[IPSCCP] Constant fold struct argument/instructions when all the lattice values are constant.

This now should also work with the interprocedural variant of the pass.
Slightly easier now that the yak is shaved.

Differential Revision:   http://reviews.llvm.org/D22329

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275363 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed