GlobalISel: support same ConstantExprs as Instructions.

It's more than just inttoptr, but the others can't be tested until we have
support for non-trivial constants (they currently get unavoidably folded to a
ConstantInt).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278303 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed