[DIA] Add IPDBSectionContrib interfaces and DIA implementation

To resolve symbol context at a particular address, we need to
determine the compiland for the address. We are able to determine
the parent compiland of PDBSymbolFunc, PDBSymbolTypeUDT,
PDBSymbolTypeEnum symbols indirectly through line information. 
However no such information is availabile for PDBSymbolData, 
i.e. variables.

The Section Contribution table from PDBs has information about
each compiland's contribution to sections by address. For example,
a piece of a contribution looks like,

  VA         RelativeVA  Sect No.  Offset    Length    Compiland
  14000087B0 000087B0    0001      000077B0  000000BB  exe_main.obj

So given an address, it's possible to determine its compiland with
this information.

llvm-svn: 328178

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Native/NativeSession.cpp b/llvm/lib/DebugInfo/PDB/Native/NativeSession.cpp
index c4d188ee337..d9f9552b7b9 100644
--- a/llvm/lib/DebugInfo/PDB/Native/NativeSession.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/NativeSession.cpp
@@ -260,3 +260,8 @@ std::unique_ptr<IPDBEnumInjectedSources>
 NativeSession::getInjectedSources() const {
   return nullptr;
 }
+
+std::unique_ptr<IPDBEnumSectionContribs>
+NativeSession::getSectionContribs() const {
+  return nullptr;
+}