Effect Of Using BitWise and Logical Operators !!

spartanthewarrior · Senior Joined: Aug 15, 2009 Posts: 32

Hi All,

I have a question:

How can I measure performance of simulator when, I am using (BitWise) or (Logical) operators.

How can I check the difference these operators are making ?

Example:

property Compare(disable_assertion) ;
logic [17:0] val;

disable iff (~rst | disable_assertion )
(`TRUE, val = selected_val) ##5

1) (val === out_val);

2) (val ~^ out_val);

dave_59 · Posted: Thu Jun 14, 2012 2:29 am **Post subject:**

I hope you realize the two choices are not equivalent. 2) should be

&(val ~^ out_val);

Questa can show you the intermediate expressions in an assertion.

I don't think you will see much difference in performance because accessing a 4-state value can be more expensive that performing an operation on it.

Dave Rich
Mentor Graphics

chrisspear · Posted: Sun Jun 17, 2012 2:05 pm **Post subject:**

Before you worry too much about performance, run your simulator's profiling tool to see if this is a problem. Trying to write optimal code can take more time than writing comprehensible code, and will take more time to decode by other people. If this code only consumes 1% of the total simulation time, what have you gained?

Instead, run the profile tool and look for the "whales". A few hours tweaking your code can save hundreds of simulation hours. If you've never tried this before, call your Application Engineer and have him or her walk you through the process. The payback will be great!
_________________
Chris Spear
Co-Author: SystemVerilog for Verification - 3rd edition!
http://chris.spear.net/systemverilog