[InlineCost] Mark functions accessing varargs as not viable.

This prevents functions accessing varargs from being inlined if they
have the alwaysinline attribute.

Reviewers: efriedma, rnk, davide

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D42556


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323619 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed