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Rollup merge of #55271 - sinkuu:traversal_iter, r=matthewjasper

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Unimplement ExactSizeIterator for MIR traversing iterators

If `root` is not `START_BLOCK`, `basic_blocks().len() - visited` does not represent their exact size.
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kennytm 2018-10-26 18:25:02 +08:00
commit 9111fab74d
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1 changed files with 24 additions and 12 deletions
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36
src/librustc/mir/traversal.rs
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@ -34,6 +34,7 @@ pub struct Preorder<'a, 'tcx: 'a> {
mir: &'a Mir<'tcx>,
visited: BitSet<BasicBlock>,
worklist: Vec<BasicBlock>,
root_is_start_block: bool,
}
impl<'a, 'tcx> Preorder<'a, 'tcx> {
@ -44,6 +45,7 @@ impl<'a, 'tcx> Preorder<'a, 'tcx> {
mir,
visited: BitSet::new_empty(mir.basic_blocks().len()),
worklist,
root_is_start_block: root == START_BLOCK,
}
}
}
@ -75,15 +77,19 @@ impl<'a, 'tcx> Iterator for Preorder<'a, 'tcx> {
fn size_hint(&self) -> (usize, Option<usize>) {
// All the blocks, minus the number of blocks we've visited.
let remaining = self.mir.basic_blocks().len() - self.visited.count();
let upper = self.mir.basic_blocks().len() - self.visited.count();
// We will visit all remaining blocks exactly once.
(remaining, Some(remaining))
let lower = if self.root_is_start_block {
// We will visit all remaining blocks exactly once.
upper
} else {
self.worklist.len()
};
(lower, Some(upper))
}
}
impl<'a, 'tcx> ExactSizeIterator for Preorder<'a, 'tcx> {}
/// Postorder traversal of a graph.
///
/// Postorder traversal is when each node is visited after all of it's
@ -105,7 +111,8 @@ impl<'a, 'tcx> ExactSizeIterator for Preorder<'a, 'tcx> {}
pub struct Postorder<'a, 'tcx: 'a> {
mir: &'a Mir<'tcx>,
visited: BitSet<BasicBlock>,
visit_stack: Vec<(BasicBlock, Successors<'a>)>
visit_stack: Vec<(BasicBlock, Successors<'a>)>,
root_is_start_block: bool,
}
impl<'a, 'tcx> Postorder<'a, 'tcx> {
@ -113,7 +120,8 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> {
let mut po = Postorder {
mir,
visited: BitSet::new_empty(mir.basic_blocks().len()),
visit_stack: Vec::new()
visit_stack: Vec::new(),
root_is_start_block: root == START_BLOCK,
};
@ -214,15 +222,19 @@ impl<'a, 'tcx> Iterator for Postorder<'a, 'tcx> {
fn size_hint(&self) -> (usize, Option<usize>) {
// All the blocks, minus the number of blocks we've visited.
let remaining = self.mir.basic_blocks().len() - self.visited.count();
let upper = self.mir.basic_blocks().len() - self.visited.count();
// We will visit all remaining blocks exactly once.
(remaining, Some(remaining))
let lower = if self.root_is_start_block {
// We will visit all remaining blocks exactly once.
upper
} else {
self.visit_stack.len()
};
(lower, Some(upper))
}
}
impl<'a, 'tcx> ExactSizeIterator for Postorder<'a, 'tcx> {}
/// Reverse postorder traversal of a graph
///
/// Reverse postorder is the reverse order of a postorder traversal.