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// Copyright 2017 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.
pub use super::*;
use rustc::mir::*;
use rustc::mir::visit::Visitor;
use dataflow::BitDenotation;
/// This calculates if any part of a MIR local could have previously been borrowed.
/// This means that once a local has been borrowed, its bit will always be set
/// from that point and onwards, even if the borrow ends. You could also think of this
/// as computing the lifetimes of infinite borrows.
/// This is used to compute which locals are live during a yield expression for
/// immovable generators.
#[derive(Copy, Clone)]
pub struct HaveBeenBorrowedLocals<'a, 'tcx: 'a> {
mir: &'a Mir<'tcx>,
}
impl<'a, 'tcx: 'a> HaveBeenBorrowedLocals<'a, 'tcx> {
pub fn new(mir: &'a Mir<'tcx>)
-> Self {
HaveBeenBorrowedLocals { mir: mir }
}
pub fn mir(&self) -> &Mir<'tcx> {
self.mir
}
}
impl<'a, 'tcx> BitDenotation for HaveBeenBorrowedLocals<'a, 'tcx> {
type Idx = Local;
fn name() -> &'static str { "has_been_borrowed_locals" }
fn bits_per_block(&self) -> usize {
self.mir.local_decls.len()
}
fn start_block_effect(&self, _sets: &mut IdxSet<Local>) {
// Nothing is borrowed on function entry
}
fn statement_effect(&self,
sets: &mut BlockSets<Local>,
loc: Location) {
BorrowedLocalsVisitor {
sets,
}.visit_statement(loc.block, &self.mir[loc.block].statements[loc.statement_index], loc);
}
fn terminator_effect(&self,
sets: &mut BlockSets<Local>,
loc: Location) {
BorrowedLocalsVisitor {
sets,
}.visit_terminator(loc.block, self.mir[loc.block].terminator(), loc);
}
fn propagate_call_return(&self,
_in_out: &mut IdxSet<Local>,
_call_bb: mir::BasicBlock,
_dest_bb: mir::BasicBlock,
_dest_place: &mir::Place) {
// Nothing to do when a call returns successfully
}
}
impl<'a, 'tcx> BitwiseOperator for HaveBeenBorrowedLocals<'a, 'tcx> {
#[inline]
fn join(&self, pred1: usize, pred2: usize) -> usize {
pred1 | pred2 // "maybe" means we union effects of both preds
}
}
impl<'a, 'tcx> InitialFlow for HaveBeenBorrowedLocals<'a, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = unborrowed
}
}
struct BorrowedLocalsVisitor<'b, 'c: 'b> {
sets: &'b mut BlockSets<'c, Local>,
}
fn find_local<'tcx>(place: &Place<'tcx>) -> Option<Local> {
match *place {
Place::Local(l) => Some(l),
Place::Static(..) => None,
Place::Projection(ref proj) => {
match proj.elem {
ProjectionElem::Deref => None,
_ => find_local(&proj.base)
}
}
}
}
impl<'tcx, 'b, 'c> Visitor<'tcx> for BorrowedLocalsVisitor<'b, 'c> {
fn visit_rvalue(&mut self,
rvalue: &Rvalue<'tcx>,
location: Location) {
if let Rvalue::Ref(_, _, ref place) = *rvalue {
if let Some(local) = find_local(place) {
self.sets.gen(&local);
}
}
self.super_rvalue(rvalue, location)
}
}
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