[lld][MachO][NFC] Create a support file for LTO.

[Roger]

Summary

I'm making this change because I'd like to use saveTempBitcode in other places than just the ThinLTOCodeGenerator.cpp file.

[Roger]

Generalize error message.

llvm/include/llvm/LTO/Support.h

+//===--------------------- Support.h ----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file contains helper functions related to link-time optimization (LTO).
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/Module.h"
+
+namespace llvm {
+
+void saveTempBitcode(const Module &TheModule, StringRef TempDir, unsigned Count,
+                     StringRef Suffix);
+
+} // namespace llvm

llvm/lib/LTO/CMakeLists.txt

 add_llvm_component_library(LLVMLTO
   LTO.cpp
   LTOBackend.cpp
   LTOModule.cpp
   LTOCodeGenerator.cpp
   SummaryBasedOptimizations.cpp
+  Support.cpp
   UpdateCompilerUsed.cpp
   ThinLTOCodeGenerator.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/LTO
   DEPENDS
   intrinsics_gen
   llvm_vcsrevision_h

llvm/lib/LTO/Support.cpp

+//===-Support.cpp - LLVM Link Time Optimizer ------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///  \file
+///
+/// This file contains helper functions related to link-time optimization (LTO).
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/Support.h"
+
+#include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/Support/FileSystem.h"
+
+namespace llvm {
+
+// Simple helper to save temporary files for debug.
+void saveTempBitcode(const Module &TheModule, StringRef TempDir, unsigned Count,
+                     StringRef Suffix) {
+  if (TempDir.empty())
+    return;
+  // User asked to save temps, let dump the bitcode file after import.
+  std::string SaveTempPath = (TempDir + llvm::Twine(Count) + Suffix).str();
+  std::error_code EC;
+  raw_fd_ostream OS(SaveTempPath, EC, sys::fs::OF_None);
+  if (EC)
+    report_fatal_error(Twine("Failed to open ") + SaveTempPath +
+                       " to save bitcode\n");
+  WriteBitcodeToFile(TheModule, OS, /* ShouldPreserveUseListOrder */ true);
+}
+
+} // namespace llvm

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
 #include "llvm/Bitcode/BitcodeWriterPass.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
-#include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/LLVMRemarkStreamer.h"
+#include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/PassTimingInfo.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/IRReader/IRReader.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/LTO/SummaryBasedOptimizations.h"
+#include "llvm/LTO/Support.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Object/IRObjectFile.h"
 #include "llvm/Passes/PassBuilder.h"
 #include "llvm/Passes/StandardInstrumentations.h"
 #include "llvm/Remarks/HotnessThresholdParser.h"
 #include "llvm/Support/CachePruning.h"
 #include "llvm/Support/Debug.h"

 namespace {
 
 // Default to using all available threads in the system, but using only one
 // thred per core, as indicated by the usage of
 // heavyweight_hardware_concurrency() below.
 static cl::opt<int> ThreadCount("threads", cl::init(0));
 
 // Simple helper to save temporary files for debug.
-static void saveTempBitcode(const Module &TheModule, StringRef TempDir,
-                            unsigned count, StringRef Suffix) {
-  if (TempDir.empty())
-    return;
-  // User asked to save temps, let dump the bitcode file after import.
-  std::string SaveTempPath = (TempDir + llvm::Twine(count) + Suffix).str();
-  std::error_code EC;
-  raw_fd_ostream OS(SaveTempPath, EC, sys::fs::OF_None);
-  if (EC)
-    report_fatal_error(Twine("Failed to open ") + SaveTempPath +
-                       " to save optimized bitcode\n");
-  WriteBitcodeToFile(TheModule, OS, /* ShouldPreserveUseListOrder */ true);
-}
-
 static const GlobalValueSummary *
 getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) {
   // If there is any strong definition anywhere, get it.
   auto StrongDefForLinker = llvm::find_if(
       GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
         auto Linkage = Summary->linkage();
         return !GlobalValue::isAvailableExternallyLinkage(Linkage) &&
                !GlobalValue::isWeakForLinker(Linkage);