( ESNUG 385 Item 14 ) -------------------------------------------- [12/19/01]
Subject: ( ESNUG 383 #9 ) How To Use The Absolute Minimum PLI With VCS 6.0
> By running VCS with only the Signalscan PLI compiled in VCS (but not used),
> I got a speed-up of 8 to 10 percent on a 3 Mgate RTL design and close to
> 20 percent on a 500 kgate RTL design.
>
> By not compiling in any PLI routines I got a speed-up of 42 to 48 percent
> on both my small and large design.
>
> - Anders Nordstrom
> Nortel Networks, Ltd. Ottawa Canada
From: Amitabh Chand <amitabh@synopsys.COM>
Hi John,
Anders brings up an important point about enabling VCS optimizations. It's
true that turning on global PLI access will hurt VCS performance even if no
actual dumping is done. This is a serious problem with any company that has
a corp CAD group that controls VCS scripts since they want to make everything
available to the verification engineers. VCS engineering is working on
fixing this problem. Until then, we recommenced to use Adaptive PLI which
was introduced in VCS 6.0.
Two steps to use adaptive PLI:
1.) add one flag to the runtime simulation: simv +vcs+learn+pli
This tell VCS to monitor all PLI access and create an new
table file containing just the modules that really needed
to talk to the PLI program.
2.) recompile your design with one additional flag: vcs +applylearn
This tells VCS to override PLI visibility with the new table file.
Thus now VCS will be able to compile and do much more optimizations without
all the overhead of PLI access to Verilog modules that do not need it.
- Amitabh Chand
Synopsys, Inc. Marlboro, MA
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