[Iverilog-devel] vpi_put_value

[fuyong <fuy...@gm...>]

Hi,

This is a test in Stuart Sutherland's PLI handbook, and it works well with
commercial tools. In Iverilog, we can have compile done, but run time show:

$pow(2, 3) returns 8
Unsupported format 6.
vvp: vpi_tasks.cc:179:virtual __vpiHandle*
sysfunc_real::vpi_put_value(p_vpi_value, int): Assertion `0` failed.

There are two $pow() calls .First one returns correct result, second one
failed. with vpi_print, we find seems like the first pow() did not even
called  our defined function (might be using the $pow in build-in $pow()?).
Any way, "result" is defined as int, not sure why the assertion is trigger
in run time.



=== Verilog side:
  initial
    begin
      a = 1;
      b = 0;
      #1 $display("$pow(2,3) returns %d", $pow(2,3));
      #1 result = $pow(a,b);
      #1 $display("$pow(a,b) returns %d (a=%d b=%d)", result, a, b);

=== C side:

  tf_data.type        = vpiSysFunc;
  tf_data.sysfunctype = vpiSysFuncSized;
  tf_data.tfname      = "$pow";
  tf_data.calltf      = PLIbook_PowCalltf;
  tf_data.compiletf   = PLIbook_PowCompiletf;
  tf_data.sizetf      = PLIbook_PowSizetf;
  vpi_register_systf(&tf_data);


int PLIbook_PowCalltf(char *user_data)
{
  s_vpi_value value_s;
  vpiHandle   systf_handle, arg_itr, arg_handle;
  int         base, exp, result;

  systf_handle = vpi_handle(vpiSysTfCall, NULL);
  arg_itr = vpi_iterate(vpiArgument, systf_handle);
  if (arg_itr == NULL) {
    vpi_printf("ERROR: $pow failed to obtain systf arg handles\n");
    return(0);
  }

  /* read base from systf arg 1 (compiletf has already verified) */
  arg_handle = vpi_scan(arg_itr);
  value_s.format = vpiIntVal;
  vpi_get_value(arg_handle, &value_s);
  base = value_s.value.integer;

  /* read exponent from systf arg 2 (compiletf has already verified) */
  arg_handle = vpi_scan(arg_itr);
  vpi_free_object(arg_itr); /* not calling scan until returns null */
  vpi_get_value(arg_handle, &value_s);
  exp = value_s.value.integer;

  /* calculate result of base to power of exponent */
  result = (int)pow( (double)base, (double)exp );

  /* write result to simulation as return value $pow */
  value_s.value.integer = result;
  vpi_put_value(systf_handle, &value_s, NULL, vpiNoDelay);
  return(0);
}