ARM64: Redundant movs done for zero extend the register

[kunalspathak]

Redundant movs are done to zero the upper 32-bit of register, but if they are done after ldr, we can eliminate them.

B8736822          ldr     w2, [x1, x19]
2A0203E2          mov     w2, w2   ; can be eliminated

In framework libraries code, found 1098 such instructions that can eliminated.

Details :
redundant-mov-3.txt

category:cq
theme:optimization
skill-level:intermediate
cost:small