1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // Finds items that are externally reachable, to determine which items
12 // need to have their metadata (and possibly their AST) serialized.
13 // All items that can be referred to through an exported name are
14 // reachable, and when a reachable thing is inline or generic, it
15 // makes all other generics or inline functions that it references
18 use hir::map as hir_map;
20 use hir::def_id::{DefId, CrateNum};
22 use ty::{self, TyCtxt};
23 use ty::maps::Providers;
26 use util::nodemap::{NodeSet, FxHashSet};
32 use hir::def_id::LOCAL_CRATE;
33 use hir::intravisit::{Visitor, NestedVisitorMap};
34 use hir::itemlikevisit::ItemLikeVisitor;
37 // Returns true if the given set of generics implies that the item it's
38 // associated with must be inlined.
39 fn generics_require_inlining(generics: &hir::Generics) -> bool {
40 !generics.ty_params.is_empty()
43 // Returns true if the given item must be inlined because it may be
44 // monomorphized or it was marked with `#[inline]`. This will only return
45 // true for functions.
46 fn item_might_be_inlined(item: &hir::Item) -> bool {
47 if attr::requests_inline(&item.attrs) {
52 hir::ItemImpl(_, _, _, ref generics, ..) |
53 hir::ItemFn(.., ref generics, _) => {
54 generics_require_inlining(generics)
60 fn method_might_be_inlined<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
62 impl_item: &hir::ImplItem,
63 impl_src: DefId) -> bool {
64 if attr::requests_inline(&impl_item.attrs) ||
65 generics_require_inlining(&sig.generics) {
68 if let Some(impl_node_id) = tcx.hir.as_local_node_id(impl_src) {
69 match tcx.hir.find(impl_node_id) {
70 Some(hir_map::NodeItem(item)) =>
71 item_might_be_inlined(&item),
73 span_bug!(impl_item.span, "impl did is not an item")
76 span_bug!(impl_item.span, "found a foreign impl as a parent of a local method")
80 // Information needed while computing reachability.
81 struct ReachableContext<'a, 'tcx: 'a> {
83 tcx: TyCtxt<'a, 'tcx, 'tcx>,
84 tables: &'a ty::TypeckTables<'tcx>,
85 // The set of items which must be exported in the linkage sense.
86 reachable_symbols: NodeSet,
87 // A worklist of item IDs. Each item ID in this worklist will be inlined
88 // and will be scanned for further references.
89 worklist: Vec<ast::NodeId>,
90 // Whether any output of this compilation is a library
94 impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
95 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
96 NestedVisitorMap::None
99 fn visit_nested_body(&mut self, body: hir::BodyId) {
100 let old_tables = self.tables;
101 self.tables = self.tcx.body_tables(body);
102 let body = self.tcx.hir.body(body);
103 self.visit_body(body);
104 self.tables = old_tables;
107 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
108 let def = match expr.node {
109 hir::ExprPath(ref qpath) => {
110 Some(self.tables.qpath_def(qpath, expr.hir_id))
112 hir::ExprMethodCall(..) => {
113 Some(self.tables.type_dependent_defs()[expr.hir_id])
118 if let Some(def) = def {
119 let def_id = def.def_id();
120 if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
121 if self.def_id_represents_local_inlined_item(def_id) {
122 self.worklist.push(node_id);
125 // If this path leads to a constant, then we need to
126 // recurse into the constant to continue finding
127 // items that are reachable.
128 Def::Const(..) | Def::AssociatedConst(..) => {
129 self.worklist.push(node_id);
132 // If this wasn't a static, then the destination is
135 self.reachable_symbols.insert(node_id);
142 intravisit::walk_expr(self, expr)
146 impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
147 // Returns true if the given def ID represents a local item that is
148 // eligible for inlining and false otherwise.
149 fn def_id_represents_local_inlined_item(&self, def_id: DefId) -> bool {
150 let node_id = match self.tcx.hir.as_local_node_id(def_id) {
151 Some(node_id) => node_id,
152 None => { return false; }
155 match self.tcx.hir.find(node_id) {
156 Some(hir_map::NodeItem(item)) => {
158 hir::ItemFn(..) => item_might_be_inlined(&item),
162 Some(hir_map::NodeTraitItem(trait_method)) => {
163 match trait_method.node {
164 hir::TraitItemKind::Const(_, ref default) => default.is_some(),
165 hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => true,
166 hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) |
167 hir::TraitItemKind::Type(..) => false,
170 Some(hir_map::NodeImplItem(impl_item)) => {
171 match impl_item.node {
172 hir::ImplItemKind::Const(..) => true,
173 hir::ImplItemKind::Method(ref sig, _) => {
174 if generics_require_inlining(&sig.generics) ||
175 attr::requests_inline(&impl_item.attrs) {
178 let impl_did = self.tcx
180 .get_parent_did(node_id);
181 // Check the impl. If the generics on the self
182 // type of the impl require inlining, this method
184 let impl_node_id = self.tcx.hir.as_local_node_id(impl_did).unwrap();
185 match self.tcx.hir.expect_item(impl_node_id).node {
186 hir::ItemImpl(_, _, _, ref generics, ..) => {
187 generics_require_inlining(generics)
193 hir::ImplItemKind::Type(_) => false,
197 None => false // This will happen for default methods.
201 // Step 2: Mark all symbols that the symbols on the worklist touch.
202 fn propagate(&mut self) {
203 let mut scanned = FxHashSet();
205 let search_item = match self.worklist.pop() {
209 if !scanned.insert(search_item) {
213 if let Some(ref item) = self.tcx.hir.find(search_item) {
214 self.propagate_node(item, search_item);
219 fn propagate_node(&mut self, node: &hir_map::Node<'tcx>,
220 search_item: ast::NodeId) {
221 if !self.any_library {
222 // If we are building an executable, only explicitly extern
223 // types need to be exported.
224 if let hir_map::NodeItem(item) = *node {
225 let reachable = if let hir::ItemFn(.., abi, _, _) = item.node {
230 let is_extern = attr::contains_extern_indicator(&self.tcx.sess.diagnostic(),
232 if reachable || is_extern {
233 self.reachable_symbols.insert(search_item);
237 // If we are building a library, then reachable symbols will
238 // continue to participate in linkage after this product is
239 // produced. In this case, we traverse the ast node, recursing on
240 // all reachable nodes from this one.
241 self.reachable_symbols.insert(search_item);
245 hir_map::NodeItem(item) => {
247 hir::ItemFn(.., body) => {
248 if item_might_be_inlined(&item) {
249 self.visit_nested_body(body);
253 // Reachable constants will be inlined into other crates
254 // unconditionally, so we need to make sure that their
255 // contents are also reachable.
256 hir::ItemConst(_, init) => {
257 self.visit_nested_body(init);
260 // These are normal, nothing reachable about these
261 // inherently and their children are already in the
262 // worklist, as determined by the privacy pass
263 hir::ItemExternCrate(_) | hir::ItemUse(..) |
264 hir::ItemTy(..) | hir::ItemStatic(..) |
265 hir::ItemMod(..) | hir::ItemForeignMod(..) |
266 hir::ItemImpl(..) | hir::ItemTrait(..) |
267 hir::ItemStruct(..) | hir::ItemEnum(..) |
268 hir::ItemUnion(..) | hir::ItemDefaultImpl(..) |
269 hir::ItemGlobalAsm(..) => {}
272 hir_map::NodeTraitItem(trait_method) => {
273 match trait_method.node {
274 hir::TraitItemKind::Const(_, None) |
275 hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) => {
276 // Keep going, nothing to get exported
278 hir::TraitItemKind::Const(_, Some(body_id)) |
279 hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(body_id)) => {
280 self.visit_nested_body(body_id);
282 hir::TraitItemKind::Type(..) => {}
285 hir_map::NodeImplItem(impl_item) => {
286 match impl_item.node {
287 hir::ImplItemKind::Const(_, body) => {
288 self.visit_nested_body(body);
290 hir::ImplItemKind::Method(ref sig, body) => {
291 let did = self.tcx.hir.get_parent_did(search_item);
292 if method_might_be_inlined(self.tcx, sig, impl_item, did) {
293 self.visit_nested_body(body)
296 hir::ImplItemKind::Type(_) => {}
299 hir_map::NodeExpr(&hir::Expr { node: hir::ExprClosure(.., body, _, _), .. }) => {
300 self.visit_nested_body(body);
302 // Nothing to recurse on for these
303 hir_map::NodeForeignItem(_) |
304 hir_map::NodeVariant(_) |
305 hir_map::NodeStructCtor(_) |
306 hir_map::NodeField(_) |
307 hir_map::NodeTy(_) => {}
309 bug!("found unexpected thingy in worklist: {}",
310 self.tcx.hir.node_to_string(search_item))
316 // Some methods from non-exported (completely private) trait impls still have to be
317 // reachable if they are called from inlinable code. Generally, it's not known until
318 // monomorphization if a specific trait impl item can be reachable or not. So, we
319 // conservatively mark all of them as reachable.
320 // FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
321 // items of non-exported traits (or maybe all local traits?) unless their respective
322 // trait items are used from inlinable code through method call syntax or UFCS, or their
323 // trait is a lang item.
324 struct CollectPrivateImplItemsVisitor<'a, 'tcx: 'a> {
325 tcx: TyCtxt<'a, 'tcx, 'tcx>,
326 access_levels: &'a privacy::AccessLevels,
327 worklist: &'a mut Vec<ast::NodeId>,
330 impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx> {
331 fn visit_item(&mut self, item: &hir::Item) {
332 // We need only trait impls here, not inherent impls, and only non-exported ones
333 if let hir::ItemImpl(.., Some(ref trait_ref), _, ref impl_item_refs) = item.node {
334 if !self.access_levels.is_reachable(item.id) {
335 for impl_item_ref in impl_item_refs {
336 self.worklist.push(impl_item_ref.id.node_id);
339 let trait_def_id = match trait_ref.path.def {
340 Def::Trait(def_id) => def_id,
344 if !trait_def_id.is_local() {
348 for default_method in self.tcx.provided_trait_methods(trait_def_id) {
349 let node_id = self.tcx
351 .as_local_node_id(default_method.def_id)
353 self.worklist.push(node_id);
359 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {}
361 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
362 // processed in visit_item above
366 pub fn find_reachable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Rc<NodeSet> {
367 tcx.reachable_set(LOCAL_CRATE)
370 fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> Rc<NodeSet> {
371 debug_assert!(crate_num == LOCAL_CRATE);
373 let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
375 let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
376 *ty == config::CrateTypeRlib || *ty == config::CrateTypeDylib ||
377 *ty == config::CrateTypeProcMacro
379 let mut reachable_context = ReachableContext {
381 tables: &ty::TypeckTables::empty(None),
382 reachable_symbols: NodeSet(),
383 worklist: Vec::new(),
387 // Step 1: Seed the worklist with all nodes which were found to be public as
388 // a result of the privacy pass along with all local lang items and impl items.
389 // If other crates link to us, they're going to expect to be able to
390 // use the lang items, so we need to be sure to mark them as
392 for (id, _) in &access_levels.map {
393 reachable_context.worklist.push(*id);
395 for item in tcx.lang_items().items().iter() {
396 if let Some(did) = *item {
397 if let Some(node_id) = tcx.hir.as_local_node_id(did) {
398 reachable_context.worklist.push(node_id);
403 let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
406 worklist: &mut reachable_context.worklist,
408 tcx.hir.krate().visit_all_item_likes(&mut collect_private_impl_items);
411 // Step 2: Mark all symbols that the symbols on the worklist touch.
412 reachable_context.propagate();
414 // Return the set of reachable symbols.
415 Rc::new(reachable_context.reachable_symbols)
418 pub fn provide(providers: &mut Providers) {
419 *providers = Providers {