IMPLEMENTING FORTRAN STANDARDESE WITHIN LFORTRAN ROHIT GOSWAMI .and. ONDŘEJ ČERTÍK Created: 2021-09-24 Fri 01:14

BRIEF INTRODUCTION 3

HELLO! Find me here: Who? Rohit Goswami MInstP Doctoral Researcher, University of Iceland, Faculty of Physical Sciences https://rgoswami.me 4

LOGISTICS All contents are Slides are in presentations/fortranCon2021/gsocLFortran hosted on GitHub Questions are welcome anytime 5

LFORTRAN 7

INTRODUCTION Language Files Lines Code Comments Blanks C 3 1023 694 191 138 C Header 57 14237 11416 1041 1780 CMake 11 430 361 16 53 C++ 54 30745 26911 1560 2274 C++ Header 1 8938 8297 348 293 FORTRAN 20 1738 1344 174 220 Python 2 224 191 4 29 Total 148 57335 49214 3334 4787 8

STRUCTURE

FEATURES Runtime Libraries Pure Fortran | Impure ASR Guarantees compilation –> Wrappers Parser Currently almost all of F2018; including F77 LLVM Canonical backend, includes compile time evaluated expressions Jupyter Native execution as a kernel 10

REPRESENTATIONS 12

READING CODE I __attribute__((externally_visible)) main (integer(kind=4) argc, character(kind=1) * * argv) {integer(kind=4) D.3878; static integer(kind=4) options.1[7] = {2116, 4095, 0, 1, 1, 0, 31}; _gfortran_set_args (argc, argv); _gfortran_set_options (7, &options.1[0]); MAIN__ (); D.3878 = 0; return D.3878;} MAIN__ () {static integer(kind=4) i = 3; {struct __st_parameter_dt dt_parm.0; try {dt_parm.0.common.filename = &"hi.f90"[1]{lb: 1 sz: 1}; dt_parm.0.common.line = 3; dt_parm.0.common.flags = 128; dt_parm.0.common.unit = 6; _gfortran_st_write (&dt_parm.0); _gfortran_transfer_integer_write (&dt_parm.0, &i, 4); _gfortran_transfer_character_write (&dt_parm.0, &"Hello World"[1]{lb: 1 sz: 1}, 1 _gfortran_st_write_done (&dt_parm.0);} finally {dt_parm.0 = {CLOBBER};}}} GIMPLE is an internal gfortran representation… 13

READING CODE II AST on the left ASR on the right 14

READING CODE III program main integer :: i=3 print*, i, "Hello World" end program lfortran has a nicer intermediate structure conda create -n lf conda activate lf conda install lfortran \ -c conda-forge lfortran --show-asr hi.f90 15

FORTRAN AND STANDARDESE The ASR can be used to implement the standard verbatim 17

REAL DEFINITION

REAL ARGUMENTS if (func_name == "real") { if (args.n == 1) { ASR::expr_t* real_expr = args[0]; int real_kind = LFortran::ASRUtils::extract_kind_from_ttype_t (func_type); if (LFortran::ASR::is_a(*func_type)) { if (real_kind == 4){ float rr = ASR::down_cast (LFortran::ASRUtils::expr_value(real_expr))->m_r; value = ASR::down_cast (ASR::make_ConstantReal_t(al, x.base.base.loc, rr, func_type)); } else { double rr = ASR::down_cast (LFortran::ASRUtils::expr_value(real_expr))->m_r; value = ASR::down_cast (ASR::make_ConstantReal_t(al, x.base.base.loc, rr, func_type)); } } // TODO: Handle BOZ later } else { throw SemanticError("REAL must have only one argument", x.base.base.loc); } 19

INTEGER ARGUMENTS else if (LFortran::ASR::is_a(*func_type)) { if (real_kind == 4){ int64_t rv = ASR::down_cast( LFortran::ASRUtils::expr_value(real_expr))->m_n; float rr = static_cast(rv); value = ASR::down_cast (ASR::make_ConstantReal_t(al, x.base.base.loc, rr, func_type)); } else { double rr = static_cast(ASR::down_cast (LFortran::ASRUtils:: expr_value(real_expr))->m_n); value = ASR::down_cast (ASR::make_ConstantReal_t (al, x.base.base.loc, rr, func_type)); } } 20

CONCLUSIONS 22

OMITTED TOPICS Details here

THE END 25

ACKNOWLEDGEMENTS as my supervisor, as my co-supervisor, and my committee member at Los Alamos National Laboratory ( , and ) Family, pets, Groupmembers, audience Prof. Hannes Jónsson Prof. Birgir Hrafnkelsson Dr. Elvar Jonsson Dr. Ondřej Čertík Quansight Labs Dr. Ralf Gommers Dr. Melissa Weber Mendonça Dr. Pearu Peterson 26

THANKS! 27