[CodeView] Align type records on 4-bytes when emitting PDBs

When emitting PDBs, the TypeStreamMerger class is used to merge .debug$T records from the input .OBJ files into the output .PDB stream.
Records in .OBJs are not required to be aligned on 4-bytes, and "The Netwide Assembler 2.14" generates non-aligned records.

When compiling with -DLLVM_ENABLE_ASSERTIONS=ON, an assert was triggered in MergingTypeTableBuilder when non-ghash merging was used.
With ghash merging there was no assert.
As a result, LLD could potentially generate a non-aligned TPI stream.

We now align records on 4-bytes when record indices are remapped, in TypeStreamMerger::remapIndices().

Differential Revision: https://reviews.llvm.org/D75081

(cherry picked from commit a7325298e1f311b383b8ce5ba8e2d3698fef472a)

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/include/llvm/DebugInfo/CodeView/GlobalTypeTableBuilder.h b/llvm/include/llvm/DebugInfo/CodeView/GlobalTypeTableBuilder.h
index 3b103c22770..bb8cc032e28 100644
--- a/llvm/include/llvm/DebugInfo/CodeView/GlobalTypeTableBuilder.h
+++ b/llvm/include/llvm/DebugInfo/CodeView/GlobalTypeTableBuilder.h
@@ -71,6 +71,11 @@ public:
   template <typename CreateFunc>
   TypeIndex insertRecordAs(GloballyHashedType Hash, size_t RecordSize,
                            CreateFunc Create) {
+    assert(RecordSize < UINT32_MAX && "Record too big");
+    assert(RecordSize % 4 == 0 &&
+           "RecordSize is not a multiple of 4 bytes which will cause "
+           "misalignment in the output TPI stream!");
+
     auto Result = HashedRecords.try_emplace(Hash, nextTypeIndex());
 
     if (LLVM_UNLIKELY(Result.second /*inserted*/ ||