1 files changed, 20 insertions, 0 deletions
diff --git a/compiler/rustc_mir_dataflow/src/storage.rs b/compiler/rustc_mir_dataflow/src/storage.rs
new file mode 100644
index 000000000..c909648ea
--- /dev/null
+++ b/compiler/rustc_mir_dataflow/src/storage.rs
@@ -0,0 +1,20 @@
+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
+}