philipturner
commented
2 years ago This reproducer can be narrowed down further. I don't think it's about whether the function is differentiable, because the reproducer works with [Float]. In that case, the function would be differentiable, but it would still crash.
import _Differentiation
@differentiable(reverse)
func readAll(from root: Float) -> [Float] {
// [Int] can be any array type. It can also be initialized outside of the
// function.
return [Int]().map { _ in root }
}The crash appeared between the 2021-01-27 and 2021-04-18 snapshots. On 2021-01-27, there seems to be a pre-existing bug that triggered before this one. To reproduce it on that toolchain, you must change @differentiable(reverse) to @differentiable.
Crash on 2021-04-18 toolchain
``` (base) philipturner@m1-max-mbp bug % swiftc file.swift error: compile command failed due to signal 6 (use -v to see invocation) Assertion failed: (!NodePtr->isKnownSentinel()), function operator*, file /Users/buildnode/jenkins/workspace/oss-swift-package-macos/llvm-project/llvm/include/llvm/ADT/ilist_iterator.h, line 138. Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the project and the crash backtrace. Stack dump: 0. Program arguments: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2021-04-18-a.xctoolchain/usr/bin/swift-frontend -frontend -c -primary-file file.swift -target x86_64-apple-macosx12.0 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -color-diagnostics -new-driver-path /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2021-04-18-a.xctoolchain/usr/bin/swift-driver -resource-dir /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2021-04-18-a.xctoolchain/usr/lib/swift -module-name file -target-sdk-version 12.3.0 -o /var/folders/qn/86czb43d3pv03bfnxvb3x66h0000gn/T/TemporaryDirectory.dciRaZ/file-1.o 1. Apple Swift version 5.5-dev (LLVM fb5a91b4e892ed9, Swift f17142883421ec0) 2. While evaluating request ExecuteSILPipelineRequest(Run pipelines { Mandatory Diagnostic Passes + Enabling Optimization Passes } on SIL for file.file) 3. While running pass #31 SILModuleTransform "Differentiation". 4. While processing // differentiability witness for readAll(from:) sil_differentiability_witness hidden [reverse] [parameters 0] [results 0] @$s4file7readAll4fromSaySfGSf_tF : $@convention(thin) (Float) -> @owned ArrayCrash on 2021-01-27 toolchain
``` (base) philipturner@m1-max-mbp bug % swiftc file.swift Begin Error in Function: '$s4file7readAll4fromSaySfGSf_tFTJpSpSr' Error! Found a leaked owned value that was never consumed. Value: %3 = copy_value %0 : $ArrayOn the 2020-07-22 toolchain, it fails gracefully when using [Int](), saying it can't be differentiated because of unsupported control flow. Changing to [Float]() doesn't eliminate the error, so maybe this reproducer is non-differentiable in all forms. Thus, it could be about emitting a proper diagnostic for non-differentiable functions.
jkshtj
Additional Detail from JIRA
| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | Bug, AutoDiff | |Assignee | None | |Priority | Medium | md5: ae84dcea4936a75e0d58dcc65a61c26eIssue Description:
The following simple file involving differentiation through a map function that uses keypaths triggers an assertion failure of "Assertion failed: (!NodePtr->isKnownSentinel()), function operator*, file ilist_iterator.h, line 138.":
To reproduce, place the above in a file and run `swiftc file.swift` to hit the assertion failure. This is present in current nightly snapshots and is not a recent regression.
My guess is that we're missing a diagnostic stating that the above isn't differentiable, in a similar manner to the missing diagnostic in SR-15201.
This is the full text of the assertion failure: