Vectors with different number of elements of the same element type can have

Vectors with different number of elements of the same element type can have
the same allocation size but different primitive sizes(e.g., <3xi32> and
<4xi32>).  When ScalarRepl promotes them, it can't use a bit cast but
should use a shuffle vector instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129472 91177308-0d34-0410-b5e6-96231b3b80d8