Rollup merge of rust-lang#100200 - petrochenkov:zgccld2, r=lqd,Mark-Simulacrum

Change implementation of `-Z gcc-ld` and `lld-wrapper` again

This PR partially reverts rust-lang#97375 and uses the strategy described in rust-lang#97402 (comment) instead, thus fixes rust-lang#97755.

Author: matthiaskrgr

Diff for: compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2797,20 +2797,24 @@ 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.get_tools_search_paths(false);
-                    let gcc_ld_dir = 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.arg({
-                        let mut arg = OsString::from("-B");
-                        arg.push(gcc_ld_dir);
-                        arg
-                    });
-                    cmd.arg(format!("-Wl,-rustc-lld-flavor={}", sess.target.lld_flavor.as_str()));
+                    // Implement the "self-contained" part of -Zgcc-ld
+                    // by adding rustc distribution directories to the tool search path.
+                    for path in sess.get_tools_search_paths(false) {
+                        cmd.arg({
+                            let mut arg = OsString::from("-B");
+                            arg.push(path.join("gcc-ld"));
+                            arg
+                        });
+                    }
+                    // Implement the "linker flavor" part of -Zgcc-ld
+                    // by asking cc to use some kind of lld.
+                    cmd.arg("-fuse-ld=lld");
+                    if sess.target.lld_flavor != LldFlavor::Ld {
+                        // Tell clang to use a non-default LLD flavor.
+                        // Gcc doesn't understand the target option, but we currently assume
+                        // that gcc is not used for Apple and Wasm targets (#97402).
+                        cmd.arg(format!("--target={}", sess.target.llvm_target));
+                    }
                 }
             }
         } else {

Diff for: src/bootstrap/compile.rs

@@ -1281,7 +1281,9 @@ impl Step for Assemble {
                 compiler: build_compiler,
                 target: target_compiler.host,
             });
-            builder.copy(&lld_wrapper_exe, &gcc_ld_dir.join(exe("ld", target_compiler.host)));
+            for name in crate::LLD_FILE_NAMES {
+                builder.copy(&lld_wrapper_exe, &gcc_ld_dir.join(exe(name, target_compiler.host)));
+            }
         }
 
         if builder.config.rust_codegen_backends.contains(&INTERNER.intern_str("llvm")) {

Diff for: src/bootstrap/dist.rs

@@ -423,8 +423,11 @@ impl Step for Rustc {
                 let gcc_lld_src_dir = src_dir.join("gcc-ld");
                 let gcc_lld_dst_dir = dst_dir.join("gcc-ld");
                 t!(fs::create_dir(&gcc_lld_dst_dir));
-                let exe_name = exe("ld", compiler.host);
-                builder.copy(&gcc_lld_src_dir.join(&exe_name), &gcc_lld_dst_dir.join(&exe_name));
+                for name in crate::LLD_FILE_NAMES {
+                    let exe_name = exe(name, compiler.host);
+                    builder
+                        .copy(&gcc_lld_src_dir.join(&exe_name), &gcc_lld_dst_dir.join(&exe_name));
+                }
             }
 
             // Man pages

Diff for: src/bootstrap/lib.rs

@@ -187,6 +187,9 @@ const LLVM_TOOLS: &[&str] = &[
     "opt",           // used to optimize LLVM bytecode
 ];
 
+/// LLD file names for all flavors.
+const LLD_FILE_NAMES: &[&str] = &["ld.lld", "ld64.lld", "lld-link", "wasm-ld"];
+
 pub const VERSION: usize = 2;
 
 /// Extra --check-cfg to add when building

Diff for: src/tools/lld-wrapper/src/main.rs

@@ -8,8 +8,8 @@
 //! make gcc/clang pass `-flavor <flavor>` as the first two arguments in the linker invocation
 //! and since Windows does not support symbolic links for files this wrapper is used in place of a
 //! symbolic link. It execs `../rust-lld -flavor <flavor>` by propagating the flavor argument
-//! passed to the wrapper as the first two arguments. On Windows it spawns a `..\rust-lld.exe`
-//! child process.
+//! obtained from the wrapper's name as the first two arguments.
+//! On Windows it spawns a `..\rust-lld.exe` child process.
 
 use std::fmt::Display;
 use std::path::{Path, PathBuf};
@@ -53,29 +53,32 @@ fn get_rust_lld_path(current_exe_path: &Path) -> PathBuf {
     rust_lld_path
 }
 
+/// Extract LLD flavor name from the lld-wrapper executable name.
+fn get_lld_flavor(current_exe_path: &Path) -> Result<&'static str, String> {
+    let stem = current_exe_path.file_stem();
+    Ok(match stem.and_then(|s| s.to_str()) {
+        Some("ld.lld") => "gnu",
+        Some("ld64.lld") => "darwin",
+        Some("lld-link") => "link",
+        Some("wasm-ld") => "wasm",
+        _ => return Err(format!("{:?}", stem)),
+    })
+}
+
 /// Returns the command for invoking rust-lld with the correct flavor.
-/// LLD only accepts the flavor argument at the first two arguments, so move it there.
+/// LLD only accepts the flavor argument at the first two arguments, so pass it there.
 ///
 /// Exits on error.
 fn get_rust_lld_command(current_exe_path: &Path) -> process::Command {
     let rust_lld_path = get_rust_lld_path(current_exe_path);
     let mut command = process::Command::new(rust_lld_path);
 
-    let mut flavor = None;
-    let args = env::args_os()
-        .skip(1)
-        .filter(|arg| match arg.to_str().and_then(|s| s.strip_prefix("-rustc-lld-flavor=")) {
-            Some(suffix) => {
-                flavor = Some(suffix.to_string());
-                false
-            }
-            None => true,
-        })
-        .collect::<Vec<_>>();
+    let flavor =
+        get_lld_flavor(current_exe_path).unwrap_or_exit_with("executable has unexpected name");
 
     command.arg("-flavor");
-    command.arg(flavor.unwrap_or_exit_with("-rustc-lld-flavor=<flavor> is not passed"));
-    command.args(args);
+    command.arg(flavor);
+    command.args(env::args_os().skip(1));
     command
 }