Why does .NET Native compile loop in reverse order?

inc might be slower than add because of the partial flag update. Moreover add affects the zero flag so you don't need to use another cmp instruction. Just jump directly.

This is one famous type of loop optimization

reversal: Loop reversal reverses the order in which values are assigned to the index variable. This is a subtle optimization which can help eliminate dependencies and thus enable other optimizations. Also, certain architectures utilize looping constructs at Assembly language level that count in a single direction only (e.g. decrement-jump-if-not-zero (DJNZ)).

• Is it faster to count down than it is to count up?
• GCC Loop optimization

You can see the result for other compilers here.

Your conclusion is correct: inverted cycle will target 0 (cycle will ends when register value reach 0), so that Add will set zero flag used in conditional branch.

This way you don't need dedicated Cmp which leads to: 1) size optimization 2) it's also faster (conclusion from compiler programmers decision and another answer).

That's pretty common assembler trick to write loop targeting 0. I am surprised you understand assembler, but don't know (asking) about it.