[LoopVectorizer] give more advice in remark about failure to vectorize call

Something like this is requested by:
https://bugs.llvm.org/show_bug.cgi?id=40265
...and it seems like a common enough case that we should acknowledge it.

Differential Revision: https://reviews.llvm.org/D56551


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351010 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed