[LTO] Replace llvm::writeFileAtomically with llvm::writeToOutput API.

[hokein]

This is a patch split out from https://reviews.llvm.org/D153740.

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

433

this is not a completely-none-functional change (in case of error), but I think it should be fine.

[steven_wu]

This is generally fine. I don't see any error that should fall into consumeError condition that won't just error out anyway (like out of disk space, etc.) and I don't see those are special cased for code before switching to writeFileAtomically.

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

419

Nit: Since now we don't care about what kind of error returns, this handleErrors with no error handle does nothing. Just do:

auto Err = llvm::writeToOutput()

[hokein]

Thanks for the review.

[hokein]

committed in 6ecc6b1250b253816703cbca18af432b95fb4089 and dc6c8b8d1e357acf6440824afaf6b6547b34aeeb.

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

 #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"
 #include "llvm/Support/Error.h"
-#include "llvm/Support/FileUtilities.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SHA1.h"
 #include "llvm/Support/SmallVectorMemoryBuffer.h"
 #include "llvm/Support/ThreadPool.h"
 #include "llvm/Support/Threading.h"
 #include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/TargetParser/SubtargetFeature.h"
 #include "llvm/Transforms/IPO/FunctionAttrs.h"
 #include "llvm/Transforms/IPO/FunctionImport.h"
 #include "llvm/Transforms/IPO/Internalize.h"
 #include "llvm/Transforms/IPO/WholeProgramDevirt.h"
 #include "llvm/Transforms/ObjCARC.h"
 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
ErrorOr<std::unique_ptr<MemoryBuffer>> tryLoadingBuffer() {
     return MBOrErr;
   }
 
   // Cache the Produced object file
   void write(const MemoryBuffer &OutputBuffer) {
     if (EntryPath.empty())
       return;
 
-    // Write to a temporary to avoid race condition
-    SmallString<128> TempFilename;
-    SmallString<128> CachePath(EntryPath);
-    llvm::sys::path::remove_filename(CachePath);
-    sys::path::append(TempFilename, CachePath, "Thin-%%%%%%.tmp.o");
-
-    if (auto Err = handleErrors(
-            llvm::writeFileAtomically(TempFilename, EntryPath,
-                                      OutputBuffer.getBuffer()),
-            [](const llvm::AtomicFileWriteError &E) {
-              std::string ErrorMsgBuffer;
-              llvm::raw_string_ostream S(ErrorMsgBuffer);
-              E.log(S);
-
-              if (E.Error ==
-                  llvm::atomic_write_error::failed_to_create_uniq_file) {
-                errs() << "Error: " << ErrorMsgBuffer << "\n";
-                report_fatal_error("ThinLTO: Can't get a temporary file");
-              }
-            })) {
-      // FIXME
-      consumeError(std::move(Err));
-    }
+    if (auto Err = handleErrors(llvm::writeToOutput(
+            EntryPath, [&OutputBuffer](llvm::raw_ostream &OS) -> llvm::Error {
+              OS << OutputBuffer.getBuffer();
+              return llvm::Error::success();
+            })))
+      report_fatal_error(llvm::formatv("ThinLTO: Can't write file {0}: {1}",
+                                       EntryPath,
+                                       toString(std::move(Err)).c_str()));
   }
 };
 
 static std::unique_ptr<MemoryBuffer>
 ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
                      StringMap<lto::InputFile *> &ModuleMap, TargetMachine &TM,
                      const FunctionImporter::ImportMapTy &ImportList,
                      const FunctionImporter::ExportSetTy &ExportList,