Prefetches used to always be chained between any previous and following
memory accesses. The problem with this was that later optimizations, such as
folding of a load into the user instruction, got disrupted.
This patch relaxes the chaining of prefetches in order to remedy this.
Reveiw: Hal Finkel
https://reviews.llvm.org/D38886
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322163 91177308-0d34-0410-b5e6-96231b3b80d8
