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[OpenMP] Add basic support for properly handling static libraries 

Currently we handle static libraries like any other object in the
linker wrapper. However, this does not preserve the sematnics that
dictate static libraries should be lazily loaded as the symbols are
needed. This allows us to ignore linking in architectures that are not
used by the main application being compiled. This patch adds the basic
support for detecting if a file came from a static library, and only
including it in the link job if it's used by other object files.

This patch only adds the basic support, to be more correct we should
check the symbols and only inclue the library if the link job contains
symbols that are needed. Ideally we could just put this on the linker
itself, but nvlink doesn't seem to support `.a` files.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D125092
This commit is contained in:
Joseph Huber 2022-05-06 09:37:08 -04:00
parent edaeab664c
commit e12905b4d5
2 changed files with 50 additions and 15 deletions
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12
clang/test/Driver/linker-wrapper.c
View File

@ -48,3 +48,15 @@
// RUN: /usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=CUDA_OMP_LINK
// CUDA_OMP_LINK: nvlink{{.*}}-m64 -o {{.*}}.out -arch sm_70 {{.*}}.o {{.*}}.o
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t-lib.o \
// RUN: -fembed-offload-object=%S/Inputs/dummy-elf.o,openmp,nvptx64-nvida-cuda,sm_70 \
// RUN: -fembed-offload-object=%S/Inputs/dummy-elf.o,openmp,nvptx64-nvida-cuda,sm_52
// RUN: llvm-ar rcs %t.a %t-lib.o
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t-obj.o \
// RUN: -fembed-offload-object=%S/Inputs/dummy-elf.o,openmp,nvptx64-nvida-cuda,sm_70
// RUN: clang-linker-wrapper --host-triple x86_64-unknown-linux-gnu --dry-run -linker-path \
// RUN: /usr/bin/ld -- %t.a %t-obj.o -o a.out 2>&1 | FileCheck %s --check-prefix=STATIC-LIBRARY
// STATIC-LIBRARY: nvlink{{.*}} -arch sm_70
// STATIC-LIBRARY-NOT: nvlink{{.*}} -arch sm_50

53
clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
View File

@ -167,13 +167,15 @@ static constexpr unsigned FatbinaryOffset = 0x50;
/// Information for a device offloading file extracted from the host.
struct DeviceFile {
DeviceFile(StringRef Kind, StringRef TheTriple, StringRef Arch,
StringRef Filename)
: Kind(Kind), TheTriple(TheTriple), Arch(Arch), Filename(Filename) {}
StringRef Filename, bool IsLibrary = false)
: Kind(Kind), TheTriple(TheTriple), Arch(Arch), Filename(Filename),
IsLibrary(IsLibrary) {}
std::string Kind;
std::string TheTriple;
std::string Arch;
std::string Filename;
bool IsLibrary;
};
namespace llvm {
@ -208,7 +210,8 @@ namespace {
Expected<Optional<std::string>>
extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
SmallVectorImpl<DeviceFile> &DeviceFiles);
SmallVectorImpl<DeviceFile> &DeviceFiles,
bool IsLibrary = false);
void printCommands(ArrayRef<StringRef> CmdArgs) {
if (CmdArgs.empty())
@ -324,7 +327,8 @@ void removeFromCompilerUsed(Module &M, GlobalValue &Value) {
/// buffer \p Contents. The buffer is expected to contain a valid offloading
/// binary format.
Error extractOffloadFiles(StringRef Contents, StringRef Prefix,
SmallVectorImpl<DeviceFile> &DeviceFiles) {
SmallVectorImpl<DeviceFile> &DeviceFiles,
bool IsLibrary = false) {
uint64_t Offset = 0;
// There could be multiple offloading binaries stored at this section.
while (Offset < Contents.size()) {
@ -361,7 +365,7 @@ Error extractOffloadFiles(StringRef Contents, StringRef Prefix,
return E;
DeviceFiles.emplace_back(Kind, Binary.getTriple(), Binary.getArch(),
TempFile);
TempFile, IsLibrary);
Offset += Binary.getSize();
}
@ -371,7 +375,8 @@ Error extractOffloadFiles(StringRef Contents, StringRef Prefix,
Expected<Optional<std::string>>
extractFromBinary(const ObjectFile &Obj,
SmallVectorImpl<DeviceFile> &DeviceFiles) {
SmallVectorImpl<DeviceFile> &DeviceFiles,
bool IsLibrary = false) {
StringRef Extension = sys::path::extension(Obj.getFileName()).drop_front();
StringRef Prefix = sys::path::stem(Obj.getFileName());
SmallVector<StringRef, 4> ToBeStripped;
@ -386,7 +391,8 @@ extractFromBinary(const ObjectFile &Obj,
if (!Contents)
return Contents.takeError();
if (Error Err = extractOffloadFiles(*Contents, Prefix, DeviceFiles))
if (Error Err =
extractOffloadFiles(*Contents, Prefix, DeviceFiles, IsLibrary))
return std::move(Err);
ToBeStripped.push_back(*Name);
@ -447,7 +453,8 @@ extractFromBinary(const ObjectFile &Obj,
Expected<Optional<std::string>>
extractFromBitcode(std::unique_ptr<MemoryBuffer> Buffer,
SmallVectorImpl<DeviceFile> &DeviceFiles) {
SmallVectorImpl<DeviceFile> &DeviceFiles,
bool IsLibrary = false) {
LLVMContext Context;
SMDiagnostic Err;
std::unique_ptr<Module> M = getLazyIRModule(std::move(Buffer), Err, Context);
@ -473,7 +480,8 @@ extractFromBitcode(std::unique_ptr<MemoryBuffer> Buffer,
StringRef Contents = CDS->getAsString();
if (Error Err = extractOffloadFiles(Contents, Prefix, DeviceFiles))
if (Error Err =
extractOffloadFiles(Contents, Prefix, DeviceFiles, IsLibrary))
return std::move(Err);
ToBeDeleted.push_back(&GV);
@ -521,7 +529,8 @@ extractFromArchive(const Archive &Library,
std::unique_ptr<MemoryBuffer> ChildBuffer =
MemoryBuffer::getMemBuffer(*ChildBufferRefOrErr, false);
auto FileOrErr = extractFromBuffer(std::move(ChildBuffer), DeviceFiles);
auto FileOrErr = extractFromBuffer(std::move(ChildBuffer), DeviceFiles,
/*IsLibrary*/ true);
if (!FileOrErr)
return FileOrErr.takeError();
@ -573,11 +582,11 @@ extractFromArchive(const Archive &Library,
/// device code stripped from the buffer will be returned.
Expected<Optional<std::string>>
extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
SmallVectorImpl<DeviceFile> &DeviceFiles) {
SmallVectorImpl<DeviceFile> &DeviceFiles, bool IsLibrary) {
file_magic Type = identify_magic(Buffer->getBuffer());
switch (Type) {
case file_magic::bitcode:
return extractFromBitcode(std::move(Buffer), DeviceFiles);
return extractFromBitcode(std::move(Buffer), DeviceFiles, IsLibrary);
case file_magic::elf_relocatable:
case file_magic::macho_object:
case file_magic::coff_object: {
@ -585,7 +594,7 @@ extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
ObjectFile::createObjectFile(*Buffer, Type);
if (!ObjFile)
return ObjFile.takeError();
return extractFromBinary(*ObjFile->get(), DeviceFiles);
return extractFromBinary(*ObjFile->get(), DeviceFiles, IsLibrary);
}
case file_magic::archive: {
Expected<std::unique_ptr<llvm::object::Archive>> LibFile =
@ -1127,8 +1136,22 @@ Error linkDeviceFiles(ArrayRef<DeviceFile> DeviceFiles,
SmallVectorImpl<std::string> &LinkedImages) {
// Get the list of inputs for a specific device.
DenseMap<DeviceFile, SmallVector<std::string, 4>> LinkerInputMap;
for (auto &File : DeviceFiles)
LinkerInputMap[File].push_back(File.Filename);
SmallVector<DeviceFile, 4> LibraryFiles;
for (auto &File : DeviceFiles) {
if (File.IsLibrary)
LibraryFiles.push_back(File);
else
LinkerInputMap[File].push_back(File.Filename);
}
// Static libraries are loaded lazily as-needed, only add them if other files
// are present.
// TODO: We need to check the symbols as well, static libraries are only
// loaded if they contain symbols that are currently undefined or common
// in the symbol table.
for (auto &File : LibraryFiles)
if (LinkerInputMap.count(File))
LinkerInputMap[File].push_back(File.Filename);
// Try to link each device toolchain.
for (auto &LinkerInput : LinkerInputMap) {