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39f8965325
The dummy WitnessTableEntry for the protocol conformance descriptor was used to ensure that the witness indices were offset by 1 (to account for the protocol conformance descriptor), but it led to some odd index adjustments. Instead, make the index adjustments explicit when we're passing a WitnessIndex off to be loaded for a witness table.
57 lines
1.8 KiB
C++
57 lines
1.8 KiB
C++
//===--- WitnessIndex.h - Index into a witness table ------------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the WitnessIndex type, used for drilling into a
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// protocol witness table or value witness table.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_IRGEN_WITNESSINDEX_H
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#define SWIFT_IRGEN_WITNESSINDEX_H
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#include "swift/ABI/MetadataValues.h"
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#include "swift/IRGen/ValueWitness.h"
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namespace swift {
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namespace irgen {
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/// A class which encapsulates an index into a witness table.
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class WitnessIndex {
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// Negative values are indexing into the private area of a protocol witness
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// table.
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int Value : 31;
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unsigned IsPrefix : 1;
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public:
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WitnessIndex() = default;
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WitnessIndex(ValueWitness index) : Value(int(index)) {}
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explicit WitnessIndex(int index, bool isPrefix)
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: Value(index), IsPrefix(isPrefix) {}
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int getValue() const { return Value; }
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bool isPrefix() const { return IsPrefix; }
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/// Adjust the index to refer into a protocol witness table (rather than
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/// a value witness table).
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WitnessIndex forProtocolWitnessTable() const {
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int NewValue = Value < 0
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? Value
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: Value + WitnessTableFirstRequirementOffset;
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return WitnessIndex(NewValue, IsPrefix);
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}
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};
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} // end namespace irgen
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} // end namespace swift
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#endif
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