Redefine NodeIndex as a newtype_index!.
This commit removes the custom index implementation of `NodeIndex`, which probably predates `newtype_index!`. As well as eliminating code, it improves the debugging experience, because the custom implementation had the property of being incremented by 1 (so it could use `NonZeroU32`), which was incredibly confusing if you didn't expect it. For some reason, I also had to remove an `unsafe` block marker from `from_u32_unchecked()` that the compiler said was now unnecessary.
This commit is contained in:
Nicholas Nethercote
parent
04b1111ae8
commit
43c0d2ce8e
4 changed files with 35 additions and 42 deletions
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@ -149,7 +149,7 @@ macro_rules! newtype_index {
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#[inline]
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$v const unsafe fn from_u32_unchecked(value: u32) -> Self {
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unsafe { $type { private: value } }
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$type { private: value }
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}
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/// Extracts the value of this index as an integer.
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@ -74,9 +74,9 @@ impl<'a, O: ForestObligation + 'a> dot::GraphWalk<'a> for &'a ObligationForest<O
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.flat_map(|i| {
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let node = &self.nodes[i];
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node.parent.iter().map(|p| p.get())
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.chain(node.dependents.iter().map(|p| p.get()))
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.map(move |p| (p, i))
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node.parent.iter()
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.chain(node.dependents.iter())
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.map(move |p| (p.index(), i))
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})
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.collect()
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}
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@ -81,6 +81,8 @@
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//! nodes, which aren't needed anymore.
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use crate::fx::{FxHashMap, FxHashSet};
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use crate::indexed_vec::Idx;
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use crate::newtype_index;
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use std::cell::Cell;
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use std::collections::hash_map::Entry;
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@ -88,14 +90,15 @@ use std::fmt::Debug;
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use std::hash;
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use std::marker::PhantomData;
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mod node_index;
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use self::node_index::NodeIndex;
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mod graphviz;
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#[cfg(test)]
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mod tests;
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newtype_index! {
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pub struct NodeIndex { .. }
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}
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pub trait ForestObligation : Clone + Debug {
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type Predicate : Clone + hash::Hash + Eq + Debug;
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@ -151,6 +154,10 @@ pub struct ObligationForest<O: ForestObligation> {
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/// At all times we maintain the invariant that every node appears
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/// at a higher index than its parent. This is needed by the
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/// backtrace iterator (which uses `split_at`).
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///
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/// Ideally, this would be an `IndexVec<NodeIndex, Node<O>>`. But that is
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/// slower, because this vector is accessed so often that the
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/// `u32`-to-`usize` conversions required for accesses are significant.
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nodes: Vec<Node<O>>,
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/// A cache of predicates that have been successfully completed.
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@ -178,13 +185,19 @@ struct Node<O> {
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obligation: O,
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state: Cell<NodeState>,
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/// The parent of a node - the original obligation of
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/// which it is a subobligation. Except for error reporting,
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/// it is just like any member of `dependents`.
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/// The parent of a node - the original obligation of which it is a
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/// subobligation. Except for error reporting, it is just like any member
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/// of `dependents`.
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///
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/// Unlike `ObligationForest::nodes`, this uses `NodeIndex` rather than
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/// `usize` for the index, because keeping the size down is more important
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/// than the cost of converting to a `usize` for indexing.
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parent: Option<NodeIndex>,
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/// Obligations that depend on this obligation for their
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/// completion. They must all be in a non-pending state.
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/// Obligations that depend on this obligation for their completion. They
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/// must all be in a non-pending state.
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///
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/// This uses `NodeIndex` for the same reason as `parent`.
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dependents: Vec<NodeIndex>,
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/// Identifier of the obligation tree to which this node belongs.
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@ -294,7 +307,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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Entry::Occupied(o) => {
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debug!("register_obligation_at({:?}, {:?}) - duplicate of {:?}!",
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obligation, parent, o.get());
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let node = &mut self.nodes[o.get().get()];
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let node = &mut self.nodes[o.get().index()];
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if let Some(parent_index) = parent {
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// If the node is already in `waiting_cache`, it's already
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// been marked with a parent. (It's possible that parent
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@ -318,7 +331,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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let obligation_tree_id = match parent {
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Some(parent_index) => {
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self.nodes[parent_index.get()].obligation_tree_id
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self.nodes[parent_index.index()].obligation_tree_id
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}
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None => self.obligation_tree_id_generator.next().unwrap()
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};
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@ -506,7 +519,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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node.state.set(NodeState::OnDfsStack);
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stack.push(i);
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for index in node.parent.iter().chain(node.dependents.iter()) {
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self.find_cycles_from_node(stack, processor, index.get());
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self.find_cycles_from_node(stack, processor, index.index());
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}
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stack.pop();
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node.state.set(NodeState::Done);
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@ -531,11 +544,11 @@ impl<O: ForestObligation> ObligationForest<O> {
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let node = &self.nodes[i];
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node.state.set(NodeState::Error);
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trace.push(node.obligation.clone());
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error_stack.extend(node.dependents.iter().map(|index| index.get()));
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error_stack.extend(node.dependents.iter().map(|index| index.index()));
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// Loop to the parent.
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match node.parent {
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Some(parent_index) => i = parent_index.get(),
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Some(parent_index) => i = parent_index.index(),
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None => break
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}
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}
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@ -548,7 +561,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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}
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error_stack.extend(
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node.parent.iter().chain(node.dependents.iter()).map(|index| index.get())
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node.parent.iter().chain(node.dependents.iter()).map(|index| index.index())
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);
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}
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@ -560,7 +573,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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#[inline(always)]
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fn inlined_mark_neighbors_as_waiting_from(&self, node: &Node<O>) {
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for dependent in node.parent.iter().chain(node.dependents.iter()) {
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self.mark_as_waiting_from(&self.nodes[dependent.get()]);
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self.mark_as_waiting_from(&self.nodes[dependent.index()]);
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}
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}
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@ -686,7 +699,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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for node in &mut self.nodes {
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if let Some(index) = node.parent {
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let new_i = node_rewrites[index.get()];
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let new_i = node_rewrites[index.index()];
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if new_i >= nodes_len {
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// parent dead due to error
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node.parent = None;
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@ -697,7 +710,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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let mut i = 0;
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while i < node.dependents.len() {
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let new_i = node_rewrites[node.dependents[i].get()];
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let new_i = node_rewrites[node.dependents[i].index()];
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if new_i >= nodes_len {
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node.dependents.swap_remove(i);
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} else {
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@ -709,7 +722,7 @@ impl<O: ForestObligation> ObligationForest<O> {
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let mut kill_list = vec![];
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for (predicate, index) in &mut self.waiting_cache {
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let new_i = node_rewrites[index.get()];
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let new_i = node_rewrites[index.index()];
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if new_i >= nodes_len {
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kill_list.push(predicate.clone());
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} else {
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@ -1,20 +0,0 @@
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use std::num::NonZeroU32;
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use std::u32;
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#[derive(Copy, Clone, Debug, PartialEq, Eq)]
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pub struct NodeIndex {
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index: NonZeroU32,
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}
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impl NodeIndex {
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#[inline]
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pub fn new(value: usize) -> NodeIndex {
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assert!(value < (u32::MAX as usize));
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NodeIndex { index: NonZeroU32::new((value as u32) + 1).unwrap() }
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}
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#[inline]
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pub fn get(self) -> usize {
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(self.index.get() - 1) as usize
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}
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}
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