Check for NaN or Inf in SystemVerilog

1
votes

How to check if a real variable in SystemVerilog is at 'Not a Number' (NaN) or infinite (Inf)? Do system tasks exist for this purpose like isnan() or isinf() in C99?

2
verilogsystem-verilog
if($realtobits(realvariable)==64'b1111111111111000000000000000000000000000000000000000000000000000) works for me. But it is awkward. - SeblZ

2 Answers

0
votes

You could do:

let isnan(r) = {$realtobits(r)}[62:52] == '1 && {$realtobits(r)}[51:0] != '0;

Although the SystemVerilog LRM references IEEE 754 for representing floating point numbers, it does not define the results of real operations that could produce NaN or Inf. So use with caution.

0
votes

I now use

function real_is_number; 
  input real in;
  reg [63:0] in_bits;
  begin
    in_bits=$realtobits(in);
    real_is_number = ~&in_bits[62:52];
  end
endfunction

to detect any real value which is not an ordinary number.