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// 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-flow-optimizer.h"
#include "src/compiler/common-operator.h"
#include "src/compiler/graph.h"
#include "src/compiler/node-matchers.h"
#include "src/compiler/node-properties.h"
namespace v8 {
namespace internal {
namespace compiler {
ControlFlowOptimizer::ControlFlowOptimizer(Graph* graph,
CommonOperatorBuilder* common,
MachineOperatorBuilder* machine,
Zone* zone)
: graph_(graph),
common_(common),
machine_(machine),
queue_(zone),
queued_(graph, 2),
zone_(zone) {}
void ControlFlowOptimizer::Optimize() {
Enqueue(graph()->start());
while (!queue_.empty()) {
Node* node = queue_.front();
queue_.pop();
if (node->IsDead()) continue;
switch (node->opcode()) {
case IrOpcode::kBranch:
VisitBranch(node);
break;
default:
VisitNode(node);
break;
}
}
}
void ControlFlowOptimizer::Enqueue(Node* node) {
DCHECK_NOT_NULL(node);
if (node->IsDead() || queued_.Get(node)) return;
queued_.Set(node, true);
queue_.push(node);
}
void ControlFlowOptimizer::VisitNode(Node* node) {
for (Edge edge : node->use_edges()) {
if (NodeProperties::IsControlEdge(edge)) {
Enqueue(edge.from());
}
}
}
void ControlFlowOptimizer::VisitBranch(Node* node) {
DCHECK_EQ(IrOpcode::kBranch, node->opcode());
if (TryBuildSwitch(node)) return;
VisitNode(node);
}
bool ControlFlowOptimizer::TryBuildSwitch(Node* node) {
DCHECK_EQ(IrOpcode::kBranch, node->opcode());
Node* branch = node;
if (BranchHintOf(branch->op()) != BranchHint::kNone) return false;
Node* cond = NodeProperties::GetValueInput(branch, 0);
if (cond->opcode() != IrOpcode::kWord32Equal) return false;
Int32BinopMatcher m(cond);
Node* index = m.left().node();
if (!m.right().HasValue()) return false;
int32_t value = m.right().Value();
ZoneSet<int32_t> values(zone());
values.insert(value);
Node* if_false;
Node* if_true;
int32_t order = 1;
while (true) {
BranchMatcher matcher(branch);
DCHECK(matcher.Matched());
if_true = matcher.IfTrue();
if_false = matcher.IfFalse();
auto it = if_false->uses().begin();
if (it == if_false->uses().end()) break;
Node* branch1 = *it++;
if (branch1->opcode() != IrOpcode::kBranch) break;
if (BranchHintOf(branch1->op()) != BranchHint::kNone) break;
if (it != if_false->uses().end()) break;
Node* cond1 = branch1->InputAt(0);
if (cond1->opcode() != IrOpcode::kWord32Equal) break;
Int32BinopMatcher m1(cond1);
if (m1.left().node() != index) break;
if (!m1.right().HasValue()) break;
int32_t value1 = m1.right().Value();
if (values.find(value1) != values.end()) break;
DCHECK_NE(value, value1);
if (branch != node) {
branch->NullAllInputs();
if_true->ReplaceInput(0, node);
}
NodeProperties::ChangeOp(if_true, common()->IfValue(value, order++));
if_false->NullAllInputs();
Enqueue(if_true);
branch = branch1;
value = value1;
values.insert(value);
}
DCHECK_EQ(IrOpcode::kBranch, node->opcode());
DCHECK_EQ(IrOpcode::kBranch, branch->opcode());
if (branch == node) {
DCHECK_EQ(1u, values.size());
return false;
}
DCHECK_LT(1u, values.size());
node->ReplaceInput(0, index);
NodeProperties::ChangeOp(node, common()->Switch(values.size() + 1));
if_true->ReplaceInput(0, node);
NodeProperties::ChangeOp(if_true, common()->IfValue(value, order++));
Enqueue(if_true);
if_false->ReplaceInput(0, node);
NodeProperties::ChangeOp(if_false, common()->IfDefault());
Enqueue(if_false);
branch->NullAllInputs();
return true;
}
} // namespace compiler
} // namespace internal
} // namespace v8
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