1 files changed, 229 insertions, 0 deletions
diff --git a/llvm/lib/DebugInfo/PDB/Native/PDBStringTableBuilder.cpp b/llvm/lib/DebugInfo/PDB/Native/PDBStringTableBuilder.cpp
new file mode 100644
index 000000000000..f7f36901e4d4
--- /dev/null
+++ b/llvm/lib/DebugInfo/PDB/Native/PDBStringTableBuilder.cpp
@@ -0,0 +1,229 @@
+//===- 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();
+}