[META][AutoDiff] Tech debt from tests

[kovdan01]

Description

I've assigned preliminary priorities for the issues, but this should be revisited.

High priority:

• [ ] #54214 Note: FIXME(TF-977): Fix incorrect derivative for array literal with tuple_element_addr elements. Test: test/AutoDiff/validation-test/array.swift

• [ ] Note: FIXME(TF-584): Investigate incorrect (too big) gradient values for repeat-while loops. Test: test/AutoDiff/validation-test/control_flow.swift

Medium priority:

• [ ] Note: TODO(TF-1030): This will eventually not be an error. Test: test/AutoDiff/SILOptimizer/differentiation_diagnostics.swift (see hasImplicitlyDifferentiatedClosureDefaultArgument).

  The same error was fixed for curry thunks in #77615

• [ ] Note: FIXME: missing reverse-mode differentiability witness for foo(_:) Test: test/AutoDiff/SILGen/has_symbol.swift

• [ ] Note: FIXME(TF-1176): Some values are incorrectly not marked as active: %16, etc. Test: test/AutoDiff/SILOptimizer/activity_analysis.swift

  This is probably class-related, but need to ensure that for non-class cases the issue is not present.

• [ ] #54231 Note: TODO(TF-982): Lift this restriction and add proper support. Test: test/AutoDiff/Sema/derivative_attr_type_checking.swift

• [ ] Note: FIXME(TF-284): Fix unexpected diagnostic. Test: AutoDiff/Sema/differentiable_attr_type_checking.swift

• [ ] #54445 Note: FIXME(TF-1103): Derivative registration does not yet support @_alwaysEmitIntoClient original functions. Test: AutoDiff/stdlib/simd.swift

• [ ] #55690 Note: FIXME: Disabled due to test failure with -O Test: test/AutoDiff/validation-test/differentiable_protocol_requirements.swift

• [ ] #54628 Note: TODO(TF-433): operator ?? lowers to an active try_apply. Test: test/AutoDiff/validation-test/optional.swift

• [ ] #55084 Note: TODO: Support modify accessors Test: test/AutoDiff/validation-test/property_wrappers.swift

Low priority:

• [ ] #77762 Notes:

  1. TODO: cannot use literal true because it crashes
  2. TODO: cannot use literal false because it crashes

  Tests:

  1. test/AutoDiff/compiler_crashers_fixed/58660-conflicting-debug-info-inlining.swift
  2. test/AutoDiff/compiler_crashers_fixed/issue-58123-mutating-functions-with-control-flow.swift
  3. test/AutoDiff/validation-test/address_only_tangentvector.swift
  4. test/AutoDiff/validation-test/control_flow.swift

• [ ] #77775 Note: TODO(TF-851): Uncomment the tests below after @differentiable function SILGen thunking is fixed. Test: test/AutoDiff/SILOptimizer/generics.swift

• [ ] Note: TODO: Re-enable the boolean-literal-folding pass and fix the test accordingly Test: test/AutoDiff/SILOptimizer/activity_analysis.swift

• [ ] Note: TODO(TF-956): Improve location of active enum non-differentiability errors Test: test/AutoDiff/SILOptimizer/differentiation_control_flow_diagnostics.swift

• [ ] Note: TODO(TF-957): Improve non-differentiability errors for for-in loops Test: test/AutoDiff/SILOptimizer/differentiation_control_flow_diagnostics.swift

• [ ] Note: TODO(TF-788): Re-enable non-varied result warning. Test: test/AutoDiff/SILOptimizer/differentiation_diagnostics.swift

• [ ] Note: TODO(TF-482): Remove diagnostics when @differentiable attributes are also uniqued based on generic requirements. Test: test/AutoDiff/Sema/differentiable_attr_type_checking.swift

• [ ] Note: TODO(TF-650): It would be nice to diagnose protocol default implementation with missing @differentiable attribute. Test: test/AutoDiff/Sema/differentiable_attr_type_checking.swift

• [ ] Note: TODO(TF-632): Fix "'TangentVector' is not a member type of 'Self'" diagnostic. The underlying error should appear instead: "covariant 'Self' can only appear at the top level of method result type". Test: test/AutoDiff/Sema/differentiable_attr_type_checking.swift

• [ ] Note: FIXME: Enable test for all platforms after debugging (https://github.com/apple/swift/issues/55186). Test: test/AutoDiff/validation-test/control_flow.swift

• [ ] Note: TODO(TF-1065): Consider disallowing qualified operators / operator names Tests:

  1. test/AutoDiff/Parse/transpose_attr_parse.swift
  2. test/AutoDiff/Sema/transpose_attr_type_checking.swift

Existing issues which require discussion about priorities, semantics, etc:

Class-related:

1. 65012 and its sub-issues.

2. 52130 and its sub-issues.

Forward-mode-related:

1. 55906

2. 55650

Entire tests which require discussion whether we want to address tech debt for them:

Class-related:

1. test/AutoDiff/SILGen/vtable.swift
2. test/AutoDiff/Sema/DerivedConformances/class_differentiable.swift
3. test/AutoDiff/validation-test/class_differentiation.swift

Forward-mode-related:

1. test/AutoDiff/SILOptimizer/forward_mode_diagnostics.swift
2. test/AutoDiff/validation-test/forward_mode_simd.swift
3. test/AutoDiff/validation-test/forward_mode_simple.swift

Marked as TODO/FIXME/etc but require discussion whether we want to address them:

Class-related:

1. Note: FIXME(rdar://74380324) Test: test/AutoDiff/TBD/derivative_symbols.swift FIXMEs are related to initializer and other special functions differentiation support
2. Note: FIXME(TF-1080): Fix incorrect class property modify accessor derivative values. Test: test/AutoDiff/validation-test/inout_parameters.swift
3. Note: TODO(TF-649): Enable @derivative to override derivatives for original declaration defined in superclass. Test: test/AutoDiff/Sema/derivative_attr_type_checking.swift
4. Note: FIXME: Enable derivative registration for class property/subscript setters (https://github.com/apple/swift/issues/55542). Test: test/AutoDiff/Sema/derivative_attr_type_checking.swift This looks working for structs.
5. Note: FIXME(rdar://74380324)\ Test: test/AutoDiff/TBD/derivative_symbols.swift The FIXME is related to the following crash:

     1.      Swift version 6.1-dev (LLVM 0f86f354a7bc883, Swift e6b4e0f9f171a51)
     2.      Compiling with effective version 4.1.50
     3.      While evaluating request ASTLoweringRequest(Lowering AST to SIL for module test)
     6.      While verifying SIL function "@$s4test5ClassCyACSfcfCTJVfSUpSr".test/AutoDiff/TBD/derivative_symbols.swift

6. Note: FIXME(TF-1175): Class operands should always be marked active. Test: test/AutoDiff/validation-test/property_wrappers.swift

Forward-mode-related:

1. Note: TODO(TF-1254): Support forward-mode differentiation and test generated differentials. Test: test/AutoDiff/SILOptimizer/semantic_member_accessors_sil.swift
2. Note: TODO(TF-1173): Move floating-point mutating operation tests to test/AutoDiff/stdlib/floating_point.swift.gyb when forward-mode differentiation supports inout parameter differentiation. Test: test/AutoDiff/validation-test/inout_parameters.swift
3. Note: TODO(TF-1254): Support and test forward-mode differentiation. Test: test/AutoDiff/validation-test/property_wrappers.swift
4. Note: FIXME(TF-1033): Fix forward-mode ownership error for tuple with non-active Test: test/AutoDiff/validation-test/simple_math.swift

Linear functions related:

1. Note: TODO(TF-900, TF-902): Uncomment the following line to test loading a linear function from memory and direct calls to a linear function. Test: test/AutoDiff/SILGen/differentiable_function.swift
2. Note: TODO: Add tests for @differentiable(_linear) functions. Test: test/AutoDiff/IRGen/loadable_by_address.swift

Additional information

No response

[kovdan01]

Tagging @asl

[asl]

@JaapWijnen @rxwei