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use super::ControlFlowGraph;
use super::iterate::reverse_post_order;
use super::super::indexed_vec::{IndexVec, Idx};
use std::fmt;
#[cfg(test)]
mod test;
pub fn dominators<G: ControlFlowGraph>(graph: &G) -> Dominators<G::Node> {
let start_node = graph.start_node();
let rpo = reverse_post_order(graph, start_node);
dominators_given_rpo(graph, &rpo)
}
pub fn dominators_given_rpo<G: ControlFlowGraph>(graph: &G,
rpo: &[G::Node])
-> Dominators<G::Node> {
let start_node = graph.start_node();
assert_eq!(rpo[0], start_node);
let mut post_order_rank: IndexVec<G::Node, usize> = IndexVec::from_elem_n(usize::default(),
graph.num_nodes());
for (index, node) in rpo.iter().rev().cloned().enumerate() {
post_order_rank[node] = index;
}
let mut immediate_dominators: IndexVec<G::Node, Option<G::Node>> =
IndexVec::from_elem_n(Option::default(), graph.num_nodes());
immediate_dominators[start_node] = Some(start_node);
let mut changed = true;
while changed {
changed = false;
for &node in &rpo[1..] {
let mut new_idom = None;
for pred in graph.predecessors(node) {
if immediate_dominators[pred].is_some() {
new_idom = intersect_opt(&post_order_rank,
&immediate_dominators,
new_idom,
Some(pred));
}
}
if new_idom != immediate_dominators[node] {
immediate_dominators[node] = new_idom;
changed = true;
}
}
}
Dominators {
post_order_rank: post_order_rank,
immediate_dominators: immediate_dominators,
}
}
fn intersect_opt<Node: Idx>(post_order_rank: &IndexVec<Node, usize>,
immediate_dominators: &IndexVec<Node, Option<Node>>,
node1: Option<Node>,
node2: Option<Node>)
-> Option<Node> {
match (node1, node2) {
(None, None) => None,
(Some(n), None) | (None, Some(n)) => Some(n),
(Some(n1), Some(n2)) => Some(intersect(post_order_rank, immediate_dominators, n1, n2)),
}
}
fn intersect<Node: Idx>(post_order_rank: &IndexVec<Node, usize>,
immediate_dominators: &IndexVec<Node, Option<Node>>,
mut node1: Node,
mut node2: Node)
-> Node {
while node1 != node2 {
while post_order_rank[node1] < post_order_rank[node2] {
node1 = immediate_dominators[node1].unwrap();
}
while post_order_rank[node2] < post_order_rank[node1] {
node2 = immediate_dominators[node2].unwrap();
}
}
return node1;
}
#[derive(Clone, Debug)]
pub struct Dominators<N: Idx> {
post_order_rank: IndexVec<N, usize>,
immediate_dominators: IndexVec<N, Option<N>>,
}
impl<Node: Idx> Dominators<Node> {
pub fn is_reachable(&self, node: Node) -> bool {
self.immediate_dominators[node].is_some()
}
pub fn immediate_dominator(&self, node: Node) -> Node {
assert!(self.is_reachable(node), "node {:?} is not reachable", node);
self.immediate_dominators[node].unwrap()
}
pub fn dominators(&self, node: Node) -> Iter<Node> {
assert!(self.is_reachable(node), "node {:?} is not reachable", node);
Iter {
dominators: self,
node: Some(node),
}
}
pub fn is_dominated_by(&self, node: Node, dom: Node) -> bool {
self.dominators(node).any(|n| n == dom)
}
pub fn mutual_dominator_node(&self, node1: Node, node2: Node) -> Node {
assert!(self.is_reachable(node1),
"node {:?} is not reachable",
node1);
assert!(self.is_reachable(node2),
"node {:?} is not reachable",
node2);
intersect::<Node>(&self.post_order_rank,
&self.immediate_dominators,
node1,
node2)
}
pub fn mutual_dominator<I>(&self, iter: I) -> Option<Node>
where I: IntoIterator<Item = Node>
{
let mut iter = iter.into_iter();
iter.next()
.map(|dom| iter.fold(dom, |dom, node| self.mutual_dominator_node(dom, node)))
}
pub fn all_immediate_dominators(&self) -> &IndexVec<Node, Option<Node>> {
&self.immediate_dominators
}
pub fn dominator_tree(&self) -> DominatorTree<Node> {
let elem: Vec<Node> = Vec::new();
let mut children: IndexVec<Node, Vec<Node>> =
IndexVec::from_elem_n(elem, self.immediate_dominators.len());
let mut root = None;
for (index, immed_dom) in self.immediate_dominators.iter().enumerate() {
let node = Node::new(index);
match *immed_dom {
None => {
}
Some(immed_dom) => {
if node == immed_dom {
root = Some(node);
} else {
children[immed_dom].push(node);
}
}
}
}
DominatorTree {
root: root.unwrap(),
children: children,
}
}
}
pub struct Iter<'dom, Node: Idx + 'dom> {
dominators: &'dom Dominators<Node>,
node: Option<Node>,
}
impl<'dom, Node: Idx> Iterator for Iter<'dom, Node> {
type Item = Node;
fn next(&mut self) -> Option<Self::Item> {
if let Some(node) = self.node {
let dom = self.dominators.immediate_dominator(node);
if dom == node {
self.node = None;
} else {
self.node = Some(dom);
}
return Some(node);
} else {
return None;
}
}
}
pub struct DominatorTree<N: Idx> {
root: N,
children: IndexVec<N, Vec<N>>,
}
impl<Node: Idx> DominatorTree<Node> {
pub fn root(&self) -> Node {
self.root
}
pub fn children(&self, node: Node) -> &[Node] {
&self.children[node]
}
pub fn iter_children_of(&self, node: Node) -> IterChildrenOf<Node> {
IterChildrenOf {
tree: self,
stack: vec![node],
}
}
}
pub struct IterChildrenOf<'iter, Node: Idx + 'iter> {
tree: &'iter DominatorTree<Node>,
stack: Vec<Node>,
}
impl<'iter, Node: Idx> Iterator for IterChildrenOf<'iter, Node> {
type Item = Node;
fn next(&mut self) -> Option<Node> {
if let Some(node) = self.stack.pop() {
self.stack.extend(self.tree.children(node));
Some(node)
} else {
None
}
}
}
impl<Node: Idx> fmt::Debug for DominatorTree<Node> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
fmt::Debug::fmt(&DominatorTreeNode {
tree: self,
node: self.root,
},
fmt)
}
}
struct DominatorTreeNode<'tree, Node: Idx> {
tree: &'tree DominatorTree<Node>,
node: Node,
}
impl<'tree, Node: Idx> fmt::Debug for DominatorTreeNode<'tree, Node> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
let subtrees: Vec<_> = self.tree
.children(self.node)
.iter()
.map(|&child| {
DominatorTreeNode {
tree: self.tree,
node: child,
}
})
.collect();
fmt.debug_tuple("")
.field(&self.node)
.field(&subtrees)
.finish()
}
}