When inlining a function and adding its inner call sites to the

When inlining a function and adding its inner call sites to the
candidate set for subsequent inlining, try to simplify the arguments to
the inner call site now that inlining has been performed.

The goal here is to propagate and fold constants through deeply nested
call chains. Without doing this, we loose the inliner bonus that should
be applied because the arguments don't match the exact pattern the cost
estimator uses.

Reviewed on IRC by Benjamin Kramer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152556 91177308-0d34-0410-b5e6-96231b3b80d8