>
> So what, the optimized code goes only once through the loop, and then
> bails out?  If so, what is the value of 'size' when the loop ends?
>

OK, so there was one more detail that I forgot to mention. It looks like I
also had "-funroll-loops". After removing it, "-O3" works fine too (without
"volatile"). I think this is still a toolchain bug because "-O3
-funroll-loops" combination works fine in the x64 build and what's more
important --- it *should* work fine. Anyway, maybe it's a good idea to
somehow prevent people from passing "-funroll-loops" by filtering it out
from "CFLAGS" in "Makefile" for example?