[embedded] Compile-time (literal) KeyPaths for Embedded Swift #72472
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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:).
kubamracek
requested review from
phausler,
stephentyrone,
rauhul,
zoecarver and
eeckstein
kubamracek
requested review from
a team,
hborla,
slavapestov and
xedin
as code owners
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@swift-ci please test |
…nstructions for keypath operands
…retains to prevent keypath instructions from being optimized out
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@swift-ci please test |
| @@ -370,7 +370,7 @@ public struct UnsafePointer<Pointee>: _Pointer { | |||
| /// by the key path, or `nil`. | |||
| @inlinable | |||
| @_alwaysEmitIntoClient | |||
| @_unavailableInEmbedded | |||
| @_transparent | |||
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since this is applicable for both embedded and non-embedded systems what impact does that have per ABI?
@Azoy do you have any objection here?
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Yeah, I'm not sure we'd want these things to be @_transparent in the non-embedded version. That seems a bit too aggressive for this API. If you truly need this for embedded and can't just rely on the @inlinable/@_alwaysEmitIntoClient declarations, then I'd suggest guarding this with the feature flag. In terms of ABI, this shouldn't be too big of a concern because it's already visible to clients.
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Added the #if $Embedded guards.
Nope! I guess it is technically a reference type, but the compiler has an optimization to eliminate the creation of the keypath completely in the case where all you need from the keypath is to get the stored offset value, i.e. you only use the keypath to call MemoryLayout.offset(of:) or UnsafePointer.pointer(to:). That's exactly what this PR allows in Embedded Swift, and it (still) disallows actually creating keypaths objects. |
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@swift-ci please test |
Enable KeyPath/AnyKeyPath/PartialKeyPath/WritableKeyPath in Embedded Swift, but for compile-time use only:
rdar://125363334