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|
pub use super::*;
use rustc::mir::*;
use rustc::mir::visit::{
PlaceContext, Visitor, NonMutatingUseContext,
};
use std::cell::RefCell;
use crate::dataflow::BitDenotation;
use crate::dataflow::HaveBeenBorrowedLocals;
use crate::dataflow::{DataflowResults, DataflowResultsCursor, DataflowResultsRefCursor};
#[derive(Copy, Clone)]
pub struct MaybeStorageLive<'a, 'tcx> {
body: &'a Body<'tcx>,
}
impl<'a, 'tcx> MaybeStorageLive<'a, 'tcx> {
pub fn new(body: &'a Body<'tcx>)
-> Self {
MaybeStorageLive { body }
}
pub fn body(&self) -> &Body<'tcx> {
self.body
}
}
impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
type Idx = Local;
fn name() -> &'static str { "maybe_storage_live" }
fn bits_per_block(&self) -> usize {
self.body.local_decls.len()
}
fn start_block_effect(&self, _on_entry: &mut BitSet<Local>) {
// Nothing is live on function entry (generators only have a self
// argument, and we don't care about that)
assert_eq!(1, self.body.arg_count);
}
fn statement_effect(&self,
trans: &mut GenKillSet<Local>,
loc: Location) {
let stmt = &self.body[loc.block].statements[loc.statement_index];
match stmt.kind {
StatementKind::StorageLive(l) => trans.gen(l),
StatementKind::StorageDead(l) => trans.kill(l),
_ => (),
}
}
fn terminator_effect(&self,
_trans: &mut GenKillSet<Local>,
_loc: Location) {
// Terminators have no effect
}
fn propagate_call_return(
&self,
_in_out: &mut BitSet<Local>,
_call_bb: mir::BasicBlock,
_dest_bb: mir::BasicBlock,
_dest_place: &mir::Place<'tcx>,
) {
// Nothing to do when a call returns successfully
}
}
impl<'a, 'tcx> BottomValue for MaybeStorageLive<'a, 'tcx> {
/// bottom = dead
const BOTTOM_VALUE: bool = false;
}
/// Dataflow analysis that determines whether each local requires storage at a
/// given location; i.e. whether its storage can go away without being observed.
pub struct RequiresStorage<'mir, 'tcx> {
body: &'mir Body<'tcx>,
borrowed_locals:
RefCell<DataflowResultsRefCursor<'mir, 'tcx, HaveBeenBorrowedLocals<'mir, 'tcx>>>,
}
impl<'mir, 'tcx: 'mir> RequiresStorage<'mir, 'tcx> {
pub fn new(
body: &'mir Body<'tcx>,
borrowed_locals: &'mir DataflowResults<'tcx, HaveBeenBorrowedLocals<'mir, 'tcx>>,
) -> Self {
RequiresStorage {
body,
borrowed_locals: RefCell::new(DataflowResultsCursor::new(borrowed_locals, body)),
}
}
pub fn body(&self) -> &Body<'tcx> {
self.body
}
}
impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
type Idx = Local;
fn name() -> &'static str { "requires_storage" }
fn bits_per_block(&self) -> usize {
self.body.local_decls.len()
}
fn start_block_effect(&self, _sets: &mut BitSet<Local>) {
// Nothing is live on function entry (generators only have a self
// argument, and we don't care about that)
assert_eq!(1, self.body.arg_count);
}
fn before_statement_effect(&self, sets: &mut GenKillSet<Self::Idx>, loc: Location) {
// If we borrow or assign to a place then it needs storage for that
// statement.
self.check_for_borrow(sets, loc);
let stmt = &self.body[loc.block].statements[loc.statement_index];
match stmt.kind {
StatementKind::StorageDead(l) => sets.kill(l),
StatementKind::Assign(box(ref place, _))
| StatementKind::SetDiscriminant { box ref place, .. } => {
if let PlaceBase::Local(local) = place.base {
sets.gen(local);
}
}
StatementKind::InlineAsm(box InlineAsm { ref outputs, .. }) => {
for p in &**outputs {
if let PlaceBase::Local(local) = p.base {
sets.gen(local);
}
}
}
_ => (),
}
}
fn statement_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
// If we move from a place then only stops needing storage *after*
// that statement.
self.check_for_move(sets, loc);
}
fn before_terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
self.check_for_borrow(sets, loc);
if let TerminatorKind::Call {
destination: Some((Place { base: PlaceBase::Local(local), .. }, _)),
..
} = self.body[loc.block].terminator().kind {
sets.gen(local);
}
}
fn terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
// For call terminators the destination requires storage for the call
// and after the call returns successfully, but not after a panic.
// Since `propagate_call_unwind` doesn't exist, we have to kill the
// destination here, and then gen it again in `propagate_call_return`.
if let TerminatorKind::Call {
destination: Some((ref place, _)),
..
} = self.body[loc.block].terminator().kind {
if let Some(local) = place.as_local() {
sets.kill(local);
}
}
self.check_for_move(sets, loc);
}
fn propagate_call_return(
&self,
in_out: &mut BitSet<Local>,
_call_bb: mir::BasicBlock,
_dest_bb: mir::BasicBlock,
dest_place: &mir::Place<'tcx>,
) {
if let PlaceBase::Local(local) = dest_place.base {
in_out.insert(local);
}
}
}
impl<'mir, 'tcx> RequiresStorage<'mir, 'tcx> {
/// Kill locals that are fully moved and have not been borrowed.
fn check_for_move(&self, sets: &mut GenKillSet<Local>, loc: Location) {
let mut visitor = MoveVisitor {
sets,
borrowed_locals: &self.borrowed_locals,
};
visitor.visit_location(self.body, loc);
}
/// Gen locals that are newly borrowed. This includes borrowing any part of
/// a local (we rely on this behavior of `HaveBeenBorrowedLocals`).
fn check_for_borrow(&self, sets: &mut GenKillSet<Local>, loc: Location) {
let mut borrowed_locals = self.borrowed_locals.borrow_mut();
borrowed_locals.seek(loc);
borrowed_locals.each_gen_bit(|l| sets.gen(l));
}
}
impl<'mir, 'tcx> BottomValue for RequiresStorage<'mir, 'tcx> {
/// bottom = dead
const BOTTOM_VALUE: bool = false;
}
struct MoveVisitor<'a, 'mir, 'tcx> {
borrowed_locals:
&'a RefCell<DataflowResultsRefCursor<'mir, 'tcx, HaveBeenBorrowedLocals<'mir, 'tcx>>>,
sets: &'a mut GenKillSet<Local>,
}
impl<'a, 'mir: 'a, 'tcx> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx> {
fn visit_local(&mut self, local: &Local, context: PlaceContext, loc: Location) {
if PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) == context {
let mut borrowed_locals = self.borrowed_locals.borrow_mut();
borrowed_locals.seek(loc);
if !borrowed_locals.contains(*local) {
self.sets.kill(*local);
}
}
}
}
|
