Rearrange where target is created when creating session

compiler/rustc_interface/src/tests.rs

@@ -35,6 +35,16 @@ fn mk_session(handler: &mut EarlyErrorHandler, matches: getopts::Matches) -> (Se
         output_file: None,
         temps_dir,
     };
+
+    let sysroot = match &sessopts.maybe_sysroot {
+        Some(sysroot) => sysroot.clone(),
+        None => {
+            rustc_session::filesearch::get_or_default_sysroot().expect("Failed finding sysroot")
+        }
+    };
+
+    let target_cfg = rustc_session::config::build_target_config(handler, &sessopts, None, &sysroot);
+
     let sess = build_session(
         handler,
         sessopts,
@@ -44,7 +54,8 @@ fn mk_session(handler: &mut EarlyErrorHandler, matches: getopts::Matches) -> (Se
         vec![],
         Default::default(),
         None,
-        None,
+        target_cfg,
+        sysroot,
         "",
         None,
         Arc::default(),

compiler/rustc_interface/src/util.rs

@@ -69,18 +69,39 @@ pub fn create_session(
     using_internal_features: Arc<AtomicBool>,
     expanded_args: Vec<String>,
 ) -> (Session, Box<dyn CodegenBackend>) {
-    let codegen_backend = if let Some(make_codegen_backend) = make_codegen_backend {
-        make_codegen_backend(&sopts)
-    } else {
-        get_codegen_backend(
-            handler,
-            &sopts.maybe_sysroot,
-            sopts.unstable_opts.codegen_backend.as_deref(),
-        )
+    let sysroot = match &sopts.maybe_sysroot {
+        Some(sysroot) => sysroot.clone(),
+        None => filesearch::get_or_default_sysroot().expect("Failed finding sysroot"),
     };
 
-    // target_override is documented to be called before init(), so this is okay
-    let target_override = codegen_backend.target_override(&sopts);
+    let (codegen_backend, target_cfg) = match make_codegen_backend {
+        Some(make_codegen_backend) => {
+            let backend = make_codegen_backend(&sopts);
+
+            // target_override is documented to be called before init(), so this is okay
+            let target_override = backend.target_override(&sopts);
+
+            let target = config::build_target_config(handler, &sopts, target_override, &sysroot);
+
+            (backend, target)
+        }
+        None => {
+            let _target = config::build_target_config(handler, &sopts, None, &sysroot);
+
+            let backend = get_codegen_backend(
+                handler,
+                &sopts.maybe_sysroot,
+                sopts.unstable_opts.codegen_backend.as_deref(),
+            );
+
+            // target_override is documented to be called before init(), so this is okay
+            let target_override = backend.target_override(&sopts);
+
+            let target = config::build_target_config(handler, &sopts, target_override, &sysroot);
+
+            (backend, target)
+        }
+    };
 
     let bundle = match rustc_errors::fluent_bundle(
         sopts.maybe_sysroot.clone(),
@@ -107,7 +128,8 @@ pub fn create_session(
         locale_resources,
         lint_caps,
         file_loader,
-        target_override,
+        target_cfg,
+        sysroot,
         rustc_version_str().unwrap_or("unknown"),
         ice_file,
         using_internal_features,

compiler/rustc_session/src/config.rs

@@ -1559,7 +1559,7 @@ pub fn build_configuration(sess: &Session, mut user_cfg: Cfg) -> Cfg {
     user_cfg
 }
 
-pub(super) fn build_target_config(
+pub fn build_target_config(
     handler: &EarlyErrorHandler,
     opts: &Options,
     target_override: Option<Target>,

compiler/rustc_session/src/session.rs

@@ -1392,7 +1392,8 @@ pub fn build_session(
     fluent_resources: Vec<&'static str>,
     driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
     file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
-    target_override: Option<Target>,
+    target_cfg: Target,
+    sysroot: PathBuf,
     cfg_version: &'static str,
     ice_file: Option<PathBuf>,
     using_internal_features: Arc<AtomicBool>,
@@ -1409,12 +1410,6 @@ pub fn build_session(
     let cap_lints_allow = sopts.lint_cap.is_some_and(|cap| cap == lint::Allow);
     let can_emit_warnings = !(warnings_allow || cap_lints_allow);
 
-    let sysroot = match &sopts.maybe_sysroot {
-        Some(sysroot) => sysroot.clone(),
-        None => filesearch::get_or_default_sysroot().expect("Failed finding sysroot"),
-    };
-
-    let target_cfg = config::build_target_config(handler, &sopts, target_override, &sysroot);
     let host_triple = TargetTriple::from_triple(config::host_triple());
     let (host, target_warnings) = Target::search(&host_triple, &sysroot)
         .unwrap_or_else(|e| handler.early_error(format!("Error loading host specification: {e}")));