[InstCombine] add memcpy expansion tests with potential DL dependency; NFC

Current behavior is to transform these independently of the datalayout.

There's a proposal to change this in D35035:
https://reviews.llvm.org/D35035


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310611 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed