[SR-13529] Forward-mode differentiation: thunk generation crash

[dan-zheng]

Previous ID	SR-13529
Radar	rdar://problem/73388885
Original Reporter	@dan-zheng
Type	Bug
Status	Closed
Resolution	Invalid

Additional Detail from JIRA

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

md5: bf77f0398bb89e022f17050e14447b10

Issue Description:

Reproducer:

import _Differentiation

struct Tensor<Scalar> {}
extension Tensor: Differentiable where Scalar: Differentiable {}

@differentiable
func foo<Scalar: Differentiable>(_ x: Tensor<Scalar>) -> Tensor<Scalar> { x }

@differentiable(wrt: x)
func bar<Scalar: Differentiable>(
  x: Tensor<Scalar>,
  body: @differentiable (Tensor<Scalar>) -> Tensor<Scalar> = foo
) -> Tensor<Scalar> {
  body(x)
}

$ swiftc -Xfrontend -enable-experimental-forward-mode-differentiation fwd.swift
Assertion failed: (signature || !origType->hasTypeParameter()), function initSwiftType, file include/swift/SIL/AbstractionPattern.h, line 395.
Stack dump:
0.  Program arguments: build/Ninja-ReleaseAssert+swift-DebugAssert/swift-macosx-x86_64/bin/swift-frontend -frontend -c -primary-file fwd.swift -target x86_64-apple-darwin19.4.0 -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -color-diagnostics -enable-experimental-forward-mode-differentiation -target-sdk-version 10.16 -module-name fwd -o /var/folders/m_/6f7q8zfs3n9fr0c_4gy8840m00hc_q/T/fwd-db5651.o
1.  Swift version 5.3-dev (LLVM 14a10d635b229fb, Swift 39c6ee112f95980)
2.  While evaluating request ExecuteSILPipelineRequest(Run pipelines { Mandatory Diagnostic Passes + Enabling Optimization Passes } on SIL for fwd.fwd)
3.  While running pass #​489 SILModuleTransform "Differentiation".
4.  While processing // differentiability witness for bar<A>(x:body:)
sil_differentiability_witness hidden [parameters 0] [results 0] <Scalar where Scalar : Differentiable> @$s3fwd3bar1x4bodyAA6TensorVyxGAG_A2GXFts14DifferentiableRzlF : $@convention(thin) <Scalar where Scalar : Differentiable> (Tensor<Scalar>, @differentiable @noescape @callee_guaranteed @substituted <τ_0_0, τ_0_1> (Tensor<τ_0_0>) -> Tensor<τ_0_1> for <Scalar, Scalar>) -> Tensor<Scalar> {
}

 on SIL function "@$s3fwd3bar1x4bodyAA6TensorVyxGAG_A2GXFts14DifferentiableRzlF".
 for 'bar(x:body:)' (at fwd.swift:10:1)
5.  While generating JVP and differential for SIL function "@$s3fwd3bar1x4bodyAA6TensorVyxGAG_A2GXFts14DifferentiableRzlF".
 for 'bar(x:body:)' (at fwd.swift:10:1)
0  swift-frontend           0x0000000113695ca5 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift-frontend           0x0000000113694c58 llvm::sys::RunSignalHandlers() + 248
2  swift-frontend           0x00000001136962a6 SignalHandler(int) + 262
3  libsystem_platform.dylib 0x00007fff6e0115fd _sigtramp + 29
4  libsystem_platform.dylib 000000000000000000 _sigtramp + 18446603338670598688
5  libsystem_c.dylib        0x00007fff6dee7808 abort + 120
6  libsystem_c.dylib        0x00007fff6dee6ac6 err + 0
7  swift-frontend           0x000000010e907432 swift::Lowering::AbstractionPattern::initSwiftType(swift::CanGenericSignature, swift::CanType, swift::Lowering::AbstractionPattern::Kind) + 130
8  swift-frontend           0x000000010e90739f swift::Lowering::AbstractionPattern::AbstractionPattern(swift::CanGenericSignature, swift::CanType) + 111
9  swift-frontend           0x000000010e8f0b45 swift::Lowering::AbstractionPattern::AbstractionPattern(swift::CanGenericSignature, swift::CanType) + 37
10 swift-frontend           0x000000010e79e1a4 (anonymous namespace)::SILTypeSubstituter::visitType(swift::CanType) + 660
11 swift-frontend           0x000000010e79e5d8 swift::CanTypeVisitor<(anonymous namespace)::SILTypeSubstituter, swift::CanType>::visitNominalType(swift::CanTypeWrapper<swift::NominalType>) + 40
12 swift-frontend           0x000000010e79d7a8 swift::CanTypeVisitor<(anonymous namespace)::SILTypeSubstituter, swift::CanType>::visitStructType(swift::CanTypeWrapper<swift::StructType>) + 40
13 swift-frontend           0x000000010e79c983 swift::CanTypeVisitor<(anonymous namespace)::SILTypeSubstituter, swift::CanType>::visit(swift::CanType) + 1251
14 swift-frontend           0x000000010e79ee2d (anonymous namespace)::SILTypeSubstituter::substInterface(swift::SILResultInfo) + 61
15 swift-frontend           0x000000010e786654 (anonymous namespace)::SILTypeSubstituter::substSILFunctionType(swift::CanTypeWrapper<swift::SILFunctionType>, bool) + 2244
16 swift-frontend           0x000000010e79dd17 (anonymous namespace)::SILTypeSubstituter::visitSILFunctionType(swift::CanTypeWrapper<swift::SILFunctionType>) + 39
17 swift-frontend           0x000000010e79cedb swift::CanTypeVisitor<(anonymous namespace)::SILTypeSubstituter, swift::CanType>::visit(swift::CanType) + 2619
18 swift-frontend           0x000000010e785742 (anonymous namespace)::SILTypeSubstituter::subst(swift::SILType) + 50
19 swift-frontend           0x000000010e785626 swift::SILType::subst(swift::Lowering::TypeConverter&, llvm::function_ref<swift::Type (swift::SubstitutableType*)>, llvm::function_ref<swift::ProtocolConformanceRef (swift::CanType, swift::Type, swift::ProtocolDecl*)>, swift::CanGenericSignature, bool) const + 486
20 swift-frontend           0x000000010e785805 swift::SILType::subst(swift::SILModule&, llvm::function_ref<swift::Type (swift::SubstitutableType*)>, llvm::function_ref<swift::ProtocolConformanceRef (swift::CanType, swift::Type, swift::ProtocolDecl*)>, swift::CanGenericSignature, bool) const + 149
21 swift-frontend           0x000000010db486fe swift::autodiff::buildThunkType(swift::SILFunction*, swift::CanTypeWrapper<swift::SILFunctionType>&, swift::CanTypeWrapper<swift::SILFunctionType>&, swift::GenericEnvironment*&, swift::SubstitutionMap&, bool, swift::autodiff::DifferentiationThunkKind)::$_3::operator()(swift::CanTypeWrapper<swift::SILFunctionType>) const + 190
22 swift-frontend           0x000000010db47e98 swift::autodiff::buildThunkType(swift::SILFunction*, swift::CanTypeWrapper<swift::SILFunctionType>&, swift::CanTypeWrapper<swift::SILFunctionType>&, swift::GenericEnvironment*&, swift::SubstitutionMap&, bool, swift::autodiff::DifferentiationThunkKind) + 1112
23 swift-frontend           0x000000010db48988 swift::autodiff::getOrCreateReabstractionThunk(swift::SILOptFunctionBuilder&, swift::SILModule&, swift::SILLocation, swift::SILFunction*, swift::CanTypeWrapper<swift::SILFunctionType>, swift::CanTypeWrapper<swift::SILFunctionType>) + 328
24 swift-frontend           0x000000010db4a78a swift::autodiff::reabstractFunction(swift::SILBuilder&, swift::SILOptFunctionBuilder&, swift::SILLocation, swift::SILValue, swift::CanTypeWrapper<swift::SILFunctionType>, std::__1::function<swift::SubstitutionMap (swift::SubstitutionMap)>) + 330
25 swift-frontend           0x000000010dae4d7d swift::autodiff::JVPCloner::Implementation::visitApplyInst(swift::ApplyInst*) + 6557

The crash occurs while attempting to generate a reabstraction thunk for a function-typed value (differential callee) during forward-mode differentiation.

[airspeedswift]

@swift-ci create

[rxwei]

Forward-mode is not supported and will be deprecated. Closing.