Why does this change to the makefile make the performance go up? : <p>I recently completed a performance lab in class, but there was one thing that my buddy showed me that I can't figure out why.
In the original makefile we had:</p>

<pre><code>##
##

CXX =g++
CXXFLAGS= -m32 -static
</code></pre>

<p>But I changed the CXXFLAGS to:</p>

<pre><code>##
##

CXX =g++
CXXFLAGS= -m32 -static -funroll-loops -O3
</code></pre>

<p>What exactly does the -funroll-loops -O3 do that the original doesn't?</p>
