[LegacyPM] Remove ThinLTO bitcode writer legacy pass

Using the legacy PM for the optimization pipeline is deprecated and in
the process of being removed. This is a small step in that direction.

For an example of migrating to the new PM:
853b57f

llvm/include/llvm/Transforms/IPO.h

@@ -240,10 +240,6 @@ ModulePass *createCrossDSOCFIPass();
 /// devirtualization and control-flow integrity.
 ModulePass *createGlobalSplitPass();
 
-/// Write ThinLTO-ready bitcode to Str.
-ModulePass *createWriteThinLTOBitcodePass(raw_ostream &Str,
-                                          raw_ostream *ThinLinkOS = nullptr);
-
 } // End llvm namespace
 
 #endif

llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp

@@ -546,54 +546,8 @@ void writeThinLTOBitcode(raw_ostream &OS, raw_ostream *ThinLinkOS,
     writeThinLinkBitcodeToFile(M, *ThinLinkOS, *Index, ModHash);
 }
 
-class WriteThinLTOBitcode : public ModulePass {
-  raw_ostream &OS; // raw_ostream to print on
-  // The output stream on which to emit a minimized module for use
-  // just in the thin link, if requested.
-  raw_ostream *ThinLinkOS = nullptr;
-
-public:
-  static char ID; // Pass identification, replacement for typeid
-  WriteThinLTOBitcode() : ModulePass(ID), OS(dbgs()) {
-    initializeWriteThinLTOBitcodePass(*PassRegistry::getPassRegistry());
-  }
-
-  explicit WriteThinLTOBitcode(raw_ostream &o, raw_ostream *ThinLinkOS)
-      : ModulePass(ID), OS(o), ThinLinkOS(ThinLinkOS) {
-    initializeWriteThinLTOBitcodePass(*PassRegistry::getPassRegistry());
-  }
-
-  StringRef getPassName() const override { return "ThinLTO Bitcode Writer"; }
-
-  bool runOnModule(Module &M) override {
-    const ModuleSummaryIndex *Index =
-        &(getAnalysis<ModuleSummaryIndexWrapperPass>().getIndex());
-    writeThinLTOBitcode(OS, ThinLinkOS, LegacyAARGetter(*this), M, Index);
-    return true;
-  }
-  void getAnalysisUsage(AnalysisUsage &AU) const override {
-    AU.setPreservesAll();
-    AU.addRequired<AssumptionCacheTracker>();
-    AU.addRequired<ModuleSummaryIndexWrapperPass>();
-    AU.addRequired<TargetLibraryInfoWrapperPass>();
-  }
-};
 } // anonymous namespace
 
-char WriteThinLTOBitcode::ID = 0;
-INITIALIZE_PASS_BEGIN(WriteThinLTOBitcode, "write-thinlto-bitcode",
-                      "Write ThinLTO Bitcode", false, true)
-INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
-INITIALIZE_PASS_DEPENDENCY(ModuleSummaryIndexWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
-INITIALIZE_PASS_END(WriteThinLTOBitcode, "write-thinlto-bitcode",
-                    "Write ThinLTO Bitcode", false, true)
-
-ModulePass *llvm::createWriteThinLTOBitcodePass(raw_ostream &Str,
-                                                raw_ostream *ThinLinkOS) {
-  return new WriteThinLTOBitcode(Str, ThinLinkOS);
-}
-
 PreservedAnalyses
 llvm::ThinLTOBitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
   FunctionAnalysisManager &FAM =

llvm/tools/opt/opt.cpp

@@ -970,8 +970,8 @@ int main(int argc, char **argv) {
         report_fatal_error("Text output is incompatible with -module-hash");
       Passes.add(createPrintModulePass(*OS, "", PreserveAssemblyUseListOrder));
     } else if (OutputThinLTOBC)
-      Passes.add(createWriteThinLTOBitcodePass(
-          *OS, ThinLinkOut ? &ThinLinkOut->os() : nullptr));
+      report_fatal_error(
+          "Use the new pass manager for printing ThinLTO bitcode");
     else
       Passes.add(createBitcodeWriterPass(*OS, PreserveBitcodeUseListOrder,
                                          EmitSummaryIndex, EmitModuleHash));