ISACOV : Ignore WILDCARD Bins

[Jalali]

Hello @silabs-robin @MikeOpenHWGroup ,
In the ISACOV agent there's some macros that define wildcard bins for toggling GPR (rx), the macros content 3 arguments :

• name
• field
• iff_exp
  as I understand the iff_exp argument is the one that decide if we create the Coverpoint or not, in the example the c.mv instruction does not have rs1, so it make sense to disable rs1_value coverpoint & toggling rs1 -> `ISACOV_CP_BITWISE(cp_rs1_toggle, instr.rs1_value, has_rs1) (has_rs1 = 0 for c.mv & has_rs1 = 1 for c.add)
  what i got in the coverage report is :
  

as you can see the rs1_value is successfully ignore, but rs1_toggle NO !! and it count in the coverage.

So I wanna know what you got int this covergoupe in the report, is that a tool behavior for synopsys or a BUG in these macros.

[silabs-robin]

From what I can tell, the iff only sets a qualifying condition to decide when the coverpoint can be sampled.
Similar to how iff works for bins.
So the coverpoint would still exist, AFAICT.
(I only read a bit of coverage code within core-v-verif and didn't confer the LRM now.)

Here is what it looks like for us:

[silabs-robin]

The CP in question: https://github.com/openhwgroup/core-v-verif/blob/master/lib/uvm_agents/uvma_isacov/cov/uvma_isacov_cov_model.sv#L977C4-L977C21

The macro in question: https://github.com/openhwgroup/core-v-verif/blob/master/lib/uvm_agents/uvma_isacov/uvma_isacov_macros.sv#L48C12-L48C12

I think the only way to remove the coverpoint might be to use the with syntax that was discussed previously. (At least I can't think of anything else at the moment.)
And I don't remember how well it went when you used iff instead.

[Jalali]

So it count also in coverage.
I don't think using iff with WILDCARD bins is the same as using iff with bins.
can't we use option.weight = iff_exp in the macros, that way we're sure that does not count

[Jalali]

I think the only way to remove the coverpoint might be to use the with syntax that was discussed previously. (At least I can't think of anything else at the moment.)

could you test it to confirm that with works in that case

[silabs-robin]

could you test it to confirm that with works in that case

I couldn't get it to work.
(Not sure why, because the LRM grammar seems to say it is okay, but Xcelium thought otherwise.)

@MikeOpenHWGroup do you have any ideas?

[Mike Thompson]

I couldn't get it to work.
(Not sure why, because the LRM grammar seems to say it is okay, but Xcelium thought otherwise.)

Can you expand on this @silabs-robin? Does it compile and run under Xcelium? If so, what is the resulting coverage look like?

[silabs-robin]

I didn't manage to add with expressions to the wildcard bins, because Xcelium got an error saying it was not ok to do so. (Compile time error.)

So then I can't really think of any ideas atm for how to prevent such coverpoints from showing in coverage results.

[silabs-robin]

can't we use option.weight = iff_exp in the macros, that way we're sure that does not count

@AyoubJalali Yeah, maybe this. I have not tried it.

[Jalali]

I couldn't get it to work.

try it on WILDCARD BINS not on the coverpoint

[silabs-robin]

I couldn't get it to work.

try it on WILDCARD BINS not on the coverpoint

That is what I did.