The C compiler may attempt to reorder read and write operations when
accessing the source and destination buffers. So instead of sequential
memory accesses we may get something like a "drunk master style"
memory access pattern. Certain processors, such as ARM Cortex-A7,
do not like such memory access pattern very much and it causes
a major performance drop. The actual access pattern is unpredictable
and is sensitive to the compiler version, optimization flags and
even sometimes on some changes in unrelated parts of source code.

So use the volatile keyword for the destination pointer in order
to resolve this problem and make C benchmarks more deterministic.

See https://github.com/ssvb/tinymembench/issues/7