[DWARFYAML] Add helper function getDWARFEmitterByName(). NFC.

[Higuoxing]

Summary

In this patch, we add a helper function getDWARFEmitterByName(). This
function returns the proper DWARF section emitting method by the name.

[Higuoxing]

This comment was removed by Higuoxing.

[Higuoxing]

Update.

[Higuoxing]

Pull out the changes of adding emitDebug[GNU]Pub[names/types] functions.

[jhenderson]

llvm/lib/ObjectYAML/ELFEmitter.cpp

952

I'm not sure this check is really giving us anything. There's a check in the getDWARFEmitterByName that the name is a recognised name (the default case), so I think you can just remove this check here.

953–955

if (Error Err = EmitFunc(*OS, DWARF);

[Higuoxing]

Address review comments.

Thanks for reviewing!

[jhenderson]

LGTM.

llvm/include/llvm/ObjectYAML/DWARFEmitter.h

 Error emitDebugGNUPubnames(raw_ostream &OS, const Data &DI);
 Error emitDebugGNUPubtypes(raw_ostream &OS, const Data &DI);
 Error emitDebugInfo(raw_ostream &OS, const Data &DI);
 Error emitDebugLine(raw_ostream &OS, const Data &DI);
 Error emitDebugAddr(raw_ostream &OS, const Data &DI);
 Error emitDebugStrOffsets(raw_ostream &OS, const Data &DI);
 Error emitDebugRnglists(raw_ostream &OS, const Data &DI);
 
+std::function<Error(raw_ostream &, const Data &)>
+getDWARFEmitterByName(StringRef SecName);
 Expected<StringMap<std::unique_ptr<MemoryBuffer>>>
 emitDebugSections(StringRef YAMLString,
                   bool IsLittleEndian = sys::IsLittleEndianHost);
 } // end namespace DWARFYAML
 } // end namespace llvm
 
 #endif // LLVM_OBJECTYAML_DWARFEMITTER_H

llvm/lib/ObjectYAML/DWARFEmitter.cpp

 /// The DWARF component of yaml2obj. Provided as library code for tests.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ObjectYAML/DWARFEmitter.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/ObjectYAML/DWARFYAML.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"

 }
 
 Error DWARFYAML::emitDebugRnglists(raw_ostream &OS, const Data &DI) {
   assert(DI.DebugRnglists && "unexpected emitDebugRnglists() call");
   return writeDWARFLists<DWARFYAML::RnglistEntry>(
       OS, *DI.DebugRnglists, DI.IsLittleEndian, DI.Is64BitAddrSize);
 }
 
-using EmitFuncType = Error (*)(raw_ostream &, const DWARFYAML::Data &);
+std::function<Error(raw_ostream &, const DWARFYAML::Data &)>
+DWARFYAML::getDWARFEmitterByName(StringRef SecName) {
+  auto EmitFunc =
+      StringSwitch<
+          std::function<Error(raw_ostream &, const DWARFYAML::Data &)>>(SecName)
+          .Case("debug_abbrev", DWARFYAML::emitDebugAbbrev)
+          .Case("debug_addr", DWARFYAML::emitDebugAddr)
+          .Case("debug_aranges", DWARFYAML::emitDebugAranges)
+          .Case("debug_gnu_pubnames", DWARFYAML::emitDebugGNUPubnames)
+          .Case("debug_gnu_pubtypes", DWARFYAML::emitDebugGNUPubtypes)
+          .Case("debug_info", DWARFYAML::emitDebugInfo)
+          .Case("debug_line", DWARFYAML::emitDebugLine)
+          .Case("debug_pubnames", DWARFYAML::emitDebugPubnames)
+          .Case("debug_pubtypes", DWARFYAML::emitDebugPubtypes)
+          .Case("debug_ranges", DWARFYAML::emitDebugRanges)
+          .Case("debug_rnglists", DWARFYAML::emitDebugRnglists)
+          .Case("debug_str", DWARFYAML::emitDebugStr)
+          .Case("debug_str_offsets", DWARFYAML::emitDebugStrOffsets)
+          .Default([&](raw_ostream &, const DWARFYAML::Data &) {
+            return createStringError(errc::not_supported,
+                                     SecName + " is not supported");
+          });
+
+  return EmitFunc;
+}
 
 static Error
-emitDebugSectionImpl(const DWARFYAML::Data &DI, EmitFuncType EmitFunc,
-                     StringRef Sec,
+emitDebugSectionImpl(const DWARFYAML::Data &DI, StringRef Sec,
                      StringMap<std::unique_ptr<MemoryBuffer>> &OutputBuffers) {
   std::string Data;
   raw_string_ostream DebugInfoStream(Data);
+
+  auto EmitFunc = DWARFYAML::getDWARFEmitterByName(Sec);
+
   if (Error Err = EmitFunc(DebugInfoStream, DI))
     return Err;
   DebugInfoStream.flush();
   if (!Data.empty())
     OutputBuffers[Sec] = MemoryBuffer::getMemBufferCopy(Data);
 
   return Error::success();
 }
DWARFYAML::emitDebugSections(StringRef YAMLString, bool IsLittleEndian) {
 
   DWARFYAML::Data DI;
   DI.IsLittleEndian = IsLittleEndian;
   YIn >> DI;
   if (YIn.error())
     return createStringError(YIn.error(), GeneratedDiag.getMessage());
 
   StringMap<std::unique_ptr<MemoryBuffer>> DebugSections;
-  Error Err = emitDebugSectionImpl(DI, &DWARFYAML::emitDebugInfo, "debug_info",
-                                   DebugSections);
-  Err = joinErrors(std::move(Err),
-                   emitDebugSectionImpl(DI, &DWARFYAML::emitDebugLine,
-                                        "debug_line", DebugSections));
-  Err = joinErrors(std::move(Err),
-                   emitDebugSectionImpl(DI, &DWARFYAML::emitDebugStr,
-                                        "debug_str", DebugSections));
-  Err = joinErrors(std::move(Err),
-                   emitDebugSectionImpl(DI, &DWARFYAML::emitDebugAbbrev,
-                                        "debug_abbrev", DebugSections));
-  Err = joinErrors(std::move(Err),
-                   emitDebugSectionImpl(DI, &DWARFYAML::emitDebugAranges,
-                                        "debug_aranges", DebugSections));
+  Error Err = Error::success();
+  cantFail(std::move(Err));
+
+  for (StringRef SecName : DI.getNonEmptySectionNames())
     Err = joinErrors(std::move(Err),
-                   emitDebugSectionImpl(DI, &DWARFYAML::emitDebugRanges,
-                                        "debug_ranges", DebugSections));
+                     emitDebugSectionImpl(DI, SecName, DebugSections));
 
   if (Err)
     return std::move(Err);
   return std::move(DebugSections);
 }

llvm/lib/ObjectYAML/ELFEmitter.cpp

Expected<uint64_t> emitDWARF(typename ELFT::Shdr &SHeader, StringRef Name,
   // We are unable to predict the size of debug data, so we request to write 0
   // bytes. This should always return us an output stream unless CBA is already
   // in an error state.
   raw_ostream *OS = CBA.getRawOS(0);
   if (!OS)
     return 0;
 
   uint64_t BeginOffset = CBA.tell();
-  Error Err = Error::success();
-  cantFail(std::move(Err));
 
-  if (Name == ".debug_str")
-    Err = DWARFYAML::emitDebugStr(*OS, DWARF);
-  else if (Name == ".debug_aranges")
-    Err = DWARFYAML::emitDebugAranges(*OS, DWARF);
-  else if (Name == ".debug_ranges")
-    Err = DWARFYAML::emitDebugRanges(*OS, DWARF);
-  else if (Name == ".debug_line")
-    Err = DWARFYAML::emitDebugLine(*OS, DWARF);
-  else if (Name == ".debug_addr")
-    Err = DWARFYAML::emitDebugAddr(*OS, DWARF);
-  else if (Name == ".debug_abbrev")
-    Err = DWARFYAML::emitDebugAbbrev(*OS, DWARF);
-  else if (Name == ".debug_info")
-    Err = DWARFYAML::emitDebugInfo(*OS, DWARF);
-  else if (Name == ".debug_pubnames")
-    Err = DWARFYAML::emitDebugPubnames(*OS, DWARF);
-  else if (Name == ".debug_pubtypes")
-    Err = DWARFYAML::emitDebugPubtypes(*OS, DWARF);
-  else if (Name == ".debug_gnu_pubnames")
-    Err = DWARFYAML::emitDebugGNUPubnames(*OS, DWARF);
-  else if (Name == ".debug_gnu_pubtypes")
-    Err = DWARFYAML::emitDebugGNUPubtypes(*OS, DWARF);
-  else if (Name == ".debug_str_offsets")
-    Err = DWARFYAML::emitDebugStrOffsets(*OS, DWARF);
-  else if (Name == ".debug_rnglists")
-    Err = DWARFYAML::emitDebugRnglists(*OS, DWARF);
-  else
-    llvm_unreachable("unexpected emitDWARF() call");
-
-  if (Err)
+  auto EmitFunc = DWARFYAML::getDWARFEmitterByName(Name.substr(1));
+  if (Error Err = EmitFunc(*OS, DWARF))
     return std::move(Err);
 
   return CBA.tell() - BeginOffset;
 }
 
 template <class ELFT>
 void ELFState<ELFT>::initDWARFSectionHeader(Elf_Shdr &SHeader, StringRef Name,
                                             ContiguousBlobAccumulator &CBA,
                                             ELFYAML::Section *YAMLSec) {