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[LTO][GlobalDCE] Use pass parameter instead of module flag for LTO phase
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. Differential Revision: https://reviews.llvm.org/D153655
1 parent a2a4b60 commit 200cc95

17 files changed

+55
-56
lines changed

Diff for: ‎llvm/include/llvm/Transforms/IPO/GlobalDCE.h

+7
Original file line numberDiff line numberDiff line change
@@ -35,9 +35,16 @@ class Value;
3535
/// Pass to remove unused function declarations.
3636
class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
3737
public:
38+
GlobalDCEPass(bool InLTOPostLink = false) : InLTOPostLink(InLTOPostLink) {}
39+
3840
PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
3941

42+
void printPipeline(raw_ostream &OS,
43+
function_ref<StringRef(StringRef)> MapClassName2PassName);
44+
4045
private:
46+
bool InLTOPostLink = false;
47+
4148
SmallPtrSet<GlobalValue*, 32> AliveGlobals;
4249

4350
/// Global -> Global that uses this global.

Diff for: ‎llvm/lib/LTO/LTO.cpp

-2
Original file line numberDiff line numberDiff line change
@@ -1290,8 +1290,6 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
12901290
GV->setLinkage(GlobalValue::InternalLinkage);
12911291
}
12921292

1293-
RegularLTO.CombinedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
1294-
12951293
if (Conf.PostInternalizeModuleHook &&
12961294
!Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
12971295
return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));

Diff for: ‎llvm/lib/LTO/LTOCodeGenerator.cpp

-3
Original file line numberDiff line numberDiff line change
@@ -617,9 +617,6 @@ bool LTOCodeGenerator::optimize() {
617617
// Mark which symbols can not be internalized
618618
this->applyScopeRestrictions();
619619

620-
// Write LTOPostLink flag for passes that require all the modules.
621-
MergedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
622-
623620
// Add an appropriate DataLayout instance for this module...
624621
MergedModule->setDataLayout(TargetMach->createDataLayout());
625622

Diff for: ‎llvm/lib/Passes/PassBuilder.cpp

+4
Original file line numberDiff line numberDiff line change
@@ -672,6 +672,10 @@ Expected<bool> parseSinglePassOption(StringRef Params, StringRef OptionName,
672672
return Result;
673673
}
674674

675+
Expected<bool> parseGlobalDCEPassOptions(StringRef Params) {
676+
return parseSinglePassOption(Params, "vfe-linkage-unit-visibility", "GlobalDCE");
677+
}
678+
675679
Expected<bool> parseInlinerPassOptions(StringRef Params) {
676680
return parseSinglePassOption(Params, "only-mandatory", "InlinerPass");
677681
}

Diff for: ‎llvm/lib/Passes/PassBuilderPipelines.cpp

+3-3
Original file line numberDiff line numberDiff line change
@@ -1638,7 +1638,7 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
16381638

16391639
// Remove unused virtual tables to improve the quality of code generated by
16401640
// whole-program devirtualization and bitset lowering.
1641-
MPM.addPass(GlobalDCEPass());
1641+
MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
16421642

16431643
// Do basic inference of function attributes from known properties of system
16441644
// libraries and other oracles.
@@ -1757,7 +1757,7 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
17571757
MPM.addPass(OpenMPOptPass(ThinOrFullLTOPhase::FullLTOPostLink));
17581758

17591759
// Garbage collect dead functions.
1760-
MPM.addPass(GlobalDCEPass());
1760+
MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
17611761

17621762
// If we didn't decide to inline a function, check to see if we can
17631763
// transform it to pass arguments by value instead of by reference.
@@ -1895,7 +1895,7 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
18951895
MPM.addPass(EliminateAvailableExternallyPass());
18961896

18971897
// Now that we have optimized the program, discard unreachable functions.
1898-
MPM.addPass(GlobalDCEPass());
1898+
MPM.addPass(GlobalDCEPass(/*InLTOPostLink=*/true));
18991899

19001900
if (PTO.MergeFunctions)
19011901
MPM.addPass(MergeFunctionsPass());

Diff for: ‎llvm/lib/Passes/PassRegistry.def

+7-1
Original file line numberDiff line numberDiff line change
@@ -60,7 +60,6 @@ MODULE_PASS("elim-avail-extern", EliminateAvailableExternallyPass())
6060
MODULE_PASS("extract-blocks", BlockExtractorPass({}, false))
6161
MODULE_PASS("forceattrs", ForceFunctionAttrsPass())
6262
MODULE_PASS("function-import", FunctionImportPass())
63-
MODULE_PASS("globaldce", GlobalDCEPass())
6463
MODULE_PASS("globalopt", GlobalOptPass())
6564
MODULE_PASS("globalsplit", GlobalSplitPass())
6665
MODULE_PASS("hotcoldsplit", HotColdSplittingPass())
@@ -142,6 +141,13 @@ MODULE_PASS_WITH_PARAMS("loop-extract",
142141
},
143142
parseLoopExtractorPassOptions,
144143
"single")
144+
MODULE_PASS_WITH_PARAMS("globaldce",
145+
"GlobalDCEPass",
146+
[](bool InLTOPostLink) {
147+
return GlobalDCEPass(InLTOPostLink);
148+
},
149+
parseGlobalDCEPassOptions,
150+
"in-lto-post-link")
145151
MODULE_PASS_WITH_PARAMS("hwasan",
146152
"HWAddressSanitizerPass",
147153
[](HWAddressSanitizerOptions Opts) {

Diff for: ‎llvm/lib/Transforms/IPO/GlobalDCE.cpp

+9-6
Original file line numberDiff line numberDiff line change
@@ -120,11 +120,6 @@ void GlobalDCEPass::ScanVTables(Module &M) {
120120
SmallVector<MDNode *, 2> Types;
121121
LLVM_DEBUG(dbgs() << "Building type info -> vtable map\n");
122122

123-
auto *LTOPostLinkMD =
124-
cast_or_null<ConstantAsMetadata>(M.getModuleFlag("LTOPostLink"));
125-
bool LTOPostLink =
126-
LTOPostLinkMD && !cast<ConstantInt>(LTOPostLinkMD->getValue())->isZero();
127-
128123
for (GlobalVariable &GV : M.globals()) {
129124
Types.clear();
130125
GV.getMetadata(LLVMContext::MD_type, Types);
@@ -151,7 +146,7 @@ void GlobalDCEPass::ScanVTables(Module &M) {
151146
if (auto GO = dyn_cast<GlobalObject>(&GV)) {
152147
GlobalObject::VCallVisibility TypeVis = GO->getVCallVisibility();
153148
if (TypeVis == GlobalObject::VCallVisibilityTranslationUnit ||
154-
(LTOPostLink &&
149+
(InLTOPostLink &&
155150
TypeVis == GlobalObject::VCallVisibilityLinkageUnit)) {
156151
LLVM_DEBUG(dbgs() << GV.getName() << " is safe for VFE\n");
157152
VFESafeVTables.insert(&GV);
@@ -414,3 +409,11 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
414409
return PreservedAnalyses::none();
415410
return PreservedAnalyses::all();
416411
}
412+
413+
void GlobalDCEPass::printPipeline(
414+
raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
415+
static_cast<PassInfoMixin<GlobalDCEPass> *>(this)->printPipeline(
416+
OS, MapClassName2PassName);
417+
if (InLTOPostLink)
418+
OS << "<vfe-linkage-unit-visibility>";
419+
}

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

+1-2
Original file line numberDiff line numberDiff line change
@@ -112,7 +112,7 @@ define weak_odr void @test(i32 %0) !dbg !34 {
112112
attributes #0 = { nocallback nofree nosync nounwind readnone speculatable willreturn }
113113

114114
!llvm.dbg.cu = !{!0, !25, !26}
115-
!llvm.module.flags = !{!27, !28, !29, !30, !31, !32, !33}
115+
!llvm.module.flags = !{!27, !28, !29, !30, !31, !32}
116116

117117
!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)
118118
!1 = !DIFile(filename: "dummy", directory: "dummy", checksumkind: CSK_MD5, checksum: "b67bec84bdce3730b4a6f2ed8d50b85c")
@@ -147,7 +147,6 @@ attributes #0 = { nocallback nofree nosync nounwind readnone speculatable willre
147147
!30 = !{i32 7, !"openmp", i32 50}
148148
!31 = !{i32 7, !"openmp-device", i32 50}
149149
!32 = !{i32 7, !"PIC Level", i32 2}
150-
!33 = !{i32 1, !"LTOPostLink", i32 1}
151150
!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)
152151
!35 = distinct !DICompositeType(tag: DW_TAG_class_type, file: !1, line: 49, size: 32, flags: DIFlagEnumClass, elements: !6, identifier: "dummy")
153152
!36 = !DISubprogram(name: "dummy", scope: !35, file: !1, line: 49, type: !23, scopeLine: 288, flags: DIFlagEnumClass, spFlags: DISPFlagOptimized)

Diff for: ‎llvm/test/DebugInfo/MIR/X86/ldv_unreachable_blocks.mir

+1-2
Original file line numberDiff line numberDiff line change
@@ -16,11 +16,10 @@
1616
}
1717
declare zeroext i8 @foo_len() local_unnamed_addr
1818
!llvm.dbg.cu = !{!0}
19-
!llvm.module.flags = !{!3, !4}
19+
!llvm.module.flags = !{!3}
2020
!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")
2121
!2 = !{}
2222
!3 = !{i32 2, !"Debug Info Version", i32 3}
23-
!4 = !{i32 1, !"LTOPostLink", i32 1}
2423
!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)
2524
!6 = !DIFile(filename: "t.c", directory: "")
2625
!7 = !DISubroutineType(types: !2)

Diff for: ‎llvm/test/DebugInfo/MIR/X86/ldv_unreachable_blocks2.mir

+1-2
Original file line numberDiff line numberDiff line change
@@ -9,12 +9,11 @@
99
unreachable
1010
}
1111
!llvm.dbg.cu = !{!3}
12-
!llvm.module.flags = !{!5, !6}
12+
!llvm.module.flags = !{!5}
1313
!2 = !{}
1414
!3 = distinct !DICompileUnit(language: DW_LANG_C99, file: !4, producer: "clang", runtimeVersion: 0, emissionKind: FullDebug)
1515
!4 = !DIFile(filename: "t.c", directory: "/")
1616
!5 = !{i32 2, !"Debug Info Version", i32 3}
17-
!6 = !{i32 1, !"LTOPostLink", i32 1}
1817
!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)
1918
!9 = !DISubroutineType(types: !2)
2019
!11 = !DILocalVariable(name: ".block_descriptor", arg: 1, scope: !7, file: !4, line: 557, type: !12, flags: DIFlagArtificial)

Diff for: ‎llvm/test/DebugInfo/X86/subprogram-across-cus.ll

+1-2
Original file line numberDiff line numberDiff line change
@@ -61,7 +61,7 @@ entry:
6161

6262
!llvm.dbg.cu = !{!0, !9}
6363
!llvm.ident = !{!10, !10}
64-
!llvm.module.flags = !{!11, !12, !13, !14, !15, !16}
64+
!llvm.module.flags = !{!11, !12, !13, !14, !15}
6565

6666
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 12.0.0 ([email protected]:llvm/llvm-project bc9ab9a5cd6bafc5e1293f3d5d51638f8f5cd26c)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, splitDebugInlining: false, nameTableKind: None)
6767
!1 = !DIFile(filename: "1.cpp", directory: "/tmp/bees")
@@ -79,7 +79,6 @@ entry:
7979
!13 = !{i32 1, !"wchar_size", i32 4}
8080
!14 = !{i32 1, !"ThinLTO", i32 0}
8181
!15 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
82-
!16 = !{i32 1, !"LTOPostLink", i32 1}
8382
!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)
8483
!18 = !DISubroutineType(types: !19)
8584
!19 = !{!20}

Diff for: ‎llvm/test/LTO/ARM/lto-linking-metadata.ll

-23
This file was deleted.

Diff for: ‎llvm/test/Other/new-pm-print-pipeline.ll

+6
Original file line numberDiff line numberDiff line change
@@ -114,3 +114,9 @@
114114

115115
; 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
116116
; CHECK-33: function(loop(loop-rotate<no-header-duplication;no-prepare-for-lto>))
117+
118+
; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='globaldce' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-34
119+
; CHECK-34: globaldce
120+
121+
; 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
122+
; CHECK-35: globaldce<vfe-linkage-unit-visibility>

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

+12-4
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,14 @@
1-
; RUN: opt < %s -passes=globaldce -S | FileCheck %s
1+
; RUN: opt < %s -passes='globaldce<vfe-linkage-unit-visibility>' -S | FileCheck %s
2+
; RUN: opt < %s -passes='lto<O2>' -S | FileCheck %s
23

34
; structs A, B and C have vcall_visibility of public, linkage-unit and
45
; translation-unit respectively. This test is run after LTO linking (the
5-
; LTOPostLink metadata is present), so B and C can be VFE'd.
6+
; pass parameter simulates how GlobalDCE is invoked from the regular LTO
7+
; pipeline), so B and C can be VFE'd.
8+
9+
;; Try again without being in the LTO post link, we can only eliminate C.
10+
; RUN: opt < %s -passes='globaldce' -S | FileCheck %s --check-prefix=NO-LTO
11+
; RUN: opt < %s -passes='default<O2>' -S | FileCheck %s --check-prefix=NO-LTO
612

713
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
814

@@ -17,6 +23,7 @@ entry:
1723
}
1824

1925
; CHECK: define {{.*}} @_ZN1A3fooEv(
26+
; NO-LTO: define {{.*}} @_ZN1A3fooEv(
2027
define internal void @_ZN1A3fooEv(ptr nocapture %this) {
2128
entry:
2229
ret void
@@ -41,6 +48,7 @@ entry:
4148
}
4249

4350
; CHECK-NOT: define {{.*}} @_ZN1B3fooEv(
51+
; NO-LTO: define {{.*}} @_ZN1B3fooEv(
4452
define internal void @_ZN1B3fooEv(ptr nocapture %this) {
4553
entry:
4654
ret void
@@ -65,6 +73,7 @@ entry:
6573
}
6674

6775
; CHECK-NOT: define {{.*}} @_ZN1C3fooEv(
76+
; NO-LTO-NOT: define {{.*}} @_ZN1C3fooEv(
6877
define internal void @_ZN1C3fooEv(ptr nocapture %this) {
6978
entry:
7079
ret void
@@ -79,12 +88,11 @@ entry:
7988

8089
declare dso_local noalias nonnull ptr @_Znwm(i64)
8190

82-
!llvm.module.flags = !{!5, !6}
91+
!llvm.module.flags = !{!6}
8392

8493
!0 = !{i64 16, !"_ZTS1A"}
8594
!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
8695
!2 = !{i64 0} ; public vcall visibility
8796
!3 = !{i64 1} ; linkage-unit vcall visibility
8897
!4 = !{i64 2} ; translation-unit vcall visibility
89-
!5 = !{i32 1, !"LTOPostLink", i32 1}
9098
!6 = !{i32 1, !"Virtual Function Elim", i32 1}

Diff for: ‎llvm/test/Transforms/GlobalDCE/vtable-rtti.ll

+1-2
Original file line numberDiff line numberDiff line change
@@ -37,10 +37,9 @@ entry:
3737
declare dso_local noalias nonnull ptr @_Znwm(i64)
3838
@_ZTVN10__cxxabiv117__class_type_infoE = external dso_local global ptr
3939

40-
!llvm.module.flags = !{!3, !4}
40+
!llvm.module.flags = !{!4}
4141

4242
!0 = !{i64 16, !"_ZTS1A"}
4343
!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
4444
!2 = !{i64 2} ; translation-unit vcall visibility
45-
!3 = !{i32 1, !"LTOPostLink", i32 1}
4645
!4 = !{i32 1, !"Virtual Function Elim", i32 1}

Diff for: ‎llvm/test/Transforms/WholeProgramDevirt/devirt-single-impl2.ll

+1-2
Original file line numberDiff line numberDiff line change
@@ -34,12 +34,11 @@ entry:
3434
}
3535

3636
!llvm.ident = !{!2}
37-
!llvm.module.flags = !{!3, !4, !5, !6}
37+
!llvm.module.flags = !{!3, !4, !5}
3838

3939
!0 = !{i64 16, !"_ZTS1A"}
4040
!1 = !{i64 16, !"_ZTSM1AKFivE.virtual"}
4141
!2 = !{!"clang version 10.0.0 (trunk 373596)"}
4242
!3 = !{i32 1, !"wchar_size", i32 4}
4343
!4 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
4444
!5 = !{i32 1, !"ThinLTO", i32 0}
45-
!6 = !{i32 1, !"LTOPostLink", i32 1}

Diff for: ‎llvm/test/tools/llvm-reduce/reduce-module-flags.ll

+1-2
Original file line numberDiff line numberDiff line change
@@ -30,11 +30,10 @@
3030

3131
; RESULT2: !llvm.module.flags = !{}
3232

33-
!llvm.module.flags = !{!0, !1, !2, !3, !4, !5}
33+
!llvm.module.flags = !{!0, !1, !2, !3, !4}
3434

3535
!0 = !{i32 1, !"amdgpu_code_object_version", i32 400}
3636
!1 = !{i32 1, !"wchar_size", i32 4}
3737
!2 = !{i32 7, !"openmp", i32 50}
3838
!3 = !{i32 7, !"openmp-device", i32 50}
3939
!4 = !{i32 8, !"PIC Level", i32 1}
40-
!5 = !{i32 1, !"LTOPostLink", i32 1}

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