Add support for subsections to the ELF assembler. Fixes PR8717.

Differential Revision: http://llvm-reviews.chandlerc.com/D598

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179725 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 549ab7f..1dff71a 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -197,6 +197,8 @@
   // actually a DW_LNE_end_sequence.
 
   // Switch to the section to be able to create a symbol at its end.
+  // TODO: keep track of the last subsection so that this symbol appears in the
+  // correct place.
   MCOS->SwitchSection(Section);
 
   MCContext &context = MCOS->getContext();
@@ -787,7 +789,7 @@
   if (Symbol->isTemporary())
     return;
   MCContext &context = MCOS->getContext();
-  if (context.getGenDwarfSection() != MCOS->getCurrentSection())
+  if (context.getGenDwarfSection() != MCOS->getCurrentSection().first)
     return;
 
   // The dwarf label's name does not have the symbol name's leading