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move_data.rs
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move_data.rs
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// Copyright 2012-2014 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.
/*!
Data structures used for tracking moves. Please see the extensive
comments in the section "Moves and initialization" and in `doc.rs`.
*/
use std::cell::RefCell;
use std::rc::Rc;
use std::uint;
use std::collections::{HashMap, HashSet};
use middle::borrowck::*;
use middle::cfg;
use middle::dataflow::DataFlowContext;
use middle::dataflow::BitwiseOperator;
use middle::dataflow::DataFlowOperator;
use euv = middle::expr_use_visitor;
use middle::ty;
use syntax::ast;
use syntax::ast_util;
use syntax::codemap::Span;
use util::ppaux::Repr;
pub struct MoveData {
/// Move paths. See section "Move paths" in `doc.rs`.
pub paths: RefCell<Vec<MovePath>>,
/// Cache of loan path to move path index, for easy lookup.
pub path_map: RefCell<HashMap<Rc<LoanPath>, MovePathIndex>>,
/// Each move or uninitialized variable gets an entry here.
pub moves: RefCell<Vec<Move>>,
/// Assignments to a variable, like `x = foo`. These are assigned
/// bits for dataflow, since we must track them to ensure that
/// immutable variables are assigned at most once along each path.
pub var_assignments: RefCell<Vec<Assignment>>,
/// Assignments to a path, like `x.f = foo`. These are not
/// assigned dataflow bits, but we track them because they still
/// kill move bits.
pub path_assignments: RefCell<Vec<Assignment>>,
/// Assignments to a variable or path, like `x = foo`, but not `x += foo`.
pub assignee_ids: RefCell<HashSet<ast::NodeId>>,
}
pub struct FlowedMoveData<'a> {
pub move_data: MoveData,
pub dfcx_moves: MoveDataFlow<'a>,
// We could (and maybe should, for efficiency) combine both move
// and assign data flow into one, but this way it's easier to
// distinguish the bits that correspond to moves and assignments.
pub dfcx_assign: AssignDataFlow<'a>
}
/// Index into `MoveData.paths`, used like a pointer
#[deriving(PartialEq)]
pub struct MovePathIndex(uint);
impl MovePathIndex {
fn get(&self) -> uint {
let MovePathIndex(v) = *self; v
}
}
impl Clone for MovePathIndex {
fn clone(&self) -> MovePathIndex {
MovePathIndex(self.get())
}
}
static InvalidMovePathIndex: MovePathIndex =
MovePathIndex(uint::MAX);
/// Index into `MoveData.moves`, used like a pointer
#[deriving(PartialEq)]
pub struct MoveIndex(uint);
impl MoveIndex {
fn get(&self) -> uint {
let MoveIndex(v) = *self; v
}
}
static InvalidMoveIndex: MoveIndex =
MoveIndex(uint::MAX);
pub struct MovePath {
/// Loan path corresponding to this move path
pub loan_path: Rc<LoanPath>,
/// Parent pointer, `InvalidMovePathIndex` if root
pub parent: MovePathIndex,
/// Head of linked list of moves to this path,
/// `InvalidMoveIndex` if not moved
pub first_move: MoveIndex,
/// First node in linked list of children, `InvalidMovePathIndex` if leaf
pub first_child: MovePathIndex,
/// Next node in linked list of parent's children (siblings),
/// `InvalidMovePathIndex` if none.
pub next_sibling: MovePathIndex,
}
#[deriving(PartialEq)]
pub enum MoveKind {
Declared, // When declared, variables start out "moved".
MoveExpr, // Expression or binding that moves a variable
MovePat, // By-move binding
Captured // Closure creation that moves a value
}
pub struct Move {
/// Path being moved.
pub path: MovePathIndex,
/// id of node that is doing the move.
pub id: ast::NodeId,
/// Kind of move, for error messages.
pub kind: MoveKind,
/// Next node in linked list of moves from `path`, or `InvalidMoveIndex`
pub next_move: MoveIndex
}
pub struct Assignment {
/// Path being assigned.
pub path: MovePathIndex,
/// id where assignment occurs
pub id: ast::NodeId,
/// span of node where assignment occurs
pub span: Span,
}
#[deriving(Clone)]
pub struct MoveDataFlowOperator;
pub type MoveDataFlow<'a> = DataFlowContext<'a, MoveDataFlowOperator>;
#[deriving(Clone)]
pub struct AssignDataFlowOperator;
pub type AssignDataFlow<'a> = DataFlowContext<'a, AssignDataFlowOperator>;
impl MoveData {
pub fn new() -> MoveData {
MoveData {
paths: RefCell::new(Vec::new()),
path_map: RefCell::new(HashMap::new()),
moves: RefCell::new(Vec::new()),
path_assignments: RefCell::new(Vec::new()),
var_assignments: RefCell::new(Vec::new()),
assignee_ids: RefCell::new(HashSet::new()),
}
}
fn path_loan_path(&self, index: MovePathIndex) -> Rc<LoanPath> {
self.paths.borrow().get(index.get()).loan_path.clone()
}
fn path_parent(&self, index: MovePathIndex) -> MovePathIndex {
self.paths.borrow().get(index.get()).parent
}
fn path_first_move(&self, index: MovePathIndex) -> MoveIndex {
self.paths.borrow().get(index.get()).first_move
}
fn path_first_child(&self, index: MovePathIndex) -> MovePathIndex {
self.paths.borrow().get(index.get()).first_child
}
fn path_next_sibling(&self, index: MovePathIndex) -> MovePathIndex {
self.paths.borrow().get(index.get()).next_sibling
}
fn set_path_first_move(&self,
index: MovePathIndex,
first_move: MoveIndex) {
self.paths.borrow_mut().get_mut(index.get()).first_move = first_move
}
fn set_path_first_child(&self,
index: MovePathIndex,
first_child: MovePathIndex) {
self.paths.borrow_mut().get_mut(index.get()).first_child = first_child
}
fn move_next_move(&self, index: MoveIndex) -> MoveIndex {
//! Type safe indexing operator
self.moves.borrow().get(index.get()).next_move
}
fn is_var_path(&self, index: MovePathIndex) -> bool {
//! True if `index` refers to a variable
self.path_parent(index) == InvalidMovePathIndex
}
pub fn move_path(&self,
tcx: &ty::ctxt,
lp: Rc<LoanPath>) -> MovePathIndex {
/*!
* Returns the existing move path index for `lp`, if any,
* and otherwise adds a new index for `lp` and any of its
* base paths that do not yet have an index.
*/
match self.path_map.borrow().find(&lp) {
Some(&index) => {
return index;
}
None => {}
}
let index = match *lp {
LpVar(..) => {
let index = MovePathIndex(self.paths.borrow().len());
self.paths.borrow_mut().push(MovePath {
loan_path: lp.clone(),
parent: InvalidMovePathIndex,
first_move: InvalidMoveIndex,
first_child: InvalidMovePathIndex,
next_sibling: InvalidMovePathIndex,
});
index
}
LpExtend(ref base, _, _) => {
let parent_index = self.move_path(tcx, base.clone());
let index = MovePathIndex(self.paths.borrow().len());
let next_sibling = self.path_first_child(parent_index);
self.set_path_first_child(parent_index, index);
self.paths.borrow_mut().push(MovePath {
loan_path: lp.clone(),
parent: parent_index,
first_move: InvalidMoveIndex,
first_child: InvalidMovePathIndex,
next_sibling: next_sibling,
});
index
}
};
debug!("move_path(lp={}, index={:?})",
lp.repr(tcx),
index);
assert_eq!(index.get(), self.paths.borrow().len() - 1);
self.path_map.borrow_mut().insert(lp, index);
return index;
}
fn existing_move_path(&self, lp: &Rc<LoanPath>)
-> Option<MovePathIndex> {
self.path_map.borrow().find_copy(lp)
}
fn existing_base_paths(&self, lp: &Rc<LoanPath>)
-> Vec<MovePathIndex> {
let mut result = vec!();
self.add_existing_base_paths(lp, &mut result);
result
}
fn add_existing_base_paths(&self, lp: &Rc<LoanPath>,
result: &mut Vec<MovePathIndex>) {
/*!
* Adds any existing move path indices for `lp` and any base
* paths of `lp` to `result`, but does not add new move paths
*/
match self.path_map.borrow().find_copy(lp) {
Some(index) => {
self.each_base_path(index, |p| {
result.push(p);
true
});
}
None => {
match **lp {
LpVar(..) => { }
LpExtend(ref b, _, _) => {
self.add_existing_base_paths(b, result);
}
}
}
}
}
pub fn add_move(&self,
tcx: &ty::ctxt,
lp: Rc<LoanPath>,
id: ast::NodeId,
kind: MoveKind) {
/*!
* Adds a new move entry for a move of `lp` that occurs at
* location `id` with kind `kind`.
*/
debug!("add_move(lp={}, id={:?}, kind={:?})",
lp.repr(tcx),
id,
kind);
let path_index = self.move_path(tcx, lp);
let move_index = MoveIndex(self.moves.borrow().len());
let next_move = self.path_first_move(path_index);
self.set_path_first_move(path_index, move_index);
self.moves.borrow_mut().push(Move {
path: path_index,
id: id,
kind: kind,
next_move: next_move
});
}
pub fn add_assignment(&self,
tcx: &ty::ctxt,
lp: Rc<LoanPath>,
assign_id: ast::NodeId,
span: Span,
assignee_id: ast::NodeId,
mode: euv::MutateMode) {
/*!
* Adds a new record for an assignment to `lp` that occurs at
* location `id` with the given `span`.
*/
debug!("add_assignment(lp={}, assign_id={:?}, assignee_id={:?}",
lp.repr(tcx), assign_id, assignee_id);
let path_index = self.move_path(tcx, lp.clone());
match mode {
euv::Init | euv::JustWrite => {
self.assignee_ids.borrow_mut().insert(assignee_id);
}
euv::WriteAndRead => { }
}
let assignment = Assignment {
path: path_index,
id: assign_id,
span: span,
};
if self.is_var_path(path_index) {
debug!("add_assignment[var](lp={}, assignment={}, path_index={:?})",
lp.repr(tcx), self.var_assignments.borrow().len(), path_index);
self.var_assignments.borrow_mut().push(assignment);
} else {
debug!("add_assignment[path](lp={}, path_index={:?})",
lp.repr(tcx), path_index);
self.path_assignments.borrow_mut().push(assignment);
}
}
fn add_gen_kills(&self,
tcx: &ty::ctxt,
dfcx_moves: &mut MoveDataFlow,
dfcx_assign: &mut AssignDataFlow) {
/*!
* Adds the gen/kills for the various moves and
* assignments into the provided data flow contexts.
* Moves are generated by moves and killed by assignments and
* scoping. Assignments are generated by assignment to variables and
* killed by scoping. See `doc.rs` for more details.
*/
for (i, move) in self.moves.borrow().iter().enumerate() {
dfcx_moves.add_gen(move.id, i);
}
for (i, assignment) in self.var_assignments.borrow().iter().enumerate() {
dfcx_assign.add_gen(assignment.id, i);
self.kill_moves(assignment.path, assignment.id, dfcx_moves);
}
for assignment in self.path_assignments.borrow().iter() {
self.kill_moves(assignment.path, assignment.id, dfcx_moves);
}
// Kill all moves related to a variable `x` when it goes out
// of scope:
for path in self.paths.borrow().iter() {
match *path.loan_path {
LpVar(id) => {
let kill_id = tcx.region_maps.var_scope(id);
let path = *self.path_map.borrow().get(&path.loan_path);
self.kill_moves(path, kill_id, dfcx_moves);
}
LpExtend(..) => {}
}
}
// Kill all assignments when the variable goes out of scope:
for (assignment_index, assignment) in
self.var_assignments.borrow().iter().enumerate() {
match *self.path_loan_path(assignment.path) {
LpVar(id) => {
let kill_id = tcx.region_maps.var_scope(id);
dfcx_assign.add_kill(kill_id, assignment_index);
}
LpExtend(..) => {
tcx.sess.bug("var assignment for non var path");
}
}
}
}
fn each_base_path(&self, index: MovePathIndex, f: |MovePathIndex| -> bool)
-> bool {
let mut p = index;
while p != InvalidMovePathIndex {
if !f(p) {
return false;
}
p = self.path_parent(p);
}
return true;
}
fn each_extending_path(&self,
index: MovePathIndex,
f: |MovePathIndex| -> bool)
-> bool {
if !f(index) {
return false;
}
let mut p = self.path_first_child(index);
while p != InvalidMovePathIndex {
if !self.each_extending_path(p, |x| f(x)) {
return false;
}
p = self.path_next_sibling(p);
}
return true;
}
fn each_applicable_move(&self,
index0: MovePathIndex,
f: |MoveIndex| -> bool)
-> bool {
let mut ret = true;
self.each_extending_path(index0, |index| {
let mut p = self.path_first_move(index);
while p != InvalidMoveIndex {
if !f(p) {
ret = false;
break;
}
p = self.move_next_move(p);
}
ret
});
ret
}
fn kill_moves(&self,
path: MovePathIndex,
kill_id: ast::NodeId,
dfcx_moves: &mut MoveDataFlow) {
self.each_applicable_move(path, |move_index| {
dfcx_moves.add_kill(kill_id, move_index.get());
true
});
}
}
impl<'a> FlowedMoveData<'a> {
pub fn new(move_data: MoveData,
tcx: &'a ty::ctxt,
cfg: &'a cfg::CFG,
id_range: ast_util::IdRange,
decl: &ast::FnDecl,
body: &ast::Block)
-> FlowedMoveData<'a> {
let mut dfcx_moves =
DataFlowContext::new(tcx,
"flowed_move_data_moves",
Some(decl),
cfg,
MoveDataFlowOperator,
id_range,
move_data.moves.borrow().len());
let mut dfcx_assign =
DataFlowContext::new(tcx,
"flowed_move_data_assigns",
Some(decl),
cfg,
AssignDataFlowOperator,
id_range,
move_data.var_assignments.borrow().len());
move_data.add_gen_kills(tcx, &mut dfcx_moves, &mut dfcx_assign);
dfcx_moves.add_kills_from_flow_exits(cfg);
dfcx_assign.add_kills_from_flow_exits(cfg);
dfcx_moves.propagate(cfg, body);
dfcx_assign.propagate(cfg, body);
FlowedMoveData {
move_data: move_data,
dfcx_moves: dfcx_moves,
dfcx_assign: dfcx_assign,
}
}
pub fn each_path_moved_by(&self,
id: ast::NodeId,
f: |&Move, &LoanPath| -> bool)
-> bool {
/*!
* Iterates through each path moved by `id`
*/
self.dfcx_moves.each_gen_bit_frozen(id, |index| {
let move = self.move_data.moves.borrow();
let move = move.get(index);
let moved_path = move.path;
f(move, &*self.move_data.path_loan_path(moved_path))
})
}
pub fn kind_of_move_of_path(&self,
id: ast::NodeId,
loan_path: &Rc<LoanPath>)
-> Option<MoveKind> {
//! Returns the kind of a move of `loan_path` by `id`, if one exists.
let mut ret = None;
for loan_path_index in self.move_data.path_map.borrow().find(&*loan_path).iter() {
self.dfcx_moves.each_gen_bit_frozen(id, |move_index| {
let move = self.move_data.moves.borrow();
let move = move.get(move_index);
if move.path == **loan_path_index {
ret = Some(move.kind);
false
} else {
true
}
});
}
ret
}
pub fn each_move_of(&self,
id: ast::NodeId,
loan_path: &Rc<LoanPath>,
f: |&Move, &LoanPath| -> bool)
-> bool {
/*!
* Iterates through each move of `loan_path` (or some base path
* of `loan_path`) that *may* have occurred on entry to `id` without
* an intervening assignment. In other words, any moves that
* would invalidate a reference to `loan_path` at location `id`.
*/
// Bad scenarios:
//
// 1. Move of `a.b.c`, use of `a.b.c`
// 2. Move of `a.b.c`, use of `a.b.c.d`
// 3. Move of `a.b.c`, use of `a` or `a.b`
//
// OK scenario:
//
// 4. move of `a.b.c`, use of `a.b.d`
let base_indices = self.move_data.existing_base_paths(loan_path);
if base_indices.is_empty() {
return true;
}
let opt_loan_path_index = self.move_data.existing_move_path(loan_path);
let mut ret = true;
self.dfcx_moves.each_bit_on_entry_frozen(id, |index| {
let move = self.move_data.moves.borrow();
let move = move.get(index);
let moved_path = move.path;
if base_indices.iter().any(|x| x == &moved_path) {
// Scenario 1 or 2: `loan_path` or some base path of
// `loan_path` was moved.
if !f(move, &*self.move_data.path_loan_path(moved_path)) {
ret = false;
}
} else {
for &loan_path_index in opt_loan_path_index.iter() {
let cont = self.move_data.each_base_path(moved_path, |p| {
if p == loan_path_index {
// Scenario 3: some extension of `loan_path`
// was moved
f(move, &*self.move_data.path_loan_path(moved_path))
} else {
true
}
});
if !cont { ret = false; break }
}
}
ret
})
}
pub fn is_assignee(&self,
id: ast::NodeId)
-> bool {
//! True if `id` is the id of the LHS of an assignment
self.move_data.assignee_ids.borrow().iter().any(|x| x == &id)
}
pub fn each_assignment_of(&self,
id: ast::NodeId,
loan_path: &Rc<LoanPath>,
f: |&Assignment| -> bool)
-> bool {
/*!
* Iterates through every assignment to `loan_path` that
* may have occurred on entry to `id`. `loan_path` must be
* a single variable.
*/
let loan_path_index = {
match self.move_data.existing_move_path(loan_path) {
Some(i) => i,
None => {
// if there were any assignments, it'd have an index
return true;
}
}
};
self.dfcx_assign.each_bit_on_entry_frozen(id, |index| {
let assignment = self.move_data.var_assignments.borrow();
let assignment = assignment.get(index);
if assignment.path == loan_path_index && !f(assignment) {
false
} else {
true
}
})
}
}
impl BitwiseOperator for MoveDataFlowOperator {
#[inline]
fn join(&self, succ: uint, pred: uint) -> uint {
succ | pred // moves from both preds are in scope
}
}
impl DataFlowOperator for MoveDataFlowOperator {
#[inline]
fn initial_value(&self) -> bool {
false // no loans in scope by default
}
}
impl BitwiseOperator for AssignDataFlowOperator {
#[inline]
fn join(&self, succ: uint, pred: uint) -> uint {
succ | pred // moves from both preds are in scope
}
}
impl DataFlowOperator for AssignDataFlowOperator {
#[inline]
fn initial_value(&self) -> bool {
false // no assignments in scope by default
}
}