1 use std::collections::hash_map::Entry::*;
3 use rustc_ast::expand::allocator::ALLOCATOR_METHODS;
4 use rustc_data_structures::fingerprint::Fingerprint;
5 use rustc_data_structures::fx::FxHashMap;
7 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
9 use rustc_index::vec::IndexVec;
10 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
11 use rustc_middle::middle::exported_symbols::{
12 metadata_symbol_name, ExportedSymbol, SymbolExportLevel,
14 use rustc_middle::ty::query::{ExternProviders, Providers};
15 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
16 use rustc_middle::ty::Instance;
17 use rustc_middle::ty::{SymbolName, TyCtxt};
18 use rustc_session::config::CrateType;
19 use rustc_target::spec::SanitizerSet;
21 pub fn threshold(tcx: TyCtxt<'_>) -> SymbolExportLevel {
22 crates_export_threshold(&tcx.sess.crate_types())
25 fn crate_export_threshold(crate_type: CrateType) -> SymbolExportLevel {
27 CrateType::Executable | CrateType::Staticlib | CrateType::ProcMacro | CrateType::Cdylib => {
30 CrateType::Rlib | CrateType::Dylib => SymbolExportLevel::Rust,
34 pub fn crates_export_threshold(crate_types: &[CrateType]) -> SymbolExportLevel {
37 .any(|&crate_type| crate_export_threshold(crate_type) == SymbolExportLevel::Rust)
39 SymbolExportLevel::Rust
45 fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<SymbolExportLevel> {
46 assert_eq!(cnum, LOCAL_CRATE);
48 if !tcx.sess.opts.output_types.should_codegen() {
49 return Default::default();
52 // Check to see if this crate is a "special runtime crate". These
53 // crates, implementation details of the standard library, typically
54 // have a bunch of `pub extern` and `#[no_mangle]` functions as the
55 // ABI between them. We don't want their symbols to have a `C`
56 // export level, however, as they're just implementation details.
57 // Down below we'll hardwire all of the symbols to the `Rust` export
59 let special_runtime_crate =
60 tcx.is_panic_runtime(LOCAL_CRATE) || tcx.is_compiler_builtins(LOCAL_CRATE);
62 let mut reachable_non_generics: DefIdMap<_> = tcx
65 .filter_map(|&def_id| {
66 // We want to ignore some FFI functions that are not exposed from
67 // this crate. Reachable FFI functions can be lumped into two
70 // 1. Those that are included statically via a static library
71 // 2. Those included otherwise (e.g., dynamically or via a framework)
73 // Although our LLVM module is not literally emitting code for the
74 // statically included symbols, it's an export of our library which
75 // needs to be passed on to the linker and encoded in the metadata.
77 // As a result, if this id is an FFI item (foreign item) then we only
78 // let it through if it's included statically.
79 match tcx.hir().get(tcx.hir().local_def_id_to_hir_id(def_id)) {
80 Node::ForeignItem(..) => {
81 tcx.is_statically_included_foreign_item(def_id).then_some(def_id)
84 // Only consider nodes that actually have exported symbols.
85 Node::Item(&hir::Item {
86 kind: hir::ItemKind::Static(..) | hir::ItemKind::Fn(..),
89 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => {
90 let generics = tcx.generics_of(def_id);
91 if !generics.requires_monomorphization(tcx)
92 // Functions marked with #[inline] are codegened with "internal"
93 // linkage and are not exported unless marked with an extern
95 && (!Instance::mono(tcx, def_id.to_def_id()).def.generates_cgu_internal_copy(tcx)
96 || tcx.codegen_fn_attrs(def_id.to_def_id()).contains_extern_indicator())
108 let export_level = if special_runtime_crate {
109 let name = tcx.symbol_name(Instance::mono(tcx, def_id.to_def_id())).name;
110 // We can probably do better here by just ensuring that
111 // it has hidden visibility rather than public
112 // visibility, as this is primarily here to ensure it's
113 // not stripped during LTO.
115 // In general though we won't link right if these
116 // symbols are stripped, and LTO currently strips them.
118 "rust_eh_personality"
119 | "rust_eh_register_frames"
120 | "rust_eh_unregister_frames" =>
121 SymbolExportLevel::C,
122 _ => SymbolExportLevel::Rust,
125 symbol_export_level(tcx, def_id.to_def_id())
128 "EXPORTED SYMBOL (local): {} ({:?})",
129 tcx.symbol_name(Instance::mono(tcx, def_id.to_def_id())),
132 (def_id.to_def_id(), export_level)
136 if let Some(id) = tcx.proc_macro_decls_static(()) {
137 reachable_non_generics.insert(id.to_def_id(), SymbolExportLevel::C);
140 reachable_non_generics
143 fn is_reachable_non_generic_provider_local(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
144 let export_threshold = threshold(tcx);
146 if let Some(&level) = tcx.reachable_non_generics(def_id.krate).get(&def_id) {
147 level.is_below_threshold(export_threshold)
153 fn is_reachable_non_generic_provider_extern(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
154 tcx.reachable_non_generics(def_id.krate).contains_key(&def_id)
157 fn exported_symbols_provider_local<'tcx>(
160 ) -> &'tcx [(ExportedSymbol<'tcx>, SymbolExportLevel)] {
161 assert_eq!(cnum, LOCAL_CRATE);
163 if !tcx.sess.opts.output_types.should_codegen() {
167 let mut symbols: Vec<_> = tcx
168 .reachable_non_generics(LOCAL_CRATE)
170 .map(|(&def_id, &level)| (ExportedSymbol::NonGeneric(def_id), level))
173 if tcx.entry_fn(()).is_some() {
174 let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, "main"));
176 symbols.push((exported_symbol, SymbolExportLevel::C));
179 if tcx.allocator_kind(()).is_some() {
180 for method in ALLOCATOR_METHODS {
181 let symbol_name = format!("__rust_{}", method.name);
182 let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
184 symbols.push((exported_symbol, SymbolExportLevel::Rust));
188 if tcx.sess.instrument_coverage() || tcx.sess.opts.cg.profile_generate.enabled() {
189 // These are weak symbols that point to the profile version and the
190 // profile name, which need to be treated as exported so LTO doesn't nix
192 const PROFILER_WEAK_SYMBOLS: [&str; 2] =
193 ["__llvm_profile_raw_version", "__llvm_profile_filename"];
195 symbols.extend(PROFILER_WEAK_SYMBOLS.iter().map(|sym| {
196 let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, sym));
197 (exported_symbol, SymbolExportLevel::C)
201 if tcx.sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::MEMORY) {
202 // Similar to profiling, preserve weak msan symbol during LTO.
203 const MSAN_WEAK_SYMBOLS: [&str; 2] = ["__msan_track_origins", "__msan_keep_going"];
205 symbols.extend(MSAN_WEAK_SYMBOLS.iter().map(|sym| {
206 let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, sym));
207 (exported_symbol, SymbolExportLevel::C)
211 if tcx.sess.crate_types().contains(&CrateType::Dylib) {
212 let symbol_name = metadata_symbol_name(tcx);
213 let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
215 symbols.push((exported_symbol, SymbolExportLevel::Rust));
218 if tcx.sess.opts.share_generics() && tcx.local_crate_exports_generics() {
219 use rustc_middle::mir::mono::{Linkage, MonoItem, Visibility};
220 use rustc_middle::ty::InstanceDef;
222 // Normally, we require that shared monomorphizations are not hidden,
223 // because if we want to re-use a monomorphization from a Rust dylib, it
224 // needs to be exported.
225 // However, on platforms that don't allow for Rust dylibs, having
226 // external linkage is enough for monomorphization to be linked to.
227 let need_visibility = tcx.sess.target.dynamic_linking && !tcx.sess.target.only_cdylib;
229 let (_, cgus) = tcx.collect_and_partition_mono_items(());
231 for (mono_item, &(linkage, visibility)) in cgus.iter().flat_map(|cgu| cgu.items().iter()) {
232 if linkage != Linkage::External {
233 // We can only re-use things with external linkage, otherwise
234 // we'll get a linker error
238 if need_visibility && visibility == Visibility::Hidden {
239 // If we potentially share things from Rust dylibs, they must
245 MonoItem::Fn(Instance { def: InstanceDef::Item(def), substs }) => {
246 if substs.non_erasable_generics().next().is_some() {
247 let symbol = ExportedSymbol::Generic(def.did, substs);
248 symbols.push((symbol, SymbolExportLevel::Rust));
251 MonoItem::Fn(Instance { def: InstanceDef::DropGlue(_, Some(ty)), substs }) => {
252 // A little sanity-check
254 substs.non_erasable_generics().next(),
255 Some(GenericArgKind::Type(ty))
257 symbols.push((ExportedSymbol::DropGlue(ty), SymbolExportLevel::Rust));
260 // Any other symbols don't qualify for sharing
266 // Sort so we get a stable incr. comp. hash.
267 symbols.sort_by_cached_key(|s| s.0.symbol_name_for_local_instance(tcx));
269 tcx.arena.alloc_from_iter(symbols)
272 fn upstream_monomorphizations_provider(
275 ) -> DefIdMap<FxHashMap<SubstsRef<'_>, CrateNum>> {
276 let cnums = tcx.crates(());
278 let mut instances: DefIdMap<FxHashMap<_, _>> = Default::default();
280 let cnum_stable_ids: IndexVec<CrateNum, Fingerprint> = {
281 let mut cnum_stable_ids = IndexVec::from_elem_n(Fingerprint::ZERO, cnums.len() + 1);
283 for &cnum in cnums.iter() {
284 cnum_stable_ids[cnum] =
285 tcx.def_path_hash(DefId { krate: cnum, index: CRATE_DEF_INDEX }).0;
291 let drop_in_place_fn_def_id = tcx.lang_items().drop_in_place_fn();
293 for &cnum in cnums.iter() {
294 for (exported_symbol, _) in tcx.exported_symbols(cnum).iter() {
295 let (def_id, substs) = match *exported_symbol {
296 ExportedSymbol::Generic(def_id, substs) => (def_id, substs),
297 ExportedSymbol::DropGlue(ty) => {
298 if let Some(drop_in_place_fn_def_id) = drop_in_place_fn_def_id {
299 (drop_in_place_fn_def_id, tcx.intern_substs(&[ty.into()]))
301 // `drop_in_place` in place does not exist, don't try
306 ExportedSymbol::NonGeneric(..) | ExportedSymbol::NoDefId(..) => {
307 // These are no monomorphizations
312 let substs_map = instances.entry(def_id).or_default();
314 match substs_map.entry(substs) {
316 // If there are multiple monomorphizations available,
317 // we select one deterministically.
318 let other_cnum = *e.get();
319 if cnum_stable_ids[other_cnum] > cnum_stable_ids[cnum] {
333 fn upstream_monomorphizations_for_provider(
336 ) -> Option<&FxHashMap<SubstsRef<'_>, CrateNum>> {
337 debug_assert!(!def_id.is_local());
338 tcx.upstream_monomorphizations(()).get(&def_id)
341 fn upstream_drop_glue_for_provider<'tcx>(
343 substs: SubstsRef<'tcx>,
344 ) -> Option<CrateNum> {
345 if let Some(def_id) = tcx.lang_items().drop_in_place_fn() {
346 tcx.upstream_monomorphizations_for(def_id).and_then(|monos| monos.get(&substs).cloned())
352 fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
353 !tcx.reachable_set(()).contains(&def_id)
356 pub fn provide(providers: &mut Providers) {
357 providers.reachable_non_generics = reachable_non_generics_provider;
358 providers.is_reachable_non_generic = is_reachable_non_generic_provider_local;
359 providers.exported_symbols = exported_symbols_provider_local;
360 providers.upstream_monomorphizations = upstream_monomorphizations_provider;
361 providers.is_unreachable_local_definition = is_unreachable_local_definition_provider;
362 providers.upstream_drop_glue_for = upstream_drop_glue_for_provider;
363 providers.wasm_import_module_map = wasm_import_module_map;
366 pub fn provide_extern(providers: &mut ExternProviders) {
367 providers.is_reachable_non_generic = is_reachable_non_generic_provider_extern;
368 providers.upstream_monomorphizations_for = upstream_monomorphizations_for_provider;
371 fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel {
372 // We export anything that's not mangled at the "C" layer as it probably has
373 // to do with ABI concerns. We do not, however, apply such treatment to
374 // special symbols in the standard library for various plumbing between
375 // core/std/allocators/etc. For example symbols used to hook up allocation
376 // are not considered for export
377 let codegen_fn_attrs = tcx.codegen_fn_attrs(sym_def_id);
378 let is_extern = codegen_fn_attrs.contains_extern_indicator();
380 codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
382 if is_extern && !std_internal {
383 let target = &tcx.sess.target.llvm_target;
384 // WebAssembly cannot export data symbols, so reduce their export level
385 if target.contains("emscripten") {
386 if let Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(..), .. })) =
387 tcx.hir().get_if_local(sym_def_id)
389 return SymbolExportLevel::Rust;
395 SymbolExportLevel::Rust
399 /// This is the symbol name of the given instance instantiated in a specific crate.
400 pub fn symbol_name_for_instance_in_crate<'tcx>(
402 symbol: ExportedSymbol<'tcx>,
403 instantiating_crate: CrateNum,
405 // If this is something instantiated in the local crate then we might
406 // already have cached the name as a query result.
407 if instantiating_crate == LOCAL_CRATE {
408 return symbol.symbol_name_for_local_instance(tcx).to_string();
411 // This is something instantiated in an upstream crate, so we have to use
412 // the slower (because uncached) version of computing the symbol name.
414 ExportedSymbol::NonGeneric(def_id) => {
415 rustc_symbol_mangling::symbol_name_for_instance_in_crate(
417 Instance::mono(tcx, def_id),
421 ExportedSymbol::Generic(def_id, substs) => {
422 rustc_symbol_mangling::symbol_name_for_instance_in_crate(
424 Instance::new(def_id, substs),
428 ExportedSymbol::DropGlue(ty) => rustc_symbol_mangling::symbol_name_for_instance_in_crate(
430 Instance::resolve_drop_in_place(tcx, ty),
433 ExportedSymbol::NoDefId(symbol_name) => symbol_name.to_string(),
437 fn wasm_import_module_map(tcx: TyCtxt<'_>, cnum: CrateNum) -> FxHashMap<DefId, String> {
438 // Build up a map from DefId to a `NativeLib` structure, where
439 // `NativeLib` internally contains information about
440 // `#[link(wasm_import_module = "...")]` for example.
441 let native_libs = tcx.native_libraries(cnum);
443 let def_id_to_native_lib = native_libs
445 .filter_map(|lib| lib.foreign_module.map(|id| (id, lib)))
446 .collect::<FxHashMap<_, _>>();
448 let mut ret = FxHashMap::default();
449 for (def_id, lib) in tcx.foreign_modules(cnum).iter() {
450 let module = def_id_to_native_lib.get(&def_id).and_then(|s| s.wasm_import_module);
451 let module = match module {
455 ret.extend(lib.foreign_items.iter().map(|id| {
456 assert_eq!(id.krate, cnum);
457 (*id, module.to_string())