Rollup merge of #133475 - nnethercote:MaybeStorage-improvements, r=lcnr

`MaybeStorage` improvements

Minor dataflow improvements.

r? `@tmiasko`

compiler/rustc_mir_dataflow/src/impls/mod.rs

@@ -14,4 +14,6 @@ pub use self::initialized::{
 pub use self::liveness::{
     MaybeLiveLocals, MaybeTransitiveLiveLocals, TransferFunction as LivenessTransferFunction,
 };
-pub use self::storage_liveness::{MaybeRequiresStorage, MaybeStorageDead, MaybeStorageLive};
+pub use self::storage_liveness::{
+    MaybeRequiresStorage, MaybeStorageDead, MaybeStorageLive, always_storage_live_locals,
+};

compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs

@@ -7,6 +7,23 @@ use rustc_middle::mir::*;
 use super::MaybeBorrowedLocals;
 use crate::{Analysis, GenKill, ResultsCursor};
 
+/// The set of locals in a MIR body that do not have `StorageLive`/`StorageDead` annotations.
+///
+/// These locals have fixed storage for the duration of the body.
+pub fn always_storage_live_locals(body: &Body<'_>) -> BitSet<Local> {
+    let mut always_live_locals = BitSet::new_filled(body.local_decls.len());
+
+    for block in &*body.basic_blocks {
+        for statement in &block.statements {
+            if let StatementKind::StorageLive(l) | StatementKind::StorageDead(l) = statement.kind {
+                always_live_locals.remove(l);
+            }
+        }
+    }
+
+    always_live_locals
+}
+
 pub struct MaybeStorageLive<'a> {
     always_live_locals: Cow<'a, BitSet<Local>>,
 }
@@ -28,10 +45,7 @@ impl<'a, 'tcx> Analysis<'tcx> for MaybeStorageLive<'a> {
     }
 
     fn initialize_start_block(&self, body: &Body<'tcx>, on_entry: &mut Self::Domain) {
-        assert_eq!(body.local_decls.len(), self.always_live_locals.domain_size());
-        for local in self.always_live_locals.iter() {
-            on_entry.insert(local);
-        }
+        on_entry.union(&*self.always_live_locals);
 
         for arg in body.args_iter() {
             on_entry.insert(arg);

compiler/rustc_mir_dataflow/src/lib.rs

@@ -25,7 +25,7 @@ pub use self::framework::{
 use self::move_paths::MoveData;
 
 pub mod debuginfo;
-pub mod drop_flag_effects;
+mod drop_flag_effects;
 pub mod elaborate_drops;
 mod errors;
 mod framework;
@@ -33,8 +33,7 @@ pub mod impls;
 pub mod move_paths;
 pub mod points;
 pub mod rustc_peek;
-pub mod storage;
-pub mod un_derefer;
+mod un_derefer;
 pub mod value_analysis;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }

compiler/rustc_mir_dataflow/src/storage.rs

@@ -1,20 +0,0 @@
-use rustc_index::bit_set::BitSet;
-use rustc_middle::mir::{self, Local};
-
-/// The set of locals in a MIR body that do not have `StorageLive`/`StorageDead` annotations.
-///
-/// These locals have fixed storage for the duration of the body.
-pub fn always_storage_live_locals(body: &mir::Body<'_>) -> BitSet<Local> {
-    let mut always_live_locals = 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.remove(l);
-            }
-        }
-    }
-
-    always_live_locals
-}