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//===- llvm/CodeGen/DwarfStringPoolEntry.h - String pool entry --*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_DWARFSTRINGPOOLENTRY_H
#define LLVM_CODEGEN_DWARFSTRINGPOOLENTRY_H
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/StringMap.h"
namespace llvm {
class MCSymbol;
/// Data for a string pool entry.
struct DwarfStringPoolEntry {
static constexpr unsigned NotIndexed = -1;
MCSymbol *Symbol = nullptr;
uint64_t Offset = 0;
unsigned Index = 0;
bool isIndexed() const { return Index != NotIndexed; }
};
/// DwarfStringPoolEntry with string keeping externally.
struct DwarfStringPoolEntryWithExtString : public DwarfStringPoolEntry {
StringRef String;
};
/// DwarfStringPoolEntryRef: Dwarf string pool entry reference.
///
/// Dwarf string pool entry keeps string value and its data.
/// There are two variants how data are represented:
///
/// 1. String data in pool - StringMapEntry<DwarfStringPoolEntry>.
/// 2. External string data - DwarfStringPoolEntryWithExtString.
///
/// The external data variant allows reducing memory usage for the case
/// when string pool entry does not have data: string entry does not
/// keep any data and so no need to waste space for the full
/// DwarfStringPoolEntry. It is recommended to use external variant if not all
/// entries of dwarf string pool have corresponding DwarfStringPoolEntry.
class DwarfStringPoolEntryRef {
/// Pointer type for "By value" string entry.
using ByValStringEntryPtr = const StringMapEntry<DwarfStringPoolEntry> *;
/// Pointer type for external string entry.
using ExtStringEntryPtr = const DwarfStringPoolEntryWithExtString *;
/// Pointer to the dwarf string pool Entry.
PointerUnion<ByValStringEntryPtr, ExtStringEntryPtr> MapEntry = nullptr;
public:
DwarfStringPoolEntryRef() = default;
/// ASSUMPTION: DwarfStringPoolEntryRef keeps pointer to \p Entry,
/// thus specified entry mustn`t be reallocated.
DwarfStringPoolEntryRef(const StringMapEntry<DwarfStringPoolEntry> &Entry)
: MapEntry(&Entry) {}
/// ASSUMPTION: DwarfStringPoolEntryRef keeps pointer to \p Entry,
/// thus specified entry mustn`t be reallocated.
DwarfStringPoolEntryRef(const DwarfStringPoolEntryWithExtString &Entry)
: MapEntry(&Entry) {}
explicit operator bool() const { return !MapEntry.isNull(); }
/// \returns symbol for the dwarf string.
MCSymbol *getSymbol() const {
assert(getEntry().Symbol && "No symbol available!");
return getEntry().Symbol;
}
/// \returns offset for the dwarf string.
uint64_t getOffset() const { return getEntry().Offset; }
/// \returns index for the dwarf string.
unsigned getIndex() const {
assert(getEntry().isIndexed() && "Index is not set!");
return getEntry().Index;
}
/// \returns string.
StringRef getString() const {
if (isa<ByValStringEntryPtr>(MapEntry))
return cast<ByValStringEntryPtr>(MapEntry)->first();
return cast<ExtStringEntryPtr>(MapEntry)->String;
}
/// \returns the entire string pool entry for convenience.
const DwarfStringPoolEntry &getEntry() const {
if (isa<ByValStringEntryPtr>(MapEntry))
return cast<ByValStringEntryPtr>(MapEntry)->second;
return *cast<ExtStringEntryPtr>(MapEntry);
}
bool operator==(const DwarfStringPoolEntryRef &X) const {
return MapEntry.getOpaqueValue() == X.MapEntry.getOpaqueValue();
}
bool operator!=(const DwarfStringPoolEntryRef &X) const {
return MapEntry.getOpaqueValue() != X.MapEntry.getOpaqueValue();
}
};
} // end namespace llvm
#endif
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