ARM64: Optimize redundant memory loads with mov

[kunalspathak]

ldr     w1, [fp,#28]
ldr     w0, [fp,#28]

The 2nd load can be converted into mov which takes 2 fewer cycles than ldr.

ldr     w1, [fp,#28]
mov     w0, w1

I collected no. of such ldr pairs in framework libraries and found approx. 540 pairs in 300 methods.

Details:

ldr_to_mov.txt

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

[Dotnet-GitSync-Bot]

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[EgorBo]

NOTE: this opt should not be done for loads of "volatile" fields