[AnnotationRemarks] Support generating annotation remarks with -O0.

This matches the legacy pass manager behavior. If remarks are not
enabled the pass is effectively a no-op.

(cherry-picked from 770a50b)

Author: fhahn

llvm/include/llvm/Transforms/Scalar/AnnotationRemarks.h

@@ -22,6 +22,7 @@ class Function;
 
 struct AnnotationRemarksPass : public PassInfoMixin<AnnotationRemarksPass> {
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+  static bool isRequired() { return true; }
 };
 } // namespace llvm
 

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -1704,6 +1704,8 @@ ModulePassManager PassBuilder::buildO0DefaultPipeline(OptimizationLevel Level,
   if (LTOPreLink)
     addRequiredLTOPreLinkPasses(MPM);
 
+  MPM.addPass(createModuleToFunctionPassAdaptor(AnnotationRemarksPass()));
+
   return MPM;
 }
 

llvm/test/Other/new-pm-O0-defaults.ll

@@ -58,8 +58,9 @@
 ; CHECK-LTO-NEXT: Running analysis: InnerAnalysisManagerProxy
 ; CHECK-LTO-NEXT: Running pass: LowerTypeTestsPass
 ; CHECK-LTO-NEXT: Running pass: LowerTypeTestsPass
+; CHECK-CORO-NEXT: Running pass: AnnotationRemarksPass
 ; CHECK-LTO-NEXT: Running pass: AnnotationRemarksPass
-; CHECK-LTO-NEXT: Running analysis: TargetLibraryAnalysis 
+; CHECK-LTO-NEXT: Running analysis: TargetLibraryAnalysis
 ; CHECK-NEXT: Running pass: PrintModulePass
 
 ; Make sure we get the IR back out without changes when we print the module.