The 64/128-bit vector types are legal if NEON instructions are
available. However, there was no matching patterns for @llvm.cttz.*()
intrinsics and result in fatal error.
This commit fixes the problem by lowering cttz to:
a. ctpop((x & -x) - 1)
b. width - ctlz(x & -x) - 1
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242037 91177308-0d34-0410-b5e6-96231b3b80d8
