Update MSVC compat docs about debug info.

[thakis]

docs/MSVCCompatibility.rst

80

I believe this is true?

[rnk]

docs/MSVCCompatibility.rst

80

You can actually pass -gdwarf to clang-cl to get DWARF. I'm not sure we need to say anything about what happens when you link with DWARF. We mostly want to say that you need to use link.exe to get PDBs today, and that we are working on PDBs in LLD.

[thakis]

docs/MSVCCompatibility.rst

80

Huh, it's not in /? output for some reason. Do you know why? Should we fix this? (I'll remove the reference to DWARF here)

[thakis]

no dwarf or gcc mode

[rnk]

docs/MSVCCompatibility.rst

77

Are these debuggers modern or are they just debuggers provided by Microsoft? It could be interpreted as a knock against gdb. Maybe we should say: "Windows debuggers that use the Microsoft DIA SDK, such as the Visual Studio debugger"?

[thakis]

docs/MSVCCompatibility.rst

77

Dunno, that was already here, I just kept it. Do they all use the DIA SDK? I thought one of them didn't (but I could be making that up)

[thakis]

reword slightly

[rnk]

Thanks!

docs/MSVCCompatibility.rst

77

I thought they did. Anyway, your wording is good.

[thakis]

r289712

docs/MSVCCompatibility.rst

 .. _/vm: http://msdn.microsoft.com/en-us/library/yad46a6z.aspx
 .. _pointer to a member of a virtual base class: http://llvm.org/PR15713
 
-* Debug info: :partial:`Minimal`.  Clang emits both CodeView line tables
-  (similar to what MSVC emits when given the ``/Z7`` flag) and DWARF debug
-  information into the object file.
-  Microsoft's link.exe will transform the CodeView line tables into a PDB,
-  enabling stack traces in all modern Windows debuggers.  Clang does not emit
-  any CodeView-compatible type info or description of variable layout.
-  Binaries linked with either binutils' ld or LLVM's lld should be usable with
-  GDB however sophisticated C++ expressions are likely to fail.
+* Debug info: :good:`Mostly complete`.  Clang emits relatively complete CodeView
+  debug information if ``/Z7`` or ``/Zi`` is passed. Microsoft's link.exe will
+  transform the CodeView debug information into a PDB that works in Windows
+  debuggers and other tools that consume PDB files like ETW. Work to teach lld
+  about CodeView and PDBs is ongoing.
 
 * RTTI: :good:`Complete`.  Generation of RTTI data structures has been
   finished, along with support for the ``/GR`` flag.