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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/tail-call-optimization.h"
#include "src/compiler/common-operator.h"
#include "src/compiler/graph.h"
#include "src/compiler/linkage.h"
#include "src/compiler/node-properties.h"
namespace v8 {
namespace internal {
namespace compiler {
Reduction TailCallOptimization::Reduce(Node* node) {
if (node->opcode() != IrOpcode::kReturn) return NoChange();
// The value which is returned must be the result of a potential tail call,
// there must be no try/catch/finally around the Call, and there must be no
// other effect between the Call and the Return nodes.
Node* const call = NodeProperties::GetValueInput(node, 0);
if (call->opcode() == IrOpcode::kCall &&
OpParameter<CallDescriptor const*>(call)->SupportsTailCalls() &&
NodeProperties::GetEffectInput(node) == call &&
!NodeProperties::IsExceptionalCall(call)) {
Node* const control = NodeProperties::GetControlInput(node);
if (control->opcode() == IrOpcode::kIfSuccess &&
call->OwnedBy(node, control) && control->OwnedBy(node)) {
// Furthermore, control has to flow via an IfSuccess from the Call, so
// the Return node value and effect depends directly on the Call node,
// and indirectly control depends on the Call via an IfSuccess.
// Value1 ... ValueN Effect Control
// ^ ^ ^ ^
// | | | |
// | +--+ +-+ |
// +----------+ | | +------+
// \ | | /
// Call[Descriptor]
// ^ ^ ^
// | | |
// +-+ | |
// | | |
// | +-+ |
// | | IfSuccess
// | | ^
// | | |
// Return
// ^
// |
// The resulting graph looks like this:
// Value1 ... ValueN Effect Control
// ^ ^ ^ ^
// | | | |
// | +--+ +-+ |
// +----------+ | | +------+
// \ | | /
// TailCall[Descriptor]
// ^
// |
DCHECK_EQ(call, NodeProperties::GetControlInput(control, 0));
DCHECK_EQ(3, node->InputCount());
node->ReplaceInput(0, NodeProperties::GetEffectInput(call));
node->ReplaceInput(1, NodeProperties::GetControlInput(call));
node->RemoveInput(2);
for (int index = 0; index < call->op()->ValueInputCount(); ++index) {
node->InsertInput(graph()->zone(), index,
NodeProperties::GetValueInput(call, index));
}
NodeProperties::ChangeOp(
node, common()->TailCall(OpParameter<CallDescriptor const*>(call)));
return Changed(node);
}
}
return NoChange();
}
} // namespace compiler
} // namespace internal
} // namespace v8
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