Unify landing pad information adding routines (NFC)
Summary:
We have `llvm::addLandingPadInfo` and `MachineFunction::addLandingPad`,
both of which add landing pad information to populate `LandingPadInfo`
but are called from different locations, which was confusing. This patch
unifies them with one `MachineFunction::addLandingPad` function, which
now has functionlities of both functions.
Reviewers: rnk
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D52428
llvm-svn: 343018