[compiler-rt] [ubsan] Use internal_memcpy to copy ubsan bits size (PR #121586)

[Florian Mayer via llvm-commits]

fmayer wrote:

> The proper way would be to use ifdef to separate platforms working with non-aligned values from platforms behaving improperly, but i was not able to locate such define.

shouldn't the compiler be able to optimize the memcpy with target specific knowledge? 

https://github.com/llvm/llvm-project/pull/121586