[ThinLTO] Add support for optimization remarks to thinBackend

[tejohnson]

Summary

Support was added to the regular LTO backend, but not thinBackend.
This patch adds that support.

[pcc]

LGTM

Maybe consider making finalizeOptimizationRemarks return an llvm::Error so that we can return from thinBackend with return finalizeOptimizationRemarks(...).

[tejohnson]

In D46376#1086811, @pcc wrote:

LGTM

Maybe consider making finalizeOptimizationRemarks return an llvm::Error so that we can return from thinBackend with return finalizeOptimizationRemarks(...).

Good idea, done.

[tejohnson]

Address comments

lib/LTO/LTOBackend.cpp

Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
                        const GVSummaryMapTy &DefinedGlobals,
                        MapVector<StringRef, BitcodeModule> &ModuleMap) {
   Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
   if (!TOrErr)
     return TOrErr.takeError();
 
   std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod);
 
+  // Setup optimization remarks.
+  auto DiagFileOrErr = lto::setupOptimizationRemarks(
+      Mod.getContext(), Conf.RemarksFilename, Conf.RemarksWithHotness, Task);
+  if (!DiagFileOrErr)
+    return DiagFileOrErr.takeError();
+  auto DiagnosticOutputFile = std::move(*DiagFileOrErr);
+
   if (Conf.CodeGenOnly) {
     codegen(Conf, TM.get(), AddStream, Task, Mod);
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
   }
 
-  if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
+  if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod)) {
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
+  }
 
   renameModuleForThinLTO(Mod, CombinedIndex);
 
   dropDeadSymbols(Mod, DefinedGlobals, CombinedIndex);
 
   thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
 
-  if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
+  if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod)) {
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
+  }
 
   if (!DefinedGlobals.empty())
     thinLTOInternalizeModule(Mod, DefinedGlobals);
 
   if (Conf.PostInternalizeModuleHook &&
-      !Conf.PostInternalizeModuleHook(Task, Mod))
+      !Conf.PostInternalizeModuleHook(Task, Mod)) {
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
+  }
 
   auto ModuleLoader = [&](StringRef Identifier) {
     assert(Mod.getContext().isODRUniquingDebugTypes() &&
            "ODR Type uniquing should be enabled on the context");
     auto I = ModuleMap.find(Identifier);
     assert(I != ModuleMap.end());
     return I->second.getLazyModule(Mod.getContext(),
                                    /*ShouldLazyLoadMetadata=*/true,
                                    /*IsImporting*/ true);
   };
 
   FunctionImporter Importer(CombinedIndex, ModuleLoader);
   if (Error Err = Importer.importFunctions(Mod, ImportList).takeError())
     return Err;
 
-  if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
+  if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod)) {
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
+  }
 
   if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true,
-           /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex))
+           /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex)) {
+    finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
     return Error::success();
+  }
 
   codegen(Conf, TM.get(), AddStream, Task, Mod);
+  finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
   return Error::success();
 }

test/LTO/Resolution/X86/diagnostic-handler-remarks.ll

-; RUN: llvm-as < %s >%t.bc
+; Test of LTO with opt remarks YAML output.
 
+; First try with Regular LTO
+; RUN: llvm-as < %s >%t.bc
 ; RUN: rm -f %t.yaml
 ; RUN: llvm-lto2 run -pass-remarks-output=%t.yaml \
 ; RUN:           -r %t.bc,tinkywinky,p \
 ; RUN:           -r %t.bc,patatino,px \
 ; RUN:           -r %t.bc,main,px -o %t.o %t.bc
 ; RUN: cat %t.yaml | FileCheck %s -check-prefix=YAML
 
+; Try again with ThinLTO
+; RUN: opt -module-summary %s -o %t.bc
+; RUN: rm -f %t.thin.1.yaml
+; RUN: llvm-lto2 run -pass-remarks-output=%t \
+; RUN:           -r %t.bc,tinkywinky,p \
+; RUN:           -r %t.bc,patatino,px \
+; RUN:           -r %t.bc,main,px -o %t.o %t.bc
+; RUN: cat %t.thin.1.yaml | FileCheck %s -check-prefix=YAML
+
 ; YAML:      --- !Passed
 ; YAML-NEXT: Pass:            inline
 ; YAML-NEXT: Name:            Inlined
 ; YAML-NEXT: Function:        main
 ; YAML-NEXT: Args:
 ; YAML-NEXT:   - Callee:          tinkywinky
 ; YAML-NEXT:   - String:          ' inlined into '
 ; YAML-NEXT:   - Caller:          main