[Flang] Add user option -funderscoring/-fnounderscoring to control trailing underscore added to external names

This patch adds user option -funderscoring/-fnounderscoring  to control the trailing underscore being appended to external names (e.g. procedure names, common block names). The option in gfortran is documented in https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html.

Reviewed By: clementval

Differential Revision: https://reviews.llvm.org/D140795

1 files changed, 6 insertions, 0 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 08cb69d..9bccb7e 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -171,6 +171,12 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
     if (args.hasArg(clang::driver::options::OPT_pic_is_pie))
       opts.IsPIE = 1;
   }
+
+  // This option is compatible with -f[no-]underscoring in gfortran.
+  if (args.hasFlag(clang::driver::options::OPT_fno_underscoring,
+                   clang::driver::options::OPT_funderscoring, false)) {
+    opts.Underscoring = 0;
+  }
 }
 
 /// Parses all target input arguments and populates the target