1.  Apple Swift version 5.4-dev (LLVM 7459512566cf7f4, Swift a69bf4e50992d60)
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 FuturesSync.FuturesSync)
3.  While running pass #​48793 SILFunctionTransform "AccessEnforcementOpts" on SILFunction "@$s11FuturesSync9AtomicRefC5valuexSgvs".
 for setter for value (at ./swift-source-compat-suite/project_cache/swift-futures/Sources/FuturesSync/Atomic/AtomicRef.swift:50:16)
 
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   swift-frontend                  0x0000000108daf043 swift::SILInstruction::mayRelease() const + 259
1   swift-frontend                  0x0000000108ab3558 (anonymous namespace)::AccessEnforcementOpts::run() + 7384
2   swift-frontend                  0x0000000108a6393b swift::SILPassManager::runPassOnFunction(unsigned int, swift::SILFunction*) + 2027
3   swift-frontend                  0x0000000108a64b8f swift::SILPassManager::runFunctionPasses(unsigned int, unsigned int) + 1423
4   swift-frontend                  0x0000000108a61e58 swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 72
5   swift-frontend                  0x0000000108a61df3 swift::ExecuteSILPipelineRequest::evaluate(swift::Evaluator&, swift::SILPipelineExecutionDescriptor) const + 51
6   swift-frontend                  0x0000000108a7aa9d swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::__1::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) + 29
7   swift-frontend                  0x0000000108a679ea llvm::Expected<swift::ExecuteSILPipelineRequest::OutputType> swift::Evaluator::getResultUncached<swift::ExecuteSILPipelineRequest>(swift::ExecuteSILPipelineRequest const&) + 218
8   swift-frontend                  0x0000000108a62041 swift::executePassPipelinePlan(swift::SILModule*, swift::SILPassPipelinePlan const&, bool, swift::irgen::IRGenModule*) + 65
9   swift-frontend                  0x0000000108a6a807 swift::runSILOptimizationPasses(swift::SILModule&) + 151
10  swift-frontend                  0x0000000108562cc2 swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 610
11  swift-frontend                  0x00000001084683af performCompileStepsPostSILGen(swift::CompilerInstance&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 863
12  swift-frontend                  0x0000000108467e4b performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 603
13  swift-frontend                  0x000000010845d3d4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 4756
14  swift-frontend                  0x0000000108401551 main + 801
15  libdyld.dylib                   0x00007fff20415621 start + 1

Thread 0 crashed with X86 Thread State (64-bit):
  rax: 0x0000000000000000  rbx: 0x00007fa6b605cbf0  rcx: 0x0000000000000395  rdx: 0x0000000108daf043
  rdi: 0x00007fa6b605cbf0  rsi: 0x0000000108daf048  rbp: 0x00007ffee77fc2c0  rsp: 0x00007ffee77fc2a0
   r8: 0x00007fa6b605cbb0   r9: 0x0000000000000000  r10: 0x00007fa6b6854780  r11: 0x00000000fffff001
  r12: 0x00007fa6b605cbf0  r13: 0x00007fa6b68546e8  r14: 0x00007fa6b6854728  r15: 0x00007fa6b68512cc
  rip: 0x0000000108daf043  rfl: 0x0000000000010213  cr2: 0x00007fed530b7a08