[clang] d074458 - [Clang] Initial support for linking offloading code in tool
Joseph Huber via cfe-commits
cfe-commits at lists.llvm.org
Mon Jan 31 20:11:55 PST 2022
Author: Joseph Huber
Date: 2022-01-31T23:11:41-05:00
New Revision: d0744585f9ea842ca97855b2e002fddc893c4a92
URL: https://github.com/llvm/llvm-project/commit/d0744585f9ea842ca97855b2e002fddc893c4a92
DIFF: https://github.com/llvm/llvm-project/commit/d0744585f9ea842ca97855b2e002fddc893c4a92.diff
LOG: [Clang] Initial support for linking offloading code in tool
This patch adds the initial support for linking NVPTX offloading code
using the clang-linker-wrapper tool. This uses the extracted device
files and runs `nvlink` on them. Currently this is then passed to the
existing toolchain for creating linkable OpenMP offloading programs
using `clang-offload-wrapper` and compiling it manually using `llc`.
More work is required to support LTO, Bitcode linking, AMDGPU, and x86
offloading.
Depends on D116545
Differential Revision: https://reviews.llvm.org/D116627
Added:
Modified:
clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
Removed:
################################################################################
diff --git a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
index bbbdffc534a66..0072ce7a0080b 100644
--- a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
+++ b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
@@ -28,6 +28,7 @@
#include "llvm/Support/Errc.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Host.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
@@ -59,22 +60,26 @@ static cl::opt<std::string> LinkerUserPath("linker-path",
// Do not parse linker options.
static cl::list<std::string>
- LinkerArgs(cl::Sink, cl::desc("<options to be passed to linker>..."));
+ HostLinkerArgs(cl::Sink, cl::desc("<options to be passed to linker>..."));
/// Path of the current binary.
static std::string LinkerExecutable;
+static SmallVector<std::string, 16> TempFiles;
/// Magic section string that marks the existence of offloading data. The
/// section string will be formatted as `.llvm.offloading.<triple>.<arch>`.
-#define OFFLOAD_SECTION_MAGIC_STR ".llvm.offloading"
+#define OFFLOAD_SECTION_MAGIC_STR ".llvm.offloading."
+/// Information for a device offloading file extracted from the host.
struct DeviceFile {
DeviceFile(StringRef TheTriple, StringRef Arch, StringRef Filename)
: TheTriple(TheTriple), Arch(Arch), Filename(Filename) {}
- const Triple TheTriple;
+ const std::string TheTriple;
const std::string Arch;
const std::string Filename;
+
+ operator std::string() const { return TheTriple + "-" + Arch; }
};
namespace {
@@ -83,6 +88,16 @@ Expected<Optional<std::string>>
extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
SmallVectorImpl<DeviceFile> &DeviceFiles);
+static StringRef getDeviceFileExtension(StringRef DeviceTriple,
+ bool IsBitcode = false) {
+ Triple TheTriple(DeviceTriple);
+ if (TheTriple.isAMDGPU() || IsBitcode)
+ return "bc";
+ if (TheTriple.isNVPTX())
+ return "cubin";
+ return "o";
+}
+
Error runLinker(std::string &LinkerPath, SmallVectorImpl<std::string> &Args) {
std::vector<StringRef> LinkerArgs;
LinkerArgs.push_back(LinkerPath);
@@ -150,9 +165,12 @@ extractFromBinary(const ObjectFile &Obj,
if (Expected<StringRef> Contents = Sec.getContents()) {
SmallString<128> TempFile;
+ StringRef DeviceExtension = getDeviceFileExtension(
+ DeviceTriple, identify_magic(*Contents) == file_magic::bitcode);
if (std::error_code EC = sys::fs::createTemporaryFile(
- Prefix + "-device-" + DeviceTriple, Extension, TempFile))
+ Prefix + "-device-" + DeviceTriple, DeviceExtension, TempFile))
return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
Expected<std::unique_ptr<FileOutputBuffer>> OutputOrErr =
FileOutputBuffer::create(TempFile, Sec.getSize());
@@ -173,10 +191,7 @@ extractFromBinary(const ObjectFile &Obj,
// We will use llvm-strip to remove the now unneeded section containing the
// offloading code.
- ErrorOr<std::string> StripPath = sys::findProgramByName(
- "llvm-strip", sys::path::parent_path(LinkerExecutable));
- if (!StripPath)
- StripPath = sys::findProgramByName("llvm-strip");
+ ErrorOr<std::string> StripPath = sys::findProgramByName("llvm-strip");
if (!StripPath)
return createStringError(StripPath.getError(),
"Unable to find 'llvm-strip' in path");
@@ -185,6 +200,7 @@ extractFromBinary(const ObjectFile &Obj,
if (std::error_code EC =
sys::fs::createTemporaryFile(Prefix + "-host", Extension, TempFile))
return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
SmallVector<StringRef, 8> StripArgs;
StripArgs.push_back(*StripPath);
@@ -237,9 +253,12 @@ extractFromBitcode(std::unique_ptr<MemoryBuffer> Buffer,
StringRef Contents = CDS->getAsString();
SmallString<128> TempFile;
+ StringRef DeviceExtension = getDeviceFileExtension(
+ DeviceTriple, identify_magic(Contents) == file_magic::bitcode);
if (std::error_code EC = sys::fs::createTemporaryFile(
- Prefix + "-device-" + DeviceTriple, Extension, TempFile))
+ Prefix + "-device-" + DeviceTriple, DeviceExtension, TempFile))
return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
Expected<std::unique_ptr<FileOutputBuffer>> OutputOrErr =
FileOutputBuffer::create(TempFile, Contents.size());
@@ -271,6 +290,8 @@ extractFromBitcode(std::unique_ptr<MemoryBuffer> Buffer,
if (std::error_code EC =
sys::fs::createTemporaryFile(Prefix + "-host", Extension, TempFile))
return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
+
std::error_code EC;
raw_fd_ostream HostOutput(TempFile, EC, sys::fs::OF_None);
if (EC)
@@ -341,6 +362,7 @@ extractFromArchive(const Archive &Library,
if (std::error_code EC =
sys::fs::createTemporaryFile(Prefix + "-host", Extension, TempFile))
return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
std::unique_ptr<MemoryBuffer> Buffer =
MemoryBuffer::getMemBuffer(Library.getMemoryBufferRef(), false);
@@ -380,8 +402,153 @@ extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
default:
return errorCodeToError(object_error::invalid_file_type);
}
+}
+
+// TODO: Move these to a separate file.
+namespace nvptx {
+Expected<std::string> link(ArrayRef<StringRef> InputFiles,
+ ArrayRef<std::string> LinkerArgs, Triple TheTriple,
+ StringRef Arch) {
+ // NVPTX uses the nvlink binary to link device object files.
+ ErrorOr<std::string> NvlinkPath = sys::findProgramByName("nvlink");
+ if (!NvlinkPath)
+ return createStringError(NvlinkPath.getError(),
+ "Unable to find 'nvlink' in path");
+
+ // Create a new file to write the linked device image to.
+ SmallString<128> TempFile;
+ if (std::error_code EC = sys::fs::createTemporaryFile(
+ TheTriple.getArchName() + "-" + Arch + "-image", "out", TempFile))
+ return createFileError(TempFile, EC);
+ TempFiles.push_back(static_cast<std::string>(TempFile));
+
+ // TODO: Pass in arguments like `-g` and `-v` from the driver.
+ SmallVector<StringRef, 16> CmdArgs;
+ CmdArgs.push_back(*NvlinkPath);
+ CmdArgs.push_back(TheTriple.isArch64Bit() ? "-m64" : "-m32");
+ CmdArgs.push_back("-o");
+ CmdArgs.push_back(TempFile);
+ CmdArgs.push_back("-arch");
+ CmdArgs.push_back(Arch);
+
+ // Copy system library paths used by the host linker.
+ for (StringRef Arg : LinkerArgs)
+ if (Arg.startswith("-L"))
+ CmdArgs.push_back(Arg);
+
+ // Add extracted input files.
+ for (auto Input : InputFiles)
+ CmdArgs.push_back(Input);
+
+ if (sys::ExecuteAndWait(*NvlinkPath, CmdArgs))
+ return createStringError(inconvertibleErrorCode(), "'nvlink' failed");
+
+ return static_cast<std::string>(TempFile);
+}
+} // namespace nvptx
+
+Expected<std::string> linkDevice(ArrayRef<StringRef> InputFiles,
+ ArrayRef<std::string> LinkerArgs,
+ Triple TheTriple, StringRef Arch) {
+ switch (TheTriple.getArch()) {
+ case Triple::nvptx:
+ case Triple::nvptx64:
+ return nvptx::link(InputFiles, LinkerArgs, TheTriple, Arch);
+ case Triple::amdgcn:
+ // TODO: AMDGCN linking support.
+ case Triple::x86:
+ case Triple::x86_64:
+ // TODO: x86 linking support.
+ default:
+ return createStringError(inconvertibleErrorCode(),
+ TheTriple.getArchName() +
+ " linking is not supported");
+ }
+}
+
+/// Runs the appropriate linking action on all the device files specified in \p
+/// DeviceFiles. The linked device images are returned in \p LinkedImages.
+Error linkDeviceFiles(ArrayRef<DeviceFile> DeviceFiles,
+ ArrayRef<std::string> LinkerArgs,
+ SmallVectorImpl<std::string> &LinkedImages) {
+ // Get the list of inputs for a specific device.
+ StringMap<SmallVector<StringRef, 4>> LinkerInputMap;
+ for (auto &File : DeviceFiles)
+ LinkerInputMap[StringRef(File)].push_back(File.Filename);
+
+ // Try to link each device toolchain.
+ for (auto &LinkerInput : LinkerInputMap) {
+ auto TargetFeatures = LinkerInput.getKey().rsplit('-');
+ Triple TheTriple(TargetFeatures.first);
+ StringRef Arch(TargetFeatures.second);
+
+ // TODO: Run LTO or bitcode linking before the final link job.
+
+ auto ImageOrErr =
+ linkDevice(LinkerInput.getValue(), LinkerArgs, TheTriple, Arch);
+ if (!ImageOrErr)
+ return ImageOrErr.takeError();
+
+ LinkedImages.push_back(*ImageOrErr);
+ }
+ return Error::success();
+}
+
+/// Creates an object file containing the device image stored in the filename \p
+/// ImageFile that can be linked with the host.
+Expected<std::string> wrapDeviceImage(StringRef ImageFile) {
+ // TODO: Call these utilities as a library intead of executing them here.
+ ErrorOr<std::string> WrapperPath =
+ sys::findProgramByName("clang-offload-wrapper");
+ if (!WrapperPath)
+ return createStringError(WrapperPath.getError(),
+ "Unable to find 'clang-offload-wrapper' in path");
+
+ // Create a new file to write the wrapped bitcode file to.
+ SmallString<128> BitcodeFile;
+ if (std::error_code EC =
+ sys::fs::createTemporaryFile("offload", "bc", BitcodeFile))
+ return createFileError(BitcodeFile, EC);
+ TempFiles.push_back(static_cast<std::string>(BitcodeFile));
+
+ // TODO: Optionally pass the host triple in somewhere.
+ Triple HostTriple(sys::getDefaultTargetTriple());
+ SmallVector<StringRef, 4> WrapperArgs;
+ WrapperArgs.push_back(*WrapperPath);
+ WrapperArgs.push_back("-target");
+ WrapperArgs.push_back(HostTriple.getTriple());
+ WrapperArgs.push_back("-o");
+ WrapperArgs.push_back(BitcodeFile);
+ WrapperArgs.push_back(ImageFile);
+
+ if (sys::ExecuteAndWait(*WrapperPath, WrapperArgs))
+ return createStringError(inconvertibleErrorCode(),
+ "'clang-offload-wrapper' failed");
+
+ ErrorOr<std::string> CompilerPath = sys::findProgramByName("llc");
+ if (!WrapperPath)
+ return createStringError(WrapperPath.getError(),
+ "Unable to find 'llc' in path");
- return None;
+ // Create a new file to write the wrapped bitcode file to.
+ SmallString<128> ObjectFile;
+ if (std::error_code EC =
+ sys::fs::createTemporaryFile("offload", "o", ObjectFile))
+ return createFileError(BitcodeFile, EC);
+ TempFiles.push_back(static_cast<std::string>(ObjectFile));
+
+ SmallVector<StringRef, 4> CompilerArgs;
+ CompilerArgs.push_back(*CompilerPath);
+ CompilerArgs.push_back("--filetype=obj");
+ CompilerArgs.push_back("--relocation-model=pic");
+ CompilerArgs.push_back("-o");
+ CompilerArgs.push_back(ObjectFile);
+ CompilerArgs.push_back(BitcodeFile);
+
+ if (sys::ExecuteAndWait(*CompilerPath, CompilerArgs))
+ return createStringError(inconvertibleErrorCode(), "'llc' failed");
+
+ return static_cast<std::string>(ObjectFile);
}
} // namespace
@@ -389,6 +556,7 @@ extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
int main(int argc, const char **argv) {
InitLLVM X(argc, argv);
+ LinkerExecutable = argv[0];
sys::PrintStackTraceOnErrorSignal(argv[0]);
cl::SetVersionPrinter(PrintVersion);
cl::HideUnrelatedOptions(ClangLinkerWrapperCategory);
@@ -403,59 +571,61 @@ int main(int argc, const char **argv) {
cl::PrintHelpMessage();
return EXIT_SUCCESS;
}
- LinkerExecutable = argv[0];
-
- SmallVector<std::string, 4> TempFiles;
- SmallVector<DeviceFile, 4> DeviceFiles;
auto reportError = [argv](Error E) {
logAllUnhandledErrors(std::move(E), WithColor::error(errs(), argv[0]));
- exit(EXIT_FAILURE);
+ return EXIT_FAILURE;
};
+ SmallVector<std::string, 16> LinkerArgs;
+ for (const std::string &Arg : HostLinkerArgs)
+ LinkerArgs.push_back(Arg);
+
// Try to extract device code from the linker input and replace the linker
// input with a new file that has the device section stripped.
+ SmallVector<DeviceFile, 4> DeviceFiles;
for (std::string &Arg : LinkerArgs) {
if (sys::path::extension(Arg) == ".o" ||
sys::path::extension(Arg) == ".a") {
ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
MemoryBuffer::getFileOrSTDIN(Arg);
if (std::error_code EC = BufferOrErr.getError())
- reportError(createFileError(Arg, EC));
+ return reportError(createFileError(Arg, EC));
auto NewFileOrErr =
extractFromBuffer(std::move(*BufferOrErr), DeviceFiles);
if (!NewFileOrErr)
- reportError(NewFileOrErr.takeError());
+ return reportError(NewFileOrErr.takeError());
- if (NewFileOrErr->hasValue()) {
- TempFiles.push_back(**NewFileOrErr);
+ if (NewFileOrErr->hasValue())
Arg = **NewFileOrErr;
- }
}
}
- // Add the newly extracted device files to the temporary list.
- for (const auto &DeviceFile : DeviceFiles)
- TempFiles.push_back(DeviceFile.Filename);
+ // Link the device images extracted from the linker input.
+ SmallVector<std::string, 16> LinkedImages;
+ if (Error Err = linkDeviceFiles(DeviceFiles, LinkerArgs, LinkedImages))
+ return reportError(std::move(Err));
- // TODO: Perform appropriate device linking action.
- // TODO: Wrap device image in a host binary and pass it to the linker.
- WithColor::warning(errs(), argv[0]) << "Offload linking not yet supported.\n";
+ // Wrap each linked device image into a linkable host binary and add it to the
+ // link job's inputs.
+ for (const auto &Image : LinkedImages) {
+ auto FileOrErr = wrapDeviceImage(Image);
+ if (!FileOrErr)
+ return reportError(FileOrErr.takeError());
- SmallVector<std::string, 16> LinkerArgv;
- for (const std::string &Arg : LinkerArgs)
- LinkerArgv.push_back(Arg);
+ LinkerArgs.push_back(*FileOrErr);
+ }
// Run the host linking job.
- if (Error Err = runLinker(LinkerUserPath, LinkerArgv))
- reportError(std::move(Err));
+ if (Error Err = runLinker(LinkerUserPath, LinkerArgs))
+ return reportError(std::move(Err));
- for (const auto &TempFile : TempFiles) {
+ // Remove the temporary files created.
+ for (const auto &TempFile : TempFiles)
if (std::error_code EC = sys::fs::remove(TempFile))
reportError(createFileError(TempFile, EC));
- }
return EXIT_SUCCESS;
}
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