refactor add_gcc_ld_path into its final form

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -12,7 +12,7 @@ use rustc_metadata::fs::{copy_to_stdout, emit_wrapper_file, METADATA_FILENAME};
 use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::dependency_format::Linkage;
 use rustc_middle::middle::exported_symbols::SymbolExportKind;
-use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Strip};
+use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, Strip};
 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind};
 use rustc_session::cstore::DllImport;
 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
@@ -2246,7 +2246,8 @@ fn add_order_independent_options(
     out_filename: &Path,
     tmpdir: &Path,
 ) {
-    add_gcc_ld_path(cmd, sess, flavor);
+    // Take care of the flavors and CLI options requesting the `lld` linker.
+    add_lld_args(cmd, sess, flavor);
 
     add_apple_sdk(cmd, sess, flavor);
 
@@ -2948,16 +2949,31 @@ fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootErro
     }
 }
 
-fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
+/// When using the linker flavors opting in to `lld`, or the unstable `-Zgcc-ld=lld` flag, add the
-    if let Some(ld_impl) = sess.opts.unstable_opts.gcc_ld {
+/// necessary paths and arguments to invoke it:
-        if let LinkerFlavor::Gnu(Cc::Yes, _)
+/// - when the self-contained linker flag is active: the build of `lld` distributed with rustc,
-        | LinkerFlavor::Darwin(Cc::Yes, _)
+/// - or any `lld` available to `cc`.
-        | LinkerFlavor::WasmLld(Cc::Yes) = flavor
+fn add_lld_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
-        {
+    let unstable_use_lld = sess.opts.unstable_opts.gcc_ld.is_some();
-            match ld_impl {
+    debug!("add_lld_args requested, flavor: '{flavor:?}', `-Zgcc-ld=lld`: {unstable_use_lld}");
-                LdImpl::Lld => {
+
-                    // Implement the "self-contained" part of -Zgcc-ld
+    // Sanity check: using the old unstable `-Zgcc-ld=lld` option requires a `cc`-using flavor.
-                    // by adding rustc distribution directories to the tool search path.
+    let flavor_uses_cc = flavor.uses_cc();
+    if unstable_use_lld && !flavor_uses_cc {
+        sess.emit_fatal(errors::OptionGccOnly);
+    }
+
+    // If the flavor doesn't use a C/C++ compiler to invoke the linker, or doesn't opt in to `lld`,
+    // we don't need to do anything.
+    let use_lld = flavor.uses_lld() || unstable_use_lld;
+    if !flavor_uses_cc || !use_lld {
+        return;
+    }
+
+    // 1. Implement the "self-contained" part of this feature by adding rustc distribution
+    //    directories to the tool's search path.
+    let self_contained_linker = sess.opts.cg.link_self_contained.linker() || unstable_use_lld;
+    if self_contained_linker {
         for path in sess.get_tools_search_paths(false) {
             cmd.arg({
                 let mut arg = OsString::from("-B");
@@ -2965,8 +2981,10 @@ fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
                 arg
             });
         }
-                    // Implement the "linker flavor" part of -Zgcc-ld
+    }
-                    // by asking cc to use some kind of lld.
+
+    // 2. Implement the "linker flavor" part of this feature by asking `cc` to use some kind of
+    //    `lld` as the linker.
     cmd.arg("-fuse-ld=lld");
 
     if !flavor.is_gnu() {
@@ -2994,9 +3012,3 @@ fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         }
     }
 }
-            }
-        } else {
-            sess.emit_fatal(errors::OptionGccOnly);
-        }
-    }
-}

compiler/rustc_session/src/config.rs

@@ -307,6 +307,11 @@ impl LinkSelfContained {
         on.set_all_explicitly(true);
         on
     }
+
+    /// Returns whether the self-contained linker component is enabled.
+    pub fn linker(&self) -> bool {
+        self.components.contains(LinkSelfContainedComponents::LINKER)
+    }
 }
 
 /// Used with `-Z assert-incr-state`.