[DWP] Refactoring llvm-dwp in to a library.

[ayermolo]

Summary

This is a step1, mechanical refactor, of moving the bulk of llvm-dwp functionality in to a library. This should allow other tools, like BOLT, to re-use some of the llvm-dwp functionality.

[ayermolo]

Removing some includes.

[ayermolo]

one more

[dblaikie]

No dobut we've discussed this before, but could you refresh my memory on why bolt needs access to dwp rewriting?

Is it possible we could emit bolt-compatible DWARF instead (I imagine we'll want to do this for Propeller anyway) - for instance if Bolt can change the length of a code range (so DWARF's use of offsets relative to known addresses would become inaccurate) perhaps when code generating we could know that those ranges could change and instead emit addresses rather than offsets? Thoese addresses would go in the address pool and be modifiable by Bolt without having to rewrite the dwp (this will significantly increase the .o/executable size of the DWARF due to the use of more address relocations, but may still be worthwhile/the right direction, possibly).

[ayermolo]

In D106198#2885179, @dblaikie wrote:

No dobut we've discussed this before, but could you refresh my memory on why bolt needs access to dwp rewriting?

Is it possible we could emit bolt-compatible DWARF instead (I imagine we'll want to do this for Propeller anyway) - for instance if Bolt can change the length of a code range (so DWARF's use of offsets relative to known addresses would become inaccurate) perhaps when code generating we could know that those ranges could change and instead emit addresses rather than offsets? Thoese addresses would go in the address pool and be modifiable by Bolt without having to rewrite the dwp (this will significantly increase the .o/executable size of the DWARF due to the use of more address relocations, but may still be worthwhile/the right direction, possibly).

The main motivation is to simplify the compilation pipeline, with some speed up. Right now we build pre-bolt binary with DWO sections in .dwo/.o, then we run bolt which writes out modified .dwo. Final step we run llvm-dwp which reads all of this in, then writes out again. With bolt supporting dwp as output we can short circuit running llvm-dwp and just write it out directly.
Supporting DWP as input, is mainly just to make it feature complete. It was a low hanging fruit.

[ayermolo]

I guess on thing that can simplify BOLT. In some cases skeleton CU doesn't have DW_AT_GNU_ranges_base. In general bolt converts DW_AT_low_pc/DW_AT_high_pc to ranges. If Skeleton CU doesn't have DW_AT_GNU_ranges_base we replace DW_AT_low_pc with it. Except DW_AT_GNU_ranges_base doesn't fit in 8 bits. So Abbrev section can't be patched, and I ended up re-writing it. Not sure what can be done there. Maybe llvm can always emit DW_AT_GNU_ranges_base in Skeleton CU?

[dblaikie]

In D106198#2887577, @ayermolo wrote:

In D106198#2885179, @dblaikie wrote:

No dobut we've discussed this before, but could you refresh my memory on why bolt needs access to dwp rewriting?

Is it possible we could emit bolt-compatible DWARF instead (I imagine we'll want to do this for Propeller anyway) - for instance if Bolt can change the length of a code range (so DWARF's use of offsets relative to known addresses would become inaccurate) perhaps when code generating we could know that those ranges could change and instead emit addresses rather than offsets? Thoese addresses would go in the address pool and be modifiable by Bolt without having to rewrite the dwp (this will significantly increase the .o/executable size of the DWARF due to the use of more address relocations, but may still be worthwhile/the right direction, possibly).

The main motivation is to simplify the compilation pipeline, with some speed up. Right now we build pre-bolt binary with DWO sections in .dwo/.o, then we run bolt which writes out modified .dwo. Final step we run llvm-dwp which reads all of this in, then writes out again. With bolt supporting dwp as output we can short circuit running llvm-dwp and just write it out directly.
Supporting DWP as input, is mainly just to make it feature complete. It was a low hanging fruit.

Is there no chance of the compiler knowing ahead of time what the cut-points are and emitting DWARF that already accounts for that?

If it's only about ranges - yeah, we could have a mode where /everything/ is described by a range, though Split DWARF doesn't provide a way for DIEs in the dwo to references ranges in the linked binary (they reference .debug_rnglists.dwo instead) - even if those ranges used startx_endx encodings, you couldn't change the number of ranges needed to describe something (so you couldn't split a contiguous sequence into a range by only modifying the linked debug info, without touching the .dwo/dwp). So, yeah, without something more like Propeller, where the cut-points are known at compile-time, modifying dwo/dwp seems necessary.

Thanks for walking me through it again.

Perhaps this should be in a subdirectory of "DebugInfo" rather than in its own top level directory? Eh, I guess if DWARFLinker is in its own top-level directory then so could this.

Could you split the change up a bit - do some/all of the library refactoring in-place before moving directories? It'd make it easier to separate/undertsand the changes.

[ayermolo]

Breaking up in to two patches. This one just refactores code in to seperate files.

[ayermolo]

minor cleanup

[ayermolo]

Not sure why reviews tags both llvm-dwp and DWPLibrary.cpp as copied from each other.

[ayermolo]

In D106198#2887694, @dblaikie wrote:

In D106198#2887577, @ayermolo wrote:

In D106198#2885179, @dblaikie wrote:

No dobut we've discussed this before, but could you refresh my memory on why bolt needs access to dwp rewriting?

Is it possible we could emit bolt-compatible DWARF instead (I imagine we'll want to do this for Propeller anyway) - for instance if Bolt can change the length of a code range (so DWARF's use of offsets relative to known addresses would become inaccurate) perhaps when code generating we could know that those ranges could change and instead emit addresses rather than offsets? Thoese addresses would go in the address pool and be modifiable by Bolt without having to rewrite the dwp (this will significantly increase the .o/executable size of the DWARF due to the use of more address relocations, but may still be worthwhile/the right direction, possibly).

The main motivation is to simplify the compilation pipeline, with some speed up. Right now we build pre-bolt binary with DWO sections in .dwo/.o, then we run bolt which writes out modified .dwo. Final step we run llvm-dwp which reads all of this in, then writes out again. With bolt supporting dwp as output we can short circuit running llvm-dwp and just write it out directly.
Supporting DWP as input, is mainly just to make it feature complete. It was a low hanging fruit.

Is there no chance of the compiler knowing ahead of time what the cut-points are and emitting DWARF that already accounts for that?

If it's only about ranges - yeah, we could have a mode where /everything/ is described by a range, though Split DWARF doesn't provide a way for DIEs in the dwo to references ranges in the linked binary (they reference .debug_rnglists.dwo instead) - even if those ranges used startx_endx encodings, you couldn't change the number of ranges needed to describe something (so you couldn't split a contiguous sequence into a range by only modifying the linked debug info, without touching the .dwo/dwp). So, yeah, without something more like Propeller, where the cut-points are known at compile-time, modifying dwo/dwp seems necessary.

Thanks for walking me through it again.

Perhaps this should be in a subdirectory of "DebugInfo" rather than in its own top level directory? Eh, I guess if DWARFLinker is in its own top-level directory then so could this.

Could you split the change up a bit - do some/all of the library refactoring in-place before moving directories? It'd make it easier to separate/undertsand the changes.

Bolt introduces new ranges by splitting hot/cold sections, etc.
Side note. Currently BOLT only supports DWARF 4. I know GCC turned on DWARF 5 by default. Are there plans on llvm side?

[dblaikie]

In D106198#2888141, @ayermolo wrote:

In D106198#2887694, @dblaikie wrote:

In D106198#2887577, @ayermolo wrote:

In D106198#2885179, @dblaikie wrote:

No dobut we've discussed this before, but could you refresh my memory on why bolt needs access to dwp rewriting?

Is it possible we could emit bolt-compatible DWARF instead (I imagine we'll want to do this for Propeller anyway) - for instance if Bolt can change the length of a code range (so DWARF's use of offsets relative to known addresses would become inaccurate) perhaps when code generating we could know that those ranges could change and instead emit addresses rather than offsets? Thoese addresses would go in the address pool and be modifiable by Bolt without having to rewrite the dwp (this will significantly increase the .o/executable size of the DWARF due to the use of more address relocations, but may still be worthwhile/the right direction, possibly).

The main motivation is to simplify the compilation pipeline, with some speed up. Right now we build pre-bolt binary with DWO sections in .dwo/.o, then we run bolt which writes out modified .dwo. Final step we run llvm-dwp which reads all of this in, then writes out again. With bolt supporting dwp as output we can short circuit running llvm-dwp and just write it out directly.
Supporting DWP as input, is mainly just to make it feature complete. It was a low hanging fruit.

Is there no chance of the compiler knowing ahead of time what the cut-points are and emitting DWARF that already accounts for that?

If it's only about ranges - yeah, we could have a mode where /everything/ is described by a range, though Split DWARF doesn't provide a way for DIEs in the dwo to references ranges in the linked binary (they reference .debug_rnglists.dwo instead) - even if those ranges used startx_endx encodings, you couldn't change the number of ranges needed to describe something (so you couldn't split a contiguous sequence into a range by only modifying the linked debug info, without touching the .dwo/dwp). So, yeah, without something more like Propeller, where the cut-points are known at compile-time, modifying dwo/dwp seems necessary.

Thanks for walking me through it again.

Perhaps this should be in a subdirectory of "DebugInfo" rather than in its own top level directory? Eh, I guess if DWARFLinker is in its own top-level directory then so could this.

Could you split the change up a bit - do some/all of the library refactoring in-place before moving directories? It'd make it easier to separate/undertsand the changes.

Bolt introduces new ranges by splitting hot/cold sections, etc.
Side note. Currently BOLT only supports DWARF 4. I know GCC turned on DWARF 5 by default. Are there plans on llvm side?

Haven't heard any particular discussions - Google switched to DWARFv5 by default several months ago, haven't heard Sony or Apple discussing it.

llvm/tools/llvm-dwp/CMakeLists.txt

9

I'd probably call this DWP.cpp to match DWP.h?

[ayermolo]

change to DWP.cpp

[dblaikie]

Sounds good

[ayermolo]

fix clang-tidy

[ayermolo]

rebase on tot

[ayermolo]

rebase on latest

[ayermolo]

@dblaikie can I land or should I wait for @jdoerfert
Looking at failures, they look unrelated

[dblaikie]

In D106198#2891643, @ayermolo wrote:

@dblaikie can I land or should I wait for @jdoerfert
Looking at failures, they look unrelated

nah, that's fine - you can go ahead. Please update the patch description/commit message to reflect that this patch isn't creating a library, but is the preliminary changes within the llvm-dwp binary.

llvm/include/llvm/DWP/DWP.h

+#ifndef TOOLS_LLVM_DWP_DWP_H
+#define TOOLS_LLVM_DWP_DWP_H
+
+#include "DWPStringPool.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/Error.h"
+#include <deque>
+#include <vector>
+
+namespace llvm {
+struct UnitIndexEntry {
+  DWARFUnitIndex::Entry::SectionContribution Contributions[8];
+  std::string Name;
+  std::string DWOName;
+  StringRef DWPName;
+};
+
+// Holds data for Skeleton, Split Compilation, and Type Unit Headers (only in
+// v5) as defined in Dwarf 5 specification, 7.5.1.2, 7.5.1.3 and Dwarf 4
+// specification 7.5.1.1.
+struct InfoSectionUnitHeader {
+  // unit_length field. Note that the type is uint64_t even in 32-bit dwarf.
+  uint64_t Length = 0;
+
+  // version field.
+  uint16_t Version = 0;
+
+  // unit_type field. Initialized only if Version >= 5.
+  uint8_t UnitType = 0;
+
+  // address_size field.
+  uint8_t AddrSize = 0;
+
+  // debug_abbrev_offset field. Note that the type is uint64_t even in 32-bit
+  // dwarf. It is assumed to be 0.
+  uint64_t DebugAbbrevOffset = 0;
+
+  // dwo_id field. This resides in the header only if Version >= 5.
+  // In earlier versions, it is read from DW_AT_GNU_dwo_id.
+  Optional<uint64_t> Signature = None;
+
+  // Derived from the length of Length field.
+  dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
+
+  // The size of the Header in bytes. This is derived while parsing the header,
+  // and is stored as a convenience.
+  uint8_t HeaderSize = 0;
+};
+
+struct CompileUnitIdentifiers {
+  uint64_t Signature = 0;
+  const char *Name = "";
+  const char *DWOName = "";
+};
+
+Error write(MCStreamer &Out, ArrayRef<std::string> Inputs);
+
+unsigned getContributionIndex(DWARFSectionKind Kind, uint32_t IndexVersion);
+
+Error handleSection(
+    const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
+    const MCSection *StrSection, const MCSection *StrOffsetSection,
+    const MCSection *TypesSection, const MCSection *CUIndexSection,
+    const MCSection *TUIndexSection, const MCSection *InfoSection,
+    const object::SectionRef &Section, MCStreamer &Out,
+    std::deque<SmallString<32>> &UncompressedSections,
+    uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
+    StringRef &CurStrSection, StringRef &CurStrOffsetSection,
+    std::vector<StringRef> &CurTypesSection,
+    std::vector<StringRef> &CurInfoSection, StringRef &AbbrevSection,
+    StringRef &CurCUIndexSection, StringRef &CurTUIndexSection,
+    std::vector<std::pair<DWARFSectionKind, uint32_t>> &SectionLength);
+
+Expected<InfoSectionUnitHeader> parseInfoSectionUnitHeader(StringRef Info);
+
+void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
+                            MCSection *StrOffsetSection,
+                            StringRef CurStrSection,
+                            StringRef CurStrOffsetSection, uint16_t Version);
+
+Error buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
+                          const CompileUnitIdentifiers &ID, StringRef DWPName);
+
+void writeIndex(MCStreamer &Out, MCSection *Section,
+                ArrayRef<unsigned> ContributionOffsets,
+                const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
+                uint32_t IndexVersion);
+
+} // namespace llvm
+#endif // TOOLS_LLVM_DWP_DWP_H

llvm/include/llvm/DWP/DWPError.h

public:
   std::error_code convertToErrorCode() const override {
     llvm_unreachable("Not implemented");
   }
   static char ID;
 
 private:
   std::string Info;
 };
-}
+} // namespace llvm
 
 #endif

llvm/include/llvm/DWP/DWPStringPool.h

if (Pair.second) {
       Out.SwitchSection(Sec);
       Out.emitBytes(StringRef(Str, Length));
       Offset += Length;
     }
 
     return Pair.first->second;
   }
 };
-}
+} // namespace llvm
 
 #endif

llvm/lib/CMakeLists.txt

 add_subdirectory(LTO)
 add_subdirectory(MC)
 add_subdirectory(MCA)
 add_subdirectory(Object)
 add_subdirectory(ObjectYAML)
 add_subdirectory(Option)
 add_subdirectory(Remarks)
 add_subdirectory(DebugInfo)
+add_subdirectory(DWP)
 add_subdirectory(ExecutionEngine)
 add_subdirectory(Target)
 add_subdirectory(AsmParser)
 add_subdirectory(LineEditor)
 add_subdirectory(ProfileData)
 add_subdirectory(Passes)
 add_subdirectory(TextAPI)
 add_subdirectory(ToolDrivers)

llvm/lib/DWP/CMakeLists.txt

+add_llvm_component_library(LLVMDWP
+  DWPLibrary.cpp
+  DWPError.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/DWP
+
+  DEPENDS
+  intrinsics_gen
+)

llvm/lib/DWP/DWPError.cpp

-#include "DWPError.h"
+#include "llvm/DWP/DWPError.h"
 using namespace llvm;
 char DWPError::ID;

llvm/lib/DWP/DWPLibrary.cpp

 //===-- llvm-dwp.cpp - Split DWARF merging tool for llvm ------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // A utility for merging DWARF 5 Split DWARF .dwo files into .dwp (DWARF
 // package files).
 //
 //===----------------------------------------------------------------------===//
-#include "DWPError.h"
-#include "DWPStringPool.h"
-#include "llvm/ADT/MapVector.h"
-#include "llvm/ADT/Optional.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/DebugInfo/DWARF/DWARFContext.h"
-#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
-#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
-#include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
-#include "llvm/MC/MCAsmBackend.h"
-#include "llvm/MC/MCAsmInfo.h"
-#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/DWP/DWP.h"
+#include "llvm/DWP/DWPError.h"
 #include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCObjectFileInfo.h"
-#include "llvm/MC/MCObjectWriter.h"
-#include "llvm/MC/MCRegisterInfo.h"
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCTargetOptionsCommandFlags.h"
 #include "llvm/Object/Decompressor.h"
-#include "llvm/Object/ObjectFile.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/DataExtractor.h"
-#include "llvm/Support/Error.h"
-#include "llvm/Support/FileSystem.h"
-#include "llvm/Support/InitLLVM.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/MemoryBuffer.h"
-#include "llvm/Support/Path.h"
-#include "llvm/Support/TargetRegistry.h"
-#include "llvm/Support/TargetSelect.h"
-#include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/WithColor.h"
-#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::object;
 
 static mc::RegisterMCTargetOptionsFlags MCTargetOptionsFlags;
 
-cl::OptionCategory DwpCategory("Specific Options");
-static cl::list<std::string> InputFiles(cl::Positional, cl::ZeroOrMore,
-                                        cl::desc("<input files>"),
-                                        cl::cat(DwpCategory));
-
-static cl::list<std::string> ExecFilenames(
-    "e", cl::ZeroOrMore,
-    cl::desc("Specify the executable/library files to get the list of *.dwo from"),
-    cl::value_desc("filename"), cl::cat(DwpCategory));
-
-static cl::opt<std::string> OutputFilename(cl::Required, "o",
-                                           cl::desc("Specify the output file."),
-                                           cl::value_desc("filename"),
-                                           cl::cat(DwpCategory));
-
 // Returns the size of debug_str_offsets section headers in bytes.
 static uint64_t debugStrOffsetsHeaderSize(DataExtractor StrOffsetsData,
                                           uint16_t DwarfVersion) {
   if (DwarfVersion <= 4)
     return 0; // There is no header before dwarf 5.
   uint64_t Offset = 0;
   uint64_t Length = StrOffsetsData.getU32(&Offset);
   if (Length == llvm::dwarf::DW_LENGTH_DWARF64)
     return 16; // unit length: 12 bytes, version: 2 bytes, padding: 2 bytes.
   return 8;    // unit length: 4 bytes, version: 2 bytes, padding: 2 bytes.
 }
 
-// Holds data for Skeleton, Split Compilation, and Type Unit Headers (only in
-// v5) as defined in Dwarf 5 specification, 7.5.1.2, 7.5.1.3 and Dwarf 4
-// specification 7.5.1.1.
-struct InfoSectionUnitHeader {
-  // unit_length field. Note that the type is uint64_t even in 32-bit dwarf.
-  uint64_t Length = 0;
-
-  // version field.
-  uint16_t Version = 0;
-
-  // unit_type field. Initialized only if Version >= 5.
-  uint8_t UnitType = 0;
-
-  // address_size field.
-  uint8_t AddrSize = 0;
-
-  // debug_abbrev_offset field. Note that the type is uint64_t even in 32-bit
-  // dwarf. It is assumed to be 0.
-  uint64_t DebugAbbrevOffset = 0;
-
-  // dwo_id field. This resides in the header only if Version >= 5.
-  // In earlier versions, it is read from DW_AT_GNU_dwo_id.
-  Optional<uint64_t> Signature = None;
-
-  // Derived from the length of Length field.
-  dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
-
-  // The size of the Header in bytes. This is derived while parsing the header,
-  // and is stored as a convenience.
-  uint8_t HeaderSize = 0;
-};
-
-// Parse and return the header of an info section compile/type unit.
-static Expected<InfoSectionUnitHeader>
-parseInfoSectionUnitHeader(StringRef Info) {
-  InfoSectionUnitHeader Header;
-  Error Err = Error::success();
-  uint64_t Offset = 0;
-  DWARFDataExtractor InfoData(Info, true, 0);
-  std::tie(Header.Length, Header.Format) =
-      InfoData.getInitialLength(&Offset, &Err);
-  if (Err)
-    return make_error<DWPError>("cannot parse compile unit length: " +
-                                llvm::toString(std::move(Err)));
-
-  if (!InfoData.isValidOffset(Offset + (Header.Length - 1))) {
-    return make_error<DWPError>(
-        "compile unit exceeds .debug_info section range: " +
-        utostr(Offset + Header.Length) + " >= " + utostr(InfoData.size()));
-  }
-
-  Header.Version = InfoData.getU16(&Offset, &Err);
-  if (Err)
-    return make_error<DWPError>("cannot parse compile unit version: " +
-                                llvm::toString(std::move(Err)));
-
-  uint64_t MinHeaderLength;
-  if (Header.Version >= 5) {
-    // Size: Version (2), UnitType (1), AddrSize (1), DebugAbbrevOffset (4),
-    // Signature (8)
-    MinHeaderLength = 16;
-  } else {
-    // Size: Version (2), DebugAbbrevOffset (4), AddrSize (1)
-    MinHeaderLength = 7;
-  }
-  if (Header.Length < MinHeaderLength) {
-    return make_error<DWPError>("unit length is too small: expected at least " +
-                                utostr(MinHeaderLength) + " got " +
-                                utostr(Header.Length) + ".");
-  }
-  if (Header.Version >= 5) {
-    Header.UnitType = InfoData.getU8(&Offset);
-    Header.AddrSize = InfoData.getU8(&Offset);
-    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
-    Header.Signature = InfoData.getU64(&Offset);
-    if (Header.UnitType == dwarf::DW_UT_split_type) {
-      // Type offset.
-      MinHeaderLength += 4;
-      if (Header.Length < MinHeaderLength)
-        return make_error<DWPError>("type unit is missing type offset");
-      InfoData.getU32(&Offset);
-    }
-  } else {
-    // Note that, address_size and debug_abbrev_offset fields have switched
-    // places between dwarf version 4 and 5.
-    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
-    Header.AddrSize = InfoData.getU8(&Offset);
-  }
-
-  Header.HeaderSize = Offset;
-  return Header;
-}
-
-static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
-                                   MCSection *StrOffsetSection,
-                                   StringRef CurStrSection,
-                                   StringRef CurStrOffsetSection,
-                                   uint16_t Version) {
-  // Could possibly produce an error or warning if one of these was non-null but
-  // the other was null.
-  if (CurStrSection.empty() || CurStrOffsetSection.empty())
-    return;
-
-  DenseMap<uint64_t, uint32_t> OffsetRemapping;
-
-  DataExtractor Data(CurStrSection, true, 0);
-  uint64_t LocalOffset = 0;
-  uint64_t PrevOffset = 0;
-  while (const char *s = Data.getCStr(&LocalOffset)) {
-    OffsetRemapping[PrevOffset] =
-        Strings.getOffset(s, LocalOffset - PrevOffset);
-    PrevOffset = LocalOffset;
-  }
-
-  Data = DataExtractor(CurStrOffsetSection, true, 0);
-
-  Out.SwitchSection(StrOffsetSection);
-
-  uint64_t HeaderSize = debugStrOffsetsHeaderSize(Data, Version);
-  uint64_t Offset = 0;
-  uint64_t Size = CurStrOffsetSection.size();
-  // FIXME: This can be caused by bad input and should be handled as such.
-  assert(HeaderSize <= Size && "StrOffsetSection size is less than its header");
-  // Copy the header to the output.
-  Out.emitBytes(Data.getBytes(&Offset, HeaderSize));
-  while (Offset < Size) {
-    auto OldOffset = Data.getU32(&Offset);
-    auto NewOffset = OffsetRemapping[OldOffset];
-    Out.emitIntValue(NewOffset, 4);
-  }
-}
-
 static uint64_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
   uint64_t Offset = 0;
   DataExtractor AbbrevData(Abbrev, true, 0);
   while (AbbrevData.getULEB128(&Offset) != AbbrCode) {
     // Tag
     AbbrevData.getULEB128(&Offset);
     // DW_CHILDREN
     AbbrevData.getU8(&Offset);
     // Attributes
     while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
       ;
   }
   return Offset;
 }
 
-struct CompileUnitIdentifiers {
-  uint64_t Signature = 0;
-  const char *Name = "";
-  const char *DWOName = "";
-};
-
 static Expected<const char *>
 getIndexedString(dwarf::Form Form, DataExtractor InfoData, uint64_t &InfoOffset,
                  StringRef StrOffsets, StringRef Str, uint16_t Version) {
   if (Form == dwarf::DW_FORM_string)
     return InfoData.getCStr(&InfoOffset);
   uint64_t StrIndex;
   switch (Form) {
   case dwarf::DW_FORM_strx1:
getCUIdentifiers(InfoSectionUnitHeader &Header, StringRef Abbrev,
   auto Tag = static_cast<dwarf::Tag>(AbbrevData.getULEB128(&AbbrevOffset));
   if (Tag != dwarf::DW_TAG_compile_unit)
     return make_error<DWPError>("top level DIE is not a compile unit");
   // DW_CHILDREN
   AbbrevData.getU8(&AbbrevOffset);
   uint32_t Name;
   dwarf::Form Form;
   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
-         (Form = static_cast<dwarf::Form>(AbbrevData.getULEB128(&AbbrevOffset))) &&
+             (Form = static_cast<dwarf::Form>(
+                  AbbrevData.getULEB128(&AbbrevOffset))) &&
          (Name != 0 || Form != 0)) {
     switch (Name) {
     case dwarf::DW_AT_name: {
       Expected<const char *> EName = getIndexedString(
           Form, InfoData, Offset, StrOffsets, Str, Header.Version);
       if (!EName)
         return EName.takeError();
       ID.Name = *EName;
while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
     }
   }
   if (!Header.Signature)
     return make_error<DWPError>("compile unit missing dwo_id");
   ID.Signature = *Header.Signature;
   return ID;
 }
 
-struct UnitIndexEntry {
-  DWARFUnitIndex::Entry::SectionContribution Contributions[8];
-  std::string Name;
-  std::string DWOName;
-  StringRef DWPName;
-};
-
 static bool isSupportedSectionKind(DWARFSectionKind Kind) {
   return Kind != DW_SECT_EXT_unknown;
 }
 
+namespace llvm {
 // Convert an internal section identifier into the index to use with
 // UnitIndexEntry::Contributions.
-static unsigned getContributionIndex(DWARFSectionKind Kind,
-                                     uint32_t IndexVersion) {
+unsigned getContributionIndex(DWARFSectionKind Kind, uint32_t IndexVersion) {
   assert(serializeSectionKind(Kind, IndexVersion) >= DW_SECT_INFO);
   return serializeSectionKind(Kind, IndexVersion) - DW_SECT_INFO;
 }
+} // namespace llvm
 
 // Convert a UnitIndexEntry::Contributions index to the corresponding on-disk
 // value of the section identifier.
 static unsigned getOnDiskSectionId(unsigned Index) {
   return Index + DW_SECT_INFO;
 }
 
 static StringRef getSubsection(StringRef Section,
while (Data.isValidOffset(Offset)) {
         continue;
 
       Out.emitBytes(Types.substr(PrevOffset, C.Length));
       TypesOffset += C.Length;
     }
   }
 }
 
-static void
-writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
-                const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
-                uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
+static std::string buildDWODescription(StringRef Name, StringRef DWPName,
+                                       StringRef DWOName) {
+  std::string Text = "\'";
+  Text += Name;
+  Text += '\'';
+  if (!DWPName.empty()) {
+    Text += " (from ";
+    if (!DWOName.empty()) {
+      Text += '\'';
+      Text += DWOName;
+      Text += "' in ";
+    }
+    Text += '\'';
+    Text += DWPName;
+    Text += "')";
+  }
+  return Text;
+}
+
+static Error createError(StringRef Name, Error E) {
+  return make_error<DWPError>(
+      ("failure while decompressing compressed section: '" + Name + "', " +
+       llvm::toString(std::move(E)))
+          .str());
+}
+
+static Error
+handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
+                        StringRef &Name, StringRef &Contents) {
+  if (!Decompressor::isGnuStyle(Name))
+    return Error::success();
+
+  Expected<Decompressor> Dec =
+      Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
+  if (!Dec)
+    return createError(Name, Dec.takeError());
+
+  UncompressedSections.emplace_back();
+  if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
+    return createError(Name, std::move(E));
+
+  Name = Name.substr(2); // Drop ".z"
+  Contents = UncompressedSections.back();
+  return Error::success();
+}
+
+namespace llvm {
+// Parse and return the header of an info section compile/type unit.
+Expected<InfoSectionUnitHeader> parseInfoSectionUnitHeader(StringRef Info) {
+  InfoSectionUnitHeader Header;
+  Error Err = Error::success();
+  uint64_t Offset = 0;
+  DWARFDataExtractor InfoData(Info, true, 0);
+  std::tie(Header.Length, Header.Format) =
+      InfoData.getInitialLength(&Offset, &Err);
+  if (Err)
+    return make_error<DWPError>("cannot parse compile unit length: " +
+                                llvm::toString(std::move(Err)));
+
+  if (!InfoData.isValidOffset(Offset + (Header.Length - 1))) {
+    return make_error<DWPError>(
+        "compile unit exceeds .debug_info section range: " +
+        utostr(Offset + Header.Length) + " >= " + utostr(InfoData.size()));
+  }
+
+  Header.Version = InfoData.getU16(&Offset, &Err);
+  if (Err)
+    return make_error<DWPError>("cannot parse compile unit version: " +
+                                llvm::toString(std::move(Err)));
+
+  uint64_t MinHeaderLength;
+  if (Header.Version >= 5) {
+    // Size: Version (2), UnitType (1), AddrSize (1), DebugAbbrevOffset (4),
+    // Signature (8)
+    MinHeaderLength = 16;
+  } else {
+    // Size: Version (2), DebugAbbrevOffset (4), AddrSize (1)
+    MinHeaderLength = 7;
+  }
+  if (Header.Length < MinHeaderLength) {
+    return make_error<DWPError>("unit length is too small: expected at least " +
+                                utostr(MinHeaderLength) + " got " +
+                                utostr(Header.Length) + ".");
+  }
+  if (Header.Version >= 5) {
+    Header.UnitType = InfoData.getU8(&Offset);
+    Header.AddrSize = InfoData.getU8(&Offset);
+    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
+    Header.Signature = InfoData.getU64(&Offset);
+    if (Header.UnitType == dwarf::DW_UT_split_type) {
+      // Type offset.
+      MinHeaderLength += 4;
+      if (Header.Length < MinHeaderLength)
+        return make_error<DWPError>("type unit is missing type offset");
+      InfoData.getU32(&Offset);
+    }
+  } else {
+    // Note that, address_size and debug_abbrev_offset fields have switched
+    // places between dwarf version 4 and 5.
+    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
+    Header.AddrSize = InfoData.getU8(&Offset);
+  }
+
+  Header.HeaderSize = Offset;
+  return Header;
+}
+
+void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
+                            MCSection *StrOffsetSection,
+                            StringRef CurStrSection,
+                            StringRef CurStrOffsetSection, uint16_t Version) {
+  // Could possibly produce an error or warning if one of these was non-null but
+  // the other was null.
+  if (CurStrSection.empty() || CurStrOffsetSection.empty())
+    return;
+
+  DenseMap<uint64_t, uint32_t> OffsetRemapping;
+
+  DataExtractor Data(CurStrSection, true, 0);
+  uint64_t LocalOffset = 0;
+  uint64_t PrevOffset = 0;
+  while (const char *s = Data.getCStr(&LocalOffset)) {
+    OffsetRemapping[PrevOffset] =
+        Strings.getOffset(s, LocalOffset - PrevOffset);
+    PrevOffset = LocalOffset;
+  }
+
+  Data = DataExtractor(CurStrOffsetSection, true, 0);
+
+  Out.SwitchSection(StrOffsetSection);
+
+  uint64_t HeaderSize = debugStrOffsetsHeaderSize(Data, Version);
+  uint64_t Offset = 0;
+  uint64_t Size = CurStrOffsetSection.size();
+  // FIXME: This can be caused by bad input and should be handled as such.
+  assert(HeaderSize <= Size && "StrOffsetSection size is less than its header");
+  // Copy the header to the output.
+  Out.emitBytes(Data.getBytes(&Offset, HeaderSize));
+  while (Offset < Size) {
+    auto OldOffset = Data.getU32(&Offset);
+    auto NewOffset = OffsetRemapping[OldOffset];
+    Out.emitIntValue(NewOffset, 4);
+  }
+}
+
+void writeIndexTable(
+    MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
   for (const auto &E : IndexEntries)
     for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
       if (ContributionOffsets[i])
         Out.emitIntValue(E.second.Contributions[i].*Field, 4);
 }
 
-static void writeIndex(MCStreamer &Out, MCSection *Section,
-                       ArrayRef<unsigned> ContributionOffsets,
-                       const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
-                       uint32_t IndexVersion) {
+void writeIndex(MCStreamer &Out, MCSection *Section,
   if (IndexEntries.empty())
     return;
 
   unsigned Columns = 0;
   for (auto &C : ContributionOffsets)
     if (C)
       ++Columns;
 
   std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
   uint64_t Mask = Buckets.size() - 1;
   size_t i = 0;
   for (const auto &P : IndexEntries) {
     auto S = P.first;
     auto H = S & Mask;
     auto HP = ((S >> 32) & Mask) | 1;
     while (Buckets[H]) {
       assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
              "Duplicate unit");
       H = (H + HP) & Mask;
void writeIndex(MCStreamer &Out, MCSection *Section,
   for (const auto &I : Buckets)
     Out.emitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
 
   // Write the indexes.
   for (const auto &I : Buckets)
     Out.emitIntValue(I, 4);
 
   // Write the column headers (which sections will appear in the table)
   for (size_t i = 0; i != ContributionOffsets.size(); ++i)
     if (ContributionOffsets[i])
       Out.emitIntValue(getOnDiskSectionId(i), 4);
 
   // Write the offsets.
   writeIndexTable(Out, ContributionOffsets, IndexEntries,
                   &DWARFUnitIndex::Entry::SectionContribution::Offset);
 
   // Write the lengths.
   writeIndexTable(Out, ContributionOffsets, IndexEntries,
                   &DWARFUnitIndex::Entry::SectionContribution::Length);
 }
 
-static std::string buildDWODescription(StringRef Name, StringRef DWPName,
-                                       StringRef DWOName) {
-  std::string Text = "\'";
-  Text += Name;
-  Text += '\'';
-  if (!DWPName.empty()) {
-    Text += " (from ";
-    if (!DWOName.empty()) {
-      Text += '\'';
-      Text += DWOName;
-      Text += "' in ";
-    }
-    Text += '\'';
-    Text += DWPName;
-    Text += "')";
-  }
-  return Text;
-}
-
-static Error createError(StringRef Name, Error E) {
+Error buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
+                          const CompileUnitIdentifiers &ID, StringRef DWPName) {
   return make_error<DWPError>(
-      ("failure while decompressing compressed section: '" + Name + "', " +
-       llvm::toString(std::move(E)))
-          .str());
-}
-
-static Error
-handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
-                        StringRef &Name, StringRef &Contents) {
-  if (!Decompressor::isGnuStyle(Name))
-    return Error::success();
-
-  Expected<Decompressor> Dec =
-      Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
-  if (!Dec)
-    return createError(Name, Dec.takeError());
-
-  UncompressedSections.emplace_back();
-  if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
-    return createError(Name, std::move(E));
-
-  Name = Name.substr(2); // Drop ".z"
-  Contents = UncompressedSections.back();
-  return Error::success();
+      std::string("duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
+      buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
+                          PrevE.second.DWOName) +
+      " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
 }
 
-static Error handleSection(
+Error handleSection(
     const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
     const MCSection *StrSection, const MCSection *StrOffsetSection,
     const MCSection *TypesSection, const MCSection *CUIndexSection,
     const MCSection *TUIndexSection, const MCSection *InfoSection,
     const SectionRef &Section, MCStreamer &Out,
     std::deque<SmallString<32>> &UncompressedSections,
     uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
     StringRef &CurStrSection, StringRef &CurStrOffsetSection,
else if (OutSection == InfoSection)
     CurInfoSection.push_back(Contents);
   else {
     Out.SwitchSection(OutSection);
     Out.emitBytes(Contents);
   }
   return Error::success();
 }
 
-static Error
-buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
-                    const CompileUnitIdentifiers &ID, StringRef DWPName) {
-  return make_error<DWPError>(
-      std::string("duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
-      buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
-                          PrevE.second.DWOName) +
-      " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
-}
-
-static Expected<SmallVector<std::string, 16>>
-getDWOFilenames(StringRef ExecFilename) {
-  auto ErrOrObj = object::ObjectFile::createObjectFile(ExecFilename);
-  if (!ErrOrObj)
-    return ErrOrObj.takeError();
-
-  const ObjectFile &Obj = *ErrOrObj.get().getBinary();
-  std::unique_ptr<DWARFContext> DWARFCtx = DWARFContext::create(Obj);
-
-  SmallVector<std::string, 16> DWOPaths;
-  for (const auto &CU : DWARFCtx->compile_units()) {
-    const DWARFDie &Die = CU->getUnitDIE();
-    std::string DWOName = dwarf::toString(
-        Die.find({dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}), "");
-    if (DWOName.empty())
-      continue;
-    std::string DWOCompDir =
-        dwarf::toString(Die.find(dwarf::DW_AT_comp_dir), "");
-    if (!DWOCompDir.empty()) {
-      SmallString<16> DWOPath(std::move(DWOName));
-      sys::fs::make_absolute(DWOCompDir, DWOPath);
-      DWOPaths.emplace_back(DWOPath.data(), DWOPath.size());
-    } else {
-      DWOPaths.push_back(std::move(DWOName));
-    }
-  }
-  return std::move(DWOPaths);
-}
-
-static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
+Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
   const auto &MCOFI = *Out.getContext().getObjectFileInfo();
   MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
   MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
   MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
   MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
   MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
   MCSection *const InfoSection = MCOFI.getDwarfInfoDWOSection();
   const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
if (Version < 5) {
     ContributionOffsets[0] = 1;
   }
 
   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
              IndexEntries, IndexVersion);
 
   return Error::success();
 }
-
-static int error(const Twine &Error, const Twine &Context) {
-  errs() << Twine("while processing ") + Context + ":\n";
-  errs() << Twine("error: ") + Error + "\n";
-  return 1;
-}
-
-static Expected<Triple> readTargetTriple(StringRef FileName) {
-  auto ErrOrObj = object::ObjectFile::createObjectFile(FileName);
-  if (!ErrOrObj)
-    return ErrOrObj.takeError();
-
-  return ErrOrObj->getBinary()->makeTriple();
-}
-
-int main(int argc, char **argv) {
-  InitLLVM X(argc, argv);
-
-  cl::ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files\n");
-
-  llvm::InitializeAllTargetInfos();
-  llvm::InitializeAllTargetMCs();
-  llvm::InitializeAllTargets();
-  llvm::InitializeAllAsmPrinters();
-
-  std::vector<std::string> DWOFilenames = InputFiles;
-  for (const auto &ExecFilename : ExecFilenames) {
-    auto DWOs = getDWOFilenames(ExecFilename);
-    if (!DWOs) {
-      logAllUnhandledErrors(DWOs.takeError(), WithColor::error());
-      return 1;
-    }
-    DWOFilenames.insert(DWOFilenames.end(),
-                        std::make_move_iterator(DWOs->begin()),
-                        std::make_move_iterator(DWOs->end()));
-  }
-
-  if (DWOFilenames.empty())
-    return 0;
-
-  std::string ErrorStr;
-  StringRef Context = "dwarf streamer init";
-
-  auto ErrOrTriple = readTargetTriple(DWOFilenames.front());
-  if (!ErrOrTriple) {
-    logAllUnhandledErrors(ErrOrTriple.takeError(), WithColor::error());
-    return 1;
-  }
-
-  // Get the target.
-  const Target *TheTarget =
-      TargetRegistry::lookupTarget("", *ErrOrTriple, ErrorStr);
-  if (!TheTarget)
-    return error(ErrorStr, Context);
-  std::string TripleName = ErrOrTriple->getTriple();
-
-  // Create all the MC Objects.
-  std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
-  if (!MRI)
-    return error(Twine("no register info for target ") + TripleName, Context);
-
-  MCTargetOptions MCOptions = llvm::mc::InitMCTargetOptionsFromFlags();
-  std::unique_ptr<MCAsmInfo> MAI(
-      TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
-  if (!MAI)
-    return error("no asm info for target " + TripleName, Context);
-
-  std::unique_ptr<MCSubtargetInfo> MSTI(
-      TheTarget->createMCSubtargetInfo(TripleName, "", ""));
-  if (!MSTI)
-    return error("no subtarget info for target " + TripleName, Context);
-
-  MCContext MC(*ErrOrTriple, MAI.get(), MRI.get(), MSTI.get());
-  std::unique_ptr<MCObjectFileInfo> MOFI(
-      TheTarget->createMCObjectFileInfo(MC, /*PIC=*/false));
-  MC.setObjectFileInfo(MOFI.get());
-
-  MCTargetOptions Options;
-  auto MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, Options);
-  if (!MAB)
-    return error("no asm backend for target " + TripleName, Context);
-
-  std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
-  if (!MII)
-    return error("no instr info info for target " + TripleName, Context);
-
-  MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
-  if (!MCE)
-    return error("no code emitter for target " + TripleName, Context);
-
-  // Create the output file.
-  std::error_code EC;
-  ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_None);
-  Optional<buffer_ostream> BOS;
-  raw_pwrite_stream *OS;
-  if (EC)
-    return error(Twine(OutputFilename) + ": " + EC.message(), Context);
-  if (OutFile.os().supportsSeeking()) {
-    OS = &OutFile.os();
-  } else {
-    BOS.emplace(OutFile.os());
-    OS = BOS.getPointer();
-  }
-
-  std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
-      *ErrOrTriple, MC, std::unique_ptr<MCAsmBackend>(MAB),
-      MAB->createObjectWriter(*OS), std::unique_ptr<MCCodeEmitter>(MCE), *MSTI,
-      MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
-      /*DWARFMustBeAtTheEnd*/ false));
-  if (!MS)
-    return error("no object streamer for target " + TripleName, Context);
-
-  if (auto Err = write(*MS, DWOFilenames)) {
-    logAllUnhandledErrors(std::move(Err), WithColor::error());
-    return 1;
-  }
-
-  MS->Finish();
-  OutFile.keep();
-  return 0;
-}
+} // namespace llvm

llvm/tools/llvm-dwp/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   AllTargetsAsmParsers
   AllTargetsCodeGens
-  AllTargetsDescs
-  AllTargetsInfos
-  AsmPrinter
-  DebugInfoDWARF
-  MC
-  Object
-  Support
-  Target
+  DWP
   )
 
 add_llvm_tool(llvm-dwp
   llvm-dwp.cpp
-  DWPError.cpp
 
   DEPENDS
   intrinsics_gen
   )
 
 if(LLVM_INSTALL_BINUTILS_SYMLINKS)
   add_llvm_tool_symlink(dwp llvm-dwp)
 endif()

llvm/tools/llvm-dwp/llvm-dwp.cpp

 //===-- llvm-dwp.cpp - Split DWARF merging tool for llvm ------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // A utility for merging DWARF 5 Split DWARF .dwo files into .dwp (DWARF
 // package files).
 //
 //===----------------------------------------------------------------------===//
-#include "DWPError.h"
-#include "DWPStringPool.h"
-#include "llvm/ADT/MapVector.h"
-#include "llvm/ADT/Optional.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/DebugInfo/DWARF/DWARFContext.h"
-#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
-#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
-#include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
+#include "llvm/DWP/DWP.h"
+#include "llvm/DWP/DWPError.h"
+#include "llvm/DWP/DWPStringPool.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCInstrInfo.h"
-#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectWriter.h"
-#include "llvm/MC/MCRegisterInfo.h"
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCTargetOptionsCommandFlags.h"
-#include "llvm/Object/Decompressor.h"
-#include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/CommandLine.h"
-#include "llvm/Support/DataExtractor.h"
-#include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/MemoryBuffer.h"
-#include "llvm/Support/Path.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/WithColor.h"
-#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::object;
 
 static mc::RegisterMCTargetOptionsFlags MCTargetOptionsFlags;
 
 cl::OptionCategory DwpCategory("Specific Options");
 static cl::list<std::string> InputFiles(cl::Positional, cl::ZeroOrMore,
                                         cl::desc("<input files>"),
                                         cl::cat(DwpCategory));
 
 static cl::list<std::string> ExecFilenames(
     "e", cl::ZeroOrMore,
     cl::desc("Specify the executable/library files to get the list of *.dwo from"),
     cl::value_desc("filename"), cl::cat(DwpCategory));
 
 static cl::opt<std::string> OutputFilename(cl::Required, "o",
                                            cl::desc("Specify the output file."),
                                            cl::value_desc("filename"),
                                            cl::cat(DwpCategory));
 
-// Returns the size of debug_str_offsets section headers in bytes.
-static uint64_t debugStrOffsetsHeaderSize(DataExtractor StrOffsetsData,
-                                          uint16_t DwarfVersion) {
-  if (DwarfVersion <= 4)
-    return 0; // There is no header before dwarf 5.
-  uint64_t Offset = 0;
-  uint64_t Length = StrOffsetsData.getU32(&Offset);
-  if (Length == llvm::dwarf::DW_LENGTH_DWARF64)
-    return 16; // unit length: 12 bytes, version: 2 bytes, padding: 2 bytes.
-  return 8;    // unit length: 4 bytes, version: 2 bytes, padding: 2 bytes.
-}
-
-// Holds data for Skeleton, Split Compilation, and Type Unit Headers (only in
-// v5) as defined in Dwarf 5 specification, 7.5.1.2, 7.5.1.3 and Dwarf 4
-// specification 7.5.1.1.
-struct InfoSectionUnitHeader {
-  // unit_length field. Note that the type is uint64_t even in 32-bit dwarf.
-  uint64_t Length = 0;
-
-  // version field.
-  uint16_t Version = 0;
-
-  // unit_type field. Initialized only if Version >= 5.
-  uint8_t UnitType = 0;
-
-  // address_size field.
-  uint8_t AddrSize = 0;
-
-  // debug_abbrev_offset field. Note that the type is uint64_t even in 32-bit
-  // dwarf. It is assumed to be 0.
-  uint64_t DebugAbbrevOffset = 0;
-
-  // dwo_id field. This resides in the header only if Version >= 5.
-  // In earlier versions, it is read from DW_AT_GNU_dwo_id.
-  Optional<uint64_t> Signature = None;
-
-  // Derived from the length of Length field.
-  dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
-
-  // The size of the Header in bytes. This is derived while parsing the header,
-  // and is stored as a convenience.
-  uint8_t HeaderSize = 0;
-};
-
-// Parse and return the header of an info section compile/type unit.
-static Expected<InfoSectionUnitHeader>
-parseInfoSectionUnitHeader(StringRef Info) {
-  InfoSectionUnitHeader Header;
-  Error Err = Error::success();
-  uint64_t Offset = 0;
-  DWARFDataExtractor InfoData(Info, true, 0);
-  std::tie(Header.Length, Header.Format) =
-      InfoData.getInitialLength(&Offset, &Err);
-  if (Err)
-    return make_error<DWPError>("cannot parse compile unit length: " +
-                                llvm::toString(std::move(Err)));
-
-  if (!InfoData.isValidOffset(Offset + (Header.Length - 1))) {
-    return make_error<DWPError>(
-        "compile unit exceeds .debug_info section range: " +
-        utostr(Offset + Header.Length) + " >= " + utostr(InfoData.size()));
-  }
-
-  Header.Version = InfoData.getU16(&Offset, &Err);
-  if (Err)
-    return make_error<DWPError>("cannot parse compile unit version: " +
-                                llvm::toString(std::move(Err)));
-
-  uint64_t MinHeaderLength;
-  if (Header.Version >= 5) {
-    // Size: Version (2), UnitType (1), AddrSize (1), DebugAbbrevOffset (4),
-    // Signature (8)
-    MinHeaderLength = 16;
-  } else {
-    // Size: Version (2), DebugAbbrevOffset (4), AddrSize (1)
-    MinHeaderLength = 7;
-  }
-  if (Header.Length < MinHeaderLength) {
-    return make_error<DWPError>("unit length is too small: expected at least " +
-                                utostr(MinHeaderLength) + " got " +
-                                utostr(Header.Length) + ".");
-  }
-  if (Header.Version >= 5) {
-    Header.UnitType = InfoData.getU8(&Offset);
-    Header.AddrSize = InfoData.getU8(&Offset);
-    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
-    Header.Signature = InfoData.getU64(&Offset);
-    if (Header.UnitType == dwarf::DW_UT_split_type) {
-      // Type offset.
-      MinHeaderLength += 4;
-      if (Header.Length < MinHeaderLength)
-        return make_error<DWPError>("type unit is missing type offset");
-      InfoData.getU32(&Offset);
-    }
-  } else {
-    // Note that, address_size and debug_abbrev_offset fields have switched
-    // places between dwarf version 4 and 5.
-    Header.DebugAbbrevOffset = InfoData.getU32(&Offset);
-    Header.AddrSize = InfoData.getU8(&Offset);
-  }
-
-  Header.HeaderSize = Offset;
-  return Header;
-}
-
-static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
-                                   MCSection *StrOffsetSection,
-                                   StringRef CurStrSection,
-                                   StringRef CurStrOffsetSection,
-                                   uint16_t Version) {
-  // Could possibly produce an error or warning if one of these was non-null but
-  // the other was null.
-  if (CurStrSection.empty() || CurStrOffsetSection.empty())
-    return;
-
-  DenseMap<uint64_t, uint32_t> OffsetRemapping;
-
-  DataExtractor Data(CurStrSection, true, 0);
-  uint64_t LocalOffset = 0;
-  uint64_t PrevOffset = 0;
-  while (const char *s = Data.getCStr(&LocalOffset)) {
-    OffsetRemapping[PrevOffset] =
-        Strings.getOffset(s, LocalOffset - PrevOffset);
-    PrevOffset = LocalOffset;
-  }
-
-  Data = DataExtractor(CurStrOffsetSection, true, 0);
-
-  Out.SwitchSection(StrOffsetSection);
-
-  uint64_t HeaderSize = debugStrOffsetsHeaderSize(Data, Version);
-  uint64_t Offset = 0;
-  uint64_t Size = CurStrOffsetSection.size();
-  // FIXME: This can be caused by bad input and should be handled as such.
-  assert(HeaderSize <= Size && "StrOffsetSection size is less than its header");
-  // Copy the header to the output.
-  Out.emitBytes(Data.getBytes(&Offset, HeaderSize));
-  while (Offset < Size) {
-    auto OldOffset = Data.getU32(&Offset);
-    auto NewOffset = OffsetRemapping[OldOffset];
-    Out.emitIntValue(NewOffset, 4);
-  }
-}
-
-static uint64_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
-  uint64_t Offset = 0;
-  DataExtractor AbbrevData(Abbrev, true, 0);
-  while (AbbrevData.getULEB128(&Offset) != AbbrCode) {
-    // Tag
-    AbbrevData.getULEB128(&Offset);
-    // DW_CHILDREN
-    AbbrevData.getU8(&Offset);
-    // Attributes
-    while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
-      ;
-  }
-  return Offset;
-}
-
-struct CompileUnitIdentifiers {
-  uint64_t Signature = 0;
-  const char *Name = "";
-  const char *DWOName = "";
-};
-
-static Expected<const char *>
-getIndexedString(dwarf::Form Form, DataExtractor InfoData, uint64_t &InfoOffset,
-                 StringRef StrOffsets, StringRef Str, uint16_t Version) {
-  if (Form == dwarf::DW_FORM_string)
-    return InfoData.getCStr(&InfoOffset);
-  uint64_t StrIndex;
-  switch (Form) {
-  case dwarf::DW_FORM_strx1:
-    StrIndex = InfoData.getU8(&InfoOffset);
-    break;
-  case dwarf::DW_FORM_strx2:
-    StrIndex = InfoData.getU16(&InfoOffset);
-    break;
-  case dwarf::DW_FORM_strx3:
-    StrIndex = InfoData.getU24(&InfoOffset);
-    break;
-  case dwarf::DW_FORM_strx4:
-    StrIndex = InfoData.getU32(&InfoOffset);
-    break;
-  case dwarf::DW_FORM_strx:
-  case dwarf::DW_FORM_GNU_str_index:
-    StrIndex = InfoData.getULEB128(&InfoOffset);
-    break;
-  default:
-    return make_error<DWPError>(
-        "string field must be encoded with one of the following: "
-        "DW_FORM_string, DW_FORM_strx, DW_FORM_strx1, DW_FORM_strx2, "
-        "DW_FORM_strx3, DW_FORM_strx4, or DW_FORM_GNU_str_index.");
-  }
-  DataExtractor StrOffsetsData(StrOffsets, true, 0);
-  uint64_t StrOffsetsOffset = 4 * StrIndex;
-  StrOffsetsOffset += debugStrOffsetsHeaderSize(StrOffsetsData, Version);
-
-  uint64_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
-  DataExtractor StrData(Str, true, 0);
-  return StrData.getCStr(&StrOffset);
-}
-
-static Expected<CompileUnitIdentifiers>
-getCUIdentifiers(InfoSectionUnitHeader &Header, StringRef Abbrev,
-                 StringRef Info, StringRef StrOffsets, StringRef Str) {
-  DataExtractor InfoData(Info, true, 0);
-  uint64_t Offset = Header.HeaderSize;
-  if (Header.Version >= 5 && Header.UnitType != dwarf::DW_UT_split_compile)
-    return make_error<DWPError>(
-        std::string("unit type DW_UT_split_compile type not found in "
-                    "debug_info header. Unexpected unit type 0x" +
-                    utostr(Header.UnitType) + " found"));
-
-  CompileUnitIdentifiers ID;
-
-  uint32_t AbbrCode = InfoData.getULEB128(&Offset);
-  DataExtractor AbbrevData(Abbrev, true, 0);
-  uint64_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
-  auto Tag = static_cast<dwarf::Tag>(AbbrevData.getULEB128(&AbbrevOffset));
-  if (Tag != dwarf::DW_TAG_compile_unit)
-    return make_error<DWPError>("top level DIE is not a compile unit");
-  // DW_CHILDREN
-  AbbrevData.getU8(&AbbrevOffset);
-  uint32_t Name;
-  dwarf::Form Form;
-  while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
-         (Form = static_cast<dwarf::Form>(AbbrevData.getULEB128(&AbbrevOffset))) &&
-         (Name != 0 || Form != 0)) {
-    switch (Name) {
-    case dwarf::DW_AT_name: {
-      Expected<const char *> EName = getIndexedString(
-          Form, InfoData, Offset, StrOffsets, Str, Header.Version);
-      if (!EName)
-        return EName.takeError();
-      ID.Name = *EName;
-      break;
-    }
-    case dwarf::DW_AT_GNU_dwo_name:
-    case dwarf::DW_AT_dwo_name: {
-      Expected<const char *> EName = getIndexedString(
-          Form, InfoData, Offset, StrOffsets, Str, Header.Version);
-      if (!EName)
-        return EName.takeError();
-      ID.DWOName = *EName;
-      break;
-    }
-    case dwarf::DW_AT_GNU_dwo_id:
-      Header.Signature = InfoData.getU64(&Offset);
-      break;
-    default:
-      DWARFFormValue::skipValue(
-          Form, InfoData, &Offset,
-          dwarf::FormParams({Header.Version, Header.AddrSize, Header.Format}));
-    }
-  }
-  if (!Header.Signature)
-    return make_error<DWPError>("compile unit missing dwo_id");
-  ID.Signature = *Header.Signature;
-  return ID;
-}
-
-struct UnitIndexEntry {
-  DWARFUnitIndex::Entry::SectionContribution Contributions[8];
-  std::string Name;
-  std::string DWOName;
-  StringRef DWPName;
-};
-
-static bool isSupportedSectionKind(DWARFSectionKind Kind) {
-  return Kind != DW_SECT_EXT_unknown;
-}
-
-// Convert an internal section identifier into the index to use with
-// UnitIndexEntry::Contributions.
-static unsigned getContributionIndex(DWARFSectionKind Kind,
-                                     uint32_t IndexVersion) {
-  assert(serializeSectionKind(Kind, IndexVersion) >= DW_SECT_INFO);
-  return serializeSectionKind(Kind, IndexVersion) - DW_SECT_INFO;
-}
-
-// Convert a UnitIndexEntry::Contributions index to the corresponding on-disk
-// value of the section identifier.
-static unsigned getOnDiskSectionId(unsigned Index) {
-  return Index + DW_SECT_INFO;
-}
-
-static StringRef getSubsection(StringRef Section,
-                               const DWARFUnitIndex::Entry &Entry,
-                               DWARFSectionKind Kind) {
-  const auto *Off = Entry.getContribution(Kind);
-  if (!Off)
-    return StringRef();
-  return Section.substr(Off->Offset, Off->Length);
-}
-
-static void
-addAllTypesFromDWP(MCStreamer &Out,
-                   MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
-                   const DWARFUnitIndex &TUIndex, MCSection *OutputTypes,
-                   StringRef Types, const UnitIndexEntry &TUEntry,
-                   uint32_t &TypesOffset, unsigned TypesContributionIndex) {
-  Out.SwitchSection(OutputTypes);
-  for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
-    auto *I = E.getContributions();
-    if (!I)
-      continue;
-    auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
-    if (!P.second)
-      continue;
-    auto &Entry = P.first->second;
-    // Zero out the debug_info contribution
-    Entry.Contributions[0] = {};
-    for (auto Kind : TUIndex.getColumnKinds()) {
-      if (!isSupportedSectionKind(Kind))
-        continue;
-      auto &C =
-          Entry.Contributions[getContributionIndex(Kind, TUIndex.getVersion())];
-      C.Offset += I->Offset;
-      C.Length = I->Length;
-      ++I;
-    }
-    auto &C = Entry.Contributions[TypesContributionIndex];
-    Out.emitBytes(Types.substr(
-        C.Offset - TUEntry.Contributions[TypesContributionIndex].Offset,
-        C.Length));
-    C.Offset = TypesOffset;
-    TypesOffset += C.Length;
-  }
-}
-
-static void addAllTypesFromTypesSection(
-    MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
-    MCSection *OutputTypes, const std::vector<StringRef> &TypesSections,
-    const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
-  for (StringRef Types : TypesSections) {
-    Out.SwitchSection(OutputTypes);
-    uint64_t Offset = 0;
-    DataExtractor Data(Types, true, 0);
-    while (Data.isValidOffset(Offset)) {
-      UnitIndexEntry Entry = CUEntry;
-      // Zero out the debug_info contribution
-      Entry.Contributions[0] = {};
-      auto &C = Entry.Contributions[getContributionIndex(DW_SECT_EXT_TYPES, 2)];
-      C.Offset = TypesOffset;
-      auto PrevOffset = Offset;
-      // Length of the unit, including the 4 byte length field.
-      C.Length = Data.getU32(&Offset) + 4;
-
-      Data.getU16(&Offset); // Version
-      Data.getU32(&Offset); // Abbrev offset
-      Data.getU8(&Offset);  // Address size
-      auto Signature = Data.getU64(&Offset);
-      Offset = PrevOffset + C.Length;
-
-      auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
-      if (!P.second)
-        continue;
-
-      Out.emitBytes(Types.substr(PrevOffset, C.Length));
-      TypesOffset += C.Length;
-    }
-  }
-}
-
-static void
-writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
-                const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
-                uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
-  for (const auto &E : IndexEntries)
-    for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
-      if (ContributionOffsets[i])
-        Out.emitIntValue(E.second.Contributions[i].*Field, 4);
-}
-
-static void writeIndex(MCStreamer &Out, MCSection *Section,
-                       ArrayRef<unsigned> ContributionOffsets,
-                       const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
-                       uint32_t IndexVersion) {
-  if (IndexEntries.empty())
-    return;
-
-  unsigned Columns = 0;
-  for (auto &C : ContributionOffsets)
-    if (C)
-      ++Columns;
-
-  std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
-  uint64_t Mask = Buckets.size() - 1;
-  size_t i = 0;
-  for (const auto &P : IndexEntries) {
-    auto S = P.first;
-    auto H = S & Mask;
-    auto HP = ((S >> 32) & Mask) | 1;
-    while (Buckets[H]) {
-      assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
-             "Duplicate unit");
-      H = (H + HP) & Mask;
-    }
-    Buckets[H] = i + 1;
-    ++i;
-  }
-
-  Out.SwitchSection(Section);
-  Out.emitIntValue(IndexVersion, 4);        // Version
-  Out.emitIntValue(Columns, 4);             // Columns
-  Out.emitIntValue(IndexEntries.size(), 4); // Num Units
-  Out.emitIntValue(Buckets.size(), 4);      // Num Buckets
-
-  // Write the signatures.
-  for (const auto &I : Buckets)
-    Out.emitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
-
-  // Write the indexes.
-  for (const auto &I : Buckets)
-    Out.emitIntValue(I, 4);
-
-  // Write the column headers (which sections will appear in the table)
-  for (size_t i = 0; i != ContributionOffsets.size(); ++i)
-    if (ContributionOffsets[i])
-      Out.emitIntValue(getOnDiskSectionId(i), 4);
-
-  // Write the offsets.
-  writeIndexTable(Out, ContributionOffsets, IndexEntries,
-                  &DWARFUnitIndex::Entry::SectionContribution::Offset);
-
-  // Write the lengths.
-  writeIndexTable(Out, ContributionOffsets, IndexEntries,
-                  &DWARFUnitIndex::Entry::SectionContribution::Length);
-}
-
-static std::string buildDWODescription(StringRef Name, StringRef DWPName,
-                                       StringRef DWOName) {
-  std::string Text = "\'";
-  Text += Name;
-  Text += '\'';
-  if (!DWPName.empty()) {
-    Text += " (from ";
-    if (!DWOName.empty()) {
-      Text += '\'';
-      Text += DWOName;
-      Text += "' in ";
-    }
-    Text += '\'';
-    Text += DWPName;
-    Text += "')";
-  }
-  return Text;
-}
-
-static Error createError(StringRef Name, Error E) {
-  return make_error<DWPError>(
-      ("failure while decompressing compressed section: '" + Name + "', " +
-       llvm::toString(std::move(E)))
-          .str());
-}
-
-static Error
-handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
-                        StringRef &Name, StringRef &Contents) {
-  if (!Decompressor::isGnuStyle(Name))
-    return Error::success();
-
-  Expected<Decompressor> Dec =
-      Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
-  if (!Dec)
-    return createError(Name, Dec.takeError());
-
-  UncompressedSections.emplace_back();
-  if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
-    return createError(Name, std::move(E));
-
-  Name = Name.substr(2); // Drop ".z"
-  Contents = UncompressedSections.back();
-  return Error::success();
-}
-
-static Error handleSection(
-    const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
-    const MCSection *StrSection, const MCSection *StrOffsetSection,
-    const MCSection *TypesSection, const MCSection *CUIndexSection,
-    const MCSection *TUIndexSection, const MCSection *InfoSection,
-    const SectionRef &Section, MCStreamer &Out,
-    std::deque<SmallString<32>> &UncompressedSections,
-    uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
-    StringRef &CurStrSection, StringRef &CurStrOffsetSection,
-    std::vector<StringRef> &CurTypesSection,
-    std::vector<StringRef> &CurInfoSection, StringRef &AbbrevSection,
-    StringRef &CurCUIndexSection, StringRef &CurTUIndexSection,
-    std::vector<std::pair<DWARFSectionKind, uint32_t>> &SectionLength) {
-  if (Section.isBSS())
-    return Error::success();
-
-  if (Section.isVirtual())
-    return Error::success();
-
-  Expected<StringRef> NameOrErr = Section.getName();
-  if (!NameOrErr)
-    return NameOrErr.takeError();
-  StringRef Name = *NameOrErr;
-
-  Expected<StringRef> ContentsOrErr = Section.getContents();
-  if (!ContentsOrErr)
-    return ContentsOrErr.takeError();
-  StringRef Contents = *ContentsOrErr;
-
-  if (auto Err = handleCompressedSection(UncompressedSections, Name, Contents))
-    return Err;
-
-  Name = Name.substr(Name.find_first_not_of("._"));
-
-  auto SectionPair = KnownSections.find(Name);
-  if (SectionPair == KnownSections.end())
-    return Error::success();
-
-  if (DWARFSectionKind Kind = SectionPair->second.second) {
-    if (Kind != DW_SECT_EXT_TYPES && Kind != DW_SECT_INFO) {
-      SectionLength.push_back(std::make_pair(Kind, Contents.size()));
-    }
-
-    if (Kind == DW_SECT_ABBREV) {
-      AbbrevSection = Contents;
-    }
-  }
-
-  MCSection *OutSection = SectionPair->second.first;
-  if (OutSection == StrOffsetSection)
-    CurStrOffsetSection = Contents;
-  else if (OutSection == StrSection)
-    CurStrSection = Contents;
-  else if (OutSection == TypesSection)
-    CurTypesSection.push_back(Contents);
-  else if (OutSection == CUIndexSection)
-    CurCUIndexSection = Contents;
-  else if (OutSection == TUIndexSection)
-    CurTUIndexSection = Contents;
-  else if (OutSection == InfoSection)
-    CurInfoSection.push_back(Contents);
-  else {
-    Out.SwitchSection(OutSection);
-    Out.emitBytes(Contents);
-  }
-  return Error::success();
-}
-
-static Error
-buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
-                    const CompileUnitIdentifiers &ID, StringRef DWPName) {
-  return make_error<DWPError>(
-      std::string("duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
-      buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
-                          PrevE.second.DWOName) +
-      " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
-}
-
 static Expected<SmallVector<std::string, 16>>
 getDWOFilenames(StringRef ExecFilename) {
   auto ErrOrObj = object::ObjectFile::createObjectFile(ExecFilename);
   if (!ErrOrObj)
     return ErrOrObj.takeError();
 
   const ObjectFile &Obj = *ErrOrObj.get().getBinary();
   std::unique_ptr<DWARFContext> DWARFCtx = DWARFContext::create(Obj);
if (!DWOCompDir.empty()) {
       DWOPaths.emplace_back(DWOPath.data(), DWOPath.size());
     } else {
       DWOPaths.push_back(std::move(DWOName));
     }
   }
   return std::move(DWOPaths);
 }
 
-static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
-  const auto &MCOFI = *Out.getContext().getObjectFileInfo();
-  MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
-  MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
-  MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
-  MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
-  MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
-  MCSection *const InfoSection = MCOFI.getDwarfInfoDWOSection();
-  const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
-      {"debug_info.dwo", {InfoSection, DW_SECT_INFO}},
-      {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_EXT_TYPES}},
-      {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
-      {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
-      {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_EXT_LOC}},
-      {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
-      {"debug_macro.dwo", {MCOFI.getDwarfMacroDWOSection(), DW_SECT_MACRO}},
-      {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
-      {"debug_loclists.dwo",
-       {MCOFI.getDwarfLoclistsDWOSection(), DW_SECT_LOCLISTS}},
-      {"debug_rnglists.dwo",
-       {MCOFI.getDwarfRnglistsDWOSection(), DW_SECT_RNGLISTS}},
-      {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
-      {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
-
-  MapVector<uint64_t, UnitIndexEntry> IndexEntries;
-  MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
-
-  uint32_t ContributionOffsets[8] = {};
-  uint16_t Version = 0;
-  uint32_t IndexVersion = 0;
-
-  DWPStringPool Strings(Out, StrSection);
-
-  SmallVector<OwningBinary<object::ObjectFile>, 128> Objects;
-  Objects.reserve(Inputs.size());
-
-  std::deque<SmallString<32>> UncompressedSections;
-
-  for (const auto &Input : Inputs) {
-    auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
-    if (!ErrOrObj)
-      return ErrOrObj.takeError();
-
-    auto &Obj = *ErrOrObj->getBinary();
-    Objects.push_back(std::move(*ErrOrObj));
-
-    UnitIndexEntry CurEntry = {};
-
-    StringRef CurStrSection;
-    StringRef CurStrOffsetSection;
-    std::vector<StringRef> CurTypesSection;
-    std::vector<StringRef> CurInfoSection;
-    StringRef AbbrevSection;
-    StringRef CurCUIndexSection;
-    StringRef CurTUIndexSection;
-
-    // This maps each section contained in this file to its length.
-    // This information is later on used to calculate the contributions,
-    // i.e. offset and length, of each compile/type unit to a section.
-    std::vector<std::pair<DWARFSectionKind, uint32_t>> SectionLength;
-
-    for (const auto &Section : Obj.sections())
-      if (auto Err = handleSection(
-              KnownSections, StrSection, StrOffsetSection, TypesSection,
-              CUIndexSection, TUIndexSection, InfoSection, Section, Out,
-              UncompressedSections, ContributionOffsets, CurEntry,
-              CurStrSection, CurStrOffsetSection, CurTypesSection,
-              CurInfoSection, AbbrevSection, CurCUIndexSection,
-              CurTUIndexSection, SectionLength))
-        return Err;
-
-    if (CurInfoSection.empty())
-      continue;
-
-    Expected<InfoSectionUnitHeader> HeaderOrErr =
-        parseInfoSectionUnitHeader(CurInfoSection.front());
-    if (!HeaderOrErr)
-      return HeaderOrErr.takeError();
-    InfoSectionUnitHeader &Header = *HeaderOrErr;
-
-    if (Version == 0) {
-      Version = Header.Version;
-      IndexVersion = Version < 5 ? 2 : 5;
-    } else if (Version != Header.Version) {
-      return make_error<DWPError>("incompatible DWARF compile unit versions.");
-    }
-
-    writeStringsAndOffsets(Out, Strings, StrOffsetSection, CurStrSection,
-                           CurStrOffsetSection, Header.Version);
-
-    for (auto Pair : SectionLength) {
-      auto Index = getContributionIndex(Pair.first, IndexVersion);
-      CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
-      ContributionOffsets[Index] +=
-          (CurEntry.Contributions[Index].Length = Pair.second);
-    }
-
-    uint32_t &InfoSectionOffset =
-        ContributionOffsets[getContributionIndex(DW_SECT_INFO, IndexVersion)];
-    if (CurCUIndexSection.empty()) {
-      bool FoundCUUnit = false;
-      Out.SwitchSection(InfoSection);
-      for (StringRef Info : CurInfoSection) {
-        uint64_t UnitOffset = 0;
-        while (Info.size() > UnitOffset) {
-          Expected<InfoSectionUnitHeader> HeaderOrError =
-              parseInfoSectionUnitHeader(Info.substr(UnitOffset, Info.size()));
-          if (!HeaderOrError)
-            return HeaderOrError.takeError();
-          InfoSectionUnitHeader &Header = *HeaderOrError;
-
-          UnitIndexEntry Entry = CurEntry;
-          auto &C = Entry.Contributions[getContributionIndex(DW_SECT_INFO,
-                                                             IndexVersion)];
-          C.Offset = InfoSectionOffset;
-          C.Length = Header.Length + 4;
-          UnitOffset += C.Length;
-          if (Header.Version < 5 ||
-              Header.UnitType == dwarf::DW_UT_split_compile) {
-            Expected<CompileUnitIdentifiers> EID =
-                getCUIdentifiers(Header, AbbrevSection,
-                                 Info.substr(UnitOffset - C.Length, C.Length),
-                                 CurStrOffsetSection, CurStrSection);
-
-            if (!EID)
-              return createFileError(Input, EID.takeError());
-            const auto &ID = *EID;
-            auto P = IndexEntries.insert(std::make_pair(ID.Signature, Entry));
-            if (!P.second)
-              return buildDuplicateError(*P.first, ID, "");
-            P.first->second.Name = ID.Name;
-            P.first->second.DWOName = ID.DWOName;
-
-            FoundCUUnit = true;
-          } else if (Header.UnitType == dwarf::DW_UT_split_type) {
-            auto P = TypeIndexEntries.insert(
-                std::make_pair(Header.Signature.getValue(), Entry));
-            if (!P.second)
-              continue;
-          }
-          Out.emitBytes(Info.substr(UnitOffset - C.Length, C.Length));
-          InfoSectionOffset += C.Length;
-        }
-      }
-
-      if (!FoundCUUnit)
-        return make_error<DWPError>("no compile unit found in file: " + Input);
-
-      if (IndexVersion == 2) {
-        // Add types from the .debug_types section from DWARF < 5.
-        addAllTypesFromTypesSection(
-            Out, TypeIndexEntries, TypesSection, CurTypesSection, CurEntry,
-            ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES, 2)]);
-      }
-      continue;
-    }
-
-    if (CurInfoSection.size() != 1)
-      return make_error<DWPError>("expected exactly one occurrence of a debug "
-                                  "info section in a .dwp file");
-    StringRef DwpSingleInfoSection = CurInfoSection.front();
-
-    DWARFUnitIndex CUIndex(DW_SECT_INFO);
-    DataExtractor CUIndexData(CurCUIndexSection, Obj.isLittleEndian(), 0);
-    if (!CUIndex.parse(CUIndexData))
-      return make_error<DWPError>("failed to parse cu_index");
-    if (CUIndex.getVersion() != IndexVersion)
-      return make_error<DWPError>("incompatible cu_index versions, found " +
-                                  utostr(CUIndex.getVersion()) +
-                                  " and expecting " + utostr(IndexVersion));
-
-    Out.SwitchSection(InfoSection);
-    for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
-      auto *I = E.getContributions();
-      if (!I)
-        continue;
-      auto P = IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
-      StringRef CUInfoSection =
-          getSubsection(DwpSingleInfoSection, E, DW_SECT_INFO);
-      Expected<InfoSectionUnitHeader> HeaderOrError =
-          parseInfoSectionUnitHeader(CUInfoSection);
-      if (!HeaderOrError)
-        return HeaderOrError.takeError();
-      InfoSectionUnitHeader &Header = *HeaderOrError;
-
-      Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
-          Header, getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
-          CUInfoSection,
-          getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
-          CurStrSection);
-      if (!EID)
-        return createFileError(Input, EID.takeError());
-      const auto &ID = *EID;
-      if (!P.second)
-        return buildDuplicateError(*P.first, ID, Input);
-      auto &NewEntry = P.first->second;
-      NewEntry.Name = ID.Name;
-      NewEntry.DWOName = ID.DWOName;
-      NewEntry.DWPName = Input;
-      for (auto Kind : CUIndex.getColumnKinds()) {
-        if (!isSupportedSectionKind(Kind))
-          continue;
-        auto &C =
-            NewEntry.Contributions[getContributionIndex(Kind, IndexVersion)];
-        C.Offset += I->Offset;
-        C.Length = I->Length;
-        ++I;
-      }
-      unsigned Index = getContributionIndex(DW_SECT_INFO, IndexVersion);
-      auto &C = NewEntry.Contributions[Index];
-      Out.emitBytes(CUInfoSection);
-      C.Offset = InfoSectionOffset;
-      InfoSectionOffset += C.Length;
-    }
-
-    if (!CurTUIndexSection.empty()) {
-      llvm::DWARFSectionKind TUSectionKind;
-      MCSection *OutSection;
-      StringRef TypeInputSection;
-      // Write type units into debug info section for DWARFv5.
-      if (Version >= 5) {
-        TUSectionKind = DW_SECT_INFO;
-        OutSection = InfoSection;
-        TypeInputSection = DwpSingleInfoSection;
-      } else {
-        // Write type units into debug types section for DWARF < 5.
-        if (CurTypesSection.size() != 1)
-          return make_error<DWPError>(
-              "multiple type unit sections in .dwp file");
-
-        TUSectionKind = DW_SECT_EXT_TYPES;
-        OutSection = TypesSection;
-        TypeInputSection = CurTypesSection.front();
-      }
-
-      DWARFUnitIndex TUIndex(TUSectionKind);
-      DataExtractor TUIndexData(CurTUIndexSection, Obj.isLittleEndian(), 0);
-      if (!TUIndex.parse(TUIndexData))
-        return make_error<DWPError>("failed to parse tu_index");
-      if (TUIndex.getVersion() != IndexVersion)
-        return make_error<DWPError>("incompatible tu_index versions, found " +
-                                    utostr(TUIndex.getVersion()) +
-                                    " and expecting " + utostr(IndexVersion));
-
-      unsigned TypesContributionIndex =
-          getContributionIndex(TUSectionKind, IndexVersion);
-      addAllTypesFromDWP(Out, TypeIndexEntries, TUIndex, OutSection,
-                         TypeInputSection, CurEntry,
-                         ContributionOffsets[TypesContributionIndex],
-                         TypesContributionIndex);
-    }
-  }
-
-  if (Version < 5) {
-    // Lie about there being no info contributions so the TU index only includes
-    // the type unit contribution for DWARF < 5. In DWARFv5 the TU index has a
-    // contribution to the info section, so we do not want to lie about it.
-    ContributionOffsets[0] = 0;
-  }
-  writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
-             TypeIndexEntries, IndexVersion);
-
-  if (Version < 5) {
-    // Lie about the type contribution for DWARF < 5. In DWARFv5 the type
-    // section does not exist, so no need to do anything about this.
-    ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES, 2)] = 0;
-    // Unlie about the info contribution
-    ContributionOffsets[0] = 1;
-  }
-
-  writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
-             IndexEntries, IndexVersion);
-
-  return Error::success();
-}
-
 static int error(const Twine &Error, const Twine &Context) {
   errs() << Twine("while processing ") + Context + ":\n";
   errs() << Twine("error: ") + Error + "\n";
   return 1;
 }
 
 static Expected<Triple> readTargetTriple(StringRef FileName) {
   auto ErrOrObj = object::ObjectFile::createObjectFile(FileName);