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};
21 use rustc_data_structures::sync::Lrc;
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.params.iter().any(|param| param.is_type_param())
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>,
61 impl_item: &hir::ImplItem,
62 impl_src: DefId) -> bool {
63 if attr::requests_inline(&impl_item.attrs) ||
64 generics_require_inlining(&impl_item.generics) {
67 if let Some(impl_node_id) = tcx.hir.as_local_node_id(impl_src) {
68 match tcx.hir.find(impl_node_id) {
69 Some(hir_map::NodeItem(item)) =>
70 item_might_be_inlined(&item),
72 span_bug!(impl_item.span, "impl did is not an item")
75 span_bug!(impl_item.span, "found a foreign impl as a parent of a local method")
79 // Information needed while computing reachability.
80 struct ReachableContext<'a, 'tcx: 'a> {
82 tcx: TyCtxt<'a, 'tcx, 'tcx>,
83 tables: &'a ty::TypeckTables<'tcx>,
84 // The set of items which must be exported in the linkage sense.
85 reachable_symbols: NodeSet,
86 // A worklist of item IDs. Each item ID in this worklist will be inlined
87 // and will be scanned for further references.
88 worklist: Vec<ast::NodeId>,
89 // Whether any output of this compilation is a library
93 impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
94 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
95 NestedVisitorMap::None
98 fn visit_nested_body(&mut self, body: hir::BodyId) {
99 let old_tables = self.tables;
100 self.tables = self.tcx.body_tables(body);
101 let body = self.tcx.hir.body(body);
102 self.visit_body(body);
103 self.tables = old_tables;
106 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
107 let def = match expr.node {
108 hir::ExprPath(ref qpath) => {
109 Some(self.tables.qpath_def(qpath, expr.hir_id))
111 hir::ExprMethodCall(..) => {
112 Some(self.tables.type_dependent_defs()[expr.hir_id])
118 Some(Def::Local(node_id)) | Some(Def::Upvar(node_id, ..)) => {
119 self.reachable_symbols.insert(node_id);
122 let def_id = def.def_id();
123 if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
124 if self.def_id_represents_local_inlined_item(def_id) {
125 self.worklist.push(node_id);
128 // If this path leads to a constant, then we need to
129 // recurse into the constant to continue finding
130 // items that are reachable.
131 Def::Const(..) | Def::AssociatedConst(..) => {
132 self.worklist.push(node_id);
135 // If this wasn't a static, then the destination is
138 self.reachable_symbols.insert(node_id);
147 intravisit::walk_expr(self, expr)
151 impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
152 // Returns true if the given def ID represents a local item that is
153 // eligible for inlining and false otherwise.
154 fn def_id_represents_local_inlined_item(&self, def_id: DefId) -> bool {
155 let node_id = match self.tcx.hir.as_local_node_id(def_id) {
156 Some(node_id) => node_id,
157 None => { return false; }
160 match self.tcx.hir.find(node_id) {
161 Some(hir_map::NodeItem(item)) => {
163 hir::ItemFn(..) => item_might_be_inlined(&item),
167 Some(hir_map::NodeTraitItem(trait_method)) => {
168 match trait_method.node {
169 hir::TraitItemKind::Const(_, ref default) => default.is_some(),
170 hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => true,
171 hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) |
172 hir::TraitItemKind::Type(..) => false,
175 Some(hir_map::NodeImplItem(impl_item)) => {
176 match impl_item.node {
177 hir::ImplItemKind::Const(..) => true,
178 hir::ImplItemKind::Method(..) => {
179 if generics_require_inlining(&impl_item.generics) ||
180 attr::requests_inline(&impl_item.attrs) {
183 let impl_did = self.tcx
185 .get_parent_did(node_id);
186 // Check the impl. If the generics on the self
187 // type of the impl require inlining, this method
189 let impl_node_id = self.tcx.hir.as_local_node_id(impl_did).unwrap();
190 match self.tcx.hir.expect_item(impl_node_id).node {
191 hir::ItemImpl(_, _, _, ref generics, ..) => {
192 generics_require_inlining(generics)
198 hir::ImplItemKind::Type(_) => false,
202 None => false // This will happen for default methods.
206 // Step 2: Mark all symbols that the symbols on the worklist touch.
207 fn propagate(&mut self) {
208 let mut scanned = FxHashSet();
209 while let Some(search_item) = self.worklist.pop() {
210 if !scanned.insert(search_item) {
214 if let Some(ref item) = self.tcx.hir.find(search_item) {
215 self.propagate_node(item, search_item);
220 fn propagate_node(&mut self, node: &hir_map::Node<'tcx>,
221 search_item: ast::NodeId) {
222 if !self.any_library {
223 // If we are building an executable, only explicitly extern
224 // types need to be exported.
225 if let hir_map::NodeItem(item) = *node {
226 let reachable = if let hir::ItemFn(.., abi, _, _) = item.node {
231 let def_id = self.tcx.hir.local_def_id(item.id);
232 let is_extern = self.tcx.contains_extern_indicator(def_id);
233 if reachable || is_extern {
234 self.reachable_symbols.insert(search_item);
238 // If we are building a library, then reachable symbols will
239 // continue to participate in linkage after this product is
240 // produced. In this case, we traverse the ast node, recursing on
241 // all reachable nodes from this one.
242 self.reachable_symbols.insert(search_item);
246 hir_map::NodeItem(item) => {
248 hir::ItemFn(.., body) => {
249 if item_might_be_inlined(&item) {
250 self.visit_nested_body(body);
254 // Reachable constants will be inlined into other crates
255 // unconditionally, so we need to make sure that their
256 // contents are also reachable.
257 hir::ItemConst(_, init) => {
258 self.visit_nested_body(init);
261 // These are normal, nothing reachable about these
262 // inherently and their children are already in the
263 // worklist, as determined by the privacy pass
264 hir::ItemExternCrate(_) | hir::ItemUse(..) |
265 hir::ItemTy(..) | hir::ItemStatic(..) |
266 hir::ItemMod(..) | hir::ItemForeignMod(..) |
267 hir::ItemImpl(..) | hir::ItemTrait(..) | hir::ItemTraitAlias(..) |
268 hir::ItemStruct(..) | hir::ItemEnum(..) |
269 hir::ItemUnion(..) | 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(_, body) => {
291 let did = self.tcx.hir.get_parent_did(search_item);
292 if method_might_be_inlined(self.tcx, 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(_) |
308 hir_map::NodeMacroDef(_) => {}
310 bug!("found unexpected thingy in worklist: {}",
311 self.tcx.hir.node_to_string(search_item))
317 // Some methods from non-exported (completely private) trait impls still have to be
318 // reachable if they are called from inlinable code. Generally, it's not known until
319 // monomorphization if a specific trait impl item can be reachable or not. So, we
320 // conservatively mark all of them as reachable.
321 // FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
322 // items of non-exported traits (or maybe all local traits?) unless their respective
323 // trait items are used from inlinable code through method call syntax or UFCS, or their
324 // trait is a lang item.
325 struct CollectPrivateImplItemsVisitor<'a, 'tcx: 'a> {
326 tcx: TyCtxt<'a, 'tcx, 'tcx>,
327 access_levels: &'a privacy::AccessLevels,
328 worklist: &'a mut Vec<ast::NodeId>,
331 impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx> {
332 fn visit_item(&mut self, item: &hir::Item) {
333 // Anything which has custom linkage gets thrown on the worklist no
334 // matter where it is in the crate.
335 if attr::contains_name(&item.attrs, "linkage") {
336 self.worklist.push(item.id);
339 // We need only trait impls here, not inherent impls, and only non-exported ones
340 if let hir::ItemImpl(.., Some(ref trait_ref), _, ref impl_item_refs) = item.node {
341 if !self.access_levels.is_reachable(item.id) {
342 for impl_item_ref in impl_item_refs {
343 self.worklist.push(impl_item_ref.id.node_id);
346 let trait_def_id = match trait_ref.path.def {
347 Def::Trait(def_id) => def_id,
351 if !trait_def_id.is_local() {
355 for default_method in self.tcx.provided_trait_methods(trait_def_id) {
356 let node_id = self.tcx
358 .as_local_node_id(default_method.def_id)
360 self.worklist.push(node_id);
366 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {}
368 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
369 // processed in visit_item above
373 // We introduce a new-type here, so we can have a specialized HashStable
374 // implementation for it.
376 pub struct ReachableSet(pub Lrc<NodeSet>);
379 fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> ReachableSet {
380 debug_assert!(crate_num == LOCAL_CRATE);
382 let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
384 let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
385 *ty == config::CrateTypeRlib || *ty == config::CrateTypeDylib ||
386 *ty == config::CrateTypeProcMacro
388 let mut reachable_context = ReachableContext {
390 tables: &ty::TypeckTables::empty(None),
391 reachable_symbols: NodeSet(),
392 worklist: Vec::new(),
396 // Step 1: Seed the worklist with all nodes which were found to be public as
397 // a result of the privacy pass along with all local lang items and impl items.
398 // If other crates link to us, they're going to expect to be able to
399 // use the lang items, so we need to be sure to mark them as
401 for (id, _) in &access_levels.map {
402 reachable_context.worklist.push(*id);
404 for item in tcx.lang_items().items().iter() {
405 if let Some(did) = *item {
406 if let Some(node_id) = tcx.hir.as_local_node_id(did) {
407 reachable_context.worklist.push(node_id);
412 let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
415 worklist: &mut reachable_context.worklist,
417 tcx.hir.krate().visit_all_item_likes(&mut collect_private_impl_items);
420 // Step 2: Mark all symbols that the symbols on the worklist touch.
421 reachable_context.propagate();
423 // Return the set of reachable symbols.
424 ReachableSet(Lrc::new(reachable_context.reachable_symbols))
427 pub fn provide(providers: &mut Providers) {
428 *providers = Providers {