[ThinLTO]Mark referencers of local ifunc not eligible for import

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

@@ -95,9 +95,12 @@ extern cl::opt<unsigned> MaxNumVTableAnnotations;
 // global vars at all. When importing function we aren't interested if any
 // instruction in it takes an address of any basic block, because instruction
 // can only take an address of basic block located in the same function.
+// Set `RefLocalLinkageIFunc` to true if the analyzed value references a
+// local-linkage ifunc.
 static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser,
                          SetVector<ValueInfo, std::vector<ValueInfo>> &RefEdges,
-                         SmallPtrSet<const User *, 8> &Visited) {
+                         SmallPtrSet<const User *, 8> &Visited,
+                         bool &RefLocalLinkageIFunc) {
   bool HasBlockAddress = false;
   SmallVector<const User *, 32> Worklist;
   if (Visited.insert(CurUser).second)
@@ -119,8 +122,18 @@ static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser,
         // We have a reference to a global value. This should be added to
         // the reference set unless it is a callee. Callees are handled
         // specially by WriteFunction and are added to a separate list.
-        if (!(CB && CB->isCallee(&OI)))
+        if (!(CB && CB->isCallee(&OI))) {
+          // If an ifunc has local linkage, do not add it into ref edges, and
+          // sets `RefLocalLinkageIFunc` to true. The referencer is not eligible
+          // for import. An ifunc doesn't have summary and ThinLTO cannot
+          // promote it; importing the referencer may cause linkage errors.
+          if (auto *GI = dyn_cast_if_present<GlobalIFunc>(GV);
+              GI && GI->hasLocalLinkage()) {
+            RefLocalLinkageIFunc = true;
+            continue;
+          }
           RefEdges.insert(Index.getOrInsertValueInfo(GV));
+        }
         continue;
       }
       if (Visited.insert(Operand).second)
@@ -313,7 +326,8 @@ static void computeFunctionSummary(
 
   // Add personality function, prefix data and prologue data to function's ref
   // list.
-  findRefEdges(Index, &F, RefEdges, Visited);
+  bool HasLocalIFuncCallOrRef = false;
+  findRefEdges(Index, &F, RefEdges, Visited, HasLocalIFuncCallOrRef);
   std::vector<const Instruction *> NonVolatileLoads;
   std::vector<const Instruction *> NonVolatileStores;
 
@@ -326,7 +340,6 @@ static void computeFunctionSummary(
 
   bool HasInlineAsmMaybeReferencingInternal = false;
   bool HasIndirBranchToBlockAddress = false;
-  bool HasIFuncCall = false;
   bool HasUnknownCall = false;
   bool MayThrow = false;
   for (const BasicBlock &BB : F) {
@@ -372,11 +385,11 @@ static void computeFunctionSummary(
             // of calling it we should add GV to RefEdges directly.
             RefEdges.insert(Index.getOrInsertValueInfo(GV));
           else if (auto *U = dyn_cast<User>(Stored))
-            findRefEdges(Index, U, RefEdges, Visited);
+            findRefEdges(Index, U, RefEdges, Visited, HasLocalIFuncCallOrRef);
           continue;
         }
       }
-      findRefEdges(Index, &I, RefEdges, Visited);
+      findRefEdges(Index, &I, RefEdges, Visited, HasLocalIFuncCallOrRef);
       const auto *CB = dyn_cast<CallBase>(&I);
       if (!CB) {
         if (I.mayThrow())
@@ -450,7 +463,7 @@ static void computeFunctionSummary(
         // Non-local ifunc is not cloned and does not have the issue.
         if (auto *GI = dyn_cast_if_present<GlobalIFunc>(CalledValue))
           if (GI->hasLocalLinkage())
-            HasIFuncCall = true;
+            HasLocalIFuncCallOrRef = true;
         // Skip inline assembly calls.
         if (CI && CI->isInlineAsm())
           continue;
@@ -555,7 +568,7 @@ static void computeFunctionSummary(
                            SmallPtrSet<const User *, 8> &Cache) {
       for (const auto *I : Instrs) {
         Cache.erase(I);
-        findRefEdges(Index, I, Edges, Cache);
+        findRefEdges(Index, I, Edges, Cache, HasLocalIFuncCallOrRef);
       }
     };
 
@@ -631,9 +644,9 @@ static void computeFunctionSummary(
 #endif
 
   bool NonRenamableLocal = isNonRenamableLocal(F);
-  bool NotEligibleForImport = NonRenamableLocal ||
-                              HasInlineAsmMaybeReferencingInternal ||
-                              HasIndirBranchToBlockAddress || HasIFuncCall;
+  bool NotEligibleForImport =
+      NonRenamableLocal || HasInlineAsmMaybeReferencingInternal ||
+      HasIndirBranchToBlockAddress || HasLocalIFuncCallOrRef;
   GlobalValueSummary::GVFlags Flags(
       F.getLinkage(), F.getVisibility(), NotEligibleForImport,
       /* Live = */ false, F.isDSOLocal(), F.canBeOmittedFromSymbolTable(),
@@ -787,7 +800,10 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
                                    SmallVectorImpl<MDNode *> &Types) {
   SetVector<ValueInfo, std::vector<ValueInfo>> RefEdges;
   SmallPtrSet<const User *, 8> Visited;
-  bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited);
+  bool RefLocalIFunc = false;
+  bool HasBlockAddress =
+      findRefEdges(Index, &V, RefEdges, Visited, RefLocalIFunc);
+  const bool NotEligibleForImport = (HasBlockAddress || RefLocalIFunc);
   bool NonRenamableLocal = isNonRenamableLocal(V);
   GlobalValueSummary::GVFlags Flags(
       V.getLinkage(), V.getVisibility(), NonRenamableLocal,
@@ -821,7 +837,7 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
                                                          RefEdges.takeVector());
   if (NonRenamableLocal)
     CantBePromoted.insert(V.getGUID());
-  if (HasBlockAddress)
+  if (NotEligibleForImport)
     GVarSummary->setNotEligibleToImport();
   if (!VTableFuncs.empty())
     GVarSummary->setVTableFuncs(VTableFuncs);

llvm/test/ThinLTO/X86/ref-ifunc.ll

@@ -0,0 +1,52 @@
+; RUN: opt -module-summary %s -o %t.bc
+
+; RUN: llvm-dis %t.bc -o - | FileCheck %s
+
+; Tests that var and caller are not eligible to import and they don't have refs to ifunc 'callee'
+
+; CHECK: gv: (name: "var", summaries: (variable: ({{.*}}, flags: ({{.*}}notEligibleToImport: 1
+; CHECK-NOT: refs
+; CHECK-SAME: guid = 7919382516565939378
+
+; CHECK: gv: (name: "caller", summaries: (function: ({{.*}}, flags: ({{.*}}notEligibleToImport: 1
+; CHECK-NOT: refs
+; CHECK-SAME: guid = 16677772384402303968
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@__cpu_model = external global { i32, i32, i32, [1 x i32] }
+
+@callee = internal ifunc void(), ptr @callee.resolver
+
+@var = constant { [1 x ptr] } { [1 x ptr] [ptr @callee]}
+
+define void @dispatch(ptr %func) {
+    tail call void %func()
+    ret void
+}
+
+define void @caller() {
+  tail call void @dispatch(ptr @callee)
+  ret void
+}
+
+define internal ptr @callee.resolver() {
+resolver_entry:
+  tail call void @__cpu_indicator_init()
+  %0 = load i32, ptr getelementptr inbounds ({ i32, i32, i32, [1 x i32] }, ptr @__cpu_model, i64 0, i32 3, i64 0)
+  %1 = and i32 %0, 1024
+  %.not = icmp eq i32 %1, 0
+  %func_sel = select i1 %.not, ptr @callee.default.1, ptr @callee.avx2.0
+  ret ptr %func_sel
+}
+
+define internal void @callee.default.1(i32 %a) {
+  ret void
+}
+
+define internal void @callee.avx2.0(i32 %a) {
+  ret void
+}
+
+declare void @__cpu_indicator_init()