[DebugInfo] Add calling convention support for DWARF and CodeView

Summary:
Now DISubroutineType has a 'cc' field which should be a DW_CC_ enum.  If
it is present and non-zero, the backend will emit it as a
DW_AT_calling_convention attribute. On the CodeView side, we translate
it to the appropriate enum for the LF_PROCEDURE record.

I added a new LLVM vendor specific enum to the list of DWARF calling
conventions. DWARF does not appear to attempt to standardize these, so I
assume it's OK to do this until we coordinate with GCC on how to emit
vectorcall convention functions.

Reviewers: dexonsmith, majnemer, aaboud, amccarth

Subscribers: mehdi_amini, llvm-commits

Differential Revision: http://reviews.llvm.org/D21114

llvm-svn: 272197

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1467,6 +1467,7 @@ void ModuleBitcodeWriter::writeDISubroutineType(
   Record.push_back(HasNoOldTypeRefs | (unsigned)N->isDistinct());
   Record.push_back(N->getFlags());
   Record.push_back(VE.getMetadataOrNullID(N->getTypeArray().get()));
+  Record.push_back(N->getCC());
 
   Stream.EmitRecord(bitc::METADATA_SUBROUTINE_TYPE, Record, Abbrev);
   Record.clear();