systemVeilog - pass array of unknown size

Question

I have the following function:

   function void foo_arr_bit (int seed, ref bit [*] mem, string  mem_name);
      for (int i=0; i< mem.size(); i++)
    mem[i] = my_randomize_int(seed, mem[i], mem_name);     
   endfunction: foo_arr_bit

I call the function by:

 foo_arr_bit(seed, data_bit, "data_bit");

Where data_bit can be: bit [1:0]/ bit [2:0]/ bit [3:0]/ bit [4:0]/ bit [5:0] etc...

When I try to compile I got the following error: near "[": syntax error, unexpected [ , expecting IDENTIFIER or TYPE_IDENTIFIER or NETTYPE_IDENTIFIER.

Hida · Accepted Answer · 2016-12-19 08:51:59Z

1

[*] is not the correct syntax for a dynamic array, use [].

Your array can only be dynamic in the unpacked dimension. So you cannot have bit [] mem_array, but must have bit mem_array[].

Finally a function using pass by reference cannot have a static lifetime. That is, it must be declared as automatic.

function automatic void foo_arr_bit (int seed, ref bit mem[], string  mem_name);
  for (int i=0; i< mem.size(); i++)
    mem[i] = my_randomize_int(seed, mem[i], mem_name);     
endfunction: foo_arr_bit

Edit: But even with these changes you face a bigger issue. Passing by reference demands very strict typing. There is no casting allowed so I expect there to be issues with type conversion.

Furthermore, passing by reference is not really necessary in your case. Use inout instead.

function automatic void foo_arr_bit (input int seed, string  mem_name, inout bit mem[]);
  for (int i=0; i< mem.size(); i++)
    mem[i] = my_randomize_int(seed, mem[i], mem_name);
endfunction: foo_arr_bit

edited Dec 19, 2016 at 8:51

answered Dec 19, 2016 at 8:16

Hida

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2 Comments

sara8d Over a year ago

my input is packed array, not unpaked.

Hida Over a year ago

Systemverilog does not have dynamic packed arrays. Using a parameterizable class to encapsule your function could be a solution. More on that here: forums.accellera.org/topic/… Or just pass SIZE to the function and have a sufficiently large packed array.

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