Lower `@llvm.global_dtors` using `__cxa_atexit` on MachO

[yln]

Summary

For MachO, lower @llvm.global_dtors into @llvm_global_ctors with
__cxa_atexit calls to avoid emitting the deprecated __mod_term_func.

Reuse the existing WebAssemblyLowerGlobalDtors.cpp to accomplish this.

Enable fallback to the old behavior via Clang driver flag
(-fregister-global-dtors-with-atexit) or llc / code generation flag
(-lower-global-dtors-via-cxa-atexit). This escape hatch will be
removed in the future.

[yln]

Hi @Orlando and @RKSimon, would you be able to confirm that this version avoids the previous opt: Unknown command line argument '-lower-global-dtors' error?

Lit invocation:
env LIT_FILTER='dtor' ninja check-llvm

[yln]

It looks like all tests succeed for x64 debian:
https://buildkite.com/llvm-project/premerge-checks/builds/83802#c5002be5-e01c-46fc-a767-50fe6f854465

[yln]

FYI - you could have continued to use this phab for review, it makes it easier to compare the changes you've made

I will definitely do this next time!

Diff to D121327:
I've added 2 additional calls to initializeLowerGlobalDtorsLegacyPassPass(). The one in the constructor of the legacy pass should ensure that the pass is always registered.

[yln]

Plan to land tomorrow morning. Test passes on the Debian bot:

PASS: LLVM :: Transforms/LowerGlobalDestructors/lower-global-dtors.ll (72299 of 93291)

[RKSimon]

LGTM - but please hang around after you commit

[yln]

In D121736#3389251, @RKSimon wrote:

LGTM - but please hang around after you commit

Thanks! Looks like this time it worked out. Let me know if there are any other problems.

[zequanwu]

Hi, this causes crash on Mac building bot.
Here is the reduced repro:

opt -lower-global-dtors /tmp/reduced.ll -o /dev/null

$ cat /tmp/reduced.ll
%struct.mach_header = type { i32, i32, i32, i32, i32, i32, i32 }

@__dso_handle = external global %struct.mach_header
@llvm.global_dtors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 1, void ()* undef, i8* null }]

[yln]

Thank you @zequanwu, for providing the minimized reproducer! It really made fixing this much easier! :)

I've re-landed the change and added a test specifically for this issue: lower-global-dtors-existing-dos_handle.ll

clang/lib/CodeGen/BackendUtil.cpp

static bool initTargetOptions(DiagnosticsEngine &Diags,
   case LangOptions::FPM_Fast:
     Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
     break;
   }
 
   Options.BinutilsVersion =
       llvm::TargetMachine::parseBinutilsVersion(CodeGenOpts.BinutilsVersion);
   Options.UseInitArray = CodeGenOpts.UseInitArray;
+  Options.LowerGlobalDtorsViaCxaAtExit =
+      CodeGenOpts.RegisterGlobalDtorsWithAtExit;
   Options.DisableIntegratedAS = CodeGenOpts.DisableIntegratedAS;
   Options.CompressDebugSections = CodeGenOpts.getCompressDebugSections();
   Options.RelaxELFRelocations = CodeGenOpts.RelaxELFRelocations;
 
   // Set EABI version.
   Options.EABIVersion = TargetOpts.EABIVersion;
 
   if (LangOpts.hasSjLjExceptions())

llvm/docs/Passes.rst

 This can increase the size of the code exponentially (doubling it every time a
 loop is unswitched) so we only unswitch if the resultant code will be smaller
 than a threshold.
 
 This pass expects :ref:`LICM <passes-licm>` to be run before it to hoist
 invariant conditions out of the loop, to make the unswitching opportunity
 obvious.
 
+``-lower-global-dtors``: Lower global destructors
+------------------------------------------------------------
+
+This pass lowers global module destructors (``llvm.global_dtors``) by creating
+wrapper functions that are registered as global constructors in
+``llvm.global_ctors`` and which contain a call to ``__cxa_atexit`` to register
+their destructor functions.
+
 ``-loweratomic``: Lower atomic intrinsics to non-atomic form
 ------------------------------------------------------------
 
 This pass lowers atomic intrinsics to non-atomic form for use in a known
 non-preemptible environment.
 
 The pass does not verify that the environment is non-preemptible (in general
 this would require knowledge of the entire call graph of the program including

llvm/include/llvm/CodeGen/CommandFlags.h

 unsigned getOverrideStackAlignment();
 
 bool getStackRealign();
 
 std::string getTrapFuncName();
 
 bool getUseCtors();
 
+bool getLowerGlobalDtorsViaCxaAtExit();
+
 bool getRelaxELFRelocations();
 
 bool getDataSections();
 Optional<bool> getExplicitDataSections();
 
 bool getFunctionSections();
 Optional<bool> getExplicitFunctionSections();
 

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

 
 class TargetLoweringObjectFileMachO : public TargetLoweringObjectFile {
 public:
   TargetLoweringObjectFileMachO();
   ~TargetLoweringObjectFileMachO() override = default;
 
   void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
 
+  MCSection *getStaticDtorSection(unsigned Priority,
+                                  const MCSymbol *KeySym) const override;
+
   /// Emit the module flags that specify the garbage collection information.
   void emitModuleMetadata(MCStreamer &Streamer, Module &M) const override;
 
   MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
                                     const TargetMachine &TM) const override;
 
   MCSection *getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind,
                                       const TargetMachine &TM) const override;

llvm/include/llvm/InitializePasses.h

 void initializeLoopUnswitchPass(PassRegistry&);
 void initializeLoopVectorizePass(PassRegistry&);
 void initializeLoopVersioningLICMLegacyPassPass(PassRegistry &);
 void initializeLoopVersioningLegacyPassPass(PassRegistry &);
 void initializeLowerAtomicLegacyPassPass(PassRegistry&);
 void initializeLowerConstantIntrinsicsPass(PassRegistry&);
 void initializeLowerEmuTLSPass(PassRegistry&);
 void initializeLowerExpectIntrinsicPass(PassRegistry&);
+void initializeLowerGlobalDtorsLegacyPassPass(PassRegistry &);
 void initializeLowerGuardIntrinsicLegacyPassPass(PassRegistry&);
 void initializeLowerWidenableConditionLegacyPassPass(PassRegistry&);
 void initializeLowerIntrinsicsPass(PassRegistry&);
 void initializeLowerInvokeLegacyPassPass(PassRegistry&);
 void initializeLowerSwitchLegacyPassPass(PassRegistry &);
 void initializeLowerTypeTestsPass(PassRegistry&);
 void initializeLowerMatrixIntrinsicsLegacyPassPass(PassRegistry &);
 void initializeLowerMatrixIntrinsicsMinimalLegacyPassPass(PassRegistry &);

llvm/include/llvm/LinkAllPasses.h

ForcePassLinking() {
       (void) llvm::createLoopUnrollPass();
       (void) llvm::createLoopUnrollAndJamPass();
       (void) llvm::createLoopUnswitchPass();
       (void) llvm::createLoopVersioningLICMPass();
       (void) llvm::createLoopIdiomPass();
       (void) llvm::createLoopRotatePass();
       (void) llvm::createLowerConstantIntrinsicsPass();
       (void) llvm::createLowerExpectIntrinsicPass();
+      (void) llvm::createLowerGlobalDtorsLegacyPass();
       (void) llvm::createLowerInvokePass();
       (void) llvm::createLowerSwitchPass();
       (void) llvm::createNaryReassociatePass();
       (void) llvm::createObjCARCAAWrapperPass();
       (void) llvm::createObjCARCAPElimPass();
       (void) llvm::createObjCARCExpandPass();
       (void) llvm::createObjCARCContractPass();
       (void) llvm::createObjCARCOptPass();

llvm/include/llvm/Target/TargetOptions.h

namespace llvm {
   public:
     TargetOptions()
         : UnsafeFPMath(false), NoInfsFPMath(false), NoNaNsFPMath(false),
           NoTrappingFPMath(true), NoSignedZerosFPMath(false),
           ApproxFuncFPMath(false), EnableAIXExtendedAltivecABI(false),
           HonorSignDependentRoundingFPMathOption(false), NoZerosInBSS(false),
           GuaranteedTailCallOpt(false), StackSymbolOrdering(true),
           EnableFastISel(false), EnableGlobalISel(false), UseInitArray(false),
-          DisableIntegratedAS(false), RelaxELFRelocations(false),
-          FunctionSections(false), DataSections(false),
-          IgnoreXCOFFVisibility(false), XCOFFTracebackTable(true),
-          UniqueSectionNames(true), UniqueBasicBlockSectionNames(false),
-          TrapUnreachable(false), NoTrapAfterNoreturn(false), TLSSize(0),
-          EmulatedTLS(false), ExplicitEmulatedTLS(false), EnableIPRA(false),
+          LowerGlobalDtorsViaCxaAtExit(false), DisableIntegratedAS(false),
+          RelaxELFRelocations(false), FunctionSections(false),
+          DataSections(false), IgnoreXCOFFVisibility(false),
+          XCOFFTracebackTable(true), UniqueSectionNames(true),
+          UniqueBasicBlockSectionNames(false), TrapUnreachable(false),
+          NoTrapAfterNoreturn(false), TLSSize(0), EmulatedTLS(false),
+          ExplicitEmulatedTLS(false), EnableIPRA(false),
           EmitStackSizeSection(false), EnableMachineOutliner(false),
           EnableMachineFunctionSplitter(false), SupportsDefaultOutlining(false),
           EmitAddrsig(false), EmitCallSiteInfo(false),
           SupportsDebugEntryValues(false), EnableDebugEntryValues(false),
           ValueTrackingVariableLocations(false), ForceDwarfFrameSection(false),
           XRayOmitFunctionIndex(false), DebugStrictDwarf(false),
           Hotpatch(false), PPCGenScalarMASSEntries(false), JMCInstrument(false),
           FPDenormalMode(DenormalMode::IEEE, DenormalMode::IEEE) {}
public:
     /// be set.
     SwiftAsyncFramePointerMode SwiftAsyncFramePointer =
         SwiftAsyncFramePointerMode::Always;
 
     /// UseInitArray - Use .init_array instead of .ctors for static
     /// constructors.
     unsigned UseInitArray : 1;
 
+    /// Use __cxa_atexit to register global destructors; determines how
+    /// llvm.global_dtors is lowered.
+    unsigned LowerGlobalDtorsViaCxaAtExit : 1;
+
     /// Disable the integrated assembler.
     unsigned DisableIntegratedAS : 1;
 
     /// Compress DWARF debug sections.
     DebugCompressionType CompressDebugSections = DebugCompressionType::None;
 
     unsigned RelaxELFRelocations : 1;
 

llvm/include/llvm/Transforms/Instrumentation/AddressSanitizerOptions.h

 
 namespace llvm {
 
 /// Types of ASan module destructors supported
 enum class AsanDtorKind {
   None,    ///< Do not emit any destructors for ASan
   Global,  ///< Append to llvm.global_dtors
   Invalid, ///< Not a valid destructor Kind.
-  // TODO(dliew): Add more more kinds.
 };
 
 /// Mode of ASan detect stack use after return
 enum class AsanDetectStackUseAfterReturnMode {
   Never,   ///< Never detect stack use after return.
   Runtime, ///< Detect stack use after return if runtime flag is enabled
            ///< (ASAN_OPTIONS=detect_stack_use_after_return=1)
   Always,  ///< Always detect stack use after return.
   Invalid, ///< Not a valid detect mode.
 };
 
 } // namespace llvm
 
 #endif

llvm/include/llvm/Transforms/Utils.h

 FunctionPass *createAssumeSimplifyPass();
 
 //===----------------------------------------------------------------------===//
 //
 // CanonicalizeFreezeInLoops - Canonicalize freeze instructions in loops so they
 // don't block SCEV.
 //
 Pass *createCanonicalizeFreezeInLoopsPass();
+
+//===----------------------------------------------------------------------===//
+// LowerGlobalDtorsLegacy - Lower @llvm.global_dtors by creating wrapper
+// functions that are registered in @llvm.global_ctors and which contain a call
+// to `__cxa_atexit` to register their destructor functions.
+ModulePass *createLowerGlobalDtorsLegacyPass();
 } // namespace llvm
 
 #endif

llvm/include/llvm/Transforms/Utils/LowerGlobalDtors.h

+//===- LowerGlobalDtors.h - Lower @llvm.global_dtors ----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers @llvm.global_dtors by creating wrapper functions that are
+// registered in @llvm.global_ctors and which contain a call to `__cxa_atexit`
+// to register their destructor functions.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_TRANSFORMS_UTILS_LOWERGLOBALDTORS_H
+#define LLVM_TRANSFORMS_UTILS_LOWERGLOBALDTORS_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+class LowerGlobalDtorsPass : public PassInfoMixin<LowerGlobalDtorsPass> {
+public:
+  PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
+};
+
+} // namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_LOWERGLOBALDTORS_H

llvm/lib/CodeGen/CodeGen.cpp

void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeJMCInstrumenterPass(Registry);
   initializeLiveDebugValuesPass(Registry);
   initializeLiveDebugVariablesPass(Registry);
   initializeLiveIntervalsPass(Registry);
   initializeLiveRangeShrinkPass(Registry);
   initializeLiveStacksPass(Registry);
   initializeLiveVariablesPass(Registry);
   initializeLocalStackSlotPassPass(Registry);
+  initializeLowerGlobalDtorsLegacyPassPass(Registry);
   initializeLowerIntrinsicsPass(Registry);
   initializeMIRAddFSDiscriminatorsPass(Registry);
   initializeMIRCanonicalizerPass(Registry);
   initializeMIRNamerPass(Registry);
   initializeMIRProfileLoaderPassPass(Registry);
   initializeMachineBlockFrequencyInfoPass(Registry);
   initializeMachineBlockPlacementPass(Registry);
   initializeMachineBlockPlacementStatsPass(Registry);

llvm/lib/CodeGen/CommandFlags.cpp

 CGOPT(SwiftAsyncFramePointerMode, SwiftAsyncFramePointer)
 CGOPT(bool, DontPlaceZerosInBSS)
 CGOPT(bool, EnableGuaranteedTailCallOpt)
 CGOPT(bool, DisableTailCalls)
 CGOPT(bool, StackSymbolOrdering)
 CGOPT(bool, StackRealign)
 CGOPT(std::string, TrapFuncName)
 CGOPT(bool, UseCtors)
+CGOPT(bool, LowerGlobalDtorsViaCxaAtExit)
 CGOPT(bool, RelaxELFRelocations)
 CGOPT_EXP(bool, DataSections)
 CGOPT_EXP(bool, FunctionSections)
 CGOPT(bool, IgnoreXCOFFVisibility)
 CGOPT(bool, XCOFFTracebackTable)
 CGOPT(std::string, BBSections)
 CGOPT(unsigned, TLSSize)
 CGOPT(bool, EmulatedTLS)
static cl::opt<std::string> TrapFuncName(
       cl::init(""));
   CGBINDOPT(TrapFuncName);
 
   static cl::opt<bool> UseCtors("use-ctors",
                                 cl::desc("Use .ctors instead of .init_array."),
                                 cl::init(false));
   CGBINDOPT(UseCtors);
 
+  static cl::opt<bool> LowerGlobalDtorsViaCxaAtExit(
+      "lower-global-dtors-via-cxa-atexit",
+      cl::desc("Lower llvm.global_dtors (global destructors) via __cxa_atexit"),
+      cl::init(true));
+  CGBINDOPT(LowerGlobalDtorsViaCxaAtExit);
+
   static cl::opt<bool> RelaxELFRelocations(
       "relax-elf-relocations",
       cl::desc(
           "Emit GOTPCRELX/REX_GOTPCRELX instead of GOTPCREL on x86-64 ELF"),
       cl::init(false));
   CGBINDOPT(RelaxELFRelocations);
 
   static cl::opt<bool> DataSections(
Options.HonorSignDependentRoundingFPMathOption =
       getEnableHonorSignDependentRoundingFPMath();
   if (getFloatABIForCalls() != FloatABI::Default)
     Options.FloatABIType = getFloatABIForCalls();
   Options.EnableAIXExtendedAltivecABI = getEnableAIXExtendedAltivecABI();
   Options.NoZerosInBSS = getDontPlaceZerosInBSS();
   Options.GuaranteedTailCallOpt = getEnableGuaranteedTailCallOpt();
   Options.StackSymbolOrdering = getStackSymbolOrdering();
   Options.UseInitArray = !getUseCtors();
+  Options.LowerGlobalDtorsViaCxaAtExit = getLowerGlobalDtorsViaCxaAtExit();
   Options.RelaxELFRelocations = getRelaxELFRelocations();
   Options.DataSections =
       getExplicitDataSections().getValueOr(TheTriple.hasDefaultDataSections());
   Options.FunctionSections = getFunctionSections();
   Options.IgnoreXCOFFVisibility = getIgnoreXCOFFVisibility();
   Options.XCOFFTracebackTable = getXCOFFTracebackTable();
   Options.BBSections = getBBSectionsMode(Options);
   Options.UniqueSectionNames = getUniqueSectionNames();

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
 
   PersonalityEncoding =
       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
   LSDAEncoding = dwarf::DW_EH_PE_pcrel;
   TTypeEncoding =
       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 }
 
+MCSection *TargetLoweringObjectFileMachO::getStaticDtorSection(
+    unsigned Priority, const MCSymbol *KeySym) const {
+  // TODO(yln): Remove -lower-global-dtors-via-cxa-atexit fallback flag
+  // (LowerGlobalDtorsViaCxaAtExit) and always issue a fatal error here.
+  if (TM->Options.LowerGlobalDtorsViaCxaAtExit)
+    report_fatal_error("@llvm.global_dtors should have been lowered already");
+  return StaticDtorSection;
+}
+
 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
                                                        Module &M) const {
   // Emit the linker options if present.
   if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
     for (const auto *Option : LinkerOptions->operands()) {
       SmallVector<std::string, 4> StrOptions;
       for (const auto &Piece : cast<MDNode>(Option)->operands())
         StrOptions.push_back(std::string(cast<MDString>(Piece)->getString()));
MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
   return Priority == UINT16_MAX ?
          StaticCtorSection :
          getContext().getWasmSection(".init_array." + utostr(Priority),
                                      SectionKind::getData());
 }
 
 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
     unsigned Priority, const MCSymbol *KeySym) const {
-  llvm_unreachable("@llvm.global_dtors should have been lowered already");
-  return nullptr;
+  report_fatal_error("@llvm.global_dtors should have been lowered already");
 }
 
 //===----------------------------------------------------------------------===//
 //                                  XCOFF
 //===----------------------------------------------------------------------===//
 bool TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(
     const MachineFunction *MF) {
   if (!MF->getLandingPads().empty())

llvm/lib/CodeGen/TargetPassConfig.cpp

void TargetPassConfig::addIRPasses() {
   }
 
   // Run GC lowering passes for builtin collectors
   // TODO: add a pass insertion point here
   addPass(&GCLoweringID);
   addPass(&ShadowStackGCLoweringID);
   addPass(createLowerConstantIntrinsicsPass());
 
+  // For MachO, lower @llvm.global_dtors into @llvm_global_ctors with
+  // __cxa_atexit() calls to avoid emitting the deprecated __mod_term_func.
+  if (TM->getTargetTriple().isOSBinFormatMachO() &&
+      TM->Options.LowerGlobalDtorsViaCxaAtExit)
+    addPass(createLowerGlobalDtorsLegacyPass());
+
   // Make sure that no unreachable blocks are instruction selected.
   addPass(createUnreachableBlockEliminationPass());
 
   // Prepare expensive constants for SelectionDAG.
   if (getOptLevel() != CodeGenOpt::None && !DisableConstantHoisting)
     addPass(createConstantHoistingPass());
 
   if (getOptLevel() != CodeGenOpt::None)

llvm/lib/Passes/PassBuilder.cpp

 #include "llvm/Transforms/Utils/FixIrreducible.h"
 #include "llvm/Transforms/Utils/HelloWorld.h"
 #include "llvm/Transforms/Utils/InjectTLIMappings.h"
 #include "llvm/Transforms/Utils/InstructionNamer.h"
 #include "llvm/Transforms/Utils/LCSSA.h"
 #include "llvm/Transforms/Utils/LibCallsShrinkWrap.h"
 #include "llvm/Transforms/Utils/LoopSimplify.h"
 #include "llvm/Transforms/Utils/LoopVersioning.h"
+#include "llvm/Transforms/Utils/LowerGlobalDtors.h"
 #include "llvm/Transforms/Utils/LowerInvoke.h"
 #include "llvm/Transforms/Utils/LowerSwitch.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
 #include "llvm/Transforms/Utils/MetaRenamer.h"
 #include "llvm/Transforms/Utils/NameAnonGlobals.h"
 #include "llvm/Transforms/Utils/PredicateInfo.h"
 #include "llvm/Transforms/Utils/RelLookupTableConverter.h"
 #include "llvm/Transforms/Utils/StripGCRelocates.h"

llvm/lib/Passes/PassRegistry.def

 MODULE_PASS("insert-gcov-profiling", GCOVProfilerPass())
 MODULE_PASS("instrorderfile", InstrOrderFilePass())
 MODULE_PASS("instrprof", InstrProfiling())
 MODULE_PASS("internalize", InternalizePass())
 MODULE_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 MODULE_PASS("ipsccp", IPSCCPPass())
 MODULE_PASS("iroutliner", IROutlinerPass())
 MODULE_PASS("print-ir-similarity", IRSimilarityAnalysisPrinterPass(dbgs()))
+MODULE_PASS("lower-global-dtors", LowerGlobalDtorsPass())
 MODULE_PASS("lowertypetests", LowerTypeTestsPass())
 MODULE_PASS("metarenamer", MetaRenamerPass())
 MODULE_PASS("mergefunc", MergeFunctionsPass())
 MODULE_PASS("name-anon-globals", NameAnonGlobalPass())
 MODULE_PASS("no-op-module", NoOpModulePass())
 MODULE_PASS("objc-arc-apelim", ObjCARCAPElimPass())
 MODULE_PASS("partial-inliner", PartialInlinerPass())
 MODULE_PASS("pgo-icall-prom", PGOIndirectCallPromotion())

llvm/lib/Target/WebAssembly/CMakeLists.txt

add_llvm_target(WebAssemblyCodeGen
   WebAssemblyFixIrreducibleControlFlow.cpp
   WebAssemblyFixFunctionBitcasts.cpp
   WebAssemblyFrameLowering.cpp
   WebAssemblyISelDAGToDAG.cpp
   WebAssemblyISelLowering.cpp
   WebAssemblyInstrInfo.cpp
   WebAssemblyLowerBrUnless.cpp
   WebAssemblyLowerEmscriptenEHSjLj.cpp
-  WebAssemblyLowerGlobalDtors.cpp
   WebAssemblyLowerRefTypesIntPtrConv.cpp
   WebAssemblyMachineFunctionInfo.cpp
   WebAssemblyMCInstLower.cpp
   WebAssemblyMCLowerPrePass.cpp
   WebAssemblyNullifyDebugValueLists.cpp
   WebAssemblyOptimizeLiveIntervals.cpp
   WebAssemblyOptimizeReturned.cpp
   WebAssemblyPeephole.cpp

llvm/lib/Target/WebAssembly/WebAssembly.h

 namespace llvm {
 
 class WebAssemblyTargetMachine;
 class ModulePass;
 class FunctionPass;
 
 // LLVM IR passes.
 ModulePass *createWebAssemblyLowerEmscriptenEHSjLj();
-ModulePass *createWebAssemblyLowerGlobalDtors();
 ModulePass *createWebAssemblyAddMissingPrototypes();
 ModulePass *createWebAssemblyFixFunctionBitcasts();
 FunctionPass *createWebAssemblyOptimizeReturned();
 FunctionPass *createWebAssemblyLowerRefTypesIntPtrConv();
 
 // ISel and immediate followup passes.
 FunctionPass *createWebAssemblyISelDag(WebAssemblyTargetMachine &TM,
                                        CodeGenOpt::Level OptLevel);

 FunctionPass *createWebAssemblyRegNumbering();
 FunctionPass *createWebAssemblyDebugFixup();
 FunctionPass *createWebAssemblyPeephole();
 ModulePass *createWebAssemblyMCLowerPrePass();
 
 // PassRegistry initialization declarations.
 void initializeWebAssemblyAddMissingPrototypesPass(PassRegistry &);
 void initializeWebAssemblyLowerEmscriptenEHSjLjPass(PassRegistry &);
-void initializeLowerGlobalDtorsPass(PassRegistry &);
 void initializeFixFunctionBitcastsPass(PassRegistry &);
 void initializeOptimizeReturnedPass(PassRegistry &);
 void initializeWebAssemblyArgumentMovePass(PassRegistry &);
 void initializeWebAssemblySetP2AlignOperandsPass(PassRegistry &);
 void initializeWebAssemblyReplacePhysRegsPass(PassRegistry &);
 void initializeWebAssemblyNullifyDebugValueListsPass(PassRegistry &);
 void initializeWebAssemblyPrepareForLiveIntervalsPass(PassRegistry &);
 void initializeWebAssemblyOptimizeLiveIntervalsPass(PassRegistry &);

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

 #include "WebAssemblyTargetObjectFile.h"
 #include "WebAssemblyTargetTransformInfo.h"
 #include "llvm/CodeGen/MIRParser/MIParser.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/RegAllocRegistry.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/IR/Function.h"
+#include "llvm/InitializePasses.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Scalar/LowerAtomic.h"
 #include "llvm/Transforms/Utils.h"
 using namespace llvm;
 
RegisterTargetMachine<WebAssemblyTargetMachine> X(
       getTheWebAssemblyTarget32());
   RegisterTargetMachine<WebAssemblyTargetMachine> Y(
       getTheWebAssemblyTarget64());
 
   // Register backend passes
   auto &PR = *PassRegistry::getPassRegistry();
   initializeWebAssemblyAddMissingPrototypesPass(PR);
   initializeWebAssemblyLowerEmscriptenEHSjLjPass(PR);
-  initializeLowerGlobalDtorsPass(PR);
+  initializeLowerGlobalDtorsLegacyPassPass(PR);
   initializeFixFunctionBitcastsPass(PR);
   initializeOptimizeReturnedPass(PR);
   initializeWebAssemblyArgumentMovePass(PR);
   initializeWebAssemblySetP2AlignOperandsPass(PR);
   initializeWebAssemblyReplacePhysRegsPass(PR);
   initializeWebAssemblyPrepareForLiveIntervalsPass(PR);
   initializeWebAssemblyOptimizeLiveIntervalsPass(PR);
   initializeWebAssemblyMemIntrinsicResultsPass(PR);

 // the CodeGen pass sequence.
 //===----------------------------------------------------------------------===//
 
 void WebAssemblyPassConfig::addIRPasses() {
   // Add signatures to prototype-less function declarations
   addPass(createWebAssemblyAddMissingPrototypes());
 
   // Lower .llvm.global_dtors into .llvm_global_ctors with __cxa_atexit calls.
-  addPass(createWebAssemblyLowerGlobalDtors());
+  addPass(createLowerGlobalDtorsLegacyPass());
 
   // Fix function bitcasts, as WebAssembly requires caller and callee signatures
   // to match.
   addPass(createWebAssemblyFixFunctionBitcasts());
 
   // Optimize "returned" function attributes.
   if (getOptLevel() != CodeGenOpt::None)
     addPass(createWebAssemblyOptimizeReturned());

llvm/lib/Transforms/Utils/CMakeLists.txt

add_llvm_component_library(LLVMTransformUtils
   LoopPeel.cpp
   LoopRotationUtils.cpp
   LoopSimplify.cpp
   LoopUnroll.cpp
   LoopUnrollAndJam.cpp
   LoopUnrollRuntime.cpp
   LoopUtils.cpp
   LoopVersioning.cpp
+  LowerGlobalDtors.cpp
   LowerInvoke.cpp
   LowerMemIntrinsics.cpp
   LowerSwitch.cpp
   MatrixUtils.cpp
   MemoryOpRemark.cpp
   MemoryTaggingSupport.cpp
   Mem2Reg.cpp
   MetaRenamer.cpp

llvm/lib/Transforms/Utils/LowerGlobalDtors.cpp

-//===-- WebAssemblyLowerGlobalDtors.cpp - Lower @llvm.global_dtors --------===//
+//===-- LowerGlobalDtors.cpp - Lower @llvm.global_dtors -------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// Lower @llvm.global_dtors.
 ///
-/// WebAssembly doesn't have a builtin way to invoke static destructors.
 /// Implement @llvm.global_dtors by creating wrapper functions that are
 /// registered in @llvm.global_ctors and which contain a call to
 /// `__cxa_atexit` to register their destructor functions.
 ///
 //===----------------------------------------------------------------------===//
 
-#include "WebAssembly.h"
-#include "llvm/ADT/MapVector.h"
+#include "llvm/Transforms/Utils/LowerGlobalDtors.h"
+
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/Module.h"
+#include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 #include <map>
 
 using namespace llvm;
 
-#define DEBUG_TYPE "wasm-lower-global-dtors"
+#define DEBUG_TYPE "lower-global-dtors"
 
 namespace {
-class LowerGlobalDtors final : public ModulePass {
+class LowerGlobalDtorsLegacyPass final : public ModulePass {
   StringRef getPassName() const override {
-    return "WebAssembly Lower @llvm.global_dtors";
+    return "Lower @llvm.global_dtors via `__cxa_atexit`";
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesCFG();
     ModulePass::getAnalysisUsage(AU);
   }
 
   bool runOnModule(Module &M) override;
 
 public:
   static char ID;
-  LowerGlobalDtors() : ModulePass(ID) {}
+  LowerGlobalDtorsLegacyPass() : ModulePass(ID) {
+    initializeLowerGlobalDtorsLegacyPassPass(*PassRegistry::getPassRegistry());
+  }
 };
 } // End anonymous namespace
 
-char LowerGlobalDtors::ID = 0;
-INITIALIZE_PASS(LowerGlobalDtors, DEBUG_TYPE,
-                "Lower @llvm.global_dtors for WebAssembly", false, false)
+char LowerGlobalDtorsLegacyPass::ID = 0;
+INITIALIZE_PASS(LowerGlobalDtorsLegacyPass, DEBUG_TYPE,
+                "Lower @llvm.global_dtors via `__cxa_atexit`", false, false)
 
-ModulePass *llvm::createWebAssemblyLowerGlobalDtors() {
-  return new LowerGlobalDtors();
+ModulePass *llvm::createLowerGlobalDtorsLegacyPass() {
+  return new LowerGlobalDtorsLegacyPass();
 }
 
-bool LowerGlobalDtors::runOnModule(Module &M) {
-  LLVM_DEBUG(dbgs() << "********** Lower Global Destructors **********\n");
+static bool runImpl(Module &M);
+bool LowerGlobalDtorsLegacyPass::runOnModule(Module &M) { return runImpl(M); }
+
+PreservedAnalyses LowerGlobalDtorsPass::run(Module &M,
+                                            ModuleAnalysisManager &AM) {
+  bool Changed = runImpl(M);
+  if (!Changed)
+    return PreservedAnalyses::all();
+
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
+}
 
+static bool runImpl(Module &M) {
   GlobalVariable *GV = M.getGlobalVariable("llvm.global_dtors");
   if (!GV || !GV->hasInitializer())
     return false;
 
   const ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
   if (!InitList)
     return false;
 

llvm/lib/Transforms/Utils/Utils.cpp

void llvm::initializeTransformUtils(PassRegistry &Registry) {
   initializeAssumeBuilderPassLegacyPassPass(Registry);
   initializeBreakCriticalEdgesPass(Registry);
   initializeCanonicalizeAliasesLegacyPassPass(Registry);
   initializeCanonicalizeFreezeInLoopsPass(Registry);
   initializeInstNamerPass(Registry);
   initializeLCSSAWrapperPassPass(Registry);
   initializeLibCallsShrinkWrapLegacyPassPass(Registry);
   initializeLoopSimplifyPass(Registry);
+  initializeLowerGlobalDtorsLegacyPassPass(Registry);
   initializeLowerInvokeLegacyPassPass(Registry);
   initializeLowerSwitchLegacyPassPass(Registry);
   initializeNameAnonGlobalLegacyPassPass(Registry);
   initializePromoteLegacyPassPass(Registry);
   initializeStripNonLineTableDebugLegacyPassPass(Registry);
   initializeUnifyFunctionExitNodesLegacyPassPass(Registry);
   initializeMetaRenamerPass(Registry);
   initializeStripGCRelocatesLegacyPass(Registry);

llvm/test/CodeGen/ARM/ctors_dtors.ll

 ; RUN: llc < %s -mtriple=arm-apple-darwin  | FileCheck %s -check-prefix=DARWIN
+; RUN: llc < %s -mtriple=arm-apple-darwin -lower-global-dtors-via-cxa-atexit=false  | FileCheck %s -check-prefix=DARWIN-OLD
 ; RUN: llc < %s -mtriple=arm-linux-gnu -target-abi=apcs  | FileCheck %s -check-prefix=ELF
 ; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s -check-prefix=GNUEABI
 
+; DARWIN: l_register_call_dtors:
+; DARWIN: bl  ___cxa_atexit
 ; DARWIN: .section  __DATA,__mod_init_func,mod_init_funcs
-; DARWIN: .section  __DATA,__mod_term_func,mod_term_funcs
+; DARWIN-NOT: __mod_term_func
+
+; DARWIN-OLD: .section  __DATA,__mod_init_func,mod_init_funcs
+; DARWIN-OLD: .section  __DATA,__mod_term_func,mod_term_funcs
 
 ; ELF: .section .ctors,"aw",%progbits
 ; ELF: .section .dtors,"aw",%progbits
 
 ; GNUEABI: .section .init_array,"aw",%init_array
 ; GNUEABI: .section .fini_array,"aw",%fini_array
 
 @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [ { i32, void ()*, i8* } { i32 65535, void ()* @__mf_init, i8* null } ]                ; <[1 x { i32, void ()*, i8* }]*> [#uses=0]

llvm/test/CodeGen/X86/2011-08-29-InitOrder.ll

 ; RUN: llc < %s -mtriple=i386-linux-gnu -use-ctors | FileCheck %s --check-prefix=CHECK-DEFAULT
 ; RUN: llc < %s -mtriple=i386-apple-darwin | FileCheck %s --check-prefix=CHECK-DARWIN
 ; PR5329
 
 @llvm.global_ctors = appending global [3 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 2000, void ()* @construct_2, i8* null }, { i32, void ()*, i8* } { i32 3000, void ()* @construct_3, i8* null }, { i32, void ()*, i8* } { i32 1000, void ()* @construct_1, i8* null }]
 ; CHECK-DEFAULT: .section        .ctors.62535,"aw",@progbits
 ; CHECK-DEFAULT: .long construct_3
 ; CHECK-DEFAULT: .section        .ctors.63535,"aw",@progbits
 ; CHECK-DEFAULT: .long construct_2
 ; CHECK-DEFAULT: .section        .ctors.64535,"aw",@progbits
 ; CHECK-DEFAULT: .long construct_1
 
-; CHECK-DARWIN: .long _construct_1
+; CHECK-DARWIN-LABEL: .section  __DATA,__mod_init_func,mod_init_funcs
+; CHECK-DARWIN:      .long _construct_1
+; CHECK-DARWIN-NEXT: .long l_register_call_dtors.1000
 ; CHECK-DARWIN-NEXT: .long _construct_2
+; CHECK-DARWIN-NEXT: .long l_register_call_dtors.2000
 ; CHECK-DARWIN-NEXT: .long _construct_3
+; CHECK-DARWIN-NEXT: .long l_register_call_dtors.3000
 
 @llvm.global_dtors = appending global [3 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 2000, void ()* @destruct_2, i8* null }, { i32, void ()*, i8* } { i32 1000, void ()* @destruct_1, i8* null }, { i32, void ()*, i8* } { i32 3000, void ()* @destruct_3, i8* null }]
 ; CHECK-DEFAULT: .section        .dtors.62535,"aw",@progbits
 ; CHECK-DEFAULT: .long destruct_3
 ; CHECK-DEFAULT: .section        .dtors.63535,"aw",@progbits
 ; CHECK-DEFAULT: .long destruct_2
 ; CHECK-DEFAULT: .section        .dtors.64535,"aw",@progbits
 ; CHECK-DEFAULT: .long destruct_1
 
-; CHECK-DARWIN:      .long _destruct_1
-; CHECK-DARWIN-NEXT: .long _destruct_2
-; CHECK-DARWIN-NEXT: .long _destruct_3
+; CHECK-DARWIN-NOT: mod_term_func
 
 declare void @construct_1()
 declare void @construct_2()
 declare void @construct_3()
 declare void @destruct_1()
 declare void @destruct_2()
 declare void @destruct_3()

llvm/test/Transforms/LowerGlobalDestructors/lower-global-dtors.ll

+; RUN: opt        -lower-global-dtors -S < %s | FileCheck %s --implicit-check-not=llvm.global_dtors
+; RUN: opt -passes=lower-global-dtors -S < %s | FileCheck %s --implicit-check-not=llvm.global_dtors
+
+; Test that @llvm.global_dtors is properly lowered into @llvm.global_ctors,
+; grouping dtor calls by priority and associated symbol.
+
+declare void @orig_ctor()
+declare void @orig_dtor0()
+declare void @orig_dtor1a()
+declare void @orig_dtor1b()
+declare void @orig_dtor1c0()
+declare void @orig_dtor1c1a()
+declare void @orig_dtor1c1b()
+declare void @orig_dtor1c2a()
+declare void @orig_dtor1c2b()
+declare void @orig_dtor1c3()
+declare void @orig_dtor1d()
+declare void @orig_dtor65535()
+declare void @orig_dtor65535c0()
+declare void @after_the_null()
+
+@associatedc0 = external global i8
+@associatedc1 = external global i8
+@associatedc2 = global i8 42
+@associatedc3 = global i8 84
+
[e-mail]_ctors = appending global
+[1 x { i32, void ()*, i8* }]
+[
+  { i32, void ()*, i8* } { i32 200, void ()* @orig_ctor, i8* null }
+]
+
[e-mail]_dtors = appending global
+[14 x { i32, void ()*, i8* }]
+[
+  { i32, void ()*, i8* } { i32 0, void ()* @orig_dtor0, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1a, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1b, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c0, i8* @associatedc0 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c1a, i8* @associatedc1 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c1b, i8* @associatedc1 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c2a, i8* @associatedc2 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c2b, i8* @associatedc2 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c3, i8* @associatedc3 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1d, i8* null },
+  { i32, void ()*, i8* } { i32 65535, void ()* @orig_dtor65535c0, i8* @associatedc0 },
+  { i32, void ()*, i8* } { i32 65535, void ()* @orig_dtor65535, i8* null },
+  { i32, void ()*, i8* } { i32 65535, void ()* null, i8* null },
+  { i32, void ()*, i8* } { i32 65535, void ()* @after_the_null, i8* null }
+]
+
+; CHECK: @associatedc0 = external global i8
+; CHECK: @associatedc1 = external global i8
+; CHECK: @associatedc2 = global i8 42
+; CHECK: @associatedc3 = global i8 84
+; CHECK: @__dso_handle = extern_weak hidden constant i8
+
+; CHECK-LABEL: @llvm.global_ctors = appending global [10 x { i32, void ()*, i8* }] [
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 200, void ()* @orig_ctor, i8* null },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 0, void ()* @register_call_dtors.0, i8* null },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$0", i8* null },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$1.associatedc0", i8* @associatedc0 },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$2.associatedc1", i8* @associatedc1 },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$3.associatedc2", i8* @associatedc2 },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$4.associatedc3", i8* @associatedc3 },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 1, void ()* @"register_call_dtors.1$5", i8* null },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 65535, void ()* @"register_call_dtors$0.associatedc0", i8* @associatedc0 },
+; CHECK-SAME:  { i32, void ()*, i8* } { i32 65535, void ()* @"register_call_dtors$1", i8* null }]
+
+; CHECK: declare void @orig_ctor()
+; CHECK: declare void @orig_dtor0()
+; --- other dtors here ---
+; CHECK: declare void @after_the_null()
+
+; CHECK: declare i32 @__cxa_atexit(void (i8*)*, i8*, i8*)
+
+; CHECK-LABEL: define private void @call_dtors.0(i8* %0)
+; CHECK:       call void @orig_dtor0()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @register_call_dtors.0()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @call_dtors.0, i8* null, i8* @__dso_handle)
+; CHECK-NEXT:  %0 = icmp ne i32 %call, 0
+; CHECK-NEXT:  br i1 %0, label %fail, label %return
+; CHECK-EMPTY:
+; CHECK-NEXT:  fail:
+; CHECK-NEXT:    call void @llvm.trap()
+; CHECK-NEXT:    unreachable
+; CHECK-EMPTY:
+; CHECK-NEXT:  return:
+; CHECK-NEXT:    ret void
+
+; CHECK-LABEL: define private void @"call_dtors.1$0"(i8* %0)
+; CHECK:       call void @orig_dtor1b()
+; CHECK-NEXT:  call void @orig_dtor1a()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$0"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$0", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors.1$1.associatedc0"(i8* %0)
+; CHECK:       call void @orig_dtor1c0()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$1.associatedc0"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$1.associatedc0", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors.1$2.associatedc1"(i8* %0)
+; CHECK:       call void @orig_dtor1c1b()
+; CHECK-NEXT:  call void @orig_dtor1c1a()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$2.associatedc1"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$2.associatedc1", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors.1$3.associatedc2"(i8* %0)
+; CHECK:       call void @orig_dtor1c2b()
+; CHECK-NEXT:  call void @orig_dtor1c2a()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$3.associatedc2"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$3.associatedc2", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors.1$4.associatedc3"(i8* %0)
+; CHECK:       call void @orig_dtor1c3()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$4.associatedc3"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$4.associatedc3", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors.1$5"(i8* %0)
+; CHECK:       call void @orig_dtor1d()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors.1$5"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors.1$5", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors$0.associatedc0"(i8* %0)
+; CHECK:       call void @orig_dtor65535c0()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors$0.associatedc0"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors$0.associatedc0", i8* null, i8* @__dso_handle)
+
+; CHECK-LABEL: define private void @"call_dtors$1"(i8* %0)
+; CHECK:       call void @orig_dtor65535()
+; CHECK-NEXT:  ret void
+
+; CHECK-LABEL: define private void @"register_call_dtors$1"()
+; CHECK:       %call = call i32 @__cxa_atexit(void (i8*)* @"call_dtors$1", i8* null, i8* @__dso_handle)
+
+
+; This function is listed after the null terminator, so it should
+; be excluded.
+
+; CHECK-NOT: after_the_null