ThinLTO: Do not take into account whether a definition has multiple copies when promo...

We currently do not touch a symbol's linkage in the case where a definition
has a single copy. However, this code is effectively unnecessary: either
the definition is not exported, in which case the internalize phase sets
its linkage to internal, or it is exported, in which case we need to promote
linkage to weak. Those two cases are already handled by existing code.

I believe that the only real functional change here is in the case where we
have a single definition which does not prevail (e.g. because the definition
in a native object file prevails). In that case we now lower linkage to
available_externally following the existing code path for that case.

As a result we can remove the isExported function parameter from the
thinLTOResolveWeakForLinkerInIndex function.

Differential Revision: http://reviews.llvm.org/D21883

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274784 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/LTO/LTO.h b/include/llvm/LTO/LTO.h
index 0670af8..5154c00 100644 (file)
--- a/include/llvm/LTO/LTO.h
+++ b/include/llvm/LTO/LTO.h
@@ -60,7 +60,6 @@ void thinLTOResolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
-    function_ref<bool(StringRef, GlobalValue::GUID)> isExported,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
         recordNewLinkage);
 

diff --git a/lib/LTO/LTO.cpp b/lib/LTO/LTO.cpp
index 11bfc94..10226c4 100644 (file)
--- a/lib/LTO/LTO.cpp
+++ b/lib/LTO/LTO.cpp
@@ -45,26 +45,17 @@ static void thinLTOResolveWeakForLinkerGUID(
     DenseSet<GlobalValueSummary *> &GlobalInvolvedWithAlias,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
-    function_ref<bool(StringRef, GlobalValue::GUID)> isExported,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
         recordNewLinkage) {
-  auto HasMultipleCopies = GVSummaryList.size() > 1;
-
   for (auto &S : GVSummaryList) {
     if (GlobalInvolvedWithAlias.count(S.get()))
       continue;
     GlobalValue::LinkageTypes OriginalLinkage = S->linkage();
     if (!GlobalValue::isWeakForLinker(OriginalLinkage))
       continue;
-    // We need to emit only one of these, the first module will keep it,
+    // We need to emit only one of these. The prevailing module will keep it,
     // but turned into a weak, while the others will drop it when possible.
-    if (!HasMultipleCopies) {
-      // Exported Linkonce needs to be promoted to not be discarded.
-      if (GlobalValue::isLinkOnceLinkage(OriginalLinkage) &&
-          isExported(S->modulePath(), GUID))
-        S->setLinkage(GlobalValue::getWeakLinkage(
-            GlobalValue::isLinkOnceODRLinkage(OriginalLinkage)));
-    } else if (isPrevailing(GUID, S.get())) {
+    if (isPrevailing(GUID, S.get())) {
       if (GlobalValue::isLinkOnceLinkage(OriginalLinkage))
         S->setLinkage(GlobalValue::getWeakLinkage(
             GlobalValue::isLinkOnceODRLinkage(OriginalLinkage)));
@@ -89,7 +80,6 @@ void thinLTOResolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
-    function_ref<bool(StringRef, GlobalValue::GUID)> isExported,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
         recordNewLinkage) {
   // We won't optimize the globals that are referenced by an alias for now
@@ -103,7 +93,7 @@ void thinLTOResolveWeakForLinkerInIndex(
 
   for (auto &I : Index)
     thinLTOResolveWeakForLinkerGUID(I.second, I.first, GlobalInvolvedWithAlias,
-                                    isPrevailing, isExported, recordNewLinkage);
+                                    isPrevailing, recordNewLinkage);
 }
 
 static void thinLTOInternalizeAndPromoteGUID(

diff --git a/lib/LTO/ThinLTOCodeGenerator.cpp b/lib/LTO/ThinLTOCodeGenerator.cpp
index 5c97e4d..2aa1e3f 100644 (file)
--- a/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -393,8 +393,6 @@ ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
 /// copies when possible).
 static void resolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
-    const StringMap<FunctionImporter::ExportSetTy> &ExportLists,
-    const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
     StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>>
         &ResolvedODR) {
 
@@ -409,21 +407,13 @@ static void resolveWeakForLinkerInIndex(
     return Prevailing->second == S;
   };
 
-  auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
-    const auto &ExportList = ExportLists.find(ModuleIdentifier);
-    return (ExportList != ExportLists.end() &&
-            ExportList->second.count(GUID)) ||
-           GUIDPreservedSymbols.count(GUID);
-  };
-
   auto recordNewLinkage = [&](StringRef ModuleIdentifier,
                               GlobalValue::GUID GUID,
                               GlobalValue::LinkageTypes NewLinkage) {
     ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
   };
 
-  thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, isExported,
-                                     recordNewLinkage);
+  thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, recordNewLinkage);
 }
 
 // Initialize the TargetMachine builder for a given Triple
@@ -537,14 +527,9 @@ void ThinLTOCodeGenerator::promote(Module &TheModule,
   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
                            ExportLists);
 
-  // Convert the preserved symbols set from string to GUID
-  auto GUIDPreservedSymbols =
-  computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
-
   // Resolve LinkOnce/Weak symbols.
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
-  resolveWeakForLinkerInIndex(Index, ExportLists, GUIDPreservedSymbols,
-                              ResolvedODR);
+  resolveWeakForLinkerInIndex(Index, ResolvedODR);
 
   thinLTOResolveWeakForLinkerModule(
       TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
@@ -750,8 +735,7 @@ void ThinLTOCodeGenerator::run() {
 
   // Resolve LinkOnce/Weak symbols, this has to be computed early because it
   // impacts the caching.
-  resolveWeakForLinkerInIndex(*Index, ExportLists, GUIDPreservedSymbols,
-                              ResolvedODR);
+  resolveWeakForLinkerInIndex(*Index, ResolvedODR);
 
   auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
     const auto &ExportList = ExportLists.find(ModuleIdentifier);

diff --git a/test/ThinLTO/X86/alias_import.ll b/test/ThinLTO/X86/alias_import.ll
index 198b44c..f708ead 100644 (file)
--- a/test/ThinLTO/X86/alias_import.ll
+++ b/test/ThinLTO/X86/alias_import.ll
@@ -11,36 +11,36 @@
 ; available_externally, i.e linkOnceODR. (FIXME this limitation could be lifted)
 ; PROMOTE-DAG: @globalfuncAlias = alias void (...), bitcast (void ()* @globalfunc to void (...)*)
 ; PROMOTE-DAG: @globalfuncWeakAlias = weak alias void (...), bitcast (void ()* @globalfunc to void (...)*)
-; PROMOTE-DAG: @globalfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+; PROMOTE-DAG: @globalfuncLinkonceAlias = weak alias void (...), bitcast (void ()* @globalfunc to void (...)*)
 ; PROMOTE-DAG: @globalfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @globalfunc to void (...)*)
-; PROMOTE-DAG: @globalfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+; PROMOTE-DAG: @globalfuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @globalfunc to void (...)*)
 ; PROMOTE-DAG: @internalfuncAlias = alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
 ; PROMOTE-DAG: @internalfuncWeakAlias = weak alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
-; PROMOTE-DAG: @internalfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
+; PROMOTE-DAG: @internalfuncLinkonceAlias = weak alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
 ; PROMOTE-DAG: @internalfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
-; PROMOTE-DAG: @internalfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
+; PROMOTE-DAG: @internalfuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
 ; PROMOTE-DAG: @linkoncefuncAlias = alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
 ; PROMOTE-DAG: @linkoncefuncWeakAlias = weak alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
-; PROMOTE-DAG: @linkoncefuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+; PROMOTE-DAG: @linkoncefuncLinkonceAlias = weak alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
 ; PROMOTE-DAG: @linkoncefuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
-; PROMOTE-DAG: @linkoncefuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+; PROMOTE-DAG: @linkoncefuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
 ; PROMOTE-DAG: @weakfuncAlias = alias void (...), bitcast (void ()* @weakfunc to void (...)*)
 ; PROMOTE-DAG: @weakfuncWeakAlias = weak alias void (...), bitcast (void ()* @weakfunc to void (...)*)
-; PROMOTE-DAG: @weakfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+; PROMOTE-DAG: @weakfuncLinkonceAlias = weak alias void (...), bitcast (void ()* @weakfunc to void (...)*)
 ; PROMOTE-DAG: @weakfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @weakfunc to void (...)*)
-; PROMOTE-DAG: @weakfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+; PROMOTE-DAG: @weakfuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @weakfunc to void (...)*)
 ; PROMOTE-DAG: @weakODRfuncAlias = alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
 ; PROMOTE-DAG: @weakODRfuncWeakAlias = weak alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
-; PROMOTE-DAG: @weakODRfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+; PROMOTE-DAG: @weakODRfuncLinkonceAlias = weak alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
 ; PROMOTE-DAG: @weakODRfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
-; PROMOTE-DAG: @weakODRfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+; PROMOTE-DAG: @weakODRfuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
 
 ; Only alias to LinkonceODR aliasee can be imported
 ; PROMOTE-DAG: @linkonceODRfuncAlias = alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
 ; PROMOTE-DAG: @linkonceODRfuncWeakAlias = weak alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
 ; PROMOTE-DAG: @linkonceODRfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
 ; Amongst these that are imported, check that we promote only linkonce->weak
-; PROMOTE-DAG: @linkonceODRfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+; PROMOTE-DAG: @linkonceODRfuncLinkonceAlias = weak alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
 ; PROMOTE-DAG: @linkonceODRfuncLinkonceODRAlias = weak_odr alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
 
 ; These will be imported, check the linkage/renaming after promotion

diff --git a/test/ThinLTO/X86/weak_resolution.ll b/test/ThinLTO/X86/weak_resolution.ll
index bf3b3b8..5c23a36 100644 (file)
--- a/test/ThinLTO/X86/weak_resolution.ll
+++ b/test/ThinLTO/X86/weak_resolution.ll
@@ -67,7 +67,7 @@ entry:
   ret void
 }
 
-; MOD1: define linkonce_odr void @linkonceodrfuncInSingleModule()
+; MOD1: define weak_odr void @linkonceodrfuncInSingleModule()
 ; MOD1-INT: define internal void @linkonceodrfuncInSingleModule()
 ; EXPORTED: define weak_odr void @linkonceodrfuncInSingleModule()
 define linkonce_odr void @linkonceodrfuncInSingleModule() #0 {