[ThinLTO] Add Visibility bits to GlobalValueSummary::GVFlags

Imported functions and variable get the visibility from the module supplying the
definition.  However, non-imported definitions do not get the visibility from
(ELF) the most constraining visibility among all modules (Mach-O) the visibility
of the prevailing definition.

This patch

* adds visibility bits to GlobalValueSummary::GVFlags
* computes the result visibility and propagates it to all definitions

Protected/hidden can imply dso_local which can enable some optimizations (this
is stronger than GVFlags::DSOLocal because the implied dso_local can be
leveraged for ELF -shared while default visibility dso_local has to be cleared
for ELF -shared).

Note: we don't have summaries for declarations, so for ELF if a declaration has
the most constraining visibility, the result visibility may not be that one.

Differential Revision: https://reviews.llvm.org/D92900

1 files changed, 18 insertions, 14 deletions

diff --git a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
index 5f7746e..00fc416 100644
--- a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -459,9 +459,10 @@ static void computeFunctionSummary(
   bool NonRenamableLocal = isNonRenamableLocal(F);
   bool NotEligibleForImport =
       NonRenamableLocal || HasInlineAsmMaybeReferencingInternal;
-  GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
-                                    /* Live = */ false, F.isDSOLocal(),
-                                    F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr());
+  GlobalValueSummary::GVFlags Flags(
+      F.getLinkage(), F.getVisibility(), NotEligibleForImport,
+      /* Live = */ false, F.isDSOLocal(),
+      F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr());
   FunctionSummary::FFlags FunFlags{
       F.hasFnAttribute(Attribute::ReadNone),
       F.hasFnAttribute(Attribute::ReadOnly),
@@ -580,9 +581,10 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
   SmallPtrSet<const User *, 8> Visited;
   bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited);
   bool NonRenamableLocal = isNonRenamableLocal(V);
-  GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false, V.isDSOLocal(),
-                                    V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr());
+  GlobalValueSummary::GVFlags Flags(
+      V.getLinkage(), V.getVisibility(), NonRenamableLocal,
+      /* Live = */ false, V.isDSOLocal(),
+      V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr());
 
   VTableFuncList VTableFuncs;
   // If splitting is not enabled, then we compute the summary information
@@ -622,9 +624,10 @@ static void
 computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
                     DenseSet<GlobalValue::GUID> &CantBePromoted) {
   bool NonRenamableLocal = isNonRenamableLocal(A);
-  GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false, A.isDSOLocal(),
-                                    A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr());
+  GlobalValueSummary::GVFlags Flags(
+      A.getLinkage(), A.getVisibility(), NonRenamableLocal,
+      /* Live = */ false, A.isDSOLocal(),
+      A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr());
   auto AS = std::make_unique<AliasSummary>(Flags);
   auto *Aliasee = A.getBaseObject();
   auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID());
@@ -697,11 +700,12 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
           if (!GV)
             return;
           assert(GV->isDeclaration() && "Def in module asm already has definition");
-          GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
-                                              /* NotEligibleToImport = */ true,
-                                              /* Live = */ true,
-                                              /* Local */ GV->isDSOLocal(),
-                                              GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr());
+          GlobalValueSummary::GVFlags GVFlags(
+              GlobalValue::InternalLinkage, GlobalValue::DefaultVisibility,
+              /* NotEligibleToImport = */ true,
+              /* Live = */ true,
+              /* Local */ GV->isDSOLocal(),
+              GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr());
           CantBePromoted.insert(GV->getGUID());
           // Create the appropriate summary type.
           if (Function *F = dyn_cast<Function>(GV)) {