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// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_COMPILER_GENERIC_ALGORITHM_H_
#define V8_COMPILER_GENERIC_ALGORITHM_H_
#include <deque>
#include <stack>
#include "src/compiler/generic-graph.h"
#include "src/compiler/generic-node.h"
#include "src/zone-containers.h"
namespace v8 {
namespace internal {
namespace compiler {
// GenericGraphVisit allows visitation of graphs of nodes and edges in pre- and
// post-order. Visitation uses an explicitly allocated stack rather than the
// execution stack to avoid stack overflow. Although GenericGraphVisit is
// primarily intended to traverse networks of nodes through their
// dependencies and uses, it also can be used to visit any graph-like network
// by specifying custom traits.
class GenericGraphVisit {
public:
enum Control {
CONTINUE = 0x0, // Continue depth-first normally
SKIP = 0x1, // Skip this node and its successors
REENTER = 0x2, // Allow reentering this node
DEFER = SKIP | REENTER
};
// struct Visitor {
// Control Pre(Traits::Node* current);
// Control Post(Traits::Node* current);
// void PreEdge(Traits::Node* from, int index, Traits::Node* to);
// void PostEdge(Traits::Node* from, int index, Traits::Node* to);
// }
template <class Visitor, class Traits, class RootIterator>
static void Visit(GenericGraphBase* graph, RootIterator root_begin,
RootIterator root_end, Visitor* visitor) {
// TODO(bmeurer): Pass "local" zone as parameter.
Zone* zone = graph->zone();
typedef typename Traits::Node Node;
typedef typename Traits::Iterator Iterator;
typedef std::pair<Iterator, Iterator> NodeState;
typedef zone_allocator<NodeState> ZoneNodeStateAllocator;
typedef std::deque<NodeState, ZoneNodeStateAllocator> NodeStateDeque;
typedef std::stack<NodeState, NodeStateDeque> NodeStateStack;
NodeStateStack stack((NodeStateDeque(ZoneNodeStateAllocator(zone))));
BoolVector visited(Traits::max_id(graph), false, ZoneBoolAllocator(zone));
Node* current = *root_begin;
while (true) {
DCHECK(current != NULL);
const int id = current->id();
DCHECK(id >= 0);
DCHECK(id < Traits::max_id(graph)); // Must be a valid id.
bool visit = !GetVisited(&visited, id);
if (visit) {
Control control = visitor->Pre(current);
visit = !IsSkip(control);
if (!IsReenter(control)) SetVisited(&visited, id, true);
}
Iterator begin(visit ? Traits::begin(current) : Traits::end(current));
Iterator end(Traits::end(current));
stack.push(NodeState(begin, end));
Node* post_order_node = current;
while (true) {
NodeState top = stack.top();
if (top.first == top.second) {
if (visit) {
Control control = visitor->Post(post_order_node);
DCHECK(!IsSkip(control));
SetVisited(&visited, post_order_node->id(), !IsReenter(control));
}
stack.pop();
if (stack.empty()) {
if (++root_begin == root_end) return;
current = *root_begin;
break;
}
post_order_node = Traits::from(stack.top().first);
visit = true;
} else {
visitor->PreEdge(Traits::from(top.first), top.first.edge().index(),
Traits::to(top.first));
current = Traits::to(top.first);
if (!GetVisited(&visited, current->id())) break;
}
top = stack.top();
visitor->PostEdge(Traits::from(top.first), top.first.edge().index(),
Traits::to(top.first));
++stack.top().first;
}
}
}
template <class Visitor, class Traits>
static void Visit(GenericGraphBase* graph, typename Traits::Node* current,
Visitor* visitor) {
typename Traits::Node* array[] = {current};
Visit<Visitor, Traits>(graph, &array[0], &array[1], visitor);
}
template <class B, class S>
struct NullNodeVisitor {
Control Pre(GenericNode<B, S>* node) { return CONTINUE; }
Control Post(GenericNode<B, S>* node) { return CONTINUE; }
void PreEdge(GenericNode<B, S>* from, int index, GenericNode<B, S>* to) {}
void PostEdge(GenericNode<B, S>* from, int index, GenericNode<B, S>* to) {}
};
private:
static bool IsSkip(Control c) { return c & SKIP; }
static bool IsReenter(Control c) { return c & REENTER; }
// TODO(turbofan): resizing could be optionally templatized away.
static void SetVisited(BoolVector* visited, int id, bool value) {
if (id >= static_cast<int>(visited->size())) {
// Resize and set all values to unvisited.
visited->resize((3 * id) / 2, false);
}
visited->at(id) = value;
}
static bool GetVisited(BoolVector* visited, int id) {
if (id >= static_cast<int>(visited->size())) return false;
return visited->at(id);
}
};
}
}
} // namespace v8::internal::compiler
#endif // V8_COMPILER_GENERIC_ALGORITHM_H_
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