trunc (load X) --> load (bitcast X to narrow type)
We have this transform in DAGCombiner::ReduceLoadWidth(), but the truncated load pattern can interfere with other instcombine transforms, so I'd like to allow the fold sooner.
...in that report, we have bitcasts bracketing these ops, so those could get eliminated too.
We've generally ruled out widening of loads early in IR ( LoadCombine - http://lists.llvm.org/pipermail/llvm-dev/2016-September/105291.html ), but I'm not sure if that reasoning applies to narrowing.
There's another request for narrowing in IR here, but it's a different pattern: