2af8155bee
#16081 fixed an issue where a nested return statement would cause incorrect behaviour due to the inner return writing over the return stack slot that had already been written too. However, the check was very broad and picked many cases that wouldn't ever be affected by this issue. As a result, the number of allocas increased dramatically and therefore stack-size increased. LLVM is not able to remove all of the extraneous allocas. Any code that had multiple return values in a compound expression at the end of a function (including loops) would be hit by the issue. The check now uses a control-flow graph to only consider the case when the inner return is executed conditionally. By itself, this narrowed definition causes #15763 to return, so the control-flow graph is also used to avoid passing the return slot as a destination when the result won't be used. This change allows the stack-size of the main rustc task to be reduced to 8MB from 32MB.
485 lines
15 KiB
Rust
485 lines
15 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A graph module for use in dataflow, region resolution, and elsewhere.
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//!
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//! # Interface details
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//!
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//! You customize the graph by specifying a "node data" type `N` and an
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//! "edge data" type `E`. You can then later gain access (mutable or
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//! immutable) to these "user-data" bits. Currently, you can only add
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//! nodes or edges to the graph. You cannot remove or modify them once
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//! added. This could be changed if we have a need.
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//!
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//! # Implementation details
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//!
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//! The main tricky thing about this code is the way that edges are
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//! stored. The edges are stored in a central array, but they are also
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//! threaded onto two linked lists for each node, one for incoming edges
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//! and one for outgoing edges. Note that every edge is a member of some
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//! incoming list and some outgoing list. Basically you can load the
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//! first index of the linked list from the node data structures (the
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//! field `first_edge`) and then, for each edge, load the next index from
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//! the field `next_edge`). Each of those fields is an array that should
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//! be indexed by the direction (see the type `Direction`).
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#![allow(dead_code)] // still WIP
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use std::fmt::{Formatter, Error, Show};
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use std::uint;
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use std::collections::BitvSet;
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pub struct Graph<N,E> {
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nodes: Vec<Node<N>> ,
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edges: Vec<Edge<E>> ,
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}
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pub struct Node<N> {
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first_edge: [EdgeIndex, ..2], // see module comment
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pub data: N,
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}
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pub struct Edge<E> {
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next_edge: [EdgeIndex, ..2], // see module comment
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source: NodeIndex,
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target: NodeIndex,
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pub data: E,
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}
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impl<E: Show> Show for Edge<E> {
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
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write!(f, "Edge {{ next_edge: [{}, {}], source: {}, target: {}, data: {} }}",
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self.next_edge[0], self.next_edge[1], self.source,
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self.target, self.data)
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}
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}
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#[deriving(Clone, Copy, PartialEq, Show)]
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pub struct NodeIndex(pub uint);
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#[allow(non_upper_case_globals)]
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pub const InvalidNodeIndex: NodeIndex = NodeIndex(uint::MAX);
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#[deriving(Copy, PartialEq, Show)]
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pub struct EdgeIndex(pub uint);
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#[allow(non_upper_case_globals)]
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pub const InvalidEdgeIndex: EdgeIndex = EdgeIndex(uint::MAX);
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// Use a private field here to guarantee no more instances are created:
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#[deriving(Copy, Show)]
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pub struct Direction { repr: uint }
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#[allow(non_upper_case_globals)]
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pub const Outgoing: Direction = Direction { repr: 0 };
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#[allow(non_upper_case_globals)]
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pub const Incoming: Direction = Direction { repr: 1 };
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impl NodeIndex {
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fn get(&self) -> uint { let NodeIndex(v) = *self; v }
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/// Returns unique id (unique with respect to the graph holding associated node).
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pub fn node_id(&self) -> uint { self.get() }
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}
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impl EdgeIndex {
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fn get(&self) -> uint { let EdgeIndex(v) = *self; v }
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/// Returns unique id (unique with respect to the graph holding associated edge).
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pub fn edge_id(&self) -> uint { self.get() }
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}
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impl<N,E> Graph<N,E> {
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pub fn new() -> Graph<N,E> {
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Graph {
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nodes: Vec::new(),
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edges: Vec::new(),
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}
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}
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pub fn with_capacity(num_nodes: uint,
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num_edges: uint) -> Graph<N,E> {
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Graph {
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nodes: Vec::with_capacity(num_nodes),
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edges: Vec::with_capacity(num_edges),
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}
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}
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///////////////////////////////////////////////////////////////////////////
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// Simple accessors
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#[inline]
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pub fn all_nodes<'a>(&'a self) -> &'a [Node<N>] {
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let nodes: &'a [Node<N>] = self.nodes.as_slice();
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nodes
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}
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#[inline]
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pub fn all_edges<'a>(&'a self) -> &'a [Edge<E>] {
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let edges: &'a [Edge<E>] = self.edges.as_slice();
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edges
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}
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///////////////////////////////////////////////////////////////////////////
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// Node construction
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pub fn next_node_index(&self) -> NodeIndex {
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NodeIndex(self.nodes.len())
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}
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pub fn add_node(&mut self, data: N) -> NodeIndex {
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let idx = self.next_node_index();
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self.nodes.push(Node {
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first_edge: [InvalidEdgeIndex, InvalidEdgeIndex],
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data: data
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});
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idx
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}
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pub fn mut_node_data<'a>(&'a mut self, idx: NodeIndex) -> &'a mut N {
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&mut self.nodes[idx.get()].data
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}
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pub fn node_data<'a>(&'a self, idx: NodeIndex) -> &'a N {
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&self.nodes[idx.get()].data
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}
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pub fn node<'a>(&'a self, idx: NodeIndex) -> &'a Node<N> {
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&self.nodes[idx.get()]
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}
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///////////////////////////////////////////////////////////////////////////
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// Edge construction and queries
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pub fn next_edge_index(&self) -> EdgeIndex {
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EdgeIndex(self.edges.len())
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}
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pub fn add_edge(&mut self,
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source: NodeIndex,
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target: NodeIndex,
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data: E) -> EdgeIndex {
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let idx = self.next_edge_index();
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// read current first of the list of edges from each node
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let source_first = self.nodes[source.get()]
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.first_edge[Outgoing.repr];
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let target_first = self.nodes[target.get()]
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.first_edge[Incoming.repr];
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// create the new edge, with the previous firsts from each node
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// as the next pointers
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self.edges.push(Edge {
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next_edge: [source_first, target_first],
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source: source,
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target: target,
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data: data
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});
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// adjust the firsts for each node target be the next object.
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self.nodes[source.get()].first_edge[Outgoing.repr] = idx;
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self.nodes[target.get()].first_edge[Incoming.repr] = idx;
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return idx;
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}
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pub fn mut_edge_data<'a>(&'a mut self, idx: EdgeIndex) -> &'a mut E {
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&mut self.edges[idx.get()].data
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}
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pub fn edge_data<'a>(&'a self, idx: EdgeIndex) -> &'a E {
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&self.edges[idx.get()].data
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}
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pub fn edge<'a>(&'a self, idx: EdgeIndex) -> &'a Edge<E> {
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&self.edges[idx.get()]
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}
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pub fn first_adjacent(&self, node: NodeIndex, dir: Direction) -> EdgeIndex {
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//! Accesses the index of the first edge adjacent to `node`.
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//! This is useful if you wish to modify the graph while walking
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//! the linked list of edges.
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self.nodes[node.get()].first_edge[dir.repr]
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}
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pub fn next_adjacent(&self, edge: EdgeIndex, dir: Direction) -> EdgeIndex {
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//! Accesses the next edge in a given direction.
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//! This is useful if you wish to modify the graph while walking
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//! the linked list of edges.
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self.edges[edge.get()].next_edge[dir.repr]
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}
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///////////////////////////////////////////////////////////////////////////
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// Iterating over nodes, edges
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pub fn each_node<'a, F>(&'a self, mut f: F) -> bool where
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F: FnMut(NodeIndex, &'a Node<N>) -> bool,
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{
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//! Iterates over all edges defined in the graph.
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self.nodes.iter().enumerate().all(|(i, node)| f(NodeIndex(i), node))
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}
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pub fn each_edge<'a, F>(&'a self, mut f: F) -> bool where
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F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
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{
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//! Iterates over all edges defined in the graph
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self.edges.iter().enumerate().all(|(i, edge)| f(EdgeIndex(i), edge))
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}
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pub fn each_outgoing_edge<'a, F>(&'a self, source: NodeIndex, f: F) -> bool where
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F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
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{
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//! Iterates over all outgoing edges from the node `from`
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self.each_adjacent_edge(source, Outgoing, f)
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}
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pub fn each_incoming_edge<'a, F>(&'a self, target: NodeIndex, f: F) -> bool where
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F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
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{
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//! Iterates over all incoming edges to the node `target`
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self.each_adjacent_edge(target, Incoming, f)
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}
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pub fn each_adjacent_edge<'a, F>(&'a self,
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node: NodeIndex,
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dir: Direction,
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mut f: F)
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-> bool where
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F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
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{
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//! Iterates over all edges adjacent to the node `node`
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//! in the direction `dir` (either `Outgoing` or `Incoming)
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let mut edge_idx = self.first_adjacent(node, dir);
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while edge_idx != InvalidEdgeIndex {
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let edge = &self.edges[edge_idx.get()];
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if !f(edge_idx, edge) {
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return false;
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}
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edge_idx = edge.next_edge[dir.repr];
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}
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return true;
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}
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///////////////////////////////////////////////////////////////////////////
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// Fixed-point iteration
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//
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// A common use for graphs in our compiler is to perform
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// fixed-point iteration. In this case, each edge represents a
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// constraint, and the nodes themselves are associated with
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// variables or other bitsets. This method facilitates such a
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// computation.
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pub fn iterate_until_fixed_point<'a, F>(&'a self, mut op: F) where
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F: FnMut(uint, EdgeIndex, &'a Edge<E>) -> bool,
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{
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let mut iteration = 0;
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let mut changed = true;
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while changed {
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changed = false;
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iteration += 1;
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for (i, edge) in self.edges.iter().enumerate() {
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changed |= op(iteration, EdgeIndex(i), edge);
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}
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}
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}
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pub fn depth_traverse<'a>(&'a self, start: NodeIndex) -> DepthFirstTraversal<'a, N, E> {
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DepthFirstTraversal {
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graph: self,
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stack: vec![start],
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visited: BitvSet::new()
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}
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}
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}
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pub struct DepthFirstTraversal<'g, N:'g, E:'g> {
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graph: &'g Graph<N, E>,
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stack: Vec<NodeIndex>,
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visited: BitvSet
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}
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impl<'g, N, E> Iterator<&'g N> for DepthFirstTraversal<'g, N, E> {
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fn next(&mut self) -> Option<&'g N> {
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while let Some(idx) = self.stack.pop() {
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if !self.visited.insert(idx.node_id()) {
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continue;
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}
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self.graph.each_outgoing_edge(idx, |_, e| -> bool {
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if !self.visited.contains(&e.target().node_id()) {
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self.stack.push(e.target());
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}
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true
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});
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return Some(self.graph.node_data(idx));
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}
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return None;
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}
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}
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pub fn each_edge_index<F>(max_edge_index: EdgeIndex, mut f: F) where
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F: FnMut(EdgeIndex) -> bool,
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{
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let mut i = 0;
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let n = max_edge_index.get();
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while i < n {
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if !f(EdgeIndex(i)) {
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return;
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}
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i += 1;
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}
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}
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impl<E> Edge<E> {
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pub fn source(&self) -> NodeIndex {
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self.source
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}
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pub fn target(&self) -> NodeIndex {
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self.target
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}
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}
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#[cfg(test)]
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mod test {
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use middle::graph::*;
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use std::fmt::Show;
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type TestNode = Node<&'static str>;
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type TestEdge = Edge<&'static str>;
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type TestGraph = Graph<&'static str, &'static str>;
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fn create_graph() -> TestGraph {
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let mut graph = Graph::new();
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// Create a simple graph
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//
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// A -+> B --> C
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// | | ^
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// | v |
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// F D --> E
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let a = graph.add_node("A");
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let b = graph.add_node("B");
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let c = graph.add_node("C");
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let d = graph.add_node("D");
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let e = graph.add_node("E");
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let f = graph.add_node("F");
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graph.add_edge(a, b, "AB");
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graph.add_edge(b, c, "BC");
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graph.add_edge(b, d, "BD");
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graph.add_edge(d, e, "DE");
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graph.add_edge(e, c, "EC");
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graph.add_edge(f, b, "FB");
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return graph;
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}
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#[test]
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fn each_node() {
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let graph = create_graph();
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let expected = ["A", "B", "C", "D", "E", "F"];
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graph.each_node(|idx, node| {
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assert_eq!(&expected[idx.get()], graph.node_data(idx));
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assert_eq!(expected[idx.get()], node.data);
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true
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});
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}
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#[test]
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fn each_edge() {
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let graph = create_graph();
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let expected = ["AB", "BC", "BD", "DE", "EC", "FB"];
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graph.each_edge(|idx, edge| {
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assert_eq!(&expected[idx.get()], graph.edge_data(idx));
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assert_eq!(expected[idx.get()], edge.data);
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true
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});
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}
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fn test_adjacent_edges<N:PartialEq+Show,E:PartialEq+Show>(graph: &Graph<N,E>,
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start_index: NodeIndex,
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start_data: N,
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expected_incoming: &[(E,N)],
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expected_outgoing: &[(E,N)]) {
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assert!(graph.node_data(start_index) == &start_data);
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let mut counter = 0;
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graph.each_incoming_edge(start_index, |edge_index, edge| {
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assert!(graph.edge_data(edge_index) == &edge.data);
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assert!(counter < expected_incoming.len());
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debug!("counter={} expected={} edge_index={} edge={}",
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counter, expected_incoming[counter], edge_index, edge);
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match expected_incoming[counter] {
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(ref e, ref n) => {
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assert!(e == &edge.data);
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assert!(n == graph.node_data(edge.source));
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assert!(start_index == edge.target);
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}
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}
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counter += 1;
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true
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});
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assert_eq!(counter, expected_incoming.len());
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let mut counter = 0;
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graph.each_outgoing_edge(start_index, |edge_index, edge| {
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assert!(graph.edge_data(edge_index) == &edge.data);
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assert!(counter < expected_outgoing.len());
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debug!("counter={} expected={} edge_index={} edge={}",
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counter, expected_outgoing[counter], edge_index, edge);
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match expected_outgoing[counter] {
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(ref e, ref n) => {
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assert!(e == &edge.data);
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assert!(start_index == edge.source);
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assert!(n == graph.node_data(edge.target));
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}
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}
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counter += 1;
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true
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});
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assert_eq!(counter, expected_outgoing.len());
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}
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#[test]
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fn each_adjacent_from_a() {
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let graph = create_graph();
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test_adjacent_edges(&graph, NodeIndex(0), "A",
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&[],
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&[("AB", "B")]);
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}
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#[test]
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fn each_adjacent_from_b() {
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let graph = create_graph();
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test_adjacent_edges(&graph, NodeIndex(1), "B",
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&[("FB", "F"), ("AB", "A"),],
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&[("BD", "D"), ("BC", "C"),]);
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}
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#[test]
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fn each_adjacent_from_c() {
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let graph = create_graph();
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test_adjacent_edges(&graph, NodeIndex(2), "C",
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&[("EC", "E"), ("BC", "B")],
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&[]);
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}
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#[test]
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fn each_adjacent_from_d() {
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let graph = create_graph();
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test_adjacent_edges(&graph, NodeIndex(3), "D",
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&[("BD", "B")],
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&[("DE", "E")]);
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}
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}
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