In case of `var` initializations, SILGen creates a dynamic begin/end_access pair around the initialization store.
If it's an initialization (and not a re-assign) it's guanranteed that it's an exlusive access and we can convert the access to an `[init] [static]` access.
https://github.com/apple/swift/issues/66496
Replaced the -disable-copy-propagation flag with
-enable-copy-propagation=false where the latter is a new multi-var
-enable-copy-propagation= which can take one of three values:
- true
- requested-passes-only
- false
In a designated initializer of a non-root class, 'self' becomes
fully initialized after the 'super.init' call, at which point
escaping uses of 'self' become valid, and releases of 'self' are
lowered to a 'strong_release' instruction, which runs the
deinitializer.
In a root class, 'self' becomes fully initialized after all stored
properties have been initialized, at which point escaping uses of
'self' become valid.
However, DI would still lower a conditional destroy of 'self' by
destroying any initialized stored properties and freeing the object
with 'dealloc_partial_ref'. This is incorrect, because 'self' may
have escaped.
In the non-conditional destroy case, we correctly lowered the
release to a 'strong_release' if all stored properties are known
to be initialized.
Fix DI to handle the conditional destroy case by first checking if all
bits in the control variable are set, and releasing the instance with
'strong_release' if so. The 'dealloc_partial_ref' is only emitted
if not at least one stored property was not initialized.
This ensures that we don't deallocate an instance that may have
escaped.
Fixes <https://bugs.swift.org/browse/SR-13439>, <rdar://problem/67746791>,
<https://bugs.swift.org/browse/SR-13355>, <rdar://problem/67361228>.
