Move exported_symbols_for_lto out of CodegenContext

bjorn3 · bjorn3 · commit b2948eb1268c · 2025-07-17T11:11:09.000Z
diff --git a/compiler/rustc_codegen_gcc/src/back/lto.rs b/compiler/rustc_codegen_gcc/src/back/lto.rs
@@ -51,9 +51,6 @@ fn prepare_lto(
     cgcx: &CodegenContext<GccCodegenBackend>,
     dcx: DiagCtxtHandle<'_>,
 ) -> Result<LtoData, FatalError> {
-    // FIXME(bjorn3): Limit LTO exports to these symbols
-    let _symbols_below_threshold = &cgcx.exported_symbols_for_lto;
-
     let tmp_path = match tempdir() {
         Ok(tmp_path) => tmp_path,
         Err(error) => {
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -355,6 +355,8 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        // FIXME(bjorn3): Limit LTO exports to these symbols
+        _exported_symbols_for_lto: &[String],
         modules: Vec<FatLtoInput<Self>>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
@@ -367,6 +369,8 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        // FIXME(bjorn3): Limit LTO exports to these symbols
+        _exported_symbols_for_lto: &[String],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError> {
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -33,10 +33,10 @@ const THIN_LTO_KEYS_INCR_COMP_FILE_NAME: &str = "thin-lto-past-keys.bin";
 
 fn prepare_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
     dcx: DiagCtxtHandle<'_>,
 ) -> Result<(Vec<CString>, Vec<(SerializedModule<ModuleBuffer>, CString)>), FatalError> {
-    let mut symbols_below_threshold = cgcx
-        .exported_symbols_for_lto
+    let mut symbols_below_threshold = exported_symbols_for_lto
         .iter()
         .map(|symbol| CString::new(symbol.to_owned()).unwrap())
         .collect::<Vec<CString>>();
@@ -135,11 +135,13 @@ fn get_bitcode_slice_from_object_data<'a>(
 /// for further optimization.
 pub(crate) fn run_fat(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
     modules: Vec<FatLtoInput<LlvmCodegenBackend>>,
 ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
+    let (symbols_below_threshold, upstream_modules) =
+        prepare_lto(cgcx, exported_symbols_for_lto, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
     fat_lto(cgcx, dcx, modules, upstream_modules, &symbols_below_threshold)
@@ -150,12 +152,14 @@ pub(crate) fn run_fat(
 /// can simply be copied over from the incr. comp. cache.
 pub(crate) fn run_thin(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
     modules: Vec<(String, ThinBuffer)>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<(Vec<ThinModule<LlvmCodegenBackend>>, Vec<WorkProduct>), FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
+    let (symbols_below_threshold, upstream_modules) =
+        prepare_lto(cgcx, exported_symbols_for_lto, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
     if cgcx.opts.cg.linker_plugin_lto.enabled() {
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -176,10 +176,11 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
         modules: Vec<FatLtoInput<Self>>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
-        let mut module = back::lto::run_fat(cgcx, modules)?;
+        let mut module = back::lto::run_fat(cgcx, exported_symbols_for_lto, modules)?;
 
         if !diff_fncs.is_empty() {
             builder::autodiff::differentiate(&module, cgcx, diff_fncs)?;
@@ -193,10 +194,11 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError> {
-        back::lto::run_thin(cgcx, modules, cached_modules)
+        back::lto::run_thin(cgcx, exported_symbols_for_lto, modules, cached_modules)
     }
     fn optimize(
         cgcx: &CodegenContext<Self>,
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -340,7 +340,6 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub opts: Arc<config::Options>,
     pub crate_types: Vec<CrateType>,
     pub each_linked_rlib_for_lto: Vec<(CrateNum, PathBuf)>,
-    pub exported_symbols_for_lto: Arc<Vec<String>>,
     pub output_filenames: Arc<OutputFilenames>,
     pub invocation_temp: Option<String>,
     pub regular_module_config: Arc<ModuleConfig>,
@@ -395,13 +394,15 @@ impl<B: WriteBackendMethods> CodegenContext<B> {
 
 fn generate_thin_lto_work<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
+    exported_symbols_for_lto: &[String],
     needs_thin_lto: Vec<(String, B::ThinBuffer)>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
 ) -> Vec<(WorkItem<B>, u64)> {
     let _prof_timer = cgcx.prof.generic_activity("codegen_thin_generate_lto_work");
 
     let (lto_modules, copy_jobs) =
-        B::run_thin_lto(cgcx, needs_thin_lto, import_only_modules).unwrap_or_else(|e| e.raise());
+        B::run_thin_lto(cgcx, exported_symbols_for_lto, needs_thin_lto, import_only_modules)
+            .unwrap_or_else(|e| e.raise());
     lto_modules
         .into_iter()
         .map(|module| {
@@ -717,6 +718,7 @@ pub(crate) enum WorkItem<B: WriteBackendMethods> {
     CopyPostLtoArtifacts(CachedModuleCodegen),
     /// Performs fat LTO on the given module.
     FatLto {
+        exported_symbols_for_lto: Arc<Vec<String>>,
         needs_fat_lto: Vec<FatLtoInput<B>>,
         import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
         autodiff: Vec<AutoDiffItem>,
@@ -989,6 +991,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
 fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
+    exported_symbols_for_lto: &[String],
     mut needs_fat_lto: Vec<FatLtoInput<B>>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
     autodiff: Vec<AutoDiffItem>,
@@ -998,7 +1001,8 @@ fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
         needs_fat_lto.push(FatLtoInput::Serialized { name: wp.cgu_name, buffer: module })
     }
 
-    let module = B::run_and_optimize_fat_lto(cgcx, needs_fat_lto, autodiff)?;
+    let module =
+        B::run_and_optimize_fat_lto(cgcx, exported_symbols_for_lto, needs_fat_lto, autodiff)?;
     let module = B::codegen(cgcx, module, module_config)?;
     Ok(WorkItemResult::Finished(module))
 }
@@ -1159,7 +1163,6 @@ fn start_executing_work<B: ExtraBackendMethods>(
     let cgcx = CodegenContext::<B> {
         crate_types: tcx.crate_types().to_vec(),
         each_linked_rlib_for_lto,
-        exported_symbols_for_lto,
         lto: sess.lto(),
         fewer_names: sess.fewer_names(),
         save_temps: sess.opts.cg.save_temps,
@@ -1438,6 +1441,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
                         work_items.push((
                             WorkItem::FatLto {
+                                exported_symbols_for_lto: Arc::clone(&exported_symbols_for_lto),
                                 needs_fat_lto,
                                 import_only_modules,
                                 autodiff: autodiff_items.clone(),
@@ -1453,9 +1457,12 @@ fn start_executing_work<B: ExtraBackendMethods>(
                             dcx.handle().emit_fatal(AutodiffWithoutLto {});
                         }
 
-                        for (work, cost) in
-                            generate_thin_lto_work(&cgcx, needs_thin_lto, import_only_modules)
-                        {
+                        for (work, cost) in generate_thin_lto_work(
+                            &cgcx,
+                            &exported_symbols_for_lto,
+                            needs_thin_lto,
+                            import_only_modules,
+                        ) {
                             let insertion_index = work_items
                                 .binary_search_by_key(&cost, |&(_, cost)| cost)
                                 .unwrap_or_else(|e| e);
@@ -1794,12 +1801,18 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
                     );
                     Ok(execute_copy_from_cache_work_item(&cgcx, m, module_config))
                 }
-                WorkItem::FatLto { needs_fat_lto, import_only_modules, autodiff } => {
+                WorkItem::FatLto {
+                    exported_symbols_for_lto,
+                    needs_fat_lto,
+                    import_only_modules,
+                    autodiff,
+                } => {
                     let _timer = cgcx
                         .prof
                         .generic_activity_with_arg("codegen_module_perform_lto", "everything");
                     execute_fat_lto_work_item(
                         &cgcx,
+                        &exported_symbols_for_lto,
                         needs_fat_lto,
                         import_only_modules,
                         autodiff,
diff --git a/compiler/rustc_codegen_ssa/src/traits/write.rs b/compiler/rustc_codegen_ssa/src/traits/write.rs
@@ -24,6 +24,7 @@ pub trait WriteBackendMethods: Clone + 'static {
     /// if necessary and running any further optimizations
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
         modules: Vec<FatLtoInput<Self>>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError>;
@@ -32,6 +33,7 @@ pub trait WriteBackendMethods: Clone + 'static {
     /// can simply be copied over from the incr. comp. cache.
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError>;
