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//===- Offloading.cpp - Utilities for handling offloading code -*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/Object/OffloadBinary.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/BinaryFormat/Magic.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Module.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/Archive.h"
#include "llvm/Object/ArchiveWriter.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/Error.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/SourceMgr.h"
using namespace llvm;
using namespace llvm::object;
namespace {
/// Attempts to extract all the embedded device images contained inside the
/// buffer \p Contents. The buffer is expected to contain a valid offloading
/// binary format.
Error extractOffloadFiles(MemoryBufferRef Contents,
SmallVectorImpl<OffloadFile> &Binaries) {
uint64_t Offset = 0;
// There could be multiple offloading binaries stored at this section.
while (Offset < Contents.getBuffer().size()) {
std::unique_ptr<MemoryBuffer> Buffer =
MemoryBuffer::getMemBuffer(Contents.getBuffer().drop_front(Offset), "",
/*RequiresNullTerminator*/ false);
if (!isAddrAligned(Align(OffloadBinary::getAlignment()),
Buffer = MemoryBuffer::getMemBufferCopy(Buffer->getBuffer(),
auto BinaryOrErr = OffloadBinary::create(*Buffer);
if (!BinaryOrErr)
return BinaryOrErr.takeError();
OffloadBinary &Binary = **BinaryOrErr;
// Create a new owned binary with a copy of the original memory.
std::unique_ptr<MemoryBuffer> BufferCopy = MemoryBuffer::getMemBufferCopy(
auto NewBinaryOrErr = OffloadBinary::create(*BufferCopy);
if (!NewBinaryOrErr)
return NewBinaryOrErr.takeError();
Binaries.emplace_back(std::move(*NewBinaryOrErr), std::move(BufferCopy));
Offset += Binary.getSize();
return Error::success();
// Extract offloading binaries from an Object file \p Obj.
Error extractFromObject(const ObjectFile &Obj,
SmallVectorImpl<OffloadFile> &Binaries) {
assert((Obj.isELF() || Obj.isCOFF()) && "Invalid file type");
for (SectionRef Sec : Obj.sections()) {
// ELF files contain a section with the LLVM_OFFLOADING type.
if (Obj.isELF() &&
static_cast<ELFSectionRef>(Sec).getType() != ELF::SHT_LLVM_OFFLOADING)
// COFF has no section types so we rely on the name of the section.
if (Obj.isCOFF()) {
Expected<StringRef> NameOrErr = Sec.getName();
if (!NameOrErr)
return NameOrErr.takeError();
if (!NameOrErr->equals(".llvm.offloading"))
Expected<StringRef> Buffer = Sec.getContents();
if (!Buffer)
return Buffer.takeError();
MemoryBufferRef Contents(*Buffer, Obj.getFileName());
if (Error Err = extractOffloadFiles(Contents, Binaries))
return Err;
return Error::success();
Error extractFromBitcode(MemoryBufferRef Buffer,
SmallVectorImpl<OffloadFile> &Binaries) {
LLVMContext Context;
SMDiagnostic Err;
std::unique_ptr<Module> M = getLazyIRModule(
MemoryBuffer::getMemBuffer(Buffer, /*RequiresNullTerminator=*/false), Err,
if (!M)
return createStringError(inconvertibleErrorCode(),
"Failed to create module");
// Extract offloading data from globals referenced by the
// `llvm.embedded.object` metadata with the `.llvm.offloading` section.
auto *MD = M->getNamedMetadata("llvm.embedded.objects");
if (!MD)
return Error::success();
for (const MDNode *Op : MD->operands()) {
if (Op->getNumOperands() < 2)
MDString *SectionID = dyn_cast<MDString>(Op->getOperand(1));
if (!SectionID || SectionID->getString() != ".llvm.offloading")
GlobalVariable *GV =
if (!GV)
auto *CDS = dyn_cast<ConstantDataSequential>(GV->getInitializer());
if (!CDS)
MemoryBufferRef Contents(CDS->getAsString(), M->getName());
if (Error Err = extractOffloadFiles(Contents, Binaries))
return Err;
return Error::success();
Error extractFromArchive(const Archive &Library,
SmallVectorImpl<OffloadFile> &Binaries) {
// Try to extract device code from each file stored in the static archive.
Error Err = Error::success();
for (auto Child : Library.children(Err)) {
auto ChildBufferOrErr = Child.getMemoryBufferRef();
if (!ChildBufferOrErr)
return ChildBufferOrErr.takeError();
std::unique_ptr<MemoryBuffer> ChildBuffer =
MemoryBuffer::getMemBuffer(*ChildBufferOrErr, false);
// Check if the buffer has the required alignment.
if (!isAddrAligned(Align(OffloadBinary::getAlignment()),
ChildBuffer = MemoryBuffer::getMemBufferCopy(
if (Error Err = extractOffloadBinaries(*ChildBuffer, Binaries))
return Err;
if (Err)
return Err;
return Error::success();
} // namespace
OffloadBinary::create(MemoryBufferRef Buf) {
if (Buf.getBufferSize() < sizeof(Header) + sizeof(Entry))
return errorCodeToError(object_error::parse_failed);
// Check for 0x10FF1OAD magic bytes.
if (identify_magic(Buf.getBuffer()) != file_magic::offload_binary)
return errorCodeToError(object_error::parse_failed);
// Make sure that the data has sufficient alignment.
if (!isAddrAligned(Align(getAlignment()), Buf.getBufferStart()))
return errorCodeToError(object_error::parse_failed);
const char *Start = Buf.getBufferStart();
const Header *TheHeader = reinterpret_cast<const Header *>(Start);
if (TheHeader->Version != OffloadBinary::Version)
return errorCodeToError(object_error::parse_failed);
if (TheHeader->Size > Buf.getBufferSize() ||
TheHeader->EntryOffset > TheHeader->Size - sizeof(Entry) ||
TheHeader->EntrySize > TheHeader->Size - sizeof(Header))
return errorCodeToError(object_error::unexpected_eof);
const Entry *TheEntry =
reinterpret_cast<const Entry *>(&Start[TheHeader->EntryOffset]);
if (TheEntry->ImageOffset > Buf.getBufferSize() ||
TheEntry->StringOffset > Buf.getBufferSize())
return errorCodeToError(object_error::unexpected_eof);
return std::unique_ptr<OffloadBinary>(
new OffloadBinary(Buf, TheHeader, TheEntry));
SmallString<0> OffloadBinary::write(const OffloadingImage &OffloadingData) {
// Create a null-terminated string table with all the used strings.
StringTableBuilder StrTab(StringTableBuilder::ELF);
for (auto &KeyAndValue : OffloadingData.StringData) {
uint64_t StringEntrySize =
sizeof(StringEntry) * OffloadingData.StringData.size();
// Make sure the image we're wrapping around is aligned as well.
uint64_t BinaryDataSize = alignTo(sizeof(Header) + sizeof(Entry) +
StringEntrySize + StrTab.getSize(),
// Create the header and fill in the offsets. The entry will be directly
// placed after the header in memory. Align the size to the alignment of the
// header so this can be placed contiguously in a single section.
Header TheHeader;
TheHeader.Size = alignTo(
BinaryDataSize + OffloadingData.Image->getBufferSize(), getAlignment());
TheHeader.EntryOffset = sizeof(Header);
TheHeader.EntrySize = sizeof(Entry);
// Create the entry using the string table offsets. The string table will be
// placed directly after the entry in memory, and the image after that.
Entry TheEntry;
TheEntry.TheImageKind = OffloadingData.TheImageKind;
TheEntry.TheOffloadKind = OffloadingData.TheOffloadKind;
TheEntry.Flags = OffloadingData.Flags;
TheEntry.StringOffset = sizeof(Header) + sizeof(Entry);
TheEntry.NumStrings = OffloadingData.StringData.size();
TheEntry.ImageOffset = BinaryDataSize;
TheEntry.ImageSize = OffloadingData.Image->getBufferSize();
SmallString<0> Data;
raw_svector_ostream OS(Data);
OS << StringRef(reinterpret_cast<char *>(&TheHeader), sizeof(Header));
OS << StringRef(reinterpret_cast<char *>(&TheEntry), sizeof(Entry));
for (auto &KeyAndValue : OffloadingData.StringData) {
uint64_t Offset = sizeof(Header) + sizeof(Entry) + StringEntrySize;
StringEntry Map{Offset + StrTab.getOffset(KeyAndValue.first),
Offset + StrTab.getOffset(KeyAndValue.second)};
OS << StringRef(reinterpret_cast<char *>(&Map), sizeof(StringEntry));
// Add padding to required image alignment.
OS.write_zeros(TheEntry.ImageOffset - OS.tell());
OS << OffloadingData.Image->getBuffer();
// Add final padding to required alignment.
assert(TheHeader.Size >= OS.tell() && "Too much data written?");
OS.write_zeros(TheHeader.Size - OS.tell());
assert(TheHeader.Size == OS.tell() && "Size mismatch");
return Data;
Error object::extractOffloadBinaries(MemoryBufferRef Buffer,
SmallVectorImpl<OffloadFile> &Binaries) {
file_magic Type = identify_magic(Buffer.getBuffer());
switch (Type) {
case file_magic::bitcode:
return extractFromBitcode(Buffer, Binaries);
case file_magic::elf_relocatable:
case file_magic::elf_executable:
case file_magic::elf_shared_object:
case file_magic::coff_object: {
Expected<std::unique_ptr<ObjectFile>> ObjFile =
ObjectFile::createObjectFile(Buffer, Type);
if (!ObjFile)
return ObjFile.takeError();
return extractFromObject(*ObjFile->get(), Binaries);
case file_magic::archive: {
Expected<std::unique_ptr<llvm::object::Archive>> LibFile =
if (!LibFile)
return LibFile.takeError();
return extractFromArchive(*LibFile->get(), Binaries);
case file_magic::offload_binary:
return extractOffloadFiles(Buffer, Binaries);
return Error::success();
OffloadKind object::getOffloadKind(StringRef Name) {
return llvm::StringSwitch<OffloadKind>(Name)
.Case("openmp", OFK_OpenMP)
.Case("cuda", OFK_Cuda)
.Case("hip", OFK_HIP)
StringRef object::getOffloadKindName(OffloadKind Kind) {
switch (Kind) {
case OFK_OpenMP:
return "openmp";
case OFK_Cuda:
return "cuda";
case OFK_HIP:
return "hip";
return "none";
ImageKind object::getImageKind(StringRef Name) {
return llvm::StringSwitch<ImageKind>(Name)
.Case("o", IMG_Object)
.Case("bc", IMG_Bitcode)
.Case("cubin", IMG_Cubin)
.Case("fatbin", IMG_Fatbinary)
.Case("s", IMG_PTX)
StringRef object::getImageKindName(ImageKind Kind) {
switch (Kind) {
case IMG_Object:
return "o";
case IMG_Bitcode:
return "bc";
case IMG_Cubin:
return "cubin";
case IMG_Fatbinary:
return "fatbin";
case IMG_PTX:
return "s";
return "";