It looks like the devirtualizer used to have problems computing
method types in the presence of generic substitutions, covariant
returns and other things, so it would bail if a perticular set
of pre-conditions was not met on the types of original method call
and the devirtualized method call.
I don't think any of this is necessary anymore. If this patch
introduces any regressions, we need to fix the root cause instead
of re-introducing this logic.
It is important to de-serialize the devirtualized function (and its callees), especially because we must make sure that all transparent functions are de-serialized.
SILCombine did not do that. But as we have the same optimization in the Devirtualizer, it's not needed to duplicate the code in SILCombine.
The only reason we had this peephole in SILCombine is that the Devirtualizer pass could not handle partial applies.
So with this change the Devirtualizer can now also handle partial applies.
Fixes rdar://problem/30544344 (again, after my first attempt failed)
This predicate can be used to check if a given call can be devirtualized. One of the clients of this new API will be the inliner, which may want to check if a given method call becomes devirtualizable after inlining.
This reverts commit 1b3d29a163, reversing
changes made to b32424953e.
We're seeing a handful of issues from turning on inlining of generics,
so I'm reverting to unblock the bots.
It is now possible to check for any apply if it can be devirtualized without actually performing the deirtualization. This could be used e.g. by inlining heuristics.
(Headers first)
It has been generally agreed that we need to do this reorg, and now
seems like the perfect time. Some major pass reorganization is in the
works.
This does not have to be the final word on the matter. The consensus
among those working on the code is that it's much better than what we
had and a better starting point for future bike shedding.
Note that the previous organization was designed to allow separate
analysis and optimization libraries. It turns out this is an
artificial distinction and not an important goal.
