[cpp] export isl_printer functionality

[ftynse]

It can fit a custom stream object, similarly to std::stringstream, which has state and can accept any relevant objects using operator <<. This way, it will be possible to configure the output formats of the isl_printer. The different between printer_to_file and printer_to_str can be resolved, e.g., with inheritance. It would be nice if printer_to_str behaved similarly to std::stringstream. Finally, callbacks accepting/returning a printer object can accept/return a stream object instead, which is compatible with C++ notion of a stream.

[tobiasgrosser]

Very interesting. I would like to see a modern printer interface for isl. Sven wanted to not directly expose the isl printer as he did not like the current design. It would be great to learn what kind of interface Sven has in mind.

[tobiasgrosser]

Or what kind of interface we would like to have.

[tobiasgrosser]

In fact Polly we just define operator<< using isl_*_to_str:

#define ADD_OSTREAM_PRINTER(name)                                              \
  inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,                  \
                                       const name &Obj) {                      \
    OS << Obj.to_str();                                                        \
    return OS;                                                                 \
  }

ADD_OSTREAM_PRINTER(isl::aff)
ADD_OSTREAM_PRINTER(isl::ast_expr)
ADD_OSTREAM_PRINTER(isl::ast_node)
ADD_OSTREAM_PRINTER(isl::basic_map)
ADD_OSTREAM_PRINTER(isl::basic_set)
ADD_OSTREAM_PRINTER(isl::map)
ADD_OSTREAM_PRINTER(isl::set)
ADD_OSTREAM_PRINTER(isl::id)
ADD_OSTREAM_PRINTER(isl::multi_aff)
ADD_OSTREAM_PRINTER(isl::multi_pw_aff)
ADD_OSTREAM_PRINTER(isl::multi_union_pw_aff)
ADD_OSTREAM_PRINTER(isl::point)
ADD_OSTREAM_PRINTER(isl::pw_aff)
ADD_OSTREAM_PRINTER(isl::schedule)
ADD_OSTREAM_PRINTER(isl::schedule_node)
ADD_OSTREAM_PRINTER(isl::space)
ADD_OSTREAM_PRINTER(isl::union_access_info)
ADD_OSTREAM_PRINTER(isl::union_flow)
ADD_OSTREAM_PRINTER(isl::union_set)
ADD_OSTREAM_PRINTER(isl::union_map)
ADD_OSTREAM_PRINTER(isl::union_pw_aff)
ADD_OSTREAM_PRINTER(isl::union_pw_multi_aff)

https://github.com/llvm-mirror/polly/blob/master/include/polly/Support/ISLOStream.h

[ftynse]

This sort of definitions can be auto-generated, I think, but it won't solve the callbacks problem.

[tobiasgrosser]

Sure, the Polly stuff is certainly not a complete interface.

Can you expand a little on the callback stuff. What exactly would you like / do you need?

[chandangreddy]

What we need is the AST printing functions exposed with the support for callbacks handling users node printing.