[LTO][GlobalDCE] Use pass parameter instead of module flag for LTO phase

[tejohnson]

Summary

D63932 added a module flag to indicate that we are executing the regular
LTO post merge pipeline, so that GlobalDCE could perform more aggressive
optimization for Dead Virtual Function Elimination. This caused issues
trying to reuse bitcode that had already been through the LTO pipeline
(see context in D139816).

Instead support this by passing down a parameter flag to the
GlobalDCEPass constructor, which is the more usual way for indicating
this information.

Most test changes are to remove incidental uses of this flag. Of the 2
real uses, llvm/test/LTO/ARM/lto-linking-metadata.ll is now obsolete and
removed in this patch, and the virtual-functions-visibility-post-lto.ll
test is updated to use the regular LTO default pipeline where this
parameter is set to true.

[nikic]

You need to also implement printing and parsing support for the new pass option.

[aeubanks]

In D153655#4444985, @nikic wrote:

You need to also implement printing and parsing support for the new pass option.

(https://reviews.llvm.org/D153437 as an example)

[tejohnson]

In D153655#4445020, @aeubanks wrote:

In D153655#4444985, @nikic wrote:

You need to also implement printing and parsing support for the new pass option.

(https://reviews.llvm.org/D153437 as an example)

Ah missed that. Done.

I also updated new-pm-print-pipeline.ll to test the new parameter.

Expanded virtual-functions-visibility-post-lto.ll test to use globaldce with the new parameter in addition to testing by invoking the full regular LTO pass pipeline. I also expanded this to ensure the transformation doesn't occur if we don't specify the new parameter (or use a non-lto default pipeline).

[tejohnson]

Address comments

[aeubanks]

lgtm with one comment, this is much cleaner

llvm/lib/Passes/PassBuilder.cpp

676

GlobalDCE

[arsenm]

llvm/lib/Passes/PassBuilder.cpp

676

Can you use a name descriptive of the behavior change, rather than the why/where?

[tejohnson]

llvm/lib/Passes/PassBuilder.cpp

676

Looks like it is supposed to be the pass name, fixed.

[tejohnson]

Address comments

[arsenm]

llvm/lib/Passes/PassBuilder.cpp

676

I mean "in-lto-post-link" doesn't tell me how the pass is going to behave differently. I mean something like handle-vtable-something or skip-something

[tejohnson]

llvm/lib/Passes/PassBuilder.cpp

676

Oh hmm, I was thought this should be the same as the parameter name, which I was trying to keep close to the previous module flag.

I'm not sure what to rename this to that is descriptive yet not too long. The behavior is basically: when in the LTO post link, VFE can be applied to vtables with linkage unit vcall visibility (by default it is just those with translation unit vcall visibility). Open to suggestions.

[arsenm]

llvm/lib/Passes/PassBuilder.cpp

676

After skimming the code and barely knowing anything about this optimization, my suggestions:

'assume-visible-vcall-table'
'assume-vcall-visibility-translation-unit'
'assume-module-visibility'
'whole-module-vfe'

[tejohnson]

llvm/lib/Passes/PassBuilder.cpp

676

Ok thanks. After considering these and thinking about it some more, I've settled on 'vfe-linkage-unit-visibility' (since we are telling VFE that it can assume it has visibility over the full linkage unit).

[tejohnson]

Change pass option string name

[tejohnson]

Fix one place I forgot to update with the new name

llvm/include/llvm/Transforms/IPO/GlobalDCE.h

 class GlobalVariable;
 class Metadata;
 class Module;
 class Value;
 
 /// Pass to remove unused function declarations.
 class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
 public:
+  GlobalDCEPass(bool InLTOPostLink = false) : InLTOPostLink(InLTOPostLink) {}
+
   PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
 
+  void printPipeline(raw_ostream &OS,
+                     function_ref<StringRef(StringRef)> MapClassName2PassName);
+
 private:
+  bool InLTOPostLink = false;
+
   SmallPtrSet<GlobalValue*, 32> AliveGlobals;
 
   /// Global -> Global that uses this global.
   DenseMap<GlobalValue *, SmallPtrSet<GlobalValue *, 4>> GVDependencies;
 
   /// Constant -> Globals that use this global cache.
   std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>>
       ConstantDependenciesCache;

llvm/lib/LTO/LTO.cpp

for (const auto &R : GlobalResolutions) {
       if (!GV || GV->hasLocalLinkage() || GV->isDeclaration())
         continue;
       GV->setUnnamedAddr(R.second.UnnamedAddr ? GlobalValue::UnnamedAddr::Global
                                               : GlobalValue::UnnamedAddr::None);
       if (EnableLTOInternalization && R.second.Partition == 0)
         GV->setLinkage(GlobalValue::InternalLinkage);
     }
 
-    RegularLTO.CombinedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
-
     if (Conf.PostInternalizeModuleHook &&
         !Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
       return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
   }
 
   if (!RegularLTO.EmptyCombinedModule || Conf.AlwaysEmitRegularLTOObj) {
     if (Error Err =
             backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,

llvm/lib/LTO/LTOCodeGenerator.cpp

bool LTOCodeGenerator::optimize() {
 
   // We always run the verifier once on the merged module, the `DisableVerify`
   // parameter only applies to subsequent verify.
   verifyMergedModuleOnce();
 
   // Mark which symbols can not be internalized
   this->applyScopeRestrictions();
 
-  // Write LTOPostLink flag for passes that require all the modules.
-  MergedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
-
   // Add an appropriate DataLayout instance for this module...
   MergedModule->setDataLayout(TargetMach->createDataLayout());
 
   if (!SaveIRBeforeOptPath.empty()) {
     std::error_code EC;
     raw_fd_ostream OS(SaveIRBeforeOptPath, EC, sys::fs::OF_None);
     if (EC)
       report_fatal_error(Twine("Failed to open ") + SaveIRBeforeOptPath +

llvm/lib/Passes/PassBuilder.cpp

if (ParamName == OptionName) {
           formatv("invalid {1} pass parameter '{0}' ", ParamName, PassName)
               .str(),
           inconvertibleErrorCode());
     }
   }
   return Result;
 }
 
+Expected<bool> parseGlobalDCEPassOptions(StringRef Params) {
+  return parseSinglePassOption(Params, "vfe-linkage-unit-visibility", "GlobalDCE");
+}
+
 Expected<bool> parseInlinerPassOptions(StringRef Params) {
   return parseSinglePassOption(Params, "only-mandatory", "InlinerPass");
 }
 
 Expected<bool> parseCoroSplitPassOptions(StringRef Params) {
   return parseSinglePassOption(Params, "reuse-storage", "CoroSplitPass");
 }
 

llvm/lib/Passes/PassBuilderPipelines.cpp

if (PGOOpt && PGOOpt->Action == PGOOptions::SampleUse) {
     MPM.addPass(RequireAnalysisPass<ProfileSummaryAnalysis, Module>());
   }
 
   // Try to run OpenMP optimizations, quick no-op if no OpenMP metadata present.
   MPM.addPass(OpenMPOptPass(ThinOrFullLTOPhase::FullLTOPostLink));
 
   // Remove unused virtual tables to improve the quality of code generated by
   // whole-program devirtualization and bitset lowering.
-  MPM.addPass(GlobalDCEPass());
+  MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
 
   // Do basic inference of function attributes from known properties of system
   // libraries and other oracles.
   MPM.addPass(InferFunctionAttrsPass());
 
   if (Level.getSpeedupLevel() > 1) {
     MPM.addPass(createModuleToFunctionPassAdaptor(
         CallSiteSplittingPass(), PTO.EagerlyInvalidateAnalyses));
PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
 
   // Optimize globals again after we ran the inliner.
   MPM.addPass(GlobalOptPass());
 
   // Run the OpenMPOpt pass again after global optimizations.
   MPM.addPass(OpenMPOptPass(ThinOrFullLTOPhase::FullLTOPostLink));
 
   // Garbage collect dead functions.
-  MPM.addPass(GlobalDCEPass());
+  MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
 
   // If we didn't decide to inline a function, check to see if we can
   // transform it to pass arguments by value instead of by reference.
   MPM.addPass(createModuleToPostOrderCGSCCPassAdaptor(ArgumentPromotionPass()));
 
   FunctionPassManager FPM;
   // The IPO Passes may leave cruft around. Clean up after them.
   FPM.addPass(InstCombinePass());
LateFPM.addPass(SimplifyCFGPass(
       SimplifyCFGOptions().convertSwitchRangeToICmp(true).hoistCommonInsts(
           true)));
   MPM.addPass(createModuleToFunctionPassAdaptor(std::move(LateFPM)));
 
   // Drop bodies of available eternally objects to improve GlobalDCE.
   MPM.addPass(EliminateAvailableExternallyPass());
 
   // Now that we have optimized the program, discard unreachable functions.
-  MPM.addPass(GlobalDCEPass());
+  MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
 
   if (PTO.MergeFunctions)
     MPM.addPass(MergeFunctionsPass());
 
   if (PTO.CallGraphProfile)
     MPM.addPass(CGProfilePass());
 
   invokeFullLinkTimeOptimizationLastEPCallbacks(MPM, Level);

llvm/lib/Passes/PassRegistry.def

 MODULE_PASS("cross-dso-cfi", CrossDSOCFIPass())
 MODULE_PASS("deadargelim", DeadArgumentEliminationPass())
 MODULE_PASS("debugify", NewPMDebugifyPass())
 MODULE_PASS("dot-callgraph", CallGraphDOTPrinterPass())
 MODULE_PASS("elim-avail-extern", EliminateAvailableExternallyPass())
 MODULE_PASS("extract-blocks", BlockExtractorPass({}, false))
 MODULE_PASS("forceattrs", ForceFunctionAttrsPass())
 MODULE_PASS("function-import", FunctionImportPass())
-MODULE_PASS("globaldce", GlobalDCEPass())
 MODULE_PASS("globalopt", GlobalOptPass())
 MODULE_PASS("globalsplit", GlobalSplitPass())
 MODULE_PASS("hotcoldsplit", HotColdSplittingPass())
 MODULE_PASS("inferattrs", InferFunctionAttrsPass())
 MODULE_PASS("inliner-wrapper", ModuleInlinerWrapperPass())
 MODULE_PASS("inliner-ml-advisor-release", ModuleInlinerWrapperPass(getInlineParams(), true, {}, InliningAdvisorMode::Release, 0))
 MODULE_PASS("print<inline-advisor>", InlineAdvisorAnalysisPrinterPass(dbgs()))
 MODULE_PASS("inliner-wrapper-no-mandatory-first", ModuleInlinerWrapperPass(
MODULE_PASS_WITH_PARAMS("loop-extract",
                         "LoopExtractorPass",
                         [](bool Single) {
                           if (Single)
                             return LoopExtractorPass(1);
                           return LoopExtractorPass();
                         },
                         parseLoopExtractorPassOptions,
                         "single")
+MODULE_PASS_WITH_PARAMS("globaldce",
+                        "GlobalDCEPass",
+                        [](bool InLTOPostLink) {
+                          return GlobalDCEPass(InLTOPostLink);
+                        },
+                        parseGlobalDCEPassOptions,
+                        "in-lto-post-link")
 MODULE_PASS_WITH_PARAMS("hwasan",
                         "HWAddressSanitizerPass",
                         [](HWAddressSanitizerOptions Opts) {
                           return HWAddressSanitizerPass(Opts);
                         },
                         parseHWASanPassOptions,
                         "kernel;recover")
 MODULE_PASS_WITH_PARAMS("asan",

llvm/lib/Transforms/IPO/GlobalDCE.cpp

if (Comdat *C = GV.getComdat()) {
     }
   }
 }
 
 void GlobalDCEPass::ScanVTables(Module &M) {
   SmallVector<MDNode *, 2> Types;
   LLVM_DEBUG(dbgs() << "Building type info -> vtable map\n");
 
-  auto *LTOPostLinkMD =
-      cast_or_null<ConstantAsMetadata>(M.getModuleFlag("LTOPostLink"));
-  bool LTOPostLink =
-      LTOPostLinkMD && !cast<ConstantInt>(LTOPostLinkMD->getValue())->isZero();
-
   for (GlobalVariable &GV : M.globals()) {
     Types.clear();
     GV.getMetadata(LLVMContext::MD_type, Types);
     if (GV.isDeclaration() || Types.empty())
       continue;
 
     // Use the typeid metadata on the vtable to build a mapping from typeids to
     // the list of (GV, offset) pairs which are the possible vtables for that
for (GlobalVariable &GV : M.globals()) {
     }
 
     // If the type corresponding to the vtable is private to this translation
     // unit, we know that we can see all virtual functions which might use it,
     // so VFE is safe.
     if (auto GO = dyn_cast<GlobalObject>(&GV)) {
       GlobalObject::VCallVisibility TypeVis = GO->getVCallVisibility();
       if (TypeVis == GlobalObject::VCallVisibilityTranslationUnit ||
-          (LTOPostLink &&
+          (InLTOPostLink &&
            TypeVis == GlobalObject::VCallVisibilityLinkageUnit)) {
         LLVM_DEBUG(dbgs() << GV.getName() << " is safe for VFE\n");
         VFESafeVTables.insert(&GV);
       }
     }
   }
 }
 
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
   ComdatMembers.clear();
   TypeIdMap.clear();
   VFESafeVTables.clear();
 
   if (Changed)
     return PreservedAnalyses::none();
   return PreservedAnalyses::all();
 }
+
+void GlobalDCEPass::printPipeline(
+    raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
+  static_cast<PassInfoMixin<GlobalDCEPass> *>(this)->printPipeline(
+      OS, MapClassName2PassName);
+  if (InLTOPostLink)
+    OS << "<vfe-linkage-unit-visibility>";
+}

llvm/test/CodeGen/AMDGPU/dwarf-multi-register-use-crash.ll

; CHECK-NEXT:  .Ltmp2:
   store i32 0, ptr %3, align 4
   call void @llvm.dbg.declare(metadata ptr %3, metadata !40, metadata !DIExpression()), !dbg !43
   ret void
 }
 
 attributes #0 = { nocallback nofree nosync nounwind readnone speculatable willreturn }
 
 !llvm.dbg.cu = !{!0, !25, !26}
-!llvm.module.flags = !{!27, !28, !29, !30, !31, !32, !33}
+!llvm.module.flags = !{!27, !28, !29, !30, !31, !32}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 15.0.0 (https://github.com/llvm/llvm-project.git 05256c8d95e0b15bcc502d595c15d902ff520f97)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !8, imports: !20, splitDebugInlining: false, nameTableKind: None)
 !1 = !DIFile(filename: "dummy", directory: "dummy", checksumkind: CSK_MD5, checksum: "b67bec84bdce3730b4a6f2ed8d50b85c")
 !2 = !{!3, !3, !3}
 !3 = distinct !DICompositeType(tag: DW_TAG_enumeration_type, name: "dummy", scope: !4, file: !1, line: 49, baseType: !5, size: 32, elements: !6, identifier: "dummy")
 !4 = !DINamespace(name: "dummy", scope: null)
 !5 = !DIBasicType(name: "dummy", size: 32, encoding: DW_ATE_unsigned)
 !6 = !{!7}

 !25 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 15.0.0 (https://github.com/llvm/llvm-project.git 05256c8d95e0b15bcc502d595c15d902ff520f97)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, imports: !20, splitDebugInlining: false, nameTableKind: None)
 !26 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 15.0.0 (https://github.com/llvm/llvm-project.git 05256c8d95e0b15bcc502d595c15d902ff520f97)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !24, imports: !20, splitDebugInlining: false, nameTableKind: None)
 !27 = !{i32 7, !"Dwarf Version", i32 5}
 !28 = !{i32 2, !"Debug Info Version", i32 3}
 !29 = !{i32 1, !"wchar_size", i32 4}
 !30 = !{i32 7, !"openmp", i32 50}
 !31 = !{i32 7, !"openmp-device", i32 50}
 !32 = !{i32 7, !"PIC Level", i32 2}
-!33 = !{i32 1, !"LTOPostLink", i32 1}
 !34 = distinct !DISubprogram(name: "dummy", linkageName: "dummy", scope: !35, file: !1, line: 49, type: !23, scopeLine: 288, flags: DIFlagEnumClass, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, declaration: !36, retainedNodes: !37)
 !35 = distinct !DICompositeType(tag: DW_TAG_class_type, file: !1, line: 49, size: 32, flags: DIFlagEnumClass, elements: !6, identifier: "dummy")
 !36 = !DISubprogram(name: "dummy", scope: !35, file: !1, line: 49, type: !23, scopeLine: 288, flags: DIFlagEnumClass, spFlags: DISPFlagOptimized)
 !37 = !{!38, !40, !41, !42}
 !38 = !DILocalVariable(name: "dummy", arg: 1, scope: !34, type: !39, flags: DIFlagEnumClass)
 !39 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 32)
 !40 = !DILocalVariable(name: "dummy", arg: 2, scope: !34, file: !1, line: 49, type: !5)
 !41 = !DILocalVariable(name: "dummy", arg: 3, scope: !34, file: !1, line: 49, type: !5)
 !42 = !DILocalVariable(name: "dummy", arg: 4, scope: !34, file: !1, line: 49, type: !5)
 !43 = !DILocation(line: 49, column: 9, scope: !34)

llvm/test/DebugInfo/MIR/X86/ldv_unreachable_blocks.mir

if.else.i103.i:                                   ; preds = %sw.bb.i
     br label %bar_length.exit105.i
   bar_length.exit105.i:                        ; preds = %if.else.i103.i, %sw.bb.i
     unreachable
   baz_size.exit:                  ; preds = %bar_length.exit131.i, %bar_length.exit105.i, %bar_length.exit.i.baz_size.exit_crit_edge
     unreachable
   }
   declare zeroext i8 @foo_len() local_unnamed_addr
   !llvm.dbg.cu = !{!0}
-  !llvm.module.flags = !{!3, !4}
+  !llvm.module.flags = !{!3}
   !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !6, producer: "Apple clang", isOptimized: true, flags: "-fsanitize=fuzzer-no-link,address", runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !2, splitDebugInlining: false, nameTableKind: None, sysroot: "/", sdk: "MacOSX.sdk")
   !2 = !{}
   !3 = !{i32 2, !"Debug Info Version", i32 3}
-  !4 = !{i32 1, !"LTOPostLink", i32 1}
   !5 = distinct !DISubprogram(name: "__foo_block_invoke", linkageName: "__foo_block_invoke", scope: !6, file: !6, line: 557, type: !7, scopeLine: 557, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
   !6 = !DIFile(filename: "t.c", directory: "")
   !7 = !DISubroutineType(types: !2)
   !10 = !DILocation(line: 558, column: 7, scope: !12)
   !12 = distinct !DILexicalBlock(scope: !5, file: !6, line: 557, column: 50)
 name:            __foo_block_invoke
 body:             |
   bb.0.entry:
     JCC_1 %bb.1, 5, implicit $eflags, debug-location !10
   bb.28.baz_size.exit:
     RET64 $al, debug-location !10
   bb.1:
     successors: 
   bb.25.if.else.i103.i (machine-block-address-taken):
     JMP_1 %bb.28

llvm/test/DebugInfo/MIR/X86/ldv_unreachable_blocks2.mir

 # RUN: llc -mtriple=x86_64-apple-macos %s -start-before=livedebugvalues -filetype=obj -o - | llvm-dwarfdump - | FileCheck %s
 # CHECK: DW_TAG_subprogram
 # Test that LiveDebugValues can handle MBBs that are not reachable in a RPOT.
 --- |
   define hidden zeroext i1 @__foo_block_invoke(i8* nocapture noundef readonly %.block_descriptor, i64 noundef %type) !dbg !7 {
   entry:
     unreachable
   do.body.i129.i:                                   ; preds = %if.else6.i128.i
     unreachable
   }
   !llvm.dbg.cu = !{!3}
-  !llvm.module.flags = !{!5, !6}
+  !llvm.module.flags = !{!5}
   !2 = !{}
   !3 = distinct !DICompileUnit(language: DW_LANG_C99, file: !4, producer: "clang", runtimeVersion: 0, emissionKind: FullDebug)
   !4 = !DIFile(filename: "t.c", directory: "/")
   !5 = !{i32 2, !"Debug Info Version", i32 3}
-  !6 = !{i32 1, !"LTOPostLink", i32 1}
   !7 = distinct !DISubprogram(name: "__foo_block_invoke", scope: !4, file: !4, line: 573, type: !9, scopeLine: 573, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !3, retainedNodes: !2)
   !9 = !DISubroutineType(types: !2)
   !11 = !DILocalVariable(name: ".block_descriptor", arg: 1, scope: !7, file: !4, line: 557, type: !12, flags: DIFlagArtificial)
   !12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64)
   !13 = !DICompositeType(tag: DW_TAG_structure_type, name: "__block_literal_1", scope: !4, file: !4, line: 557, size: 392, elements: !2)
   !15 = !DILocation(line: 558, column: 7, scope: !7)
 name:            __foo_block_invoke
 body:             |
   bb.0.entry:
     DBG_VALUE $rdi, $noreg, !11, !DIExpression(), debug-location !15
     $ecx = MOV32rr undef $edi, implicit $dil, debug-location !15
   bb.2:
     successors: 
     TRAP
   bb.21.do.body.i129.i (machine-block-address-taken):

llvm/test/DebugInfo/X86/subprogram-across-cus.ll

 define dso_local i32 @main() local_unnamed_addr !dbg !17 {
 entry:
   tail call fastcc void @_Z2f1v(), !dbg !21
   unreachable, !dbg !21
 }
 
 !llvm.dbg.cu = !{!0, !9}
 !llvm.ident = !{!10, !10}
-!llvm.module.flags = !{!11, !12, !13, !14, !15, !16}
+!llvm.module.flags = !{!11, !12, !13, !14, !15}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 12.0.0 ([e-mail]:llvm/llvm-project bc9ab9a5cd6bafc5e1293f3d5d51638f8f5cd26c)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, splitDebugInlining: false, nameTableKind: None)
 !1 = !DIFile(filename: "1.cpp", directory: "/tmp/bees")
 !2 = !{}
 !3 = !{!4}
 !4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression())
 !5 = distinct !DIGlobalVariable(name: "zzz", scope: !0, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true)
 !6 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64)
 !7 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "HHH", file: !8, line: 3, size: 8, flags: DIFlagTypePassByValue, elements: !2, identifier: "_ZTS3HHH")
 !8 = !DIFile(filename: "2.cpp", directory: "/tmp/bees")
 !9 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !8, producer: "clang version 12.0.0 ([e-mail]:llvm/llvm-project bc9ab9a5cd6bafc5e1293f3d5d51638f8f5cd26c)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
 !10 = !{!"clang version 12.0.0 ([e-mail]:llvm/llvm-project bc9ab9a5cd6bafc5e1293f3d5d51638f8f5cd26c)"}
 !11 = !{i32 7, !"Dwarf Version", i32 4}
 !12 = !{i32 2, !"Debug Info Version", i32 3}
 !13 = !{i32 1, !"wchar_size", i32 4}
 !14 = !{i32 1, !"ThinLTO", i32 0}
 !15 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
-!16 = !{i32 1, !"LTOPostLink", i32 1}
 !17 = distinct !DISubprogram(name: "main", scope: !8, file: !8, line: 10, type: !18, scopeLine: 10, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !9, retainedNodes: !2)
 !18 = !DISubroutineType(types: !19)
 !19 = !{!20}
 !20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 !21 = !DILocation(line: 6, column: 5, scope: !22, inlinedAt: !27)
 !22 = distinct !DISubprogram(name: "ccc<local>", linkageName: "_ZN3HHH3cccIZ4mainE5localEEiv", scope: !7, file: !8, line: 5, type: !18, scopeLine: 5, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !9, templateParams: !24, declaration: !23, retainedNodes: !2)
 !23 = !DISubprogram(name: "ccc<local>", linkageName: "_ZN3HHH3cccIZ4mainE5localEEiv", scope: !7, file: !8, line: 5, type: !18, scopeLine: 5, flags: DIFlagPrototyped | DIFlagStaticMember, spFlags: DISPFlagOptimized, templateParams: !24)
 !24 = !{!25}
 !25 = !DITemplateTypeParameter(name: "bbb", type: !26)
 !26 = !DICompositeType(tag: DW_TAG_structure_type, name: "local", scope: !17, file: !8, line: 11, size: 8, flags: DIFlagFwdDecl)
 !27 = distinct !DILocation(line: 12, column: 3, scope: !17)

llvm/test/LTO/ARM/lto-linking-metadata.ll

-; RUN: opt %s -o %t1.bc
-
-; RUN: llvm-lto %t1.bc -o %t1.save.opt -save-linked-module -save-merged-module -O1 --exported-symbol=foo
-; RUN: llvm-dis < %t1.save.opt.merged.bc | FileCheck %s
-; RUN: llvm-dis < %t1.save.opt.linked.bc | FileCheck %s --check-prefix=CHECK-LINKED
-
-; RUN: llvm-lto2 run %t1.bc -o %t.out.o -save-temps \
-; RUN:     -r=%t1.bc,foo,pxl
-; RUN: llvm-dis < %t.out.o.0.2.internalize.bc | FileCheck  %s
-
-target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv7a-unknown-linux"
-
-define void @foo() {
-entry:
-  ret void
-}
-
-; CHECK: !llvm.module.flags = !{[[MD_NUM:![0-9]+]]}
-; CHECK: [[MD_NUM]] = !{i32 1, !"LTOPostLink", i32 1}
-
-; CHECK-LINKED: @foo
-; CHECK-LINKED-NOT: LTOPostLink

llvm/test/Other/new-pm-print-pipeline.ll

 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='cgscc(function<no-rerun;eager-inv>(no-op-function))' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-31
 ; CHECK-31: cgscc(function<eager-inv;no-rerun>(no-op-function))
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='cgscc(function<no-rerun>(no-op-function))' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-32
 ; CHECK-32: cgscc(function<no-rerun>(no-op-function))
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(loop(loop-rotate<no-header-duplication;no-prepare-for-lto>))' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-33
 ; CHECK-33: function(loop(loop-rotate<no-header-duplication;no-prepare-for-lto>))
+
+; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='globaldce' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-34
+; CHECK-34: globaldce
+
+; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='globaldce<vfe-linkage-unit-visibility>' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-35
+; CHECK-35: globaldce<vfe-linkage-unit-visibility>

llvm/test/Transforms/GlobalDCE/virtual-functions-visibility-post-lto.ll

-; RUN: opt < %s -passes=globaldce -S | FileCheck %s
+; RUN: opt < %s -passes='globaldce<vfe-linkage-unit-visibility>' -S | FileCheck %s
+; RUN: opt < %s -passes='lto<O2>' -S | FileCheck %s
 
 ; structs A, B and C have vcall_visibility of public, linkage-unit and
 ; translation-unit respectively. This test is run after LTO linking (the
-; LTOPostLink metadata is present), so B and C can be VFE'd.
+; pass parameter simulates how GlobalDCE is invoked from the regular LTO
+; pipeline), so B and C can be VFE'd.
+
+;; Try again without being in the LTO post link, we can only eliminate C.
+; RUN: opt < %s -passes='globaldce' -S | FileCheck %s --check-prefix=NO-LTO
+; RUN: opt < %s -passes='default<O2>' -S | FileCheck %s --check-prefix=NO-LTO
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
 %struct.A = type { ptr }
 
 @_ZTV1A = hidden unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr null, ptr @_ZN1A3fooEv] }, align 8, !type !0, !type !1, !vcall_visibility !2
 
 define internal void @_ZN1AC2Ev(ptr %this) {
 entry:
   store ptr getelementptr inbounds ({ [3 x ptr] }, ptr @_ZTV1A, i64 0, inrange i32 0, i64 2), ptr %this, align 8
   ret void
 }
 
 ; CHECK: define {{.*}} @_ZN1A3fooEv(
+; NO-LTO: define {{.*}} @_ZN1A3fooEv(
 define internal void @_ZN1A3fooEv(ptr nocapture %this) {
 entry:
   ret void
 }
 
 define dso_local ptr @_Z6make_Av() {
 entry:
   %call = tail call ptr @_Znwm(i64 8)
   tail call void @_ZN1AC2Ev(ptr %call)
   ret ptr %call
 }
 
 
 %struct.B = type { ptr }
 
 @_ZTV1B = hidden unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr null, ptr @_ZN1B3fooEv] }, align 8, !type !0, !type !1, !vcall_visibility !3
 
 define internal void @_ZN1BC2Ev(ptr %this) {
 entry:
   store ptr getelementptr inbounds ({ [3 x ptr] }, ptr @_ZTV1B, i64 0, inrange i32 0, i64 2), ptr %this, align 8
   ret void
 }
 
 ; CHECK-NOT: define {{.*}} @_ZN1B3fooEv(
+; NO-LTO: define {{.*}} @_ZN1B3fooEv(
 define internal void @_ZN1B3fooEv(ptr nocapture %this) {
 entry:
   ret void
 }
 
 define dso_local ptr @_Z6make_Bv() {
 entry:
   %call = tail call ptr @_Znwm(i64 8)
   tail call void @_ZN1BC2Ev(ptr %call)
   ret ptr %call
 }
 
 
 %struct.C = type { ptr }
 
 @_ZTV1C = hidden unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr null, ptr @_ZN1C3fooEv] }, align 8, !type !0, !type !1, !vcall_visibility !4
 
 define internal void @_ZN1CC2Ev(ptr %this) {
 entry:
   store ptr getelementptr inbounds ({ [3 x ptr] }, ptr @_ZTV1C, i64 0, inrange i32 0, i64 2), ptr %this, align 8
   ret void
 }
 
 ; CHECK-NOT: define {{.*}} @_ZN1C3fooEv(
+; NO-LTO-NOT: define {{.*}} @_ZN1C3fooEv(
 define internal void @_ZN1C3fooEv(ptr nocapture %this) {
 entry:
   ret void
 }
 
 define dso_local ptr @_Z6make_Cv() {
 entry:
   %call = tail call ptr @_Znwm(i64 8)
   tail call void @_ZN1CC2Ev(ptr %call)
   ret ptr %call
 }
 
 declare dso_local noalias nonnull ptr @_Znwm(i64)
 
-!llvm.module.flags = !{!5, !6}
+!llvm.module.flags = !{!6}
 
 !0 = !{i64 16, !"_ZTS1A"}
 !1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
 !2 = !{i64 0} ; public vcall visibility
 !3 = !{i64 1} ; linkage-unit vcall visibility
 !4 = !{i64 2} ; translation-unit vcall visibility
-!5 = !{i32 1, !"LTOPostLink", i32 1}
 !6 = !{i32 1, !"Virtual Function Elim", i32 1}

llvm/test/Transforms/GlobalDCE/vtable-rtti.ll

entry:
   tail call void @_ZN1AC2Ev(ptr %call)
   ret ptr %call
 }
 
 
 declare dso_local noalias nonnull ptr @_Znwm(i64)
 @_ZTVN10__cxxabiv117__class_type_infoE = external dso_local global ptr
 
-!llvm.module.flags = !{!3, !4}
+!llvm.module.flags = !{!4}
 
 !0 = !{i64 16, !"_ZTS1A"}
 !1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
 !2 = !{i64 2} ; translation-unit vcall visibility
-!3 = !{i32 1, !"LTOPostLink", i32 1}
 !4 = !{i32 1, !"Virtual Function Elim", i32 1}

llvm/test/Transforms/WholeProgramDevirt/devirt-single-impl2.ll

 @_ZTV1A = weak_odr hidden unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr @_ZTI1A, ptr @_ZNK1A1fEv] }, comdat, align 8, !type !0, !type !1
 @_ZTI1A = external hidden constant { ptr, ptr }, align 8
 define available_externally hidden i32 @_ZNK1A1fEv(ptr %this) unnamed_addr align 2 {
 entry:
   ret i32 3
 }
 
 !llvm.ident = !{!2}
-!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.module.flags = !{!3, !4, !5}
 
 !0 = !{i64 16, !"_ZTS1A"}
 !1 = !{i64 16, !"_ZTSM1AKFivE.virtual"}
 !2 = !{!"clang version 10.0.0 (trunk 373596)"}
 !3 = !{i32 1, !"wchar_size", i32 4}
 !4 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
 !5 = !{i32 1, !"ThinLTO", i32 0}
-!6 = !{i32 1, !"LTOPostLink", i32 1}

llvm/test/tools/llvm-reduce/reduce-module-flags.ll

 
 ; RESULT1: !llvm.module.flags = !{!0, !1}
 ; RESULT1: !0 = !{i32 1, !"wchar_size", i32 4}
 ; RESULT1: !1 = !{i32 7, !"openmp", i32 50}
 
 
 ; RESULT2: !llvm.module.flags = !{}
 
-!llvm.module.flags = !{!0, !1, !2, !3, !4, !5}
+!llvm.module.flags = !{!0, !1, !2, !3, !4}
 
 !0 = !{i32 1, !"amdgpu_code_object_version", i32 400}
 !1 = !{i32 1, !"wchar_size", i32 4}
 !2 = !{i32 7, !"openmp", i32 50}
 !3 = !{i32 7, !"openmp-device", i32 50}
 !4 = !{i32 8, !"PIC Level", i32 1}
-!5 = !{i32 1, !"LTOPostLink", i32 1}