This improves on the previous situation:
- The request ensures that the backing storage for lazy properties
and property wrappers gets synthesized first; previously it was
only somewhat guaranteed by callers.
- Instead of returning a range this just returns an ArrayRef,
which simplifies clients.
- Indexing into the ArrayRef is O(1), which addresses some FIXMEs
in the SIL optimizer.
Simplify the implementation of ClusteredBitVector by using an APInt
to represent the raw bits. This simplification will make it easier
to incrementally move to a representation of bit vectors that works
on both big- and little-endian machines.
This commit also removes reserve and reserveExtra from the API
since they were only used in one place and no longer have any effect
because memory allocation is now handled by the APInt class.
- In Sema, don't traverse nested declarations while deducing the opaque return type. This would
cause returns inside nested functions to clobber the return type of the outer function.
- In IRGen, walk the list of opaque return types we keep in the SourceFile already for type
reconstruction, instead of trying to visit them ad-hoc as part of walking the AST, since
IRGen doesn't normally walk the bodies of function decls directly.
Fixes rdar://problem/50459091
If -enable-anonymous-context-mangled-names is enabled, meaning that we assign names to
anonymous context descriptors for discovery by RemoteAST, then include opaque type descriptors
in the type metadata record table so that they can also be found at runtime by RemoteAST for
debugger support.
Previously even if a type's metadata was optimized away, we would still
emit a field descriptor, which in turn could reference nominal type
descriptors for other types via symbolic references, etc.
The old logic was confusing. The LazyTypeGlobals map would contain
entries for all referenced types, even those without lazy metadata.
And for a type with lazy metadata, the IsLazy field would begin
with a value of false -- unless it was imported.
When a non-imported type was finally visited in the AST, we would
try to "enable" lazyness for it, which meant queueing up any
metadata that had been requested prior, or immediately emitting
the metadata otherwise.
Instead, let's add a separate map that caches whether a type has
lazy metadata or not. The first time we ask for the metadata of a
type, consult this map. If the type has lazy metadata according to
the map, queue up metadata emission for the type. Otherwise, emit
metadata eagerly when the type is visited in the AST.
Field offset vectors are always filled out with either zero or the static layout's offset, depending on the metadata initialization strategy. This change means that the static layout's offset will only be non-zero for properties with a statically-known layout. Existing runtimes doing dynamic class layout assign class properties a zero offset if the field offset vector entry is zero and the property is zero-sized. So this effectively brings the compiler into accord with the runtime (for all newly-compiled Swift code, which will eventually be all Swift code because the current public releases of Swift 5 are not yet considered ABI-stable) and guarantees a zero value for the offset everywhere.
Since the runtime will agree with the compiler about the zero value of the offset, the compiler can continue to emit such offset variables as constant. The exception to this rule is if the class has non-fragile ObjC ancestry, in which case the ObjC runtime (which is not aware of this special rule for empty fields) will attempt to slide it along with everything else.
Fixes rdar://48031465, in which the `FixedClassMetadataBuilder` for a class with a legacy-fixed layout was writing a non-zero offset for an empty field into the field offset vector, causing the runtime to not apply the special case and thus to compute a non-zero offset, which it then attempted to copy into the global field offset variable, which the compiler had emitted as a true-constant zero.
This is essentially a long-belated follow-up to Arnold's #12606.
The key observation here is that the enum-tag-single-payload witnesses
are strictly more powerful than the XI witnesses: you can simulate
the XI witnesses by using an extra case count that's <= the XI count.
Of course the result is less efficient than the XI witnesses, but
that's less important than overall code size, and we can work on
fast-paths for that.
The extra inhabitant count is stored in a 32-bit field (always present)
following the ValueWitnessFlags, which now occupy a fixed 32 bits.
This inflates non-XI VWTs on 32-bit targets by a word, but the net effect
on XI VWTs is to shrink them by two words, which is likely to be the
more important change. Also, being able to access the XI count directly
should be a nice win.
Like we did for structs, make it so that tuple types can also get extra inhabitants from whichever element with the most, not only the first. This lets us move all of the extra inhabitant handling functionality between structs and tuples in IRGen up to the common RecordTypeInfo CRTP base.
This allows us to layout-optimize Optional<T> when T is a struct with an
extra-inhabitant-bearing field anywhere in its definition, not only at
the beginning. rdar://problem/43019427
I believe the warning is erroneous and filed a bug against clang.
GenStruct.cpp:290:19: warning: unused type alias 'super' [-Wunused-local-typedef]
rdar://40626108
Type of elements contained by field offsets vector can be adjusted
to 32-bit integers (from being pointer sized) to safe space in the
binary since segment size is limited to 4 GB.
Resolves: rdar://problem/36560486
Clang allows C structs to have zero-sized array fields for things like trailing buffers. Lower these correctly into Swift types in IRGen so that Swift codegen knows to treat them as empty types. Fixes rdar://problem/31042794.
If a type has the same layout as one of the basic integer types, or has a single refcounted pointer representation, we can use prefab value witness tables from the runtime instead of instantiating new ones. This saves quite a bit of code size, particularly in the Apple SDK overlays, where there are lots of swift_newtype wrappers and option set structs.
The key path pattern needs to include a reference to the external descriptor, along with hooks for lowering its type arguments and indices, if any. The runtime will need to instantiate and interpolate the external component when the key path object is instantiated.
While we're here, let's also reserve some more component header bytes for future expansion, since this is an ABI we're going to be living with for a while.
- Create the value witness table as a separate global object instead
of concatenating it to the metadata pattern.
- Always pass the metadata to the runtime and let the runtime handle
instantiating or modifying the value witness table.
- Pass the right layout algorithm version to the runtime; currently
this is always "Swift 5".
- Create a runtime function to instantiate single-case enums.
Among other things, this makes the copying of the VWT, and any
modifications of it, explicit and in the runtime, which is more
future-proof.
The emitInitializeFieldOffsetVector() function used for
class metadata is now almost identical to the logic used
for structs. Refactor the code used for classes and also
use it to layout structs.
