[PDB] Move PDB functions to a separate file.

We are going to use the hash functions from TPI streams.

Differential Revision: http://reviews.llvm.org/D21142

llvm-svn: 272223

1 files changed, 77 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Raw/Hash.cpp b/llvm/lib/DebugInfo/PDB/Raw/Hash.cpp
new file mode 100644
index 0000000..8d327b3
--- /dev/null
+++ b/llvm/lib/DebugInfo/PDB/Raw/Hash.cpp
@@ -0,0 +1,77 @@
+//===- Hash.cpp - PDB Hash Functions --------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/PDB/Raw/Hash.h"
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::support;
+
+// Corresponds to `Hasher::lhashPbCb` in PDB/include/misc.h.
+// Used for name hash table and TPI/IPI hashes.
+uint32_t pdb::HashStringV1(StringRef Str) {
+  uint32_t Result = 0;
+  uint32_t Size = Str.size();
+
+  ArrayRef<ulittle32_t> Longs(reinterpret_cast<const ulittle32_t *>(Str.data()),
+                              Size / 4);
+
+  for (auto Value : Longs)
+    Result ^= Value;
+
+  const uint8_t *Remainder = reinterpret_cast<const uint8_t *>(Longs.end());
+  uint32_t RemainderSize = Size % 4;
+
+  // Maximum of 3 bytes left.  Hash a 2 byte word if possible, then hash the
+  // possibly remaining 1 byte.
+  if (RemainderSize >= 2) {
+    uint16_t Value = *reinterpret_cast<const ulittle16_t *>(Remainder);
+    Result ^= static_cast<uint32_t>(Value);
+    Remainder += 2;
+    RemainderSize -= 2;
+  }
+
+  // hash possible odd byte
+  if (RemainderSize == 1) {
+    Result ^= *(Remainder++);
+  }
+
+  const uint32_t toLowerMask = 0x20202020;
+  Result |= toLowerMask;
+  Result ^= (Result >> 11);
+
+  return Result ^ (Result >> 16);
+}
+
+// Corresponds to `HasherV2::HashULONG` in PDB/include/misc.h.
+// Used for name hash table.
+uint32_t pdb::HashStringV2(StringRef Str) {
+  uint32_t Hash = 0xb170a1bf;
+
+  ArrayRef<char> Buffer(Str.begin(), Str.end());
+
+  ArrayRef<ulittle32_t> Items(
+      reinterpret_cast<const ulittle32_t *>(Buffer.data()),
+      Buffer.size() / sizeof(ulittle32_t));
+  for (ulittle32_t Item : Items) {
+    Hash += Item;
+    Hash += (Hash << 10);
+    Hash ^= (Hash >> 6);
+  }
+  Buffer = Buffer.slice(Items.size() * sizeof(ulittle32_t));
+  for (uint8_t Item : Buffer) {
+    Hash += Item;
+    Hash += (Hash << 10);
+    Hash ^= (Hash >> 6);
+  }
+
+  return Hash * 1664525L + 1013904223L;
+}