Re: [Iverilog-devel] iverilog functions

[Cary R. <cy...@ya...>]

I can confirm that this does fail using both V10 and development.I'm guessing it has something to do with the constant function code and the SystemVerilog type or operators. I do not have time to look at this right now. This looks like valid code and is likely a problem in Icarus so not something that is easy for an end user to debug. If you feel adventurous then look at the constant function code in the compiler (eval_tree.cc, etc.) and add appropriate debug output to see what is going on.
Cary
 

    On Monday, February 8, 2016 8:02 PM, Dan McLeran <dan...@gm...> wrote:
 

 Thanks. Here is a simple example. Using the function clog2 in the
declaration of the logic array causes the failure. Using clog2 in the
sequential logic appears to work.

iverilog -g2012 -Wall -o example example.sv

//example.sv
module example #(parameter N = 8) (output logic[3:0] result, input logic clk);
    //logic[clog2(N):0] temp; //comment this line back in to see the failure

    always@(posedge clk)
        result <= clog2(N);

    function int clog2(input int n);
        begin
            clog2 = 0;
            n--;
            while(n > 0)
                begin
                    clog2++;
                    n >>= 1;
                end
        end
    endfunction
endmodule

On Mon, Feb 8, 2016 at 5:13 PM, Stephen Williams <st...@ic...> wrote:
>
> If you make a small but complete example that we cal compile
> for ourselves, we can take a look at this.
>
> On 02/08/2016 12:50 PM, Dan McLeran wrote:
>> I am using iverilog to learn SystemVerilog. I am following along in a
>> digital system design book and am having trouble building one of the
>> examples. The code uses a function to calculate log2:
>>
>> module #(parameter AL = 8, BL = 8, QL = AL + BL) ...
>>
>>    logic[clog2(AL):0] count;
>>    ...
>>    function clog2(input int n);
>>        begin
>>            clog2 = 0;
>>            n--;
>>            while(n > 0)
>>                begin
>>                    clog2++;
>>                    n >>= 1;
>>                end
>>          end
>>    endfunction
>> endmodule
>>
>> I calling iverilog like this:
>>
>> iverilog -g2012 -Wall -o booth booth.sv
>>
>> It seems to get hung processing the loop or detecting n == 0 or
>> something. Is there an easy way
>> to debug this? I was thinking I'd run iverilog within gdb but maybe
>> there is a faster way to determine what is happening?
>>
>> Regards,
>>
>> Dan McLeran
>>
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>
>
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