This isn't a "complete" port of the standard library for embedded Swift, but
something that should serve as a starting point for further iterations on the
stdlib.
- General CMake logic for building a library as ".swiftmodule only" (ONLY_SWIFTMODULE).
- CMake logic in stdlib/public/core/CMakeLists.txt to start building the embedded stdlib for a handful of hardcoded target triples.
- Lots of annotations throughout the standard library to make types, functions, protocols unavailable in embedded Swift (@_unavailableInEmbedded).
- Mainly this is about stdlib functionality that relies on existentials, type erasure, metatypes, reflection, string interpolations.
- We rely on function body removal of unavailable functions to eliminate the actual problematic SIL code (existentials).
- Many .swift files are not included in the compilation of embedded stdlib at all, to simplify the scope of the annotations.
- EmbeddedStubs.swift is used to stub out (as unavailable and fatalError'd) the missing functionality.
Cleanup code in _modify accessors will only run reliably if it is put in a defer statement.
(Statements that follow the `yield` aren’t executed if the yielded-to code throws an error.)
`_copyContents(initializing:)` is a core method of Sequence, and it is used surprisingly often to copy stuff out of sequences. Array’s internal types currently have explicit implementations of it that trap (to prevent a performance bug due to the default iterator-based implementation. This has proved a bad idea, as not all code paths that end up calling `_copyContents` have actually been expunged — so we replaced a performance bug with a catastrophic correctness bug. 😥
Rather than trying to play whack-a-mole with code paths that end up in `_copyContents`, replace the traps with (relatively) efficient implementations, based on the ancient `_copyContents(subRange:initializing)` methods that have already been there all this time.
This resolves https://bugs.swift.org/browse/SR-14663.
I expect specialization will make this fix deploy back to earlier OSes in most (but unfortunately not all) cases.
* [stdlib] Deprecate MutableCollection._withUnsafeMutableBufferPointerIfSupported
In Swift 5.0, [SE-0237] introduced the public `MutableCollection.withContiguousMutableStorageIfAvailable` method. It’s time we migrated off the old, underscored variant and deprecated it.
The default `MutableCollection.sort` and `.partition(by:)` implementations are currently calling this hidden method rather than the documented interface, preventing custom Collection implementations from achieving good performance, even if they have contiguous storage.
[SE-0237]: https://github.com/apple/swift-evolution/blob/master/proposals/0237-contiguous-collection.md
* [test] Update tests for stdlib behavior changes
* Update stdlib/private/StdlibCollectionUnittest/CheckMutableCollectionType.swift
Co-authored-by: Nate Cook <natecook@apple.com>
* Update stdlib/private/StdlibCollectionUnittest/CheckMutableCollectionType.swift
Co-authored-by: Nate Cook <natecook@apple.com>
* Apply suggestions from code review
Co-authored-by: Nate Cook <natecook@apple.com>
* [test] LoggingMutableCollection: Fix logging targets
* [stdlib] Fix warning by restoring original workaround
Co-authored-by: Nate Cook <natecook@apple.com>
Introduce checking of ConcurrentValue conformances:
- For structs, check that each stored property conforms to ConcurrentValue
- For enums, check that each associated value conforms to ConcurrentValue
- For classes, check that each stored property is immutable and conforms
to ConcurrentValue
Because all of the stored properties / associated values need to be
visible for this check to work, limit ConcurrentValue conformances to
be in the same source file as the type definition.
This checking can be disabled by conforming to a new marker protocol,
UnsafeConcurrentValue, that refines ConcurrentValue.
UnsafeConcurrentValue otherwise his no specific meaning. This allows
both "I know what I'm doing" for types that manage concurrent access
themselves as well as enabling retroactive conformance, both of which
are fundamentally unsafe but also quite necessary.
The bulk of this change ended up being to the standard library, because
all conformances of standard library types to the ConcurrentValue
protocol needed to be sunk down into the standard library so they
would benefit from the checking above. There were numerous little
mistakes in the initial pass through the stsandard library types that
have now been corrected.
to check for improperly nested '@_semantic' functions.
Add a missing @_semantics("array.init") in ArraySlice found by the
diagnostic.
Distinguish between array.init and array.init.empty.
Categorize the types of semantic functions by how they affect the
inliner and pass pipeline, and centralize this logic in
PerformanceInlinerUtils. The ultimate goal is to prevent inlining of
"Fundamental" @_semantics calls and @_effects calls until the late
pipeline where we can safely discard semantics. However, that requires
significant pipeline changes.
In the meantime, this change prevents the situation from getting worse
and makes the intention clear. However, it has no significant effect
on the pass pipeline and inliner.
Use the new builtins for COW representation in Array, ContiguousArray and ArraySlice.
The basic idea is to strictly separate code which mutates an array buffer from code which reads from an array.
The concept is explained in more detail in docs/SIL.rst, section "Copy-on-Write Representation".
The main change is to use beginCOWMutation() instead of isUniquelyReferenced() and insert endCOWMutation() at the end of all mutating functions. Also, reading from the array buffer must be done differently, depending on if the buffer is in a mutable or immutable state.
All the required invariants are enforced by runtime checks - but only in an assert-build of the library: a bit in the buffer object side-table indicates if the buffer is mutable or not.
Along with the library changes, also two optimizations needed to be updated: COWArrayOpt and ObjectOutliner.
Confirmed this change on using the swift-5.2-DEVELOPMENT-SNAPSHOT-2020-01-22-a
toolchain, Apple Swift version 5.2-dev (Swift d3f0448a4c).
Fixes rdar://problem/58717942
A previous commit [1] identified and fixed a benign race on
`_swiftEmptyArrayStorage`. Unfortunately, we have some code duplication
and the fix was not applied to all the necessary places. Essentially,
we need to ensure that the "empty array storage" object that backs many
"array like types" is never written to.
I tried to improve the test to capture this, however, it is very
finicky. Currently, it does not go red on my system even when I remove
the check to avoid the benign race in Release mode.
Relevant classes: Array, ArraySlice, ContiguousArray, ArrayBuffer,
ContiguousArrayBuffer, SliceBuffer.
[1] b9b4c789f3
rdar://55161564
This fixes a major perform bug involving array initialization from any
contiguously stored collection. This is not a recent regression. This fix
results in a 10,000X speedup (that's 4 zeros) for this code path:
func initializeFromSlice(_ a: [Int]) -> [Int] {
return Array<Int>(a[...])
}
A benchmark is included.
These should be audited since some might not actually need to be
@inlinable, but for now:
- Anything public and @inline(__always) is now also @inlinable
- Anything @usableFromInline and @inline(__always) is now @inlinable
* Removing FIXME from methods also marked always/never
* Unavailable/deprecated things don't need inlining
* Trivial implementations
* Enum namespaces
* Unsafe performance of opaque/raw pointer
* Dump doesn't need to be fast
* Error paths shouldn't require inlining
* Consistency with surrounding code
* Lazy performance needs specialization
* [stdlib] Update complexity docs for seq/collection algorithms
This corrects and standardizes the complexity documentation for Sequence
and Collection methods. The use of constants is more consistent, with `n`
equal to the length of the target collection, `m` equal to the length of
a collection passed in as a parameter, and `k` equal to any other passed
or calculated constant.
* Apply notes from @brentdax about complexity nomenclature
* Change `n` to `distance` in `index(_:offsetBy:)`
* Use equivalency language more places; sync across array types
* Use k instead of n for parameter names
* Slight changes to index(_:offsetBy:) discussion.
* Update tests with new parameter names
As a general rule, it is safe to mark the implementation of hash(into:) and _rawHashValue(seed:) for @_fixed_layout structs as inlinable.
However, some structs (like String guts, Character, KeyPath-related types) have complicated enough hashing that it seems counterproductive to inline them. Mark these with @effects(releasenone) instead.
