388 lines
15 KiB
Rust
388 lines
15 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 dep_graph::DepNode;
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use front::map as ast_map;
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use middle::def::Def;
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use middle::def_id::DefId;
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use middle::ty::{self, TyCtxt};
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use middle::privacy;
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use session::config;
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use util::nodemap::NodeSet;
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use std::collections::HashSet;
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use syntax::abi::Abi;
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use syntax::ast;
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use syntax::attr;
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use rustc_front::hir;
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use rustc_front::intravisit::Visitor;
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use rustc_front::intravisit;
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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: &hir::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: &hir::Item) -> bool {
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if attr::requests_inline(&item.attrs) {
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return true
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}
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match item.node {
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hir::ItemImpl(_, _, ref generics, _, _, _) |
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hir::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: &TyCtxt, sig: &hir::MethodSig,
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impl_item: &hir::ImplItem,
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impl_src: DefId) -> bool {
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if attr::requests_inline(&impl_item.attrs) ||
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generics_require_inlining(&sig.generics) {
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return true
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}
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if let Some(impl_node_id) = tcx.map.as_local_node_id(impl_src) {
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match tcx.map.find(impl_node_id) {
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Some(ast_map::NodeItem(item)) =>
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item_might_be_inlined(&item),
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Some(..) | None =>
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tcx.sess.span_bug(impl_item.span, "impl did is not an item")
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}
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} else {
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tcx.sess.span_bug(impl_item.span, "found a foreign impl as a parent of a 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<'a, 'tcx: 'a> {
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// The type context.
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tcx: &'a TyCtxt<'tcx>,
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// The set of items which must be exported in the linkage sense.
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reachable_symbols: NodeSet,
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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: Vec<ast::NodeId>,
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// Whether any output of this compilation is a library
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any_library: bool,
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}
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impl<'a, 'tcx, 'v> Visitor<'v> for ReachableContext<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &hir::Expr) {
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match expr.node {
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hir::ExprPath(..) => {
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let def = match self.tcx.def_map.borrow().get(&expr.id) {
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Some(d) => d.full_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.def_id();
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if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
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if self.def_id_represents_local_inlined_item(def_id) {
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self.worklist.push(node_id);
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} else {
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match def {
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// If this path leads to a constant, then we need to
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// recurse into the constant to continue finding
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// items that are reachable.
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Def::Const(..) | Def::AssociatedConst(..) => {
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self.worklist.push(node_id);
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}
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// If this wasn't a static, then the destination is
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// surely reachable.
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_ => {
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self.reachable_symbols.insert(node_id);
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}
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}
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}
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}
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}
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hir::ExprMethodCall(..) => {
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let method_call = ty::MethodCall::expr(expr.id);
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let def_id = self.tcx.tables.borrow().method_map[&method_call].def_id;
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// Mark the trait item (and, possibly, its default impl) as reachable
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// Or mark inherent impl item as reachable
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if let Some(node_id) = self.tcx.map.as_local_node_id(def_id) {
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if self.def_id_represents_local_inlined_item(def_id) {
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self.worklist.push(node_id)
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}
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self.reachable_symbols.insert(node_id);
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}
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}
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_ => {}
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}
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intravisit::walk_expr(self, expr)
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}
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}
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impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
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// Creates a new reachability computation context.
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fn new(tcx: &'a TyCtxt<'tcx>) -> ReachableContext<'a, 'tcx> {
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let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
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*ty != config::CrateTypeExecutable
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});
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ReachableContext {
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tcx: tcx,
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reachable_symbols: NodeSet(),
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worklist: Vec::new(),
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any_library: any_library,
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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(&self, def_id: DefId) -> bool {
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let node_id = match self.tcx.map.as_local_node_id(def_id) {
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Some(node_id) => node_id,
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None => { return false; }
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};
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match self.tcx.map.find(node_id) {
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Some(ast_map::NodeItem(item)) => {
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match item.node {
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hir::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::NodeTraitItem(trait_method)) => {
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match trait_method.node {
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hir::ConstTraitItem(_, ref default) => default.is_some(),
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hir::MethodTraitItem(_, ref body) => body.is_some(),
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hir::TypeTraitItem(..) => false,
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}
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}
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Some(ast_map::NodeImplItem(impl_item)) => {
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match impl_item.node {
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hir::ImplItemKind::Const(..) => true,
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hir::ImplItemKind::Method(ref sig, _) => {
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if generics_require_inlining(&sig.generics) ||
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attr::requests_inline(&impl_item.attrs) {
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true
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} else {
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let impl_did = self.tcx
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.map
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.get_parent_did(node_id);
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// Check the impl. If the generics on the self
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// type of the impl require inlining, this method
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// does too.
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let impl_node_id = self.tcx.map.as_local_node_id(impl_did).unwrap();
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match self.tcx.map.expect_item(impl_node_id).node {
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hir::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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}
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hir::ImplItemKind::Type(_) => false,
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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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// Step 2: Mark all symbols that the symbols on the worklist touch.
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fn propagate(&mut self) {
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let mut scanned = HashSet::new();
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loop {
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let search_item = match self.worklist.pop() {
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Some(item) => item,
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None => break,
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};
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if !scanned.insert(search_item) {
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continue
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}
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if let Some(ref item) = self.tcx.map.find(search_item) {
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self.propagate_node(item, search_item);
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}
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}
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}
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fn propagate_node(&mut self, node: &ast_map::Node,
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search_item: ast::NodeId) {
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if !self.any_library {
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// If we are building an executable, only explicitly extern
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// types need to be exported.
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if let ast_map::NodeItem(item) = *node {
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let reachable = if let hir::ItemFn(_, _, _, abi, _, _) = item.node {
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abi != Abi::Rust
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} else {
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false
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};
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let is_extern = attr::contains_extern_indicator(&self.tcx.sess.diagnostic(),
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&item.attrs);
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if reachable || is_extern {
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self.reachable_symbols.insert(search_item);
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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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self.reachable_symbols.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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hir::ItemFn(_, _, _, _, _, ref search_block) => {
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if item_might_be_inlined(&item) {
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intravisit::walk_block(self, &search_block)
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}
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}
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// Reachable constants will be inlined into other crates
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// unconditionally, so we need to make sure that their
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// contents are also reachable.
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hir::ItemConst(_, ref init) => {
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self.visit_expr(&init);
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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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hir::ItemExternCrate(_) | hir::ItemUse(_) |
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hir::ItemTy(..) | hir::ItemStatic(_, _, _) |
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hir::ItemMod(..) | hir::ItemForeignMod(..) |
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hir::ItemImpl(..) | hir::ItemTrait(..) |
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hir::ItemStruct(..) | hir::ItemEnum(..) |
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hir::ItemDefaultImpl(..) => {}
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}
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}
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ast_map::NodeTraitItem(trait_method) => {
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match trait_method.node {
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hir::ConstTraitItem(_, None) |
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hir::MethodTraitItem(_, None) => {
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// Keep going, nothing to get exported
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}
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hir::ConstTraitItem(_, Some(ref expr)) => {
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self.visit_expr(&expr);
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}
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hir::MethodTraitItem(_, Some(ref body)) => {
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intravisit::walk_block(self, body);
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}
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hir::TypeTraitItem(..) => {}
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}
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}
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ast_map::NodeImplItem(impl_item) => {
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match impl_item.node {
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hir::ImplItemKind::Const(_, ref expr) => {
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self.visit_expr(&expr);
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}
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hir::ImplItemKind::Method(ref sig, ref body) => {
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let did = self.tcx.map.get_parent_did(search_item);
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if method_might_be_inlined(self.tcx, sig, impl_item, did) {
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intravisit::walk_block(self, body)
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}
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}
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hir::ImplItemKind::Type(_) => {}
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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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self.tcx
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.sess
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.bug(&format!("found unexpected thingy in worklist: {}",
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self.tcx
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.map
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.node_to_string(search_item)))
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}
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}
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}
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}
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// Some methods from non-exported (completely private) trait impls still have to be
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// reachable if they are called from inlinable code. Generally, it's not known until
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// monomorphization if a specific trait impl item can be reachable or not. So, we
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// conservatively mark all of them as reachable.
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// FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
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// items of non-exported traits (or maybe all local traits?) unless their respective
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// trait items are used from inlinable code through method call syntax or UFCS, or their
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// trait is a lang item.
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struct CollectPrivateImplItemsVisitor<'a> {
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access_levels: &'a privacy::AccessLevels,
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worklist: &'a mut Vec<ast::NodeId>,
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}
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impl<'a, 'v> Visitor<'v> for CollectPrivateImplItemsVisitor<'a> {
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fn visit_item(&mut self, item: &hir::Item) {
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// We need only trait impls here, not inherent impls, and only non-exported ones
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if let hir::ItemImpl(_, _, _, Some(_), _, ref impl_items) = item.node {
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if !self.access_levels.is_reachable(item.id) {
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for impl_item in impl_items {
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self.worklist.push(impl_item.id);
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}
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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: &TyCtxt,
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access_levels: &privacy::AccessLevels)
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-> NodeSet {
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let _task = tcx.dep_graph.in_task(DepNode::Reachability);
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let mut reachable_context = ReachableContext::new(tcx);
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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 along with all local lang items and impl items.
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// If other crates link to us, they're going to expect to be able to
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// use the lang items, so we need to be sure to mark them as
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// exported.
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for (id, _) in &access_levels.map {
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reachable_context.worklist.push(*id);
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}
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for item in tcx.lang_items.items().iter() {
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if let Some(did) = *item {
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if let Some(node_id) = tcx.map.as_local_node_id(did) {
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reachable_context.worklist.push(node_id);
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}
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}
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}
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{
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let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
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access_levels: access_levels,
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worklist: &mut reachable_context.worklist,
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};
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tcx.map.krate().visit_all_items(&mut collect_private_impl_items);
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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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// Return the set of reachable symbols.
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reachable_context.reachable_symbols
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}
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