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//===- PDBStringTableBuilder.cpp - PDB String Table -------------*- 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
//
//===----------------------------------------------------------------------===//
#include "llvm/DebugInfo/PDB/Native/PDBStringTableBuilder.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/DebugInfo/PDB/Native/Hash.h"
#include "llvm/DebugInfo/PDB/Native/RawTypes.h"
#include "llvm/Support/BinaryStreamWriter.h"
#include "llvm/Support/Endian.h"
#include <map>
using namespace llvm;
using namespace llvm::msf;
using namespace llvm::support;
using namespace llvm::support::endian;
using namespace llvm::pdb;
StringTableHashTraits::StringTableHashTraits(PDBStringTableBuilder &Table)
: Table(&Table) {}
uint32_t StringTableHashTraits::hashLookupKey(StringRef S) const {
// The reference implementation doesn't include code for /src/headerblock
// handling, but it can only read natvis entries lld's PDB files if
// this hash function truncates the hash to 16 bit.
// PDB/include/misc.h in the reference implementation has a hashSz() function
// that returns an unsigned short, that seems what's being used for
// /src/headerblock.
return static_cast<uint16_t>(Table->getIdForString(S));
}
StringRef StringTableHashTraits::storageKeyToLookupKey(uint32_t Offset) const {
return Table->getStringForId(Offset);
}
uint32_t StringTableHashTraits::lookupKeyToStorageKey(StringRef S) {
return Table->insert(S);
}
uint32_t PDBStringTableBuilder::insert(StringRef S) {
return Strings.insert(S);
}
uint32_t PDBStringTableBuilder::getIdForString(StringRef S) const {
return Strings.getIdForString(S);
}
StringRef PDBStringTableBuilder::getStringForId(uint32_t Id) const {
return Strings.getStringForId(Id);
}
static uint32_t computeBucketCount(uint32_t NumStrings) {
// This is a precomputed list of Buckets given the specified number of
// strings. Matching the reference algorithm exactly is not strictly
// necessary for correctness, but it helps when comparing LLD's PDBs with
// Microsoft's PDBs so as to eliminate superfluous differences.
// The reference implementation does (in nmt.h, NMT::grow()):
// unsigned StringCount = 0;
// unsigned BucketCount = 1;
// fn insert() {
// ++StringCount;
// if (BucketCount * 3 / 4 < StringCount)
// BucketCount = BucketCount * 3 / 2 + 1;
// }
// This list contains all StringCount, BucketCount pairs where BucketCount was
// just incremented. It ends before the first BucketCount entry where
// BucketCount * 3 would overflow a 32-bit unsigned int.
static std::map<uint32_t, uint32_t> StringsToBuckets = {
{0, 1},
{1, 2},
{2, 4},
{4, 7},
{6, 11},
{9, 17},
{13, 26},
{20, 40},
{31, 61},
{46, 92},
{70, 139},
{105, 209},
{157, 314},
{236, 472},
{355, 709},
{532, 1064},
{799, 1597},
{1198, 2396},
{1798, 3595},
{2697, 5393},
{4045, 8090},
{6068, 12136},
{9103, 18205},
{13654, 27308},
{20482, 40963},
{30723, 61445},
{46084, 92168},
{69127, 138253},
{103690, 207380},
{155536, 311071},
{233304, 466607},
{349956, 699911},
{524934, 1049867},
{787401, 1574801},
{1181101, 2362202},
{1771652, 3543304},
{2657479, 5314957},
{3986218, 7972436},
{5979328, 11958655},
{8968992, 17937983},
{13453488, 26906975},
{20180232, 40360463},
{30270348, 60540695},
{45405522, 90811043},
{68108283, 136216565},
{102162424, 204324848},
{153243637, 306487273},
{229865455, 459730910},
{344798183, 689596366},
{517197275, 1034394550},
{775795913, 1551591826},
{1163693870, 2327387740}};
auto Entry = StringsToBuckets.lower_bound(NumStrings);
assert(Entry != StringsToBuckets.end());
return Entry->second;
}
uint32_t PDBStringTableBuilder::calculateHashTableSize() const {
uint32_t Size = sizeof(uint32_t); // Hash table begins with 4-byte size field.
Size += sizeof(uint32_t) * computeBucketCount(Strings.size());
return Size;
}
uint32_t PDBStringTableBuilder::calculateSerializedSize() const {
uint32_t Size = 0;
Size += sizeof(PDBStringTableHeader);
Size += Strings.calculateSerializedSize();
Size += calculateHashTableSize();
Size += sizeof(uint32_t); // The /names stream ends with the string count.
return Size;
}
void PDBStringTableBuilder::setStrings(
const codeview::DebugStringTableSubsection &Strings) {
this->Strings = Strings;
}
Error PDBStringTableBuilder::writeHeader(BinaryStreamWriter &Writer) const {
// Write a header
PDBStringTableHeader H;
H.Signature = PDBStringTableSignature;
H.HashVersion = 1;
H.ByteSize = Strings.calculateSerializedSize();
if (auto EC = Writer.writeObject(H))
return EC;
assert(Writer.bytesRemaining() == 0);
return Error::success();
}
Error PDBStringTableBuilder::writeStrings(BinaryStreamWriter &Writer) const {
if (auto EC = Strings.commit(Writer))
return EC;
assert(Writer.bytesRemaining() == 0);
return Error::success();
}
Error PDBStringTableBuilder::writeHashTable(BinaryStreamWriter &Writer) const {
// Write a hash table.
uint32_t BucketCount = computeBucketCount(Strings.size());
if (auto EC = Writer.writeInteger(BucketCount))
return EC;
std::vector<ulittle32_t> Buckets(BucketCount);
for (auto &Pair : Strings) {
StringRef S = Pair.getKey();
uint32_t Offset = Pair.getValue();
uint32_t Hash = hashStringV1(S);
for (uint32_t I = 0; I != BucketCount; ++I) {
uint32_t Slot = (Hash + I) % BucketCount;
if (Buckets[Slot] != 0)
continue;
Buckets[Slot] = Offset;
break;
}
}
if (auto EC = Writer.writeArray(ArrayRef<ulittle32_t>(Buckets)))
return EC;
assert(Writer.bytesRemaining() == 0);
return Error::success();
}
Error PDBStringTableBuilder::writeEpilogue(BinaryStreamWriter &Writer) const {
if (auto EC = Writer.writeInteger<uint32_t>(Strings.size()))
return EC;
assert(Writer.bytesRemaining() == 0);
return Error::success();
}
Error PDBStringTableBuilder::commit(BinaryStreamWriter &Writer) const {
BinaryStreamWriter SectionWriter;
std::tie(SectionWriter, Writer) = Writer.split(sizeof(PDBStringTableHeader));
if (auto EC = writeHeader(SectionWriter))
return EC;
std::tie(SectionWriter, Writer) =
Writer.split(Strings.calculateSerializedSize());
if (auto EC = writeStrings(SectionWriter))
return EC;
std::tie(SectionWriter, Writer) = Writer.split(calculateHashTableSize());
if (auto EC = writeHashTable(SectionWriter))
return EC;
std::tie(SectionWriter, Writer) = Writer.split(sizeof(uint32_t));
if (auto EC = writeEpilogue(SectionWriter))
return EC;
return Error::success();
}
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