Move Apple linker args from rustc_target to rustc_codegen_ssa

madsmtm · madsmtm · commit fb10eeb42b03 · 2024-09-26T16:40:25.000+02:00
They are dependent on the deployment target and SDK version, but having
these in `rustc_target` makes it hard to introduce that dependency.
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -40,7 +40,7 @@ use rustc_target::spec::crt_objects::CrtObjects;
 use rustc_target::spec::{
     Cc, LinkOutputKind, LinkSelfContainedComponents, LinkSelfContainedDefault, LinkerFeatures,
     LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy, RelocModel, RelroLevel, SanitizerSet,
-    SplitDebuginfo,
+    SplitDebuginfo, current_apple_deployment_target,
 };
 use tempfile::Builder as TempFileBuilder;
 use tracing::{debug, info, warn};
@@ -2405,6 +2405,8 @@ fn add_order_independent_options(
     // Take care of the flavors and CLI options requesting the `lld` linker.
     add_lld_args(cmd, sess, flavor, self_contained_components);
 
+    add_apple_link_args(cmd, sess, flavor);
+
     let apple_sdk_root = add_apple_sdk(cmd, sess, flavor);
 
     add_link_script(cmd, sess, tmpdir, crate_type);
@@ -2957,6 +2959,135 @@ pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool
     }
 }
 
+/// We need to communicate four things to the linker on Apple/Darwin targets:
+/// - The architecture.
+/// - The operating system (and that it's an Apple platform).
+/// - The deployment target.
+/// - The environment / ABI.
+fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
+    if !sess.target.is_like_osx {
+        return;
+    }
+    let LinkerFlavor::Darwin(cc, _) = flavor else {
+        return;
+    };
+
+    // `sess.target.arch` (`target_arch`) is not detailed enough.
+    let llvm_arch = sess.target.llvm_target.split_once('-').expect("LLVM target must have arch").0;
+    let target_os = &*sess.target.os;
+    let target_abi = &*sess.target.abi;
+
+    // The architecture name to forward to the linker.
+    //
+    // Supported architecture names can be found in the source:
+    // https://github.com/apple-oss-distributions/ld64/blob/ld64-951.9/src/abstraction/MachOFileAbstraction.hpp#L578-L648
+    //
+    // Intentially verbose to ensure that the list always matches correctly
+    // with the list in the source above.
+    let ld64_arch = match llvm_arch {
+        "armv7k" => "armv7k",
+        "armv7s" => "armv7s",
+        "arm64" => "arm64",
+        "arm64e" => "arm64e",
+        "arm64_32" => "arm64_32",
+        // ld64 doesn't understand i686, so fall back to i386 instead.
+        //
+        // Same story when linking with cc, since that ends up invoking ld64.
+        "i386" | "i686" => "i386",
+        "x86_64" => "x86_64",
+        "x86_64h" => "x86_64h",
+        _ => bug!("unsupported architecture in Apple target: {}", sess.target.llvm_target),
+    };
+
+    if cc == Cc::No {
+        // From the man page for ld64 (`man ld`):
+        // > The linker accepts universal (multiple-architecture) input files,
+        // > but always creates a "thin" (single-architecture), standard
+        // > Mach-O output file. The architecture for the output file is
+        // > specified using the -arch option.
+        //
+        // The linker has heuristics to determine the desired architecture,
+        // but to be safe, and to avoid a warning, we set the architecture
+        // explicitly.
+        cmd.link_args(&["-arch", ld64_arch]);
+
+        // Man page says that ld64 supports the following platform names:
+        // > - macos
+        // > - ios
+        // > - tvos
+        // > - watchos
+        // > - bridgeos
+        // > - visionos
+        // > - xros
+        // > - mac-catalyst
+        // > - ios-simulator
+        // > - tvos-simulator
+        // > - watchos-simulator
+        // > - visionos-simulator
+        // > - xros-simulator
+        // > - driverkit
+        let platform_name = match (target_os, target_abi) {
+            (os, "") => os,
+            ("ios", "macabi") => "mac-catalyst",
+            ("ios", "sim") => "ios-simulator",
+            ("tvos", "sim") => "tvos-simulator",
+            ("watchos", "sim") => "watchos-simulator",
+            ("visionos", "sim") => "visionos-simulator",
+            _ => bug!("invalid OS/ABI combination for Apple target: {target_os}, {target_abi}"),
+        };
+
+        let (major, minor, patch) = current_apple_deployment_target(&sess.target);
+        let min_version = format!("{major}.{minor}.{patch}");
+
+        // Lie about the SDK version, we don't know it here
+        let sdk_version = &*min_version;
+
+        // From the man page for ld64 (`man ld`):
+        // > This is set to indicate the platform, oldest supported version of
+        // > that platform that output is to be used on, and the SDK that the
+        // > output was built against.
+        //
+        // Like with `-arch`, the linker can figure out the platform versions
+        // itself from the binaries being linked, but to be safe, we specify
+        // the desired versions here explicitly.
+        cmd.link_args(&["-platform_version", platform_name, &*min_version, sdk_version]);
+    } else {
+        // cc == Cc::Yes
+        // We'd _like_ to use `-target` everywhere, since that can uniquely
+        // communicate all the required details, but that doesn't work on GCC,
+        // and since we don't know whether the `cc` compiler is Clang, GCC, or
+        // something else, we fall back to other options that also work on GCC
+        // when compiling for macOS.
+        //
+        // Targets other than macOS are ill-supported by GCC (it doesn't even
+        // support e.g. `-miphoneos-version-min`), so in those cases we can
+        // fairly safely use `-target`. See also the following, where it is
+        // made explicit that the recommendation by LLVM developers is to use
+        // `-target`: <https://github.com/llvm/llvm-project/issues/88271>
+        if target_os == "macos" {
+            // `-arch` communicates the architecture.
+            //
+            // CC forwards the `-arch` to the linker, so we use the same value
+            // here intentionally.
+            cmd.cc_args(&["-arch", ld64_arch]);
+
+            // The presence of `-mmacosx-version-min` makes CC default to
+            // macOS, and it sets the deployment target.
+            let (major, minor, patch) = current_apple_deployment_target(&sess.target);
+            // Intentionally pass this as a single argument, Clang doesn't
+            // seem to like it otherwise.
+            cmd.cc_arg(&format!("-mmacosx-version-min={major}.{minor}.{patch}"));
+
+            // macOS has no environment, so with these two, we've told CC the
+            // four desired parameters.
+            //
+            // We avoid `-m32`/`-m64`, as this is already encoded by `-arch`.
+        } else {
+            cmd.cc_args(&["-target", &sess.target.llvm_target]);
+        }
+    }
+}
+
 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) -> Option<PathBuf> {
     let arch = &sess.target.arch;
     let os = &sess.target.os;
diff --git a/compiler/rustc_target/src/spec/base/apple/mod.rs b/compiler/rustc_target/src/spec/base/apple/mod.rs
@@ -3,8 +3,8 @@ use std::env;
 use std::num::ParseIntError;
 
 use crate::spec::{
-    Cc, DebuginfoKind, FramePointer, LinkArgs, LinkerFlavor, Lld, SplitDebuginfo, StackProbeType,
-    StaticCow, Target, TargetOptions, add_link_args, add_link_args_iter, cvs,
+    Cc, DebuginfoKind, FramePointer, LinkerFlavor, Lld, SplitDebuginfo, StackProbeType, StaticCow,
+    Target, TargetOptions, cvs,
 };
 
 #[cfg(test)]
@@ -40,25 +40,6 @@ impl Arch {
         }
     }
 
-    /// The architecture name to forward to the linker.
-    fn ld_arch(self) -> &'static str {
-        // Supported architecture names can be found in the source:
-        // https://github.com/apple-oss-distributions/ld64/blob/ld64-951.9/src/abstraction/MachOFileAbstraction.hpp#L578-L648
-        match self {
-            Armv7k => "armv7k",
-            Armv7s => "armv7s",
-            Arm64 => "arm64",
-            Arm64e => "arm64e",
-            Arm64_32 => "arm64_32",
-            // ld64 doesn't understand i686, so fall back to i386 instead
-            //
-            // Same story when linking with cc, since that ends up invoking ld64.
-            I386 | I686 => "i386",
-            X86_64 => "x86_64",
-            X86_64h => "x86_64h",
-        }
-    }
-
     pub(crate) fn target_arch(self) -> Cow<'static, str> {
         Cow::Borrowed(match self {
             Armv7k | Armv7s => "arm",
@@ -116,104 +97,6 @@ impl TargetAbi {
     }
 }
 
-fn pre_link_args(os: &'static str, arch: Arch, abi: TargetAbi) -> LinkArgs {
-    // From the man page for ld64 (`man ld`):
-    // > The linker accepts universal (multiple-architecture) input files,
-    // > but always creates a "thin" (single-architecture), standard Mach-O
-    // > output file. The architecture for the output file is specified using
-    // > the -arch option.
-    //
-    // The linker has heuristics to determine the desired architecture, but to
-    // be safe, and to avoid a warning, we set the architecture explicitly.
-    let mut args =
-        TargetOptions::link_args(LinkerFlavor::Darwin(Cc::No, Lld::No), &["-arch", arch.ld_arch()]);
-
-    // From the man page for ld64 (`man ld`):
-    // > This is set to indicate the platform, oldest supported version of
-    // > that platform that output is to be used on, and the SDK that the
-    // > output was built against. platform [...] may be one of the following
-    // > strings:
-    // > - macos
-    // > - ios
-    // > - tvos
-    // > - watchos
-    // > - bridgeos
-    // > - visionos
-    // > - xros
-    // > - mac-catalyst
-    // > - ios-simulator
-    // > - tvos-simulator
-    // > - watchos-simulator
-    // > - visionos-simulator
-    // > - xros-simulator
-    // > - driverkit
-    //
-    // Like with `-arch`, the linker can figure out the platform versions
-    // itself from the binaries being linked, but to be safe, we specify the
-    // desired versions here explicitly.
-    let platform_name: StaticCow<str> = match abi {
-        TargetAbi::Normal => os.into(),
-        TargetAbi::Simulator => format!("{os}-simulator").into(),
-        TargetAbi::MacCatalyst => "mac-catalyst".into(),
-    };
-    let min_version: StaticCow<str> = {
-        let (major, minor, patch) = deployment_target(os, arch, abi);
-        format!("{major}.{minor}.{patch}").into()
-    };
-    // Lie about the SDK version, we don't know it here
-    let sdk_version = min_version.clone();
-    add_link_args_iter(
-        &mut args,
-        LinkerFlavor::Darwin(Cc::No, Lld::No),
-        ["-platform_version".into(), platform_name, min_version, sdk_version].into_iter(),
-    );
-
-    // We need to communicate four things to the C compiler to be able to link:
-    // - The architecture.
-    // - The operating system (and that it's an Apple platform).
-    // - The deployment target.
-    // - The environment / ABI.
-    //
-    // We'd like to use `-target` everywhere, since that can uniquely
-    // communicate all of these, but that doesn't work on GCC, and since we
-    // don't know whether the `cc` compiler is Clang, GCC, or something else,
-    // we fall back to other options that also work on GCC when compiling for
-    // macOS.
-    //
-    // Targets other than macOS are ill-supported by GCC (it doesn't even
-    // support e.g. `-miphoneos-version-min`), so in those cases we can fairly
-    // safely use `-target`. See also the following, where it is made explicit
-    // that the recommendation by LLVM developers is to use `-target`:
-    // <https://github.com/llvm/llvm-project/issues/88271>
-    if os == "macos" {
-        // `-arch` communicates the architecture.
-        //
-        // CC forwards the `-arch` to the linker, so we use the same value
-        // here intentionally.
-        add_link_args(&mut args, LinkerFlavor::Darwin(Cc::Yes, Lld::No), &[
-            "-arch",
-            arch.ld_arch(),
-        ]);
-        // The presence of `-mmacosx-version-min` makes CC default to macOS,
-        // and it sets the deployment target.
-        let (major, minor, patch) = deployment_target(os, arch, abi);
-        let opt = format!("-mmacosx-version-min={major}.{minor}.{patch}").into();
-        add_link_args_iter(&mut args, LinkerFlavor::Darwin(Cc::Yes, Lld::No), [opt].into_iter());
-        // macOS has no environment, so with these two, we've told CC all the
-        // desired parameters.
-        //
-        // We avoid `-m32`/`-m64`, as this is already encoded by `-arch`.
-    } else {
-        add_link_args_iter(
-            &mut args,
-            LinkerFlavor::Darwin(Cc::Yes, Lld::No),
-            ["-target".into(), llvm_target(os, arch, abi)].into_iter(),
-        );
-    }
-
-    args
-}
-
 /// Get the base target options, LLVM target and `target_arch` from the three
 /// things that uniquely identify Rust's Apple targets: The OS, the
 /// architecture, and the ABI.
@@ -232,7 +115,6 @@ pub(crate) fn base(
         // macOS has -dead_strip, which doesn't rely on function_sections
         function_sections: false,
         dynamic_linking: true,
-        pre_link_args: pre_link_args(os, arch, abi),
         families: cvs!["unix"],
         is_like_osx: true,
         // LLVM notes that macOS 10.11+ and iOS 9+ default
