nim_svdpi.org

Step 1: Nim to libdpi.so

nim c --out:libdpi.so --app:lib libdpi.nim

Step 2: Compile SystemVerilog as usual

xrun -sv -64bit tb.sv

Files

tb.sv

program top;

  import "DPI-C" hello=task hello();

  initial begin
    hello();
  end

endprogram

libdpi.nim

proc hello() {.exportc, dynlib.} =
  echo "Hello from Nim!"

Datatype Translation

SystemVerilog	C	Nim
byte	char	byte or char or uint8
int	int	cint or int32
longint	long long	clonglong or int64
shortint	short int	cshort or int16
real	double	cdouble or float64
shortreal	float	cfloat or float32
chandle	void*	pointer or ptr T
string	char*	cstring

Imports

Tasks

• A Nim proc mapped to a SV task needs to have an cint return type, and it should return a value of 0 (default) or 1.

  Failure to do so will give this error:

  xmsim: *F,INVDIS: The import task import_task returned a value other than 1 or 0.
      

Context

If an imported function/task is calling an exported function/task, that import declaration must contain the context keyword.

Example:

export "DPI-C" function export_func;
import "DPI-C" context function void import_func_calling_export_func();
// ..

If that context keyword is left you, you get an error like:

xmsim: *E,NONCONI: The C identifier "export_func" representing an
export task/function cannot be executed from a non-context import
task/function.

Exports

If a function or task name foo is exported from SystemVerilog to a C function (Nim proc), it needs to be declared in the Nim code as:

proc foo() {.importc.} # Assuming that foo has no arguments and has void return type