444 lines
18 KiB
Rust
444 lines
18 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Finds items that are externally reachable, to determine which items
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// need to have their metadata (and possibly their AST) serialized.
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// All items that can be referred to through an exported name are
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// reachable, and when a reachable thing is inline or generic, it
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// makes all other generics or inline functions that it references
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// reachable as well.
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use middle::ty;
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use middle::typeck;
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use middle::privacy;
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use std::cell::RefCell;
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use std::hashmap::HashSet;
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use syntax::ast;
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use syntax::ast_map;
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use syntax::ast_util::{def_id_of_def, is_local};
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use syntax::attr;
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use syntax::parse::token;
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use syntax::visit::Visitor;
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use syntax::visit;
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// Returns true if the given set of attributes contains the `#[inline]`
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// attribute.
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fn attributes_specify_inlining(attrs: &[ast::Attribute]) -> bool {
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attr::contains_name(attrs, "inline")
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}
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// Returns true if the given set of generics implies that the item it's
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// associated with must be inlined.
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fn generics_require_inlining(generics: &ast::Generics) -> bool {
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!generics.ty_params.is_empty()
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}
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// Returns true if the given item must be inlined because it may be
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// monomorphized or it was marked with `#[inline]`. This will only return
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// true for functions.
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fn item_might_be_inlined(item: &ast::Item) -> bool {
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if attributes_specify_inlining(item.attrs) {
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return true
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}
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match item.node {
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ast::ItemImpl(ref generics, _, _, _) |
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ast::ItemFn(_, _, _, ref generics, _) => {
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generics_require_inlining(generics)
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}
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_ => false,
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}
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}
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fn method_might_be_inlined(tcx: ty::ctxt, method: &ast::Method,
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impl_src: ast::DefId) -> bool {
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if attributes_specify_inlining(method.attrs) ||
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generics_require_inlining(&method.generics) {
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return true
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}
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if is_local(impl_src) {
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{
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match tcx.items.find(impl_src.node) {
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Some(ast_map::NodeItem(item, _)) => {
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item_might_be_inlined(item)
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}
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Some(..) | None => {
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tcx.sess.span_bug(method.span, "impl did is not an item")
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}
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}
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}
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} else {
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tcx.sess.span_bug(method.span, "found a foreign impl as a parent of a \
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local method")
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}
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}
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// Information needed while computing reachability.
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struct ReachableContext {
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// The type context.
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tcx: ty::ctxt,
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// The method map, which links node IDs of method call expressions to the
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// methods they've been resolved to.
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method_map: typeck::method_map,
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// The set of items which must be exported in the linkage sense.
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reachable_symbols: @RefCell<HashSet<ast::NodeId>>,
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// A worklist of item IDs. Each item ID in this worklist will be inlined
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// and will be scanned for further references.
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worklist: @RefCell<~[ast::NodeId]>,
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}
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struct MarkSymbolVisitor {
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worklist: @RefCell<~[ast::NodeId]>,
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method_map: typeck::method_map,
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tcx: ty::ctxt,
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reachable_symbols: @RefCell<HashSet<ast::NodeId>>,
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}
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impl Visitor<()> for MarkSymbolVisitor {
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fn visit_expr(&mut self, expr: &ast::Expr, _: ()) {
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match expr.node {
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ast::ExprPath(_) => {
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let def_map = self.tcx.def_map.borrow();
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let def = match def_map.get().find(&expr.id) {
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Some(&def) => def,
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None => {
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self.tcx.sess.span_bug(expr.span,
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"def ID not in def map?!")
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}
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};
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let def_id = def_id_of_def(def);
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if is_local(def_id) {
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if ReachableContext::
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def_id_represents_local_inlined_item(self.tcx, def_id) {
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{
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let mut worklist = self.worklist.borrow_mut();
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worklist.get().push(def_id.node)
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}
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} else {
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match def {
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// If this path leads to a static, then we may have
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// to do some work to figure out whether the static
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// is indeed reachable (address_insignificant
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// statics are *never* reachable).
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ast::DefStatic(..) => {
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let mut worklist = self.worklist.borrow_mut();
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worklist.get().push(def_id.node);
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}
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// If this wasn't a static, then this destination is
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// surely reachable.
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_ => {
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let mut reachable_symbols =
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self.reachable_symbols.borrow_mut();
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reachable_symbols.get().insert(def_id.node);
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}
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}
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}
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}
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}
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ast::ExprMethodCall(..) => {
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let method_map = self.method_map.borrow();
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match method_map.get().find(&expr.id) {
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Some(&typeck::method_map_entry {
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origin: typeck::method_static(def_id),
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..
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}) => {
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if is_local(def_id) {
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if ReachableContext::
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def_id_represents_local_inlined_item(
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self.tcx,
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def_id) {
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{
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let mut worklist = self.worklist
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.borrow_mut();
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worklist.get().push(def_id.node)
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}
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}
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{
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let mut reachable_symbols =
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self.reachable_symbols.borrow_mut();
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reachable_symbols.get().insert(def_id.node);
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}
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}
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}
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Some(_) => {}
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None => {
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self.tcx.sess.span_bug(expr.span,
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"method call expression \
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not in method map?!")
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}
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}
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}
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_ => {}
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}
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visit::walk_expr(self, expr, ())
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}
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fn visit_item(&mut self, _item: &ast::Item, _: ()) {
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// Do not recurse into items. These items will be added to the worklist
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// and recursed into manually if necessary.
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}
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}
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impl ReachableContext {
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// Creates a new reachability computation context.
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fn new(tcx: ty::ctxt, method_map: typeck::method_map) -> ReachableContext {
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ReachableContext {
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tcx: tcx,
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method_map: method_map,
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reachable_symbols: @RefCell::new(HashSet::new()),
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worklist: @RefCell::new(~[]),
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}
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}
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// Returns true if the given def ID represents a local item that is
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// eligible for inlining and false otherwise.
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fn def_id_represents_local_inlined_item(tcx: ty::ctxt, def_id: ast::DefId)
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-> bool {
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if def_id.crate != ast::LOCAL_CRATE {
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return false
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}
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let node_id = def_id.node;
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match tcx.items.find(node_id) {
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Some(ast_map::NodeItem(item, _)) => {
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match item.node {
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ast::ItemFn(..) => item_might_be_inlined(item),
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_ => false,
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}
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}
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Some(ast_map::NodeTraitMethod(trait_method, _, _)) => {
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match *trait_method {
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ast::Required(_) => false,
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ast::Provided(_) => true,
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}
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}
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Some(ast_map::NodeMethod(method, impl_did, _)) => {
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if generics_require_inlining(&method.generics) ||
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attributes_specify_inlining(method.attrs) {
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true
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} else {
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// Check the impl. If the generics on the self type of the
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// impl require inlining, this method does too.
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assert!(impl_did.crate == ast::LOCAL_CRATE);
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match tcx.items.find(impl_did.node) {
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Some(ast_map::NodeItem(item, _)) => {
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match item.node {
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ast::ItemImpl(ref generics, _, _, _) => {
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generics_require_inlining(generics)
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}
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_ => false
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}
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}
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Some(_) => {
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tcx.sess.span_bug(method.span,
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"method is not inside an \
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impl?!")
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}
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None => {
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tcx.sess.span_bug(method.span,
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"the impl that this method is \
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supposedly inside of doesn't \
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exist in the AST map?!")
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}
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}
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}
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}
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Some(_) => false,
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None => false // This will happen for default methods.
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}
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}
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// Helper function to set up a visitor for `propagate()` below.
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fn init_visitor(&self) -> MarkSymbolVisitor {
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let (worklist, method_map) = (self.worklist, self.method_map);
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let (tcx, reachable_symbols) = (self.tcx, self.reachable_symbols);
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MarkSymbolVisitor {
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worklist: worklist,
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method_map: method_map,
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tcx: tcx,
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reachable_symbols: reachable_symbols,
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}
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}
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// Step 2: Mark all symbols that the symbols on the worklist touch.
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fn propagate(&self) {
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let mut visitor = self.init_visitor();
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let mut scanned = HashSet::new();
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loop {
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let search_item = {
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let mut worklist = self.worklist.borrow_mut();
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if worklist.get().len() == 0 {
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break
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}
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let search_item = worklist.get().pop().unwrap();
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if scanned.contains(&search_item) {
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continue
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}
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search_item
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};
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scanned.insert(search_item);
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match self.tcx.items.find(search_item) {
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Some(ref item) => self.propagate_node(item, search_item,
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&mut visitor),
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None if search_item == ast::CRATE_NODE_ID => {}
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None => {
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self.tcx.sess.bug(format!("found unmapped ID in worklist: \
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{}",
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search_item))
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}
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}
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}
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}
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fn propagate_node(&self, node: &ast_map::Node,
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search_item: ast::NodeId,
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visitor: &mut MarkSymbolVisitor) {
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if !self.tcx.sess.building_library.get() {
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// If we are building an executable, then there's no need to flag
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// anything as external except for `extern fn` types. These
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// functions may still participate in some form of native interface,
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// but all other rust-only interfaces can be private (they will not
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// participate in linkage after this product is produced)
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match *node {
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ast_map::NodeItem(item, _) => {
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match item.node {
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ast::ItemFn(_, ast::ExternFn, _, _, _) => {
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let mut reachable_symbols =
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self.reachable_symbols.borrow_mut();
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reachable_symbols.get().insert(search_item);
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}
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_ => {}
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}
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}
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_ => {}
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}
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} else {
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// If we are building a library, then reachable symbols will
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// continue to participate in linkage after this product is
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// produced. In this case, we traverse the ast node, recursing on
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// all reachable nodes from this one.
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let mut reachable_symbols = self.reachable_symbols.borrow_mut();
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reachable_symbols.get().insert(search_item);
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}
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match *node {
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ast_map::NodeItem(item, _) => {
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match item.node {
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ast::ItemFn(_, _, _, _, search_block) => {
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if item_might_be_inlined(item) {
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visit::walk_block(visitor, search_block, ())
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}
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}
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// Statics with insignificant addresses are not reachable
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// because they're inlined specially into all other crates.
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ast::ItemStatic(..) => {
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if attr::contains_name(item.attrs,
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"address_insignificant") {
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let mut reachable_symbols =
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self.reachable_symbols.borrow_mut();
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reachable_symbols.get().remove(&search_item);
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}
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}
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// These are normal, nothing reachable about these
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// inherently and their children are already in the
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// worklist, as determined by the privacy pass
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ast::ItemTy(..) |
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ast::ItemMod(..) | ast::ItemForeignMod(..) |
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ast::ItemImpl(..) | ast::ItemTrait(..) |
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ast::ItemStruct(..) | ast::ItemEnum(..) => {}
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_ => {
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self.tcx.sess.span_bug(item.span,
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"found non-function item \
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in worklist?!")
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}
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}
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}
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ast_map::NodeTraitMethod(trait_method, _, _) => {
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match *trait_method {
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ast::Required(..) => {
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// Keep going, nothing to get exported
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}
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ast::Provided(ref method) => {
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visit::walk_block(visitor, method.body, ())
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}
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}
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}
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ast_map::NodeMethod(method, did, _) => {
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if method_might_be_inlined(self.tcx, method, did) {
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visit::walk_block(visitor, method.body, ())
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}
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}
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// Nothing to recurse on for these
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ast_map::NodeForeignItem(..) |
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ast_map::NodeVariant(..) |
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ast_map::NodeStructCtor(..) => {}
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_ => {
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let ident_interner = token::get_ident_interner();
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let desc = ast_map::node_id_to_str(self.tcx.items,
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search_item,
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ident_interner);
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self.tcx.sess.bug(format!("found unexpected thingy in \
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worklist: {}",
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desc))
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}
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}
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}
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// Step 3: Mark all destructors as reachable.
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//
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// FIXME(pcwalton): This is a conservative overapproximation, but fixing
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// this properly would result in the necessity of computing *type*
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// reachability, which might result in a compile time loss.
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fn mark_destructors_reachable(&self) {
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let destructor_for_type = self.tcx.destructor_for_type.borrow();
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for (_, destructor_def_id) in destructor_for_type.get().iter() {
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if destructor_def_id.crate == ast::LOCAL_CRATE {
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let mut reachable_symbols = self.reachable_symbols
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.borrow_mut();
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reachable_symbols.get().insert(destructor_def_id.node);
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}
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}
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}
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}
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pub fn find_reachable(tcx: ty::ctxt,
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method_map: typeck::method_map,
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exported_items: &privacy::ExportedItems)
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-> @RefCell<HashSet<ast::NodeId>> {
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let reachable_context = ReachableContext::new(tcx, method_map);
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// Step 1: Seed the worklist with all nodes which were found to be public as
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// a result of the privacy pass
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for &id in exported_items.iter() {
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let mut worklist = reachable_context.worklist.borrow_mut();
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worklist.get().push(id);
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}
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// Step 2: Mark all symbols that the symbols on the worklist touch.
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reachable_context.propagate();
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// Step 3: Mark all destructors as reachable.
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reachable_context.mark_destructors_reachable();
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// Return the set of reachable symbols.
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reachable_context.reachable_symbols
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}
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