Calculate Gated Clock Percentage

Abstract

This use case shows how to calculate register driven by gated clock percentage

GofCall Script

## Script: gated_clock_percentage.pl
## Calculate the clock gated registers percentage 
##
use strict;
read_library("libdir/hvt.lib", "libdir/rvt.lib");
read_design("-imp", "netdir/netlist.v");

our $total_reg_num = 0;
our $gated_reg_num = 0;
set_quiet(1);
my @tops = get_roots();
my $top = $tops[0];
&go_through_module($top);
my $ratio;
my $st_ratio;
if($total_reg_num){
  $ratio = $gated_reg_num / $total_reg_num;
  $ratio *= 100;
  $st_ratio = sprintf("%2.2f", $ratio);
  print "Overall, gated clock percentage $st_ratio% ($gated_reg_num / $total_reg_num)\n";
}

exit;



##
## recursively go through the modules to get registers
##

sub go_through_module{
  my ($top) = @_;
  set_top($top);
  # get all flops in $top module
  my @ffs = get_cells("-type", "ff");
  my $subtotal = scalar(@ffs);
  my $subgated = 0;
  $total_reg_num += $subtotal;

  foreach my $ff (@ffs){
    my $ref = get_ref($ff);
    my @clks = get_pins($ref, "-clock");
    my $clock_pin = $clks[0];
    my @driver = get_driver("$ff/$clock_pin");
    my $drive_inst = $driver[0];
    if($drive_inst eq ""){ # not driven by leaf cell
      next;
    }
    my @types = get_cell_info($drive_inst, "-type");
    if(scalar(@types)==1 && $types[0] eq "cg"){
      $gated_reg_num++;
      $subgated++;
    }
  }    
  if($subtotal){
    my $ratio = $subgated / $subtotal;
    $ratio *= 100;
    my $st_ratio = sprintf("%2.2f", $ratio);
    print "Module $top has gated clock percentage $st_ratio% $subgated / $subtotal \n";
  }
  ##
  ## Do each hierarchical sub module
  ##
  my @sub_instances = get_instances;
  foreach my $instance (@sub_instances){
    set_top($top);
    my $sub_module = get_ref($instance);
    &go_through_module($sub_module);
  }
}