Is it possible to iterate systemverilog associative array with non-int index type through VPI c function?

Question

For example

// test.sv

class cls;
    int b;
endclass

module m
    cls testObj;
    int map[cls];
    initial begin
      inst = new;
      inst.b = 10;
      map[cls] = 12;
      $VPIcall;
    end
endmoudle

// pseudocode vpi c

vpiHandle mapHandle = vpi_handle_by_name("m.map", 0); // return valid handle
vpiHandle valueHandle = vpi_handle_by_name("map[testObj]", mapHandle); // return zero

seems we could not get valueHandle like this and I wonder whether is it possible to iterate or get value stored in associative array through VPI?

Serge · Answer 1 · 2023-08-09T15:05:48.947

Notes:

VPI capabilities are implemented differently by different tools. Your first line should work, depending on the tool and on the qualifiers used at compilation. For example, to make it work with 'vcs' I used -debug_all (there should be a better choice).
The second line will never work, at least for object names, however you can scan over the elements of the array using vpi_iterate/vpi_scan. It seems that direct access with vip_handle_by_index does not work for associative arrays.
Your code sample is not compilable.

Here is a sample that works for me with vcs:

verilog:

class cls;
   int b;
endclass

module m;
   
   cls testObj, obj1;
   
   int map[cls];
   initial begin
      testObj = new;
      testObj.b = 10;
      map[testObj] = 12;
      obj1 = new;
      obj1.b = 20;
      map[obj1] = 13;
      $testme;
   end
endmodule

vpi:

#include <stdio.h>
#include <vpi_user.h>

void testme() {
    vpiHandle mapHandle = vpi_handle_by_name("m.map", 0); // return valid handle
    vpi_printf("map: %p\n", mapHandle);

vpiHandle el;
    s_vpi_value val = {vpiIntVal};

    vpiHandle iterator = vpi_iterate(vpiReg, mapHandle);
    while ((el = vpi_scan(iterator))) {
        vpi_get_value(el, &val); 
        vpi_printf("%s: %d\n", vpi_get_str(vpiType, el),  val.value.integer); 
    }
    
}

Alternatively, for simpler associative arrays, like the once using strings for associations, it is easy to use an export dpi functions to do direct access, like in the following example:

module m;
   
   int map[string];
   initial begin
      map["testObj"] = 12;
      map["obj1"] = 13;
      $testme;
   end

   export "DPI" function getMap;
   function int getMap(string name);
      return map[name];
   endfunction
      
endmodule
============
#include <stdio.h>
#include <vpi_user.h>
#include <sv_vpi_user.h>
#include <svdpi.h>


void testme() {

    svScope scope = svGetScopeFromName("m");
    svSetScope(scope);
    
    int testObjVal = getMap("testObj");
    int obj1Val = getMap("obj1");
    vpi_printf(" ==> %d, %d\n", testObjVal, obj1Val);
    
}

sorry for my incomplete code snippet, and I test your code on EDAplayground. It seems that we could get handle like map[0], or map[1] while these handle could not be used to get their value correctly. Could you try with vpi_get_vaule to verify that we could get 12 or 13 through map[testObj] or map[obj1] ? — tarik jhin, Aug 09 '23 at 06:56
Besides, one of my colleagues suggest that we could use vpi_iterate to loop through the entire assoc array and I try and it works, actual value could be fetched from iterator like this `vpiHandle mapHandle = vpi_handle_by_name("m.map", 0); vpiHandle iter = vpi_iterate(vpiVarSelect, mapHandle); ` Since this way of iteration way is a little bit of redundancy, do you know whether vcs support some like `vpi_handle_by_name("map[testObj]", mapHandle);` so that we could get needed value directly without iteration — tarik jhin, Aug 09 '23 at 07:08
I apologize for not fully testing this. I could not find anything in standard which would prevent from using vpi_handle_by_index for associative arrays but it definitely does not work, at least in vcs. I cannot find any way to access elements directly without iterating over them, so I modified my answer. The only suggestion I have is to use export dpi functions to access arrays on verilog side directly, but it also looks like a heavy weight solution. — Serge, Aug 09 '23 at 14:38

Is it possible to iterate systemverilog associative array with non-int index type through VPI c function?

1 Answers1