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// Copyright 2018 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/constant-folding-reducer.h" #include "src/compiler/js-graph.h" #include "src/objects/objects-inl.h" namespace v8 { namespace internal { namespace compiler { ConstantFoldingReducer::ConstantFoldingReducer(Editor* editor, JSGraph* jsgraph, JSHeapBroker* broker) : AdvancedReducer(editor), jsgraph_(jsgraph), broker_(broker) {} ConstantFoldingReducer::~ConstantFoldingReducer() = default; Reduction ConstantFoldingReducer::Reduce(Node* node) { DisallowHeapAccess no_heap_access; // Check if the output type is a singleton. In that case we already know the // result value and can simply replace the node if it's eliminable. if (!NodeProperties::IsConstant(node) && NodeProperties::IsTyped(node) && node->op()->HasProperty(Operator::kEliminatable)) { // TODO(v8:5303): We must not eliminate FinishRegion here. This special // case can be removed once we have separate operators for value and // effect regions. if (node->opcode() == IrOpcode::kFinishRegion) return NoChange(); // We can only constant-fold nodes here, that are known to not cause any // side-effect, may it be a JavaScript observable side-effect or a possible // eager deoptimization exit (i.e. {node} has an operator that doesn't have // the Operator::kNoDeopt property). Type upper = NodeProperties::GetType(node); if (!upper.IsNone()) { Node* replacement = nullptr; if (upper.IsHeapConstant()) { replacement = jsgraph()->Constant(upper.AsHeapConstant()->Ref()); } else if (upper.Is(Type::MinusZero())) { Factory* factory = jsgraph()->isolate()->factory(); ObjectRef minus_zero(broker(), factory->minus_zero_value()); replacement = jsgraph()->Constant(minus_zero); } else if (upper.Is(Type::NaN())) { replacement = jsgraph()->NaNConstant(); } else if (upper.Is(Type::Null())) { replacement = jsgraph()->NullConstant(); } else if (upper.Is(Type::PlainNumber()) && upper.Min() == upper.Max()) { replacement = jsgraph()->Constant(upper.Min()); } else if (upper.Is(Type::Undefined())) { replacement = jsgraph()->UndefinedConstant(); } if (replacement) { // Make sure the node has a type. if (!NodeProperties::IsTyped(replacement)) { NodeProperties::SetType(replacement, upper); } ReplaceWithValue(node, replacement); return Changed(replacement); } } } return NoChange(); } } // namespace compiler } // namespace internal } // namespace v8