Static read-only arrays didn't work when passed to ObjectiveC as NSArray.
The storage class of static read-only arrays doesn't carry information about the Element type.
The new `__SwiftDeferredStaticNSArray` is generic over the element type and doesn't have to rely on the element type information of the array storage.
rdar://94185998
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.
Reduces the number of _ContiguousArrayStorage metadata.
In order to support constant time bridging we do need to set the correct
metadata when we bridge to Objective-C. This is so that the type check
succeeds when bridging back from Objective-C to reuse the storage
instance rather than bridging the elements.
To support dynamically setting the `_ContiguousArrayStorage` element
type i needed to add support for optimizing `alloc_ref_dynamic`
throughout the optimizer.
Possible future improvements:
* Use different metadata such that we can disambiguate native Swift
classes during destruction -- allowing native release rather then unknown
release usage.
* Optimize the newly added semantic function
getContiguousArrayStorageType
rdar://86171143
This abbreviation for "if and only if" is confusing to those not coming
from a background in formal mathematics, and is frequently reported as a
type by developers reading the documentation.
This commit also changes doc comments in internal and private members,
which don't become part of the public documentation, because omitting
"iff" everywhere makes it much easier to check for any later changes
that reintroduce it.
And set this option in various presets for buildbots.
Don't enable the checks by default because when linking against the OS library (which does not support COW checking) it will result in unresolved symbol errors.
So far it was handled by an availability checks against 9999 (which was a hack), but this does not work anymore.
Note, all this is only relevant for assert builds of the stdlib.
rdar://83673798
`_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.
Don't complain if the empty array buffer singleton is set to mutable.
This can happen if reserveCapacity is called with a 0-capacity for an empty array.
In this case the resulting array is still the empty array singleton.
For the compiler, it's safe to treat the empty array singleton as "mutable", because there is never anything written to an array with zero capacity:
all mutating array operations do any form of capacity/size > 0 check in addition to the uniqueness check.
Unfortunately the empty array singleton sometimes needs such special handling with is not obvious (not to say hacky).
This wrong check only fired in very specific optimization scenarios, where the inliner and the COW optimizations must play together in a certain way.
I could not find an isolated test case for this problem.
rdar://problem/71107908
Instead of doing the sanity checks by default (with an assert-build of the stdlib), only do the checks if the environment variable SWIFT_DEBUG_ENABLE_COW_SANITY_CHECKS is set to true.
The checks can give false alarms in case a binary is built against a no-assert stdlib but run with an assert-stdlib.
Therefore only do the checks if it's explicitly enabled at runtime.
rdar://problem/65475776
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.
This has two advantages:
1. It does not force the Array in memory (to pass it as inout self to the non-inlinable _createNewBuffer).
2. The new _consumeAndCreateNew is annotated to consume self. This helps to reduce unnecessary retains/releases.
The change applies for Array and ContiguousArray.
malloc introspection is a platform feature that is unavailable on
OpenBSD. There is no workaround for the feature, so we have to assume
that allocations succeed in allocating exactly the amount of memory
requested, and nothing more.
Here a new mallocSize shim is introduced so the feature check for malloc
introspection is pushed to the shims, rather than using os checks
directly from Swift. Not every use of malloc_size has been converted
yet; ManagedBuffer.swift still remains. However, this module requires
special care to fix, which will be done separately.
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
It is causing bots to fail.
* Revert "The __has_include(<os/system_version.h>) branch here wasn't quite right, we'll just use the dlsym one for now"
This reverts commit f824922456.
* Revert "Remove stdlib and runtime dependencies on Foundation and CF"
This reverts commit 3fe46e3f16.
rdar://54709269
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.
