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Compiler: - Add `Forward` and `Reverse` to `DifferentiabilityKind`. - Expand `DifferentiabilityMask` in `ExtInfo` to 3 bits so that it now holds all 4 cases of `DifferentiabilityKind`. - Parse `@differentiable(reverse)` and `@differentiable(_forward)` declaration attributes and type attributes. - Emit a warning for `@differentiable` without `reverse`. - Emit an error for `@differentiable(_forward)`. - Rename `@differentiable(linear)` to `@differentiable(_linear)`. - Make `@differentiable(reverse)` type lowering go through today's `@differentiable` code path. We will specialize it to reverse-mode in a follow-up patch. ABI: - Add `Forward` and `Reverse` to `FunctionMetadataDifferentiabilityKind`. - Extend `TargetFunctionTypeFlags` by 1 bit to store the highest bit of differentiability kind (linear). Note that there is a 2-bit gap in `DifferentiabilityMask` which is reserved for `AsyncMask` and `ConcurrentMask`; `AsyncMask` is ABI-stable so we cannot change that. _Differentiation module: - Replace all occurrences of `@differentiable` with `@differentiable(reverse)`. - Delete `_transpose(of:)`. Resolves rdar://69980056.
10 lines
239 B
Swift
10 lines
239 B
Swift
import _Differentiation
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@inlinable
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@differentiable(reverse where T: Differentiable)
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public func identity<T>(_ x: T) -> T { x }
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public func foo<T: Differentiable>(_ f: @differentiable(reverse) (T) -> T = identity) -> T {
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fatalError()
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}
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