Introduced during the bring-up of the generics system in July, 2012,
Substitution (and SubstitutionList) has been completely superseded by
SubstitutionMap. R.I.P.
The goals here are four-fold:
- provide cleaner internal abstractions
- avoid IR bloat from extra bitcasts
- avoid recomputing function-type lowering information
- allow more information to be propagated from the function
access site (e.g. class_method) to the call site
Use this framework immediately for class and protocol methods.
SubstitutionList is going to be a more compact representation of
a SubstitutionMap, suitable for inline allocation inside another
object.
For now, it's just a typedef for ArrayRef<Substitution>.
Similarly to how we've always handled parameter types, we
now recursively expand tuples in result types and separately
determine a result convention for each result.
The most important code-generation change here is that
indirect results are now returned separately from each
other and from any direct results. It is generally far
better, when receiving an indirect result, to receive it
as an independent result; the caller is much more likely
to be able to directly receive the result in the address
they want to initialize, rather than having to receive it
in temporary memory and then copy parts of it into the
target.
The most important conceptual change here that clients and
producers of SIL must be aware of is the new distinction
between a SILFunctionType's *parameters* and its *argument
list*. The former is just the formal parameters, derived
purely from the parameter types of the original function;
indirect results are no longer in this list. The latter
includes the indirect result arguments; as always, all
the indirect results strictly precede the parameters.
Apply instructions and entry block arguments follow the
argument list, not the parameter list.
A relatively minor change is that there can now be multiple
direct results, each with its own result convention.
This is a minor change because I've chosen to leave
return instructions as taking a single operand and
apply instructions as producing a single result; when
the type describes multiple results, they are implicitly
bound up in a tuple. It might make sense to split these
up and allow e.g. return instructions to take a list
of operands; however, it's not clear what to do on the
caller side, and this would be a major change that can
be separated out from this already over-large patch.
Unsurprisingly, the most invasive changes here are in
SILGen; this requires substantial reworking of both call
emission and reabstraction. It also proved important
to switch several SILGen operations over to work with
RValue instead of ManagedValue, since otherwise they
would be forced to spuriously "implode" buffers.
These aren't really orthogonal concerns--you'll never have a @thick @cc(objc_method), or an @objc_block @cc(witness_method)--and we have gross decision trees all over the codebase that try to hopscotch between the subset of combinations that make sense. Stop the madness by eliminating AbstractCC and folding its states into SILFunctionTypeRepresentation. This cleans up a ton of code across the compiler.
I couldn't quite eliminate AbstractCC's information from AST function types, since SIL type lowering transiently created AnyFunctionTypes with AbstractCCs set, even though these never occur at the source level. To accommodate type lowering, allow AnyFunctionType::ExtInfo to carry a SILFunctionTypeRepresentation, and arrange for the overlapping representations to share raw values.
In order to avoid disturbing test output, AST and SILFunctionTypes are still printed and parsed using the existing @thin/@thick/@objc_block and @cc() attributes, which is kind of gross, but lets me stage in the real source-breaking change separately.
Swift SVN r27095
If a type has to be passed or returned resiliently, it
will necessarily be passed indirectly, which is already
represented in SILFunctionType. There is no need to
represent this as a separate channel of information.
NFC. Also fixes a problem where the signature cache
for ExtraData::Block was writing past the end of an
array (but into the storage for an adjacent array
which was fortunately never used).
ExtraData should also disappear as a concept, but we're
still relying on that for existential protocol witnesses.
Swift SVN r21548
This was not likely an error-free change. Where you see problems
please correct them. This went through a fairly tedious audit
before committing, but comments might have been changed incorrectly,
not changed at all, etc.
Swift SVN r7631
Remove uncurry level as a property of SILType/SILFunctionTypeInfo. During SIL type lowering, map a (Type, UncurryLevel) pair to a Swift CanType with the uncurried arguments as a Swift tuple. For example, T -> (U, V) -> W at uncurry level 1 becomes ((U, V), T) -> W--in reverse order to match the low-level calling convention. Update SILGen and IRGen all over the place for this representation change.
SILFunctionTypeInfo is still used in the SILType representation, but it's no longer load-bearing. Everything remaining in it can be derived from a Swift type.
This is an ABI break. Be sure to rebuild clean!
Swift SVN r5296
We decided we're going to want to surface fine-grained representational control of functions to the user, so move AbstractCC and the calling convention attributes into the Swift type system. Like the [thin] attribute, we don't set this in the type-checker or importer at all yet, and let SILGen set the attribute where it wants it for now.
Swift SVN r5222
Use the SIL-generated ObjC thunk symbols instead of generating them in IRGen. Kill all the now-dead IRGen OwnershipConventions stuff. Teach IRGenSILFunction how to emit a C-calling-convention function, and getFunctionType how to map a C-calling-convention function type. Fix a bug in SILGen where ObjC thunks for methods and properties from extensions weren't getting emitted.
Swift SVN r5180
Now that SIL handles function currying, CallEmission doesn't need to concern itself with forcing indirect callees. No functionality change.
Swift SVN r5143
Move AbstractCC into SILType and make it an attribute of SILTypes for functions. Add a ConvertCCInst to represent calling convention conversions. Give SILFunctions a linkage attribute. Add logic to SILGen to calculate these attributes for SILConstants based on their attached decls.
IRGen doesn't use these new attributes yet. I'll hook that up when I move mangling over.
Swift SVN r4886
Alter CalleeSource and Callee to keep their own internal vector of substitutions and concatentate multiple SpecializationExpr substitutions. Update EmitPolymorphicArguments::emit to emit arguments out of the substitution list based on the generic parameters of the current function type instead of assuming that the substitution list and generic parameter list match up.
Swift SVN r3937
This is kindof a pain in a few places where the type system
doesn't propagate canonicality. Also, member initializations
are always direct-initializations and so are allowed to use
explicit constructors, which is a hole in our canonicality
tracking. But overall I like the idea of always working
with canonical types.
Swift SVN r2893
a lot closer to successfully emitting the polymorphic-min-over-ranges
example; the main blocker right now seems to be that the witness
for a static member function is not, in fact, a static member
function at al, but a freestanding function. That's legitimate,
but it probably needs some shepherding through the witness
system.
Swift SVN r2532
