Loop-invariant code motion: Difference between revisions

Revision as of 15:36, 24 December 2008

Revision as of 21:53, 9 March 2009

Line 12:

If we consider the following code sample, two optimization possibilities can be applied.

<source lang="C">

<pre>

while (j < maximum - 1)

{

j = j + (4+array[k])*pi+5;

}

</presource>

The calculation of <code>maximum - 1</code> and <code>(4+array[k])*pi+5</code> can be moved outside the loop, and precalculated, resulting in something similar to:

<source lang="C">

<pre>

int maxval = maximum - 1;

int calcval = (4+array[k])*pi+5;

while (j < maxval)

{

j = j += calcval;

}

</presource>

[[Category:Compiler optimizations]]