LLD: Add AMDGPU ELF ReaderWriter

[• tstellarAMD]

Summary

This is a basic implementation that allows lld to emit binaries consumable
by the HSA runtime.

[atanasyan]

As to me I would add more tests. For example, check ELF file header fields,

lib/ReaderWriter/ELF/AMDGPU/AMDGPUHSA.h

16 ↗

(On Diff #29912)

I think it is better to move all these declarations to llvm\Support\ELF.h. In that case you can support these flags in the llvm-readobj tool.

lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.cpp

26

Run the clang-format on this line.

37

Do you really need this empty function?

lib/ReaderWriter/ELF/AMDGPU/AMDGPUSymbolTable.cpp

23

Run the clang-format on this line.

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.cpp

73

Do you need this commented code?

78

Redundant empty line.

84

Redundant empty line.

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.h

36

Please remove the commented code.

[• tstellarAMD]

Here is an updated patch with the following changes:

• Ran clang-format on all new files.
• Merged http://reviews.llvm.org/D11265 into this patch.
• Moved AMDGPU ELF definitions into Support/ELF.h.
• Added more checks in the testcase.

[• tstellarAMD]

Ping.

[atanasyan]

I added some notes and included Rui Ueyama to the reviewers list.

lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.cpp

18–33

These methods do nothing now. I suggest to remove them from this commit and add later if necessary.

lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.h

23

Usually we put constructors in the beginning of the class declarations. Other methods go after that.

31

Do you really need this function declaration? Below in the AMDGPULinkingContext.cpp you define void setAMDGPUELFHeader(ELFHeader<ELF64LE> &elfHeader) only.

[ruiu]

lib/ReaderWriter/ELF/AMDGPU/AMDGPUELFFile.cpp

14–22

Can you add llvm::ELF::SHT_NOTE to ELFFile::handleSectionWithNoSymbols and remove this function? I'm not 100% sure but I believe doing that is not harmful to other ports.

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.cpp

55

Use real type instead of auto as the type is not obvious.

56

Ditto

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.h

39

Remove this empty line.

43–45

You may want to move these lines above if (name == ".note") because this statement does not use contentType and returns immediately.

[• tstellarAMD]

lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.cpp

18–33

These functions are actually calling the implementation of the parent class's parent instead of the parent's. This is done to avoid having c runtime symbols added to the binary.

[• tstellarAMD]

Here is an updated patch.

[• tstellarAMD]

Ping.

[ruiu]

LGTM, but please wait for Simon's LGTM.

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.cpp

41

Remove this "using".

[atanasyan]

LGTM

include/lld/Core/Reference.h

enum class KindNamespace {
     COFF    = 3,
     mach_o  = 4,
   };
 
   KindNamespace kindNamespace() const { return (KindNamespace)_kindNamespace; }
   void setKindNamespace(KindNamespace ns) { _kindNamespace = (uint8_t)ns; }
 
   // Which architecture the kind value is for.
-  enum class KindArch { all, AArch64, ARM, Hexagon, Mips, x86, x86_64 };
+  enum class KindArch { all, AArch64, AMDGPU, ARM, Hexagon, Mips, x86, x86_64 };
 
   KindArch kindArch() const { return (KindArch)_kindArch; }
   void setKindArch(KindArch a) { _kindArch = (uint8_t)a; }
 
   typedef uint16_t KindValue;
 
   KindValue kindValue() const { return _kindValue; }
 

include/lld/ReaderWriter/ELFLinkingContext.h

 using llvm::object::ELF32LE;
 using llvm::object::ELF32BE;
 using llvm::object::ELF64LE;
 using llvm::object::ELF64BE;
 
 class ELFWriter;
 
 std::unique_ptr<ELFLinkingContext> createAArch64LinkingContext(llvm::Triple);
+std::unique_ptr<ELFLinkingContext> createAMDGPULinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createARMLinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createExampleLinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createHexagonLinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createMipsLinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createX86LinkingContext(llvm::Triple);
 std::unique_ptr<ELFLinkingContext> createX86_64LinkingContext(llvm::Triple);
 
 class TargetRelocationHandler {

lib/Driver/CMakeLists.txt

add_llvm_library(lldDriver
   WinLinkModuleDef.cpp
   LINK_LIBS
     lldConfig
     lldMachO
     lldCOFF
     lldPECOFF
     lldELF
     lldAArch64ELFTarget
+    lldAMDGPUELFTarget
     lldARMELFTarget
     lldHexagonELFTarget
     lldMipsELFTarget
     lldX86ELFTarget
     lldExampleSubTarget
     lldX86_64ELFTarget
     lldCore
     lldReaderWriter
     lldYAML
     LLVMObject
     LLVMOption
     LLVMSupport
   )
 
 add_dependencies(lldDriver DriverOptionsTableGen)
 

lib/Driver/GnuLdDriver.cpp

void GnuLdDriver::addPlatformSearchDirs(ELFLinkingContext &ctx,
   }
   ctx.addSearchPath("=/usr/lib");
 }
 
 std::unique_ptr<ELFLinkingContext>
 GnuLdDriver::createELFLinkingContext(llvm::Triple triple) {
   std::unique_ptr<ELFLinkingContext> p;
   if ((p = elf::createAArch64LinkingContext(triple))) return p;
+  if ((p = elf::createAMDGPULinkingContext(triple))) return p;
   if ((p = elf::createARMLinkingContext(triple))) return p;
   if ((p = elf::createExampleLinkingContext(triple))) return p;
   if ((p = elf::createHexagonLinkingContext(triple))) return p;
   if ((p = elf::createMipsLinkingContext(triple))) return p;
   if ((p = elf::createX86LinkingContext(triple))) return p;
   if ((p = elf::createX86_64LinkingContext(triple))) return p;
   return nullptr;
 }

lib/ReaderWriter/ELF/AMDGPU/AMDGPUELFFile.h

+//===- lib/ReaderWriter/ELF/AMDGPUELFFile.h -------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_READER_WRITER_ELF_AMDGPU_ELF_FILE_H
+#define LLD_READER_WRITER_ELF_AMDGPU_ELF_FILE_H
+
+#include "ELFReader.h"
+#include "AMDGPULinkingContext.h"
+
+namespace lld {
+namespace elf {
+
+class AMDGPUELFFile : public ELFFile<ELF64LE> {
+  typedef llvm::object::Elf_Shdr_Impl<ELF64LE> Elf_Shdr;
+  typedef llvm::object::Elf_Sym_Impl<ELF64LE> Elf_Sym;
+
+public:
+  AMDGPUELFFile(std::unique_ptr<MemoryBuffer> mb, ELFLinkingContext &ctx)
+      : ELFFile(std::move(mb), ctx) {}
+
+  bool
+  handleSectionWithNoSymbols(const Elf_Shdr *shdr,
+                             std::vector<const Elf_Sym *> &syms) const override;
+};
+
+} // elf
+} // lld
+
+#endif // LLD_READER_WRITER_ELF_AMDGPU_ELF_FILE_H

lib/ReaderWriter/ELF/AMDGPU/AMDGPUELFFile.cpp

+//===- lib/ReaderWriter/ELF/AMDGPUELFFile.cpp -----------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUELFFile.h"
+
+using namespace lld::elf;
+
+bool AMDGPUELFFile::handleSectionWithNoSymbols(
+    const Elf_Shdr *shdr, std::vector<const Elf_Sym *> &syms) const {
+  // We want to create atoms for note sections, because these sections
+  // contain information required by the hsa runtime.
+  if (shdr && shdr->sh_type == llvm::ELF::SHT_NOTE && syms.empty())
+    return true;
+
+  return ELFFile::handleSectionWithNoSymbols(shdr, syms);
+}

lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.h

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.h ---------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef AMDGPU_EXECUTABLE_WRITER_H
+#define AMDGPU_EXECUTABLE_WRITER_H
+
+#include "ExecutableWriter.h"
+#include "AMDGPULinkingContext.h"
+#include "AMDGPUSymbolTable.h"
+#include "AMDGPUTargetHandler.h"
+
+namespace lld {
+namespace elf {
+
+class AMDGPUTargetLayout;
+
+class AMDGPUExecutableWriter : public ExecutableWriter<ELF64LE> {
+public:
+  AMDGPUExecutableWriter(AMDGPULinkingContext &ctx, AMDGPUTargetLayout &layout);
+
+  unique_bump_ptr<SymbolTable<ELF64LE>> createSymbolTable() {
+    return unique_bump_ptr<SymbolTable<ELF64LE>>(new (this->_alloc)
+                                                     AMDGPUSymbolTable(_ctx));
+  }
+
+  void createImplicitFiles(std::vector<std::unique_ptr<File>> &Result) override;
+  void finalizeDefaultAtomValues() override;
+
+private:
+  AMDGPULinkingContext &_ctx;
+  AMDGPUTargetLayout &_targetLayout;
+};
+
+} // namespace elf
+} // namespace lld
+
+#endif // AMDGPU_EXECUTABLE_WRITER_H

lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.cpp

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPUExecutableWriter.cpp -------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUExecutableWriter.h"
+
+using namespace lld::elf;
+
+AMDGPUExecutableWriter::AMDGPUExecutableWriter(AMDGPULinkingContext &ctx,
+                                               AMDGPUTargetLayout &layout)
+    : ExecutableWriter(ctx, layout), _ctx(ctx), _targetLayout(layout) {}
+
+void AMDGPUExecutableWriter::createImplicitFiles(
+    std::vector<std::unique_ptr<File>> &Result) {
+  // ExecutableWriter::createImplicitFiles() adds C runtime symbols that we
+  // don't need, so we use the OutputELFWriter implementation instead.
+  OutputELFWriter<ELF64LE>::createImplicitFiles(Result);
+}
+
+void AMDGPUExecutableWriter::finalizeDefaultAtomValues() {
+
+  // ExecutableWriter::finalizeDefaultAtomValues() assumes the presence of
+  // C runtime symbols.  However, since we skip the call to
+  // ExecutableWriter::createImplicitFiles(), these symbols are never added
+  // and ExectuableWriter::finalizeDefaultAtomValues() will crash if we call
+  // it.
+  OutputELFWriter<ELF64LE>::finalizeDefaultAtomValues();
+}

lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.h

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.h ---------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_LINKING_CONTEXT_H
+#define LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_LINKING_CONTEXT_H
+
+#include "OutputELFWriter.h"
+#include "lld/ReaderWriter/ELFLinkingContext.h"
+#include "llvm/Object/ELF.h"
+#include "llvm/Support/ELF.h"
+
+namespace lld {
+namespace elf {
+
+class AMDGPULinkingContext final : public ELFLinkingContext {
+public:
+  int getMachineType() const override { return llvm::ELF::EM_AMDGPU; }
+  AMDGPULinkingContext(llvm::Triple triple);
+
+  void registerRelocationNames(Registry &r) override;
+
+  StringRef entrySymbolName() const override;
+};
+
+void setAMDGPUELFHeader(ELFHeader<ELF32LE> &elfHeader);
+void setAMDGPUELFHeader(ELFHeader<ELF64LE> &elfHeader);
+
+} // elf
+} // lld
+
+#endif // LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_LINKING_CONTEXT_H

lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.cpp

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPULinkingContext.cpp ---------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===------------------------------------------------------------------------===//
+
+#include "AMDGPULinkingContext.h"
+#include "AMDGPUTargetHandler.h"
+
+namespace lld {
+namespace elf {
+
+std::unique_ptr<ELFLinkingContext>
+createAMDGPULinkingContext(llvm::Triple triple) {
+  if (triple.getArch() == llvm::Triple::amdgcn)
+    return llvm::make_unique<AMDGPULinkingContext>(triple);
+  return nullptr;
+}
+
+AMDGPULinkingContext::AMDGPULinkingContext(llvm::Triple triple)
+    : ELFLinkingContext(triple, llvm::make_unique<AMDGPUTargetHandler>(*this)) {
+}
+
+static const Registry::KindStrings kindStrings[] = {LLD_KIND_STRING_END};
+
+void AMDGPULinkingContext::registerRelocationNames(Registry &registry) {
+  registry.addKindTable(Reference::KindNamespace::ELF,
+                        Reference::KindArch::AMDGPU, kindStrings);
+}
+
+void setAMDGPUELFHeader(ELFHeader<ELF64LE> &elfHeader) {
+  elfHeader.e_ident(llvm::ELF::EI_OSABI, ELFOSABI_AMDGPU_HSA);
+}
+
+StringRef AMDGPULinkingContext::entrySymbolName() const { return ""; }
+
+} // namespace elf
+} // namespace lld

lib/ReaderWriter/ELF/AMDGPU/AMDGPURelocationHandler.h

+//===- lld/ReaderWriter/ELF/AMDGPU/AMDGPURelocationHandler.h --------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_RELOCATION_HANDLER_H
+#define LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_RELOCATION_HANDLER_H
+
+#include "lld/ReaderWriter/ELFLinkingContext.h"
+
+namespace lld {
+namespace elf {
+class AMDGPUTargetHandler;
+class AMDGPUTargetLayout;
+
+class AMDGPUTargetRelocationHandler final : public TargetRelocationHandler {
+public:
+  AMDGPUTargetRelocationHandler(AMDGPUTargetLayout &layout)
+      : _targetLayout(layout) {}
+
+  std::error_code applyRelocation(ELFWriter &, llvm::FileOutputBuffer &,
+                                  const AtomLayout &,
+                                  const Reference &) const override;
+
+private:
+  AMDGPUTargetLayout &_targetLayout;
+};
+} // elf
+} // lld
+#endif

lib/ReaderWriter/ELF/AMDGPU/AMDGPURelocationHandler.cpp

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPURelocationHandler.cpp -----------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPURelocationHandler.h"
+
+using namespace lld::elf;
+
+std::error_code AMDGPUTargetRelocationHandler::applyRelocation(
+    ELFWriter &writer, llvm::FileOutputBuffer &buf, const AtomLayout &atom,
+    const Reference &ref) const {
+  return std::error_code();
+}

lib/ReaderWriter/ELF/AMDGPU/AMDGPUSymbolTable.h

+//===--------- lib/ReaderWriter/ELF/AMDGPU/AMDGPUSymbolTable.h ------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_SYMBOL_TABLE_H
+#define LLD_READER_WRITER_ELF_AMDGPU_AMDGPU_SYMBOL_TABLE_H
+
+#include "TargetLayout.h"
+
+namespace lld {
+namespace elf {
+
+/// \brief The SymbolTable class represents the symbol table in a ELF file
+class AMDGPUSymbolTable : public SymbolTable<ELF64LE> {
+public:
+  typedef llvm::object::Elf_Sym_Impl<ELF64LE> Elf_Sym;
+
+  AMDGPUSymbolTable(const ELFLinkingContext &ctx);
+
+  void addDefinedAtom(Elf_Sym &sym, const DefinedAtom *da,
+                      int64_t addr) override;
+};
+
+} // elf
+} // lld
+
+#endif

lib/ReaderWriter/ELF/AMDGPU/AMDGPUSymbolTable.cpp

+//===--------- lib/ReaderWriter/ELF/AMDGPU/AMDGPUSymbolTable.cpp ----------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUSymbolTable.h"
+#include "ELFFile.h"
+#include "Atoms.h"
+#include "SectionChunks.h"
+
+using namespace lld::elf;
+
+AMDGPUSymbolTable::AMDGPUSymbolTable(const ELFLinkingContext &ctx)
+    : SymbolTable(ctx, ".symtab", TargetLayout<ELF64LE>::ORDER_SYMBOL_TABLE) {}
+
+void AMDGPUSymbolTable::addDefinedAtom(Elf_Sym &sym, const DefinedAtom *da,
+                                       int64_t addr) {
+  SymbolTable::addDefinedAtom(sym, da, addr);
+
+  // FIXME: Only do this for kernel functions.
+  sym.setType(STT_AMDGPU_HSA_KERNEL);
+
+  // Make st_value section relative.
+  // FIXME: This is hack to give kernel symbols a section relative offset.
+  // Because of this hack only on kernel can be included in a binary file.
+  sym.st_value = 0;
+}

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.h

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.h ------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef AMDGPU_TARGET_HANDLER_H
+#define AMDGPU_TARGET_HANDLER_H
+
+#include "ELFReader.h"
+#include "AMDGPUELFFile.h"
+#include "AMDGPURelocationHandler.h"
+#include "TargetLayout.h"
+
+namespace lld {
+namespace elf {
+class AMDGPULinkingContext;
+
+class HSATextSection : public AtomSection<ELF64LE> {
+public:
+  HSATextSection(const ELFLinkingContext &ctx);
+};
+
+/// \brief TargetLayout for AMDGPU
+class AMDGPUTargetLayout final : public TargetLayout<ELF64LE> {
+public:
+  AMDGPUTargetLayout(AMDGPULinkingContext &ctx) : TargetLayout(ctx) {}
+
+  void assignSectionsToSegments() override;
+
+  /// \brief Gets or creates a section.
+  AtomSection<ELF64LE> *
+  createSection(StringRef name, int32_t contentType,
+                DefinedAtom::ContentPermissions contentPermissions,
+                TargetLayout::SectionOrder sectionOrder) override {
+
+    if (name == ".note") {
+      contentType = DefinedAtom::typeRONote;
+    }
+    if (name == ".text") {
+      return new (_allocator) HSATextSection(_ctx);
+    }
+    return TargetLayout::createSection(name, contentType, contentPermissions,
+                                       sectionOrder);
+  }
+};
+
+/// \brief TargetHandler for AMDGPU
+class AMDGPUTargetHandler final : public TargetHandler {
+public:
+  AMDGPUTargetHandler(AMDGPULinkingContext &targetInfo);
+
+  const TargetRelocationHandler &getRelocationHandler() const override {
+    return *_relocationHandler;
+  }
+
+  std::unique_ptr<Reader> getObjReader() override {
+    return llvm::make_unique<ELFReader<AMDGPUELFFile>>(_ctx);
+  }
+
+  std::unique_ptr<Reader> getDSOReader() override {
+    return llvm::make_unique<ELFReader<DynamicFile<ELF64LE>>>(_ctx);
+  }
+
+  std::unique_ptr<Writer> getWriter() override;
+
+private:
+  AMDGPULinkingContext &_ctx;
+  std::unique_ptr<AMDGPUTargetLayout> _targetLayout;
+  std::unique_ptr<AMDGPUTargetRelocationHandler> _relocationHandler;
+};
+
+void finalizeAMDGPURuntimeAtomValues(AMDGPUTargetLayout &layout);
+
+} // end namespace elf
+} // end namespace lld
+
+#endif

lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.cpp

+//===- lib/ReaderWriter/ELF/AMDGPU/AMDGPUTargetHandler.cpp ----------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TargetLayout.h"
+#include "AMDGPUExecutableWriter.h"
+#include "AMDGPULinkingContext.h"
+#include "AMDGPUTargetHandler.h"
+#include "llvm/Support/ELF.h"
+
+using namespace llvm::ELF;
+
+using llvm::makeArrayRef;
+
+namespace lld {
+namespace elf {
+
+AMDGPUTargetHandler::AMDGPUTargetHandler(AMDGPULinkingContext &ctx)
+    : _ctx(ctx), _targetLayout(new AMDGPUTargetLayout(ctx)),
+      _relocationHandler(new AMDGPUTargetRelocationHandler(*_targetLayout)) {}
+
+std::unique_ptr<Writer> AMDGPUTargetHandler::getWriter() {
+  switch (_ctx.getOutputELFType()) {
+  case llvm::ELF::ET_EXEC:
+    return llvm::make_unique<AMDGPUExecutableWriter>(_ctx, *_targetLayout);
+  case llvm::ELF::ET_DYN:
+    llvm_unreachable("TODO: support dynamic libraries");
+  case llvm::ELF::ET_REL:
+    llvm_unreachable("TODO: support -r mode");
+  default:
+    llvm_unreachable("unsupported output type");
+  }
+}
+
+using namespace llvm::ELF;
+
+HSATextSection::HSATextSection(const ELFLinkingContext &ctx)
+    : AtomSection(ctx, ".text", DefinedAtom::typeCode, 0, 0) {
+  _type = SHT_PROGBITS;
+  _flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR | SHF_AMDGPU_HSA_AGENT |
+           SHF_AMDGPU_HSA_CODE;
+
+  // FIXME: What alignment should we use here?
+  _alignment = 4096;
+}
+
+void AMDGPUTargetLayout::assignSectionsToSegments() {
+
+  TargetLayout::assignSectionsToSegments();
+  for (auto osi : _outputSections) {
+    for (auto section : osi->sections()) {
+      StringRef InputSectionName = section->inputSectionName();
+      if (InputSectionName != ".text")
+        continue;
+
+      Segment<ELF64LE> *segment = new (_allocator) Segment<ELF64LE>(
+          _ctx, "PT_AMDGPU_HSA_LOAD_CODE_AGENT", PT_AMDGPU_HSA_LOAD_CODE_AGENT);
+      _segments.push_back(segment);
+      assert(segment);
+      segment->append(section);
+    }
+  }
+}
+
+} // namespace elf
+} // namespace lld

lib/ReaderWriter/ELF/AMDGPU/CMakeLists.txt

+add_llvm_library(lldAMDGPUELFTarget
+  AMDGPUELFFile.cpp
+  AMDGPUExecutableWriter.cpp
+  AMDGPULinkingContext.cpp
+  AMDGPURelocationHandler.cpp
+  AMDGPUSymbolTable.cpp
+  AMDGPUTargetHandler.cpp
+  LINK_LIBS
+    lldELF
+    lldReaderWriter
+    lldCore
+    LLVMObject
+    LLVMSupport
+  )

lib/ReaderWriter/ELF/CMakeLists.txt

 include_directories(.)
 
 add_subdirectory(X86)
 add_subdirectory(X86_64)
 add_subdirectory(Mips)
 add_subdirectory(Hexagon)
 add_subdirectory(AArch64)
 add_subdirectory(ARM)
+add_subdirectory(AMDGPU)

lib/ReaderWriter/ELF/ELFFile.h

protected:
   ErrorOr<ArrayRef<uint8_t>> getSectionContents(const Elf_Shdr *shdr) const {
     if (!shdr || !sectionOccupiesMemorySpace(shdr))
       return ArrayRef<uint8_t>();
     return _objFile->getSectionContents(shdr);
   }
 
   /// Determines if the target wants to create an atom for a section that has no
   /// symbol references.
-  bool handleSectionWithNoSymbols(const Elf_Shdr *shdr,
-                                  std::vector<const Elf_Sym *> &syms) const {
+  virtual bool
+  handleSectionWithNoSymbols(const Elf_Shdr *shdr,
     return shdr &&
            (shdr->sh_type == llvm::ELF::SHT_PROGBITS ||
             shdr->sh_type == llvm::ELF::SHT_INIT_ARRAY ||
             shdr->sh_type == llvm::ELF::SHT_FINI_ARRAY) &&
            syms.empty();
   }
 
   /// Handle creation of atoms for .gnu.linkonce sections.

lib/ReaderWriter/ELF/ELFLinkingContext.cpp

uint16_t ELFLinkingContext::getOutputMachine() const {
   case llvm::Triple::mipsel:
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el:
     return llvm::ELF::EM_MIPS;
   case llvm::Triple::aarch64:
     return llvm::ELF::EM_AARCH64;
   case llvm::Triple::arm:
     return llvm::ELF::EM_ARM;
+  case llvm::Triple::amdgcn:
+    return llvm::ELF::EM_AMDGPU;
   default:
     llvm_unreachable("Unhandled arch");
   }
 }
 
 StringRef ELFLinkingContext::entrySymbolName() const {
   if (_outputELFType == llvm::ELF::ET_EXEC && _entrySymbolName.empty())
     return "_start";

test/elf/AMDGPU/hsa.test

+# RUN: yaml2obj -format=elf %s > %t.obj
+# RUN: lld -flavor gnu -target amdgcn--hsa %t.obj -o %t.exe --noinhibit-exec
+# RUN: llvm-readobj -h -program-headers -s -symbols %t.exe | FileCheck %s
+
+# CHECK: ElfHeader {
+# CHECK:  Ident {
+# CHECK: Class: 64-bit (0x2)
+# CHECK: DataEncoding: LittleEndian (0x1)
+# CHECK: Machine: EM_AMDGPU (0xE0)
+
+
+# CHECK: Section {
+# CHECK: Name: .text
+# CHECK: Type: SHT_PROGBITS (0x1)
+# CHECK: Flags [ (0xC00007
+# CHECK: SHF_ALLOC (0x2)
+# CHECK: SHF_AMDGPU_HSA_AGENT (0x800000)
+# CHECK: SHF_AMDGPU_HSA_CODE (0x400000)
+# CHECK: SHF_EXECINSTR (0x4)
+# CHECK: SHF_WRITE (0x1)
+#
+# CHECK: Symbol {
+# CHECK: Name: kernel
+# CHECK: Value: 0x0
+# CHECK: Binding: Local (0x0)
+# CHECK: Type: STT_AMDGPU_HSA_KERNEL (0xA)
+
+# CHECK: ProgramHeader {
+# CHECK: Type: PT_AMDGPU_HSA_LOAD_CODE_AGENT (0x60000003)
+
+---
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  OSABI:           ELFOSABI_GNU
+  Type:            ET_REL
+  Machine:         EM_AMDGPU
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+  - Name:            .note
+    Type:            SHT_NOTE
+    AddressAlign:    0x0000000000000001
+    Content:         '00'
+Symbols:
+  Local:
+    - Name:            kernel
+      Type:            STT_GNU_IFUNC
+      Section:         .text
+...