blob: 7df7fded78ae0e15b9540b34a859d04dcfb87680 [file] [log] [blame]
// Copyright 2015 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.
#include "src/compiler/control-equivalence.h"
#include "src/compiler/node-properties.h"
#define TRACE(...) \
do { \
if (FLAG_trace_turbo_ceq) PrintF(__VA_ARGS__); \
} while (false)
namespace v8 {
namespace internal {
namespace compiler {
void ControlEquivalence::Run(Node* exit) {
if (!Participates(exit) || GetClass(exit) == kInvalidClass) {
DetermineParticipation(exit);
RunUndirectedDFS(exit);
}
}
// static
STATIC_CONST_MEMBER_DEFINITION const size_t ControlEquivalence::kInvalidClass;
void ControlEquivalence::VisitPre(Node* node) {
TRACE("CEQ: Pre-visit of #%d:%s\n", node->id(), node->op()->mnemonic());
}
void ControlEquivalence::VisitMid(Node* node, DFSDirection direction) {
TRACE("CEQ: Mid-visit of #%d:%s\n", node->id(), node->op()->mnemonic());
BracketList& blist = GetBracketList(node);
// Remove brackets pointing to this node [line:19].
BracketListDelete(blist, node, direction);
// Potentially introduce artificial dependency from start to end.
if (blist.empty()) {
DCHECK_EQ(kInputDirection, direction);
VisitBackedge(node, graph_->end(), kInputDirection);
}
// Potentially start a new equivalence class [line:37].
BracketListTRACE(blist);
Bracket* recent = &blist.back();
if (recent->recent_size != blist.size()) {
recent->recent_size = blist.size();
recent->recent_class = NewClassNumber();
}
// Assign equivalence class to node.
SetClass(node, recent->recent_class);
TRACE(" Assigned class number is %zu\n", GetClass(node));
}
void ControlEquivalence::VisitPost(Node* node, Node* parent_node,
DFSDirection direction) {
TRACE("CEQ: Post-visit of #%d:%s\n", node->id(), node->op()->mnemonic());
BracketList& blist = GetBracketList(node);
// Remove brackets pointing to this node [line:19].
BracketListDelete(blist, node, direction);
// Propagate bracket list up the DFS tree [line:13].
if (parent_node != nullptr) {
BracketList& parent_blist = GetBracketList(parent_node);
parent_blist.splice(parent_blist.end(), blist);
}
}
void ControlEquivalence::VisitBackedge(Node* from, Node* to,
DFSDirection direction) {
TRACE("CEQ: Backedge from #%d:%s to #%d:%s\n", from->id(),
from->op()->mnemonic(), to->id(), to->op()->mnemonic());
// Push backedge onto the bracket list [line:25].
Bracket bracket = {direction, kInvalidClass, 0, from, to};
GetBracketList(from).push_back(bracket);
}
void ControlEquivalence::RunUndirectedDFS(Node* exit) {
ZoneStack<DFSStackEntry> stack(zone_);
DFSPush(stack, exit, nullptr, kInputDirection);
VisitPre(exit);
while (!stack.empty()) { // Undirected depth-first backwards traversal.
DFSStackEntry& entry = stack.top();
Node* node = entry.node;
if (entry.direction == kInputDirection) {
if (entry.input != node->input_edges().end()) {
Edge edge = *entry.input;
Node* input = edge.to();
++(entry.input);
if (NodeProperties::IsControlEdge(edge)) {
// Visit next control input.
if (!Participates(input)) continue;
if (GetData(input)->visited) continue;
if (GetData(input)->on_stack) {
// Found backedge if input is on stack.
if (input != entry.parent_node) {
VisitBackedge(node, input, kInputDirection);
}
} else {
// Push input onto stack.
DFSPush(stack, input, node, kInputDirection);
VisitPre(input);
}
}
continue;
}
if (entry.use != node->use_edges().end()) {
// Switch direction to uses.
entry.direction = kUseDirection;
VisitMid(node, kInputDirection);
continue;
}
}
if (entry.direction == kUseDirection) {
if (entry.use != node->use_edges().end()) {
Edge edge = *entry.use;
Node* use = edge.from();
++(entry.use);
if (NodeProperties::IsControlEdge(edge)) {
// Visit next control use.
if (!Participates(use)) continue;
if (GetData(use)->visited) continue;
if (GetData(use)->on_stack) {
// Found backedge if use is on stack.
if (use != entry.parent_node) {
VisitBackedge(node, use, kUseDirection);
}
} else {
// Push use onto stack.
DFSPush(stack, use, node, kUseDirection);
VisitPre(use);
}
}
continue;
}
if (entry.input != node->input_edges().end()) {
// Switch direction to inputs.
entry.direction = kInputDirection;
VisitMid(node, kUseDirection);
continue;
}
}
// Pop node from stack when done with all inputs and uses.
DCHECK(entry.input == node->input_edges().end());
DCHECK(entry.use == node->use_edges().end());
DFSPop(stack, node);
VisitPost(node, entry.parent_node, entry.direction);
}
}
void ControlEquivalence::DetermineParticipationEnqueue(ZoneQueue<Node*>& queue,
Node* node) {
if (!Participates(node)) {
AllocateData(node);
queue.push(node);
}
}
void ControlEquivalence::DetermineParticipation(Node* exit) {
ZoneQueue<Node*> queue(zone_);
DetermineParticipationEnqueue(queue, exit);
while (!queue.empty()) { // Breadth-first backwards traversal.
Node* node = queue.front();
queue.pop();
int max = NodeProperties::PastControlIndex(node);
for (int i = NodeProperties::FirstControlIndex(node); i < max; i++) {
DetermineParticipationEnqueue(queue, node->InputAt(i));
}
}
}
void ControlEquivalence::DFSPush(DFSStack& stack, Node* node, Node* from,
DFSDirection dir) {
DCHECK(Participates(node));
DCHECK(!GetData(node)->visited);
GetData(node)->on_stack = true;
Node::InputEdges::iterator input = node->input_edges().begin();
Node::UseEdges::iterator use = node->use_edges().begin();
stack.push({dir, input, use, from, node});
}
void ControlEquivalence::DFSPop(DFSStack& stack, Node* node) {
DCHECK_EQ(stack.top().node, node);
GetData(node)->on_stack = false;
GetData(node)->visited = true;
stack.pop();
}
void ControlEquivalence::BracketListDelete(BracketList& blist, Node* to,
DFSDirection direction) {
// TODO(mstarzinger): Optimize this to avoid linear search.
for (BracketList::iterator i = blist.begin(); i != blist.end(); /*nop*/) {
if (i->to == to && i->direction != direction) {
TRACE(" BList erased: {%d->%d}\n", i->from->id(), i->to->id());
i = blist.erase(i);
} else {
++i;
}
}
}
void ControlEquivalence::BracketListTRACE(BracketList& blist) {
if (FLAG_trace_turbo_ceq) {
TRACE(" BList: ");
for (Bracket bracket : blist) {
TRACE("{%d->%d} ", bracket.from->id(), bracket.to->id());
}
TRACE("\n");
}
}
#undef TRACE
} // namespace compiler
} // namespace internal
} // namespace v8