This commit eliminates the need for mark uninitialized fixup by updating the
compiler so that we now emit:
```
%0 = alloc_box
%1 = mark_uninitialized %0
%2 = project_box %1
...
destroy_value %1
```
Instead of:
```
%0 = alloc_box
%1 = project_box %0
%2 = mark_uninitialized %1
...
destroy_value %0
```
Now that the first type of code is generated, I can change project_box to only
take guaranteed arguments. This will ensure that the OSSA ARC optimizer can
eliminate copies of boxes without needing to understand the usage of the
project_box.
I also removed the -verify-sil-ownership flag in favor of a disable flag
-disable-sil-ownership-verifier. I used this on only two tests that still need
work to get them to pass with ownership, but whose problems are well understood,
small corner cases. I am going to fix them in follow on commits. I detail them
below:
1. SILOptimizer/definite_init_inout_super_init.swift. This is a test case where
DI is supposed to error. The only problem is that we crash before we error since
the code emitting by SILGen to trigger this error does not pass ownership
invariants. I have spoken with JoeG about this and he suggested that I fix this
earlier in the compiler. Since we do not run the ownership verifier without
asserts enabled, this should not affect compiler users. Given that it has
triggered DI errors previously I think it is safe to disable ownership here.
2. PrintAsObjC/extensions.swift. In this case, the signature generated by type
lowering for one of the thunks here uses an unsafe +0 return value instead of
doing an autorelease return. The ownership checker rightly flags this leak. This
is going to require either an AST level change or a change to TypeLowering. I
think it is safe to turn this off since it is such a corner case that it was
found by a test that has nothing to do with it.
rdar://43398898
I have been meaning to do this change for a minute, but kept on putting it off.
This describes what is actually happening and is a better name for the option.
In a previous commit, I banned in the verifier any SILValue from producing
ValueOwnershipKind::Any in preparation for this.
This change arises out of discussions in between John, Andy, and I around
ValueOwnershipKind::Trivial. The specific realization was that this ownership
kind was an unnecessary conflation of the a type system idea (triviality) with
an ownership idea (@any, an ownership kind that is compatible with any other
ownership kind at value merge points and can only create). This caused the
ownership model to have to contort to handle the non-payloaded or trivial cases
of non-trivial enums. This is unnecessary if we just eliminate the any case and
in the verifier separately verify that trivial => @any (notice that we do not
verify that @any => trivial).
NOTE: This is technically an NFC intended change since I am just replacing
Trivial with Any. That is why if you look at the tests you will see that I
actually did not need to update anything except removing some @trivial ownership
since @any ownership is represented without writing @any in the parsed sil.
rdar://46294760
I am doing this so I can start writing DI tests without this lowering occuring.
There never was a real reason for this code to be in DI beyond convenience. Now
it just makes writing tests more difficult. To prevent any test delta, I changed
all current DI tests to run this pass after DI.
