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Refactor and add PlaceContext::AscribeUserTy.
This commit refactors `PlaceContext` to split it into four different smaller enums based on if the context represents a mutating use, non-mutating use, maybe-mutating use or a non-use (this is based on the recommendation from @oli-obk on Zulip[1]). This commit then introduces a `PlaceContext::AscribeUserTy` variant. `StatementKind::AscribeUserTy` is now correctly mapped to `PlaceContext::AscribeUserTy` instead of `PlaceContext::Validate`. `PlaceContext::AscribeUserTy` can also now be correctly categorized as a non-use which fixes an issue with constant promotion in statics after a cast introduces a `AscribeUserTy` statement. [1]: https://rust-lang.zulipchat.com/#narrow/stream/122657-wg-nll/subject/.2355288.20cast.20fails.20to.20promote.20to.20'static/near/136536949
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13 files changed

+308
-195
lines changed

13 files changed

+308
-195
lines changed

‎src/librustc/mir/visit.rs‎

Lines changed: 191 additions & 99 deletions
Large diffs are not rendered by default.

‎src/librustc_codegen_llvm/mir/analyze.rs‎

Lines changed: 32 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@ use rustc_data_structures::bit_set::BitSet;
1515
use rustc_data_structures::graph::dominators::Dominators;
1616
use rustc_data_structures::indexed_vec::{Idx, IndexVec};
1717
use rustc::mir::{self, Location, TerminatorKind};
18-
use rustc::mir::visit::{Visitor, PlaceContext};
18+
use rustc::mir::visit::{Visitor, PlaceContext, MutatingUseContext, NonMutatingUseContext};
1919
use rustc::mir::traversal;
2020
use rustc::ty;
2121
use rustc::ty::layout::LayoutOf;
@@ -116,7 +116,11 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
116116
self.not_ssa(index);
117117
}
118118
} else {
119-
self.visit_place(place, PlaceContext::Store, location);
119+
self.visit_place(
120+
place,
121+
PlaceContext::MutatingUse(MutatingUseContext::Store),
122+
location
123+
);
120124
}
121125

122126
self.visit_rvalue(rvalue, location);
@@ -142,7 +146,11 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
142146
// is not guaranteed to be statically dominated by the
143147
// definition of x, so x must always be in an alloca.
144148
if let mir::Operand::Move(ref place) = args[0] {
145-
self.visit_place(place, PlaceContext::Drop, location);
149+
self.visit_place(
150+
place,
151+
PlaceContext::MutatingUse(MutatingUseContext::Drop),
152+
location
153+
);
146154
}
147155
}
148156
}
@@ -160,7 +168,8 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
160168
if let mir::Place::Projection(ref proj) = *place {
161169
// Allow uses of projections that are ZSTs or from scalar fields.
162170
let is_consume = match context {
163-
PlaceContext::Copy | PlaceContext::Move => true,
171+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
172+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => true,
164173
_ => false
165174
};
166175
if is_consume {
@@ -190,7 +199,11 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
190199

191200
// A deref projection only reads the pointer, never needs the place.
192201
if let mir::ProjectionElem::Deref = proj.elem {
193-
return self.visit_place(&proj.base, PlaceContext::Copy, location);
202+
return self.visit_place(
203+
&proj.base,
204+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
205+
location
206+
);
194207
}
195208
}
196209

@@ -202,16 +215,14 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
202215
context: PlaceContext<'tcx>,
203216
location: Location) {
204217
match context {
205-
PlaceContext::Call => {
218+
PlaceContext::MutatingUse(MutatingUseContext::Call) => {
206219
self.assign(local, location);
207220
}
208221

209-
PlaceContext::StorageLive |
210-
PlaceContext::StorageDead |
211-
PlaceContext::Validate => {}
222+
PlaceContext::NonUse(_) => {}
212223

213-
PlaceContext::Copy |
214-
PlaceContext::Move => {
224+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
225+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => {
215226
// Reads from uninitialized variables (e.g. in dead code, after
216227
// optimizations) require locals to be in (uninitialized) memory.
217228
// NB: there can be uninitialized reads of a local visited after
@@ -227,15 +238,19 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
227238
}
228239
}
229240

230-
PlaceContext::Inspect |
231-
PlaceContext::Store |
232-
PlaceContext::AsmOutput |
233-
PlaceContext::Borrow { .. } |
234-
PlaceContext::Projection(..) => {
241+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect) |
242+
PlaceContext::MutatingUse(MutatingUseContext::Store) |
243+
PlaceContext::MutatingUse(MutatingUseContext::AsmOutput) |
244+
PlaceContext::MutatingUse(MutatingUseContext::Borrow(..)) |
245+
PlaceContext::MutatingUse(MutatingUseContext::Projection) |
246+
PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow(..)) |
247+
PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow(..)) |
248+
PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow(..)) |
249+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => {
235250
self.not_ssa(local);
236251
}
237252

238-
PlaceContext::Drop => {
253+
PlaceContext::MutatingUse(MutatingUseContext::Drop) => {
239254
let ty = mir::Place::Local(local).ty(self.fx.mir, self.fx.cx.tcx);
240255
let ty = self.fx.monomorphize(&ty.to_ty(self.fx.cx.tcx));
241256

‎src/librustc_mir/borrow_check/borrow_set.rs‎

Lines changed: 10 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,9 @@ use borrow_check::place_ext::PlaceExt;
1212
use dataflow::indexes::BorrowIndex;
1313
use dataflow::move_paths::MoveData;
1414
use rustc::mir::traversal;
15-
use rustc::mir::visit::{PlaceContext, Visitor};
15+
use rustc::mir::visit::{
16+
PlaceContext, Visitor, NonUseContext, MutatingUseContext, NonMutatingUseContext
17+
};
1618
use rustc::mir::{self, Location, Mir, Place, Local};
1719
use rustc::ty::{Region, TyCtxt};
1820
use rustc::util::nodemap::{FxHashMap, FxHashSet};
@@ -116,7 +118,7 @@ impl LocalsStateAtExit {
116118

117119
impl<'tcx> Visitor<'tcx> for HasStorageDead {
118120
fn visit_local(&mut self, local: &Local, ctx: PlaceContext<'tcx>, _: Location) {
119-
if ctx == PlaceContext::StorageDead {
121+
if ctx == PlaceContext::NonUse(NonUseContext::StorageDead) {
120122
self.0.insert(*local);
121123
}
122124
}
@@ -266,7 +268,9 @@ impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
266268

267269
// Watch out: the use of TMP in the borrow itself
268270
// doesn't count as an activation. =)
269-
if borrow_data.reserve_location == location && context == PlaceContext::Store {
271+
if borrow_data.reserve_location == location &&
272+
context == PlaceContext::MutatingUse(MutatingUseContext::Store)
273+
{
270274
return;
271275
}
272276

@@ -287,10 +291,9 @@ impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
287291
borrow_data.activation_location = match context {
288292
// The use of TMP in a shared borrow does not
289293
// count as an actual activation.
290-
PlaceContext::Borrow { kind: mir::BorrowKind::Shared, .. }
291-
| PlaceContext::Borrow { kind: mir::BorrowKind::Shallow, .. } => {
292-
TwoPhaseActivation::NotActivated
293-
}
294+
PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow(..)) |
295+
PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow(..)) =>
296+
TwoPhaseActivation::NotActivated,
294297
_ => {
295298
// Double check: This borrow is indeed a two-phase borrow (that is,
296299
// we are 'transitioning' from `NotActivated` to `ActivatedAt`) and

‎src/librustc_mir/borrow_check/nll/type_check/mod.rs‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -35,7 +35,7 @@ use rustc::infer::outlives::env::RegionBoundPairs;
3535
use rustc::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
3636
use rustc::mir::interpret::EvalErrorKind::BoundsCheck;
3737
use rustc::mir::tcx::PlaceTy;
38-
use rustc::mir::visit::{PlaceContext, Visitor};
38+
use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext};
3939
use rustc::mir::*;
4040
use rustc::traits::query::type_op;
4141
use rustc::traits::query::type_op::custom::CustomTypeOp;
@@ -472,9 +472,9 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
472472
}
473473
Place::Projection(ref proj) => {
474474
let base_context = if context.is_mutating_use() {
475-
PlaceContext::Projection(Mutability::Mut)
475+
PlaceContext::MutatingUse(MutatingUseContext::Projection)
476476
} else {
477-
PlaceContext::Projection(Mutability::Not)
477+
PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
478478
};
479479
let base_ty = self.sanitize_place(&proj.base, location, base_context);
480480
if let PlaceTy::Ty { ty } = base_ty {
@@ -488,7 +488,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
488488
self.sanitize_projection(base_ty, &proj.elem, place, location)
489489
}
490490
};
491-
if let PlaceContext::Copy = context {
491+
if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
492492
let tcx = self.tcx();
493493
let trait_ref = ty::TraitRef {
494494
def_id: tcx.lang_items().copy_trait().unwrap(),

‎src/librustc_mir/borrow_check/used_muts.rs‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,6 @@ use rustc::mir::{Local, Location, Place};
1414
use rustc_data_structures::fx::FxHashSet;
1515

1616
use borrow_check::MirBorrowckCtxt;
17-
use util::collect_writes::is_place_assignment;
1817

1918
impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
2019
/// Walks the MIR looking for assignments to a set of locals, as part of the unused mutable
@@ -46,7 +45,7 @@ impl<'visit, 'cx, 'gcx, 'tcx> Visitor<'tcx> for GatherUsedMutsVisitor<'visit, 'c
4645
return;
4746
}
4847

49-
if is_place_assignment(&place_context) {
48+
if place_context.is_place_assignment() {
5049
// Propagate the Local assigned at this Location as a used mutable local variable
5150
for moi in &self.mbcx.move_data.loc_map[location] {
5251
let mpi = &self.mbcx.move_data.moves[*moi].path;

‎src/librustc_mir/transform/check_unsafety.rs‎

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@ use rustc::hir::Node;
1919
use rustc::hir::def_id::DefId;
2020
use rustc::lint::builtin::{SAFE_EXTERN_STATICS, SAFE_PACKED_BORROWS, UNUSED_UNSAFE};
2121
use rustc::mir::*;
22-
use rustc::mir::visit::{PlaceContext, Visitor};
22+
use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext};
2323

2424
use syntax::ast;
2525
use syntax::symbol::Symbol;
@@ -152,7 +152,7 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
152152
place: &Place<'tcx>,
153153
context: PlaceContext<'tcx>,
154154
location: Location) {
155-
if let PlaceContext::Borrow { .. } = context {
155+
if context.is_borrow() {
156156
if util::is_disaligned(self.tcx, self.mir, self.param_env, place) {
157157
let source_info = self.source_info;
158158
let lint_root =
@@ -193,9 +193,11 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
193193
}
194194
ty::Adt(adt, _) => {
195195
if adt.is_union() {
196-
if context == PlaceContext::Store ||
197-
context == PlaceContext::AsmOutput ||
198-
context == PlaceContext::Drop
196+
if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
197+
context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
198+
context == PlaceContext::MutatingUse(
199+
MutatingUseContext::AsmOutput
200+
)
199201
{
200202
let elem_ty = match elem {
201203
&ProjectionElem::Field(_, ty) => ty,

‎src/librustc_mir/transform/const_prop.rs‎

Lines changed: 8 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ use rustc::hir::def::Def;
1616
use rustc::mir::{Constant, Location, Place, Mir, Operand, Rvalue, Local};
1717
use rustc::mir::{NullOp, UnOp, StatementKind, Statement, BasicBlock, LocalKind};
1818
use rustc::mir::{TerminatorKind, ClearCrossCrate, SourceInfo, BinOp, ProjectionElem};
19-
use rustc::mir::visit::{Visitor, PlaceContext};
19+
use rustc::mir::visit::{Visitor, PlaceContext, MutatingUseContext, NonMutatingUseContext};
2020
use rustc::mir::interpret::{
2121
ConstEvalErr, EvalErrorKind, Scalar, GlobalId, EvalResult,
2222
};
@@ -533,17 +533,18 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
533533
// Constants must have at most one write
534534
// FIXME(oli-obk): we could be more powerful here, if the multiple writes
535535
// only occur in independent execution paths
536-
Store => if self.found_assignment[local] {
536+
MutatingUse(MutatingUseContext::Store) => if self.found_assignment[local] {
537537
self.can_const_prop[local] = false;
538538
} else {
539539
self.found_assignment[local] = true
540540
},
541541
// Reading constants is allowed an arbitrary number of times
542-
Copy | Move |
543-
StorageDead | StorageLive |
544-
Validate |
545-
Projection(_) |
546-
Inspect => {},
542+
NonMutatingUse(NonMutatingUseContext::Copy) |
543+
NonMutatingUse(NonMutatingUseContext::Move) |
544+
NonMutatingUse(NonMutatingUseContext::Inspect) |
545+
NonMutatingUse(NonMutatingUseContext::Projection) |
546+
MutatingUse(MutatingUseContext::Projection) |
547+
NonUse(_) => {},
547548
_ => self.can_const_prop[local] = false,
548549
}
549550
}

‎src/librustc_mir/transform/promote_consts.rs‎

Lines changed: 9 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
//! move analysis runs after promotion on broken MIR.
2424
2525
use rustc::mir::*;
26-
use rustc::mir::visit::{PlaceContext, MutVisitor, Visitor};
26+
use rustc::mir::visit::{PlaceContext, MutatingUseContext, MutVisitor, Visitor};
2727
use rustc::mir::traversal::ReversePostorder;
2828
use rustc::ty::TyCtxt;
2929
use syntax_pos::Span;
@@ -97,11 +97,11 @@ impl<'tcx> Visitor<'tcx> for TempCollector<'tcx> {
9797

9898
// Ignore drops, if the temp gets promoted,
9999
// then it's constant and thus drop is noop.
100-
// Storage live ranges are also irrelevant.
101-
if context.is_drop() || context.is_storage_marker() {
100+
// Non-uses are also irrelevent.
101+
if context.is_drop() || !context.is_use() {
102102
debug!(
103-
"visit_local: context.is_drop={:?} context.is_storage_marker={:?}",
104-
context.is_drop(), context.is_storage_marker(),
103+
"visit_local: context.is_drop={:?} context.is_use={:?}",
104+
context.is_drop(), context.is_use(),
105105
);
106106
return;
107107
}
@@ -110,9 +110,9 @@ impl<'tcx> Visitor<'tcx> for TempCollector<'tcx> {
110110
debug!("visit_local: temp={:?}", temp);
111111
if *temp == TempState::Undefined {
112112
match context {
113-
PlaceContext::Store |
114-
PlaceContext::AsmOutput |
115-
PlaceContext::Call => {
113+
PlaceContext::MutatingUse(MutatingUseContext::Store) |
114+
PlaceContext::MutatingUse(MutatingUseContext::AsmOutput) |
115+
PlaceContext::MutatingUse(MutatingUseContext::Call) => {
116116
*temp = TempState::Defined {
117117
location,
118118
uses: 0
@@ -124,10 +124,7 @@ impl<'tcx> Visitor<'tcx> for TempCollector<'tcx> {
124124
} else if let TempState::Defined { ref mut uses, .. } = *temp {
125125
// We always allow borrows, even mutable ones, as we need
126126
// to promote mutable borrows of some ZSTs e.g. `&mut []`.
127-
let allowed_use = match context {
128-
PlaceContext::Borrow {..} => true,
129-
_ => context.is_nonmutating_use()
130-
};
127+
let allowed_use = context.is_borrow() || context.is_nonmutating_use();
131128
debug!("visit_local: allowed_use={:?}", allowed_use);
132129
if allowed_use {
133130
*uses += 1;

‎src/librustc_mir/transform/qualify_consts.rs‎

Lines changed: 17 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@ use rustc::ty::cast::CastTy;
2626
use rustc::ty::query::Providers;
2727
use rustc::mir::*;
2828
use rustc::mir::traversal::ReversePostorder;
29-
use rustc::mir::visit::{PlaceContext, Visitor};
29+
use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext};
3030
use rustc::middle::lang_items;
3131
use rustc_target::spec::abi::Abi;
3232
use syntax::ast::LitKind;
@@ -271,7 +271,11 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
271271
// This must be an explicit assignment.
272272
_ => {
273273
// Catch more errors in the destination.
274-
self.visit_place(dest, PlaceContext::Store, location);
274+
self.visit_place(
275+
dest,
276+
PlaceContext::MutatingUse(MutatingUseContext::Store),
277+
location
278+
);
275279
self.statement_like();
276280
}
277281
}
@@ -610,10 +614,17 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
610614
}
611615

612616
if is_reborrow {
613-
self.super_place(place, PlaceContext::Borrow {
614-
region,
615-
kind
616-
}, location);
617+
let ctx = match kind {
618+
BorrowKind::Shared =>
619+
PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow(region)),
620+
BorrowKind::Shallow =>
621+
PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow(region)),
622+
BorrowKind::Unique =>
623+
PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow(region)),
624+
BorrowKind::Mut { .. } =>
625+
PlaceContext::MutatingUse(MutatingUseContext::Borrow(region)),
626+
};
627+
self.super_place(place, ctx, location);
617628
} else {
618629
self.super_rvalue(rvalue, location);
619630
}

‎src/librustc_mir/transform/simplify.rs‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -331,8 +331,10 @@ struct DeclMarker {
331331

332332
impl<'tcx> Visitor<'tcx> for DeclMarker {
333333
fn visit_local(&mut self, local: &Local, ctx: PlaceContext<'tcx>, _: Location) {
334-
// ignore these altogether, they get removed along with their otherwise unused decls.
335-
if ctx != PlaceContext::StorageLive && ctx != PlaceContext::StorageDead {
334+
// Ignore storage markers altogether, they get removed along with their otherwise unused
335+
// decls.
336+
// FIXME: Extend this to all non-uses.
337+
if !ctx.is_storage_marker() {
336338
self.locals.insert(*local);
337339
}
338340
}

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