[InstrProf][Correlate] Improve error messages

[ellis]

Summary

Improve the error messages when using llvm-profdata to correlate profiles with debug info.

[ellis]

Tests are in the next diff D118181

[kyulee]

This looks reasonable by sharing a common error message concatenated by the detailed reasons as needed instead of populating all the error cases.
Unless this violates coding convention with regard to error messages, it looks good to me. I'm approving it but want to hear other reviewers' opinions.

[phosek]

LGTM

llvm/include/llvm/ProfileData/InstrProf.h

enum class instrprof_error {
   unsupported_version,
   unsupported_hash_type,
   too_large,
   truncated,
   malformed,
   missing_debug_info_for_correlation,
   unexpected_debug_info_for_correlation,
   unable_to_correlate_profile,
-  unsupported_debug_format,
   unknown_function,
   invalid_prof,
   hash_mismatch,
   count_mismatch,
   counter_overflow,
   value_site_count_mismatch,
   compress_failed,
   uncompress_failed,

llvm/lib/ProfileData/InstrProf.cpp

case instrprof_error::missing_debug_info_for_correlation:
     OS << "debug info for correlation is required";
     break;
   case instrprof_error::unexpected_debug_info_for_correlation:
     OS << "debug info for correlation is not necessary";
     break;
   case instrprof_error::unable_to_correlate_profile:
     OS << "unable to correlate profile";
     break;
-  case instrprof_error::unsupported_debug_format:
-    OS << "unsupported debug info format (only DWARF is supported)";
-    break;
   case instrprof_error::invalid_prof:
     OS << "invalid profile created. Please file a bug "
           "at: " BUG_REPORT_URL
           " and include the profraw files that caused this error.";
     break;
   case instrprof_error::unknown_function:
     OS << "no profile data available for function";
     break;

llvm/lib/ProfileData/InstrProfCorrelator.cpp

 
 /// Get the __llvm_prf_cnts section.
 Expected<object::SectionRef> getCountersSection(const object::ObjectFile &Obj) {
   for (auto &Section : Obj.sections())
     if (auto SectionName = Section.getName())
       if (SectionName.get() == INSTR_PROF_CNTS_SECT_NAME)
         return Section;
   return make_error<InstrProfError>(
-      instrprof_error::unable_to_correlate_profile);
+      instrprof_error::unable_to_correlate_profile,
+      "could not find counter section (" INSTR_PROF_CNTS_SECT_NAME ")");
 }
 
 const char *InstrProfCorrelator::FunctionNameAttributeName = "Function Name";
 const char *InstrProfCorrelator::CFGHashAttributeName = "CFG Hash";
 const char *InstrProfCorrelator::NumCountersAttributeName = "Num Counters";
 
 llvm::Expected<std::unique_ptr<InstrProfCorrelator::Context>>
 InstrProfCorrelator::Context::get(std::unique_ptr<MemoryBuffer> Buffer,
InstrProfCorrelator::get(StringRef DebugInfoFilename) {
   auto DsymObjectsOrErr =
       object::MachOObjectFile::findDsymObjectMembers(DebugInfoFilename);
   if (auto Err = DsymObjectsOrErr.takeError())
     return std::move(Err);
   if (!DsymObjectsOrErr->empty()) {
     // TODO: Enable profile correlation when there are multiple objects in a
     // dSYM bundle.
     if (DsymObjectsOrErr->size() > 1)
-      return createStringError(
-          std::error_code(),
-          "Profile correlation using multiple objects is not yet supported");
+      return make_error<InstrProfError>(
+          instrprof_error::unable_to_correlate_profile,
+          "using multiple objects is not yet supported");
     DebugInfoFilename = *DsymObjectsOrErr->begin();
   }
   auto BufferOrErr =
       errorOrToExpected(MemoryBuffer::getFile(DebugInfoFilename));
   if (auto Err = BufferOrErr.takeError())
     return std::move(Err);
 
   return get(std::move(*BufferOrErr));
if (auto Err = CtxOrErr.takeError())
       return std::move(Err);
     auto T = Obj->makeTriple();
     if (T.isArch64Bit())
       return InstrProfCorrelatorImpl<uint64_t>::get(std::move(*CtxOrErr), *Obj);
     if (T.isArch32Bit())
       return InstrProfCorrelatorImpl<uint32_t>::get(std::move(*CtxOrErr), *Obj);
   }
   return make_error<InstrProfError>(
-      instrprof_error::unable_to_correlate_profile);
+      instrprof_error::unable_to_correlate_profile, "not an object file");
 }
 
 namespace llvm {
 
 template <>
 InstrProfCorrelatorImpl<uint32_t>::InstrProfCorrelatorImpl(
     std::unique_ptr<InstrProfCorrelator::Context> Ctx)
     : InstrProfCorrelatorImpl(InstrProfCorrelatorKind::CK_32Bit,

 InstrProfCorrelatorImpl<IntPtrT>::get(
     std::unique_ptr<InstrProfCorrelator::Context> Ctx,
     const object::ObjectFile &Obj) {
   if (Obj.isELF() || Obj.isMachO()) {
     auto DICtx = DWARFContext::create(Obj);
     return std::make_unique<DwarfInstrProfCorrelator<IntPtrT>>(std::move(DICtx),
                                                                std::move(Ctx));
   }
-  return make_error<InstrProfError>(instrprof_error::unsupported_debug_format);
+  return make_error<InstrProfError>(
+      instrprof_error::unable_to_correlate_profile,
+      "unsupported debug info format (only DWARF is supported)");
 }
 
 template <class IntPtrT>
 Error InstrProfCorrelatorImpl<IntPtrT>::correlateProfileData() {
   assert(Data.empty() && CompressedNames.empty() && Names.empty());
   correlateProfileDataImpl();
+  if (Data.empty() || Names.empty())
+    return make_error<InstrProfError>(
+        instrprof_error::unable_to_correlate_profile,
+        "could not find any profile metadata in debug info");
   auto Result =
       collectPGOFuncNameStrings(Names, /*doCompression=*/true, CompressedNames);
   CounterOffsets.clear();
   Names.clear();
   return Result;
 }
 
 template <class IntPtrT>