half-shuffles, even looking through intervening instructions in a chain.
Summary:
This doesn't happen to show up with any test cases I've found for the current
shuffle lowering, but previous attempts would benefit from this and it seems
generally useful. I've tested it directly using intrinsics, which also shows
that it will work with hand vectorized code as well.
Note that even though pshufd isn't directly used in these tests, it gets
exercised because we combine some of the half shuffles into a pshufd
first, and then merge them.
Differential Revision: http://reviews.llvm.org/D4291
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211890 91177308-0d34-0410-b5e6-96231b3b80d8
4363b0729b