Loop Unrolling

From ActionScriptWiki

A loop with a constant known maximum can be unrolled very easy. In most cases it does not make sense to unroll a loop manually because maintaining the code will require much more work. This is usually a job which the compiler can perform in its optimization phase.

[edit] Normal Version

const x: Number;

for( var i: Number = 0; i < 5; ++i )
{
	x = i * i;
	trace( x.toString() );
}

[edit] Unrolled Version

const x: Number;

x = 0.0 * 0.0;
trace( x.toString() );

x = 1.0 * 1.0;
trace( x.toString() );

 x = 2.0 * 2.0;
trace( x.toString() );

 x = 3.0 * 3.0;
trace( x.toString() );

 x = 4.0 * 4.0;
trace( x.toString() );

Now it is be possible to recude that code even more.

const x: Number;

x = 0.0;
trace( x.toString() );

x = 1.0;
trace( x.toString() );

 x = 4.0;
trace( x.toString() );

 x = 9.0;
trace( x.toString() );

 x = 16.0;
trace( x.toString() );

The next step in this example is of course removing the x variable.

trace( (  0.0 ).toString() );
trace( (  1.0 ).toString() );
trace( (  4.0 ).toString() );
trace( (  9.0 ).toString() );
trace( ( 16.0 ).toString() );

The code is now reduced and would execute faster. But unrolling a loop is something which only begins to make sense with a lot of iterations. Therefore it does not make sense to apply this technique manually.