Subject: RE: Alternative to SvccBindSVcallee/r
From: Amouroux, John (john_amouroux@mentorg.com)
Date: Tue Nov 12 2002 - 11:30:00 PST
Kevin,
This is interesting. I've been thinking of something along these lines too.
An extension to your idea could be to define a whole structure that gets
passed in instead of a separate pli handle and context pointer. Then the
vendors could put in other useful data at compile-time as well (run-time
would be too slow).
Something like:
typedef struct directc_context_struct
{
int context_version /* = 1, to allow for version changes */
pli_handle pli; /* the pli instance handle */
char *file_name; /* source file name if HDL caller */
int line_number; /* source line number */
void *user_context; /* our beloved user-context pointer */
} directc_context;
I really don't know if this extra info is useful. My thought is that the
line number info may be a way to differentiate the places where the directc
function is called more than once from the same block, as well as allow
vendors to emit better error messages. But the nicest thing about passing a
structure is that we can add or change context info without requiring the
users to change their call site code.
However, the biggest problem I see with this is that if the vendor needs to
do some elaboration-time initialization to set up the user context data,
these calls will happen too late, maybe even if they occur within an initial
block. A complicated way around this would be to always call each and every
function instance with a special flag at elab-time to allow this
pre-simulation context set-up.
Another smaller issue is that the C code writer will still have to write
some type of mapping/hash functions if they want to share one function entry
point across numerous blocks and still do some instance-specific
specializations.
My worry is that by the time we do all this, John S's straightforward
svcBindCallee(r) scheme may actually end up being simpler.
Let's see what the others have to say.
-- John A.
P.S.
lst_data needs to be static...
-----Original Message-----
From: Kevin Cameron x3251 [mailto:Kevin.Cameron@nsc.com]
Sent: Tuesday, November 12, 2002 10:40 AM
To: sv-cc@server.eda.org
Subject: Alternative to SvccBindSVcallee/r
[I don't think this got to the reflector last time I sent it.]
To avoid using a seperate "bind" call, functions requiring context
can be called as -
<user func name>(<instance handle>,void **c_context,....)
The instance handle can be a PLI handle for call-backs, and c_context
points at a pointer location in the simulator which is initially zero
- the user can fill it if desired on the first call for future calls
(avoids hash-lookup).
e.g.
SV:
extern "C" context int uf(int);
int x;
always@(clock) x=uf(x);
C:
int uf(handle ip,void **p_cntxt,int data)
{
int *lst_data,
new_num;
if (!(lst_data = *(int **)p_cntxt)) {
/* first call only */
if(!(*p_cntxt = calloc(1,sizeof int)) {
reportError(ip,"C:uf","Out of memory");
return -1;
}
}
new_num = random_num(*lst_data);
*lst_data = new_num;
return new_num;
}
If you were calling a SystemC class (non-virtual) method it can
use the ip handle to locate the right "this" on the first call
and save it in *p_cntxt.
Regards,
Kev.
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