Re: Enhancement: Dynamic Values on attributes.

From: Michael McNamara (mac@verisity.com)
Date: Fri Oct 31 2003 - 10:46:31 PST

  • Next message: Krishna Garlapati: "Re: Enhancement: Dynamic Values on attributes."

    So it seems that $swrite almost fits the bill, but because it is a
    task rather than a function, one is stuck.

    However you say that the vendors tool wants a single attribute in a
    string; so this leads be to believer if there was a $strcat, it would
    not work:

    dff ff1 (q,d,clk) (* placement=$strcat(xloc,yloc,size) *)

    Note of course, that you don't need it to be a system function,
    however it may make it easier, as one could define scat_loc as a user
    constant function, which calls $swrite to do the work:

    function [80*8:1] scat_loc( input [31:0] xloc, yloc, size)
      begin
        $swrite(scat,"%d_%d_%s",xloc,yloc,size);
      end
    endfunction

    and then give the parameters:

    parameter [31:0] xloc = 1,
              [31:0] yloc = 1,
              [10*8:1] size = "small";

    and the instantiation:

    dff ff1 (q,d,clk) (* placement=scat_loc(xloc,yloc,size) *)

    Or does the tool instead parse the verilog, and hence these constant
    functions will not be called?

    dff ff1 (q,d,clk) (* placement=scat_loc(xloc,yloc,size) *)
    -- On Oct 30 2003 at 16:36, Krishna Garlapati sent a message:
    > To: sharp@cadence.com, btf@boyd.com
    > Subject: "Re: Enhancement: Dynamic Values on attributes."
    >
    > I guess my explanation for this request was not very clear. FPGA designers
    > use these attributes primarily to pass custom information (like location,
    > mapping methods, types etc) to the vendor backend.
    >
    > The vendor's backend tool expects a single attribute in a string
    > form and ignores everything else. I agree with you that using
    > multiple Vlog-2001 style attributes can achieve the requested
    > functionality but it does not fulfill the purpose.
    >
    > My request is to simply provide a function that can take in a bunch
    > of strings and constant expressions as parameters and return a
    > string, which is the concatenated version that contains all the
    > string parameters (as is) and evaluated constant expressions. I
    > also think implementing this is pretty very straightforward.
    >
    > We have implemented attributes for VLog-2001 and I don't think
    > there is a single system function that can realize this. A good
    > percentage of our users are already using the $strcat and we think
    > it would be a good idea to make it into the standard for
    > compatibility issues.
    >
    > "From your example, it appears that "xc_rloc" takes a string that
    > holds a row and column position encoded by strings of digits after
    > "R" and "C" (I'll ignore the ".S" part, since I didn't understand
    > what it was). You could do the same thing easily in Verilog-2001
    > by changing this to two attributes, "xc_rloc_R" and "xc_rloc_C",
    > which take the row and column directly as numerical values instead
    > of converted to strings."
    >
    > This is not acceptable to the users for the reasons I listed above.
    >
    > ""Printing" a numerical value into a string form is a complex operation,"
    >
    > I am wondering why?? I dont see a big problem here or may be I am
    > missing something.
    >
    > --
    > - Krishna Garlapati, Synplicity Inc. (408)215-6152
    >

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