compiler/rustc_mir/src/util/storage.rs

   1 use rustc_index::bit_set::BitSet;
   2 use rustc_middle::mir::{self, Local};
   3
   4 /// The set of locals in a MIR body that do not have `StorageLive`/`StorageDead` annotations.
   5 ///
   6 /// These locals have fixed storage for the duration of the body.
   7 //
   8 // FIXME: Currently, we need to traverse the entire MIR to compute this. We should instead store it
   9 // as a field in the `LocalDecl` for each `Local`.
  10 #[derive(Debug, Clone)]
  11 pub struct AlwaysLiveLocals(BitSet<Local>);
  12
  13 impl AlwaysLiveLocals {
  14     pub fn new(body: &mir::Body<'tcx>) -> Self {
  15         let mut always_live_locals = AlwaysLiveLocals(BitSet::new_filled(body.local_decls.len()));
  16
  17         for block in body.basic_blocks() {
  18             for statement in &block.statements {
  19                 use mir::StatementKind::{StorageDead, StorageLive};
  20                 if let StorageLive(l) | StorageDead(l) = statement.kind {
  21                     always_live_locals.0.remove(l);
  22                 }
  23             }
  24         }
  25
  26         always_live_locals
  27     }
  28
  29     pub fn into_inner(self) -> BitSet<Local> {
  30         self.0
  31     }
  32 }
  33
  34 impl std::ops::Deref for AlwaysLiveLocals {
  35     type Target = BitSet<Local>;
  36
  37     #[inline]
  38     fn deref(&self) -> &Self::Target {
  39         &self.0
  40     }
  41 }