gEDA-user: BUGS: iverilog reals

[lingwitt@xxxxxxxxxxxxx]

Hello again,

I've been playing around with $realtobits and $bitstoreal,
and I've found things aren't as clean as I'd hoped.

Basically, I want to simulate floating point operations in my modules.
I figured the process would be:
	(1) Convert a real to bits and pass those as an input to a module.
	(2) Convert the input to a real (without needing a variable).
	(3) Perform an operation.
	(3) Convert result of the operation to bits and output.

Here are some problems I've found.

///////////// [ 1 ] /////////////

The following compiles
(and probably shouldn't, unfortunately):

    module reals;
        wire [63:0] blah = $realtobits(6.35e25);
    endmodule

but when run produces:

    ./a.out:7: syntax error


///////////// [ 2 ] /////////////

The following compiles:

    module reals;

        SomeModule someModule
        (
            $realtobits(3.14+3.15)
        );

    endmodule

    module SomeModule
    (
        input  [63:0] in
    );

    endmodule

but when run produces:

    internal error: 13vvp_arith_sum: recv_real(3.140000) not  
implemented
    ../../src/vvp/vvp_net.cc:1386: failed assertion `0'
    Abort trap

Seems like the parse tree is a bit out of whack.
Since this doesn't work, neither does something like this:

    $realtobits($bitstoreal(arg1)+$bitstoreal(arg2))



///////////// [ 3 ] /////////////

There was some problem with realtobits/bitstoreal that
was fixed with the following change:

Index: vvp/vpi_tasks.cc
===================================================================
RCS file: /home/demon/anoncvs/verilog/vvp/vpi_tasks.cc,v
retrieving revision 1.35
diff -u -r1.35 vpi_tasks.cc
--- vvp/vpi_tasks.cc    12 Apr 2007 04:45:53 -0000      1.35
+++ vvp/vpi_tasks.cc    28 Apr 2007 03:25:34 -0000
@@ -577,7 +577,7 @@
       vpip_cur_task = (struct __vpiSysTaskCall*)ref;
       if (vpip_cur_task->defn->info.calltf) {
-           assert(vpi_mode_flag == VPI_MODE_NONE);
+           /*assert(vpi_mode_flag == VPI_MODE_NONE);*/
            vpi_mode_flag = VPI_MODE_CALLTF;
            vpip_cur_task->defn->info.calltf(vpip_cur_task->defn- 
>info.user_data);
            vpi_mode_flag = VPI_MODE_NONE;



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