bjoernager/rust
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Auto merge of #116300 - cjgillot:split-move, r=petrochenkov

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Separate move path tracking between borrowck and drop elaboration.

The primary goal of this PR is to skip creating a `MovePathIndex` for path that do not need dropping in drop elaboration.

The 2 first commits are cleanups.

The next 2 commits displace `move` errors from move-path builder to borrowck. Move-path builder keeps the same logic, but does not carry error information any more.

The remaining commits allow to filter `MovePathIndex` creation according to types. This is used in drop elaboration, to avoid computing dataflow for paths that do not need dropping.
This commit is contained in:
bors 2023-10-24 00:25:32 +00:00
commit cd674d6179
19 changed files with 581 additions and 559 deletions
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7
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View file

@ -2633,9 +2633,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
/* Check if the mpi is initialized as an argument */
let mut is_argument = false;
for arg in self.body.args_iter() {
let path = self.move_data.rev_lookup.find_local(arg);
if mpis.contains(&path) {
is_argument = true;
if let Some(path) = self.move_data.rev_lookup.find_local(arg) {
if mpis.contains(&path) {
is_argument = true;
}
}
}

1
compiler/rustc_borrowck/src/diagnostics/mod.rs
View file

@ -46,6 +46,7 @@ mod mutability_errors;
mod region_errors;
pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
pub(crate) use move_errors::{IllegalMoveOriginKind, MoveError};
pub(crate) use mutability_errors::AccessKind;
pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};

158
compiler/rustc_borrowck/src/diagnostics/move_errors.rs
View file

@ -1,9 +1,7 @@
use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
use rustc_middle::mir::*;
use rustc_middle::ty;
use rustc_mir_dataflow::move_paths::{
IllegalMoveOrigin, IllegalMoveOriginKind, LookupResult, MoveError, MovePathIndex,
};
use rustc_middle::ty::{self, Ty};
use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};
use rustc_span::{BytePos, Span};
use crate::diagnostics::CapturedMessageOpt;
@ -11,6 +9,42 @@ use crate::diagnostics::{DescribePlaceOpt, UseSpans};
use crate::prefixes::PrefixSet;
use crate::MirBorrowckCtxt;
#[derive(Debug)]
pub enum IllegalMoveOriginKind<'tcx> {
/// Illegal move due to attempt to move from behind a reference.
BorrowedContent {
/// The place the reference refers to: if erroneous code was trying to
/// move from `(*x).f` this will be `*x`.
target_place: Place<'tcx>,
},
/// Illegal move due to attempt to move from field of an ADT that
/// implements `Drop`. Rust maintains invariant that all `Drop`
/// ADT's remain fully-initialized so that user-defined destructor
/// can safely read from all of the ADT's fields.
InteriorOfTypeWithDestructor { container_ty: Ty<'tcx> },
/// Illegal move due to attempt to move out of a slice or array.
InteriorOfSliceOrArray { ty: Ty<'tcx>, is_index: bool },
}
#[derive(Debug)]
pub(crate) struct MoveError<'tcx> {
place: Place<'tcx>,
location: Location,
kind: IllegalMoveOriginKind<'tcx>,
}
impl<'tcx> MoveError<'tcx> {
pub(crate) fn new(
place: Place<'tcx>,
location: Location,
kind: IllegalMoveOriginKind<'tcx>,
) -> Self {
MoveError { place, location, kind }
}
}
// Often when desugaring a pattern match we may have many individual moves in
// MIR that are all part of one operation from the user's point-of-view. For
// example:
@ -53,20 +87,18 @@ enum GroupedMoveError<'tcx> {
}
impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
pub(crate) fn report_move_errors(&mut self, move_errors: Vec<(Place<'tcx>, MoveError<'tcx>)>) {
let grouped_errors = self.group_move_errors(move_errors);
pub(crate) fn report_move_errors(&mut self) {
let grouped_errors = self.group_move_errors();
for error in grouped_errors {
self.report(error);
}
}
fn group_move_errors(
&self,
errors: Vec<(Place<'tcx>, MoveError<'tcx>)>,
) -> Vec<GroupedMoveError<'tcx>> {
fn group_move_errors(&mut self) -> Vec<GroupedMoveError<'tcx>> {
let mut grouped_errors = Vec::new();
for (original_path, error) in errors {
self.append_to_grouped_errors(&mut grouped_errors, original_path, error);
let errors = std::mem::take(&mut self.move_errors);
for error in errors {
self.append_to_grouped_errors(&mut grouped_errors, error);
}
grouped_errors
}
@ -74,66 +106,58 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
fn append_to_grouped_errors(
&self,
grouped_errors: &mut Vec<GroupedMoveError<'tcx>>,
original_path: Place<'tcx>,
error: MoveError<'tcx>,
) {
match error {
MoveError::UnionMove { .. } => {
unimplemented!("don't know how to report union move errors yet.")
}
MoveError::IllegalMove { cannot_move_out_of: IllegalMoveOrigin { location, kind } } => {
// Note: that the only time we assign a place isn't a temporary
// to a user variable is when initializing it.
// If that ever stops being the case, then the ever initialized
// flow could be used.
if let Some(StatementKind::Assign(box (
place,
Rvalue::Use(Operand::Move(move_from)),
))) = self.body.basic_blocks[location.block]
.statements
.get(location.statement_index)
.map(|stmt| &stmt.kind)
{
if let Some(local) = place.as_local() {
let local_decl = &self.body.local_decls[local];
// opt_match_place is the
// match_span is the span of the expression being matched on
// match *x.y { ... } match_place is Some(*x.y)
// ^^^^ match_span is the span of *x.y
//
// opt_match_place is None for let [mut] x = ... statements,
// whether or not the right-hand side is a place expression
if let LocalInfo::User(BindingForm::Var(VarBindingForm {
opt_match_place: Some((opt_match_place, match_span)),
binding_mode: _,
opt_ty_info: _,
pat_span: _,
})) = *local_decl.local_info()
{
let stmt_source_info = self.body.source_info(location);
self.append_binding_error(
grouped_errors,
kind,
original_path,
*move_from,
local,
opt_match_place,
match_span,
stmt_source_info.span,
);
return;
}
}
}
let MoveError { place: original_path, location, kind } = error;
let move_spans = self.move_spans(original_path.as_ref(), location);
grouped_errors.push(GroupedMoveError::OtherIllegalMove {
use_spans: move_spans,
original_path,
kind,
});
// Note: that the only time we assign a place isn't a temporary
// to a user variable is when initializing it.
// If that ever stops being the case, then the ever initialized
// flow could be used.
if let Some(StatementKind::Assign(box (place, Rvalue::Use(Operand::Move(move_from))))) =
self.body.basic_blocks[location.block]
.statements
.get(location.statement_index)
.map(|stmt| &stmt.kind)
{
if let Some(local) = place.as_local() {
let local_decl = &self.body.local_decls[local];
// opt_match_place is the
// match_span is the span of the expression being matched on
// match *x.y { ... } match_place is Some(*x.y)
// ^^^^ match_span is the span of *x.y
//
// opt_match_place is None for let [mut] x = ... statements,
// whether or not the right-hand side is a place expression
if let LocalInfo::User(BindingForm::Var(VarBindingForm {
opt_match_place: Some((opt_match_place, match_span)),
binding_mode: _,
opt_ty_info: _,
pat_span: _,
})) = *local_decl.local_info()
{
let stmt_source_info = self.body.source_info(location);
self.append_binding_error(
grouped_errors,
kind,
original_path,
*move_from,
local,
opt_match_place,
match_span,
stmt_source_info.span,
);
return;
}
}
}
let move_spans = self.move_spans(original_path.as_ref(), location);
grouped_errors.push(GroupedMoveError::OtherIllegalMove {
use_spans: move_spans,
original_path,
kind,
});
}
fn append_binding_error(

233
compiler/rustc_borrowck/src/lib.rs
View file

@ -31,13 +31,8 @@ use rustc_index::{IndexSlice, IndexVec};
use rustc_infer::infer::{
InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin, TyCtxtInferExt,
};
use rustc_middle::mir::{
traversal, Body, ClearCrossCrate, Local, Location, MutBorrowKind, Mutability,
NonDivergingIntrinsic, Operand, Place, PlaceElem, PlaceRef, VarDebugInfoContents,
};
use rustc_middle::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
use rustc_middle::mir::{ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
use rustc_middle::mir::tcx::PlaceTy;
use rustc_middle::mir::*;
use rustc_middle::query::Providers;
use rustc_middle::traits::DefiningAnchor;
use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
@ -55,13 +50,13 @@ use rustc_mir_dataflow::impls::{
EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
};
use rustc_mir_dataflow::move_paths::{InitIndex, MoveOutIndex, MovePathIndex};
use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult, MoveData, MoveError};
use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult, MoveData};
use rustc_mir_dataflow::Analysis;
use rustc_mir_dataflow::MoveDataParamEnv;
use crate::session_diagnostics::VarNeedNotMut;
use self::diagnostics::{AccessKind, RegionName};
use self::diagnostics::{AccessKind, IllegalMoveOriginKind, MoveError, RegionName};
use self::location::LocationTable;
use self::prefixes::PrefixSet;
use consumers::{BodyWithBorrowckFacts, ConsumerOptions};
@ -224,14 +219,10 @@ fn do_mir_borrowck<'tcx>(
let location_table_owned = LocationTable::new(body);
let location_table = &location_table_owned;
let (move_data, move_errors): (MoveData<'tcx>, Vec<(Place<'tcx>, MoveError<'tcx>)>) =
match MoveData::gather_moves(&body, tcx, param_env) {
Ok(move_data) => (move_data, Vec::new()),
Err((move_data, move_errors)) => (move_data, move_errors),
};
let promoted_errors = promoted
let move_data = MoveData::gather_moves(&body, tcx, param_env, |_| true);
let promoted_move_data = promoted
.iter_enumerated()
.map(|(idx, body)| (idx, MoveData::gather_moves(&body, tcx, param_env)));
.map(|(idx, body)| (idx, MoveData::gather_moves(&body, tcx, param_env, |_| true)));
let mdpe = MoveDataParamEnv { move_data, param_env };
@ -313,36 +304,49 @@ fn do_mir_borrowck<'tcx>(
true
};
for (idx, move_data_results) in promoted_errors {
let promoted_body = &promoted[idx];
for (idx, move_data) in promoted_move_data {
use rustc_middle::mir::visit::Visitor;
if let Err((move_data, move_errors)) = move_data_results {
let mut promoted_mbcx = MirBorrowckCtxt {
infcx: &infcx,
param_env,
body: promoted_body,
move_data: &move_data,
location_table, // no need to create a real one for the promoted, it is not used
movable_coroutine,
fn_self_span_reported: Default::default(),
locals_are_invalidated_at_exit,
access_place_error_reported: Default::default(),
reservation_error_reported: Default::default(),
uninitialized_error_reported: Default::default(),
regioncx: regioncx.clone(),
used_mut: Default::default(),
used_mut_upvars: SmallVec::new(),
borrow_set: Rc::clone(&borrow_set),
upvars: Vec::new(),
local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
region_names: RefCell::default(),
next_region_name: RefCell::new(1),
polonius_output: None,
errors,
};
promoted_mbcx.report_move_errors(move_errors);
errors = promoted_mbcx.errors;
let promoted_body = &promoted[idx];
let mut promoted_mbcx = MirBorrowckCtxt {
infcx: &infcx,
param_env,
body: promoted_body,
move_data: &move_data,
location_table, // no need to create a real one for the promoted, it is not used
movable_coroutine,
fn_self_span_reported: Default::default(),
locals_are_invalidated_at_exit,
access_place_error_reported: Default::default(),
reservation_error_reported: Default::default(),
uninitialized_error_reported: Default::default(),
regioncx: regioncx.clone(),
used_mut: Default::default(),
used_mut_upvars: SmallVec::new(),
borrow_set: Rc::clone(&borrow_set),
upvars: Vec::new(),
local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
region_names: RefCell::default(),
next_region_name: RefCell::new(1),
polonius_output: None,
move_errors: Vec::new(),
errors,
};
MoveVisitor { ctxt: &mut promoted_mbcx }.visit_body(promoted_body);
promoted_mbcx.report_move_errors();
errors = promoted_mbcx.errors;
struct MoveVisitor<'a, 'cx, 'tcx> {
ctxt: &'a mut MirBorrowckCtxt<'cx, 'tcx>,
}
impl<'tcx> Visitor<'tcx> for MoveVisitor<'_, '_, 'tcx> {
fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
if let Operand::Move(place) = operand {
self.ctxt.check_movable_place(location, *place);
}
}
}
}
let mut mbcx = MirBorrowckCtxt {
@ -366,6 +370,7 @@ fn do_mir_borrowck<'tcx>(
region_names: RefCell::default(),
next_region_name: RefCell::new(1),
polonius_output,
move_errors: Vec::new(),
errors,
};
@ -378,8 +383,6 @@ fn do_mir_borrowck<'tcx>(
borrows: flow_borrows,
};
mbcx.report_move_errors(move_errors);
rustc_mir_dataflow::visit_results(
body,
traversal::reverse_postorder(body).map(|(bb, _)| bb),
@ -387,6 +390,8 @@ fn do_mir_borrowck<'tcx>(
&mut mbcx,
);
mbcx.report_move_errors();
// For each non-user used mutable variable, check if it's been assigned from
// a user-declared local. If so, then put that local into the used_mut set.
// Note that this set is expected to be small - only upvars from closures
@ -595,6 +600,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
polonius_output: Option<Rc<PoloniusOutput>>,
errors: error::BorrowckErrors<'tcx>,
move_errors: Vec<MoveError<'tcx>>,
}
// Check that:
@ -725,7 +731,6 @@ impl<'cx, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx, R> for MirBorro
}
TerminatorKind::Assert { cond, expected: _, msg, target: _, unwind: _ } => {
self.consume_operand(loc, (cond, span), flow_state);
use rustc_middle::mir::AssertKind;
if let AssertKind::BoundsCheck { len, index } = &**msg {
self.consume_operand(loc, (len, span), flow_state);
self.consume_operand(loc, (index, span), flow_state);
@ -1409,7 +1414,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
// As such we have to search for the local that this
// capture comes from and mark it as being used as mut.
let temp_mpi = self.move_data.rev_lookup.find_local(local);
let Some(temp_mpi) = self.move_data.rev_lookup.find_local(local) else {
bug!("temporary should be tracked");
};
let init = if let [init_index] = *self.move_data.init_path_map[temp_mpi] {
&self.move_data.inits[init_index]
} else {
@ -1469,6 +1476,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
);
}
Operand::Move(place) => {
// Check if moving from this place makes sense.
self.check_movable_place(location, place);
// move of place: check if this is move of already borrowed path
self.access_place(
location,
@ -1590,6 +1600,131 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
}
fn check_movable_place(&mut self, location: Location, place: Place<'tcx>) {
use IllegalMoveOriginKind::*;
let body = self.body;
let tcx = self.infcx.tcx;
let mut place_ty = PlaceTy::from_ty(body.local_decls[place.local].ty);
for (place_ref, elem) in place.iter_projections() {
match elem {
ProjectionElem::Deref => match place_ty.ty.kind() {
ty::Ref(..) | ty::RawPtr(..) => {
self.move_errors.push(MoveError::new(
place,
location,
BorrowedContent {
target_place: place_ref.project_deeper(&[elem], tcx),
},
));
return;
}
ty::Adt(adt, _) => {
if !adt.is_box() {
bug!("Adt should be a box type when Place is deref");
}
}
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(_, _, _)
| ty::Closure(_, _)
| ty::Coroutine(_, _, _)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Tuple(_)
| ty::Alias(_, _)
| ty::Param(_)
| ty::Bound(_, _)
| ty::Infer(_)
| ty::Error(_)
| ty::Placeholder(_) => {
bug!("When Place is Deref it's type shouldn't be {place_ty:#?}")
}
},
ProjectionElem::Field(_, _) => match place_ty.ty.kind() {
ty::Adt(adt, _) => {
if adt.has_dtor(tcx) {
self.move_errors.push(MoveError::new(
place,
location,
InteriorOfTypeWithDestructor { container_ty: place_ty.ty },
));
return;
}
}
ty::Closure(_, _) | ty::Coroutine(_, _, _) | ty::Tuple(_) => (),
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(_, _, _)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Alias(_, _)
| ty::Param(_)
| ty::Bound(_, _)
| ty::Infer(_)
| ty::Error(_)
| ty::Placeholder(_) => bug!(
"When Place contains ProjectionElem::Field it's type shouldn't be {place_ty:#?}"
),
},
ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
match place_ty.ty.kind() {
ty::Slice(_) => {
self.move_errors.push(MoveError::new(
place,
location,
InteriorOfSliceOrArray { ty: place_ty.ty, is_index: false },
));
return;
}
ty::Array(_, _) => (),
_ => bug!("Unexpected type {:#?}", place_ty.ty),
}
}
ProjectionElem::Index(_) => match place_ty.ty.kind() {
ty::Array(..) | ty::Slice(..) => {
self.move_errors.push(MoveError::new(
place,
location,
InteriorOfSliceOrArray { ty: place_ty.ty, is_index: true },
));
return;
}
_ => bug!("Unexpected type {place_ty:#?}"),
},
// `OpaqueCast`: only transmutes the type, so no moves there.
// `Downcast` : only changes information about a `Place` without moving.
// `Subtype` : only transmutes the type, so no moves.
// So it's safe to skip these.
ProjectionElem::OpaqueCast(_)
| ProjectionElem::Subtype(_)
| ProjectionElem::Downcast(_, _) => (),
}
place_ty = place_ty.projection_ty(tcx, elem);
}
}
fn check_if_full_path_is_moved(
&mut self,
location: Location,
@ -2074,7 +2209,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
local: Local,
flow_state: &Flows<'cx, 'tcx>,
) -> Option<InitIndex> {
let mpi = self.move_data.rev_lookup.find_local(local);
let mpi = self.move_data.rev_lookup.find_local(local)?;
let ii = &self.move_data.init_path_map[mpi];
ii.into_iter().find(|&&index| flow_state.ever_inits.contains(index)).copied()
}

2
compiler/rustc_borrowck/src/type_check/liveness/trace.rs
View file

@ -317,7 +317,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
fn compute_drop_live_points_for(&mut self, local: Local) {
debug!("compute_drop_live_points_for(local={:?})", local);
let mpi = self.cx.move_data.rev_lookup.find_local(local);
let Some(mpi) = self.cx.move_data.rev_lookup.find_local(local) else { return };
debug!("compute_drop_live_points_for: mpi = {:?}", mpi);
// Find the drops where `local` is initialized.