[AArch64] Support MI and PL (#150314)
Now, why would we want to do this?
There are a small number of places where this works:
1. It helps peepholeopt when less flag checking.
2. It allows the folding of things such as x - 0x80000000 < 0 to be
folded to cmp x, register holding this value
3. We can refine the other passes over time for this.
