Dump swift5 reflection section data into dsym bundle generated binary with dsymutil

[rastogishubham]

Summary

This change allows dsymutil to dump swift5 reflection section data into the binary that is created by dsymutil in the dsym bundle.

We only want to emit these data of these sections if the input binary does not have those sections present in them. Therefore, assuming that the input binary doesn't have the section data, dsymutil is supposed to pick the data up from the object files. If the Input binary has the data, dsymutil works the same as it has before this change.

[aprantl]

Thanks, this is looking pretty good!

llvm/include/llvm/MC/MCObjectFileInfo.h

431

I know the other comments in this file also don't use this format, but FYI, you can doxygenify this as:

/// Swift5 Reflection Data Sections.
/// \{
MCSection *getSwift5FieldmdSection() { return Swift5FieldmdSection; }
  MCSection *getSwift5AssoctySection() { return Swift5AssoctySection; }
  MCSection *getSwift5BuiltinSection() { return Swift5BuiltinSection; }
  ...
/// \}

llvm/include/llvm/Object/ObjectFile.h

37

I think this fits better into the BinaryFormat directory. I would even consider adding a swift.h header there. After all that's also where the DWARF sections are defined (in Dwarf.def/Dwarf.h).

44

maybe "Unknown = 0" ?

llvm/lib/DWARFLinker/DWARFStreamer.cpp

313

Maybe just have a MOFI->getSwiftReflectionSection(ReflSectionType) function?

330

it's better to explicitly list all cases instead of having a default: label. This way we get a warning when someone adds a new case to the enum that isn't covered by the switch.

llvm/lib/MC/MCObjectFileInfo.cpp

302

Only dsymutil puts these into the __DWARF section. We need to at least comment this, but if we can make this configurable, that would be even better.

llvm/test/tools/dsymutil/Inputs/main.yaml

5117

It's great to have this in YAML form. Do you think it might be possible to strip out parts of the executable that aren't strictly necessary for testing the dsymutil functionality? Maybe by running delta on the yaml file and test that the test still passes? I understand that some of the hardcoded offsets in the yaml might might make this hard.

llvm/test/tools/dsymutil/reflection-dump.test

1 ↗

(On Diff #391487)

RUN: rm -rf %t.dir && mkdir -p %t.dir/tmp

9 ↗

(On Diff #391487)

Are there any error cases that we'd want to test?

10 ↗

(On Diff #391487)

Nice testcase!

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

299

Does binaryHasSwiftReflectionSections() sound better? (not sure)

303

// If the input binary has swift5 reflection sections, there is no need to copy them to the .dSYM. Only copy them for binaries where the linker omitted the reflection metadata.

310

Nit: LLVM style always wants a . at the end of each sentence.

474

maybe also factor this into a copySwiftReflectionMetadata() function?

[rastogishubham]

llvm/include/llvm/MC/MCObjectFileInfo.h

431

Good to know, would it be weird to doxygen just the functions we added though?

llvm/lib/DWARFLinker/DWARFStreamer.cpp

313

I think that just moves the switch statement into a different function, and there is no overt benefit to doing that.

llvm/lib/MC/MCObjectFileInfo.cpp

302

The only thing I can think about doing here is making a function that sets the swift5 sections and takes a const char* for the section name, does that work?

llvm/test/tools/dsymutil/reflection-dump.test

1 ↗

(On Diff #391487)

Thank you

9 ↗

(On Diff #391487)

The only error I saw was if you messed up the yaml files, then the otool output would come out wrong, not sure what else to check for. Any suggestions? I guess one thing I can test is that when the input binary does have the reflection metadata sections, then we should not emit them in the output. Not really an error test case though.

10 ↗

(On Diff #391487)

Thank you!

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

299

I have always considered myself bad with names, so I am gonna go with yours :)

310

Thanks!

[rastogishubham]

Added the changes as mentioned by Adrian, based on my comments in response to him

[rastogishubham]

Reduced the testcase yaml files, made the Swift5ReflectionSection creation confirgurable, also moved the copying of the reflection section metadata to its own function called copySwiftReflectionMetadata

[aprantl]

Thanks for reducing the test! This looks much more palatable.

llvm/include/llvm/BinaryFormat/Swift.h

15

If it's already in the namespace we don't need to repeat Swift in the name. I would go with:

enum Swift5ReflectionSectionKind {
  Unknown = 0,
  Fieldmd,
  ...
};

or 

enum ReflectionSectionKind {
  Unknown = 0,
  Swift5Fieldmd,
  ...
};

22

We might want to split this out into a .def file. See Dwarf.def for an example:

Swift.def:

#ifdef HANDLE_SWIFT_SECTION
#undef HANDLE_SWIFT_SECTION
#endif
// Enum Kind, Mach-O name, ELF name, COFF name.
HANDLE_SWIFT_SECTION(Swift5Fieldmd, "__swift5fieldmd", ".swift5fieldmd", ???)

Swift.h

enum ReflectionSectionKind {
  Unknown = 0,
#define HANDLE_SWIFT_SECTION(KIND, MACHO, ELF, COFF) #KIND,
#include "llvm/BinaryFormat/Swift/def"
};

llvm/include/llvm/DWARFLinker/DWARFStreamer.h

90

I would drop the "5" here.

llvm/include/llvm/MC/MCObjectFileInfo.h

232

Here the Swift"5" makes sense.

431

I would do a second NFC patch to just doxygenify the entire class.

447

this should be a StringRef

llvm/lib/MC/MCObjectFileInfo.cpp

302

I would just write:

// The architecture of dsymutil makes it very difficult to copy the Swift reflection metadata sections into the __TEXT segment, so dsymutil creates these sections in the __DWARF segment instead.

310

If you create a Swift.def file, this can also be just a single #include with some clever macro substitutions. Check out the dwarf names are stringified for an example.

1022

The DWARF segment needs to be hardcoded in dsymutil or DwarfLinker. The MC layer should not know about this. So we need to thread the flag all the way to DwarfLinker.

llvm/lib/Object/MachOObjectFile.cpp

4725

If you create a Swift.def file, this can also be just a single #include with some clever macro substitutions. Check out the dwarf names are stringified for an example.

[rastogishubham]

Added a new file called Swift.def, it contains macros that define the various swift reflection section names and contents so we can use them throughout the code, and code changes that come with using the def file. Also added a change to have dwarflinker pass in the segment "__DWARF" to the streamer and the MC to create the reflection sections in the dwarf segment

[rastogishubham]

Fixed comments

[aprantl]

Thanks for the update! We're down to cosmetic changes.

llvm/include/llvm/BinaryFormat/Swift.def

27

missing newline

27

This is nice.

llvm/include/llvm/DWARFLinker/DWARFStreamer.h

91

s/type/kind/

llvm/include/llvm/MC/TargetRegistry.h

394 ↗

(On Diff #394191)

Instead of passing a StringRef as a pointer, we can just pass a StringRef value, like this:

StringRef Swift5ReflectionSegmentName = {}

and then check for .empty() instead for nullptr.

llvm/lib/DWARFLinker/DWARFStreamer.cpp

313

What's potentially more elegant is to have a std::array of reflection sections in MOFI instead of 6 separate member variables. If you change Unknown to -1 and let Fieldmd be 0 you could access it as Swift5ReflectionSection[Swift5ReflectionSectionType::Fieldmd]. Then we could replace the 6 accessor functions with one getSwiftReflectionSection(Swift5ReflectionSectionType)

llvm/lib/MC/MCObjectFileInfo.cpp

52

just StringRef

311

nice!

311

is this redundandant?

1000

StringRef

llvm/test/tools/dsymutil/reflection-dump.test

42 ↗

(On Diff #394191)

newline

[rastogishubham]

llvm/lib/MC/MCObjectFileInfo.cpp

311

Yes it is definitely redundant, didn't think of the scope

[rastogishubham]

Removed StringRef pointer and replaced it with a default empty StringRef argument. Changed Unkown to -1 and removed distinct swift5 sections in MOFI to one std::array. Changed names from Swift5ReflectionSectionType to Swift5ReflectionSectionKind.

[aprantl]

llvm/include/llvm/BinaryFormat/Swift.h

19

You could make this Unknown, Last = Unknown see comment below.

llvm/include/llvm/MC/MCObjectFileInfo.h

435

Nice.

[aprantl]

llvm/include/llvm/MC/MCObjectFileInfo.h

234

1. Instead of hardcoding 6, does std::array<MCSection *, Swift5ReflectionSectionKind::Last> work?

2. = {}; is shorter than listing all the nullptrs.

3. I would call this Swift5ReflectionSections

[JDevlieghere]

llvm/include/llvm/MC/MCObjectFileInfo.h

233

Is there a way we can keep this in sync automatically with the number of sections in Swift.def?

239

Should this be part of MCContext?

447

Similar as above, this seems really out of place.

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

307

Do we really need to create a new binary holder? Why can't we use the one used by the DWARFLinker?

[rastogishubham]

llvm/include/llvm/MC/MCObjectFileInfo.h

239

Sure!

447

I don't think this makes sense, I do not think the swift5reflectionsegmentname should be part of the Triple, so it has to be it's own argument.

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

307

Did not realize there was one, but I am not sure why

bool generateDsymCompanion(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
                           const DebugMap &DM, SymbolMapTranslator &Translator,
                           MCStreamer &MS, raw_fd_ostream &OutFile) {

in MachoUtils.cpp creates it's own BinaryHolder?

[rastogishubham]

Put StringRef Swift5ReflectionSegmentName in MCContext, made the SwiftReflectionSections Array the size of enum::Last instead of harcoding.

[aprantl]

llvm/include/llvm/MC/MCObjectFileInfo.h

447

Similar as above, this seems really out of place.

@JDevlieghere can you clarify what you mean? We need to make the reflection segment name configurable. What is it that you are suggesting?

[rastogishubham]

llvm/include/llvm/MC/MCObjectFileInfo.h

447

@JDevlieghere Hi Jonas, can you please clarify what you mean? As Adrian said we need to make the segment name configurable, and I don't think it is valid to make that part of the Triple.

Thanks!

[JDevlieghere]

llvm/include/llvm/MC/MCObjectFileInfo.h

447

I meant that I think it's weird that generic MC interfaces need to know about Swift section names. I understand the need to pass the information, I just don't think it should be part of the interface like this. If I follow the code correctly, the Swift 5 reflection segment name is stored in the MCContext. Instead of passing this the Swift5ReflectionSegmentName in here, can it query the *Ctx for the name? That would address my concern.

[rastogishubham]

llvm/include/llvm/MC/MCObjectFileInfo.h

447

Oh I don't know why I didn't realize that! Yes the ctx is part of the same MCObjectFileInfo object, so instead of passing it as an argument, it should just be something we should query from within the method itself!

Thank you Jonas, really appreciate your help here!

[rastogishubham]

Removed the argument Swift5ReflectionSectionName from initMachOMCObjectFileInfo function and get the name from the Ctx object present within the MCObjectFileInfo object instead

[JDevlieghere]

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

299

Instead of having an in-our argument, could this function return an Expected<bool> instead? I also find NoError confusing because you end up checking a double negation, i.e. !NoError.

300

Why are the LinkOptions not const?

348–351

You' assuming that these pointers are non-null so why not pass DebugMapObject and Streamer by references? If that's not an option, I'd just pass the underlying pointers instead. I can't think of any benefit of passing the unique_ptr by reference instead.

357–358

A common style in LLVM is to do if(Foo* foo = ...) {.

366

This use of auto doesn't seem obvious to me (https://llvm.org/docs/CodingStandards.html#use-auto-type-deduction-to-make-code-more-readable)

474–476

No braces around single-line if's (https://llvm.org/docs/CodingStandards.html#id59)

[rastogishubham]

Changed the logic for binaryHasSwiftReflectionSections to remove the NoError bool flag, made LinkOpts const, passed DebugMapObject and DwarfStreamer Objects as pointers to copySwiftReflectionMetadata, removed auto where it isn't obvious, removed braces from single line if, used llvm style if statement for dyn_cast

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

299

I realized that NoError is not needed, the function just needs to return if there are reflectionsections in the input binary. So a simple return bool value should be enough, the reason is because creating the ObjectEntry and Object are handled in MachoUtils.cpp anyway.

[aprantl]

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

305

I don't think the Map.getTriple().isOSDarwin() && check is necessary.

312

It would be good to comment here:

// Any errors will be diagnosed later in the main loop, ignore them here.
``

[rastogishubham]

Added the comments as Adrian suggested, and removed the check Adrian suggested as well

[JDevlieghere]

LGTM modulo the early return.

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

347–349

Seems like an early return here could save you a level of indentation.

[rastogishubham]

Added early return and change else { if .. to and else if

[rastogishubham]

In DwarfLinkerForBinary.cpp Line 475, we need to make sure that copySwiftReflectionMetadata is not called when the -no-output option is passed, this is because the DwarfStreamer object is not created, and copySwiftReflectionMetadata calls through to a member method of the DwarfStreamer Object. I also moved reflection-metadata.test to the X86 folder because some non X86 tests failed due to target triple issues

[aprantl]

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

473

lower case for "Reflection Sections" ?

llvm/include/llvm/BinaryFormat/Swift.h

+//===-- llvm/BinaryFormat/Swift.h ---Swift Constants-------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+
+#ifndef LLVM_BINARYFORMAT_SWIFT_H
+#define LLVM_BINARYFORMAT_SWIFT_H
+
+namespace llvm {
+namespace swift {
+
+enum Swift5ReflectionSectionKind {
+#define HANDLE_SWIFT_SECTION(KIND, MACHO, ELF, COFF) KIND,
+#include "llvm/BinaryFormat/Swift.def"
+#undef HANDLE_SWIFT_SECTION
+  Unknown,
+  Last = Unknown
+};
+} // end of namespace swift
+} // end of namespace llvm
+
+#endif

llvm/include/llvm/BinaryFormat/Swift.def

+//===- llvm/BinaryFormat/Swift.def - Swift definitions ---------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Macros for running through Swift enumerators.
+//
+//===----------------------------------------------------------------------===//
+
+#if !(defined HANDLE_SWIFT_SECTION)
+#error "Missing macro definition of HANDLE_SWIFT_SECTION"
+#endif
+
+#ifndef HANDLE_SWIFT_SECTION
+#define HANDLE_SWIFT_SECTION(KIND, MACHO, ELF, COFF)
+#endif
+
+HANDLE_SWIFT_SECTION(Fieldmd, "__swift5_fieldmd", "swift5_fieldmd", ".sw5flmd")
+HANDLE_SWIFT_SECTION(Assocty, "__swift5_assocty", "swift5_assocty", ".sw5asty")
+HANDLE_SWIFT_SECTION(Builtin, "__swift5_builtin", "swift5_builtin", ".sw5bltn")
+HANDLE_SWIFT_SECTION(Capture, "__swift5_capture", "swift5_capture", ".sw5cptr")
+HANDLE_SWIFT_SECTION(Typeref, "__swift5_typeref", "swift5_typeref", ".sw5tyrf")
+HANDLE_SWIFT_SECTION(Reflstr, "__swift5_reflstr", "swift5_reflstr", ".sw5rfst")

llvm/include/llvm/DWARFLinker/DWARFStreamer.h

 //===- DwarfStreamer.h ------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_DWARFLINKER_DWARFSTREAMER_H
 #define LLVM_DWARFLINKER_DWARFSTREAMER_H
 
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/CodeGen/AccelTable.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/DWARFLinker/DWARFLinker.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"

 class DwarfStreamer : public DwarfEmitter {
 public:
   DwarfStreamer(OutputFileType OutFileType, raw_pwrite_stream &OutFile,
                 std::function<StringRef(StringRef Input)> Translator,
                 messageHandler Error, messageHandler Warning)
       : OutFile(OutFile), OutFileType(OutFileType), Translator(Translator),
         ErrorHandler(Error), WarningHandler(Warning) {}
 
-  bool init(Triple TheTriple);
+  bool init(Triple TheTriple, StringRef Swift5ReflectionSegmentName);
 
   /// Dump the file to the disk.
   void finish();
 
   AsmPrinter &getAsmPrinter() const { return *Asm; }
 
   /// Set the current output section to debug_info and change
   /// the MC Dwarf version to \p DwarfVersion.
public:
   void emitSectionContents(StringRef SecData, StringRef SecName) override;
 
   /// Emit the string table described by \p Pool.
   void emitStrings(const NonRelocatableStringpool &Pool) override;
 
   /// Emit the swift_ast section stored in \p Buffer.
   void emitSwiftAST(StringRef Buffer);
 
+  /// Emit the swift reflection section stored in \p Buffer.
+  void emitSwiftReflectionSection(
+      llvm::swift::Swift5ReflectionSectionKind ReflSectionKind,
+      StringRef Buffer, uint32_t Alignment, uint32_t Size);
+
   /// Emit debug_ranges for \p FuncRange by translating the
   /// original \p Entries.
   void emitRangesEntries(
       int64_t UnitPcOffset, uint64_t OrigLowPc,
       const FunctionIntervals::const_iterator &FuncRange,
       const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
       unsigned AddressSize) override;
 

llvm/include/llvm/MC/MCContext.h

public:
     using DiagHandlerTy =
         std::function<void(const SMDiagnostic &, bool, const SourceMgr &,
                            std::vector<const MDNode *> &)>;
     enum Environment { IsMachO, IsELF, IsGOFF, IsCOFF, IsWasm, IsXCOFF };
 
   private:
     Environment Env;
 
+    /// The name of the Segment where Swift5 Reflection Section data will be
+    /// outputted
+    StringRef Swift5ReflectionSegmentName;
+
     /// The triple for this object.
     Triple TT;
 
     /// The SourceMgr for this object, if any.
     const SourceMgr *SrcMgr;
 
     /// The SourceMgr for inline assembly, if any.
     std::unique_ptr<SourceMgr> InlineSrcMgr;
private:
     // sections (e.g. via _attribute_((section("myname")))).
     DenseSet<StringRef> ELFSeenGenericMergeableSections;
 
   public:
     explicit MCContext(const Triple &TheTriple, const MCAsmInfo *MAI,
                        const MCRegisterInfo *MRI, const MCSubtargetInfo *MSTI,
                        const SourceMgr *Mgr = nullptr,
                        MCTargetOptions const *TargetOpts = nullptr,
-                       bool DoAutoReset = true);
+                       bool DoAutoReset = true,
+                       StringRef Swift5ReflSegmentName = {});
     MCContext(const MCContext &) = delete;
     MCContext &operator=(const MCContext &) = delete;
     ~MCContext();
 
     Environment getObjectFileType() const { return Env; }
 
+    const StringRef &getSwift5ReflectionSegmentName() const {
+      return Swift5ReflectionSegmentName;
+    }
     const Triple &getTargetTriple() const { return TT; }
     const SourceMgr *getSourceManager() const { return SrcMgr; }
 
     void initInlineSourceManager();
     SourceMgr *getInlineSourceManager() {
       return InlineSrcMgr.get();
     }
     std::vector<const MDNode *> &getLocInfos() { return LocInfos; }

llvm/include/llvm/MC/MCObjectFileInfo.h

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_MC_MCOBJECTFILEINFO_H
 #define LLVM_MC_MCOBJECTFILEINFO_H
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/VersionTuple.h"
 
 namespace llvm {
 class MCContext;
 class MCSection;
 
protected:
   MCSection *GIATsSection = nullptr;
   MCSection *GLJMPSection = nullptr;
 
   // XCOFF specific sections
   MCSection *TOCBaseSection = nullptr;
   MCSection *ReadOnly8Section = nullptr;
   MCSection *ReadOnly16Section = nullptr;
 
+  // Swift5 Reflection Data Sections
+  std::array<MCSection *, swift::Swift5ReflectionSectionKind::Last>
+      Swift5ReflectionSections = {};
+
 public:
   void initMCObjectFileInfo(MCContext &MCCtx, bool PIC,
                             bool LargeCodeModel = false);
   virtual ~MCObjectFileInfo();
   MCContext &getContext() const { return *Ctx; }
 
   bool getSupportsWeakOmittedEHFrame() const {
     return SupportsWeakOmittedEHFrame;
   }
   bool getSupportsCompactUnwindWithoutEHFrame() const {
     return SupportsCompactUnwindWithoutEHFrame;
   }
public:
 
   // XCOFF specific sections
   MCSection *getTOCBaseSection() const { return TOCBaseSection; }
 
   MCSection *getEHFrameSection() const { return EHFrameSection; }
 
   bool isPositionIndependent() const { return PositionIndependent; }
 
+  // Swift5 Reflection Data Sections
+  MCSection *getSwift5ReflectionSection(
+      llvm::swift::Swift5ReflectionSectionKind ReflSectionKind) {
+    return ReflSectionKind != llvm::swift::Swift5ReflectionSectionKind::Unknown
+               ? Swift5ReflectionSections[ReflSectionKind]
+               : nullptr;
+  }
+
 private:
   bool PositionIndependent = false;
   MCContext *Ctx = nullptr;
   VersionTuple SDKVersion;
   Optional<Triple> DarwinTargetVariantTriple;
   VersionTuple DarwinTargetVariantSDKVersion;
 
   void initMachOMCObjectFileInfo(const Triple &T);
   void initELFMCObjectFileInfo(const Triple &T, bool Large);
   void initGOFFMCObjectFileInfo(const Triple &T);
   void initCOFFMCObjectFileInfo(const Triple &T);
   void initWasmMCObjectFileInfo(const Triple &T);
   void initXCOFFMCObjectFileInfo(const Triple &T);
   MCSection *getDwarfComdatSection(const char *Name, uint64_t Hash) const;
 
 public:
   void setSDKVersion(const VersionTuple &TheSDKVersion) {

llvm/include/llvm/Object/MachO.h

 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/BinaryFormat/MachO.h"
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
public:
   static bool isValidArch(StringRef ArchFlag);
   static ArrayRef<StringRef> getValidArchs();
   static Triple getHostArch();
 
   bool isRelocatableObject() const override;
 
   StringRef mapDebugSectionName(StringRef Name) const override;
 
+  llvm::swift::Swift5ReflectionSectionKind
+  mapReflectionSectionNameToEnumValue(StringRef SectionName) const override;
+
   bool hasPageZeroSegment() const { return HasPageZeroSegment; }
 
   static bool classof(const Binary *v) {
     return v->isMachO();
   }
 
   static uint32_t
   getVersionMinMajor(MachO::version_min_command &C, bool SDK) {

llvm/include/llvm/Object/ObjectFile.h

 #ifndef LLVM_OBJECT_OBJECTFILE_H
 #define LLVM_OBJECT_OBJECTFILE_H
 
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/BinaryFormat/Magic.h"
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/Error.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include <cassert>
 #include <cstdint>
 #include <memory>
 #include <system_error>
 
 namespace llvm {
 
 class SubtargetFeatures;
 
 namespace object {
 
 class COFFObjectFile;
 class MachOObjectFile;
 class ObjectFile;
 class SectionRef;
 class SymbolRef;
 class symbol_iterator;
 class WasmObjectFile;
 
 using section_iterator = content_iterator<SectionRef>;
 
 /// This is a value type class that represents a single relocation in the list
 /// of relocations in the object file.
 class RelocationRef {
   DataRefImpl RelocationPimpl;
protected:
   friend class RelocationRef;
   virtual void moveRelocationNext(DataRefImpl &Rel) const = 0;
   virtual uint64_t getRelocationOffset(DataRefImpl Rel) const = 0;
   virtual symbol_iterator getRelocationSymbol(DataRefImpl Rel) const = 0;
   virtual uint64_t getRelocationType(DataRefImpl Rel) const = 0;
   virtual void getRelocationTypeName(DataRefImpl Rel,
                                      SmallVectorImpl<char> &Result) const = 0;
 
+  virtual llvm::swift::Swift5ReflectionSectionKind
+  mapReflectionSectionNameToEnumValue(StringRef SectionName) const {
+    return llvm::swift::Swift5ReflectionSectionKind::Unknown;
+  };
+
   Expected<uint64_t> getSymbolValue(DataRefImpl Symb) const;
 
 public:
   ObjectFile() = delete;
   ObjectFile(const ObjectFile &other) = delete;
 
   uint64_t getCommonSymbolSize(DataRefImpl Symb) const {
     Expected<uint32_t> SymbolFlagsOrErr = getSymbolFlags(Symb);

llvm/lib/DWARFLinker/DWARFStreamer.cpp

 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/MC/MCTargetOptionsCommandFlags.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Target/TargetOptions.h"
 
 namespace llvm {
 
-bool DwarfStreamer::init(Triple TheTriple) {
+bool DwarfStreamer::init(Triple TheTriple,
+                         StringRef Swift5ReflectionSegmentName) {
   std::string ErrorStr;
   std::string TripleName;
   StringRef Context = "dwarf streamer init";
 
   // Get the target.
   const Target *TheTarget =
       TargetRegistry::lookupTarget(TripleName, TheTriple, ErrorStr);
   if (!TheTarget)
bool DwarfStreamer::init(Triple TheTriple,
   MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
   if (!MAI)
     return error("no asm info for target " + TripleName, Context), false;
 
   MSTI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
   if (!MSTI)
     return error("no subtarget info for target " + TripleName, Context), false;
 
-  MC.reset(new MCContext(TheTriple, MAI.get(), MRI.get(), MSTI.get()));
-  MOFI.reset(TheTarget->createMCObjectFileInfo(*MC, /*PIC=*/false));
+  MC.reset(new MCContext(TheTriple, MAI.get(), MRI.get(), MSTI.get(), nullptr,
+                         nullptr, true, Swift5ReflectionSegmentName));
+  MOFI.reset(TheTarget->createMCObjectFileInfo(*MC, /*PIC=*/false, false));
   MC->setObjectFileInfo(MOFI.get());
 
   MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, MCOptions);
   if (!MAB)
     return error("no asm backend for target " + TripleName, Context), false;
 
   MII.reset(TheTarget->createMCInstrInfo());
   if (!MII)

 /// Emit the swift_ast section stored in \p Buffers.
 void DwarfStreamer::emitSwiftAST(StringRef Buffer) {
   MCSection *SwiftASTSection = MOFI->getDwarfSwiftASTSection();
   SwiftASTSection->setAlignment(Align(32));
   MS->SwitchSection(SwiftASTSection);
   MS->emitBytes(Buffer);
 }
 
+void DwarfStreamer::emitSwiftReflectionSection(
+    llvm::swift::Swift5ReflectionSectionKind ReflSectionKind, StringRef Buffer,
+    uint32_t Alignment, uint32_t Size) {
+  MCSection *ReflectionSection =
+      MOFI->getSwift5ReflectionSection(ReflSectionKind);
+  if (ReflectionSection == nullptr)
+    return;
+  ReflectionSection->setAlignment(Align(Alignment));
+  MS->SwitchSection(ReflectionSection);
+  MS->emitBytes(Buffer);
+}
+
 /// Emit the debug_range section contents for \p FuncRange by
 /// translating the original \p Entries. The debug_range section
 /// format is totally trivial, consisting just of pairs of address
 /// sized addresses describing the ranges.
 void DwarfStreamer::emitRangesEntries(
     int64_t UnitPcOffset, uint64_t OrigLowPc,
     const FunctionIntervals::const_iterator &FuncRange,
     const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
     unsigned AddressSize) {
   MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
 
   // Offset each range by the right amount.
   int64_t PcOffset = Entries.empty() ? 0 : FuncRange.value() + UnitPcOffset;
   for (const auto &Range : Entries) {
     if (Range.isBaseAddressSelectionEntry(AddressSize)) {
       warn("unsupported base address selection operation",
            "emitting debug_ranges");
       break;
     }
     // Do not emit empty ranges.

llvm/lib/MC/MCContext.cpp

 static void defaultDiagHandler(const SMDiagnostic &SMD, bool, const SourceMgr &,
                                std::vector<const MDNode *> &) {
   SMD.print(nullptr, errs());
 }
 
 MCContext::MCContext(const Triple &TheTriple, const MCAsmInfo *mai,
                      const MCRegisterInfo *mri, const MCSubtargetInfo *msti,
                      const SourceMgr *mgr, MCTargetOptions const *TargetOpts,
-                     bool DoAutoReset)
-    : TT(TheTriple), SrcMgr(mgr), InlineSrcMgr(nullptr),
-      DiagHandler(defaultDiagHandler), MAI(mai), MRI(mri), MSTI(msti),
-      Symbols(Allocator), UsedNames(Allocator),
+                     bool DoAutoReset, StringRef Swift5ReflSegmentName)
+    : Swift5ReflectionSegmentName(Swift5ReflSegmentName), TT(TheTriple),
+      SrcMgr(mgr), InlineSrcMgr(nullptr), DiagHandler(defaultDiagHandler),
+      MAI(mai), MRI(mri), MSTI(msti), Symbols(Allocator), UsedNames(Allocator),
       InlineAsmUsedLabelNames(Allocator),
       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
       AutoReset(DoAutoReset), TargetOptions(TargetOpts) {
   SecureLogFile = AsSecureLogFileName;
 
   if (SrcMgr && SrcMgr->getNumBuffers())
     MainFileName = std::string(SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())
                                    ->getBufferIdentifier());

llvm/lib/MC/MCObjectFileInfo.cpp

static bool useCompactUnwind(const Triple &T) {
   // And the iOS simulator.
   if (T.isiOS() && T.isX86())
     return true;
 
   return false;
 }
 
 void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
   // MachO
   SupportsWeakOmittedEHFrame = false;
 
   EHFrameSection = Ctx->getMachOSection(
       "__TEXT", "__eh_frame",
       MachO::S_COALESCED | MachO::S_ATTR_NO_TOC |
           MachO::S_ATTR_STRIP_STATIC_SYMS | MachO::S_ATTR_LIVE_SUPPORT,
       SectionKind::getReadOnly());
 
StackMapSection = Ctx->getMachOSection("__LLVM_STACKMAPS", "__llvm_stackmaps",
                                          0, SectionKind::getMetadata());
 
   FaultMapSection = Ctx->getMachOSection("__LLVM_FAULTMAPS", "__llvm_faultmaps",
                                          0, SectionKind::getMetadata());
 
   RemarksSection = Ctx->getMachOSection(
       "__LLVM", "__remarks", MachO::S_ATTR_DEBUG, SectionKind::getMetadata());
 
+  // The architecture of dsymutil makes it very difficult to copy the Swift
+  // reflection metadata sections into the __TEXT segment, so dsymutil creates
+  // these sections in the __DWARF segment instead.
+  if (!Ctx->getSwift5ReflectionSegmentName().empty()) {
+#define HANDLE_SWIFT_SECTION(KIND, MACHO, ELF, COFF)                           \
+  Swift5ReflectionSections[llvm::swift::Swift5ReflectionSectionKind::KIND] =   \
+      Ctx->getMachOSection(Ctx->getSwift5ReflectionSegmentName().data(),       \
+                           MACHO, 0, SectionKind::getMetadata());
+#include "llvm/BinaryFormat/Swift.def"
+  }
+
   TLSExtraDataSection = TLSTLVSection;
 }
 
 void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
   switch (T.getArch()) {
   case Triple::mips:
   case Triple::mipsel:
   case Triple::mips64:
DwarfMacinfoSection = Ctx->getXCOFFSection(
       /* MultiSymbolsAllowed */ true, ".dwmac", XCOFF::SSUBTYP_DWMAC);
 }
 
 MCObjectFileInfo::~MCObjectFileInfo() {}
 
 void MCObjectFileInfo::initMCObjectFileInfo(MCContext &MCCtx, bool PIC,
                                             bool LargeCodeModel) {
   PositionIndependent = PIC;
   Ctx = &MCCtx;
 
   // Common.
   CommDirectiveSupportsAlignment = true;
   SupportsWeakOmittedEHFrame = true;
   SupportsCompactUnwindWithoutEHFrame = false;
   OmitDwarfIfHaveCompactUnwind = false;
 
   FDECFIEncoding = dwarf::DW_EH_PE_absptr;
 
   CompactUnwindDwarfEHFrameOnly = 0;
 
   EHFrameSection = nullptr;             // Created on demand.
   CompactUnwindSection = nullptr;       // Used only by selected targets.
   DwarfAccelNamesSection = nullptr;     // Used only by selected targets.
   DwarfAccelObjCSection = nullptr;      // Used only by selected targets.
   DwarfAccelNamespaceSection = nullptr; // Used only by selected targets.
   DwarfAccelTypesSection = nullptr;     // Used only by selected targets.
 
   Triple TheTriple = Ctx->getTargetTriple();
   switch (Ctx->getObjectFileType()) {
   case MCContext::IsMachO:
     initMachOMCObjectFileInfo(TheTriple);
     break;
   case MCContext::IsCOFF:
     initCOFFMCObjectFileInfo(TheTriple);
     break;
   case MCContext::IsELF:
     initELFMCObjectFileInfo(TheTriple, LargeCodeModel);
     break;
   case MCContext::IsGOFF:

llvm/lib/Object/MachOObjectFile.cpp

 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/MachO.h"
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/Object/Error.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
ObjectFile::createMachOObjectFile(MemoryBufferRef Buffer,
   return make_error<GenericBinaryError>("Unrecognized MachO magic number",
                                         object_error::invalid_file_type);
 }
 
 StringRef MachOObjectFile::mapDebugSectionName(StringRef Name) const {
   return StringSwitch<StringRef>(Name)
       .Case("debug_str_offs", "debug_str_offsets")
       .Default(Name);
 }
 
 Expected<std::vector<std::string>>
 MachOObjectFile::findDsymObjectMembers(StringRef Path) {
   SmallString<256> BundlePath(Path);
   // Normalize input path. This is necessary to accept `bundle.dSYM/`.
   sys::path::remove_dots(BundlePath);
   if (!sys::fs::is_directory(BundlePath) ||
       sys::path::extension(BundlePath) != ".dSYM")
MachOObjectFile::findDsymObjectMembers(StringRef Path) {
   if (EC)
     return createFileError(BundlePath, errorCodeToError(EC));
   if (ObjectPaths.empty())
     return createStringError(std::error_code(),
                              "%s: no objects found in dSYM bundle",
                              Path.str().c_str());
   return ObjectPaths;
 }
+
+llvm::swift::Swift5ReflectionSectionKind
+MachOObjectFile::mapReflectionSectionNameToEnumValue(
+    StringRef SectionName) const {
+#define HANDLE_SWIFT_SECTION(KIND, MACHO, ELF, COFF)                           \
+  .Case(MACHO, llvm::swift::Swift5ReflectionSectionKind::KIND)
+  return StringSwitch<llvm::swift::Swift5ReflectionSectionKind>(SectionName)
+#include "llvm/BinaryFormat/Swift.def"
+      .Default(llvm::swift::Swift5ReflectionSectionKind::Unknown);
+#undef HANDLE_SWIFT_SECTION
+}

llvm/test/tools/dsymutil/Inputs/main.yaml

+# How to generate this file:
+# 1. First take a swift file and run xcrun swiftc -g -v test.swift 
+# reflection_metadata.swift, make sure the two swift files are in a short path 
+# like /tmp/
+
+# 2. Now you can see what the driver does, generate the object files in the 
+# tmp directory and link them to create the input binary
+
+# 3. Run obj2yaml on the input binary to create a yaml file and strip out the 
+# swift5 reflection sections from the load commands in the text segment
+
+# 4. I ran delta to reduce this file.
+
+--- !mach-o
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+  StringTable:
+    - ' '
+    - '_$s4main10MyProtocolMp'
+    - '_$s4main10MyProtocolTL'
+    - '_$s4main11ConformanceV5innerSivM'
+    - '_$s4main11ConformanceV5innerSivg'
+    - '_$s4main11ConformanceV5innerSivpMV'
+    - '_$s4main11ConformanceV5innerSivpfi'
+    - '_$s4main11ConformanceV5innerSivs'
+    - '_$s4main11ConformanceVAA10MyProtocolAAMc'
+    - '_$s4main11ConformanceVAA10MyProtocolAAWP'
+    - '_$s4main11ConformanceVMa'
+    - '_$s4main11ConformanceVMn'
+    - '_$s4main11ConformanceVN'
+    - '_$s4main12Conformance2V5innerSivM'
+    - '_$s4main12Conformance2V5innerSivg'
+    - '_$s4main12Conformance2V5innerSivpMV'
+    - '_$s4main12Conformance2V5innerSivpfi'
+    - '_$s4main12Conformance2V5innerSivs'
+    - '_$s4main12Conformance2VAA10MyProtocolAAMc'
+    - '_$s4main12Conformance2VAA10MyProtocolAAWP'
+    - '_$s4main12Conformance2VMa'
+    - '_$s4main12Conformance2VMn'
+    - '_$s4main12Conformance2VN'
+    - '_$s4main13MyGenericEnumOMa'
+    - '_$s4main13MyGenericEnumOMn'
+    - '_$s4main14MyGenericClassC1t1i3mgs3mgeACyxGx_5InnerQzAA0bC6StructVyxGAA0bC4EnumOyxGtcfC'
+    - '_$s4main14MyGenericClassC1t1i3mgs3mgeACyxGx_5InnerQzAA0bC6StructVyxGAA0bC4EnumOyxGtcfCTq'
+    - '_$s4main14MyGenericClassC1t1i3mgs3mgeACyxGx_5InnerQzAA0bC6StructVyxGAA0bC4EnumOyxGtcfc'
+    - '_$s4main14MyGenericClassCMa'
+    - '_$s4main14MyGenericClassCMn'
+    - '_$s4main14MyGenericClassCfD'
+    - '_$s4main14MyGenericClassCfd'
+    - '_$s4main15MyGenericStructVMa'
+    - '_$s4main15MyGenericStructVMn'
+    - '_$s4main16makeSomeClosures1tyycx_tAA10MyProtocolRzlF'
+    - '_$s4main6MyEnumOMa'
+    - '_$s4main6MyEnumOMn'
+    - '_$s4main6MyEnumON'
+    - '_$s4main7MyClassC1i2ms2meACSi_AA0B6StructVAA0B4EnumOtcfC'
+    - '_$s4main7MyClassC1i2ms2meACSi_AA0B6StructVAA0B4EnumOtcfCTq'
+    - '_$s4main7MyClassC1i2ms2meACSi_AA0B6StructVAA0B4EnumOtcfc'
+    - '_$s4main7MyClassCMa'
+    - '_$s4main7MyClassCMm'
+    - '_$s4main7MyClassCMn'
+    - '_$s4main7MyClassCN'
+    - '_$s4main7MyClassCfD'
+    - '_$s4main7MyClassCfd'
+    - '_$s4main8MyStructVMa'
+    - '_$s4main8MyStructVMn'
+    - '_$s4main8MyStructVN'
+    - '_$s5Inner4main10MyProtocolPTl'
+    - __mh_execute_header
+    - _main
+    - '_$sBi64_WV'
+    - '_$sBoWV'
+    - '_$sSS21_builtinStringLiteral17utf8CodeUnitCount7isASCIISSBp_BwBi1_tcfC'
+    - '_$sSSN'
+    - '_$sSaMa'
+    - '_$ss27_allocateUninitializedArrayySayxG_BptBwlF'
+    - '_$ss5print_9separator10terminatoryypd_S2StF'
+    - '_$sypN'
+    - '_$sytWV'
+    - '_OBJC_CLASS_$__TtCs12_SwiftObject'
+    - '_OBJC_METACLASS_$__TtCs12_SwiftObject'
+    - __objc_empty_cache
+    - _objc_opt_self
+    - _swift_allocObject
+    - _swift_allocateGenericClassMetadata
+    - _swift_allocateGenericValueMetadata
+    - _swift_bridgeObjectRelease
+    - _swift_checkMetadataState
+    - _swift_deallocClassInstance
+    - _swift_deallocObject
+    - _swift_getAssociatedTypeWitness
+    - _swift_getGenericMetadata
+    - _swift_initClassMetadata2
+    - _swift_release
+    - _swift_retain
+    - dyld_stub_binder
+    - '_$s4main12Conformance2V5innerSivM.resume.0'
+    - '_$s4main12Conformance2V5innerACSi_tcfcfA_'
+    - '_$s4main12Conformance2V5innerACSi_tcfC'
+    - '_$s4main12Conformance2VACycfC'
+    - '_$s4main12Conformance2VAA10MyProtocolA2aDP5inner5InnerQzvgTW'
+    - '_$s4main3AppVAAyyFZ'
+    - '_$ss27_finalizeUninitializedArrayySayxGABnlF'
+    - '_$ss5print_9separator10terminatoryypd_S2StFfA0_'
+    - '_$ss5print_9separator10terminatoryypd_S2StFfA1_'
+    - '_$s4main3AppVACycfC'
+    - '_$s4main3AppV5$mainyyFZ'
+    - '_$s4main3AppVMa'
+    - '_$sSa12_endMutationyyF'
+    - '_$s4main7MyClassC1iSivg'
+    - '_$s4main7MyClassC2msAA0B6StructVvg'
+    - '_$s4main7MyClassC2meAA0B4EnumOvg'
+    - '_$s4main6MyEnumOWOy'
+    - '_$s4main6MyEnumOWOe'
+    - '_$s4main6MyEnumOWOh'
+    - '_$s4main11ConformanceV5innerSivM.resume.0'
+    - '_$s4main11ConformanceV5innerACSi_tcfcfA_'
+    - '_$s4main11ConformanceV5innerACSi_tcfC'
+    - '_$s4main11ConformanceVACycfC'
+    - '_$s4main11ConformanceVAA10MyProtocolA2aDP5inner5InnerQzvgTW'
+    - '_$s4main8MyStructVACycfC'
+    - '_$s4main14MyGenericClassC1txvg'
+    - '_$s4main14MyGenericClassC1i5InnerQzvg'
+    - '_$s4main14MyGenericClassC3mgsAA0bC6StructVyxGvg'
+    - '_$s4main14MyGenericClassC3mgeAA0bC4EnumOyxGvg'
+    - '_$s4main13MyGenericEnumOyxGAA0B8ProtocolRzlWOh'
+    - '_$s4main15MyGenericStructVACyxGycfC'
+    - '_$s4main16makeSomeClosures1tyycx_tAA10MyProtocolRzlFyycfU_'
+    - '_$s4main16makeSomeClosures1tyycx_tAA10MyProtocolRzlFyycfU_TA'
+    - '_$s4main6MyEnumOwCP'
+    - '_$s4main6MyEnumOwxx'
+    - '_$s4main6MyEnumOwcp'
+    - '_$s4main6MyEnumOwca'
+    - ___swift_memcpy9_8
+    - '_$s4main6MyEnumOwta'
+    - '_$s4main6MyEnumOwet'
+    - '_$s4main6MyEnumOwst'
+    - '_$s4main6MyEnumOwug'
+    - '_$s4main6MyEnumOwup'
+    - '_$s4main6MyEnumOwui'
+    - '_$s4main14MyGenericClassCMi'
+    - '_$s4main14MyGenericClassCMr'
+    - '_$s4main15MyGenericStructVMi'
+    - '_$s4main13MyGenericEnumOMi'
+    - ___swift_initWithCopy_strong
+    - ___swift_destroy_strong
+    - ___swift_assignWithCopy_strong
+    - ___swift_memcpy8_8
+    - ___swift_assignWithTake_strong
+    - '_$s4main13MyGenericEnumOwet'
+    - '_$s4main13MyGenericEnumOwst'
+    - '_$s4main13MyGenericEnumOwug'
+    - '_$s4main13MyGenericEnumOwup'
+    - '_$s4main13MyGenericEnumOwui'
+    - ___swift_instantiateGenericMetadata
+    - ___chkstk_darwin
+    - ___chkstk_darwin_llvm_probe
+    - ___chkstk_darwin_probe
+    - ____chkstk_darwin
+    - '_$s4mainMXM'
+    - '_$s4main3AppVMn'
+    - '_$s4main7MyClassC1iSivpWvd'
+    - '_$s4main7MyClassC2msAA0B6StructVvpWvd'
+    - '_$s4main7MyClassC2meAA0B4EnumOvpWvd'
+    - '_$s4main14MyGenericClassC3mgsAA0bC6StructVyxGvpWvd'
+    - '_$s4main15MyGenericStructVMP'
+    - '_$s4main13MyGenericEnumOMP'
+    - ___swift_reflection_version
+    - _symbolic Si
+    - _symbolic _____ 4main12Conformance2V
+    - '_symbolic $s4main10MyProtocolP'
+    - _symbolic _____ 4main3AppV
+    - _symbolic x
+    - _symbolic B0
+    - _symbolic _____ 4main11ConformanceV
+    - _symbolic _____ 4main7MyClassC
+    - _symbolic _____ 4main8MyStructV
+    - _symbolic _____ 4main6MyEnumO
+    - _symbolic _____ 4main14MyGenericClassC
+    - _symbolic 5Inner_____Qz 4main10MyProtocolP
+    - _symbolic _____yxG 4main15MyGenericStructV
+    - _symbolic _____yxG 4main13MyGenericEnumO
+    - _symbolic _____ 4main15MyGenericStructV
+    - _symbolic _____ 4main13MyGenericEnumO
+    - _symbolic _____yxG 4main14MyGenericClassC
+    - '_$s4main12Conformance2VAA10MyProtocolAAMA'
+    - '_$s4main11ConformanceVAA10MyProtocolAAMA'
+    - '_$s4main12Conformance2VMF'
+    - '_$s4main3AppVMF'
+    - '_$s4main10MyProtocol_pMF'
+    - '_$s4main7MyClassCMF'
+    - '_$s4main11ConformanceVMF'
+    - '_$s4main8MyStructVMF'
+    - '_$s4main6MyEnumOMF'
+    - '_$s4main14MyGenericClassCMF'
+    - '_$s4main15MyGenericStructVMF'
+    - '_$s4main13MyGenericEnumOMF'
+    - '_$s4main6MyEnumOMB'
+    - '_$s4main12Conformance2VMf'
+    - '_$s4main3AppVMf'
+    - '_$s4main3AppVN'
+    - '_$s4main11ConformanceVMf'
+    - '_$s4main8MyStructVMf'
+    - '_$s4main6MyEnumOWV'
+    - '_$s4main6MyEnumOMf'
+    - ___unnamed_23
+    - '_$s4main14MyGenericClassCMP'
+    - '_$s4main13MyGenericEnumOWV'
+    - __METACLASS_DATA__TtC4main7MyClass
+    - __IVARS__TtC4main7MyClass
+    - __DATA__TtC4main7MyClass
+    - __IVARS__TtC4main14MyGenericClass
+    - __dyld_private
+    - '_$s4main7MyClassCMf'
+    - '_$s4main14MyGenericClassCMI'
+    - '_$s4main15MyGenericStructVMI'
+    - '_$s4main13MyGenericEnumOMI'
+    - '/tmp/main-1.swiftmodule'
+    - '/Users/shubham/Development/test76973336/final2objfiletest/'
+    - test.swift
+    - '/tmp/test-1.o'
+    - '_$s4main12Conformance2V5innerSivpfi'
+    - '_$s4main12Conformance2V5innerSivg'
+    - '_$s4main12Conformance2V5innerSivs'
+    - '_$s4main12Conformance2V5innerSivM'
+    - '_$s4main12Conformance2V5innerSivM.resume.0'
+    - '_$s4main12Conformance2V5innerACSi_tcfcfA_'
+    - '_$s4main12Conformance2V5innerACSi_tcfC'
+    - '_$s4main12Conformance2VACycfC'
+    - '_$s4main12Conformance2VAA10MyProtocolA2aDP5inner5InnerQzvgTW'
+    - '_$s4main3AppVAAyyFZ'
+    - '_$ss27_finalizeUninitializedArrayySayxGABnlF'
+    - '_$ss5print_9separator10terminatoryypd_S2StFfA0_'
+    - '_$ss5print_9separator10terminatoryypd_S2StFfA1_'
+    - '_$s4main3AppVACycfC'
+    - '_$s4main3AppV5$mainyyFZ'
+    - _main
+    - '_$s4main12Conformance2VMa'
+    - '_$s4main3AppVMa'
+    - '_$sSa12_endMutationyyF'
+    - '_$s4main12Conformance2VAA10MyProtocolAAMc'
+    - '_$s4main12Conformance2V5innerSivpMV'
+    - '_$s4mainMXM'
+    - '_$s4main12Conformance2VMn'
+    - '_$s4main3AppVMn'
+    - _symbolic Si
+    - _symbolic _____ 4main12Conformance2V
+    - '_symbolic $s4main10MyProtocolP'
+    - _symbolic _____ 4main3AppV
+    - '_$s4main12Conformance2VAA10MyProtocolAAMA'
+    - '_$s4main12Conformance2VMF'
+    - '_$s4main3AppVMF'
+    - '_$s4main12Conformance2VMf'
+    - '_$s4main12Conformance2VN'
+    - '_$s4main3AppVMf'
+    - '_$s4main3AppVN'
+    - '_$s4main12Conformance2VAA10MyProtocolAAWP'
+    - reflection_metadata.swift
+    - '/tmp/reflection_metadata-1.o'

llvm/test/tools/dsymutil/Inputs/reflection_metadata.yaml

+# How to generate this file:
+# 1. First take a swift file and run xcrun swiftc -g -v file.swift 
+# secondfile.swift, make sure the two swift files are in a short path like /tmp/
+
+# 2. Now you can see what the driver does, generate the object files in the 
+# tmp directory
+
+# 3. Run obj2yaml on object file to create a yaml file
+
+# 4. I ran delta to reduce this file.
+
+--- !mach-o
+FileHeader:
+  magic:           0xFEEDFACF
+  cputype:         0x1000007
+  cpusubtype:      0x3
+  filetype:        0x1
+  ncmds:           8
+  sizeofcmds:      2800
+  flags:           0x2000
+  reserved:        0x0
+LoadCommands:
+  - cmd:             LC_SEGMENT_64
+    cmdsize:         2552
+    segname:         ''
+    vmaddr:          0
+    vmsize:          21352
+    fileoff:         2832
+    filesize:        20967
+    maxprot:         7
+    initprot:        7
+    nsects:          31
+    flags:           0
+    Sections:
+      - sectname:        __text
+        segname:         __TEXT
+        addr:            0x0
+        size:            4571
+        offset:          0xB10
+        align:           4
+        reloff:          0x5CF8
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+        flags:           0x80000400
+        reserved1:       0x0
+        reserved2:       0x0
+        relocations:
+          - address:         0x11A1
+            symbolnum:       142
+            pcrel:           true
+            length:          2
+            extern:          true
+            type:            1
+            scattered:       false
+            value:           0
+      - sectname:        __swift5_typeref
+        segname:         __TEXT
+        addr:            0x11DC
+        size:            117
+        offset:          0x1CEC
+        align:           1
+        reloff:          0x5F48
+        nreloc:          22
+        flags:           0x10000000
+        reserved1:       0x0
+        reserved2:       0x0
+        content:         7800423000005369000001FFFFFFFF002473346D61696E31304D7950726F746F636F6C50000001FFFFFFFF0001FFFFFFFF0001FFFFFFFF0001FFFFFFFF0035496E6E657201F9FFFFFF517A0001FFFFFFFF797847000001FFFFFFFF797847000001FFFFFFFF0001FFFFFFFF0001FFFFFFFF79784700
+        relocations:
+          - address:         0x6D
+            symbolnum:       163
+            pcrel:           false
+            length:          2
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+      - sectname:        __swift5_capture
+        segname:         __TEXT
+        addr:            0x1254
+        size:            24
+        offset:          0x1D64
+        align:           2
+        reloff:          0x5FF8
+        nreloc:          6
+        flags:           0x10000000
+        reserved1:       0x0
+        reserved2:       0x0
+        content:         010000000100000002000000F4FFFFFFF0FFFFFFECFFFFFF
+        relocations:
+          - address:         0x14
+            symbolnum:       29
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+      - sectname:        __swift5_reflstr
+        segname:         __TEXT
+        addr:            0x17D8
+        size:            37
+        offset:          0x22E8
+        align:           0
+        reloff:          0x0
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llvm/test/tools/dsymutil/Inputs/test.yaml

+# How to generate this file:
+# 1. First take a swift file and run xcrun swiftc -g -v file.swift 
+# secondfile.swift, make sure the two swift files are in a short path like /tmp/
+
+# 2. Now you can see what the driver does, generate the object files in the 
+# tmp directory
+
+# 3. Run obj2yaml on object file to create a yaml file
+
+# 4. I ran delta to reduce this file.
+
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+    - '_$s4mainMXM'
+    - '_$sSa12_endMutationyyF'
+    - '_$ss5print_9separator10terminatoryypd_S2StF'
+    - '_$ss27_allocateUninitializedArrayySayxG_BptBwlF'
+    - '_$ss27_finalizeUninitializedArrayySayxGABnlF'
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+    - l___unnamed_5
+    - l___unnamed_4
+    - '_$s4main12Conformance2V5innerSivM.resume.0'
+    - ''
+    - ''
+    - ''
+    - ''
+    - ''
+    - ''
+    - ''

llvm/test/tools/dsymutil/X86/reflection-dump.test

+RUN: rm -rf %t.dir && mkdir -p %t.dir/tmp
+RUN: cp %p/../Inputs/main.yaml %t.dir
+RUN: cp %p/../Inputs/test.yaml %t.dir
+RUN: cp %p/../Inputs/reflection_metadata.yaml %t.dir
+RUN: yaml2obj %p/../Inputs/main.yaml -o %t.dir/main
+RUN: yaml2obj %p/../Inputs/test.yaml -o %t.dir/tmp/test-1.o
+RUN: yaml2obj %p/../Inputs/reflection_metadata.yaml -o %t.dir/tmp/reflection_metadata-1.o
+
+RUN: dsymutil -oso-prepend-path=%t.dir %t.dir/main -o %t.dir/main.dSYM
+RUN: llvm-objdump -s %t.dir/main.dSYM/Contents/Resources/DWARF/main | FileCheck %s
+
+CHECK: Contents of section __DWARF,__swift5_typeref:
+CHECK-NEXT:  10000e000 53690000 01ffffff ff002473 346d6169  Si........$s4mai
+CHECK-NEXT:  10000e010 6e31304d 7950726f 746f636f 6c500000  n10MyProtocolP..
+CHECK-NEXT:  10000e020 01ffffff ff007800 42300000 53690000  ......x.B0..Si..
+CHECK-NEXT:  10000e030 01ffffff ff002473 346d6169 6e31304d  ......$s4main10M
+CHECK-NEXT:  10000e040 7950726f 746f636f 6c500000 01ffffff  yProtocolP......
+
+CHECK: Contents of section __DWARF,__swift5_reflstr:
+CHECK-NEXT:  10000e09b 496e6e65 7200696e 6e657200 496e6e65  Inner.inner.Inne
+CHECK-NEXT:  10000e0ab 72006900 6d73006d 6500696e 6e657200  r.i.ms.me.inner.
+CHECK-NEXT:  10000e0bb 43004900 74006d67 73006d67 65004743  C.I.t.mgs.mge.GC
+CHECK-NEXT:  10000e0cb 00
+
+CHECK: Contents of section __DWARF,__swift5_assocty:
+CHECK-NEXT:  10000e0cc 00000000 fcffffff 01000000 08000000  ................
+CHECK-NEXT:  10000e0dc f0ffffff ecffffff 00000000 fcffffff  ................
+CHECK-NEXT:  10000e0ec 01000000 08000000 f0ffffff ecffffff  ................
+
+CHECK: Contents of section __DWARF,__swift5_fieldmd:
+CHECK-NEXT:  10000e0fc 00000000 00000000 00000c00 01000000  ................
+CHECK-NEXT:  10000e10c 02000000 ecffffff e8ffffff 00000000  ................
+CHECK-NEXT:  10000e11c 00000000 00000c00 00000000 00000000  ................
+CHECK-NEXT:  10000e12c 00000000 04000c00 00000000 00000000  ................
+
+CHECK: Contents of section __DWARF,__swift5_capture:
+CHECK-NEXT:  10000e22c 01000000 01000000 02000000 f4ffffff  ................
+CHECK-NEXT:  10000e23c f0ffffff ecffffff                    ........
+
+CHECK: Contents of section __DWARF,__swift5_builtin:
+CHECK-NEXT:  10000e244 00000000 09000000 08000100 10000000  ................
+CHECK-NEXT:  10000e254 fe000000                             ....

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/BinaryFormat/MachO.h"
+#include "llvm/BinaryFormat/Swift.h"
 #include "llvm/CodeGen/AccelTable.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/DIE.h"
 #include "llvm/CodeGen/NonRelocatableStringpool.h"
 #include "llvm/Config/config.h"
 #include "llvm/DWARFLinker/DWARFLinkerDeclContext.h"
 #include "llvm/DebugInfo/DIContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h"
bool DwarfLinkerForBinary::createStreamer(const Triple &TheTriple,
   Streamer = std::make_unique<DwarfStreamer>(
       Options.FileType, OutFile, Options.Translator,
       [&](const Twine &Error, StringRef Context, const DWARFDie *) {
         error(Error, Context);
       },
       [&](const Twine &Warning, StringRef Context, const DWARFDie *) {
         warn(Warning, Context);
       });
-  return Streamer->init(TheTriple);
+  return Streamer->init(TheTriple, "__DWARF");
 }
 
 ErrorOr<const object::ObjectFile &>
 DwarfLinkerForBinary::loadObject(const DebugMapObject &Obj,
                                  const Triple &Triple) {
   auto ObjectEntry =
       BinHolder.getObjectEntry(Obj.getObjectFilename(), Obj.getTimestamp());
   if (!ObjectEntry) {
if (Error NewE = handleErrors(
       return errorToErrorCode(std::move(NewE));
 
     return *ObjectsForLinking.back();
   }
 
   return ErrorOrObj.getError();
 }
 
+static bool binaryHasSwiftReflectionSections(const DebugMap &Map,
+                                             const LinkOptions &Options,
+                                             BinaryHolder &BinHolder) {
+  // If the input binary has swift5 reflection sections, there is no need to
+  // copy them to the .dSYM. Only copy them for binaries where the linker
+  // omitted the reflection metadata.
+  if (!Map.getBinaryPath().empty() &&
+      Options.FileType == OutputFileType::Object) {
+
+    auto ObjectEntry = BinHolder.getObjectEntry(Map.getBinaryPath());
+    // If ObjectEntry or Object has an error, no binary exists, therefore no
+    // reflection sections exist.
+    if (!ObjectEntry) {
+      // Any errors will be diagnosed later in the main loop, ignore them here.
+      llvm::consumeError(ObjectEntry.takeError());
+      return false;
+    }
+
+    auto Object =
+        ObjectEntry->getObjectAs<object::MachOObjectFile>(Map.getTriple());
+    if (!Object) {
+      // Any errors will be diagnosed later in the main loop, ignore them here.
+      llvm::consumeError(Object.takeError());
+      return false;
+    }
+
+    for (auto &Section : Object->sections()) {
+      llvm::Expected<llvm::StringRef> NameOrErr =
+          Object->getSectionName(Section.getRawDataRefImpl());
+      if (!NameOrErr) {
+        llvm::consumeError(NameOrErr.takeError());
+        continue;
+      }
+      NameOrErr->consume_back("__TEXT");
+      if (Object->mapReflectionSectionNameToEnumValue(*NameOrErr) !=
+          llvm::swift::Swift5ReflectionSectionKind::Unknown) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+static void
+copySwiftReflectionMetadata(const llvm::dsymutil::DebugMapObject *Obj,
+                            DwarfStreamer *Streamer) {
+  auto OF =
+      llvm::object::ObjectFile::createObjectFile(Obj->getObjectFilename());
+  if (!OF) {
+    llvm::consumeError(OF.takeError());
+    return;
+  } else if (auto *MO =
+                 dyn_cast<llvm::object::MachOObjectFile>(OF->getBinary())) {
+    for (auto &Section : OF->getBinary()->sections()) {
+      llvm::Expected<llvm::StringRef> NameOrErr =
+          MO->getSectionName(Section.getRawDataRefImpl());
+      if (!NameOrErr) {
+        llvm::consumeError(NameOrErr.takeError());
+        continue;
+      }
+      llvm::Expected<llvm::StringRef> SectionContents = Section.getContents();
+      if (SectionContents) {
+        NameOrErr->consume_back("__TEXT");
+        Streamer->emitSwiftReflectionSection(
+            MO->mapReflectionSectionNameToEnumValue(*NameOrErr),
+            *SectionContents, Section.getAlignment(), Section.getSize());
+      }
+    }
+  }
+}
+
 bool DwarfLinkerForBinary::link(const DebugMap &Map) {
   if (!createStreamer(Map.getTriple(), OutFile))
     return false;
 
   ObjectsForLinking.clear();
   ContextForLinking.clear();
   AddressMapForLinking.clear();
 
GeneralLinker.setObjFileLoader(
           }
 
           return ErrorOrObj.getError();
         }
 
         llvm_unreachable("Unhandled DebugMap object");
       });
   GeneralLinker.setSwiftInterfacesMap(&ParseableSwiftInterfaces);
+  bool ReflectionSectionsPresentInBinary = false;
+  // If there is no output specified, no point in checking the binary for swift5
+  // reflection sections.
+  if (!Options.NoOutput) {
+    ReflectionSectionsPresentInBinary =
+        binaryHasSwiftReflectionSections(Map, Options, BinHolder);
+  }
 
   for (const auto &Obj : Map.objects()) {
+    // If there is no output specified or the reflection sections are present in
+    // the Input binary, there is no need to copy the Swift Reflection Metadata
+    if (!Options.NoOutput && !ReflectionSectionsPresentInBinary)
+      copySwiftReflectionMetadata(Obj.get(), Streamer.get());
+
     // N_AST objects (swiftmodule files) should get dumped directly into the
     // appropriate DWARF section.
     if (Obj->getType() == MachO::N_AST) {
       if (Options.Verbose)
         outs() << "DEBUG MAP OBJECT: " << Obj->getObjectFilename() << "\n";
 
       StringRef File = Obj->getObjectFilename();
       auto ErrorOrMem = MemoryBuffer::getFile(File);
if (Obj->getType() == MachO::N_AST) {
       }
 
       // Copy the module into the .swift_ast section.
       if (!Options.NoOutput)
         Streamer->emitSwiftAST((*ErrorOrMem)->getBuffer());
 
       continue;
     }
-
     if (auto ErrorOrObj = loadObject(*Obj, Map, RL))
       GeneralLinker.addObjectFile(*ErrorOrObj);
     else {
       ObjectsForLinking.push_back(std::make_unique<DWARFFile>(
           Obj->getObjectFilename(), nullptr, nullptr,
           Obj->empty() ? Obj->getWarnings() : EmptyWarnings));
       GeneralLinker.addObjectFile(*ObjectsForLinking.back());
     }