rust/src/librustc/middle/reachable.rs

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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Finds items that are externally reachable, to determine which items
// need to have their metadata (and possibly their AST) serialized.
// All items that can be referred to through an exported name are
// reachable, and when a reachable thing is inline or generic, it
// makes all other generics or inline functions that it references
// reachable as well.
use middle::ty;
use middle::typeck;
use middle::privacy;
use middle::resolve;
use std::hashmap::HashSet;
use syntax::ast;
use syntax::ast_map;
use syntax::ast_util::{def_id_of_def, is_local, local_def};
use syntax::attr;
use syntax::parse::token;
use syntax::visit::Visitor;
use syntax::visit;
// Returns true if the given set of attributes contains the `#[inline]`
// attribute.
fn attributes_specify_inlining(attrs: &[ast::Attribute]) -> bool {
attr::contains_name(attrs, "inline")
}
// Returns true if the given set of generics implies that the item it's
// associated with must be inlined.
fn generics_require_inlining(generics: &ast::Generics) -> bool {
!generics.ty_params.is_empty()
}
// Returns true if the given item must be inlined because it may be
// monomorphized or it was marked with `#[inline]`. This will only return
// true for functions.
fn item_might_be_inlined(item: @ast::item) -> bool {
if attributes_specify_inlining(item.attrs) {
return true
}
match item.node {
ast::item_impl(ref generics, _, _, _) |
ast::item_fn(_, _, _, ref generics, _) => {
generics_require_inlining(generics)
}
_ => false,
}
}
// Returns true if the given type method must be inlined because it may be
// monomorphized or it was marked with `#[inline]`.
fn ty_method_might_be_inlined(ty_method: &ast::TypeMethod) -> bool {
attributes_specify_inlining(ty_method.attrs) ||
generics_require_inlining(&ty_method.generics)
}
fn method_might_be_inlined(tcx: ty::ctxt, method: &ast::method,
impl_src: ast::DefId) -> bool {
if attributes_specify_inlining(method.attrs) ||
generics_require_inlining(&method.generics) {
return true
}
if is_local(impl_src) {
match tcx.items.find(&impl_src.node) {
Some(&ast_map::node_item(item, _)) => item_might_be_inlined(item),
Some(*) | None => {
tcx.sess.span_bug(method.span, "impl did is not an item")
}
}
} else {
tcx.sess.span_bug(method.span, "found a foreign impl as a parent of a \
local method")
}
}
// Returns true if the given trait method must be inlined because it may be
// monomorphized or it was marked with `#[inline]`.
fn trait_method_might_be_inlined(trait_method: &ast::trait_method) -> bool {
match *trait_method {
ast::required(ref ty_method) => ty_method_might_be_inlined(ty_method),
ast::provided(_) => true
}
}
// Information needed while computing reachability.
struct ReachableContext {
// The type context.
tcx: ty::ctxt,
// The method map, which links node IDs of method call expressions to the
// methods they've been resolved to.
method_map: typeck::method_map,
// The set of items which must be exported in the linkage sense.
reachable_symbols: @mut HashSet<ast::NodeId>,
// A worklist of item IDs. Each item ID in this worklist will be inlined
// and will be scanned for further references.
worklist: @mut ~[ast::NodeId],
// Known reexports of modules
exp_map2: resolve::ExportMap2,
}
struct MarkSymbolVisitor {
worklist: @mut ~[ast::NodeId],
method_map: typeck::method_map,
tcx: ty::ctxt,
reachable_symbols: @mut HashSet<ast::NodeId>,
}
impl Visitor<()> for MarkSymbolVisitor {
fn visit_expr(&mut self, expr:@ast::Expr, _:()) {
match expr.node {
ast::ExprPath(_) => {
let def = match self.tcx.def_map.find(&expr.id) {
Some(&def) => def,
None => {
self.tcx.sess.span_bug(expr.span,
"def ID not in def map?!")
}
};
let def_id = def_id_of_def(def);
if ReachableContext::
def_id_represents_local_inlined_item(self.tcx, def_id) {
self.worklist.push(def_id.node)
}
self.reachable_symbols.insert(def_id.node);
}
ast::ExprMethodCall(*) => {
match self.method_map.find(&expr.id) {
Some(&typeck::method_map_entry {
origin: typeck::method_static(def_id),
_
}) => {
if ReachableContext::
def_id_represents_local_inlined_item(
self.tcx,
def_id) {
self.worklist.push(def_id.node)
}
self.reachable_symbols.insert(def_id.node);
}
Some(_) => {}
None => {
self.tcx.sess.span_bug(expr.span,
"method call expression \
not in method map?!")
}
}
}
_ => {}
}
visit::walk_expr(self, expr, ())
}
fn visit_item(&mut self, _item: @ast::item, _: ()) {
// Do not recurse into items. These items will be added to the worklist
// and recursed into manually if necessary.
}
}
impl ReachableContext {
// Creates a new reachability computation context.
fn new(tcx: ty::ctxt, method_map: typeck::method_map,
exp_map2: resolve::ExportMap2) -> ReachableContext {
ReachableContext {
tcx: tcx,
method_map: method_map,
reachable_symbols: @mut HashSet::new(),
worklist: @mut ~[],
exp_map2: exp_map2,
}
}
// Returns true if the given def ID represents a local item that is
// eligible for inlining and false otherwise.
fn def_id_represents_local_inlined_item(tcx: ty::ctxt, def_id: ast::DefId)
-> bool {
if def_id.crate != ast::LOCAL_CRATE {
return false
}
let node_id = def_id.node;
match tcx.items.find(&node_id) {
Some(&ast_map::node_item(item, _)) => {
match item.node {
ast::item_fn(*) => item_might_be_inlined(item),
_ => false,
}
}
Some(&ast_map::node_trait_method(trait_method, _, _)) => {
match *trait_method {
ast::required(_) => false,
ast::provided(_) => true,
}
}
Some(&ast_map::node_method(method, impl_did, _)) => {
if generics_require_inlining(&method.generics) ||
attributes_specify_inlining(method.attrs) {
true
} else {
// Check the impl. If the generics on the self type of the
// impl require inlining, this method does too.
assert!(impl_did.crate == ast::LOCAL_CRATE);
match tcx.items.find(&impl_did.node) {
Some(&ast_map::node_item(item, _)) => {
match item.node {
ast::item_impl(ref generics, _, _, _) => {
generics_require_inlining(generics)
}
_ => false
}
}
Some(_) => {
tcx.sess.span_bug(method.span,
"method is not inside an \
impl?!")
}
None => {
tcx.sess.span_bug(method.span,
"the impl that this method is \
supposedly inside of doesn't \
exist in the AST map?!")
}
}
}
}
Some(_) => false,
None => false // This will happen for default methods.
}
}
// Helper function to set up a visitor for `propagate()` below.
fn init_visitor(&self) -> MarkSymbolVisitor {
let (worklist, method_map) = (self.worklist, self.method_map);
let (tcx, reachable_symbols) = (self.tcx, self.reachable_symbols);
MarkSymbolVisitor {
worklist: worklist,
method_map: method_map,
tcx: tcx,
reachable_symbols: reachable_symbols,
}
}
fn propagate_mod(&self, id: ast::NodeId) {
match self.exp_map2.find(&id) {
Some(l) => {
for reexport in l.iter() {
if reexport.reexport && is_local(reexport.def_id) {
self.worklist.push(reexport.def_id.node);
}
}
}
None => {}
}
}
// Step 2: Mark all symbols that the symbols on the worklist touch.
fn propagate(&self) {
let mut visitor = self.init_visitor();
let mut scanned = HashSet::new();
while self.worklist.len() > 0 {
let search_item = self.worklist.pop();
if scanned.contains(&search_item) {
continue
}
scanned.insert(search_item);
self.reachable_symbols.insert(search_item);
// Find the AST block corresponding to the item and visit it,
// marking all path expressions that resolve to something
// interesting.
match self.tcx.items.find(&search_item) {
Some(&ast_map::node_item(item, _)) => {
match item.node {
ast::item_fn(_, _, _, _, ref search_block) => {
if item_might_be_inlined(item) {
visit::walk_block(&mut visitor, search_block, ())
}
}
// Our recursion into modules involves looking up their
// public reexports and the destinations of those
// exports. Privacy will put them in the worklist, but
// we won't find them in the ast_map, so this is where
// we deal with publicly re-exported items instead.
ast::item_mod(*) => self.propagate_mod(item.id),
// Implementations of exported structs/enums need to get
// added to the worklist (as all their methods should be
// accessible)
ast::item_struct(*) | ast::item_enum(*) => {
let def = local_def(item.id);
let impls = match self.tcx.inherent_impls.find(&def) {
Some(&impls) => impls,
None => continue
};
for imp in impls.iter() {
if is_local(imp.did) {
self.worklist.push(imp.did.node);
}
}
}
// Propagate through this impl
ast::item_impl(_, _, _, ref methods) => {
for method in methods.iter() {
self.worklist.push(method.id);
}
}
// Default methods of exported traits need to all be
// accessible.
ast::item_trait(_, _, ref methods) => {
for method in methods.iter() {
match *method {
ast::required(*) => {}
ast::provided(ref method) => {
self.worklist.push(method.id);
}
}
}
}
// These are normal, nothing reachable about these
// inherently and their children are already in the
// worklist
ast::item_static(*) | ast::item_ty(*) |
ast::item_foreign_mod(*) => {}
_ => {
self.tcx.sess.span_bug(item.span,
"found non-function item \
in worklist?!")
}
}
}
Some(&ast_map::node_trait_method(trait_method, _, _)) => {
match *trait_method {
ast::required(*) => {
// Keep going, nothing to get exported
}
ast::provided(ref method) => {
visit::walk_block(&mut visitor, &method.body, ())
}
}
}
Some(&ast_map::node_method(method, did, _)) => {
if method_might_be_inlined(self.tcx, method, did) {
visit::walk_block(&mut visitor, &method.body, ())
}
}
// Nothing to recurse on for these
Some(&ast_map::node_foreign_item(*)) |
Some(&ast_map::node_variant(*)) |
Some(&ast_map::node_struct_ctor(*)) => {}
Some(_) => {
let ident_interner = token::get_ident_interner();
let desc = ast_map::node_id_to_str(self.tcx.items,
search_item,
ident_interner);
2013-09-28 00:38:08 -05:00
self.tcx.sess.bug(format!("found unexpected thingy in \
worklist: {}",
desc))
}
None if search_item == ast::CRATE_NODE_ID => {
self.propagate_mod(search_item);
}
None => {
2013-09-28 00:38:08 -05:00
self.tcx.sess.bug(format!("found unmapped ID in worklist: \
{}",
search_item))
}
}
}
}
// Step 3: Mark all destructors as reachable.
//
// XXX(pcwalton): This is a conservative overapproximation, but fixing
// this properly would result in the necessity of computing *type*
// reachability, which might result in a compile time loss.
fn mark_destructors_reachable(&self) {
for (_, destructor_def_id) in self.tcx.destructor_for_type.iter() {
if destructor_def_id.crate == ast::LOCAL_CRATE {
self.reachable_symbols.insert(destructor_def_id.node);
}
}
}
}
pub fn find_reachable(tcx: ty::ctxt,
method_map: typeck::method_map,
exp_map2: resolve::ExportMap2,
exported_items: &privacy::ExportedItems)
-> @mut HashSet<ast::NodeId> {
let reachable_context = ReachableContext::new(tcx, method_map, exp_map2);
// Step 1: Seed the worklist with all nodes which were found to be public as
// a result of the privacy pass
for &id in exported_items.iter() {
reachable_context.worklist.push(id);
}
// Step 2: Mark all symbols that the symbols on the worklist touch.
reachable_context.propagate();
// Step 3: Mark all destructors as reachable.
reachable_context.mark_destructors_reachable();
// Return the set of reachable symbols.
reachable_context.reachable_symbols
}