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

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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.
This commit is contained in:
bors 2021-08-29 04:51:14 +00:00
commit 757a65bfdf
4 changed files with 41 additions and 15 deletions
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47
compiler/rustc_codegen_ssa/src/back/link.rs
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@ -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 {