284 lines
9.0 KiB
C
284 lines
9.0 KiB
C
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//==-- 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 CODEGEN_ASMPRINTER_DWARFACCELTABLE_H__
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#define CODEGEN_ASMPRINTER_DWARFACCELTABLE_H__
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#include "llvm/ADT/StringMap.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/Dwarf.h"
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#include "llvm/Support/DataTypes.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/Format.h"
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#include "llvm/Support/FormattedStream.h"
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#include "DIE.h"
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#include <vector>
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#include <map>
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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 DIE;
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class DwarfDebug;
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class DwarfAccelTable {
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enum HashFunctionType {
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eHashFunctionDJB = 0u
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};
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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 (void);
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struct TableHeader {
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uint32_t magic; // 'HASH' magic value to allow endian detection
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uint16_t version; // Version number.
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uint16_t hash_function; // The hash function enumeration that was used.
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uint32_t bucket_count; // The number of buckets in this hash table.
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uint32_t hashes_count; // 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) :
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magic (MagicHash), version (1), hash_function (eHashFunctionDJB),
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bucket_count (0), hashes_count (0), header_data_len (data_len)
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{}
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#ifndef NDEBUG
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void print(raw_ostream &O) {
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O << "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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enum AtomType {
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eAtomTypeNULL = 0u,
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eAtomTypeDIEOffset = 1u, // DIE offset, check form for encoding
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eAtomTypeCUOffset = 2u, // DIE offset of the compiler unit header that
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// contains the item in question
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eAtomTypeTag = 3u, // DW_TAG_xxx value, should be encoded as
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// DW_FORM_data1 (if no tags exceed 255) or
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// DW_FORM_data2.
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eAtomTypeNameFlags = 4u, // Flags from enum NameFlags
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eAtomTypeTypeFlags = 5u // Flags from enum TypeFlags
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};
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enum TypeFlags {
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eTypeFlagClassMask = 0x0000000fu,
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// Always set for C++, only set for ObjC if this is the
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// @implementation for a class.
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eTypeFlagClassIsImplementation = ( 1u << 1 )
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};
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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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AtomType type; // enum AtomType
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uint16_t form; // DWARF DW_FORM_ defines
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Atom(AtomType type, uint16_t form) : type(type), form(form) {}
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static const char * AtomTypeString(enum AtomType);
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#ifndef NDEBUG
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void print(raw_ostream &O) {
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O << "Type: " << AtomTypeString(type) << "\n"
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<< "Form: " << dwarf::FormEncodingString(form) << "\n";
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}
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void dump() {
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print(dbgs());
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}
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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, 1> 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 &O) {
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O << "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(O);
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}
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void dump() {
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print(dbgs());
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}
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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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DIE *Die; // Offsets
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char Flags; // Specific flags to output
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HashDataContents(DIE *D, char Flags) :
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Die(D),
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Flags(Flags) { }
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#ifndef NDEBUG
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void print(raw_ostream &O) const {
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O << " Offset: " << Die->getOffset() << "\n";
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O << " Tag: " << dwarf::TagString(Die->getTag()) << "\n";
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O << " 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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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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ArrayRef<HashDataContents*> Data; // offsets
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HashData(StringRef S, ArrayRef<HashDataContents*> 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 &O) {
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O << "Name: " << Str << "\n";
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O << " Hash Value: " << format("0x%x", HashValue) << "\n";
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O << " Symbol: " ;
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if (Sym) Sym->print(O);
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else O << "<none>";
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O << "\n";
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for (size_t i = 0; i < Data.size(); i++) {
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O << " Offset: " << Data[i]->Die->getOffset() << "\n";
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O << " Tag: " << dwarf::TagString(Data[i]->Die->getTag()) << "\n";
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O << " Flags: " << Data[i]->Flags << "\n";
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}
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}
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void dump() {
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print(dbgs());
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}
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#endif
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};
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DwarfAccelTable(const DwarfAccelTable&); // DO NOT IMPLEMENT
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void operator=(const DwarfAccelTable&); // DO NOT IMPLEMENT
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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 *, 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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// String Data
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typedef std::vector<HashDataContents*> DataArray;
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typedef StringMap<DataArray, BumpPtrAllocator&> StringEntries;
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StringEntries Entries;
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// Buckets/Hashes/Offsets
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typedef std::vector<HashData*> HashList;
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typedef std::vector<HashList> BucketList;
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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();
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void AddName(StringRef, DIE*, char = 0);
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void FinalizeTable(AsmPrinter *, const char *);
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void Emit(AsmPrinter *, MCSymbol *, DwarfDebug *);
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#ifndef NDEBUG
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void print(raw_ostream &O);
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void dump() { print(dbgs()); }
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#endif
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};
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}
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#endif
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