[Flang] WIP: Add support for fsave-optimization-record

[kiranchandramohan]

Summary

Add support for saving optimization record. Optimization record
lists the optimizations performed by LLVM. We can hopefully expand
this later to include the MLIR optimizations.

[kiranchandramohan]

Rebase

[tschuett]

It would be nice to get an OptimizationRemarkEmitter into the MLIRContext.

[kiranchandramohan]

Closing in favour of D155452.

flang/lib/Frontend/FrontendActions.cpp

 #include "mlir/Target/LLVMIR/ModuleTranslation.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticFrontend.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/BitcodeWriterPass.h"
+#include "llvm/IR/LLVMRemarkStreamer.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/IRReader/IRReader.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Object/OffloadBinary.h"
 #include "llvm/Passes/PassBuilder.h"
 #include "llvm/Passes/PassPlugin.h"
 #include "llvm/Passes/StandardInstrumentations.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/TargetParser/TargetParser.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
void CodeGenAction::executeAction() {
   // an assert for incompatible data layout when the code-generation happens.
   llvmModule->setTargetTriple(theTriple);
   llvmModule->setDataLayout(tm->createDataLayout());
 
   // Embed offload objects specified with -fembed-offload-object
   if (!ci.getInvocation().getCodeGenOpts().OffloadObjects.empty())
     embedOffloadObjects();
 
+  std::string RemarksFile = "simple.yaml";
+  std::string RemarksPasses;
+  std::string RemarksFormat;
+
+  llvm::Expected<std::unique_ptr<llvm::ToolOutputFile>> RemarksFileOrErr =
+      setupLLVMOptimizationRemarks(llvmModule->getContext(), RemarksFile,
+                                   RemarksPasses, RemarksFormat,
+                                   /*RemarksWithHotness=*/false,
+                                   /*RemarksHotnessThreshold=*/0);
+  if (llvm::Error E = RemarksFileOrErr.takeError()) {
+    llvm::errs() << toString(std::move(E)) << '\n';
+    return;
+  }
+  std::unique_ptr<llvm::ToolOutputFile> ToolRemarksFile =
+      std::move(*RemarksFileOrErr);
+
   // Run LLVM's middle-end (i.e. the optimizer).
   runOptimizationPipeline(ci.isOutputStreamNull() ? *os : ci.getOutputStream());
 
   if (action == BackendActionTy::Backend_EmitLL) {
     llvmModule->print(ci.isOutputStreamNull() ? *os : ci.getOutputStream(),
                       /*AssemblyAnnotationWriter=*/nullptr);
+    if (ToolRemarksFile) {
+      ToolRemarksFile->keep();
+      ToolRemarksFile->os().flush();
+    }
     return;
   }
 
   if (action == BackendActionTy::Backend_EmitBC) {
     // This action has effectively been completed in runOptimizationPipeline.
     return;
   }