Add Swift enumerator value for CodeView::SourceLanguage

[lanza]

Summary

Swift now generates PDBs for debugging on Windows. llvm and lldb
need a language type to properly handle the output emitted by swiftc.

[compnerd]

include/llvm/DebugInfo/CodeView/CodeView.h

161

I would say we should push this further down in case Microsoft adds a new language. Why not follow D's lead and use S?

[rnk]

In the absence of guidance from someone at Microsoft, I would suggest not using 0x11, as they have probably already allocated that to some other language. I'd recommend doing what the D language people did and grab 'S'. If VS ever does something with this info, be aware that you will probably want to change which value we use here.

[lanza]

Change value to 'S'

[lanza]

Sounds good to me. Are there any MSFT people we can tag to get feedback for this?

[smeenai]

include/llvm/DebugInfo/CodeView/CodeView.h

165

I'd either update the existing comment about D or add a new one for Swift.

[lanza]

shobot

[rnk]

lgtm, but surely you want to add this to the MapDWLangToCVLang in CodeViewDebug.cpp as well, and perhaps add a test for it.

[aganea]

In D58415#1404674, @lanza wrote:

Sounds good to me. Are there any MSFT people we can tag to get feedback for this?

Poke @neerajksingh @CJHebert

include/llvm/DebugInfo/CodeView/CodeView.h

enum SourceLanguage : uint8_t {
   Cvtpgd = 0x09,
   CSharp = 0x0a,
   VB = 0x0b,
   ILAsm = 0x0c,
   Java = 0x0d,
   JScript = 0x0e,
   MSIL = 0x0f,
   HLSL = 0x10,
 
-  /// The DMD compiler emits 'D' for the CV source language. Microsoft doesn't
-  /// have an enumerator for it yet.
+  /// The DMD & Swift compilers emit 'D' and 'S', respectively, for the CV
+  /// source language. Microsoft does not have enumerators for them yet.
   D = 'D',
+  Swift = 'S',
 };
 
 /// These values correspond to the CV_call_e enumeration, and are documented
 /// at the following locations:
 ///   https://msdn.microsoft.com/en-us/library/b2fc64ek.aspx
 ///   https://msdn.microsoft.com/en-us/library/windows/desktop/ms680207(v=vs.85).aspx
 ///
 enum class CallingConvention : uint8_t {