| // 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 && |
| CallDescriptorOf(call->op())->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(CallDescriptorOf(call->op()))); |
| return Changed(node); |
| } |
| } |
| return NoChange(); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |