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 front::map as ast_map;
21 use middle::def_id::DefId;
22 use middle::ty::{self, TyCtxt};
25 use util::nodemap::NodeSet;
27 use std::collections::HashSet;
32 use rustc_front::intravisit::Visitor;
33 use rustc_front::intravisit;
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(tcx: &TyCtxt, sig: &hir::MethodSig,
59 impl_item: &hir::ImplItem,
60 impl_src: DefId) -> bool {
61 if attr::requests_inline(&impl_item.attrs) ||
62 generics_require_inlining(&sig.generics) {
65 if let Some(impl_node_id) = tcx.map.as_local_node_id(impl_src) {
66 match tcx.map.find(impl_node_id) {
67 Some(ast_map::NodeItem(item)) =>
68 item_might_be_inlined(&item),
70 tcx.sess.span_bug(impl_item.span, "impl did is not an item")
73 tcx.sess.span_bug(impl_item.span, "found a foreign impl as a parent of a local method")
77 // Information needed while computing reachability.
78 struct ReachableContext<'a, 'tcx: 'a> {
80 tcx: &'a TyCtxt<'tcx>,
81 // The set of items which must be exported in the linkage sense.
82 reachable_symbols: NodeSet,
83 // A worklist of item IDs. Each item ID in this worklist will be inlined
84 // and will be scanned for further references.
85 worklist: Vec<ast::NodeId>,
86 // Whether any output of this compilation is a library
90 impl<'a, 'tcx, 'v> Visitor<'v> for ReachableContext<'a, 'tcx> {
91 fn visit_expr(&mut self, expr: &hir::Expr) {
93 hir::ExprPath(..) => {
94 let def = match self.tcx.def_map.borrow().get(&expr.id) {
95 Some(d) => d.full_def(),
97 self.tcx.sess.span_bug(expr.span,
98 "def ID not in def map?!")
102 let def_id = def.def_id();
103 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
104 if self.def_id_represents_local_inlined_item(def_id) {
105 self.worklist.push(node_id);
108 // If this path leads to a constant, then we need to
109 // recurse into the constant to continue finding
110 // items that are reachable.
111 Def::Const(..) | Def::AssociatedConst(..) => {
112 self.worklist.push(node_id);
115 // If this wasn't a static, then the destination is
118 self.reachable_symbols.insert(node_id);
124 hir::ExprMethodCall(..) => {
125 let method_call = ty::MethodCall::expr(expr.id);
126 let def_id = self.tcx.tables.borrow().method_map[&method_call].def_id;
128 // Mark the trait item (and, possibly, its default impl) as reachable
129 // Or mark inherent impl item as reachable
130 if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
131 if self.def_id_represents_local_inlined_item(def_id) {
132 self.worklist.push(node_id)
134 self.reachable_symbols.insert(node_id);
140 intravisit::walk_expr(self, expr)
144 impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
145 // Creates a new reachability computation context.
146 fn new(tcx: &'a TyCtxt<'tcx>) -> ReachableContext<'a, 'tcx> {
147 let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
148 *ty != config::CrateTypeExecutable
152 reachable_symbols: NodeSet(),
153 worklist: Vec::new(),
154 any_library: any_library,
158 // Returns true if the given def ID represents a local item that is
159 // eligible for inlining and false otherwise.
160 fn def_id_represents_local_inlined_item(&self, def_id: DefId) -> bool {
161 let node_id = match self.tcx.map.as_local_node_id(def_id) {
162 Some(node_id) => node_id,
163 None => { return false; }
166 match self.tcx.map.find(node_id) {
167 Some(ast_map::NodeItem(item)) => {
169 hir::ItemFn(..) => item_might_be_inlined(&item),
173 Some(ast_map::NodeTraitItem(trait_method)) => {
174 match trait_method.node {
175 hir::ConstTraitItem(_, ref default) => default.is_some(),
176 hir::MethodTraitItem(_, ref body) => body.is_some(),
177 hir::TypeTraitItem(..) => false,
180 Some(ast_map::NodeImplItem(impl_item)) => {
181 match impl_item.node {
182 hir::ImplItemKind::Const(..) => true,
183 hir::ImplItemKind::Method(ref sig, _) => {
184 if generics_require_inlining(&sig.generics) ||
185 attr::requests_inline(&impl_item.attrs) {
188 let impl_did = self.tcx
190 .get_parent_did(node_id);
191 // Check the impl. If the generics on the self
192 // type of the impl require inlining, this method
194 let impl_node_id = self.tcx.map.as_local_node_id(impl_did).unwrap();
195 match self.tcx.map.expect_item(impl_node_id).node {
196 hir::ItemImpl(_, _, ref generics, _, _, _) => {
197 generics_require_inlining(generics)
203 hir::ImplItemKind::Type(_) => false,
207 None => false // This will happen for default methods.
211 // Step 2: Mark all symbols that the symbols on the worklist touch.
212 fn propagate(&mut self) {
213 let mut scanned = HashSet::new();
215 let search_item = match self.worklist.pop() {
219 if !scanned.insert(search_item) {
223 if let Some(ref item) = self.tcx.map.find(search_item) {
224 self.propagate_node(item, search_item);
229 fn propagate_node(&mut self, node: &ast_map::Node,
230 search_item: ast::NodeId) {
231 if !self.any_library {
232 // If we are building an executable, only explicitly extern
233 // types need to be exported.
234 if let ast_map::NodeItem(item) = *node {
235 let reachable = if let hir::ItemFn(_, _, _, abi, _, _) = item.node {
240 let is_extern = attr::contains_extern_indicator(&self.tcx.sess.diagnostic(),
242 if reachable || is_extern {
243 self.reachable_symbols.insert(search_item);
247 // If we are building a library, then reachable symbols will
248 // continue to participate in linkage after this product is
249 // produced. In this case, we traverse the ast node, recursing on
250 // all reachable nodes from this one.
251 self.reachable_symbols.insert(search_item);
255 ast_map::NodeItem(item) => {
257 hir::ItemFn(_, _, _, _, _, ref search_block) => {
258 if item_might_be_inlined(&item) {
259 intravisit::walk_block(self, &search_block)
263 // Reachable constants will be inlined into other crates
264 // unconditionally, so we need to make sure that their
265 // contents are also reachable.
266 hir::ItemConst(_, ref init) => {
267 self.visit_expr(&init);
270 // These are normal, nothing reachable about these
271 // inherently and their children are already in the
272 // worklist, as determined by the privacy pass
273 hir::ItemExternCrate(_) | hir::ItemUse(_) |
274 hir::ItemTy(..) | hir::ItemStatic(_, _, _) |
275 hir::ItemMod(..) | hir::ItemForeignMod(..) |
276 hir::ItemImpl(..) | hir::ItemTrait(..) |
277 hir::ItemStruct(..) | hir::ItemEnum(..) |
278 hir::ItemDefaultImpl(..) => {}
281 ast_map::NodeTraitItem(trait_method) => {
282 match trait_method.node {
283 hir::ConstTraitItem(_, None) |
284 hir::MethodTraitItem(_, None) => {
285 // Keep going, nothing to get exported
287 hir::ConstTraitItem(_, Some(ref expr)) => {
288 self.visit_expr(&expr);
290 hir::MethodTraitItem(_, Some(ref body)) => {
291 intravisit::walk_block(self, body);
293 hir::TypeTraitItem(..) => {}
296 ast_map::NodeImplItem(impl_item) => {
297 match impl_item.node {
298 hir::ImplItemKind::Const(_, ref expr) => {
299 self.visit_expr(&expr);
301 hir::ImplItemKind::Method(ref sig, ref body) => {
302 let did = self.tcx.map.get_parent_did(search_item);
303 if method_might_be_inlined(self.tcx, sig, impl_item, did) {
304 intravisit::walk_block(self, body)
307 hir::ImplItemKind::Type(_) => {}
310 // Nothing to recurse on for these
311 ast_map::NodeForeignItem(_) |
312 ast_map::NodeVariant(_) |
313 ast_map::NodeStructCtor(_) => {}
317 .bug(&format!("found unexpected thingy in worklist: {}",
320 .node_to_string(search_item)))
326 // Some methods from non-exported (completely private) trait impls still have to be
327 // reachable if they are called from inlinable code. Generally, it's not known until
328 // monomorphization if a specific trait impl item can be reachable or not. So, we
329 // conservatively mark all of them as reachable.
330 // FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
331 // items of non-exported traits (or maybe all local traits?) unless their respective
332 // trait items are used from inlinable code through method call syntax or UFCS, or their
333 // trait is a lang item.
334 struct CollectPrivateImplItemsVisitor<'a> {
335 access_levels: &'a privacy::AccessLevels,
336 worklist: &'a mut Vec<ast::NodeId>,
339 impl<'a, 'v> Visitor<'v> for CollectPrivateImplItemsVisitor<'a> {
340 fn visit_item(&mut self, item: &hir::Item) {
341 // We need only trait impls here, not inherent impls, and only non-exported ones
342 if let hir::ItemImpl(_, _, _, Some(_), _, ref impl_items) = item.node {
343 if !self.access_levels.is_reachable(item.id) {
344 for impl_item in impl_items {
345 self.worklist.push(impl_item.id);
352 pub fn find_reachable(tcx: &TyCtxt,
353 access_levels: &privacy::AccessLevels)
355 let _task = tcx.dep_graph.in_task(DepNode::Reachability);
357 let mut reachable_context = ReachableContext::new(tcx);
359 // Step 1: Seed the worklist with all nodes which were found to be public as
360 // a result of the privacy pass along with all local lang items and impl items.
361 // If other crates link to us, they're going to expect to be able to
362 // use the lang items, so we need to be sure to mark them as
364 for (id, _) in &access_levels.map {
365 reachable_context.worklist.push(*id);
367 for item in tcx.lang_items.items().iter() {
368 if let Some(did) = *item {
369 if let Some(node_id) = tcx.map.as_local_node_id(did) {
370 reachable_context.worklist.push(node_id);
375 let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
376 access_levels: access_levels,
377 worklist: &mut reachable_context.worklist,
379 tcx.map.krate().visit_all_items(&mut collect_private_impl_items);
382 // Step 2: Mark all symbols that the symbols on the worklist touch.
383 reachable_context.propagate();
385 // Return the set of reachable symbols.
386 reachable_context.reachable_symbols