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-matchers.h" 11 #include "src/compiler/node-properties.h" 12 13 namespace v8 { 14 namespace internal { 15 namespace compiler { 16 17 Reduction TailCallOptimization::Reduce(Node* node) { 18 if (node->opcode() != IrOpcode::kReturn) return NoChange(); 19 // The value which is returned must be the result of a potential tail call, 20 // there must be no try/catch/finally around the Call, and there must be no 21 // other effect between the Call and the Return nodes. 22 Node* const call = NodeProperties::GetValueInput(node, 1); 23 if (call->opcode() == IrOpcode::kCall && 24 CallDescriptorOf(call->op())->SupportsTailCalls() && 25 NodeProperties::GetEffectInput(node) == call && 26 !NodeProperties::IsExceptionalCall(call)) { 27 Node* const control = NodeProperties::GetControlInput(node); 28 // Ensure that no additional arguments are being popped other than those in 29 // the CallDescriptor, otherwise the tail call transformation is invalid. 30 DCHECK_EQ(0, Int32Matcher(NodeProperties::GetValueInput(node, 0)).Value()); 31 if (control->opcode() == IrOpcode::kIfSuccess && 32 call->OwnedBy(node, control) && control->OwnedBy(node)) { 33 // Furthermore, control has to flow via an IfSuccess from the Call, so 34 // the Return node value and effect depends directly on the Call node, 35 // and indirectly control depends on the Call via an IfSuccess. 36 37 // Value1 ... ValueN Effect Control 38 // ^ ^ ^ ^ 39 // | | | | 40 // | +--+ +-+ | 41 // +----------+ | | +------+ 42 // \ | | / 43 // Call[Descriptor] 44 // ^ ^ ^ 45 // | | | 46 // +-+ | | 47 // | | | 48 // | +-+ | 49 // | | IfSuccess 50 // | | ^ 51 // | | | 52 // Return 53 // ^ 54 // | 55 56 // The resulting graph looks like this: 57 58 // Value1 ... ValueN Effect Control 59 // ^ ^ ^ ^ 60 // | | | | 61 // | +--+ +-+ | 62 // +----------+ | | +------+ 63 // \ | | / 64 // TailCall[Descriptor] 65 // ^ 66 // | 67 68 DCHECK_EQ(call, NodeProperties::GetControlInput(control, 0)); 69 DCHECK_EQ(4, node->InputCount()); 70 node->ReplaceInput(0, NodeProperties::GetEffectInput(call)); 71 node->ReplaceInput(1, NodeProperties::GetControlInput(call)); 72 node->RemoveInput(3); 73 node->RemoveInput(2); 74 for (int index = 0; index < call->op()->ValueInputCount(); ++index) { 75 node->InsertInput(graph()->zone(), index, 76 NodeProperties::GetValueInput(call, index)); 77 } 78 NodeProperties::ChangeOp( 79 node, common()->TailCall(CallDescriptorOf(call->op()))); 80 return Changed(node); 81 } 82 } 83 return NoChange(); 84 } 85 86 } // namespace compiler 87 } // namespace internal 88 } // namespace v8 89
