The lifetime intrinsics need some work in order to make it clear which
optimizations are or are not valid.
For now dropping this optimization avoids a miscompilation.
Patch by Björn Steinbrink.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214336 91177308-0d34-0410-b5e6-96231b3b80d8