Unavailable enum elements cannot be instantiated at runtime without invoking
UB. Therefore the optimizer can consider a basic block unreachable if its only
predecessor is a block that terminates in a switch instruction matching an
unavailable enum element. Furthermore, removing the switch instruction cases
that refer to unavailable enum elements is _mandatory_ when
`-unavailable-decl-optimization=complete` is specified because otherwise
lowered IR for these instructions could refer to enum tag accessors that will
not be lowered, resulting in a failure during linking.
Resolves rdar://113872720.
In SILGenPattern, we need to be able to unforward cleanups when we explode
tuples. Thus we can't use RValue in SILGenPattern since it may implicitly
explode tuples (which without modifying RValue itself we can not
unforward). This patch removes a specific RValue usage that we can replace with
the use of a ManagedValue instead.
rdar://49903264
This is a large patch; I couldn't split it up further while still
keeping things working. There are four things being changed at
once here:
- Places that call SILType::isAddressOnly()/isLoadable() now call
the SILFunction overload and not the SILModule one.
- SILFunction's overloads of getTypeLowering() and getLoweredType()
now pass the function's resilience expansion down, instead of
hardcoding ResilienceExpansion::Minimal.
- Various other places with '// FIXME: Expansion' now use a better
resilience expansion.
- A few tests were updated to reflect SILGen's improved code
generation, and some new tests are added to cover more code paths
that previously were uncovered and only manifested themselves as
standard library build failures while I was working on this change.
When we have a private resilient enum that is resilient because one of
its payloads is resilient but we have disabled resilience in the
context of lowering the enum as a class member (sigh), we must consider
it's payload's layout enum in the minimal domain (ignore the private
visibility) because we don't truly know the layout.
rdar://41308521
If a struct has fixed layout but contains fields which are opaque,
or if the struct itself is opaque, use a metadata accessor function
instead of loading the metadata directly.
Let's say that A and B are two structs defined in the same module,
and B has a fixed size. This patch adds support for these two cases:
1) Fixed-layout struct A contains resilient struct B
2) Resilient struct A contains resilient struct B
In case 1),
a) Inside X: A is fixed-size and has constant metadata
i) Direct metadata access can be performed on A and B
ii) Direct field access can be performed on A and B
d) Outside X: B has an opaque layout
i) Metadata accessor must be called for A and B
ii) Fields of A do not have constant offsets, instead the offsets
must be loaded from type metadata
Case 2) is the same as above except ii) does not apply, since fields
of resilient structs are manipulated via accessors.
Eventually, we will use metadata accessor functions for all public
struct and enum types.
Add a new ResilientStructTypeInfo. This is a singleton since
all resilient structs have opaque payloads and are accessed
through value witness tables.
With this in place, flesh out IRGenModule::isResilient() and
use the new singleton to convert resilient structs.
Note that the old isResilient() was hard-coded to report that
all Clang-imported classes are "resilient". Now that this has
been unified with NominalTypeDecl::hasFixedLayout(), we will
report Clang-imported classes are "resilient" at the SIL level.
This should not introduce any semantic differences at this
point.
Unlike SIL, where currently resilient types are always resilient
even when used from the same module, IRGen is able to perform
direct manipulation of resilient structs from the current
module, since IRGen's type lowering has a resilience scope
plumbed through.
Note that we do not yet support laying out structs and classes
containing resilient fields -- this will come in a future patch.
