Use dwarf-2 by default on OpenBSD and FreeBSD.

The Tools.cpp part of the patch partially based on a patch from
FreeBSD's LLVM tree.

llvm-svn: 210883
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index d4ce04a..0df398b 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2885,8 +2885,10 @@
       // FIXME: we should support specifying dwarf version with
       // -gline-tables-only.
       CmdArgs.push_back("-gline-tables-only");
-      // Default is dwarf-2 for darwin.
-      if (getToolChain().getTriple().isOSDarwin())
+      // Default is dwarf-2 for Darwin, OpenBSD and FreeBSD.
+      const llvm::Triple &Triple = getToolChain().getTriple();
+      if (Triple.isOSDarwin() || Triple.getOS() == llvm::Triple::OpenBSD ||
+          Triple.getOS() == llvm::Triple::FreeBSD)
         CmdArgs.push_back("-gdwarf-2");
     } else if (A->getOption().matches(options::OPT_gdwarf_2))
       CmdArgs.push_back("-gdwarf-2");
@@ -2896,8 +2898,10 @@
       CmdArgs.push_back("-gdwarf-4");
     else if (!A->getOption().matches(options::OPT_g0) &&
              !A->getOption().matches(options::OPT_ggdb0)) {
-      // Default is dwarf-2 for darwin.
-      if (getToolChain().getTriple().isOSDarwin())
+      // Default is dwarf-2 for Darwin, OpenBSD and FreeBSD.
+      const llvm::Triple &Triple = getToolChain().getTriple();
+      if (Triple.isOSDarwin() || Triple.getOS() == llvm::Triple::OpenBSD ||
+          Triple.getOS() == llvm::Triple::FreeBSD)
         CmdArgs.push_back("-gdwarf-2");
       else
         CmdArgs.push_back("-g");