We need special handling for protocols whose requirement
signature exists but is in a serialized state, as we
cannot run the StructuralRequirementsRequest on such
a protocol as there's no work to be done, effectively.
I am adding this since I had to go spelunking around to find the SIMCTL_CHILD_
prefix which I need to debug an app. Rather than just forgetting it again, I
thought it made sense to just document it here so I can forget it again. I also
put in a little bit of other stuff about simctl as well while I was here.
I took down my medium.com blog a few years ago, and all of the same material
in this post is now found in "Compiling Swift Generics", in docs/Generics/.
Also remove links to stuff that's extremely out of date at this point.
It's still all there in docs/ if you want to see it, but there's no
longer any reason to feature it so prominently at the top of the
README.
- Revised "Substitution Maps" chapter:
- New "Subclassing" section
- New "SIL Type Lowering" section
- New "Opaque Result Types" chapter
- Various smaller edits
New PDF will be available shortly at https://download.swift.org/docs/assets/generics.pdf.
Swift has not had user-defined conversions since before Swift 1.0.
Remove the running example from the discussion of locators. This
probably makes the explanation too opaque, but the old explanation
was useless because it was out of date.
I'll add a proper example later.
The previous algorithm was doing an iterative forward data flow analysis
followed by a reverse data flow analysis. I suspect the history here is that
it was a reverse analysis, and that didn't really work for infinite loops,
and so complexity accumulated.
The new algorithm is quite straightforward and relies on the allocations
being properly jointly post-dominated, just not nested. We simply walk
forward through the blocks in consistent-with-dominance order, maintaining
the stack of active allocations and deferring deallocations that are
improperly nested until we deallocate the allocations above it. The only
real subtlety is that we have to delay walking into dead-end regions until
we've seen all of the edges into them, so that we can know whether we have
a coherent stack state in them. If the state is incoherent, we need to
remove any deallocations of previous allocations because we cannot talk
correctly about what's on top of the stack.
The reason I'm doing this, besides it just being a simpler and hopefully
faster algorithm, is that modeling some of the uses of the async stack
allocator properly requires builtins that cannot just be semantically
reordered. That should be somewhat easier to handle with the new approach,
although really (1) we should not have runtime functions that need this and
(2) we're going to need a conservatively-correct solution that's different
from this anyway because hoisting allocations is *also* limited in its own
way.
I've attached a rather pedantic proof of the correctness of the algorithm.
The thing that concerns me most about the rewritten pass is that it isn't
actually validating joint post-dominance on input, so if you give it bad
input, it might be a little mystifying to debug the verifier failures.
Removes the underscored prefixes from the @_section and @_used attributes, making them public as @section and @used respectively. The SymbolLinkageMarkers experimental feature has been removed as these attributes are now part of the standard language. Implemented expression syntactic checking rules per SE-0492.
Major parts:
- Renamed @_section to @section and @_used to @used
- Removed the SymbolLinkageMarkers experimental feature
- Added parsing support for the old underscored names with deprecation warnings
- Updated all tests and examples to use the new attribute names
- Added syntactic validation for @section to align with SE-0492 (reusing the legality checker by @artemcm)
- Changed @DebugDescription macro to explicitly use a tuple type instead of type inferring it, to comply with the expression syntax rules
- Added a testcase for the various allowed and disallowed syntactic forms, `test/ConstValues/SectionSyntactic.swift`.
This instruction converts Builtin.ImplicitActor to Optional<any Actor>. In the
process of doing so, it masks out the bits we may have stolen from the witness
table pointer of Builtin.ImplicitActor. The bits that we mask out are the bottom
two bits of the top nibble of the TBI space on platforms that support TBI (that
is bit 60,61 on arm64). On platforms that do not support TBI, we just use the
bottom two tagged pointer bits (0,1).
By using an instruction, we avoid having to represent the bitmasking that we are
performing at the SIL level and can instead just make the emission of the
bitmasking an IRGen detail. It also allows us to move detection if we are
compiling for AArch64 to be an IRGen flag instead of a LangOpts flag.
The instruction is a guaranteed forwarding instruction since we want to treat
its result as a borrowed projection from the Builtin.ImplicitActor.
This is currently not wired up to anything. I am going to wire it up in
subsequent commits.
The reason why we are introducing this new Builtin type is to represent that we
are going to start stealing bits from the protocol witness table pointer of the
Optional<any Actor> that this type is bitwise compatible with. The type will
ensure that this value is only used in places where we know that it will be
properly masked out giving us certainty that this value will not be used in any
manner without it first being bit cleared and transformed back to Optional<any
Actor>.
The asmname attribute allows one to specify the name that will be used
when lowering a given SIL declaration to LLVM IR. It is not currently
exposed in the surface language.
Make sure this attribute round-trips through the parser and
serialization.
Part of rdar://137014448O.
docs/WebAssembly.md: update Swift SDK build instructions
Swift SDKs require Swift SDK Generator to be built with its dependencies. Additionally, now that tests for Wasm stdlib run by default, we should include required tools. Embedded Swift build is also enabled in the documented invocation.
