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Auto merge of #98145 - ouz-a:some_branch, r=oli-obk

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Pull Derefer before ElaborateDrops

_Follow up work to #97025 #96549 #96116 #95887 #95649_

This moves `Derefer` before `ElaborateDrops` and creates a new `Rvalue` called `VirtualRef` that allows us to bypass many constraints for `DerefTemp`.

r? `@oli-obk`
This commit is contained in:
bors 2022-07-13 14:32:33 +00:00
commit 42bd138126
43 changed files with 401 additions and 227 deletions
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13
compiler/rustc_mir_transform/src/add_retag.rs
View file

@ -70,17 +70,6 @@ fn may_contain_reference<'tcx>(ty: Ty<'tcx>, depth: u32, tcx: TyCtxt<'tcx>) -> b
}
}
/// Determines whether or not this LocalDecl is temp, if not it needs retagging.
fn is_not_temp<'tcx>(local_decl: &LocalDecl<'tcx>) -> bool {
if let Some(local_info) = &local_decl.local_info {
match local_info.as_ref() {
LocalInfo::DerefTemp => return false,
_ => (),
};
}
return true;
}
impl<'tcx> MirPass<'tcx> for AddRetag {
fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
sess.opts.debugging_opts.mir_emit_retag
@ -98,7 +87,7 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
// a temporary and retag on that.
is_stable(place.as_ref())
&& may_contain_reference(place.ty(&*local_decls, tcx).ty, /*depth*/ 3, tcx)
&& is_not_temp(&local_decls[place.local])
&& !local_decls[place.local].is_deref_temp()
};
let place_base_raw = |place: &Place<'tcx>| {
// If this is a `Deref`, get the type of what we are deref'ing.

1
compiler/rustc_mir_transform/src/const_prop.rs
View file

@ -621,6 +621,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
// There's no other checking to do at this time.
Rvalue::Aggregate(..)
| Rvalue::Use(..)
| Rvalue::CopyForDeref(..)
| Rvalue::Repeat(..)
| Rvalue::Len(..)
| Rvalue::Cast(..)

1
compiler/rustc_mir_transform/src/const_prop_lint.rs
View file

@ -693,6 +693,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
// There's no other checking to do at this time.
Rvalue::Aggregate(..)
| Rvalue::Use(..)
| Rvalue::CopyForDeref(..)
| Rvalue::Repeat(..)
| Rvalue::Len(..)
| Rvalue::Cast(..)

3
compiler/rustc_mir_transform/src/deref_separator.rs
View file

@ -35,6 +35,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
last_deref_idx = idx;
}
}
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if !p_ref.projection.is_empty() && p_elem == ProjectionElem::Deref {
let ty = p_ref.ty(&self.local_decls, self.tcx).ty;
@ -54,7 +55,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
self.patcher.add_assign(
loc,
Place::from(temp),
Rvalue::Use(Operand::Move(deref_place)),
Rvalue::CopyForDeref(deref_place),
);
place_local = temp;
last_len = p_ref.projection.len();

36
compiler/rustc_mir_transform/src/elaborate_drops.rs
View file

@ -1,3 +1,4 @@
use crate::deref_separator::deref_finder;
use crate::MirPass;
use rustc_data_structures::fx::FxHashMap;
use rustc_index::bit_set::BitSet;
@ -9,6 +10,7 @@ use rustc_mir_dataflow::elaborate_drops::{DropElaborator, DropFlagMode, DropStyl
use rustc_mir_dataflow::impls::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
use rustc_mir_dataflow::on_lookup_result_bits;
use rustc_mir_dataflow::un_derefer::UnDerefer;
use rustc_mir_dataflow::MoveDataParamEnv;
use rustc_mir_dataflow::{on_all_children_bits, on_all_drop_children_bits};
use rustc_mir_dataflow::{Analysis, ResultsCursor};
@ -26,6 +28,8 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
debug!("elaborate_drops({:?} @ {:?})", body.source, body.span);
let mut un_derefer = UnDerefer { tcx: tcx, derefer_sidetable: Default::default() };
un_derefer.ref_finder(body);
let def_id = body.source.def_id();
let param_env = tcx.param_env_reveal_all_normalized(def_id);
let move_data = match MoveData::gather_moves(body, tcx, param_env) {
@ -41,7 +45,7 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
let elaborate_patch = {
let body = &*body;
let env = MoveDataParamEnv { move_data, param_env };
let dead_unwinds = find_dead_unwinds(tcx, body, &env);
let dead_unwinds = find_dead_unwinds(tcx, body, &env, &un_derefer);
let inits = MaybeInitializedPlaces::new(tcx, body, &env)
.into_engine(tcx, body)
@ -65,10 +69,12 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
init_data: InitializationData { inits, uninits },
drop_flags: Default::default(),
patch: MirPatch::new(body),
un_derefer: un_derefer,
}
.elaborate()
};
elaborate_patch.apply(body);
deref_finder(tcx, body);
}
}
@ -79,6 +85,7 @@ fn find_dead_unwinds<'tcx>(
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
env: &MoveDataParamEnv<'tcx>,
und: &UnDerefer<'tcx>,
) -> BitSet<BasicBlock> {
debug!("find_dead_unwinds({:?})", body.span);
// We only need to do this pass once, because unwind edges can only
@ -92,7 +99,9 @@ fn find_dead_unwinds<'tcx>(
for (bb, bb_data) in body.basic_blocks().iter_enumerated() {
let place = match bb_data.terminator().kind {
TerminatorKind::Drop { ref place, unwind: Some(_), .. }
| TerminatorKind::DropAndReplace { ref place, unwind: Some(_), .. } => place,
| TerminatorKind::DropAndReplace { ref place, unwind: Some(_), .. } => {
und.derefer(place.as_ref(), body).unwrap_or(*place)
}
_ => continue,
};
@ -256,6 +265,7 @@ struct ElaborateDropsCtxt<'a, 'tcx> {
init_data: InitializationData<'a, 'tcx>,
drop_flags: FxHashMap<MovePathIndex, Local>,
patch: MirPatch<'tcx>,
un_derefer: UnDerefer<'tcx>,
}
impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
@ -298,7 +308,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
let terminator = data.terminator();
let place = match terminator.kind {
TerminatorKind::Drop { ref place, .. }
| TerminatorKind::DropAndReplace { ref place, .. } => place,
| TerminatorKind::DropAndReplace { ref place, .. } => {
self.un_derefer.derefer(place.as_ref(), self.body).unwrap_or(*place)
}
_ => continue,
};
@ -312,12 +324,17 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
LookupResult::Parent(None) => continue,
LookupResult::Parent(Some(parent)) => {
let (_maybe_live, maybe_dead) = self.init_data.maybe_live_dead(parent);
if self.body.local_decls[place.local].is_deref_temp() {
continue;
}
if maybe_dead {
self.tcx.sess.delay_span_bug(
terminator.source_info.span,
&format!(
"drop of untracked, uninitialized value {:?}, place {:?} ({:?})",
bb, place, path,
bb, place, path
),
);
}
@ -348,7 +365,11 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
let resume_block = self.patch.resume_block();
match terminator.kind {
TerminatorKind::Drop { place, target, unwind } => {
TerminatorKind::Drop { mut place, target, unwind } => {
if let Some(new_place) = self.un_derefer.derefer(place.as_ref(), self.body) {
place = new_place;
}
self.init_data.seek_before(loc);
match self.move_data().rev_lookup.find(place.as_ref()) {
LookupResult::Exact(path) => elaborate_drop(
@ -372,9 +393,12 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
}
}
}
TerminatorKind::DropAndReplace { place, ref value, target, unwind } => {
TerminatorKind::DropAndReplace { mut place, ref value, target, unwind } => {
assert!(!data.is_cleanup);
if let Some(new_place) = self.un_derefer.derefer(place.as_ref(), self.body) {
place = new_place;
}
self.elaborate_replace(loc, place, value, target, unwind);
}
_ => continue,

2
compiler/rustc_mir_transform/src/lib.rs
View file

@ -420,6 +420,7 @@ fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tc
&remove_noop_landing_pads::RemoveNoopLandingPads,
&cleanup_post_borrowck::CleanupNonCodegenStatements,
&simplify::SimplifyCfg::new("early-opt"),
&deref_separator::Derefer,
// These next passes must be executed together
&add_call_guards::CriticalCallEdges,
&elaborate_drops::ElaborateDrops,
@ -432,7 +433,6 @@ fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tc
&add_moves_for_packed_drops::AddMovesForPackedDrops,
// `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
// but before optimizations begin.
&deref_separator::Derefer,
&elaborate_box_derefs::ElaborateBoxDerefs,
&add_retag::AddRetag,
&lower_intrinsics::LowerIntrinsics,

2
compiler/rustc_mir_transform/src/separate_const_switch.rs
View file

@ -218,6 +218,7 @@ fn is_likely_const<'tcx>(mut tracked_place: Place<'tcx>, block: &BasicBlockData<
// These rvalues move the place to track
Rvalue::Cast(_, Operand::Copy(place) | Operand::Move(place), _)
| Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
| Rvalue::CopyForDeref(place)
| Rvalue::UnaryOp(_, Operand::Copy(place) | Operand::Move(place))
| Rvalue::Discriminant(place) => tracked_place = place,
}
@ -279,6 +280,7 @@ fn find_determining_place<'tcx>(
// that may be const in the predecessor
Rvalue::Use(Operand::Move(new) | Operand::Copy(new))
| Rvalue::UnaryOp(_, Operand::Copy(new) | Operand::Move(new))
| Rvalue::CopyForDeref(new)
| Rvalue::Cast(_, Operand::Move(new) | Operand::Copy(new), _)
| Rvalue::Repeat(Operand::Move(new) | Operand::Copy(new), _)
| Rvalue::Discriminant(new)