Auto merge of #88250 - rusticstuff:macos-lld, r=nagisa

Make `-Z gcc-ld=lld` work for Apple targets

`-Z gcc-ld=lld` was introduced in #85961. It does not work on Macos because lld needs be either named `ld64` or passed `-flavor darwin` as the first two arguments in order to select the Mach-O flavor. Rust invokes cc (=clang) on Macos for linking which calls `ld` as linker binary and not `ld64`, so just creating an `ld64` binary and modifying the search path with `-B` does not work.

In order to solve this patch does:
* Set the `lld_flavor` for all Apple-derived targets to `LldFlavor::Ld64`. As far as I can see this actually works towards fixing `-Xlinker=rust-lld` as all those targets use the Mach-O object format.
* Copy/hardlink rust-lld to the gcc-ld subdirectory as ld64 next to ld.
* If `-Z gcc-ld=lld` is used and the target lld flavor is Ld64 add `-fuse-ld=/path/to/ld64` to the linker invocation.

Fixes #86945.

1 files changed, 33 insertions, 14 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index e51d6fff788..f5463bca338 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -2482,20 +2482,39 @@ fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         if let LinkerFlavor::Gcc = flavor {
             match ld_impl {
                 LdImpl::Lld => {
-                    let tools_path =
-                        sess.host_filesearch(PathKind::All).get_tools_search_paths(false);
-                    let lld_path = tools_path
-                        .into_iter()
-                        .map(|p| p.join("gcc-ld"))
-                        .find(|p| {
-                            p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" }).exists()
-                        })
-                        .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found"));
-                    cmd.cmd().arg({
-                        let mut arg = OsString::from("-B");
-                        arg.push(lld_path);
-                        arg
-                    });
+                    if sess.target.lld_flavor == LldFlavor::Ld64 {
+                        let tools_path =
+                            sess.host_filesearch(PathKind::All).get_tools_search_paths(false);
+                        let ld64_exe = tools_path
+                            .into_iter()
+                            .map(|p| p.join("gcc-ld"))
+                            .map(|p| {
+                                p.join(if sess.host.is_like_windows { "ld64.exe" } else { "ld64" })
+                            })
+                            .find(|p| p.exists())
+                            .unwrap_or_else(|| sess.fatal("rust-lld (as ld64) not found"));
+                        cmd.cmd().arg({
+                            let mut arg = OsString::from("-fuse-ld=");
+                            arg.push(ld64_exe);
+                            arg
+                        });
+                    } else {
+                        let tools_path =
+                            sess.host_filesearch(PathKind::All).get_tools_search_paths(false);
+                        let lld_path = tools_path
+                            .into_iter()
+                            .map(|p| p.join("gcc-ld"))
+                            .find(|p| {
+                                p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" })
+                                    .exists()
+                            })
+                            .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found"));
+                        cmd.cmd().arg({
+                            let mut arg = OsString::from("-B");
+                            arg.push(lld_path);
+                            arg
+                        });
+                    }
                 }
             }
         } else {