[flang] Produce proper "preprocessor output" for -E option

Rename the current -E option to "-E -Xflang -fno-reformat".

Add a new Parsing::EmitPreprocessedSource() routine to convert the
cooked character stream output of the prescanner back to something
more closely resembling output from a traditional preprocessor;
call this new routine when -E appears.

The new -E output is suitable for use as fixed form Fortran source to
compilation by (one hopes) any Fortran compiler.  If the original
top-level source file had been free form source, the output will be
suitable for use as free form source as well; otherwise there may be
diagnostics about missing spaces if they were indeed absent in the
original fixed form source.

Unless the -P option appears, #line directives are interspersed
with the output (but be advised, f18 will ignore these if presented
with them in a later compilation).

An effort has been made to preserve original alphabetic character case
and source indentation.

Add -P and -fno-reformat to the new drivers.

Tweak test options to avoid confusion with prior -E output; use
-fno-reformat where needed, but prefer to keep -E, sometimes
in concert with -P, on most, updating expected results accordingly.

Differential Revision: https://reviews.llvm.org/D106727

1 files changed, 2 insertions, 1 deletions

diff --git a/flang/lib/Parser/token-sequence.cpp b/flang/lib/Parser/token-sequence.cpp
index cdf066d..0a959f2 100644
--- a/flang/lib/Parser/token-sequence.cpp
+++ b/flang/lib/Parser/token-sequence.cpp
@@ -276,13 +276,14 @@ void TokenSequence::Emit(CookedSource &cooked) const {
   cooked.PutProvenanceMappings(provenances_);
 }
 
-void TokenSequence::Dump(llvm::raw_ostream &o) const {
+llvm::raw_ostream &TokenSequence::Dump(llvm::raw_ostream &o) const {
   o << "TokenSequence has " << char_.size() << " chars; nextStart_ "
     << nextStart_ << '\n';
   for (std::size_t j{0}; j < start_.size(); ++j) {
     o << '[' << j << "] @ " << start_[j] << " '" << TokenAt(j).ToString()
       << "'\n";
   }
+  return o;
 }
 
 Provenance TokenSequence::GetTokenProvenance(