[LTO][ThinLTO] Use the linker resolutions to mark global values as dso_local.

Now that we have a way to mark GlobalValues as local we can use the symbol
resolutions that the linker plugin provides as part of lto/thinlto link
step to refine the compilers view on what symbols will end up being local.

Differential Revision: https://reviews.llvm.org/D35702

llvm-svn: 317374

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -148,11 +148,15 @@ public:
     /// In combined summary, indicate that the global value is live.
     unsigned Live : 1;
 
+    /// Indicates that the linker resolved the symbol to a definition from
+    /// within the same linkage unit.
+    unsigned DSOLocal : 1;
+
     /// Convenience Constructors
     explicit GVFlags(GlobalValue::LinkageTypes Linkage,
-                     bool NotEligibleToImport, bool Live)
+                     bool NotEligibleToImport, bool Live, bool IsLocal)
         : Linkage(Linkage), NotEligibleToImport(NotEligibleToImport),
-          Live(Live) {}
+          Live(Live), DSOLocal(IsLocal) {}
   };
 
 private:
@@ -229,6 +233,10 @@ public:
 
   void setLive(bool Live) { Flags.Live = Live; }
 
+  void setDSOLocal(bool Local) { Flags.DSOLocal = Local; }
+
+  bool isDSOLocal() const { return Flags.DSOLocal; }
+
   /// Flag that this global value cannot be imported.
   void setNotEligibleToImport() { Flags.NotEligibleToImport = true; }
 

llvm/include/llvm/IR/ModuleSummaryIndexYAML.h

@@ -135,7 +135,7 @@ template <> struct MappingTraits<TypeIdSummary> {
 
 struct FunctionSummaryYaml {
   unsigned Linkage;
-  bool NotEligibleToImport, Live;
+  bool NotEligibleToImport, Live, IsLocal;
   std::vector<uint64_t> TypeTests;
   std::vector<FunctionSummary::VFuncId> TypeTestAssumeVCalls,
       TypeCheckedLoadVCalls;
@@ -177,6 +177,7 @@ template <> struct MappingTraits<FunctionSummaryYaml> {
     io.mapOptional("Linkage", summary.Linkage);
     io.mapOptional("NotEligibleToImport", summary.NotEligibleToImport);
     io.mapOptional("Live", summary.Live);
+    io.mapOptional("Local", summary.IsLocal);
     io.mapOptional("TypeTests", summary.TypeTests);
     io.mapOptional("TypeTestAssumeVCalls", summary.TypeTestAssumeVCalls);
     io.mapOptional("TypeCheckedLoadVCalls", summary.TypeCheckedLoadVCalls);
@@ -211,7 +212,7 @@ template <> struct CustomMappingTraits<GlobalValueSummaryMapTy> {
       Elem.SummaryList.push_back(llvm::make_unique<FunctionSummary>(
           GlobalValueSummary::GVFlags(
               static_cast<GlobalValue::LinkageTypes>(FSum.Linkage),
-              FSum.NotEligibleToImport, FSum.Live),
+              FSum.NotEligibleToImport, FSum.Live, FSum.IsLocal),
           0, FunctionSummary::FFlags{}, ArrayRef<ValueInfo>{},
           ArrayRef<FunctionSummary::EdgeTy>{}, std::move(FSum.TypeTests),
           std::move(FSum.TypeTestAssumeVCalls),
@@ -228,7 +229,8 @@ template <> struct CustomMappingTraits<GlobalValueSummaryMapTy> {
           FSums.push_back(FunctionSummaryYaml{
               FSum->flags().Linkage,
               static_cast<bool>(FSum->flags().NotEligibleToImport),
-              static_cast<bool>(FSum->flags().Live), FSum->type_tests(),
+              static_cast<bool>(FSum->flags().Live),
+              static_cast<bool>(FSum->flags().DSOLocal), FSum->type_tests(),
               FSum->type_test_assume_vcalls(), FSum->type_checked_load_vcalls(),
               FSum->type_test_assume_const_vcalls(),
               FSum->type_checked_load_const_vcalls()});

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

@@ -303,7 +303,7 @@ computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
       // FIXME: refactor this to use the same code that inliner is using.
       F.isVarArg();
   GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
-                                    /* Live = */ false);
+                                    /* Live = */ false, F.isDSOLocal());
   FunctionSummary::FFlags FunFlags{
       F.hasFnAttribute(Attribute::ReadNone),
       F.hasFnAttribute(Attribute::ReadOnly),
@@ -329,7 +329,7 @@ computeVariableSummary(ModuleSummaryIndex &Index, const GlobalVariable &V,
   findRefEdges(Index, &V, RefEdges, Visited);
   bool NonRenamableLocal = isNonRenamableLocal(V);
   GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false);
+                                    /* Live = */ false, V.isDSOLocal());
   auto GVarSummary =
       llvm::make_unique<GlobalVarSummary>(Flags, RefEdges.takeVector());
   if (NonRenamableLocal)
@@ -342,7 +342,7 @@ computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
                     DenseSet<GlobalValue::GUID> &CantBePromoted) {
   bool NonRenamableLocal = isNonRenamableLocal(A);
   GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false);
+                                    /* Live = */ false, A.isDSOLocal());
   auto AS = llvm::make_unique<AliasSummary>(Flags);
   auto *Aliasee = A.getBaseObject();
   auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
@@ -410,7 +410,8 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
           assert(GV->isDeclaration() && "Def in module asm already has definition");
           GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
                                               /* NotEligibleToImport = */ true,
-                                              /* Live = */ true);
+                                              /* Live = */ true,
+                                              /* Local */ GV->isDSOLocal());
           CantBePromoted.insert(GlobalValue::getGUID(Name));
           // Create the appropriate summary type.
           if (Function *F = dyn_cast<Function>(GV)) {

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -889,7 +889,9 @@ static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags,
   // to work correctly on earlier versions, we must conservatively treat all
   // values as live.
   bool Live = (RawFlags & 0x2) || Version < 3;
-  return GlobalValueSummary::GVFlags(Linkage, NotEligibleToImport, Live);
+  bool Local = (RawFlags & 0x4);
+
+  return GlobalValueSummary::GVFlags(Linkage, NotEligibleToImport, Live, Local);
 }
 
 static GlobalValue::VisibilityTypes getDecodedVisibility(unsigned Val) {

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -955,6 +955,8 @@ static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) {
 
   RawFlags |= Flags.NotEligibleToImport; // bool
   RawFlags |= (Flags.Live << 1);
+  RawFlags |= (Flags.DSOLocal << 2);
+
   // Linkage don't need to be remapped at that time for the summary. Any future
   // change to the getEncodedLinkage() function will need to be taken into
   // account here as well.

llvm/lib/LTO/LTO.cpp

@@ -630,6 +630,9 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
           NonPrevailingComdats.insert(GV->getComdat());
         cast<GlobalObject>(GV)->setComdat(nullptr);
       }
+
+      // Set the 'local' flag based on the linker resolution for this symbol.
+      GV->setDSOLocal(Res.FinalDefinitionInLinkageUnit);
     }
     // Common resolution: collect the maximum size/alignment over all commons.
     // We also record if we see an instance of a common as prevailing, so that
@@ -643,7 +646,6 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
       CommonRes.Prevailing |= Res.Prevailing;
     }
 
-    // FIXME: use proposed local attribute for FinalDefinitionInLinkageUnit.
   }
   if (!M.getComdatSymbolTable().empty())
     for (GlobalValue &GV : M.global_values())
@@ -698,10 +700,10 @@ Error LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
     assert(ResI != ResE);
     SymbolResolution Res = *ResI++;
 
-    if (Res.Prevailing) {
+    if (!Sym.getIRName().empty()) {
-      if (!Sym.getIRName().empty()) {
+      auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
-        auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
+          Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
-            Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
+      if (Res.Prevailing) {
         ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
 
         // For linker redefined symbols (via --wrap or --defsym) we want to
@@ -713,6 +715,15 @@ Error LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
                   GUID, BM.getModuleIdentifier()))
             S->setLinkage(GlobalValue::WeakAnyLinkage);
       }
+
+      // If the linker resolved the symbol to a local definition then mark it
+      // as local in the summary for the module we are adding.
+      if (Res.FinalDefinitionInLinkageUnit) {
+        if (auto S = ThinLTO.CombinedIndex.findSummaryInModule(
+                GUID, BM.getModuleIdentifier())) {
+          S->setDSOLocal(true);
+        }
+      }
     }
   }
 

llvm/lib/Transforms/Utils/FunctionImportUtils.cpp

@@ -203,6 +203,23 @@ FunctionImportGlobalProcessing::getLinkage(const GlobalValue *SGV,
 }
 
 void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
+
+  // Check the summaries to see if the symbol gets resolved to a known local
+  // definition.
+  if (GV.hasName()) {
+    ValueInfo VI = ImportIndex.getValueInfo(GV.getGUID());
+    if (VI) {
+      // Need to check all summaries are local in case of hash collisions.
+      bool IsLocal = VI.getSummaryList().size() &&
+          llvm::all_of(VI.getSummaryList(),
+                       [](const std::unique_ptr<GlobalValueSummary> &Summary) {
+                         return Summary->isDSOLocal();
+                       });
+      if (IsLocal)
+        GV.setDSOLocal(true);
+    }
+  }
+
   bool DoPromote = false;
   if (GV.hasLocalLinkage() &&
       ((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) {

llvm/test/Bitcode/thinlto-summary-local-5.0.ll

@@ -0,0 +1,22 @@
+; Bitcode compatibility test for dso_local flag in thin-lto summaries.
+; Checks that older bitcode summaries without the dso_local op are still
+; properly parsed and don't set GlobalValues as dso_local.
+
+; RUN: llvm-dis < %s.bc | FileCheck %s
+; RUN: llvm-bcanalyzer -dump %s.bc | FileCheck %s --check-prefix=BCAN
+
+define void @foo() {
+;CHECK-DAG:define void @foo()
+      ret void
+}
+
+@bar = global i32 0
+;CHECK-DAG: @bar = global i32 0
+
+@baz = alias i32, i32* @bar
+;CHECK-DAG: @bar = global i32 0
+
+;BCAN: <SOURCE_FILENAME
+;BCAN-NEXT: <GLOBALVAR {{.*}} op7=0/>
+;BCAN-NEXT: <FUNCTION {{.*}} op16=0/>
+;BCAN-NEXT: <ALIAS {{.*}} op9=0/>

llvm/test/LTO/Resolution/X86/comdat-mixed-lto.ll

@@ -17,7 +17,7 @@
 ; would clash with the copy from this module.
 ; RUN: llvm-dis %t3.0.0.preopt.bc -o - | FileCheck %s
 ; CHECK: define internal void @__cxx_global_var_init() section ".text.startup" {
-; CHECK: define available_externally void @testglobfunc() section ".text.startup" {
+; CHECK: define available_externally dso_local void @testglobfunc() section ".text.startup" {
 
 ; ModuleID = 'comdat-mixed-lto.o'
 source_filename = "comdat-mixed-lto.cpp"

llvm/test/LTO/Resolution/X86/comdat.ll

@@ -70,14 +70,14 @@ bb11:
 ; CHECK-DAG: @a23 = alias i32 (i8*), i32 (i8*)* @f1.2{{$}}
 ; CHECK-DAG: @a24 = alias i16, bitcast (i32 (i8*)* @f1.2 to i16*)
 
-; CHECK:      define weak_odr i32 @f1(i8*) comdat($c1) {
+; CHECK:      define weak_odr dso_local i32 @f1(i8*) comdat($c1) {
 ; CHECK-NEXT: bb10:
 ; CHECK-NEXT:   br label %bb11{{$}}
 ; CHECK:      bb11:
 ; CHECK-NEXT:   ret i32 42
 ; CHECK-NEXT: }
 
-; CHECK:      define internal i32 @f1.2(i8* %this) comdat($c2) {
+; CHECK:      define internal dso_local i32 @f1.2(i8* %this) comdat($c2) {
 ; CHECK-NEXT: bb20:
 ; CHECK-NEXT:   store i8* %this, i8** null
 ; CHECK-NEXT:   br label %bb21

llvm/test/LTO/Resolution/X86/commons.ll

@@ -4,7 +4,7 @@
 ; RUN: llvm-dis -o - %t.out.0.0.preopt.bc  | FileCheck %s
 
 ; A strong definition should override the common
-; CHECK: @x = global i32 42, align 4
+; CHECK: @x = dso_local global i32 42, align 4
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"

llvm/test/ThinLTO/X86/deadstrip.ll

@@ -18,8 +18,8 @@
 ; RUN:   -r %t2.bc,_boo,pl \
 ; RUN:   -r %t2.bc,_dead_func,pl \
 ; RUN:   -r %t2.bc,_another_dead_func,pl
-; RUN: llvm-dis < %t.out.0.3.import.bc | FileCheck %s
+; RUN: llvm-dis < %t.out.0.3.import.bc | FileCheck %s --check-prefix=LTO2
-; RUN: llvm-dis < %t.out.1.3.import.bc | FileCheck %s --check-prefix=CHECK2
+; RUN: llvm-dis < %t.out.1.3.import.bc | FileCheck %s --check-prefix=LTO2-CHECK2
 ; RUN: llvm-nm %t.out.1 | FileCheck %s --check-prefix=CHECK2-NM
 
 ; RUN: llvm-bcanalyzer -dump %t.out.index.bc | FileCheck %s --check-prefix=COMBINED
@@ -27,14 +27,14 @@
 ; COMBINED-DAG: <COMBINED {{.*}} op2=55
 ; Live, Internal
 ; COMBINED-DAG: <COMBINED {{.*}} op2=39
-; Live, External
+; Live, Local, External
-; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; COMBINED-DAG: <COMBINED {{.*}} op2=96
-; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; COMBINED-DAG: <COMBINED {{.*}} op2=96
-; COMBINED-DAG: <COMBINED {{.*}} op2=32
+; COMBINED-DAG: <COMBINED {{.*}} op2=96
-; (Dead)
+; Local, (Dead)
-; COMBINED-DAG: <COMBINED {{.*}} op2=0
+; COMBINED-DAG: <COMBINED {{.*}} op2=64
-; COMBINED-DAG: <COMBINED {{.*}} op2=0
+; COMBINED-DAG: <COMBINED {{.*}} op2=64
-; COMBINED-DAG: <COMBINED {{.*}} op2=0
+; COMBINED-DAG: <COMBINED {{.*}} op2=64
 
 ; Dead-stripping on the index allows to internalize these,
 ; and limit the import of @baz thanks to early pruning.
@@ -45,10 +45,18 @@
 ; CHECK: define internal void @bar_internal()
 ; CHECK: define internal void @dead_func() {
 ; CHECK-NOT: available_externally {{.*}} @baz()
+; LTO2-NOT: available_externally {{.*}} @baz()
+; LTO2: @llvm.global_ctors =
+; LTO2: define internal void @_GLOBAL__I_a()
+; LTO2: define internal dso_local void @bar() {
+; LTO2: define internal void @bar_internal()
+; LTO2: define internal dso_local void @dead_func() {
+; LTO2-NOT: available_externally {{.*}} @baz()
 
 ; Make sure we didn't internalize @boo, which is reachable via
 ; llvm.global_ctors
 ; CHECK2: define void @boo()
+; LTO2-CHECK2: define dso_local void @boo()
 ; We should have eventually removed @baz since it was internalized and unused
 ; CHECK2-NM-NOT: _baz
 
@@ -80,7 +88,7 @@
 
 ; We can't internalize @dead_func because of the use in the regular LTO
 ; partition.
-; CHECK-NOTDEAD: define void @dead_func()
+; CHECK-NOTDEAD: define dso_local void @dead_func()
 ; We also can't eliminate @baz because it is in the regular LTO partition
 ; and called from @dead_func.
 ; CHECK-NM-NOTDEAD: T _baz

llvm/test/ThinLTO/X86/funcimport2.ll

@@ -7,7 +7,7 @@
 ; RUN:     -r=%t2.bc,_main,plx \
 ; RUN:     -r=%t2.bc,_foo,l
 ; RUN: llvm-dis %t.o.1.3.import.bc -o - | FileCheck %s
-; CHECK: define available_externally void @foo()
+; CHECK: define available_externally dso_local void @foo()
 
 ; We shouldn't do any importing at -O0
 ; rm -f %t.o.1.3.import.bc
@@ -17,7 +17,7 @@
 ; RUN:     -r=%t2.bc,_main,plx \
 ; RUN:     -r=%t2.bc,_foo,l
 ; RUN: llvm-dis %t.o.1.3.import.bc -o - | FileCheck %s --check-prefix=CHECKO0
-; CHECKO0: declare void @foo(...)
+; CHECKO0: declare dso_local void @foo(...)
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.11.0"

llvm/test/ThinLTO/X86/internalize.ll

@@ -1,4 +1,4 @@
-;; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %s -o %t1.bc
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t1.bc
 ; RUN: llvm-lto -thinlto-action=internalize -thinlto-index %t.index.bc %t1.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=REGULAR
 ; RUN: llvm-lto -thinlto-action=internalize -thinlto-index %t.index.bc %t1.bc -o -  --exported-symbol=foo | llvm-dis -o - | FileCheck %s --check-prefix=INTERNALIZE
@@ -7,7 +7,7 @@
 ; RUN:     -r=%t1.bc,_foo,pxl \
 ; RUN:     -r=%t1.bc,_bar,pl \
 ; RUN:     -r=%t1.bc,_linkonce_func,pl
-; RUN: llvm-dis < %t.o.0.2.internalize.bc | FileCheck  %s --check-prefix=INTERNALIZE
+; RUN: llvm-dis < %t.o.0.2.internalize.bc | FileCheck  %s --check-prefix=INTERNALIZE2
 
 
 ; REGULAR: define void @foo
@@ -16,6 +16,9 @@
 ; INTERNALIZE: define void @foo
 ; INTERNALIZE: define internal void @bar
 ; INTERNALIZE: define internal void @linkonce_func()
+; INTERNALIZE2: define dso_local void @foo
+; INTERNALIZE2: define internal dso_local void @bar
+; INTERNALIZE2: define internal dso_local void @linkonce_func()
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.11.0"
@@ -29,4 +32,4 @@ define void @bar() {
 }
 define linkonce void @linkonce_func() {
     ret void
-}
+}

llvm/test/ThinLTO/X86/reference_non_importable.ll

@@ -22,7 +22,7 @@ target triple = "x86_64-apple-macosx10.11.0"
 
 ; We want foo to be imported in the main module!
 ; RUN: llvm-dis < %t.o.1.3.import.bc  | FileCheck  %s --check-prefix=IMPORT
-; IMPORT: define available_externally i8** @foo()
+; IMPORT: define available_externally dso_local i8** @foo()
 define i8 **@foo() {
 	ret i8 **@b
 }

llvm/test/Transforms/LowerTypeTests/import-unsat.ll

@@ -7,6 +7,7 @@
 ; SUMMARY-NEXT:    - Linkage:             0
 ; SUMMARY-NEXT:      NotEligibleToImport: false
 ; SUMMARY-NEXT:      Live:                true
+; SUMMARY-NEXT:      Local:               false
 ; SUMMARY-NEXT:      TypeTests: [ 123 ]
 ; SUMMARY-NEXT: TypeIdMap:
 ; SUMMARY-NEXT:   typeid1:

llvm/test/Transforms/PGOProfile/thinlto_samplepgo_icp2.ll

@@ -22,7 +22,7 @@
 ; RUN: llvm-nm %t3.2 | FileCheck %s --check-prefix=NM
 ; NM: _ZL3barv
 ; RUN: llvm-dis < %t3.2.2.internalize.bc | FileCheck %s --check-prefix=INTERNALIZE
-; INTERNALIZE: define void @_ZL3barv
+; INTERNALIZE: define dso_local void @_ZL3barv
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"

llvm/test/Transforms/WholeProgramDevirt/import-indir.ll

@@ -7,6 +7,7 @@
 ; SUMMARY-NEXT:    - Linkage:             0
 ; SUMMARY-NEXT:      NotEligibleToImport: false
 ; SUMMARY-NEXT:      Live:                true
+; SUMMARY-NEXT:      Local:               false
 ; SUMMARY-NEXT:      TypeTestAssumeVCalls:
 ; SUMMARY-NEXT:        - GUID:            123
 ; SUMMARY-NEXT:          Offset:          0