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Auto merge of #106976 - tmiasko:borrowck-lazy-dominators, r=cjgillot

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Lazy dominator tree construction in borrowck

Motivated by the observation that sometimes constructed dominator tree was never queried.
This commit is contained in:
bors 2023-01-21 11:02:29 +00:00
commit 21f6839352
3 changed files with 12 additions and 12 deletions
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4
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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@ -2193,7 +2193,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let mut back_edge_stack = Vec::new(); let mut back_edge_stack = Vec::new();
predecessor_locations(self.body, location).for_each(|predecessor| { predecessor_locations(self.body, location).for_each(|predecessor| {
if location.dominates(predecessor, &self.dominators) { if location.dominates(predecessor, self.dominators()) {
back_edge_stack.push(predecessor) back_edge_stack.push(predecessor)
} else { } else {
stack.push(predecessor); stack.push(predecessor);
@ -2305,7 +2305,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let mut has_predecessor = false; let mut has_predecessor = false;
predecessor_locations(self.body, location).for_each(|predecessor| { predecessor_locations(self.body, location).for_each(|predecessor| {
if location.dominates(predecessor, &self.dominators) { if location.dominates(predecessor, self.dominators()) {
back_edge_stack.push(predecessor) back_edge_stack.push(predecessor)
} else { } else {
stack.push(predecessor); stack.push(predecessor);

16
compiler/rustc_borrowck/src/lib.rs
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@ -5,6 +5,7 @@
#![feature(let_chains)] #![feature(let_chains)]
#![feature(min_specialization)] #![feature(min_specialization)]
#![feature(never_type)] #![feature(never_type)]
#![feature(once_cell)]
#![feature(rustc_attrs)] #![feature(rustc_attrs)]
#![feature(stmt_expr_attributes)] #![feature(stmt_expr_attributes)]
#![feature(trusted_step)] #![feature(trusted_step)]
@ -39,6 +40,7 @@ use rustc_span::{Span, Symbol};
use either::Either; use either::Either;
use smallvec::SmallVec; use smallvec::SmallVec;
use std::cell::OnceCell;
use std::cell::RefCell; use std::cell::RefCell;
use std::collections::BTreeMap; use std::collections::BTreeMap;
use std::rc::Rc; use std::rc::Rc;
@ -333,7 +335,7 @@ fn do_mir_borrowck<'tcx>(
used_mut: Default::default(), used_mut: Default::default(),
used_mut_upvars: SmallVec::new(), used_mut_upvars: SmallVec::new(),
borrow_set: Rc::clone(&borrow_set), borrow_set: Rc::clone(&borrow_set),
dominators: Dominators::dummy(), // not used dominators: Default::default(),
upvars: Vec::new(), upvars: Vec::new(),
local_names: IndexVec::from_elem(None, &promoted_body.local_decls), local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
region_names: RefCell::default(), region_names: RefCell::default(),
@ -346,8 +348,6 @@ fn do_mir_borrowck<'tcx>(
}; };
} }
let dominators = body.basic_blocks.dominators();
let mut mbcx = MirBorrowckCtxt { let mut mbcx = MirBorrowckCtxt {
infcx, infcx,
param_env, param_env,
@ -364,7 +364,7 @@ fn do_mir_borrowck<'tcx>(
used_mut: Default::default(), used_mut: Default::default(),
used_mut_upvars: SmallVec::new(), used_mut_upvars: SmallVec::new(),
borrow_set: Rc::clone(&borrow_set), borrow_set: Rc::clone(&borrow_set),
dominators, dominators: Default::default(),
upvars, upvars,
local_names, local_names,
region_names: RefCell::default(), region_names: RefCell::default(),
@ -534,7 +534,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
borrow_set: Rc<BorrowSet<'tcx>>, borrow_set: Rc<BorrowSet<'tcx>>,
/// Dominators for MIR /// Dominators for MIR
dominators: Dominators<BasicBlock>, dominators: OnceCell<Dominators<BasicBlock>>,
/// Information about upvars not necessarily preserved in types or MIR /// Information about upvars not necessarily preserved in types or MIR
upvars: Vec<Upvar<'tcx>>, upvars: Vec<Upvar<'tcx>>,
@ -1051,7 +1051,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
(Read(kind), BorrowKind::Unique | BorrowKind::Mut { .. }) => { (Read(kind), BorrowKind::Unique | BorrowKind::Mut { .. }) => {
// Reading from mere reservations of mutable-borrows is OK. // Reading from mere reservations of mutable-borrows is OK.
if !is_active(&this.dominators, borrow, location) { if !is_active(this.dominators(), borrow, location) {
assert!(allow_two_phase_borrow(borrow.kind)); assert!(allow_two_phase_borrow(borrow.kind));
return Control::Continue; return Control::Continue;
} }
@ -2219,6 +2219,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<Field> { fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<Field> {
path_utils::is_upvar_field_projection(self.infcx.tcx, &self.upvars, place_ref, self.body()) path_utils::is_upvar_field_projection(self.infcx.tcx, &self.upvars, place_ref, self.body())
} }
fn dominators(&self) -> &Dominators<BasicBlock> {
self.dominators.get_or_init(|| self.body.basic_blocks.dominators())
}
} }
mod error { mod error {

4
compiler/rustc_data_structures/src/graph/dominators/mod.rs
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@ -271,10 +271,6 @@ pub struct Dominators<N: Idx> {
} }
impl<Node: Idx> Dominators<Node> { impl<Node: Idx> Dominators<Node> {
pub fn dummy() -> Self {
Self { post_order_rank: IndexVec::new(), immediate_dominators: IndexVec::new() }
}
pub fn is_reachable(&self, node: Node) -> bool { pub fn is_reachable(&self, node: Node) -> bool {
self.immediate_dominators[node].is_some() self.immediate_dominators[node].is_some()
} }