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 dep_graph::DepNode;
19 use hir::map as ast_map;
21 use hir::def_id::DefId;
22 use ty::{self, TyCtxt};
25 use util::nodemap::NodeSet;
27 use std::collections::HashSet;
32 use hir::intravisit::Visitor;
35 // Returns true if the given set of generics implies that the item it's
36 // associated with must be inlined.
37 fn generics_require_inlining(generics: &hir::Generics) -> bool {
38 !generics.ty_params.is_empty()
41 // Returns true if the given item must be inlined because it may be
42 // monomorphized or it was marked with `#[inline]`. This will only return
43 // true for functions.
44 fn item_might_be_inlined(item: &hir::Item) -> bool {
45 if attr::requests_inline(&item.attrs) {
50 hir::ItemImpl(_, _, ref generics, _, _, _) |
51 hir::ItemFn(_, _, _, _, ref generics, _) => {
52 generics_require_inlining(generics)
58 fn method_might_be_inlined<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
60 impl_item: &hir::ImplItem,
61 impl_src: DefId) -> bool {
62 if attr::requests_inline(&impl_item.attrs) ||
63 generics_require_inlining(&sig.generics) {
66 if let Some(impl_node_id) = tcx.map.as_local_node_id(impl_src) {
67 match tcx.map.find(impl_node_id) {
68 Some(ast_map::NodeItem(item)) =>
69 item_might_be_inlined(&item),
71 span_bug!(impl_item.span, "impl did is not an item")
74 span_bug!(impl_item.span, "found a foreign impl as a parent of a local method")
78 // Information needed while computing reachability.
79 struct ReachableContext<'a, 'tcx: 'a> {
81 tcx: TyCtxt<'a, 'tcx, 'tcx>,
82 // The set of items which must be exported in the linkage sense.
83 reachable_symbols: NodeSet,
84 // A worklist of item IDs. Each item ID in this worklist will be inlined
85 // and will be scanned for further references.
86 worklist: Vec<ast::NodeId>,
87 // Whether any output of this compilation is a library
91 impl<'a, 'tcx, 'v> Visitor<'v> for ReachableContext<'a, 'tcx> {
92 fn visit_expr(&mut self, expr: &hir::Expr) {
94 hir::ExprPath(..) => {
95 let def = self.tcx.expect_def(expr.id);
96 let def_id = def.def_id();
97 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
98 if self.def_id_represents_local_inlined_item(def_id) {
99 self.worklist.push(node_id);
102 // If this path leads to a constant, then we need to
103 // recurse into the constant to continue finding
104 // items that are reachable.
105 Def::Const(..) | Def::AssociatedConst(..) => {
106 self.worklist.push(node_id);
109 // If this wasn't a static, then the destination is
112 self.reachable_symbols.insert(node_id);
118 hir::ExprMethodCall(..) => {
119 let method_call = ty::MethodCall::expr(expr.id);
120 let def_id = self.tcx.tables.borrow().method_map[&method_call].def_id;
122 // Mark the trait item (and, possibly, its default impl) as reachable
123 // Or mark inherent impl item as reachable
124 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
125 if self.def_id_represents_local_inlined_item(def_id) {
126 self.worklist.push(node_id)
128 self.reachable_symbols.insert(node_id);
134 intravisit::walk_expr(self, expr)
138 impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
139 // Creates a new reachability computation context.
140 fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ReachableContext<'a, 'tcx> {
141 let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
142 *ty == config::CrateTypeRlib || *ty == config::CrateTypeDylib
146 reachable_symbols: NodeSet(),
147 worklist: Vec::new(),
148 any_library: any_library,
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.map.as_local_node_id(def_id) {
156 Some(node_id) => node_id,
157 None => { return false; }
160 match self.tcx.map.find(node_id) {
161 Some(ast_map::NodeItem(item)) => {
163 hir::ItemFn(..) => item_might_be_inlined(&item),
167 Some(ast_map::NodeTraitItem(trait_method)) => {
168 match trait_method.node {
169 hir::ConstTraitItem(_, ref default) => default.is_some(),
170 hir::MethodTraitItem(_, ref body) => body.is_some(),
171 hir::TypeTraitItem(..) => false,
174 Some(ast_map::NodeImplItem(impl_item)) => {
175 match impl_item.node {
176 hir::ImplItemKind::Const(..) => true,
177 hir::ImplItemKind::Method(ref sig, _) => {
178 if generics_require_inlining(&sig.generics) ||
179 attr::requests_inline(&impl_item.attrs) {
182 let impl_did = self.tcx
184 .get_parent_did(node_id);
185 // Check the impl. If the generics on the self
186 // type of the impl require inlining, this method
188 let impl_node_id = self.tcx.map.as_local_node_id(impl_did).unwrap();
189 match self.tcx.map.expect_item(impl_node_id).node {
190 hir::ItemImpl(_, _, ref generics, _, _, _) => {
191 generics_require_inlining(generics)
197 hir::ImplItemKind::Type(_) => false,
201 None => false // This will happen for default methods.
205 // Step 2: Mark all symbols that the symbols on the worklist touch.
206 fn propagate(&mut self) {
207 let mut scanned = HashSet::new();
209 let search_item = match self.worklist.pop() {
213 if !scanned.insert(search_item) {
217 if let Some(ref item) = self.tcx.map.find(search_item) {
218 self.propagate_node(item, search_item);
223 fn propagate_node(&mut self, node: &ast_map::Node,
224 search_item: ast::NodeId) {
225 if !self.any_library {
226 // If we are building an executable, only explicitly extern
227 // types need to be exported.
228 if let ast_map::NodeItem(item) = *node {
229 let reachable = if let hir::ItemFn(_, _, _, abi, _, _) = item.node {
234 let is_extern = attr::contains_extern_indicator(&self.tcx.sess.diagnostic(),
236 if reachable || is_extern {
237 self.reachable_symbols.insert(search_item);
241 // If we are building a library, then reachable symbols will
242 // continue to participate in linkage after this product is
243 // produced. In this case, we traverse the ast node, recursing on
244 // all reachable nodes from this one.
245 self.reachable_symbols.insert(search_item);
249 ast_map::NodeItem(item) => {
251 hir::ItemFn(_, _, _, _, _, ref search_block) => {
252 if item_might_be_inlined(&item) {
253 intravisit::walk_block(self, &search_block)
257 // Reachable constants will be inlined into other crates
258 // unconditionally, so we need to make sure that their
259 // contents are also reachable.
260 hir::ItemConst(_, ref init) => {
261 self.visit_expr(&init);
264 // These are normal, nothing reachable about these
265 // inherently and their children are already in the
266 // worklist, as determined by the privacy pass
267 hir::ItemExternCrate(_) | hir::ItemUse(_) |
268 hir::ItemTy(..) | hir::ItemStatic(_, _, _) |
269 hir::ItemMod(..) | hir::ItemForeignMod(..) |
270 hir::ItemImpl(..) | hir::ItemTrait(..) |
271 hir::ItemStruct(..) | hir::ItemEnum(..) |
272 hir::ItemDefaultImpl(..) => {}
275 ast_map::NodeTraitItem(trait_method) => {
276 match trait_method.node {
277 hir::ConstTraitItem(_, None) |
278 hir::MethodTraitItem(_, None) => {
279 // Keep going, nothing to get exported
281 hir::ConstTraitItem(_, Some(ref expr)) => {
282 self.visit_expr(&expr);
284 hir::MethodTraitItem(_, Some(ref body)) => {
285 intravisit::walk_block(self, body);
287 hir::TypeTraitItem(..) => {}
290 ast_map::NodeImplItem(impl_item) => {
291 match impl_item.node {
292 hir::ImplItemKind::Const(_, ref expr) => {
293 self.visit_expr(&expr);
295 hir::ImplItemKind::Method(ref sig, ref body) => {
296 let did = self.tcx.map.get_parent_did(search_item);
297 if method_might_be_inlined(self.tcx, sig, impl_item, did) {
298 intravisit::walk_block(self, body)
301 hir::ImplItemKind::Type(_) => {}
304 // Nothing to recurse on for these
305 ast_map::NodeForeignItem(_) |
306 ast_map::NodeVariant(_) |
307 ast_map::NodeStructCtor(_) => {}
309 bug!("found unexpected thingy in worklist: {}",
310 self.tcx.map.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> {
325 access_levels: &'a privacy::AccessLevels,
326 worklist: &'a mut Vec<ast::NodeId>,
329 impl<'a, 'v> Visitor<'v> for CollectPrivateImplItemsVisitor<'a> {
330 fn visit_item(&mut self, item: &hir::Item) {
331 // We need only trait impls here, not inherent impls, and only non-exported ones
332 if let hir::ItemImpl(_, _, _, Some(_), _, ref impl_items) = item.node {
333 if !self.access_levels.is_reachable(item.id) {
334 for impl_item in impl_items {
335 self.worklist.push(impl_item.id);
342 pub fn find_reachable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
343 access_levels: &privacy::AccessLevels)
345 let _task = tcx.dep_graph.in_task(DepNode::Reachability);
347 let mut reachable_context = ReachableContext::new(tcx);
349 // Step 1: Seed the worklist with all nodes which were found to be public as
350 // a result of the privacy pass along with all local lang items and impl items.
351 // If other crates link to us, they're going to expect to be able to
352 // use the lang items, so we need to be sure to mark them as
354 for (id, _) in &access_levels.map {
355 reachable_context.worklist.push(*id);
357 for item in tcx.lang_items.items().iter() {
358 if let Some(did) = *item {
359 if let Some(node_id) = tcx.map.as_local_node_id(did) {
360 reachable_context.worklist.push(node_id);
365 let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
366 access_levels: access_levels,
367 worklist: &mut reachable_context.worklist,
369 tcx.map.krate().visit_all_items(&mut collect_private_impl_items);
372 // Step 2: Mark all symbols that the symbols on the worklist touch.
373 reachable_context.propagate();
375 // Return the set of reachable symbols.
376 reachable_context.reachable_symbols