opts}{prefix}{name}{suffix}"));
         }
     }
 
@@ -1784,7 +1783,10 @@ fn exported_symbols_for_non_proc_macro(tcx: TyCtxt<'_>, crate_type: CrateType) -
     let mut symbols = Vec::new();
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
-        if info.level.is_below_threshold(export_threshold) {
+        // Do not export mangled symbols from cdylibs and don't attempt to export compiler-builtins
+        // from any cdylib. The latter doesn't work anyway as we use hidden visibility for
+        // compiler-builtins. Most linkers silently ignore it, but ld64 gives a warning.
+        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) {
             symbols.push(symbol_export::exporting_symbol_name_for_instance_in_crate(
                 tcx, symbol, cnum,
             ));
@@ -1823,7 +1825,9 @@ pub(crate) fn linked_symbols(
 
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
-        if info.level.is_below_threshold(export_threshold) || info.used {
+        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)
+            || info.used
+        {
             symbols.push((
                 symbol_export::linking_symbol_name_for_instance_in_crate(tcx, symbol, cnum),
                 info.kind,
diff --git a/compiler/rustc_codegen_ssa/src/back/metadata.rs b/compiler/rustc_codegen_ssa/src/back/metadata.rs
index 68b453ff424..ac9ac9bbb31 100644
--- a/compiler/rustc_codegen_ssa/src/back/metadata.rs
+++ b/compiler/rustc_codegen_ssa/src/back/metadata.rs
@@ -540,8 +540,8 @@ pub fn create_compressed_metadata_file(
     symbol_name: &str,
 ) -> Vec<u8> {
     let mut packed_metadata = rustc_metadata::METADATA_HEADER.to_vec();
-    packed_metadata.write_all(&(metadata.raw_data().len() as u64).to_le_bytes()).unwrap();
-    packed_metadata.extend(metadata.raw_data());
+    packed_metadata.write_all(&(metadata.stub_or_full().len() as u64).to_le_bytes()).unwrap();
+    packed_metadata.extend(metadata.stub_or_full());
 
     let Some(mut file) = create_object_file(sess) else {
         if sess.target.is_like_wasm {
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index 5c9e72ae0f1..fd06c50eb81 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -95,16 +95,11 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 return None;
             }
 
-            // Functions marked with #[inline] are codegened with "internal"
-            // linkage and are not exported unless marked with an extern
-            // indicator
-            if !Instance::mono(tcx, def_id.to_def_id()).def.generates_cgu_internal_copy(tcx)
-                || tcx.codegen_fn_attrs(def_id.to_def_id()).contains_extern_indicator()
-            {
-                Some(def_id)
-            } else {
-                None
+            if Instance::mono(tcx, def_id.into()).def.requires_inline(tcx) {
+                return None;
             }
+
+            if tcx.cross_crate_inlinable(def_id) { None } else { Some(def_id) }
         })
         .map(|def_id| {
             // We won't link right if this symbol is stripped during LTO.
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 9cc737d194c..ccc0273280f 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -546,9 +546,12 @@ fn copy_all_cgu_workproducts_to_incr_comp_cache_dir(
         if let Some(path) = &module.bytecode {
             files.push((OutputType::Bitcode.extension(), path.as_path()));
         }
-        if let Some((id, product)) =
-            copy_cgu_workproduct_to_incr_comp_cache_dir(sess, &module.name, files.as_slice())
-        {
+        if let Some((id, product)) = copy_cgu_workproduct_to_incr_comp_cache_dir(
+            sess,
+            &module.name,
+            files.as_slice(),
+            &module.links_from_incr_cache,
+        ) {
             work_products.insert(id, product);
         }
     }
@@ -566,16 +569,13 @@ fn produce_final_output_artifacts(
 
     // Produce final compile outputs.
     let copy_gracefully = |from: &Path, to: &OutFileName| match to {
-        OutFileName::Stdout => {
-            if let Err(e) = copy_to_stdout(from) {
-                sess.dcx().emit_err(errors::CopyPath::new(from, to.as_path(), e));
-            }
+        OutFileName::Stdout if let Err(e) = copy_to_stdout(from) => {
+            sess.dcx().emit_err(errors::CopyPath::new(from, to.as_path(), e));
         }
-        OutFileName::Real(path) => {
-            if let Err(e) = fs::copy(from, path) {
-                sess.dcx().emit_err(errors::CopyPath::new(from, path, e));
-            }
+        OutFileName::Real(path) if let Err(e) = fs::copy(from, path) => {
+            sess.dcx().emit_err(errors::CopyPath::new(from, path, e));
         }
+        _ => {}
     };
 
     let copy_if_one_unit = |output_type: OutputType, keep_numbered: bool| {
@@ -685,14 +685,12 @@ fn produce_final_output_artifacts(
             needs_crate_object || (user_wants_objects && sess.codegen_units().as_usize() > 1);
 
         for module in compiled_modules.modules.iter() {
-            if let Some(ref path) = module.object {
-                if !keep_numbered_objects {
+            if !keep_numbered_objects {
+                if let Some(ref path) = module.object {
                     ensure_removed(sess.dcx(), path);
                 }
-            }
 
-            if let Some(ref path) = module.dwarf_object {
-                if !keep_numbered_objects {
+                if let Some(ref path) = module.dwarf_object {
                     ensure_removed(sess.dcx(), path);
                 }
             }
@@ -704,12 +702,11 @@ fn produce_final_output_artifacts(
             }
         }
 
-        if !user_wants_bitcode {
-            if let Some(ref allocator_module) = compiled_modules.allocator_module {
-                if let Some(ref path) = allocator_module.bytecode {
-                    ensure_removed(sess.dcx(), path);
-                }
-            }
+        if !user_wants_bitcode
+            && let Some(ref allocator_module) = compiled_modules.allocator_module
+            && let Some(ref path) = allocator_module.bytecode
+        {
+            ensure_removed(sess.dcx(), path);
         }
     }
 
@@ -940,7 +937,9 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 ) -> WorkItemResult<B> {
     let incr_comp_session_dir = cgcx.incr_comp_session_dir.as_ref().unwrap();
 
-    let load_from_incr_comp_dir = |output_path: PathBuf, saved_path: &str| {
+    let mut links_from_incr_cache = Vec::new();
+
+    let mut load_from_incr_comp_dir = |output_path: PathBuf, saved_path: &str| {
         let source_file = in_incr_comp_dir(incr_comp_session_dir, saved_path);
         debug!(
             "copying preexisting module `{}` from {:?} to {}",
@@ -949,7 +948,10 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
             output_path.display()
         );
         match link_or_copy(&source_file, &output_path) {
-            Ok(_) => Some(output_path),
+            Ok(_) => {
+                links_from_incr_cache.push(source_file);
+                Some(output_path)
+            }
             Err(error) => {
                 cgcx.create_dcx().handle().emit_err(errors::CopyPathBuf {
                     source_file,
@@ -972,7 +974,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
             load_from_incr_comp_dir(dwarf_obj_out, saved_dwarf_object_file)
         });
 
-    let load_from_incr_cache = |perform, output_type: OutputType| {
+    let mut load_from_incr_cache = |perform, output_type: OutputType| {
         if perform {
             let saved_file = module.source.saved_files.get(output_type.extension())?;
             let output_path = cgcx.output_filenames.temp_path(output_type, Some(&module.name));
@@ -992,6 +994,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     }
 
     WorkItemResult::Finished(CompiledModule {
+        links_from_incr_cache,
         name: module.name,
         kind: ModuleKind::Regular,
         object,
@@ -2183,7 +2186,7 @@ fn msvc_imps_needed(tcx: TyCtxt<'_>) -> bool {
     // indirectly from ThinLTO. In theory these are not needed as ThinLTO could resolve
     // these, but it currently does not do so.
     let can_have_static_objects =
-        tcx.sess.lto() == Lto::Thin || tcx.crate_types().iter().any(|ct| *ct == CrateType::Rlib);
+        tcx.sess.lto() == Lto::Thin || tcx.crate_types().contains(&CrateType::Rlib);
 
     tcx.sess.target.is_like_windows &&
     can_have_static_objects   &&
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 396febcc637..1985b3b7170 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -658,6 +658,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
                 bytecode: None,
                 assembly: None,
                 llvm_ir: None,
+                links_from_incr_cache: Vec::new(),
             }
         })
     });
@@ -1104,11 +1105,12 @@ pub fn determine_cgu_reuse<'tcx>(tcx: TyCtxt<'tcx>, cgu: &CodegenUnit<'tcx>) ->
     // know that later). If we are not doing LTO, there is only one optimized
     // version of each module, so we re-use that.
     let dep_node = cgu.codegen_dep_node(tcx);
-    assert!(
-        !tcx.dep_graph.dep_node_exists(&dep_node),
-        "CompileCodegenUnit dep-node for CGU `{}` already exists before marking.",
-        cgu.name()
-    );
+    tcx.dep_graph.assert_dep_node_not_yet_allocated_in_current_session(&dep_node, || {
+        format!(
+            "CompileCodegenUnit dep-node for CGU `{}` already exists before marking.",
+            cgu.name()
+        )
+    });
 
     if tcx.try_mark_green(&dep_node) {
         // We can re-use either the pre- or the post-thinlto state. If no LTO is
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index d5972b5c9e6..a85d032f36e 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -604,7 +604,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     if let Some((name, _)) = lang_items::extract(attrs)
         && let Some(lang_item) = LangItem::from_name(name)
     {
-        if WEAK_LANG_ITEMS.iter().any(|&l| l == lang_item) {
+        if WEAK_LANG_ITEMS.contains(&lang_item) {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
         }
         if let Some(link_name) = lang_item.link_name() {
@@ -790,16 +790,10 @@ fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> Option<AutoDiffAttrs> {
 
     // check for exactly one autodiff attribute on placeholder functions.
     // There should only be one, since we generate a new placeholder per ad macro.
-    // FIXME(ZuseZ4): re-enable this check. Currently we add multiple, which doesn't cause harm but
-    // looks strange e.g. under cargo-expand.
     let attr = match &attrs[..] {
         [] => return None,
         [attr] => attr,
-        // These two attributes are the same and unfortunately duplicated due to a previous bug.
-        [attr, _attr2] => attr,
         _ => {
-            //FIXME(ZuseZ4): Once we fixed our parser, we should also prohibit the two-attribute
-            //branch above.
             span_bug!(attrs[1].span(), "cg_ssa: rustc_autodiff should only exist once per source");
         }
     };
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index 84703a0a156..18279a4d05f 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -555,11 +555,9 @@ pub fn compute_debuginfo_vtable_name<'tcx>(
 
 pub fn push_item_name(tcx: TyCtxt<'_>, def_id: DefId, qualified: bool, output: &mut String) {
     let def_key = tcx.def_key(def_id);
-    if qualified {
-        if let Some(parent) = def_key.parent {
-            push_item_name(tcx, DefId { krate: def_id.krate, index: parent }, true, output);
-            output.push_str("::");
-        }
+    if qualified && let Some(parent) = def_key.parent {
+        push_item_name(tcx, DefId { krate: def_id.krate, index: parent }, true, output);
+        output.push_str("::");
     }
 
     push_unqualified_item_name(tcx, def_id, def_key.disambiguated_data, output);
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 0b7cad0c2fd..f52d29baf9d 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -739,13 +739,6 @@ pub enum ExtractBundledLibsError<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(codegen_ssa_unsupported_arch)]
-pub(crate) struct UnsupportedArch<'a> {
-    pub arch: &'a str,
-    pub os: &'a str,
-}
-
-#[derive(Diagnostic)]
 pub(crate) enum AppleDeploymentTarget {
     #[diag(codegen_ssa_apple_deployment_target_invalid)]
     Invalid { env_var: &'static str, error: ParseIntError },
@@ -754,12 +747,6 @@ pub(crate) enum AppleDeploymentTarget {
 }
 
 #[derive(Diagnostic)]
-pub(crate) enum AppleSdkRootError<'a> {
-    #[diag(codegen_ssa_apple_sdk_error_sdk_path)]
-    SdkPath { sdk_name: &'a str, error: Error },
-}
-
-#[derive(Diagnostic)]
 #[diag(codegen_ssa_read_file)]
 pub(crate) struct ReadFileError {
     pub message: std::io::Error,
@@ -1334,3 +1321,26 @@ pub(crate) struct MixedExportNameAndNoMangle {
     #[suggestion(style = "verbose", code = "", applicability = "machine-applicable")]
     pub removal_span: Span,
 }
+
+#[derive(Diagnostic, Debug)]
+pub(crate) enum XcrunError {
+    #[diag(codegen_ssa_xcrun_failed_invoking)]
+    FailedInvoking { sdk_name: &'static str, command_formatted: String, error: std::io::Error },
+
+    #[diag(codegen_ssa_xcrun_unsuccessful)]
+    #[note]
+    Unsuccessful {
+        sdk_name: &'static str,
+        command_formatted: String,
+        stdout: String,
+        stderr: String,
+    },
+}
+
+#[derive(Diagnostic, Debug)]
+#[diag(codegen_ssa_xcrun_sdk_path_warning)]
+#[note]
+pub(crate) struct XcrunSdkPathWarning {
+    pub sdk_name: &'static str,
+    pub stderr: String,
+}
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index 44b8cc459cf..d26d6edf314 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -13,6 +13,7 @@
 #![feature(let_chains)]
 #![feature(negative_impls)]
 #![feature(rustdoc_internals)]
+#![feature(string_from_utf8_lossy_owned)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
 // tidy-alphabetical-end
@@ -122,6 +123,7 @@ impl<M> ModuleCodegen<M> {
             bytecode,
             assembly,
             llvm_ir,
+            links_from_incr_cache: Vec::new(),
         }
     }
 }
@@ -135,6 +137,7 @@ pub struct CompiledModule {
     pub bytecode: Option<PathBuf>,
     pub assembly: Option<PathBuf>, // --emit=asm
     pub llvm_ir: Option<PathBuf>,  // --emit=llvm-ir, llvm-bc is in bytecode
+    pub links_from_incr_cache: Vec<PathBuf>,
 }
 
 impl CompiledModule {
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 6d1930a402d..d184ce3d61d 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -163,25 +163,25 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         mergeable_succ: bool,
     ) -> MergingSucc {
         let tcx = bx.tcx();
-        if let Some(instance) = instance {
-            if is_call_from_compiler_builtins_to_upstream_monomorphization(tcx, instance) {
-                if destination.is_some() {
-                    let caller_def = fx.instance.def_id();
-                    let e = CompilerBuiltinsCannotCall {
-                        span: tcx.def_span(caller_def),
-                        caller: with_no_trimmed_paths!(tcx.def_path_str(caller_def)),
-                        callee: with_no_trimmed_paths!(tcx.def_path_str(instance.def_id())),
-                    };
-                    tcx.dcx().emit_err(e);
-                } else {
-                    info!(
-                        "compiler_builtins call to diverging function {:?} replaced with abort",
-                        instance.def_id()
-                    );
-                    bx.abort();
-                    bx.unreachable();
-                    return MergingSucc::False;
-                }
+        if let Some(instance) = instance
+            && is_call_from_compiler_builtins_to_upstream_monomorphization(tcx, instance)
+        {
+            if destination.is_some() {
+                let caller_def = fx.instance.def_id();
+                let e = CompilerBuiltinsCannotCall {
+                    span: tcx.def_span(caller_def),
+                    caller: with_no_trimmed_paths!(tcx.def_path_str(caller_def)),
+                    callee: with_no_trimmed_paths!(tcx.def_path_str(instance.def_id())),
+                };
+                tcx.dcx().emit_err(e);
+            } else {
+                info!(
+                    "compiler_builtins call to diverging function {:?} replaced with abort",
+                    instance.def_id()
+                );
+                bx.abort();
+                bx.unreachable();
+                return MergingSucc::False;
             }
         }
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
index bc9cde1b2a1..3a6b1f8d4ef 100644
--- a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
@@ -332,7 +332,7 @@ fn wasm_functype<'tcx>(tcx: TyCtxt<'tcx>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, def_id
     // please also add `wasm32-unknown-unknown` back in `tests/assembly/wasm32-naked-fn.rs`
     // basically the commit introducing this comment should be reverted
     if let PassMode::Pair { .. } = fn_abi.ret.mode {
-        let _ = WasmCAbi::Legacy;
+        let _ = WasmCAbi::Legacy { with_lint: true };
         span_bug!(
             tcx.def_span(def_id),
             "cannot return a pair (the wasm32-unknown-unknown ABI is broken, see https://github.com/rust-lang/rust/issues/115666"
@@ -384,7 +384,7 @@ fn wasm_type<'tcx>(
                 BackendRepr::SimdVector { .. } => "v128",
                 BackendRepr::Memory { .. } => {
                     // FIXME: remove this branch once the wasm32-unknown-unknown ABI is fixed
-                    let _ = WasmCAbi::Legacy;
+                    let _ = WasmCAbi::Legacy { with_lint: true };
                     span_bug!(
                         tcx.def_span(def_id),
                         "cannot use memory args (the wasm32-unknown-unknown ABI is broken, see https://github.com/rust-lang/rust/issues/115666"
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 72cfd2bffb5..5c14fe5cd10 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -86,13 +86,30 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::Rvalue::Repeat(ref elem, count) => {
-                let cg_elem = self.codegen_operand(bx, elem);
-
                 // Do not generate the loop for zero-sized elements or empty arrays.
                 if dest.layout.is_zst() {
                     return;
                 }
 
+                // When the element is a const with all bytes uninit, emit a single memset that
+                // writes undef to the entire destination.
+                if let mir::Operand::Constant(const_op) = elem {
+                    let val = self.eval_mir_constant(const_op);
+                    if val.all_bytes_uninit(self.cx.tcx()) {
+                        let size = bx.const_usize(dest.layout.size.bytes());
+                        bx.memset(
+                            dest.val.llval,
+                            bx.const_undef(bx.type_i8()),
+                            size,
+                            dest.val.align,
+                            MemFlags::empty(),
+                        );
+                        return;
+                    }
+                }
+
+                let cg_elem = self.codegen_operand(bx, elem);
+
                 let try_init_all_same = |bx: &mut Bx, v| {
                     let start = dest.val.llval;
                     let size = bx.const_usize(dest.layout.size.bytes());
@@ -837,15 +854,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     fn evaluate_array_len(&mut self, bx: &mut Bx, place: mir::Place<'tcx>) -> Bx::Value {
         // ZST are passed as operands and require special handling
         // because codegen_place() panics if Local is operand.
-        if let Some(index) = place.as_local() {
-            if let LocalRef::Operand(op) = self.locals[index] {
-                if let ty::Array(_, n) = op.layout.ty.kind() {
-                    let n = n
-                        .try_to_target_usize(bx.tcx())
-                        .expect("expected monomorphic const in codegen");
-                    return bx.cx().const_usize(n);
-                }
-            }
+        if let Some(index) = place.as_local()
+            && let LocalRef::Operand(op) = self.locals[index]
+            && let ty::Array(_, n) = op.layout.ty.kind()
+        {
+            let n = n.try_to_target_usize(bx.tcx()).expect("expected monomorphic const in codegen");
+            return bx.cx().const_usize(n);
         }
         // use common size calculation for non zero-sized types
         let cg_value = self.codegen_place(bx, place.as_ref());
@@ -991,6 +1005,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::BinOp::Cmp => {
                 use std::cmp::Ordering;
                 assert!(!is_float);
+                if let Some(value) = bx.three_way_compare(lhs_ty, lhs, rhs) {
+                    return value;
+                }
                 let pred = |op| base::bin_op_to_icmp_predicate(op, is_signed);
                 if bx.cx().tcx().sess.opts.optimize == OptLevel::No {
                     // FIXME: This actually generates tighter assembly, and is a classic trick
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 5f91133d5b4..f66309cf340 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -397,6 +397,18 @@ pub trait BuilderMethods<'a, 'tcx>:
     fn icmp(&mut self, op: IntPredicate, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
     fn fcmp(&mut self, op: RealPredicate, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
 
+    /// Returns `-1` if `lhs < rhs`, `0` if `lhs == rhs`, and `1` if `lhs > rhs`.
+    // FIXME: Move the default implementation from `codegen_scalar_binop` into this method and
+    // remove the `Option` return once LLVM 20 is the minimum version.
+    fn three_way_compare(
+        &mut self,
+        _ty: Ty<'tcx>,
+        _lhs: Self::Value,
+        _rhs: Self::Value,
+    ) -> Option<Self::Value> {
+        None
+    }
+
     fn memcpy(
         &mut self,
         dst: Self::Value,