[MemCpyOpt] allow some undef contents overread in processMemCpyMemCpyDependence#143745

vtjnash merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

vtjnash:jn/memcpy-opt-memcpy-undefvtjnash/llvm-project:jn/memcpy-opt-memcpy-undefCopy head branch name to clipboard