Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/compiler/tail-call-optimization.h" |
| 6 | |
| 7 | #include "src/compiler/common-operator.h" |
| 8 | #include "src/compiler/graph.h" |
| 9 | #include "src/compiler/linkage.h" |
| 10 | #include "src/compiler/node-properties.h" |
| 11 | |
| 12 | namespace v8 { |
| 13 | namespace internal { |
| 14 | namespace compiler { |
| 15 | |
| 16 | Reduction TailCallOptimization::Reduce(Node* node) { |
| 17 | if (node->opcode() != IrOpcode::kReturn) return NoChange(); |
| 18 | // The value which is returned must be the result of a potential tail call, |
| 19 | // there must be no try/catch/finally around the Call, and there must be no |
| 20 | // other effect between the Call and the Return nodes. |
| 21 | Node* const call = NodeProperties::GetValueInput(node, 0); |
| 22 | if (call->opcode() == IrOpcode::kCall && |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 23 | CallDescriptorOf(call->op())->SupportsTailCalls() && |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 24 | NodeProperties::GetEffectInput(node) == call && |
| 25 | !NodeProperties::IsExceptionalCall(call)) { |
| 26 | Node* const control = NodeProperties::GetControlInput(node); |
| 27 | if (control->opcode() == IrOpcode::kIfSuccess && |
| 28 | call->OwnedBy(node, control) && control->OwnedBy(node)) { |
| 29 | // Furthermore, control has to flow via an IfSuccess from the Call, so |
| 30 | // the Return node value and effect depends directly on the Call node, |
| 31 | // and indirectly control depends on the Call via an IfSuccess. |
| 32 | |
| 33 | // Value1 ... ValueN Effect Control |
| 34 | // ^ ^ ^ ^ |
| 35 | // | | | | |
| 36 | // | +--+ +-+ | |
| 37 | // +----------+ | | +------+ |
| 38 | // \ | | / |
| 39 | // Call[Descriptor] |
| 40 | // ^ ^ ^ |
| 41 | // | | | |
| 42 | // +-+ | | |
| 43 | // | | | |
| 44 | // | +-+ | |
| 45 | // | | IfSuccess |
| 46 | // | | ^ |
| 47 | // | | | |
| 48 | // Return |
| 49 | // ^ |
| 50 | // | |
| 51 | |
| 52 | // The resulting graph looks like this: |
| 53 | |
| 54 | // Value1 ... ValueN Effect Control |
| 55 | // ^ ^ ^ ^ |
| 56 | // | | | | |
| 57 | // | +--+ +-+ | |
| 58 | // +----------+ | | +------+ |
| 59 | // \ | | / |
| 60 | // TailCall[Descriptor] |
| 61 | // ^ |
| 62 | // | |
| 63 | |
| 64 | DCHECK_EQ(call, NodeProperties::GetControlInput(control, 0)); |
| 65 | DCHECK_EQ(3, node->InputCount()); |
| 66 | node->ReplaceInput(0, NodeProperties::GetEffectInput(call)); |
| 67 | node->ReplaceInput(1, NodeProperties::GetControlInput(call)); |
| 68 | node->RemoveInput(2); |
| 69 | for (int index = 0; index < call->op()->ValueInputCount(); ++index) { |
| 70 | node->InsertInput(graph()->zone(), index, |
| 71 | NodeProperties::GetValueInput(call, index)); |
| 72 | } |
| 73 | NodeProperties::ChangeOp( |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 74 | node, common()->TailCall(CallDescriptorOf(call->op()))); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 75 | return Changed(node); |
| 76 | } |
| 77 | } |
| 78 | return NoChange(); |
| 79 | } |
| 80 | |
| 81 | } // namespace compiler |
| 82 | } // namespace internal |
| 83 | } // namespace v8 |