diff options
| -rw-r--r-- | compiler/rustc_middle/src/mir/traversal.rs | 17 |
1 files changed, 6 insertions, 11 deletions
diff --git a/compiler/rustc_middle/src/mir/traversal.rs b/compiler/rustc_middle/src/mir/traversal.rs index 5950ac295af..5fb3c648d5a 100644 --- a/compiler/rustc_middle/src/mir/traversal.rs +++ b/compiler/rustc_middle/src/mir/traversal.rs @@ -108,7 +108,6 @@ pub struct Postorder<'a, 'tcx> { basic_blocks: &'a IndexSlice<BasicBlock, BasicBlockData<'tcx>>, visited: DenseBitSet<BasicBlock>, visit_stack: Vec<(BasicBlock, Successors<'a>)>, - root_is_start_block: bool, /// A non-empty `extra` allows for a precise calculation of the successors. extra: Option<(TyCtxt<'tcx>, Instance<'tcx>)>, } @@ -123,7 +122,6 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> { basic_blocks, visited: DenseBitSet::new_empty(basic_blocks.len()), visit_stack: Vec::new(), - root_is_start_block: root == START_BLOCK, extra, }; @@ -211,16 +209,13 @@ impl<'tcx> Iterator for Postorder<'_, 'tcx> { } fn size_hint(&self) -> (usize, Option<usize>) { - // All the blocks, minus the number of blocks we've visited. - let upper = self.basic_blocks.len() - self.visited.count(); - - let lower = if self.root_is_start_block { - // We will visit all remaining blocks exactly once. - upper - } else { - self.visit_stack.len() - }; + // These bounds are not at all tight, but that's fine. + // It's not worth a popcnt loop in `DenseBitSet` to improve the upper, + // and in mono-reachable we can't be precise anyway. + // Leaning on amortized growth is fine. + let lower = self.visit_stack.len(); + let upper = self.basic_blocks.len(); (lower, Some(upper)) } } |