Revert r318193 "[SLPVectorizer] Failure to beneficially vectorize 'copyable'...

Revert r318193 "[SLPVectorizer] Failure to beneficially vectorize 'copyable' elements in integer binary ops."

It crashes building sqlite; see reply on the llvm-commits thread.

> [SLPVectorizer] Failure to beneficially vectorize 'copyable' elements in integer binary ops.
>
>         Patch tries to improve vectorization of the following code:
>
>         void add1(int * __restrict dst, const int * __restrict src) {
>           *dst++ = *src++;
>           *dst++ = *src++ + 1;
>           *dst++ = *src++ + 2;
>           *dst++ = *src++ + 3;
>         }
>         Allows to vectorize even if the very first operation is not a binary add, but just a load.
>
>         Fixed issues related to previous commit.
>
>         Reviewers: spatel, mzolotukhin, mkuper, hfinkel, RKSimon, filcab, ABataev
>
>         Reviewed By: ABataev, RKSimon
>
>         Subscribers: llvm-commits, RKSimon
>
>         Differential Revision: https://reviews.llvm.org/D28907

llvm-svn: 318239