Extending the mangling of symbolic references to also include indirect
symbolic references. This allows mangled names to refer to context
descriptors (both type and protocol) not in the current source file.
For now, only permit indirect symbolic references within the current module,
because remote mirrors (among other things) is unable to handle relocations.
Co-authored-by: Joe Groff <jgroff@apple.com>
Default associated conformance accessors will be used in default
witness tables to fill in associated conformances for defaulted
associated types. Add (de|re|)mangling support for them and make them
linking entities in IRGen.
Associated conformance descriptors are aliases that refer to associated
conformance requirements within a protocol descriptor’s list of
requirements. They will be used to provide protocol resilience against
the addition of new associated conformance requirements (which only makes
sense for newly-introduced, defaulted associated types).
When an associated type witness has a default, record that as part of
the protocol and emit a default associated type metadata accessor into the
default witness table. This allows a defaulted associated type to be
added to a protocol resiliently.
This is another part of rdar://problem/44167982, but it’s still very
limiting because the new associated type cannot have any conformances.
Introduce an alias that refers one element prior to the start of a
protocol descriptor’s protocol requirements. This can be subtracted from
an associated type descriptor address to determine the offset of the
associated type accessor within a corresponding witness table. The code
generation for the latter is not yet implemented.
For example:
public struct Mystruct<T> {
func testit<U>(x: T, u: U) {
typealias Myalias = AnyObject
}
}
In this case the Myalias has a generic function as context.
This patch adds SIL-level debug info support for variables whose
static type is rewritten by an optimizer transformation. When a
function is (generic-)specialized or inlined, the static types of
inlined variables my change as they are remapped into the generic
environment of the inlined call site. With this patch all inlined
SILDebugScopes that point to functions with a generic signature are
recursively rewritten to point to clones of the original function with
new unique mangled names. The new mangled names consist of the old
mangled names plus the new substituions, similar (or exactly,
respectively) to how generic specialization is handled.
On libSwiftCore.dylib (x86_64), this yields a 17% increase in unique
source vars and a ~24% increase in variables with a debug location.
rdar://problem/28859432
rdar://problem/34526036
The central thrust of this patch is to get these metadata initializations
off of `swift_once` and onto the metadata-request system where we can
properly detect and resolve dependencies. We do this by first introducing
runtime support for resolving metadata requests for "in-place"
initializations (committed previously) and then teaching IRGen to actually
generate code to use them (this patch).
A non-trivial amount of this patch is just renaming and refactoring some of
existing infrastructure that was being used for in-place initializations to
try to avoid unnecessary confusion.
The remaining cases that are still using `swift_once` resolution of
metadata initialization are:
- non-generic classes that can't statically fill their superclass or
have resilient internal layout
- foreign type metadata
Classes require more work because I'd like to switch at least the
resilient-superclass case over to using a pattern much more like what
we do with generic class instantiation. That is, I'd like in-place
initialization to be reserved for classes that actually don't need
relocation.
Foreign metadata should also be updated to the request/dependency scheme
before we declare ABI stability. I'm not sure why foreign metadata
would ever require a type to be resolved, but let's assume it's possible.
Fixes part of SR-7876.
For now, the accessors have been underscored as `_read` and `_modify`.
I'll prepare an evolution proposal for this feature which should allow
us to remove the underscores or, y'know, rename them to `purple` and
`lettuce`.
`_read` accessors do not make any effort yet to avoid copying the
value being yielded. I'll work on it in follow-up patches.
Opaque accesses to properties and subscripts defined with `_modify`
accessors will use an inefficient `materializeForSet` pattern that
materializes the value to a temporary instead of accessing it in-place.
That will be fixed by migrating to `modify` over `materializeForSet`,
which is next up after the `read` optimizations.
SIL ownership verification doesn't pass yet for the test cases here
because of a general fault in SILGen where borrows can outlive their
borrowed value due to being cleaned up on the general cleanup stack
when the borrowed value is cleaned up on the formal-access stack.
Michael, Andy, and I discussed various ways to fix this, but it seems
clear to me that it's not in any way specific to coroutine accesses.
rdar://35399664
This patch adds SIL-level debug info support for variables whose
static type is rewritten by an optimizer transformation. When a
function is (generic-)specialized or inlined, the static types of
inlined variables my change as they are remapped into the generic
environment of the inlined call site. With this patch all inlined
SILDebugScopes that point to functions with a generic signature are
recursively rewritten to point to clones of the original function with
new unique mangled names. The new mangled names consist of the old
mangled names plus the new substituions, similar (or exactly,
respectively) to how generic specialization is handled.
On libSwiftCore.dylib (x86_64), this yields a 17% increase in unique
source vars and a ~24% increase in variables with a debug location.
rdar://problem/28859432
rdar://problem/34526036
When mangling a specialized use of a typealias in a protocol, we end up
with a "bound generic protocol" mangling, with the one substitution
replacing Self with some other type. Handle de-mangling and
re-mangling of such names.
Fixes rdar://problem/41549126.
The mangling of generic typealiases was using the underlying type’s generic
arguments rather than the generic arguments for the typealias itself.
Directly encode the generic arguments from the substitution map instead.
Also address some related issues with remangling generic typealiases.
Fixes rdar://problem/41444286.
Protocol name mangling didn’t always go through a path that allowed the use
of standard substitutions. Enable standard substitutions for protocol name
manglings where they make sense.
Removes ~277k from the standard library binary size.
LLVM r334283 changed StringRef::split(char) to be implemented using
StringRef::split(StringRef), which is not defined inline. Because Swift
uses StringRef without linking LLVM's libSupport.a, we can only use
functions that are defined inline in the headers. Swift currently only
builds LLVM for the host, so we cannot link libSupport.a without building
it for every target, which would be a big change. Instead, this changes
a few places in Swift to avoid using those split and rsplit functions.
rdar://problem/41029268
Witness tables for conformances that require runtime instantiation
should not be public, because it is an error to directly reference
such a symbol from outside the module.
Use a different mangling for witness table patterns and give them
non-public linkage.
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.
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.
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.
This makes resolving mangled names to nominal types in the same module more efficient, and for eventual secrecy improvements, also allows types in the same module to be referenced from mangled typerefs without encoding any source-level name information about them.
A "retroactive" protocol conformance is a conformance that is provided
by a module that is neither the module that defines the protocol nor
the module that defines the conforming type. It is possible for such
conformances to conflict at runtime, if defined in different modules
that were not both visible to the compiler at the same time.
When mangling a bound generic type, also mangle retroactive protocol
conformances that were needed to satisfy the generic requirements of
the generic type. This prevents name collisions between (e.g.) types
formed using retroactive conformances from different modules. The
impact on the size of the mangling is expected to be relatively small,
because most conformances are not retroactive.
Fixes the ABI part of rdar://problem/14375889.
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.
