[PDB] Fix a bug where we were serializing hash tables incorrectly.

There was some code that tried to calculate the number of 4-byte
words required to hold N bits, but it was instead computing the
number of bytes required to hold N bits.  This was leading to
extraneous data being output into the hash table, which would
cause certain operations in DIA (the Microsoft PDB reader) to
fail.

llvm-svn: 327675

2 files changed, 16 insertions, 7 deletions

diff --git a/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h b/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
index 907f5ba1a3f..6361c4b76ba 100644
--- a/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
+++ b/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
@@ -161,16 +161,23 @@ public:
   uint32_t calculateSerializedLength() const {
     uint32_t Size = sizeof(Header);
 
+    constexpr int BitsPerWord = 8 * sizeof(uint32_t);
+
     int NumBitsP = Present.find_last() + 1;
     int NumBitsD = Deleted.find_last() + 1;
 
-    // Present bit set number of words, followed by that many actual words.
+    uint32_t NumWordsP = alignTo(NumBitsP, BitsPerWord) / BitsPerWord;
+    uint32_t NumWordsD = alignTo(NumBitsD, BitsPerWord) / BitsPerWord;
+
+    // Present bit set number of words (4 bytes), followed by that many actual
+    // words (4 bytes each).
     Size += sizeof(uint32_t);
-    Size += alignTo(NumBitsP, sizeof(uint32_t));
+    Size += NumWordsP * sizeof(uint32_t);
 
-    // Deleted bit set number of words, followed by that many actual words.
+    // Deleted bit set number of words (4 bytes), followed by that many actual
+    // words (4 bytes each).
     Size += sizeof(uint32_t);
-    Size += alignTo(NumBitsD, sizeof(uint32_t));
+    Size += NumWordsD * sizeof(uint32_t);
 
     // One (Key, ValueT) pair for each entry Present.
     Size += (sizeof(uint32_t) + sizeof(ValueT)) * size();
diff --git a/llvm/lib/DebugInfo/PDB/Native/HashTable.cpp b/llvm/lib/DebugInfo/PDB/Native/HashTable.cpp
index 5ed0acc8fd7..cfabc9cd1ad 100644
--- a/llvm/lib/DebugInfo/PDB/Native/HashTable.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/HashTable.cpp
@@ -46,16 +46,18 @@ Error llvm::pdb::readSparseBitVector(BinaryStreamReader &Stream,
 
 Error llvm::pdb::writeSparseBitVector(BinaryStreamWriter &Writer,
                                       SparseBitVector<> &Vec) {
+  constexpr int BitsPerWord = 8 * sizeof(uint32_t);
+
   int ReqBits = Vec.find_last() + 1;
-  uint32_t NumWords = alignTo(ReqBits, sizeof(uint32_t)) / sizeof(uint32_t);
-  if (auto EC = Writer.writeInteger(NumWords))
+  uint32_t ReqWords = alignTo(ReqBits, BitsPerWord) / BitsPerWord;
+  if (auto EC = Writer.writeInteger(ReqWords))
     return joinErrors(
         std::move(EC),
         make_error<RawError>(raw_error_code::corrupt_file,
                              "Could not write linear map number of words"));
 
   uint32_t Idx = 0;
-  for (uint32_t I = 0; I != NumWords; ++I) {
+  for (uint32_t I = 0; I != ReqWords; ++I) {
     uint32_t Word = 0;
     for (uint32_t WordIdx = 0; WordIdx < 32; ++WordIdx, ++Idx) {
       if (Vec.test(Idx))