| // 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-matchers.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 or control between the Call and the Return nodes. |
| Node* const call = NodeProperties::GetValueInput(node, 1); |
| if (call->opcode() == IrOpcode::kCall && |
| CallDescriptorOf(call->op())->SupportsTailCalls() && |
| NodeProperties::GetEffectInput(node) == call && |
| NodeProperties::GetControlInput(node) == call && |
| !NodeProperties::IsExceptionalCall(call) && call->UseCount() == 3) { |
| // Ensure that no additional arguments are being popped other than those in |
| // the CallDescriptor, otherwise the tail call transformation is invalid. |
| DCHECK_EQ(0, Int32Matcher(NodeProperties::GetValueInput(node, 0)).Value()); |
| // Furthermore, the Return node value, effect, and control depends |
| // directly on the Call, no other uses of the Call node exist. |
| // |
| // The input graph looks as follows: |
| |
| // Value1 ... ValueN Effect Control |
| // ^ ^ ^ ^ |
| // | | | | |
| // | +--+ +-+ | |
| // +----------+ | | +------+ |
| // \ | | / |
| // Call[Descriptor] |
| // ^ ^ ^ |
| // Int32(0) <-+ | | | |
| // \ | | | |
| // Return |
| // ^ |
| // | |
| |
| // The resulting graph looks like this: |
| |
| // Value1 ... ValueN Effect Control |
| // ^ ^ ^ ^ |
| // | | | | |
| // | +--+ +-+ | |
| // +----------+ | | +------+ |
| // \ | | / |
| // TailCall[Descriptor] |
| // ^ |
| // | |
| |
| DCHECK_EQ(4, node->InputCount()); |
| node->ReplaceInput(0, NodeProperties::GetEffectInput(call)); |
| node->ReplaceInput(1, NodeProperties::GetControlInput(call)); |
| node->RemoveInput(3); |
| 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 |