Reorganize predefined macros for all Windows targets.

This adds an option to set the _MSC_VER macro without
recompiling. This is very useful when testing compatibility
with the Windows SDK and c++stdlib headers.

-fmsc-version=<version> (defaults to VS2003 (1300))

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116999 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index d4ba92c..021c7cb 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1314,6 +1314,18 @@
                    getToolChain().getTriple().getOS() == llvm::Triple::Win32))
     CmdArgs.push_back("-fms-extensions");
 
+  // -fmsc-version=1300 is default.
+  if (Args.hasFlag(options::OPT_fms_extensions, options::OPT_fno_ms_extensions,
+                   getToolChain().getTriple().getOS() == llvm::Triple::Win32) ||
+      Args.hasArg(options::OPT_fmsc_version)) {
+    llvm::StringRef msc_ver = Args.getLastArgValue(options::OPT_fmsc_version);
+    if (msc_ver.empty())
+      CmdArgs.push_back("-fmsc-version=1300");
+    else
+      CmdArgs.push_back(Args.MakeArgString("-fmsc-version=" + msc_ver));
+  }
+
+
   // -fborland-extensions=0 is default.
   if (Args.hasFlag(options::OPT_fborland_extensions,
                    options::OPT_fno_borland_extensions, false))