Although nonescaping closures are representationally trivial pointers to their
on-stack context, it is useful to model them as borrowing their captures, which
allows for checking correct use of move-only values across the closure, and
lets us model the lifetime dependence between a closure and its captures without
an ad-hoc web of `mark_dependence` instructions.
During ownership elimination, We eliminate copy/destroy_value instructions and
end the partial_apply's lifetime with an explicit dealloc_stack as before,
for compatibility with existing IRGen and non-OSSA aware passes.
Pass a BasicCalleeAnalysis instance to isDeinitBarrier. This enables
LexicalDestroyHoisting to hoist destroys over applies of functions which
are not deinit barriers.
Added new C++-to-Swift callback for isDeinitBarrier.
And pass it CalleeAnalysis so it can depend on function effects. For
now, the argument is ignored. And, all callers just pass nullptr.
Promoted to API the mayAccessPointer component predicate of
isDeinitBarrier which needs to remain in C++. That predicate will also
depends on function effects. For that reason, it too is now passed a
BasicCalleeAnalysis and is moved into SILOptimizer.
Also, added more conservative versions of isDeinitBarrier and
maySynchronize which will never consider side-effects.
IterableBackwardReachability just requires an iterable list of gens.
ShrinkBorrowScope, LexicalDestroyHoisting, and SSADestroyHoisting all
need to be able to check whether a given instruction is scope ending
quickly. Use a SmallSetVector rather than a SmallVector for the gens in
all three.
The new utility, to be run as part of copy propagation, hoists
destroy_values of owned lexical values up to deinit barriers. It is
heavily based on the rewritten ShrinkBorrowScope.
