[PDB] Fix hash function used to write /src/headerblock

lld-link used to write PDB files that DIA couldn't recover natvis
files from if:

- The global strings table was > 64kiB
- There were at least 3 natvis files

The cause was that the hash function for the /src/headerblock stream
was incorrect: It needs to be truncated to 16 bit.

If the global strings table was <= 64kiB, truncating to 16 bit is a
no-op, so this wasn't needed for small programs.

If there are only 1 or 2 natvis files, then the growth strategy in
HashTable::grow() would mean the hash table would have 2 buckets (for 1
natvis file) or 4 buckets (for 4 natvis files), and since the hash
function is used modulo number of buckets, and since 2 and 4 divide
0x10000, the missing `% 0x10000` is a no-op there too. For 3 natvis
files, the hash table grows to 6 buckets, which has a factor that's not
common with 0x10000 and the difference starts to matter.

Fixes PR41626.

Differential Revision: https://reviews.llvm.org/D61277

llvm-svn: 359515

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h b/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
index e8f08c68cd3..86c43a482b8 100644
--- a/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
+++ b/llvm/include/llvm/DebugInfo/PDB/Native/HashTable.h
@@ -143,7 +143,7 @@ public:
       return EC;
     if (Present.intersects(Deleted))
       return make_error<RawError>(raw_error_code::corrupt_file,
-                                  "Present bit vector interesects deleted!");
+                                  "Present bit vector intersects deleted!");
 
     for (uint32_t P : Present) {
       if (auto EC = Stream.readInteger(Buckets[P].first))