forked from OSchip/llvm-project
269 lines
8.2 KiB
C++
269 lines
8.2 KiB
C++
//==- llvm/CodeGen/DwarfAccelTable.h - Dwarf Accelerator Tables --*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains support for writing dwarf accelerator tables.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFACCELTABLE_H
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#define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFACCELTABLE_H
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/BinaryFormat/Dwarf.h"
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#include "llvm/CodeGen/DIE.h"
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#include "llvm/CodeGen/DwarfStringPoolEntry.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Format.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cstddef>
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#include <cstdint>
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#include <vector>
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// The dwarf accelerator tables are an indirect hash table optimized
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// for null lookup rather than access to known data. They are output into
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// an on-disk format that looks like this:
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//
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// .-------------.
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// | HEADER |
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// |-------------|
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// | BUCKETS |
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// |-------------|
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// | HASHES |
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// |-------------|
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// | OFFSETS |
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// |-------------|
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// | DATA |
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// `-------------'
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//
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// where the header contains a magic number, version, type of hash function,
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// the number of buckets, total number of hashes, and room for a special
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// struct of data and the length of that struct.
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//
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// The buckets contain an index (e.g. 6) into the hashes array. The hashes
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// section contains all of the 32-bit hash values in contiguous memory, and
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// the offsets contain the offset into the data area for the particular
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// hash.
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//
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// For a lookup example, we could hash a function name and take it modulo the
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// number of buckets giving us our bucket. From there we take the bucket value
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// as an index into the hashes table and look at each successive hash as long
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// as the hash value is still the same modulo result (bucket value) as earlier.
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// If we have a match we look at that same entry in the offsets table and
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// grab the offset in the data for our final match.
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namespace llvm {
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class AsmPrinter;
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class DwarfDebug;
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class DwarfAccelTable {
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static uint32_t HashDJB(StringRef Str) {
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uint32_t h = 5381;
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for (unsigned i = 0, e = Str.size(); i != e; ++i)
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h = ((h << 5) + h) + Str[i];
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return h;
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}
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// Helper function to compute the number of buckets needed based on
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// the number of unique hashes.
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void ComputeBucketCount();
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struct TableHeader {
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uint32_t magic = MagicHash; // 'HASH' magic value to allow endian detection
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uint16_t version = 1; // Version number.
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uint16_t hash_function = dwarf::DW_hash_function_djb;
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// The hash function enumeration that was used.
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uint32_t bucket_count = 0; // The number of buckets in this hash table.
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uint32_t hashes_count = 0; // The total number of unique hash values
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// and hash data offsets in this table.
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uint32_t header_data_len; // The bytes to skip to get to the hash
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// indexes (buckets) for correct alignment.
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// Also written to disk is the implementation specific header data.
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static const uint32_t MagicHash = 0x48415348;
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TableHeader(uint32_t data_len) : header_data_len(data_len) {}
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#ifndef NDEBUG
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void print(raw_ostream &OS) {
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OS << "Magic: " << format("0x%x", magic) << "\n"
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<< "Version: " << version << "\n"
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<< "Hash Function: " << hash_function << "\n"
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<< "Bucket Count: " << bucket_count << "\n"
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<< "Header Data Length: " << header_data_len << "\n";
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}
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void dump() { print(dbgs()); }
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#endif
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};
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public:
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// The HeaderData describes the form of each set of data. In general this
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// is as a list of atoms (atom_count) where each atom contains a type
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// (AtomType type) of data, and an encoding form (form). In the case of
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// data that is referenced via DW_FORM_ref_* the die_offset_base is
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// used to describe the offset for all forms in the list of atoms.
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// This also serves as a public interface of sorts.
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// When written to disk this will have the form:
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//
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// uint32_t die_offset_base
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// uint32_t atom_count
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// atom_count Atoms
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// Make these public so that they can be used as a general interface to
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// the class.
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struct Atom {
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uint16_t type; // enum AtomType
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uint16_t form; // DWARF DW_FORM_ defines
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constexpr Atom(uint16_t type, uint16_t form) : type(type), form(form) {}
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#ifndef NDEBUG
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void print(raw_ostream &OS) {
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OS << "Type: " << dwarf::AtomTypeString(type) << "\n"
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<< "Form: " << dwarf::FormEncodingString(form) << "\n";
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}
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void dump() { print(dbgs()); }
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#endif
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};
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private:
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struct TableHeaderData {
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uint32_t die_offset_base;
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SmallVector<Atom, 3> Atoms;
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TableHeaderData(ArrayRef<Atom> AtomList, uint32_t offset = 0)
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: die_offset_base(offset), Atoms(AtomList.begin(), AtomList.end()) {}
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#ifndef NDEBUG
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void print(raw_ostream &OS) {
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OS << "die_offset_base: " << die_offset_base << "\n";
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for (size_t i = 0; i < Atoms.size(); i++)
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Atoms[i].print(OS);
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}
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void dump() { print(dbgs()); }
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#endif
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};
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// The data itself consists of a str_offset, a count of the DIEs in the
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// hash and the offsets to the DIEs themselves.
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// On disk each data section is ended with a 0 KeyType as the end of the
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// hash chain.
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// On output this looks like:
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// uint32_t str_offset
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// uint32_t hash_data_count
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// HashData[hash_data_count]
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public:
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struct HashDataContents {
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const DIE *Die; // Offsets
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char Flags; // Specific flags to output
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HashDataContents(const DIE *D, char Flags) : Die(D), Flags(Flags) {}
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#ifndef NDEBUG
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void print(raw_ostream &OS) const {
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OS << " Offset: " << Die->getOffset() << "\n"
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<< " Tag: " << dwarf::TagString(Die->getTag()) << "\n"
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<< " Flags: " << Flags << "\n";
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}
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#endif
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};
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private:
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// String Data
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struct DataArray {
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DwarfStringPoolEntryRef Name;
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std::vector<HashDataContents *> Values;
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};
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friend struct HashData;
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struct HashData {
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StringRef Str;
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uint32_t HashValue;
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MCSymbol *Sym;
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DwarfAccelTable::DataArray &Data; // offsets
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HashData(StringRef S, DwarfAccelTable::DataArray &Data)
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: Str(S), Data(Data) {
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HashValue = DwarfAccelTable::HashDJB(S);
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}
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#ifndef NDEBUG
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void print(raw_ostream &OS) {
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OS << "Name: " << Str << "\n";
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OS << " Hash Value: " << format("0x%x", HashValue) << "\n";
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OS << " Symbol: ";
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if (Sym)
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OS << *Sym;
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else
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OS << "<none>";
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OS << "\n";
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for (HashDataContents *C : Data.Values) {
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OS << " Offset: " << C->Die->getOffset() << "\n";
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OS << " Tag: " << dwarf::TagString(C->Die->getTag()) << "\n";
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OS << " Flags: " << C->Flags << "\n";
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}
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}
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void dump() { print(dbgs()); }
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#endif
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};
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// Internal Functions
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void EmitHeader(AsmPrinter *);
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void EmitBuckets(AsmPrinter *);
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void EmitHashes(AsmPrinter *);
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void emitOffsets(AsmPrinter *, const MCSymbol *);
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void EmitData(AsmPrinter *, DwarfDebug *D);
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// Allocator for HashData and HashDataContents.
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BumpPtrAllocator Allocator;
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// Output Variables
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TableHeader Header;
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TableHeaderData HeaderData;
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std::vector<HashData *> Data;
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using StringEntries = StringMap<DataArray, BumpPtrAllocator &>;
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StringEntries Entries;
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// Buckets/Hashes/Offsets
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using HashList = std::vector<HashData *>;
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using BucketList = std::vector<HashList>;
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BucketList Buckets;
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HashList Hashes;
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// Public Implementation
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public:
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DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom>);
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DwarfAccelTable(const DwarfAccelTable &) = delete;
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DwarfAccelTable &operator=(const DwarfAccelTable &) = delete;
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void AddName(DwarfStringPoolEntryRef Name, const DIE *Die, char Flags = 0);
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void FinalizeTable(AsmPrinter *, StringRef);
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void emit(AsmPrinter *, const MCSymbol *, DwarfDebug *);
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#ifndef NDEBUG
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void print(raw_ostream &OS);
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void dump() { print(dbgs()); }
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#endif
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};
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} // end namespace llvm
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#endif // LLVM_LIB_CODEGEN_ASMPRINTER_DWARFACCELTABLE_H
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