This is currently disabled by default. Building the client library can be enabled with the CMake option SWIFT_BUILD_CLIENT_RETAIN_RELEASE, and using the library can be enabled with the flags -Xfrontend -enable-client-retain-release.
To improve retain/release performance, we build a static library containing optimized implementations of the fast paths of swift_retain, swift_release, and the corresponding bridgeObject functions. This avoids going through a stub to make a cross-library call.
IRGen gains awareness of these new functions and emits calls to them when the functionality is enabled and the target supports them. Two options are added to force use of them on or off: -enable-client-retain-release and -disable-client-retain-release. When enabled, the compiler auto-links the static library containing the implementations.
The new calls also use LLVM's preserve_most calling convention. Since retain/release doesn't need a large number of scratch registers, this is mostly harmless for the implementation, while allowing callers to improve code size and performance by spilling fewer registers around refcounting calls. (Experiments with an even more aggressive calling convention preserving x2 and up showed an insignificant savings in code size, so preserve_most seems to be a good middle ground.)
Since the implementations are embedded into client binaries, any change in the runtime's refcounting implementation needs to stay compatible with this new fast path implementation. This is ensured by having the implementation use a runtime-provided mask to check whether it can proceed into its fast path. The mask is provided as the address of the absolute symbol _swift_retainRelease_slowpath_mask_v1. If that mask ANDed with the object's current refcount field is non-zero, then we take the slow path. A future runtime that changes the refcounting implementation can adjust this mask to match, or set the mask to all 1s to disable the old embedded fast path entirely (as long as the new representation never uses 0 as a valid refcount field value).
As part of this work, the overall approach for bridgeObjectRetain is changed slightly. Previously, it would mask off the spare bits from the native pointer and then call through to swift_retain. This either lost the spare bits in the return value (when tail calling swift_retain) which is problematic since it's supposed to return its parameter, or it required pushing a stack frame which is inefficient. Now, swift_retain takes on the responsibility of masking off spare bits from the parameter and preserving them in the return value. This is a trivial addition to the fast path (just a quick mask and an extra register for saving the original value) and makes bridgeObjectRetain quite a bit more efficient when implemented correctly to return the exact value it was passed.
The runtime's implementations of swift_retain/release are now also marked as preserve_most so that they can be tail called from the client library. preserve_most is compatible with callers expecting the standard calling convention so this doesn't break any existing clients. Some ugly tricks were needed to prevent the compiler from creating unnecessary stack frames with the new calling convention. Avert your eyes.
To allow back deployment, the runtime now has aliases for these functions called swift_retain_preservemost and swift_release_preservemost. The client library brings weak definitions of these functions that save the extra registers and call through to swift_retain/release. This allows them to work correctly on older runtimes, with a small performance penalty, while still running at full speed on runtimes that have the new preservemost symbols.
Although this is only supported on Darwin at the moment, it shouldn't be too much work to adapt it to other ARM64 targets. We need to ensure the assembly plays nice with the other platforms' assemblers, and make sure the implementation is correct for the non-ObjC-interop case.
rdar://122595871
This experimental feature will be used to force the compiler to treat `Swift`
runtime availability as separate from platform availability when compiling for
targets that have the Swift runtime built-in.
_SwiftifyImport assumes types like Swift.Int, Swift.UnsafePointer<T> and
Swift.Span<T> are available. This is not the case when building the
stdlib itself. Disable safe interop in the stdlib to prevent errors.
This currently has no effect, but will when this feature is enabled by
default, which I have manually tested.
The _SwiftifyImport macro is emitted into an unnamed buffer and then
parsed, pretending it was in the header all along. This makes it hard to
add `expected-note` comments for `diag::in_macro_expansion` when they
point here. That's okay, because the macro expansion has already been
pointed out by `expected-expansion` directives. But
-verify-ignore-unrelated is too blunt of a tool, so this adds
-verify-ignore-macro-note to ignore these specific diagnostics.
This pass has been disabled since a very long time (because it's terrible for code size).
It does not work for OSSA. Therefore it cannot be enabled anymore (as is) once we have OSSA throughout the pipeline.
So it's time to completely remove it.
This PR introduces three new instrumentation flags and plumbs them
through to IRGen:
1. `-ir-profile-generate` - enable IR-level instrumentation.
2. `-cs-profile-generate` - enable context-sensitive IR-level
instrumentation.
3. `-ir-profile-use` - IR-level PGO input profdata file to enable
profile-guided optimization (both IRPGO and CSIRPGO)
**Context:**
https://forums.swift.org/t/ir-level-pgo-instrumentation-in-swift/82123
**Swift-driver PR:** https://github.com/swiftlang/swift-driver/pull/1992
**Tests and validation:**
This PR includes ir level verification tests, also checks few edge-cases
when `-ir-profile-use` supplied profile is either missing or is an
invalid IR profile.
However, for argument validation, linking, and generating IR profiles
that can later be consumed by -cs-profile-generate, I’ll need
corresponding swift-driver changes. Those changes are being tracked in
https://github.com/swiftlang/swift-driver/pull/1992
Add support for the `Swift` availability domain, which represents availability
with respect to the Swift runtime. Use of this domain is restricted by the
experimental feature `SwiftRuntimeAvailability`.
We already have -suppress-warnings and -suppress-remarks; this patch
adds support for suppressing notes too. Doing so is useful for -verify
tests where we don't really care about the emitted notes.
This adds the implementation required for later changing the default
behaviour of the -verify flag to error when diagnostics are emitted
in buffers other than the main file and files added with
-verify-additional-file. To keep the current behaviour, use the flag
-verify-ignore-unrelated. This flag is added as a no-op so that tests
can start using it before the new behaviour is enabled by default.
With some changes that I am making, we will no longer need this flag at the SIL
level, so we can just make it an IRGen flag (which it really should have been
in the first place).
Replace the one-off compiler flag for Library Evolution with an
optional language feature. This makes the
`hasFeature(LibraryEvolution)` check work in an `#if`, and is
otherwise just cleanup.
Tracked by rdar://161125572.
It's very, very easy to make a mistake that will cause broken
serialized modules. Until that's no longer true, at least tell folks
that they are heading into uncharted waters, as we do with
`@_implementationOnly` imports.
The flags "-import-bridging-header" and "-import-pch" import a bridging
header, treating the contents as a public import. Introduce
"internal-" variants of both flags that provide the same semantics,
but are intended to treat the imported contents as if they came in
through an internal import. This is just plumbing of the options for
the moment.
This command-line option hasn't been Objective-C specific ever, really.
Make the language-independent spelling the primary one to make that
more obvious.
This does not enable it by default. Use either of the flags:
```
-enable-copy-propagation
-enable-copy-propagation=always
```
to enable it in -Onone. The previous frontend flag
`-enable-copy-propagation=true` has been renamed to
`-enable-copy-propagation=optimizing`, which is currently default.
rdar://107610971
These restrictions will generally manifest as failures of various forms
later in the compiler process. Enable the diagnostics to give earlier
feedback to help stay within the bounds of Embedded Swift.
Fixes rdar://121205043.
This flag dumps all imports for each SourceFile after it's gone through
import resolution. It is only intended for testing purposes.
There are other ways to print imports, but they don't correspond 1:1 to
the imports actually resolved, which is a bit problematic when testing
implicit clang module imports.
swift_coroFrameAlloc was introduced in the Swift 6.2 runtime. Give it
the appropriate availability in IRGen, so that it gets weak
availability when needed (per the deployment target). Then, only
create the stub function for calling into swift_coroFrameAlloc or
malloc (when the former isn't available) when we're back-deploying to
a runtime prior to Swift 6.2. This is a small code size/performance
win when allocating coroutine frames on Swift 6.2-or-newer platforms.
This has a side effect of fixing a bug in Embedded Swift, where the
swift_coroFrameAlloc was getting unconditionally set to have weak
external linkage despite behind defined in the same LLVM module
(because it comes from the standard library).
Fixes rdar://149695139 / issue #80947.
If a .swiftinterface file does not include an explicit `-language-mode` option
(or its predecessor `-swift-version`) and needs to be built as a dependency of a
client compilation, then the invocation to build the module from interface
would end up inheriting the language mode that the client code is built with.
This can result in spurious type checking diagnostics or even mis-compilation.
To ensure that a module interface is always built using the language mode that
its source code was originally built with, require an explicit `-language-mode`
option when emitting swiftinterface files.
In https://github.com/swiftlang/swift/pull/84307 this diagnostic was downgraded
to a warning. The failures it caused in PR testing should now be resolved.
Resolves rdar://145168219.
Downgrade the new error in https://github.com/swiftlang/swift/pull/84244 to a
warning.
The PR smoke test build is using a different build system that is failing to
pass `-swift-version` arguments when building various stdlib modules. That
needs to be fixed, but for now we also need to unblock CI.
If a `.swiftinterface` file does not include an explicit `-language-mode`
option (or its predecessor `swift-version`) and needs to be built as a
dependency of a client compilation, then the invocation to build the module
from interface would end up inheriting the language mode that the client code
is built with. This can result in spurious type checking diagnostics or even
mis-compilation. To ensure that a module interface is always built using the
language mode that its source code was originally built with, require an
explicit `-language-mode` option when emitting swiftinterface files.
Resolves rdar://145168219.
