The PR #81766 introduced some concrete SIMD operations, but
`init(repeating:)` was temporarily disabled due to differentiation
testing break. See:
7a00619065
This PR contains two changes:
1. Define custom derivatives for concrete `init(repeating:)` so we do
not fall into non-differentiability error diagnostic.
2. Add a fix to SIL linker so differentiability witness lookup is done
when the original function has both `@_alwaysEmitIntoClient` and
`@_transparent`. Similar changes were introduced previously in #78908,
but they only handled `@_alwaysEmitIntoClient` without `@_transparent`.
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Consider an `@_alwaysEmitIntoClient` function and a custom derivative
defined
for it. Previously, such a combination resulted different errors under
different
circumstances.
Sometimes, there were linker errors due to missing derivative function
symbol -
these occurred when we tried to find the derivative in a module, while
it
should have been emitted into client's code (and it did not happen).
Sometimes, there were SIL verification failures like this:
```
SIL verification failed: internal/private function cannot be serialized or serializable: !F->isAnySerialized() || embedded
```
Linkage and serialization options for the derivative were not handled
properly,
and, instead of PublicNonABI linkage, we had Private one which is
unsupported
for serialization - but we need to serialize `@_alwaysEmitIntoClient`
functions
so the client's code is able to see them.
This patch resolves the issue and adds proper handling of custom
derivatives
of `@_alwaysEmitIntoClient` functions. Note that either both the
function and
its custom derivative or none of them should have
`@_alwaysEmitIntoClient`
attribute, mismatch in this attribute is not supported.
The following cases are handled (assume that in each case client's code
uses
the derivative).
1. Both the function and its derivative are defined in a single file in
one module.
2. Both the function and its derivative are defined in different files
which
are compiled to a single module.
3. The function is defined in one module, its derivative is defined in
another
module.
4. The function and the derivative are defined as members of a protocol
extension in two separate modules - one for the function and one for the
derivative. A struct conforming the protocol is defined in the third
module.
5. The function and the derivative are defined as members of a struct
extension in two separate modules - one for the function and one for the
derivative.
The changes allow to define derivatives for methods of `SIMD`.
Fixes#54445
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`Differentiable` conformance derivation now supports
`Differentiable.zeroTangentVectorInitializer`.
There are two potential cases:
1. Memberwise derivation: done when `TangentVector` can be initialized memberwise.
2. `{ TangentVector.zero }` derivation: done as a fallback.
`zeroTangentVectorInitializer` is a closure that produces a zero tangent vector,
capturing minimal necessary information from `self`.
It is an instance property, unlike the static property `AdditiveArithmetic.zero`,
and should be used by the differentiation transform for correctness.
Remove `Differentiable.zeroTangentVectorInitializer` dummy default implementation.
Update stdlib `Differentiable` conformances and tests.
Clean up DerivedConformanceDifferentiable.cpp cruft.
Resolves TF-1007.
Progress towards TF-1008: differentiation correctness for projection operations.
