Auto merge of #55959 - matthewjasper:remove-end-region, r=nikomatsakis

Cleanup from lexical MIR borrowck removal

Lexical MIR borrowck was removed months ago now, and `EndRegion`s are no longer used for MIRI verification.

* Remove `rustc::mir::StatementKind::EndRegion` and the `-Zemit_end_regions` flag
* Use `RegionVid` instead of `Region` in BorrowSet
* Rewrite drop generation to create fewer goto terminators.

r? @nikomatsakis

Author: bors

src/librustc/ich/impls_mir.rs

@@ -217,9 +217,6 @@ for mir::StatementKind<'gcx> {
             mir::StatementKind::StorageDead(ref place) => {
                 place.hash_stable(hcx, hasher);
             }
-            mir::StatementKind::EndRegion(ref region_scope) => {
-                region_scope.hash_stable(hcx, hasher);
-            }
             mir::StatementKind::EscapeToRaw(ref place) => {
                 place.hash_stable(hcx, hasher);
             }

src/librustc/mir/mod.rs

@@ -15,7 +15,6 @@
 use hir::def::CtorKind;
 use hir::def_id::DefId;
 use hir::{self, HirId, InlineAsm};
-use middle::region;
 use mir::interpret::{ConstValue, EvalErrorKind, Scalar};
 use mir::visit::MirVisitable;
 use rustc_apfloat::ieee::{Double, Single};
@@ -1789,10 +1788,6 @@ pub enum StatementKind<'tcx> {
     /// for more details.
     EscapeToRaw(Operand<'tcx>),
 
-    /// Mark one terminating point of a region scope (i.e. static region).
-    /// (The starting point(s) arise implicitly from borrows.)
-    EndRegion(region::Scope),
-
     /// Encodes a user's type ascription. These need to be preserved
     /// intact so that NLL can respect them. For example:
     ///
@@ -1846,8 +1841,6 @@ impl<'tcx> Debug for Statement<'tcx> {
         match self.kind {
             Assign(ref place, ref rv) => write!(fmt, "{:?} = {:?}", place, rv),
             FakeRead(ref cause, ref place) => write!(fmt, "FakeRead({:?}, {:?})", cause, place),
-            // (reuse lifetime rendering policy from ppaux.)
-            EndRegion(ref ce) => write!(fmt, "EndRegion({})", ty::ReScope(*ce)),
             Retag { fn_entry, ref place } =>
                 write!(fmt, "Retag({}{:?})", if fn_entry { "[fn entry] " } else { "" }, place),
             EscapeToRaw(ref place) => write!(fmt, "EscapeToRaw({:?})", place),
@@ -3028,7 +3021,6 @@ EnumTypeFoldableImpl! {
         (StatementKind::InlineAsm) { asm, outputs, inputs },
         (StatementKind::Retag) { fn_entry, place },
         (StatementKind::EscapeToRaw)(place),
-        (StatementKind::EndRegion)(a),
         (StatementKind::AscribeUserType)(a, v, b),
         (StatementKind::Nop),
     }

src/librustc/mir/visit.rs

@@ -377,7 +377,6 @@ macro_rules! make_mir_visitor {
                             location
                         );
                     }
-                    StatementKind::EndRegion(_) => {}
                     StatementKind::SetDiscriminant{ ref $($mutability)* place, .. } => {
                         self.visit_place(
                             place,

src/librustc/session/config.rs

@@ -1149,8 +1149,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "when debug-printing compiler state, do not include spans"), // o/w tests have closure@path
     identify_regions: bool = (false, parse_bool, [UNTRACKED],
         "make unnamed regions display as '# (where # is some non-ident unique id)"),
-    emit_end_regions: bool = (false, parse_bool, [UNTRACKED],
-        "emit EndRegion as part of MIR; enable transforms that solely process EndRegion"),
     borrowck: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "select which borrowck is used (`ast`, `mir`, `migrate`, or `compare`)"),
     two_phase_borrows: bool = (false, parse_bool, [UNTRACKED],

src/librustc/ty/context.rs

@@ -1540,13 +1540,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    /// Should we emit EndRegion MIR statements? These are consumed by
-    /// MIR borrowck, but not when NLL is used.
-    pub fn emit_end_regions(self) -> bool {
-        self.sess.opts.debugging_opts.emit_end_regions ||
-            self.use_mir_borrowck()
-    }
-
     #[inline]
     pub fn local_crate_exports_generics(self) -> bool {
         debug_assert!(self.sess.opts.share_generics());

src/librustc_codegen_ssa/mir/statement.rs

@@ -105,7 +105,6 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 bx
             }
             mir::StatementKind::FakeRead(..) |
-            mir::StatementKind::EndRegion(..) |
             mir::StatementKind::Retag { .. } |
             mir::StatementKind::EscapeToRaw { .. } |
             mir::StatementKind::AscribeUserType(..) |

src/librustc_mir/borrow_check/borrow_set.rs

@@ -9,14 +9,15 @@
 // except according to those terms.
 
 use borrow_check::place_ext::PlaceExt;
+use borrow_check::nll::ToRegionVid;
 use dataflow::indexes::BorrowIndex;
 use dataflow::move_paths::MoveData;
 use rustc::mir::traversal;
 use rustc::mir::visit::{
     PlaceContext, Visitor, NonUseContext, MutatingUseContext, NonMutatingUseContext
 };
 use rustc::mir::{self, Location, Mir, Place, Local};
-use rustc::ty::{Region, TyCtxt};
+use rustc::ty::{RegionVid, TyCtxt};
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::bit_set::BitSet;
@@ -42,7 +43,7 @@ crate struct BorrowSet<'tcx> {
 
     /// Every borrow has a region; this maps each such regions back to
     /// its borrow-indexes.
-    crate region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
+    crate region_map: FxHashMap<RegionVid, FxHashSet<BorrowIndex>>,
 
     /// Map from local to all the borrows on that local
     crate local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
@@ -77,7 +78,7 @@ crate struct BorrowData<'tcx> {
     /// What kind of borrow this is
     crate kind: mir::BorrowKind,
     /// The region for which this borrow is live
-    crate region: Region<'tcx>,
+    crate region: RegionVid,
     /// Place from which we are borrowing
     crate borrowed_place: mir::Place<'tcx>,
     /// Place to which the borrow was stored
@@ -92,13 +93,7 @@ impl<'tcx> fmt::Display for BorrowData<'tcx> {
             mir::BorrowKind::Unique => "uniq ",
             mir::BorrowKind::Mut { .. } => "mut ",
         };
-        let region = self.region.to_string();
-        let separator = if !region.is_empty() {
-            " "
-        } else {
-            ""
-        };
-        write!(w, "&{}{}{}{:?}", region, separator, kind, self.borrowed_place)
+        write!(w, "&{:?} {}{:?}", self.region, kind, self.borrowed_place)
     }
 }
 
@@ -189,7 +184,7 @@ struct GatherBorrows<'a, 'gcx: 'tcx, 'tcx: 'a> {
     idx_vec: IndexVec<BorrowIndex, BorrowData<'tcx>>,
     location_map: FxHashMap<Location, BorrowIndex>,
     activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
-    region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
+    region_map: FxHashMap<RegionVid, FxHashSet<BorrowIndex>>,
     local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
 
     /// When we encounter a 2-phase borrow statement, it will always
@@ -219,6 +214,8 @@ impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
                 return;
             }
 
+            let region = region.to_region_vid();
+
             let borrow = BorrowData {
                 kind,
                 region,
@@ -230,7 +227,7 @@ impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
             let idx = self.idx_vec.push(borrow);
             self.location_map.insert(location, idx);
 
-            self.insert_as_pending_if_two_phase(location, &assigned_place, region, kind, idx);
+            self.insert_as_pending_if_two_phase(location, &assigned_place, kind, idx);
 
             self.region_map.entry(region).or_default().insert(idx);
             if let Some(local) = borrowed_place.root_local() {
@@ -314,7 +311,7 @@ impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
             let borrow_data = &self.idx_vec[borrow_index];
             assert_eq!(borrow_data.reserve_location, location);
             assert_eq!(borrow_data.kind, kind);
-            assert_eq!(borrow_data.region, region);
+            assert_eq!(borrow_data.region, region.to_region_vid());
             assert_eq!(borrow_data.borrowed_place, *place);
         }
 
@@ -347,13 +344,12 @@ impl<'a, 'gcx, 'tcx> GatherBorrows<'a, 'gcx, 'tcx> {
         &mut self,
         start_location: Location,
         assigned_place: &mir::Place<'tcx>,
-        region: Region<'tcx>,
         kind: mir::BorrowKind,
         borrow_index: BorrowIndex,
     ) {
         debug!(
-            "Borrows::insert_as_pending_if_two_phase({:?}, {:?}, {:?}, {:?})",
-            start_location, assigned_place, region, borrow_index,
+            "Borrows::insert_as_pending_if_two_phase({:?}, {:?}, {:?})",
+            start_location, assigned_place, borrow_index,
         );
 
         if !self.allow_two_phase_borrow(kind) {

src/librustc_mir/borrow_check/mod.rs

@@ -14,7 +14,6 @@ use borrow_check::nll::region_infer::RegionInferenceContext;
 use rustc::hir;
 use rustc::hir::Node;
 use rustc::hir::def_id::DefId;
-use rustc::hir::map::definitions::DefPathData;
 use rustc::infer::InferCtxt;
 use rustc::lint::builtin::UNUSED_MUT;
 use rustc::middle::borrowck::SignalledError;
@@ -162,10 +161,6 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
         move_data: move_data,
         param_env: param_env,
     };
-    let body_id = match tcx.def_key(def_id).disambiguated_data.data {
-        DefPathData::StructCtor | DefPathData::EnumVariant(_) => None,
-        _ => Some(tcx.hir.body_owned_by(id)),
-    };
 
     let dead_unwinds = BitSet::new_empty(mir.basic_blocks().len());
     let mut flow_inits = FlowAtLocation::new(do_dataflow(
@@ -212,7 +207,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
         id,
         &attributes,
         &dead_unwinds,
-        Borrows::new(tcx, mir, regioncx.clone(), def_id, body_id, &borrow_set),
+        Borrows::new(tcx, mir, regioncx.clone(), &borrow_set),
         |rs, i| DebugFormatted::new(&rs.location(i)),
     ));
     let flow_uninits = FlowAtLocation::new(do_dataflow(
@@ -592,10 +587,6 @@ impl<'cx, 'gcx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx
                     self.consume_operand(context, (input, span), flow_state);
                 }
             }
-            StatementKind::EndRegion(ref _rgn) => {
-                // ignored when consuming results (update to
-                // flow_state already handled).
-            }
             StatementKind::Nop
             | StatementKind::AscribeUserType(..)
             | StatementKind::Retag { .. }

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

@@ -206,7 +206,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         let mir = self.mir;
         let tcx = self.infcx.tcx;
 
-        let borrow_region_vid = regioncx.to_region_vid(borrow.region);
+        let borrow_region_vid = borrow.region;
         debug!(
             "explain_why_borrow_contains_point: borrow_region_vid={:?}",
             borrow_region_vid

src/librustc_mir/borrow_check/nll/invalidation.rs

@@ -132,8 +132,6 @@ impl<'cx, 'tcx, 'gcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx, 'gcx> {
                     self.consume_operand(context, input);
                 }
             }
-            // EndRegion matters to older NLL/MIR AST borrowck, not to alias NLL
-            StatementKind::EndRegion(..) |
             StatementKind::Nop |
             StatementKind::AscribeUserType(..) |
             StatementKind::Retag { .. } |