This is avr-gcc compiled from the git mirror commit
fcdd7053da, which says it's SVN trunk@243328.
This code used to work on some earlier GCC, but I don't know which
version.
Host is Debian Linux, i686, compiled with gcc (Debian 6.2.1-5) 6.2.1 20161124.
Configured with: ../gcc/configure --target=
This is some low-level crypto code, an MMX implementation of Dan
Bernstien's "ChaCha" pseudorandom function. The input is a 4x4 array
of 32-bit words, and mixing proceeds down either columns or diagonals.
Thus, the implementation keeps each row in a pair of MMX registers,
does mixing down the col
