/
mod.rs
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/
mod.rs
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// Copyright 2012-2016 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.
use borrowck::BorrowckCtxt;
use syntax::ast::{self, MetaItem};
use syntax_pos::DUMMY_SP;
use rustc::mir::{self, BasicBlock, BasicBlockData, Mir, Statement, Terminator, Location};
use rustc::session::Session;
use rustc::ty::{self, TyCtxt};
use rustc_mir::util::elaborate_drops::DropFlagState;
use rustc_data_structures::indexed_set::{IdxSet, IdxSetBuf};
mod abs_domain;
pub mod elaborate_drops;
mod dataflow;
mod gather_moves;
// mod graphviz;
use self::dataflow::{BitDenotation};
use self::dataflow::{DataflowOperator};
use self::dataflow::{Dataflow, DataflowAnalysis, DataflowResults};
use self::dataflow::{MaybeInitializedLvals, MaybeUninitializedLvals};
use self::dataflow::{DefinitelyInitializedLvals};
use self::gather_moves::{HasMoveData, MoveData, MovePathIndex, LookupResult};
use std::fmt;
fn has_rustc_mir_with(attrs: &[ast::Attribute], name: &str) -> Option<MetaItem> {
for attr in attrs {
if attr.check_name("rustc_mir") {
let items = attr.meta_item_list();
for item in items.iter().flat_map(|l| l.iter()) {
match item.meta_item() {
Some(mi) if mi.check_name(name) => return Some(mi.clone()),
_ => continue
}
}
}
}
return None;
}
pub struct MoveDataParamEnv<'tcx> {
move_data: MoveData<'tcx>,
param_env: ty::ParameterEnvironment<'tcx>,
}
pub fn borrowck_mir(bcx: &mut BorrowckCtxt,
id: ast::NodeId,
attributes: &[ast::Attribute]) {
let tcx = bcx.tcx;
let def_id = tcx.hir.local_def_id(id);
debug!("borrowck_mir({}) UNIMPLEMENTED", tcx.item_path_str(def_id));
let mir = &tcx.item_mir(def_id);
let param_env = ty::ParameterEnvironment::for_item(tcx, id);
let move_data = MoveData::gather_moves(mir, tcx, ¶m_env);
let mdpe = MoveDataParamEnv { move_data: move_data, param_env: param_env };
let dead_unwinds = IdxSetBuf::new_empty(mir.basic_blocks().len());
let flow_inits =
do_dataflow(tcx, mir, id, attributes, &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
let flow_uninits =
do_dataflow(tcx, mir, id, attributes, &dead_unwinds,
MaybeUninitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
let flow_def_inits =
do_dataflow(tcx, mir, id, attributes, &dead_unwinds,
DefinitelyInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
if has_rustc_mir_with(attributes, "rustc_peek_maybe_init").is_some() {
dataflow::sanity_check_via_rustc_peek(bcx.tcx, mir, id, attributes, &flow_inits);
}
if has_rustc_mir_with(attributes, "rustc_peek_maybe_uninit").is_some() {
dataflow::sanity_check_via_rustc_peek(bcx.tcx, mir, id, attributes, &flow_uninits);
}
if has_rustc_mir_with(attributes, "rustc_peek_definite_init").is_some() {
dataflow::sanity_check_via_rustc_peek(bcx.tcx, mir, id, attributes, &flow_def_inits);
}
if has_rustc_mir_with(attributes, "stop_after_dataflow").is_some() {
bcx.tcx.sess.fatal("stop_after_dataflow ended compilation");
}
let mut mbcx = MirBorrowckCtxt {
bcx: bcx,
mir: mir,
node_id: id,
move_data: &mdpe.move_data,
flow_inits: flow_inits,
flow_uninits: flow_uninits,
};
for bb in mir.basic_blocks().indices() {
mbcx.process_basic_block(bb);
}
debug!("borrowck_mir done");
}
fn do_dataflow<'a, 'tcx, BD, P>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
node_id: ast::NodeId,
attributes: &[ast::Attribute],
dead_unwinds: &IdxSet<BasicBlock>,
bd: BD,
p: P)
-> DataflowResults<BD>
where BD: BitDenotation<Idx=MovePathIndex> + DataflowOperator,
P: Fn(&BD, BD::Idx) -> &fmt::Debug
{
let name_found = |sess: &Session, attrs: &[ast::Attribute], name| -> Option<String> {
if let Some(item) = has_rustc_mir_with(attrs, name) {
if let Some(s) = item.value_str() {
return Some(s.to_string())
} else {
sess.span_err(
item.span,
&format!("{} attribute requires a path", item.name()));
return None;
}
}
return None;
};
let print_preflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_preflow");
let print_postflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_postflow");
let mut mbcx = MirBorrowckCtxtPreDataflow {
node_id: node_id,
print_preflow_to: print_preflow_to,
print_postflow_to: print_postflow_to,
flow_state: DataflowAnalysis::new(tcx, mir, dead_unwinds, bd),
};
mbcx.dataflow(p);
mbcx.flow_state.results()
}
pub struct MirBorrowckCtxtPreDataflow<'a, 'tcx: 'a, BD> where BD: BitDenotation
{
node_id: ast::NodeId,
flow_state: DataflowAnalysis<'a, 'tcx, BD>,
print_preflow_to: Option<String>,
print_postflow_to: Option<String>,
}
#[allow(dead_code)]
pub struct MirBorrowckCtxt<'b, 'a: 'b, 'tcx: 'a> {
bcx: &'b mut BorrowckCtxt<'a, 'tcx>,
mir: &'b Mir<'tcx>,
node_id: ast::NodeId,
move_data: &'b MoveData<'tcx>,
flow_inits: DataflowResults<MaybeInitializedLvals<'b, 'tcx>>,
flow_uninits: DataflowResults<MaybeUninitializedLvals<'b, 'tcx>>
}
impl<'b, 'a: 'b, 'tcx: 'a> MirBorrowckCtxt<'b, 'a, 'tcx> {
fn process_basic_block(&mut self, bb: BasicBlock) {
let BasicBlockData { ref statements, ref terminator, is_cleanup: _ } =
self.mir[bb];
for stmt in statements {
self.process_statement(bb, stmt);
}
self.process_terminator(bb, terminator);
}
fn process_statement(&mut self, bb: BasicBlock, stmt: &Statement<'tcx>) {
debug!("MirBorrowckCtxt::process_statement({:?}, {:?}", bb, stmt);
}
fn process_terminator(&mut self, bb: BasicBlock, term: &Option<Terminator<'tcx>>) {
debug!("MirBorrowckCtxt::process_terminator({:?}, {:?})", bb, term);
}
}
fn move_path_children_matching<'tcx, F>(move_data: &MoveData<'tcx>,
path: MovePathIndex,
mut cond: F)
-> Option<MovePathIndex>
where F: FnMut(&mir::LvalueProjection<'tcx>) -> bool
{
let mut next_child = move_data.move_paths[path].first_child;
while let Some(child_index) = next_child {
match move_data.move_paths[child_index].lvalue {
mir::Lvalue::Projection(ref proj) => {
if cond(proj) {
return Some(child_index)
}
}
_ => {}
}
next_child = move_data.move_paths[child_index].next_sibling;
}
None
}
/// When enumerating the child fragments of a path, don't recurse into
/// paths (1.) past arrays, slices, and pointers, nor (2.) into a type
/// that implements `Drop`.
///
/// Lvalues behind references or arrays are not tracked by elaboration
/// and are always assumed to be initialized when accessible. As
/// references and indexes can be reseated, trying to track them can
/// only lead to trouble.
///
/// Lvalues behind ADT's with a Drop impl are not tracked by
/// elaboration since they can never have a drop-flag state that
/// differs from that of the parent with the Drop impl.
///
/// In both cases, the contents can only be accessed if and only if
/// their parents are initialized. This implies for example that there
/// is no need to maintain separate drop flags to track such state.
///
/// FIXME: we have to do something for moving slice patterns.
fn lvalue_contents_drop_state_cannot_differ<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
lv: &mir::Lvalue<'tcx>) -> bool {
let ty = lv.ty(mir, tcx).to_ty(tcx);
match ty.sty {
ty::TyArray(..) | ty::TySlice(..) | ty::TyRef(..) | ty::TyRawPtr(..) => {
debug!("lvalue_contents_drop_state_cannot_differ lv: {:?} ty: {:?} refd => true",
lv, ty);
true
}
ty::TyAdt(def, _) if (def.has_dtor(tcx) && !def.is_box()) || def.is_union() => {
debug!("lvalue_contents_drop_state_cannot_differ lv: {:?} ty: {:?} Drop => true",
lv, ty);
true
}
_ => {
false
}
}
}
fn on_lookup_result_bits<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
move_data: &MoveData<'tcx>,
lookup_result: LookupResult,
each_child: F)
where F: FnMut(MovePathIndex)
{
match lookup_result {
LookupResult::Parent(..) => {
// access to untracked value - do not touch children
}
LookupResult::Exact(e) => {
on_all_children_bits(tcx, mir, move_data, e, each_child)
}
}
}
fn on_all_children_bits<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
move_data: &MoveData<'tcx>,
move_path_index: MovePathIndex,
mut each_child: F)
where F: FnMut(MovePathIndex)
{
fn is_terminal_path<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
move_data: &MoveData<'tcx>,
path: MovePathIndex) -> bool
{
lvalue_contents_drop_state_cannot_differ(
tcx, mir, &move_data.move_paths[path].lvalue)
}
fn on_all_children_bits<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
move_data: &MoveData<'tcx>,
move_path_index: MovePathIndex,
each_child: &mut F)
where F: FnMut(MovePathIndex)
{
each_child(move_path_index);
if is_terminal_path(tcx, mir, move_data, move_path_index) {
return
}
let mut next_child_index = move_data.move_paths[move_path_index].first_child;
while let Some(child_index) = next_child_index {
on_all_children_bits(tcx, mir, move_data, child_index, each_child);
next_child_index = move_data.move_paths[child_index].next_sibling;
}
}
on_all_children_bits(tcx, mir, move_data, move_path_index, &mut each_child);
}
fn on_all_drop_children_bits<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
ctxt: &MoveDataParamEnv<'tcx>,
path: MovePathIndex,
mut each_child: F)
where F: FnMut(MovePathIndex)
{
on_all_children_bits(tcx, mir, &ctxt.move_data, path, |child| {
let lvalue = &ctxt.move_data.move_paths[path].lvalue;
let ty = lvalue.ty(mir, tcx).to_ty(tcx);
debug!("on_all_drop_children_bits({:?}, {:?} : {:?})", path, lvalue, ty);
if ty.needs_drop(tcx, &ctxt.param_env) {
each_child(child);
} else {
debug!("on_all_drop_children_bits - skipping")
}
})
}
fn drop_flag_effects_for_function_entry<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
ctxt: &MoveDataParamEnv<'tcx>,
mut callback: F)
where F: FnMut(MovePathIndex, DropFlagState)
{
let move_data = &ctxt.move_data;
for arg in mir.args_iter() {
let lvalue = mir::Lvalue::Local(arg);
let lookup_result = move_data.rev_lookup.find(&lvalue);
on_lookup_result_bits(tcx, mir, move_data,
lookup_result,
|moi| callback(moi, DropFlagState::Present));
}
}
fn drop_flag_effects_for_location<'a, 'tcx, F>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &Mir<'tcx>,
ctxt: &MoveDataParamEnv<'tcx>,
loc: Location,
mut callback: F)
where F: FnMut(MovePathIndex, DropFlagState)
{
let move_data = &ctxt.move_data;
let param_env = &ctxt.param_env;
debug!("drop_flag_effects_for_location({:?})", loc);
// first, move out of the RHS
for mi in &move_data.loc_map[loc] {
let path = mi.move_path_index(move_data);
debug!("moving out of path {:?}", move_data.move_paths[path]);
// don't move out of non-Copy things
let lvalue = &move_data.move_paths[path].lvalue;
let ty = lvalue.ty(mir, tcx).to_ty(tcx);
if !ty.moves_by_default(tcx, param_env, DUMMY_SP) {
continue;
}
on_all_children_bits(tcx, mir, move_data,
path,
|moi| callback(moi, DropFlagState::Absent))
}
let block = &mir[loc.block];
match block.statements.get(loc.statement_index) {
Some(stmt) => match stmt.kind {
mir::StatementKind::SetDiscriminant{ .. } => {
span_bug!(stmt.source_info.span, "SetDiscrimant should not exist during borrowck");
}
mir::StatementKind::Assign(ref lvalue, _) => {
debug!("drop_flag_effects: assignment {:?}", stmt);
on_lookup_result_bits(tcx, mir, move_data,
move_data.rev_lookup.find(lvalue),
|moi| callback(moi, DropFlagState::Present))
}
mir::StatementKind::StorageLive(_) |
mir::StatementKind::StorageDead(_) |
mir::StatementKind::InlineAsm { .. } |
mir::StatementKind::Nop => {}
},
None => {
debug!("drop_flag_effects: replace {:?}", block.terminator());
match block.terminator().kind {
mir::TerminatorKind::DropAndReplace { ref location, .. } => {
on_lookup_result_bits(tcx, mir, move_data,
move_data.rev_lookup.find(location),
|moi| callback(moi, DropFlagState::Present))
}
_ => {
// other terminators do not contain move-ins
}
}
}
}
}