// Copyright 2018 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "src/compiler/constant-folding-reducer.h"
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#include "src/compiler/js-graph.h"
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#include "src/objects-inl.h"
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namespace v8 {
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namespace internal {
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namespace compiler {
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ConstantFoldingReducer::ConstantFoldingReducer(Editor* editor, JSGraph* jsgraph,
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JSHeapBroker* js_heap_broker)
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: AdvancedReducer(editor),
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jsgraph_(jsgraph),
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js_heap_broker_(js_heap_broker) {}
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ConstantFoldingReducer::~ConstantFoldingReducer() {}
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Reduction ConstantFoldingReducer::Reduce(Node* node) {
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DisallowHeapAccess no_heap_access;
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// Check if the output type is a singleton. In that case we already know the
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// result value and can simply replace the node if it's eliminable.
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if (!NodeProperties::IsConstant(node) && NodeProperties::IsTyped(node) &&
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node->op()->HasProperty(Operator::kEliminatable)) {
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// TODO(v8:5303): We must not eliminate FinishRegion here. This special
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// case can be removed once we have separate operators for value and
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// effect regions.
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if (node->opcode() == IrOpcode::kFinishRegion) return NoChange();
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// We can only constant-fold nodes here, that are known to not cause any
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// side-effect, may it be a JavaScript observable side-effect or a possible
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// eager deoptimization exit (i.e. {node} has an operator that doesn't have
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// the Operator::kNoDeopt property).
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Type upper = NodeProperties::GetType(node);
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if (!upper.IsNone()) {
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Node* replacement = nullptr;
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if (upper.IsHeapConstant()) {
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replacement = jsgraph()->Constant(upper.AsHeapConstant()->Ref());
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} else if (upper.Is(Type::MinusZero())) {
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Factory* factory = jsgraph()->isolate()->factory();
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ObjectRef minus_zero(js_heap_broker(), factory->minus_zero_value());
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replacement = jsgraph()->Constant(minus_zero);
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} else if (upper.Is(Type::NaN())) {
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replacement = jsgraph()->NaNConstant();
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} else if (upper.Is(Type::Null())) {
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replacement = jsgraph()->NullConstant();
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} else if (upper.Is(Type::PlainNumber()) && upper.Min() == upper.Max()) {
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replacement = jsgraph()->Constant(upper.Min());
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} else if (upper.Is(Type::Undefined())) {
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replacement = jsgraph()->UndefinedConstant();
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}
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if (replacement) {
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// Make sure the node has a type.
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if (!NodeProperties::IsTyped(replacement)) {
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NodeProperties::SetType(replacement, upper);
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}
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ReplaceWithValue(node, replacement);
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return Changed(replacement);
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}
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}
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}
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return NoChange();
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}
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} // namespace compiler
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} // namespace internal
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} // namespace v8
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