source: xtideuniversalbios/trunk/Tools/unused.pl@ 301

#
# Looks for unused entry points, to aid in discovering dead code that can be removed
#
# Usage: unused.pl listing unused.asm
#        
# where: listing is the normal listing from assembly
#        unused.asm is assembled with the -E nasm flag
#
# Annotations can be placed in the source to eliminate false positives:
#   a) if a label can be fallen into, place "; fall through to label" above the label
#   b) "; unused entrypoint ok" can be placed on the same line with the label
#   c) "; jump table entrypoint" can be placed on the same line with the label
#

print "::".$ARGV[0]."::".$ARGV[1]."::\n";

open( LST, "<", $ARGV[0] ) || die "cannot open listing: ".$ARGV[0];
open( UNUSED, "<", $ARGV[1] ) || die "cannot open unused.asm: ".$ARGV[1];

while(<LST>)
{
    if( /fall\s+(-?through\s+)?(to\s+)?([a-z0-9_]+)/i )
    {
        $ok{ $3 } = 1;
    }
    if( /unused\s+entrypoint\s+ok/i && /^\s*\d+\s+\<\d\>\s([a-z0-9_]+)\:/i )
    {
        $ok{ $1 } = 1;
    }
    if( /jump\s*table\s+entrypoint/i && /^\s*\d+\s+\<\d\>\s([a-z0-9_]+)\:/i )
    {
        $ok{ $1 } = 1;
    }
}

while(<UNUSED>)
{
    if( /^([a-z0-9_]+\:)?\s+db\s+(.*)$/i || /^([a-z0-9_]+\:)?\s+dw\s+(.*)$/i || /^([a-z0-9_]+\:)?\s+mov\s+(.*)$/i ||
        /^([a-z0-9_]+\:)?\s+call\s+(.*)$/i || /^([a-z0-9_]+\:)?\s+j[a-z]?[a-z]?[a-z]?[a-z]?[a-z]?\s+(.*)$/i ||
        /^([a-z0-9_]+)?\s+equ\s+(.*)$/i )
    {
        $rem = $2;
        @words = split( /([a-z0-9_]+)/i, $_ );
        for( $t = 0; $t <= $#words; $t++ )
        {
            $jumptable{ $words[$t] } = 1;
        }
    }
    if( !(/^g_sz/) && /^([a-z0-9_]+)\:/i )
    {
        push( @definition, $1 );
    }
}

$results = 0;
for( $t = 0; $t <= $#definition; $t++ )
{
    $d = $definition[$t];
    if( !$ok{$d} && !$jumptable{$d} )
    {
        print $definition[$t]."\n";
        $results++;
    }
}

print ">>>> Unused Count: ".$results."\n";