https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114923
--- Comment #3 from nfxjfg at googlemail dot com ---
I'm expecting gcc to realize that the pointer escaped into the unknown, and
that it can't assume that the memory won't change. This is just causality, not
any vague made up viralyness.
Anyway, a 'asm volatile("":::"memory")' is too radical and increased code size
too much in my case (but it's a good suggestion). Making the buffer volatile
will inhibit optimizations before or after the DMA.
