[nfc][thinlto] Factor common state for computeImportForModule (#65427)

Added a class to hold such common state. The goal is to both reduce the argument list of other utilities used by `computeImportForModule` (which will be brought as members in a subsequent patch), and to make it easy to extend such state later.

Author: mtrofin

llvm/lib/Transforms/IPO/FunctionImport.cpp

@@ -370,6 +370,29 @@ class GlobalsImporter final {
   }
 };
 
+/// Determine the list of imports and exports for each module.
+class ModuleImportsManager final {
+  function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
+      IsPrevailing;
+  const ModuleSummaryIndex &Index;
+  DenseMap<StringRef, FunctionImporter::ExportSetTy> *const ExportLists;
+
+public:
+  ModuleImportsManager(
+      function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
+          IsPrevailing,
+      const ModuleSummaryIndex &Index,
+      DenseMap<StringRef, FunctionImporter::ExportSetTy> *ExportLists = nullptr)
+      : IsPrevailing(IsPrevailing), Index(Index), ExportLists(ExportLists) {}
+
+  /// Given the list of globals defined in a module, compute the list of imports
+  /// as well as the list of "exports", i.e. the list of symbols referenced from
+  /// another module (that may require promotion).
+  void computeImportForModule(const GVSummaryMapTy &DefinedGVSummaries,
+                              StringRef ModName,
+                              FunctionImporter::ImportMapTy &ImportList);
+};
+
 static const char *
 getFailureName(FunctionImporter::ImportFailureReason Reason) {
   switch (Reason) {
@@ -567,20 +590,13 @@ static void computeImportForFunction(
   }
 }
 
-/// Given the list of globals defined in a module, compute the list of imports
-/// as well as the list of "exports", i.e. the list of symbols referenced from
-/// another module (that may require promotion).
-static void ComputeImportForModule(
-    const GVSummaryMapTy &DefinedGVSummaries,
-    function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
-        isPrevailing,
-    const ModuleSummaryIndex &Index, StringRef ModName,
-    FunctionImporter::ImportMapTy &ImportList,
-    DenseMap<StringRef, FunctionImporter::ExportSetTy> *ExportLists = nullptr) {
+void ModuleImportsManager::computeImportForModule(
+    const GVSummaryMapTy &DefinedGVSummaries, StringRef ModName,
+    FunctionImporter::ImportMapTy &ImportList) {
   // Worklist contains the list of function imported in this module, for which
   // we will analyse the callees and may import further down the callgraph.
   SmallVector<EdgeInfo, 128> Worklist;
-  GlobalsImporter GVI(Index, DefinedGVSummaries, isPrevailing, ImportList,
+  GlobalsImporter GVI(Index, DefinedGVSummaries, IsPrevailing, ImportList,
                       ExportLists);
   FunctionImporter::ImportThresholdsTy ImportThresholds;
 
@@ -603,7 +619,7 @@ static void ComputeImportForModule(
       continue;
     LLVM_DEBUG(dbgs() << "Initialize import for " << VI << "\n");
     computeImportForFunction(*FuncSummary, Index, ImportInstrLimit,
-                             DefinedGVSummaries, isPrevailing, Worklist, GVI,
+                             DefinedGVSummaries, IsPrevailing, Worklist, GVI,
                              ImportList, ExportLists, ImportThresholds);
   }
 
@@ -615,7 +631,7 @@ static void ComputeImportForModule(
 
     if (auto *FS = dyn_cast<FunctionSummary>(Summary))
       computeImportForFunction(*FS, Index, Threshold, DefinedGVSummaries,
-                               isPrevailing, Worklist, GVI, ImportList,
+                               IsPrevailing, Worklist, GVI, ImportList,
                                ExportLists, ImportThresholds);
   }
 
@@ -717,13 +733,14 @@ void llvm::ComputeCrossModuleImport(
         isPrevailing,
     DenseMap<StringRef, FunctionImporter::ImportMapTy> &ImportLists,
     DenseMap<StringRef, FunctionImporter::ExportSetTy> &ExportLists) {
+  ModuleImportsManager MIS(isPrevailing, Index, &ExportLists);
   // For each module that has function defined, compute the import/export lists.
   for (const auto &DefinedGVSummaries : ModuleToDefinedGVSummaries) {
     auto &ImportList = ImportLists[DefinedGVSummaries.first];
     LLVM_DEBUG(dbgs() << "Computing import for Module '"
                       << DefinedGVSummaries.first << "'\n");
-    ComputeImportForModule(DefinedGVSummaries.second, isPrevailing, Index,
-                           DefinedGVSummaries.first, ImportList, &ExportLists);
+    MIS.computeImportForModule(DefinedGVSummaries.second,
+                               DefinedGVSummaries.first, ImportList);
   }
 
   // When computing imports we only added the variables and functions being
@@ -839,8 +856,8 @@ static void ComputeCrossModuleImportForModuleForTest(
 
   // Compute the import list for this module.
   LLVM_DEBUG(dbgs() << "Computing import for Module '" << ModulePath << "'\n");
-  ComputeImportForModule(FunctionSummaryMap, isPrevailing, Index, ModulePath,
-                         ImportList);
+  ModuleImportsManager MIS(isPrevailing, Index);
+  MIS.computeImportForModule(FunctionSummaryMap, ModulePath, ImportList);
 
 #ifndef NDEBUG
   dumpImportListForModule(Index, ModulePath, ImportList);