diff options
| -rw-r--r-- | src/librustc_mir/transform/const_prop.rs | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs index 58a8d5eeb1e..271c746aa0f 100644 --- a/src/librustc_mir/transform/const_prop.rs +++ b/src/librustc_mir/transform/const_prop.rs @@ -8,6 +8,7 @@ use rustc_ast::ast::Mutability; use rustc_data_structures::fx::FxHashMap; use rustc_hir::def::DefKind; use rustc_hir::HirId; +use rustc_index::bit_set::BitSet; use rustc_index::vec::IndexVec; use rustc_middle::mir::interpret::{InterpResult, Scalar}; use rustc_middle::mir::visit::{ @@ -775,7 +776,7 @@ enum ConstPropMode { struct CanConstProp { can_const_prop: IndexVec<Local, ConstPropMode>, // false at the beginning, once set, there are not allowed to be any more assignments - found_assignment: IndexVec<Local, bool>, + found_assignment: BitSet<Local>, } impl CanConstProp { @@ -783,7 +784,7 @@ impl CanConstProp { fn check(body: &Body<'_>) -> IndexVec<Local, ConstPropMode> { let mut cpv = CanConstProp { can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls), - found_assignment: IndexVec::from_elem(false, &body.local_decls), + found_assignment: BitSet::new_empty(body.local_decls.len()), }; for (local, val) in cpv.can_const_prop.iter_enumerated_mut() { // cannot use args at all @@ -811,11 +812,9 @@ impl<'tcx> Visitor<'tcx> for CanConstProp { // FIXME(oli-obk): we could be more powerful here, if the multiple writes // only occur in independent execution paths MutatingUse(MutatingUseContext::Store) => { - if self.found_assignment[local] { + if !self.found_assignment.insert(local) { trace!("local {:?} can't be propagated because of multiple assignments", local); self.can_const_prop[local] = ConstPropMode::NoPropagation; - } else { - self.found_assignment[local] = true } } // Reading constants is allowed an arbitrary number of times |