[MSVC] Turn C++ EH on my default

Our support for C++ EH is sufficiently good that it makes sense to
enable support for it out of the box.

While we are here, update the MSVCCompatibility doc.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@261195 91177308-0d34-0410-b5e6-96231b3b80d8

docs/MSVCCompatibility.rst

@@ -84,18 +84,23 @@ The status of major ABI-impacting C++ features:
 * RTTI: :good:`Complete`.  Generation of RTTI data structures has been
   finished, along with support for the ``/GR`` flag.
 
-* Exceptions and SEH: :partial:`Partial`.
+* C++ Exceptions: :good:`Mostly complete`.  Support for
-  C++ exceptions (``try`` / ``catch`` / ``throw``) and
+  C++ exceptions (``try`` / ``catch`` / ``throw``) have been implemented for
-  structured exceptions (``__try`` / ``__except`` / ``__finally``) mostly
+  x86 and x64.  Our implementation has been well tested but we still get the
-  work on x64. 32-bit exception handling support is being worked on.  LLVM does
+  odd bug report now and again.
-  not model asynchronous exceptions, so it is currently impossible to catch an
-  asynchronous exception generated in the same frame as the catching ``__try``.
   C++ exception specifications are ignored, but this is `consistent with Visual
   C++`_.
 
 .. _consistent with Visual C++:
   https://msdn.microsoft.com/en-us/library/wfa0edys.aspx
 
+* Asynchronous Exceptions (SEH): :partial:`Partial`.
+  Structured exceptions (``__try`` / ``__except`` / ``__finally``) mostly
+  work on x86 and x64.
+  LLVM does not model asynchronous exceptions, so it is currently impossible to
+  catch an asynchronous exception generated in the same frame as the catching
+  ``__try``.
+
 * Thread-safe initialization of local statics: :good:`Complete`.  MSVC 2015
   added support for thread-safe initialization of such variables by taking an
   ABI break.

lib/Driver/Tools.cpp

@@ -2410,11 +2410,9 @@ static void addExceptionArgs(const ArgList &Args, types::ID InputType,
   }
 
   if (types::isCXX(InputType)) {
-    // Disable C++ EH by default on XCore, PS4, and MSVC.
+    // Disable C++ EH by default on XCore and PS4.
-    // FIXME: Remove MSVC from this list once things work.
+    bool CXXExceptionsEnabled =
-    bool CXXExceptionsEnabled = Triple.getArch() != llvm::Triple::xcore &&
+        Triple.getArch() != llvm::Triple::xcore && !Triple.isPS4CPU();
-                                !Triple.isPS4CPU() &&
-                                !Triple.isWindowsMSVCEnvironment();
     Arg *ExceptionArg = Args.getLastArg(
         options::OPT_fcxx_exceptions, options::OPT_fno_cxx_exceptions,
         options::OPT_fexceptions, options::OPT_fno_exceptions);