| // Copyright 2014 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/select-lowering.h" |
| |
| #include "src/compiler/common-operator.h" |
| #include "src/compiler/diamond.h" |
| #include "src/compiler/graph.h" |
| #include "src/compiler/node.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| SelectLowering::SelectLowering(Graph* graph, CommonOperatorBuilder* common) |
| : common_(common), |
| graph_(graph), |
| merges_(Merges::key_compare(), Merges::allocator_type(graph->zone())) {} |
| |
| |
| SelectLowering::~SelectLowering() {} |
| |
| |
| Reduction SelectLowering::Reduce(Node* node) { |
| if (node->opcode() != IrOpcode::kSelect) return NoChange(); |
| SelectParameters const p = SelectParametersOf(node->op()); |
| |
| Node* cond = node->InputAt(0); |
| Node* vthen = node->InputAt(1); |
| Node* velse = node->InputAt(2); |
| Node* merge = nullptr; |
| |
| // Check if we already have a diamond for this condition. |
| auto range = merges_.equal_range(cond); |
| for (auto i = range.first;; ++i) { |
| if (i == range.second) { |
| // Create a new diamond for this condition and remember its merge node. |
| Diamond d(graph(), common(), cond, p.hint()); |
| merges_.insert(std::make_pair(cond, d.merge)); |
| merge = d.merge; |
| break; |
| } |
| |
| // If the diamond is reachable from the Select, merging them would result in |
| // an unschedulable graph, so we cannot reuse the diamond in that case. |
| merge = i->second; |
| if (!ReachableFrom(merge, node)) { |
| break; |
| } |
| } |
| |
| // Create a Phi hanging off the previously determined merge. |
| node->set_op(common()->Phi(p.type(), 2)); |
| node->ReplaceInput(0, vthen); |
| node->ReplaceInput(1, velse); |
| node->ReplaceInput(2, merge); |
| return Changed(node); |
| } |
| |
| |
| bool SelectLowering::ReachableFrom(Node* const sink, Node* const source) { |
| // TODO(turbofan): This is probably horribly expensive, and it should be moved |
| // into node.h or somewhere else?! |
| Zone zone(graph()->zone()->isolate()); |
| std::queue<Node*, NodeDeque> queue((NodeDeque(&zone))); |
| BoolVector visited(graph()->NodeCount(), false, &zone); |
| queue.push(source); |
| visited[source->id()] = true; |
| while (!queue.empty()) { |
| Node* current = queue.front(); |
| if (current == sink) return true; |
| queue.pop(); |
| for (auto input : current->inputs()) { |
| if (!visited[input->id()]) { |
| queue.push(input); |
| visited[input->id()] = true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |