Now that we've replaced the vinsertf128 intrinsics,
do the same for their extract twins.
This is very much like D8086 (checked in at r231794):
We want to replace as much custom x86 shuffling via intrinsics
as possible because pushing the code down the generic shuffle
optimization path allows for better codegen and less complexity
in LLVM.
This is also the LLVM sibling to the cfe D8275 patch.
Differential Revision: http://reviews.llvm.org/D8276
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232045 91177308-0d34-0410-b5e6-96231b3b80d8
b4c1547749