[SR-13250] AutoDiff test failure: test/AutoDiff/validation-test/differentiable_protocol_requirements.swift

[dan-zheng]

Previous ID	SR-13250
Radar	rdar://problem/74094125
Original Reporter	@dan-zheng
Type	Task

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Task, AutoDiff
Assignee	None
Priority	Medium

md5: 24a514bc4a5ba11871c72f5b0d01ec85

Issue Description:

Test failure reported here: #32948 (comment)

07:40:40 ******************** TEST 'Swift(linux-x86_64) :: AutoDiff/validation-test/differentiable_protocol_requirements.swift' FAILED ********************
07:40:40 Script:
07:40:40 --
07:40:40 : 'RUN: at line 1';   rm -rf "/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/test-linux-x86_64/AutoDiff/validation-test/Output/differentiable_protocol_requirements.swift.tmp" && mkdir -p "/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/test-linux-x86_64/AutoDiff/validation-test/Output/differentiable_protocol_requirements.swift.tmp" && /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swiftc -target x86_64-unknown-linux-gnu -toolchain-stdlib-rpath  -module-cache-path '/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/swift-test-results/x86_64-unknown-linux-gnu/clang-module-cache' -swift-version 4  -Xfrontend -ignore-module-source-info -O -module-cache-path '/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/swift-test-results/x86_64-unknown-linux-gnu/clang-module-cache' /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/swift/test/AutoDiff/validation-test/differentiable_protocol_requirements.swift -o /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/test-linux-x86_64/AutoDiff/validation-test/Output/differentiable_protocol_requirements.swift.tmp/a.out -module-name main  && echo /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/test-linux-x86_64/AutoDiff/validation-test/Output/differentiable_protocol_requirements.swift.tmp/a.out && /usr/bin/env DYLD_LIBRARY_PATH='/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/lib/swift/linux/x86_64' LD_LIBRARY_PATH='/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/lib/swift/linux/x86_64:/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/libdispatch-linux-x86_64' SIMCTL_CHILD_DYLD_LIBRARY_PATH='/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/lib/swift/linux/x86_64'  /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/test-linux-x86_64/AutoDiff/validation-test/Output/differentiable_protocol_requirements.swift.tmp/a.out
07:40:40 --
07:40:40 Exit Code: 254
07:40:40 
07:40:40 Command Output (stderr):
07:40:40 --
07:40:40 swift-frontend: /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/swift/lib/SIL/IR/SILInstructions.cpp:2436: static swift::ConvertFunctionInst *swift::ConvertFunctionInst::create(swift::SILDebugLocation, swift::SILValue, swift::SILType, swift::SILFunction &, swift::SILOpenedArchetypesState &, bool): Assertion `opTI->isABICompatibleWith(resTI, F).isCompatible() && "Can not convert in between ABI incompatible function types"' failed.
07:40:40 Stack dump:
07:40:40 0. Program arguments: /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend -frontend -c -primary-file /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/swift/test/AutoDiff/validation-test/differentiable_protocol_requirements.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -module-cache-path /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/swift-test-results/x86_64-unknown-linux-gnu/clang-module-cache -swift-version 4 -O -ignore-module-source-info -module-name main -o /home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/tmp/differentiable_protocol_requirements-b9935d.o 
07:40:40 1. Swift version 5.3-dev (LLVM e3586932cc1c511, Swift 71f6797c8fc2c27)
07:40:40 2. While evaluating request ExecuteSILPipelineRequest(Run pipelines { PrepareOptimizationPasses, EarlyModulePasses, HighLevel,Function+EarlyLoopOpt, HighLevel,Module+StackPromote, Serialize, MidLevel,Function, ClosureSpecialize, LowLevel,Function, LateLoopOpt, SIL Debug Info Generator } on SIL for main.main)
07:40:40 3. While running pass #​17491 SILFunctionTransform "Devirtualizer" on SILFunction "@$s0131AD__$s4main11derivatives2at2in23DifferentiationUnittest7TrackedVySfG_A3HtAH_xmtAA12FunctionsOfXRzlFA2HcfU___vjp_src_0_wrt_0_4main12mnO04main04TestmN1XV_Tg5".
07:40:40  for expression at [/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/swift/test/AutoDiff/validation-test/differentiable_protocol_requirements.swift:104:30 - line:104:47] RangeText="{ x in F(x: x).x "
07:40:40  #​0 0x000000000573a7f4 PrintStackTraceSignalHandler(void*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x573a7f4)
07:40:40  #​1 0x00000000057382f0 llvm::sys::RunSignalHandlers() (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x57382f0)
07:40:40  #​2 0x000000000573aaea SignalHandler(int) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x573aaea)
07:40:40  #​3 0x00007ff57e877390 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
07:40:40  #​4 0x00007ff57d1dc428 raise (/lib/x86_64-linux-gnu/libc.so.6+0x35428)
07:40:40  #​5 0x00007ff57d1de02a abort (/lib/x86_64-linux-gnu/libc.so.6+0x3702a)
07:40:40  #​6 0x00007ff57d1d4bd7 (/lib/x86_64-linux-gnu/libc.so.6+0x2dbd7)
07:40:40  #​7 0x00007ff57d1d4c82 (/lib/x86_64-linux-gnu/libc.so.6+0x2dc82)
07:40:40  #​8 0x0000000001144967 swift::ConvertFunctionInst::create(swift::SILDebugLocation, swift::SILValue, swift::SILType, swift::SILFunction&, swift::SILOpenedArchetypesState&, bool) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x1144967)
07:40:40  #​9 0x0000000000ca0542 swift::castValueToABICompatibleType(swift::SILBuilder*, swift::SILLocation, swift::SILValue, swift::SILType, swift::SILType) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xca0542)
07:40:40 #&#8203;10 0x0000000000c80b41 replaceApplySite(swift::SILBuilder&, swift::SILLocation, swift::ApplySite, swift::SILValue, swift::SubstitutionMap, llvm::ArrayRef<swift::SILValue>, swift::SILFunctionConventions, llvm::ArrayRef<swift::SILValue>) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xc80b41)
07:40:40 #&#8203;11 0x0000000000c819b9 swift::tryDevirtualizeWitnessMethod(swift::ApplySite, swift::OptRemark::Emitter*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xc819b9)
07:40:40 #&#8203;12 0x0000000000c820dd swift::tryDevirtualizeApply(swift::ApplySite, swift::ClassHierarchyAnalysis*, swift::OptRemark::Emitter*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xc820dd)
07:40:40 #&#8203;13 0x0000000000b81ac2 (anonymous namespace)::Devirtualizer::run() (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xb81ac2)
07:40:40 #&#8203;14 0x0000000000abb564 swift::SILPassManager::runPassOnFunction(unsigned int, swift::SILFunction*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xabb564)
07:40:40 #&#8203;15 0x0000000000abc3fb swift::SILPassManager::runFunctionPasses(unsigned int, unsigned int) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xabc3fb)
07:40:40 #&#8203;16 0x0000000000abf4ee swift::SILPassManager::execute() (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xabf4ee)
07:40:40 #&#8203;17 0x0000000000ab9788 swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xab9788)
07:40:40 #&#8203;18 0x0000000000ab974c swift::ExecuteSILPipelineRequest::evaluate(swift::Evaluator&, swift::SILPipelineExecutionDescriptor) const (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xab974c)
07:40:40 #&#8203;19 0x0000000000ad593b swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xad593b)
07:40:40 #&#8203;20 0x0000000000ac4641 llvm::Expected<swift::ExecuteSILPipelineRequest::OutputType> swift::Evaluator::getResultUncached<swift::ExecuteSILPipelineRequest>(swift::ExecuteSILPipelineRequest const&) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xac4641)
07:40:40 #&#8203;21 0x0000000000ab9955 swift::executePassPipelinePlan(swift::SILModule*, swift::SILPassPipelinePlan const&, bool, swift::irgen::IRGenModule*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xab9955)
07:40:40 #&#8203;22 0x0000000000ac7588 swift::runSILOptimizationPasses(swift::SILModule&) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0xac7588)
07:40:40 #&#8203;23 0x00000000006838db swift::CompilerInstance::performSILProcessing(swift::SILModule*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x6838db)
07:40:40 #&#8203;24 0x000000000050e6ef performCompileStepsPostSILGen(swift::CompilerInstance&, std::unique_ptr<swift::SILModule, std::default_delete<swift::SILModule> >, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x50e6ef)
07:40:40 #&#8203;25 0x00000000004ffd5d swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x4ffd5d)
07:40:40 #&#8203;26 0x000000000047cf9b main (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x47cf9b)
07:40:40 #&#8203;27 0x00007ff57d1c7830 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x20830)
07:40:40 #&#8203;28 0x000000000047ca59 _start (/home/buildnode/jenkins/workspace/oss-swift-package-linux-ubuntu-16_04/build/buildbot_linux/swift-linux-x86_64/bin/swift-frontend+0x47ca59)
07:40:40 
<unknown>:0: error: unable to execute command: Aborted
07:40:40 <unknown>:0: error: compile command failed due to signal 6 (use -v to see invocation)
07:40:40 
07:40:40 --
07:40:40 
07:40:40 ********************

[rxwei]

@swift-ci create

[kovdan01]

A minimized reproducer based on test/AutoDiff/validation-test/differentiable_protocol_requirements.swift:

import DifferentiationUnittest

protocol FunctionsOfX: Differentiable {
  @differentiable(reverse)
  init(x: Tracked<Float>)
  @differentiable(reverse)
  var x: Tracked<Float> { get }
}

struct TestFunctionsOfX: FunctionsOfX {
  @differentiable(reverse)
  init(x: Tracked<Float>) { self.x = x }
  var x: Tracked<Float>
}

// This causes a crash
func derivatives<F: FunctionsOfX>(at x: Tracked<Float>, of: F.Type)
  -> Tracked<Float> { return gradient(at: x) { x in F(x: x).x } }
derivatives(at: 2.0, of: TestFunctionsOfX.self)

// This compiles OK
let x = Tracked<Float>(42)
gradient(at: x) { x in TestFunctionsOfX(x: x).x }

Note that it is crucial to have Tracked<Float>, with just Float the code compiles normally.

Tagging @asl

[asl]

Only reproduced with -O, the assertion is

Assertion failed: ((!F || opTI->isABICompatibleWith(resTI, *F).isCompatible()) && "Can not convert in between ABI incompatible function types"), function create, file SILInstructions.cpp, line 2817.

Happens in tryDevirtualizeApply:

 for expression at [tracked.swift:18:46 - line:18:63] RangeText="{ x in F(x: x).x "
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x0000000109fd5cdc llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000109fd442c llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000109fd6320 SignalHandler(int) + 292
3  libsystem_platform.dylib 0x000000019cff0184 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000019cfbaf70 pthread_kill + 288
5  libsystem_c.dylib        0x000000019cec7908 abort + 128
6  libsystem_c.dylib        0x000000019cec6c1c err + 0
7  swift-frontend           0x000000010a0b7f70 swift::ConvertFunctionInst::create(swift::SILDebugLocation, swift::SILValue, swift::SILType, swift::SILModule&, swift::SILFunction*, bool, swift::ValueOwnershipKind) (.cold.5) + 0
8  swift-frontend           0x0000000105ba2b50 swift::ConvertFunctionInst::onlyConvertsSubstitutions() const + 0
9  swift-frontend           0x00000001055d0d50 swift::SILBuilder::createConvertFunction(swift::SILLocation, swift::SILValue, swift::SILType, bool) + 132
10 swift-frontend           0x00000001059577a0 swift::castValueToABICompatibleType(swift::SILBuilder*, swift::SILPassManager*, swift::SILLocation, swift::SILValue, swift::SILType, swift::SILType, llvm::ArrayRef<swift::SILInstruction*>) + 1120
11 swift-frontend           0x0000000105902d64 replaceApplySite(swift::SILBuilder&, swift::SILPassManager*, swift::SILLocation, swift::ApplySite, swift::SILValue, swift::SubstitutionMap, llvm::ArrayRef<swift::SILValue>, swift::SILFunctionConventions, llvm::ArrayRef<swift::SILValue>) + 288
12 swift-frontend           0x00000001059040e8 swift::tryDevirtualizeWitnessMethod(swift::SILPassManager*, swift::ApplySite, swift::OptRemark::Emitter*, bool) + 1644
13 swift-frontend           0x000000010590498c swift::tryDevirtualizeApply(swift::SILPassManager*, swift::ApplySite, swift::ClassHierarchyAnalysis*, swift::OptRemark::Emitter*, bool) + 232

[asl]

So, devirtualizer wants to convert @callee_guaranteed (@in Tracked<Float>, @thick TestFunctionsOfX.Type) -> (@out TestFunctionsOfX, @owned @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed Tracked<Float>) -> @out τ_0_0 for <TestFunctionsOfX.TangentVector> to @callee_guaranteed (@in Tracked<Float>, @thick TestFunctionsOfX.Type) -> (@out TestFunctionsOfX, @owned @callee_guaranteed @substituted <τ_0_0> (@in Tracked<Float>) -> @out τ_0_0 for <TestFunctionsOfX.TangentVector> hence the assertion.

The original instruction is

  %12 = partial_apply [callee_guaranteed] %9<TestFunctionsOfX>() : $@convention(witness_method: FunctionsOfX) <τ_0_0 where τ_0_0 : FunctionsOfX> (@in Tracked<Float>, @thick τ_0_0.Type) -> (@out τ_0_0, @owned @callee_guaranteed @substituted <τ_0_0> (@in Tracked<Float>) -> @out τ_0_0 for <τ_0_0.TangentVector>) // user: %15

The devirtualized one:

  %11 = partial_apply [callee_guaranteed] %10() : $@convention(witness_method: FunctionsOfX) (@in Tracked<Float>, @thick TestFunctionsOfX.Type) -> (@out TestFunctionsOfX, @owned @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed Tracked<Float>) -> @out τ_0_0 for <TestFunctionsOfX.TangentVector>)

And the thunk we're calling is

sil private [transparent] [thunk] [ossa] @AD__$s7tracked16TestFunctionsOfXVAA0cD1XA2aDP1xx23DifferentiationUnittest7TrackedVySfG_tcfCTW_jvp_SU : $@convention(witness_method: FunctionsOfX) (@in Tracked<Float>, @thick TestFunctionsOfX.Type) -> (@out TestFunctionsOfX, @owned @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed Tracked<Float>) -> @out τ_0_0 for <TestFunctionsOfX.TangentVector>) {

(note the @in vs @in_guaranteed difference).

Here is the original code in

  %9 = witness_method $τ_0_0, #FunctionsOfX.init!allocator.jvp.SU.<Self where Self : FunctionsOfX> : <Self where Self : FunctionsOfX> (Self.Type) -> (Tracked<Float>) -> Self : $@convention(witness_method: FunctionsOfX) <τ_0_0 where τ_0_0 : FunctionsOfX> (@in Tracked<Float>, @thick τ_0_0.Type) -> (@out τ_0_0, @owned @callee_guaranteed @substituted <τ_0_0> (@in Tracked<Float>) -> @out τ_0_0 for <τ_0_0.TangentVector>) // user: %10
  %10 = partial_apply [callee_guaranteed] %9<τ_0_0>() : $@convention(witness_method: FunctionsOfX) <τ_0_0 where τ_0_0 : FunctionsOfX> (@in Tracked<Float>, @thick τ_0_0.Type) -> (@out τ_0_0, @owned @callee_guaranteed @substituted <τ_0_0> (@in Tracked<Float>) -> @out τ_0_0 for <τ_0_0.TangentVector>) // user: %13

Here is the part of witness table:

sil_witness_table hidden TestFunctionsOfX: FunctionsOfX module tracked {
  base_protocol Differentiable: TestFunctionsOfX: Differentiable module tracked
  method #FunctionsOfX.init!allocator: <Self where Self : FunctionsOfX> (Self.Type) -> (Tracked<Float>) -> Self : @$s7tracked16TestFunctionsOfXVAA0cD1XA2aDP1xx23DifferentiationUnittest7TrackedVySfG_tcfCTW    // protocol witness for FunctionsOfX.init(x:) in conformance TestFunctionsOfX
  method #FunctionsOfX.init!allocator.jvp.SU.<Self where Self : FunctionsOfX>: <Self where Self : FunctionsOfX> (Self.Type) -> (Tracked<Float>) -> Self : @AD__$s7tracked16TestFunctionsOfXVAA0cD1XA2aDP1xx23DifferentiationUnittest7TrackedVySfG_tcfCTW_jvp_SU // AD__$s7tracked16TestFunctionsOfXVAA0cD1XA2aDP1xx23DifferentiationUnittest7TrackedVySfG_tcfCTW_jvp_SU

And we are having thunk with @in vs @in_guaranteed difference:

sil private [transparent] [thunk] @AD__$s7tracked16TestFunctionsOfXVAA0cD1XA2aDP1xx23DifferentiationUnittest7TrackedVySfG_tcfCTW_jvp_SU : $@convention(witness_method: FunctionsOfX) (@in Tracked<Float>, @thick TestFunctionsOfX.Type) -> (@out TestFunctionsOfX, @owned @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed Tracked<Float>) -> @out τ_0_0 for <TestFunctionsOfX.TangentVector>) {

[asl]

Tagging @JaapWijnen

[kovdan01]

Some additional context:

The function type of witness table entry has @in_guaranteed for its argument. This convention is applied at SILGenModule::emitProtocolWitness->auto witnessSILFnType = getNativeSILFunctionType(/*...*/). We call getSILFunctionTypeForConventions(DefaultConventions(NormalParameterConvention::Guaranteed)) there, that's the reason why we have guaranteed (DefaultConvention::getIndirectParameter() == ParameterConvention::Indirect_In_Guaranteed).

On the other hand, in SILFunctionType::getAutoDiffDerivativeFunctionType->getAutoDiffDifferentialType we have diffParams with the same conventions which params from the original function (@in for this particular case).

In getAutoDiffPullbackType (and in VJPCloner) we have several places where Indirect_In_Guaranteed is applied explicitly. Obviously, a dummy attempt to apply In_Guaranteed for entries of diffParams if param.getConvention() == ParameterConvention::Indirect_In leads to tests failing with assertions in verifier (due to attempt of mutating @in_guaranteed). It looks like that pullback cloner is built with @in_guaranteed in mind, and probably the same should be done for forward-mode.