[compiler-rt] [AArch64][compiler-rt] Add memcpy, memset, memmove, memchr builtins. (PR #77496)

[Eric Christopher via llvm-commits]

echristo wrote:

> Add naive implementation of memcpy, memset, memmove, memchr for SME targets. Co-authored-by: David Sherwood [david.sherwood at arm.com](mailto:david.sherwood at arm.com)

Do we have an idea of the expected performance differences here in the presence of SME? 

https://github.com/llvm/llvm-project/pull/77496