+/*
+ * I have nothing against unrolling but it's usually done for
+ * several reasons, namely:
+ * - minimize percentage of decision making code, i.e. branches;
+ * - avoid cache trashing;
+ * - make it possible to schedule loads earlier;
+ * Now let's examine the code below. The cornerstone of C is
+ * "programmer is always right" and that's what we love it for:-)
+ * For this very reason C compilers have to be paranoid when it
+ * comes to data aliasing and assume the worst. Yeah, but what
+ * does it mean in real life? This means that loop body below will
+ * be compiled to sequence of loads immediately followed by stores
+ * as compiler assumes the worst, something in A==B+1 style. As a
+ * result CPU pipeline is going to starve for incoming data. Secondly
+ * if A and B happen to share same cache line such code is going to
+ * cause severe cache trashing. Both factors have severe impact on
+ * performance of modern CPUs and this is the reason why this
+ * particulare piece of code is #ifdefed away and replaced by more
+ * "friendly" version found in #else section below. This comment
+ * also applies to BN_copy function.
+ *
+ * <appro@fy.chalmers.se>
+ */