[Hexagon] Implement buildVector32 and buildVector64 as utility functions

Change LowerBUILD_VECTOR to use those functions. This commit will tempora-
rily affect constant vector generation (it will generate constant-extended
values instead of non-extended combines), but the code for the general case
should be better. The constant selection part will be fixed later.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318877 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed