There's a potential change in dereferenceability attribute semantics in the nearish future. See llvm-dev thread "RFC: Decomposing deref(N) into deref(N) + nofree" and D99100 for context.
This change simply adds appropriate attributes to tests to keep transform logic exercised under both old and new/proposed semantics. Note that for many of these cases, O3 would infer exactly these attributes on the test IR.
This change handles the idiomatic pattern of a dereferenceable object being passed to a call which can not free that memory. There's a couple other tests which need more one-off attention, they'll be handled in another change.
Use context to prove that load can be safely executed at a point where load is being hoisted.
Postpone the decision about safety of speculative load execution till the moment we know
where we hoist load and check safety at that context.
Reviewers: nikic, fhahn, mkazantsev, lebedev.ri, efriedma, reames
Reviewed By: reames, mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D88725
