PR 79186 (https://github.com/swiftlang/swift/pull/79186) moved one of
the mandatory passes from the C++ implementation to the Swift
implementation resulting in a compiler that is unable to build the
standard library. The pass used to ensure that inaccessible control-flow
positions after an infinite loop was marked with `unreachable` in SIL.
Since the pass is no longer running, any function that returns a value
that also has an infinite loop internally must place a fatalError after
the infinite loop or it will fail to compile as the compiler will
determine that the function does not return from all control flow paths
even though some of the paths are unreachable.
The layout of a computed key path component carries an argument buffer for captures, which has
the following layout:
```
---
captured values (subscript indices)
---
generic arguments
---
```
When we reference an externally-defined public property or subscript from a key path, and the
external declaration has a property descriptor, then the generic arguments for the external
declaration get appended to the end of this buffer, giving:
```
---
captured values (subscript indices)
---
generic arguments
---
external property's generic arguments
---
```
The convention for key path accessors to bind their generic environment is thus to unpack them
from the end of the argument buffer, so that the external keypath's accessors can find the
arguments to bind the external generic environment while still allowing the enclosing key path
to save the original captured generic environment (which may be necessary to capture the
appropriate conditional and/or retroactive `Equatable` and `Hashable` conformances for
subscript indices).
However, our code generation for binding the generic arguments out of the argument buffer
contained a flawed optimization: for a property, we know there are never any captured values,
so I had assumed that the generic parameters could always be bound from the beginning of the
argument buffer, assuming that the generic parameters make up the totality of the buffer. This
falls over for external property descriptor references when the key path itself captures a
generic environment, since the external property's expected generic environment appears after
the key path's original generic environment. We can fix this by removing the conditional
entirely, and always adjusting the offset we load the generic environment from to look at the
end of the buffer. Fixes rdar://125886333.
Enable KeyPath/AnyKeyPath/PartialKeyPath/WritableKeyPath in Embedded Swift, but
for compile-time use only:
- Add keypath optimizations into the mandatory optimizations pipeline
- Allow keypath optimizations to look through begin_borrow, to make them work
even in OSSA.
- If a use of a KeyPath doesn't optimize away, diagnose in PerformanceDiagnostics
- Make UnsafePointer.pointer(to:) transparent to allow the keypath optimization
to happen in the callers of UnsafePointer.pointer(to:).
Key paths can store an offset or a pointer in the same field. On 32-bit, the field is considered to be an offset when it's less than the 4kB zero page, and a pointer otherwise.
The check uses a signed comparison, so pointers in the top half of memory would look like negative offsets. Add a check that the offset is zero or positive to avoid this.
rdar://103886537
AnyKeyPath's debugDescription assumes there's always at least one component, but `\Type.self` produces an empty keypath. Special-case the empty case to display a `.self` component.
rdar://103237845
* initial
* it works
demangling mostly works
fix dots
printing works
add tests
add conformance to AnyKeyPath
implement SPI
subscripts fully work
comments
use cross platform image inspection
remove unnecessary comment
fix
fix issues
add conditional conformance
add types
try to fix the api-digester test
cr feedback: move impls behind flag, remove addChain(), switch statement, fallthrough instead of if-elses, move import
cr feedback: refactor switch statement
fix #ifdef
reindent, cr feedback: removes manual memory management
fix missing whitespace
fix typo
fix indentation issues
switch to regexes
checks should test in on all platforms
print types in subscripts
add test for empty subscript
Update test/api-digester/stability-stdlib-abi-without-asserts.test
Co-authored-by: Xiaodi Wu <13952+xwu@users.noreply.github.com>
add commas
fix failing test
fix stdlib annotation
cr feedback: remove global, refactor ifdef
cr feedback: switch back to manual memory management
switch to 5.8 macro
add new weakly linked functions to the allowlist
fix one more failing test
more cr feedback
more cr feedback
* fix invisible unicode
We trust the internal implementation of the stdlib to not cause any unintentional buffer overflows.
In such cases we can use the "unprotected" address-to-pointer conversions.
This avoids inserting stack protections where it's not needed.
