Remove AlwaysLiveLocals wrapper struct

It is just a wrapper around a `BitSet` and
doesn't have any functionality of its own.

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -15,7 +15,7 @@ use rustc_middle::ty::layout::{
 use rustc_middle::ty::{
     self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable,
 };
-use rustc_mir_dataflow::storage::AlwaysLiveLocals;
+use rustc_mir_dataflow::storage::always_live_locals;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::Limit;
 use rustc_span::{Pos, Span};
@@ -715,7 +715,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         // Now mark those locals as dead that we do not want to initialize
         // Mark locals that use `Storage*` annotations as dead on function entry.
-        let always_live = AlwaysLiveLocals::new(self.body());
+        let always_live = always_live_locals(self.body());
         for local in locals.indices() {
             if !always_live.contains(local) {
                 locals[local].value = LocalValue::Dead;

compiler/rustc_const_eval/src/transform/validate.rs

@@ -14,7 +14,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt, TypeFoldable};
 use rustc_mir_dataflow::impls::MaybeStorageLive;
-use rustc_mir_dataflow::storage::AlwaysLiveLocals;
+use rustc_mir_dataflow::storage::always_live_locals;
 use rustc_mir_dataflow::{Analysis, ResultsCursor};
 use rustc_target::abi::{Size, VariantIdx};
 
@@ -48,7 +48,7 @@ impl<'tcx> MirPass<'tcx> for Validator {
         let param_env = tcx.param_env(def_id);
         let mir_phase = self.mir_phase;
 
-        let always_live_locals = AlwaysLiveLocals::new(body);
+        let always_live_locals = always_live_locals(body);
         let storage_liveness = MaybeStorageLive::new(always_live_locals)
             .into_engine(tcx, body)
             .iterate_to_fixpoint()

compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs

@@ -1,6 +1,5 @@
 pub use super::*;
 
-use crate::storage::AlwaysLiveLocals;
 use crate::{CallReturnPlaces, GenKill, Results, ResultsRefCursor};
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
@@ -8,11 +7,11 @@ use std::cell::RefCell;
 
 #[derive(Clone)]
 pub struct MaybeStorageLive {
-    always_live_locals: AlwaysLiveLocals,
+    always_live_locals: BitSet<Local>,
 }
 
 impl MaybeStorageLive {
-    pub fn new(always_live_locals: AlwaysLiveLocals) -> Self {
+    pub fn new(always_live_locals: BitSet<Local>) -> Self {
         MaybeStorageLive { always_live_locals }
     }
 }

compiler/rustc_mir_dataflow/src/storage.rs

@@ -7,35 +7,17 @@ use rustc_middle::mir::{self, Local};
 //
 // FIXME: Currently, we need to traverse the entire MIR to compute this. We should instead store it
 // as a field in the `LocalDecl` for each `Local`.
-#[derive(Debug, Clone)]
-pub struct AlwaysLiveLocals(BitSet<Local>);
+pub fn always_live_locals(body: &mir::Body<'_>) -> BitSet<Local> {
+    let mut always_live_locals = BitSet::new_filled(body.local_decls.len());
 
-impl AlwaysLiveLocals {
-    pub fn new(body: &mir::Body<'_>) -> Self {
-        let mut always_live_locals = AlwaysLiveLocals(BitSet::new_filled(body.local_decls.len()));
-
-        for block in body.basic_blocks() {
-            for statement in &block.statements {
-                use mir::StatementKind::{StorageDead, StorageLive};
-                if let StorageLive(l) | StorageDead(l) = statement.kind {
-                    always_live_locals.0.remove(l);
-                }
+    for block in body.basic_blocks() {
+        for statement in &block.statements {
+            use mir::StatementKind::{StorageDead, StorageLive};
+            if let StorageLive(l) | StorageDead(l) = statement.kind {
+                always_live_locals.remove(l);
             }
         }
-
-        always_live_locals
     }
 
-    pub fn into_inner(self) -> BitSet<Local> {
-        self.0
-    }
-}
-
-impl std::ops::Deref for AlwaysLiveLocals {
-    type Target = BitSet<Local>;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
+    always_live_locals
 }

compiler/rustc_mir_transform/src/generator.rs

@@ -228,7 +228,7 @@ struct TransformVisitor<'tcx> {
     suspension_points: Vec<SuspensionPoint<'tcx>>,
 
     // The set of locals that have no `StorageLive`/`StorageDead` annotations.
-    always_live_locals: storage::AlwaysLiveLocals,
+    always_live_locals: BitSet<Local>,
 
     // The original RETURN_PLACE local
     new_ret_local: Local,
@@ -450,7 +450,7 @@ struct LivenessInfo {
 fn locals_live_across_suspend_points<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
-    always_live_locals: &storage::AlwaysLiveLocals,
+    always_live_locals: &BitSet<Local>,
     movable: bool,
 ) -> LivenessInfo {
     let body_ref: &Body<'_> = &body;
@@ -615,7 +615,7 @@ impl ops::Deref for GeneratorSavedLocals {
 fn compute_storage_conflicts<'mir, 'tcx>(
     body: &'mir Body<'tcx>,
     saved_locals: &GeneratorSavedLocals,
-    always_live_locals: storage::AlwaysLiveLocals,
+    always_live_locals: BitSet<Local>,
     requires_storage: rustc_mir_dataflow::Results<'tcx, MaybeRequiresStorage<'mir, 'tcx>>,
 ) -> BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal> {
     assert_eq!(body.local_decls.len(), saved_locals.domain_size());
@@ -625,7 +625,7 @@ fn compute_storage_conflicts<'mir, 'tcx>(
 
     // Locals that are always live or ones that need to be stored across
     // suspension points are not eligible for overlap.
-    let mut ineligible_locals = always_live_locals.into_inner();
+    let mut ineligible_locals = always_live_locals;
     ineligible_locals.intersect(&**saved_locals);
 
     // Compute the storage conflicts for all eligible locals.
@@ -1300,7 +1300,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
             },
         );
 
-        let always_live_locals = storage::AlwaysLiveLocals::new(&body);
+        let always_live_locals = storage::always_live_locals(&body);
 
         let liveness_info =
             locals_live_across_suspend_points(tcx, body, &always_live_locals, movable);