As part of this, rename TypeMetadataRecordKind to TypeReferenceKind
and consistently give it three bits of storage.
The better modelling of these type references appears to have been
sufficient to make dynamic conformance checks succeed, which is good
but unexpected.
It hass been a longstanding principle in LLVM that the presence of
debug info shall not affect code generation. This patch brings the
Swift frontend closer to this ideal:
- unconditionally emit shadow copies
- unconditionally bind type metadata
The extra allocas, bitcasts, geps, and stores being emitted get
optimized away when compiling at anything but -Onone. There are few
use-cases for compiling at -Onone without -g, so this shouldn't affect
performance for any real-world use-cases.
This adds the dllstorage annotations on the tests. This first pass gets
most of the IRGen tests passing on Windows (though has dependencies on
other changes). However, this allows for the changes to be merged more
easily as we cannot regress other platforms here.
Ensure that we use the correct python to run the python based tools.
This also allows these tools to run on Windows which will not
necessarily associate the python script with an interpreter (python).
Most of the work of this patch is just propagating metadata states
throughout the system, especially local-type-data caching and
metadata-path resolution. It took a few design revisions to get both
DynamicMetadataRequest and MetadataResponse to a shape that felt
right and seemed to make everything easier.
The design is laid out pretty clearly (I hope) in the comments on
DynamicMetadataRequest and MetadataResponse, so I'm not going to
belabor it again here. Instead, I'll list out the work that's still
outstanding:
- I'm sure there are places we're asking for complete metadata where
we could be asking for something weaker.
- I need to actually test the runtime behavior to verify that it's
breaking the cycles it's supposed to, instead of just not regressing
anything else.
- I need to add something to the runtime to actually force all the
generic arguments of a generic type to be complete before reporting
completion. I think we can get away with this for now because all
existing types construct themselves completely on the first request,
but there might be a race condition there if another asks for the
type argument, gets an abstract metadata, and constructs a type with
it without ever needing it to be completed.
- Non-generic resilient types need to be switched over to an IRGen
pattern that supports initialization suspension.
- We should probably space out the MetadataStates so that there's some
space between Abstract and Complete.
- The runtime just calmly sits there, never making progress and
permanently blocking any waiting threads, if you actually form an
unresolvable metadata dependency cycle. It is possible to set up such
a thing in a way that Sema can't diagnose, and we should detect it at
runtime. I've set up some infrastructure so that it should be
straightforward to diagnose this, but I haven't actually implemented
the diagnostic yet.
- It's not clear to me that swift_checkMetadataState is really cheap
enough that it doesn't make sense to use a cache for type-fulfilled
metadata in associated type access functions. Fortunately this is not
ABI-affecting, so we can evaluate it anytime.
- Type layout really seems like a lot of code now that we sometimes
need to call swift_checkMetadataState for generic arguments. Maybe
we can have the runtime do this by marking low bits or something, so
that a TypeLayoutRef is actually either (1) a TypeLayout, (2) a known
layout-complete metadata, or (3) a metadata of unknown state. We could
do that later with a flag, but we'll need to at least future-proof by
allowing the runtime functions to return a MetadataDependency.
Rename it to swift_initClassMetadata() just like we recently did
swift_initStructMetadata(), and add a StructLayoutFlags parameter
so we can version calls to this function in the future.
Maybe at some point this will become a separate ClassLayoutFlags
type, but at this point it doesn't matter because IRGen always
passes a value of 0.
This includes global generic and non-generic global access
functions, protocol associated type access functions,
swift_getGenericMetadata, and generic type completion functions.
The main part of this change is that the functions now need to take
a MetadataRequest and return a MetadataResponse, which is capable
of expressing that the request can fail. The state of the returned
metadata is reported as an second, independent return value; this
allows the caller to easily check the possibility of failure without
having to mask it out from the returned metadata pointer, as well
as allowing it to be easily ignored.
Also, change metadata access functions to use swiftcc to ensure that
this return value is indeed returned in two separate registers.
Also, change protocol associated conformance access functions to use
swiftcc. This isn't really related, but for some reason it snuck in.
Since it's clearly the right thing to do, and since I really didn't
want to retroactively tease that back out from all the rest of the
test changes, I've left it in.
Also, change generic metadata access functions to either pass all
the generic arguments directly or pass them all indirectly. I don't
know how we ended up with the hybrid approach. I needed to change all
the code-generation and calls here anyway in order to pass the request
parameter, and I figured I might as well change the ABI to something
sensible.
The allocation phase is guaranteed to succeed and just puts enough
of the structure together to make things work.
The completion phase does any component metadata lookups that are
necessary (for the superclass, fields, etc.) and performs layout;
it can fail and require restart.
Next up is to support this in the runtime; then we can start the
process of making metadata accessors actually allow incomplete
metadata to be fetched.
The layout changes to become relative-address based. For this to be
truly immutable (at least on Darwin), things like the RO data patterns
must be moved out of the pattern header. Additionally, compress the
pattern header so that we do not include metadata about patterns that
are not needed for the type.
Value metadata patterns just include the metadata kind and VWT.
The design here is meant to accomodate non-default instantiation
patterns should that become an interesting thing to support in the
future, e.g. for v-table specialization.
Change the "metadata base offset" variable into a "class metadata bounds"
variable that contains the base offset and the +/- bounds on the class.
Link this variable from the class descriptor when the class has a resilient
superclass; otherwise, store the +/- bounds there. Use this variable to
compute the immediate-members offset for various runtime queries. Teach the
runtime to fill it in lazily and remove the code to compute it from the
generated code for instantiation. Identify generic arguments with the start
of the immediate class metadata members / end of the {struct,enum} metadata
header and remove the generic-arguments offset from generic type descriptors.
Minimize the generic class metadata template by removing the
class header and base-class members. Add back the set of
information that's really required for instantiation.
Teach swift_allocateGenericClass how to allocate classes without
superclass metadata. Reorder generic initialization to establish
a stronger phase-ordering between allocation (the part that doesn't
really care about the generic arguments) and initialization (the
part that really does care about the generic arguments and therefore
might need to be delayed to handle metadata cycles).
A similar thing needs to happen for resilient class relocation.
This is yet another waypoint on the path towards the final
generic-metadata design. The immediate goal is to make the
pattern a private implementation detail and to give the runtime
more visibility into the allocation and caching of generic types.
All of the information contained by this field (list of property names)
is already encoded as part of the field reflection metadata and
is accessible via `swift_getFieldAt` runtime method.
This new format more efficiently represents existing information, while
more accurately encoding important information about nested generic
contexts with same-type and layout constraints that need to be evaluated
at runtime. It's also designed with an eye to forward- and
backward-compatible expansion for ABI stability with future Swift
versions.
If a generic class has non-resilient ancestry, we cannot use
the template size so far as the constant value of the base offset
variable, because the template will not contain entries for all
metadata members; instead, use metadata layout as with everything
else.
Don't emit placeholders for field offsets and vtable entries,
since they were always null. Instead, calculate the final size
of class metadata at runtime using the size of the superclass
metadata and the number of immediate members, and only copy
this prefix from the template to the instantiated metadata,
zero-filling the rest.
For this to work with non-generic resilient classes and
non-generic subclasses of generic classes, we need a new
runtime entry point to relocate non-generic class metadata,
calculating its size at runtime using the same strategy.
We had some non-deterministic behavior where depending on
validation order, synthesized accessors would end up in
different places because we would sometimes just add them
at the end of the member list.
Now add the getter right after the storage, the setter
right after the getter and the materializeForSet right
after the setter.
This changes some test output where the declaration order
did not make sense before but should otherwise have no
functional effect.
Use the generic type lowering algorithm described in
"docs/CallingConvention.rst#physical-lowering" to map from IRGen's explosion
type to the type expected by the ABI.
Change IRGen to use the swift calling convention (swiftcc) for native swift
functions.
Use the 'swiftself' attribute on self parameters and for closures contexts.
Use the 'swifterror' parameter for swift error parameters.
Change functions in the runtime that are called as native swift functions to use
the swift calling convention.
rdar://19978563
This flag is hopefully going away one day, and using it for testing
resilience is especially suspect. Just invoke the frontend directly
to build the necessary modules with -emit-module first.
Resilient classes are not fully implemented yet, and can cause
crashes at runtime; add a flag disabling them until the code is
done, to unblock standard library testing with resilience
enabled.
