Auto merge of #70449 - ecstatic-morse:visit-body, r=oli-obk

Make `Visitor::visit_body` take a plain `&Body`

`ReadOnlyBodyAndCache` has replaced `&Body` in many parts of the code base that don't care about basic block predecessors. This includes the MIR `Visitor` trait, which I suspect resulted in many unnecessary changes in #64736. This reverts part of that PR to reduce the number of places where we need to pass a `ReadOnlyBodyAndCache`.

In the long term, we should either give `ReadOnlyBodyAndCache` more ergonomic name and replace all uses of `&mir::Body` with it at the cost of carrying an extra pointer everywhere, or use it only in places that actually need access to the predecessor cache. Perhaps there is an even nicer alternative.

r? @Nashenas88

21 files changed, 33 insertions, 34 deletions

diff --git a/src/librustc/mir/visit.rs b/src/librustc/mir/visit.rs
index c1b27b40f7d..400d15cdc14 100644
--- a/src/librustc/mir/visit.rs
+++ b/src/librustc/mir/visit.rs
@@ -65,12 +65,12 @@ use rustc_span::Span;
 // variant argument) that does not require visiting, as in
 // `is_cleanup` above.
 
-macro_rules! body_cache_type {
-    (mut $a:lifetime, $tcx:lifetime) => {
+macro_rules! body_type {
+    (mut $tcx:lifetime) => {
         &mut BodyAndCache<$tcx>
     };
-    ($a:lifetime, $tcx:lifetime) => {
-        ReadOnlyBodyAndCache<$a, $tcx>
+    ($tcx:lifetime) => {
+        &Body<$tcx>
     };
 }
 
@@ -82,7 +82,7 @@ macro_rules! make_mir_visitor {
 
             fn visit_body(
                 &mut self,
-                body: body_cache_type!($($mutability)? '_, 'tcx)
+                body: body_type!($($mutability)? 'tcx)
             ) {
                 self.super_body(body);
             }
@@ -254,7 +254,7 @@ macro_rules! make_mir_visitor {
 
             fn super_body(
                 &mut self,
-                $($mutability)? body: body_cache_type!($($mutability)? '_, 'tcx)
+                $($mutability)? body: body_type!($($mutability)? 'tcx)
             ) {
                 let span = body.span;
                 if let Some(yield_ty) = &$($mutability)? body.yield_ty {
@@ -819,7 +819,7 @@ macro_rules! make_mir_visitor {
 
             fn visit_location(
                 &mut self,
-                body: body_cache_type!($($mutability)? '_, 'tcx),
+                body: body_type!($($mutability)? 'tcx),
                 location: Location
             ) {
                 let basic_block = & $($mutability)? body[location.block];
diff --git a/src/librustc_codegen_ssa/mir/analyze.rs b/src/librustc_codegen_ssa/mir/analyze.rs
index 04680a17517..5cbeea82512 100644
--- a/src/librustc_codegen_ssa/mir/analyze.rs
+++ b/src/librustc_codegen_ssa/mir/analyze.rs
@@ -20,7 +20,7 @@ pub fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     let mir = fx.mir;
     let mut analyzer = LocalAnalyzer::new(fx);
 
-    analyzer.visit_body(mir);
+    analyzer.visit_body(&mir);
 
     for (local, decl) in mir.local_decls.iter_enumerated() {
         let ty = fx.monomorphize(&decl.ty);
diff --git a/src/librustc_mir/borrow_check/borrow_set.rs b/src/librustc_mir/borrow_check/borrow_set.rs
index 9f4f0ce5620..919d3f2ab32 100644
--- a/src/librustc_mir/borrow_check/borrow_set.rs
+++ b/src/librustc_mir/borrow_check/borrow_set.rs
@@ -107,7 +107,7 @@ impl LocalsStateAtExit {
             LocalsStateAtExit::AllAreInvalidated
         } else {
             let mut has_storage_dead = HasStorageDead(BitSet::new_empty(body.local_decls.len()));
-            has_storage_dead.visit_body(body);
+            has_storage_dead.visit_body(&body);
             let mut has_storage_dead_or_moved = has_storage_dead.0;
             for move_out in &move_data.moves {
                 if let Some(index) = move_data.base_local(move_out.path) {
diff --git a/src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs b/src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs
index 4ab7c4506fe..083b24e12a5 100644
--- a/src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs
+++ b/src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs
@@ -1559,7 +1559,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
         }
         let mut visitor = FakeReadCauseFinder { place, cause: None };
-        visitor.visit_body(self.body);
+        visitor.visit_body(&self.body);
         match visitor.cause {
             Some(FakeReadCause::ForMatchGuard) => Some("match guard"),
             Some(FakeReadCause::ForIndex) => Some("indexing expression"),
diff --git a/src/librustc_mir/borrow_check/invalidation.rs b/src/librustc_mir/borrow_check/invalidation.rs
index 3d1768cf0e5..653578cc156 100644
--- a/src/librustc_mir/borrow_check/invalidation.rs
+++ b/src/librustc_mir/borrow_check/invalidation.rs
@@ -37,7 +37,7 @@ pub(super) fn generate_invalidates<'tcx>(
             body: &body,
             dominators,
         };
-        ig.visit_body(body);
+        ig.visit_body(&body);
     }
 }
 
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index e3dc9e0f105..b6c3ae0fb87 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -299,8 +299,8 @@ fn do_mir_borrowck<'a, 'tcx>(
     }
 
     dataflow::visit_results(
-        &*body,
-        traversal::reverse_postorder(&*body).map(|(bb, _)| bb),
+        &body,
+        traversal::reverse_postorder(&body).map(|(bb, _)| bb),
         &results,
         &mut mbcx,
     );
diff --git a/src/librustc_mir/borrow_check/type_check/liveness/local_use_map.rs b/src/librustc_mir/borrow_check/type_check/liveness/local_use_map.rs
index 8155aa0ee00..9a4eeb8ffc4 100644
--- a/src/librustc_mir/borrow_check/type_check/liveness/local_use_map.rs
+++ b/src/librustc_mir/borrow_check/type_check/liveness/local_use_map.rs
@@ -81,7 +81,7 @@ impl LocalUseMap {
         live_locals.iter().for_each(|&local| locals_with_use_data[local] = true);
 
         LocalUseMapBuild { local_use_map: &mut local_use_map, elements, locals_with_use_data }
-            .visit_body(body);
+            .visit_body(&body);
 
         local_use_map
     }
diff --git a/src/librustc_mir/borrow_check/type_check/liveness/polonius.rs b/src/librustc_mir/borrow_check/type_check/liveness/polonius.rs
index 407e0628b6e..9bb1bbeaf00 100644
--- a/src/librustc_mir/borrow_check/type_check/liveness/polonius.rs
+++ b/src/librustc_mir/borrow_check/type_check/liveness/polonius.rs
@@ -101,7 +101,7 @@ pub(super) fn populate_access_facts(
             location_table,
             move_data,
         };
-        extractor.visit_body(body);
+        extractor.visit_body(&body);
 
         facts.var_dropped_at.extend(
             dropped_at.iter().map(|&(local, location)| (local, location_table.mid_index(location))),
diff --git a/src/librustc_mir/borrow_check/type_check/mod.rs b/src/librustc_mir/borrow_check/type_check/mod.rs
index 54ca0c6a260..b8dd1010b4c 100644
--- a/src/librustc_mir/borrow_check/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/type_check/mod.rs
@@ -210,7 +210,7 @@ fn type_check_internal<'a, 'tcx, R>(
     );
     let errors_reported = {
         let mut verifier = TypeVerifier::new(&mut checker, *body, promoted);
-        verifier.visit_body(body);
+        verifier.visit_body(&body);
         verifier.errors_reported
     };
 
@@ -435,7 +435,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
         }
     }
 
-    fn visit_body(&mut self, body: ReadOnlyBodyAndCache<'_, 'tcx>) {
+    fn visit_body(&mut self, body: &Body<'tcx>) {
         self.sanitize_type(&"return type", body.return_ty());
         for local_decl in &body.local_decls {
             self.sanitize_type(local_decl, local_decl.ty);
@@ -563,7 +563,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
 
         swap_constraints(self);
 
-        self.visit_body(promoted_body);
+        self.visit_body(&promoted_body);
 
         if !self.errors_reported {
             // if verifier failed, don't do further checks to avoid ICEs
diff --git a/src/librustc_mir/borrow_check/used_muts.rs b/src/librustc_mir/borrow_check/used_muts.rs
index 5e4eebb771f..7fbf8842860 100644
--- a/src/librustc_mir/borrow_check/used_muts.rs
+++ b/src/librustc_mir/borrow_check/used_muts.rs
@@ -32,7 +32,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 never_initialized_mut_locals: &mut never_initialized_mut_locals,
                 mbcx: self,
             };
-            visitor.visit_body(visitor.mbcx.body);
+            visitor.visit_body(&visitor.mbcx.body);
         }
 
         // Take the union of the existed `used_mut` set with those variables we've found were
diff --git a/src/librustc_mir/const_eval/eval_queries.rs b/src/librustc_mir/const_eval/eval_queries.rs
index ffbff00cf37..b0ef539d96b 100644
--- a/src/librustc_mir/const_eval/eval_queries.rs
+++ b/src/librustc_mir/const_eval/eval_queries.rs
@@ -307,7 +307,7 @@ pub fn const_eval_raw_provider<'tcx>(
     );
 
     let res = ecx.load_mir(cid.instance.def, cid.promoted);
-    res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, *body))
+    res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, &body))
         .and_then(|place| {
             Ok(RawConst { alloc_id: place.ptr.assert_ptr().alloc_id, ty: place.layout.ty })
         })
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 67d024e62d9..1d18279938b 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -83,7 +83,7 @@ impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     ) -> Self {
         MaybeRequiresStorage {
             body,
-            borrowed_locals: RefCell::new(ResultsRefCursor::new(*body, borrowed_locals)),
+            borrowed_locals: RefCell::new(ResultsRefCursor::new(&body, borrowed_locals)),
         }
     }
 }
@@ -250,7 +250,7 @@ impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     /// Kill locals that are fully moved and have not been borrowed.
     fn check_for_move(&self, trans: &mut impl GenKill<Local>, loc: Location) {
         let mut visitor = MoveVisitor { trans, borrowed_locals: &self.borrowed_locals };
-        visitor.visit_location(self.body, loc);
+        visitor.visit_location(&self.body, loc);
     }
 }
 
diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
index cbd19f080eb..e42cff02699 100644
--- a/src/librustc_mir/monomorphize/collector.rs
+++ b/src/librustc_mir/monomorphize/collector.rs
@@ -1162,7 +1162,7 @@ fn collect_neighbours<'tcx>(
     debug!("collect_neighbours: {:?}", instance.def_id());
     let body = tcx.instance_mir(instance.def);
 
-    MirNeighborCollector { tcx, body: &body, output, instance }.visit_body(body);
+    MirNeighborCollector { tcx, body: &body, output, instance }.visit_body(&body);
 }
 
 fn def_id_to_string(tcx: TyCtxt<'_>, def_id: DefId) -> String {
diff --git a/src/librustc_mir/transform/check_consts/validation.rs b/src/librustc_mir/transform/check_consts/validation.rs
index c315a8a65df..99c3437bf69 100644
--- a/src/librustc_mir/transform/check_consts/validation.rs
+++ b/src/librustc_mir/transform/check_consts/validation.rs
@@ -183,7 +183,7 @@ impl Validator<'a, 'mir, 'tcx> {
             self.check_op_spanned(ops::Loop, body.span);
         }
 
-        self.visit_body(body);
+        self.visit_body(&body);
 
         // Ensure that the end result is `Sync` in a non-thread local `static`.
         let should_check_for_sync =
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index d241cc5d8a3..546361d62f4 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -507,7 +507,7 @@ fn unsafety_check_result(tcx: TyCtxt<'_>, def_id: DefId) -> UnsafetyCheckResult
     // mir_built ensures that body has a computed cache, so we don't (and can't) attempt to
     // recompute it here.
     let body = body.unwrap_read_only();
-    checker.visit_body(body);
+    checker.visit_body(&body);
 
     check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
     UnsafetyCheckResult {
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 927deebb175..2a8b034d35b 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -778,7 +778,7 @@ impl CanConstProp {
                 trace!("local {:?} can't be const propagated because it's not a temporary", local);
             }
         }
-        cpv.visit_body(body);
+        cpv.visit_body(&body);
         cpv.can_const_prop
     }
 }
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
index 1945efb6bf7..030df37827f 100644
--- a/src/librustc_mir/transform/generator.rs
+++ b/src/librustc_mir/transform/generator.rs
@@ -469,7 +469,7 @@ fn locals_live_across_suspend_points(
     // Find the MIR locals which do not use StorageLive/StorageDead statements.
     // The storage of these locals are always live.
     let mut ignored = StorageIgnored(BitSet::new_filled(body.local_decls.len()));
-    ignored.visit_body(body);
+    ignored.visit_body(&body);
 
     // Calculate the MIR locals which have been previously
     // borrowed (even if they are still active).
diff --git a/src/librustc_mir/transform/instcombine.rs b/src/librustc_mir/transform/instcombine.rs
index 48b4d00a2e9..bb556f40387 100644
--- a/src/librustc_mir/transform/instcombine.rs
+++ b/src/librustc_mir/transform/instcombine.rs
@@ -26,7 +26,7 @@ impl<'tcx> MirPass<'tcx> for InstCombine {
         let optimizations = {
             let read_only_cache = read_only!(body);
             let mut optimization_finder = OptimizationFinder::new(body, tcx);
-            optimization_finder.visit_body(read_only_cache);
+            optimization_finder.visit_body(&read_only_cache);
             optimization_finder.optimizations
         };
 
diff --git a/src/librustc_mir/transform/simplify.rs b/src/librustc_mir/transform/simplify.rs
index 4c54a46642f..55ea1e40e08 100644
--- a/src/librustc_mir/transform/simplify.rs
+++ b/src/librustc_mir/transform/simplify.rs
@@ -309,7 +309,7 @@ impl<'tcx> MirPass<'tcx> for SimplifyLocals {
         let locals = {
             let read_only_cache = read_only!(body);
             let mut marker = DeclMarker { locals: BitSet::new_empty(body.local_decls.len()), body };
-            marker.visit_body(read_only_cache);
+            marker.visit_body(&read_only_cache);
             // Return pointer and arguments are always live
             marker.locals.insert(RETURN_PLACE);
             for arg in body.args_iter() {
diff --git a/src/librustc_mir/util/collect_writes.rs b/src/librustc_mir/util/collect_writes.rs
index 6cd21316496..fc9dbd73f32 100644
--- a/src/librustc_mir/util/collect_writes.rs
+++ b/src/librustc_mir/util/collect_writes.rs
@@ -1,7 +1,6 @@
 use rustc::mir::visit::PlaceContext;
 use rustc::mir::visit::Visitor;
-use rustc::mir::ReadOnlyBodyAndCache;
-use rustc::mir::{Local, Location};
+use rustc::mir::{Body, Local, Location};
 
 crate trait FindAssignments {
     // Finds all statements that assign directly to local (i.e., X = ...)
@@ -9,10 +8,10 @@ crate trait FindAssignments {
     fn find_assignments(&self, local: Local) -> Vec<Location>;
 }
 
-impl<'a, 'tcx> FindAssignments for ReadOnlyBodyAndCache<'a, 'tcx> {
+impl<'tcx> FindAssignments for Body<'tcx> {
     fn find_assignments(&self, local: Local) -> Vec<Location> {
         let mut visitor = FindLocalAssignmentVisitor { needle: local, locations: vec![] };
-        visitor.visit_body(*self);
+        visitor.visit_body(self);
         visitor.locations
     }
 }
diff --git a/src/librustc_mir/util/def_use.rs b/src/librustc_mir/util/def_use.rs
index aa9ddbdbda9..059cea86a4d 100644
--- a/src/librustc_mir/util/def_use.rs
+++ b/src/librustc_mir/util/def_use.rs
@@ -38,7 +38,7 @@ impl DefUseAnalysis {
             var_debug_info_index: 0,
             in_var_debug_info: false,
         };
-        finder.visit_body(body);
+        finder.visit_body(&body);
         self.info = finder.info
     }