X86. The pass optimizes as a unit the entire wide load + shuffles pattern
produced by interleaved vectorization. This initial patch optimizes one pattern
(64-bit elements interleaved by a factor of 4). Future patches will generalize
to additional patterns.
Patch by Farhana Aleen
Differential revision: http://reviews.llvm.org/D24681
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284260 91177308-0d34-0410-b5e6-96231b3b80d8
