https://github.com/jhuber6 updated
https://github.com/llvm/llvm-project/pull/96561
>From 6c70e542bbb355160b833ede6f86be0366953b88 Mon Sep 17 00:00:00 2001
From: Joseph Huber <hube...@outlook.com>
Date: Mon, 24 Jun 2024 15:14:52 -0500
Subject: [PATCH] [Clang] Introduce 'clang-nvlink-wrappaer' to work around
'nvlink'
Summary:
The `clang-nvlink-wrapper` is a utility that I removed awhile back
during the transition to the new driver. This patch adds back in a new,
upgraded version that does LTO + archive linking. It's not an easy
choice to reintroduce something I happily deleted, but this is the only
way to move forward with improving GPU support in LLVM.
While NVIDIA provides a linker called 'nvlink', its main interface is
very difficult to work with. It does not provide LTO, or static linking,
requires all files to be named a non-standard `.cubin`, and rejects link
jobs that other linkers would be fine with (i.e empty). I have spent a
great deal of time hacking around this in the GPU `libc` implementation,
where I deliberately avoid LTO and static linking and have about 100
lines of hacky CMake dedicated to storing these files in a format that
the clang-linker-wrapper accepts to avoid this limitation.
The main reason I want to re-intorudce this tool is because I am
planning on creating a more standard C/C++ toolchain for GPUs to use.
This will install files like the following.
```
<install>/lib/nvptx64-nvidia-cuda/libc.a
<install>/lib/nvptx64-nvidia-cuda/libc++.a
<install>/lib/nvptx64-nvidia-cuda/libomp.a
<install>/lib/clang/19/lib/nvptx64-nvidia-cuda/libclang_rt.builtins.a
```
Linking in these libraries will then simply require passing `-lc` like
is already done for non-GPU toolchains. However, this doesn't work with
the currently deficient `nvlink` linker, so I consider this a blocking
issue to massively improving the state of building GPU libraries.
In the future we may be able to convince NVIDIA to port their linker to
`ld.lld`, but for now this is the only workable solution that allows us
to hack around the weird behavior of their closed-source software.
---
clang/lib/Driver/ToolChains/Cuda.cpp | 61 +-
clang/lib/Driver/ToolChains/Cuda.h | 3 +
clang/test/Driver/cuda-cross-compiling.c | 8 +-
clang/test/Driver/nvlink-wrapper.c | 65 ++
clang/test/lit.cfg.py | 1 +
clang/tools/CMakeLists.txt | 1 +
.../tools/clang-nvlink-wrapper/CMakeLists.txt | 44 ++
.../ClangNVLinkWrapper.cpp | 671 ++++++++++++++++++
.../tools/clang-nvlink-wrapper/NVLinkOpts.td | 68 ++
9 files changed, 865 insertions(+), 57 deletions(-)
create mode 100644 clang/test/Driver/nvlink-wrapper.c
create mode 100644 clang/tools/clang-nvlink-wrapper/CMakeLists.txt
create mode 100644 clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
create mode 100644 clang/tools/clang-nvlink-wrapper/NVLinkOpts.td
diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp
b/clang/lib/Driver/ToolChains/Cuda.cpp
index 2dfc7457b0ac7..54724cc1ad08e 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -461,13 +461,6 @@ void NVPTX::Assembler::ConstructJob(Compilation &C, const
JobAction &JA,
CmdArgs.push_back("--output-file");
std::string OutputFileName = TC.getInputFilename(Output);
- // If we are invoking `nvlink` internally we need to output a `.cubin` file.
- // FIXME: This should hopefully be removed if NVIDIA updates their tooling.
- if (!C.getInputArgs().getLastArg(options::OPT_c)) {
- SmallString<256> Filename(Output.getFilename());
- llvm::sys::path::replace_extension(Filename, "cubin");
- OutputFileName = Filename.str();
- }
if (Output.isFilename() && OutputFileName != Output.getFilename())
C.addTempFile(Args.MakeArgString(OutputFileName));
@@ -618,6 +611,11 @@ void NVPTX::Linker::ConstructJob(Compilation &C, const
JobAction &JA,
// Add standard library search paths passed on the command line.
Args.AddAllArgs(CmdArgs, options::OPT_L);
getToolChain().AddFilePathLibArgs(Args, CmdArgs);
+ AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
+
+ if (C.getDriver().isUsingLTO())
+ addLTOOptions(getToolChain(), Args, CmdArgs, Output, Inputs[0],
+ C.getDriver().getLTOMode() == LTOK_Thin);
// Add paths for the default clang library path.
SmallString<256> DefaultLibPath =
@@ -625,51 +623,12 @@ void NVPTX::Linker::ConstructJob(Compilation &C, const
JobAction &JA,
llvm::sys::path::append(DefaultLibPath, CLANG_INSTALL_LIBDIR_BASENAME);
CmdArgs.push_back(Args.MakeArgString(Twine("-L") + DefaultLibPath));
- for (const auto &II : Inputs) {
- if (II.getType() == types::TY_LLVM_IR || II.getType() == types::TY_LTO_IR
||
- II.getType() == types::TY_LTO_BC || II.getType() == types::TY_LLVM_BC)
{
- C.getDriver().Diag(diag::err_drv_no_linker_llvm_support)
- << getToolChain().getTripleString();
- continue;
- }
-
- // The 'nvlink' application performs RDC-mode linking when given a '.o'
- // file and device linking when given a '.cubin' file. We always want to
- // perform device linking, so just rename any '.o' files.
- // FIXME: This should hopefully be removed if NVIDIA updates their tooling.
- if (II.isFilename()) {
- auto InputFile = getToolChain().getInputFilename(II);
- if (llvm::sys::path::extension(InputFile) != ".cubin") {
- // If there are no actions above this one then this is direct input and
- // we can copy it. Otherwise the input is internal so a `.cubin` file
- // should exist.
- if (II.getAction() && II.getAction()->getInputs().size() == 0) {
- const char *CubinF =
- Args.MakeArgString(getToolChain().getDriver().GetTemporaryPath(
- llvm::sys::path::stem(InputFile), "cubin"));
- if (llvm::sys::fs::copy_file(InputFile, C.addTempFile(CubinF)))
- continue;
-
- CmdArgs.push_back(CubinF);
- } else {
- SmallString<256> Filename(InputFile);
- llvm::sys::path::replace_extension(Filename, "cubin");
- CmdArgs.push_back(Args.MakeArgString(Filename));
- }
- } else {
- CmdArgs.push_back(Args.MakeArgString(InputFile));
- }
- } else if (!II.isNothing()) {
- II.getInputArg().renderAsInput(Args, CmdArgs);
- }
- }
-
C.addCommand(std::make_unique<Command>(
JA, *this,
ResponseFileSupport{ResponseFileSupport::RF_Full, llvm::sys::WEM_UTF8,
"--options-file"},
- Args.MakeArgString(getToolChain().GetProgramPath("nvlink")), CmdArgs,
- Inputs, Output));
+
Args.MakeArgString(getToolChain().GetProgramPath("clang-nvlink-wrapper")),
+ CmdArgs, Inputs, Output));
}
void NVPTX::getNVPTXTargetFeatures(const Driver &D, const llvm::Triple &Triple,
@@ -949,11 +908,7 @@ std::string CudaToolChain::getInputFilename(const
InputInfo &Input) const {
if (Input.getType() != types::TY_Object || getDriver().offloadDeviceOnly())
return ToolChain::getInputFilename(Input);
- // Replace extension for object files with cubin because nvlink relies on
- // these particular file names.
- SmallString<256> Filename(ToolChain::getInputFilename(Input));
- llvm::sys::path::replace_extension(Filename, "cubin");
- return std::string(Filename);
+ return ToolChain::getInputFilename(Input);
}
llvm::opt::DerivedArgList *
diff --git a/clang/lib/Driver/ToolChains/Cuda.h
b/clang/lib/Driver/ToolChains/Cuda.h
index 43c17ba7c0ba0..0735c36f116bc 100644
--- a/clang/lib/Driver/ToolChains/Cuda.h
+++ b/clang/lib/Driver/ToolChains/Cuda.h
@@ -155,6 +155,7 @@ class LLVM_LIBRARY_VISIBILITY NVPTXToolChain : public
ToolChain {
bool isPIEDefault(const llvm::opt::ArgList &Args) const override {
return false;
}
+ bool HasNativeLLVMSupport() const override { return true; }
bool isPICDefaultForced() const override { return false; }
bool SupportsProfiling() const override { return false; }
@@ -192,6 +193,8 @@ class LLVM_LIBRARY_VISIBILITY CudaToolChain : public
NVPTXToolChain {
return &HostTC.getTriple();
}
+ bool HasNativeLLVMSupport() const override { return false; }
+
std::string getInputFilename(const InputInfo &Input) const override;
llvm::opt::DerivedArgList *
diff --git a/clang/test/Driver/cuda-cross-compiling.c
b/clang/test/Driver/cuda-cross-compiling.c
index 1dc4520f485db..9a1a68f2aad5d 100644
--- a/clang/test/Driver/cuda-cross-compiling.c
+++ b/clang/test/Driver/cuda-cross-compiling.c
@@ -32,8 +32,8 @@
// RUN: | FileCheck -check-prefix=ARGS %s
// ARGS: -cc1" "-triple" "nvptx64-nvidia-cuda" "-S" {{.*}} "-target-cpu"
"sm_61" "-target-feature" "+ptx{{[0-9]+}}" {{.*}} "-o" "[[PTX:.+]].s"
-// ARGS-NEXT: ptxas{{.*}}"-m64" "-O0" "--gpu-name" "sm_61" "--output-file"
"[[CUBIN:.+]].cubin" "[[PTX]].s" "-c"
-// ARGS-NEXT: nvlink{{.*}}"-o" "a.out" "-arch" "sm_61" {{.*}} "[[CUBIN]].cubin"
+// ARGS-NEXT: ptxas{{.*}}"-m64" "-O0" "--gpu-name" "sm_61" "--output-file"
"[[CUBIN:.+]].o" "[[PTX]].s" "-c"
+// ARGS-NEXT: clang-nvlink-wrapper{{.*}}"-o" "a.out" "-arch"
"sm_61"{{.*}}"[[CUBIN]].o"
//
// Test the generated arguments to the CUDA binary utils when targeting NVPTX.
@@ -55,7 +55,7 @@
// RUN: %clang -target nvptx64-nvidia-cuda -march=sm_61 -### %t.o 2>&1 \
// RUN: | FileCheck -check-prefix=LINK %s
-// LINK: nvlink{{.*}}"-o" "a.out" "-arch" "sm_61" {{.*}} "{{.*}}.cubin"
+// LINK: clang-nvlink-wrapper{{.*}}"-o" "a.out" "-arch" "sm_61" {{.*}}
"{{.*}}.o"
//
// Test to ensure that we enable handling global constructors in a freestanding
@@ -72,7 +72,7 @@
// RUN: %clang -target nvptx64-nvidia-cuda -Wl,-v -Wl,a,b -march=sm_52 -### %s
2>&1 \
// RUN: | FileCheck -check-prefix=LINKER-ARGS %s
-// LINKER-ARGS: nvlink{{.*}}"-v"{{.*}}"a" "b"
+// LINKER-ARGS: clang-nvlink-wrapper{{.*}}"-v"{{.*}}"a" "b"
// Tests for handling a missing architecture.
//
diff --git a/clang/test/Driver/nvlink-wrapper.c
b/clang/test/Driver/nvlink-wrapper.c
new file mode 100644
index 0000000000000..fdda93f1f9cdc
--- /dev/null
+++ b/clang/test/Driver/nvlink-wrapper.c
@@ -0,0 +1,65 @@
+// REQUIRES: x86-registered-target
+// REQUIRES: nvptx-registered-target
+
+#if defined(X)
+extern int y;
+int foo() { return y; }
+
+int x = 0;
+#elif defined(Y)
+int y = 42;
+#elif defined(Z)
+int z = 42;
+#elif defined(W)
+int w = 42;
+#elif defined(U)
+extern int x;
+extern int __attribute__((weak)) w;
+
+int bar() {
+ return x + w;
+}
+#else
+extern int y;
+int __attribute__((visibility("hidden"))) x = 999;
+int baz() { return y + x; }
+#endif
+
+// Create various inputs to test basic linking and LTO capabilities. Creating a
+// CUDA binary requires access to the `ptxas` executable, so we just use x64.
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DX -o %t-x.o
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DY -o %t-y.o
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DZ -o %t-z.o
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DW -o %t-w.o
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DU -o %t-u.o
+// RUN: llvm-ar rcs %t-x.a %t-x.o
+// RUN: llvm-ar rcs %t-y.a %t-y.o
+// RUN: llvm-ar rcs %t-z.a %t-z.o
+// RUN: llvm-ar rcs %t-w.a %t-w.o
+
+//
+// Check that we forward any unrecognized argument to 'nvlink'.
+//
+// RUN: clang-nvlink-wrapper --dry-run -arch sm_52 %t-u.o -foo -o a.out 2>&1 \
+// RUN: | FileCheck %s --check-prefix=ARGS
+// ARGS: nvlink{{.*}} -arch sm_52 -foo -o a.out [[INPUT:.+]].cubin
+
+//
+// Check the symbol resolution for static archives. We expect to only link
+// `libx.a` and `liby.a` because extern weak symbols do not extract and
`libz.a`
+// is not used at all.
+//
+// RUN: clang-nvlink-wrapper --dry-run %t-x.a %t-u.o %t-y.a %t-z.a %t-w.a \
+// RUN: -arch sm_52 -o a.out 2>&1 | FileCheck %s --check-prefix=LINK
+// LINK: nvlink{{.*}} -arch sm_52 -o a.out [[INPUT:.+]].cubin
{{.*}}-x-{{.*}}.cubin{{.*}}-y-{{.*}}.cubin
+
+// RUN: %clang -cc1 %s -triple nvptx64-nvidia-cuda -emit-llvm-bc -o %t.o
+
+//
+// Check that the LTO interface works and properly preserves symbols used in a
+// regular object file.
+//
+// RUN: clang-nvlink-wrapper --dry-run %t.o %t-u.o %t-y.a \
+// RUN: -arch sm_52 -o a.out 2>&1 | FileCheck %s --check-prefix=LTO
+// LTO: ptxas{{.*}} -m64 -c [[PTX:.+]].s -O3 -arch sm_52 -o [[CUBIN:.+]].cubin
+// LTO: nvlink{{.*}} -arch sm_52 -o a.out [[CUBIN]].cubin
{{.*}}-u-{{.*}}.cubin {{.*}}-y-{{.*}}.cubin
diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
index e5630a07424c7..92a3361ce672e 100644
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -95,6 +95,7 @@
"llvm-ifs",
"yaml2obj",
"clang-linker-wrapper",
+ "clang-nvlink-wrapper",
"llvm-lto",
"llvm-lto2",
"llvm-profdata",
diff --git a/clang/tools/CMakeLists.txt b/clang/tools/CMakeLists.txt
index bdd8004be3e02..4885afc1584d0 100644
--- a/clang/tools/CMakeLists.txt
+++ b/clang/tools/CMakeLists.txt
@@ -9,6 +9,7 @@ add_clang_subdirectory(clang-format-vs)
add_clang_subdirectory(clang-fuzzer)
add_clang_subdirectory(clang-import-test)
add_clang_subdirectory(clang-linker-wrapper)
+add_clang_subdirectory(clang-nvlink-wrapper)
add_clang_subdirectory(clang-offload-packager)
add_clang_subdirectory(clang-offload-bundler)
add_clang_subdirectory(clang-scan-deps)
diff --git a/clang/tools/clang-nvlink-wrapper/CMakeLists.txt
b/clang/tools/clang-nvlink-wrapper/CMakeLists.txt
new file mode 100644
index 0000000000000..d46f66994cf39
--- /dev/null
+++ b/clang/tools/clang-nvlink-wrapper/CMakeLists.txt
@@ -0,0 +1,44 @@
+set(LLVM_LINK_COMPONENTS
+ ${LLVM_TARGETS_TO_BUILD}
+ BitWriter
+ Core
+ BinaryFormat
+ MC
+ Target
+ TransformUtils
+ Analysis
+ Passes
+ IRReader
+ Object
+ Option
+ Support
+ TargetParser
+ CodeGen
+ LTO
+ )
+
+set(LLVM_TARGET_DEFINITIONS NVLinkOpts.td)
+tablegen(LLVM NVLinkOpts.inc -gen-opt-parser-defs)
+add_public_tablegen_target(NVLinkWrapperOpts)
+
+if(NOT CLANG_BUILT_STANDALONE)
+ set(tablegen_deps intrinsics_gen NVLinkWrapperOpts)
+endif()
+
+add_clang_tool(clang-nvlink-wrapper
+ ClangNVLinkWrapper.cpp
+
+ DEPENDS
+ ${tablegen_deps}
+ )
+
+set(CLANG_NVLINK_WRAPPER_LIB_DEPS
+ clangBasic
+ )
+
+target_compile_options(clang-nvlink-wrapper PRIVATE "-g" "-O0")
+
+target_link_libraries(clang-nvlink-wrapper
+ PRIVATE
+ ${CLANG_NVLINK_WRAPPER_LIB_DEPS}
+ )
diff --git a/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
b/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
new file mode 100644
index 0000000000000..e94d2a9016954
--- /dev/null
+++ b/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
@@ -0,0 +1,671 @@
+//===-- clang-nvlink-wrapper/ClangNVLinkWrapper.cpp - NVIDIA linker util
--===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+//
+// This tool wraps around the NVIDIA linker called 'nvlink'. The NVIDIA linker
+// is required to create NVPTX applications, but does not support common
+// features like LTO or archives. This utility wraps around the tool to cover
+// its deficiencies. This tool can be removed once NVIDIA improves their linker
+// or ports it to `ld.lld`.
+//
+//===---------------------------------------------------------------------===//
+
+#include "clang/Basic/Version.h"
+
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/CodeGen/CommandFlags.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/LTO/LTO.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Object/ArchiveWriter.h"
+#include "llvm/Object/Binary.h"
+#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Object/IRObjectFile.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/OffloadBinary.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Option/OptTable.h"
+#include "llvm/Option/Option.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Program.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/StringSaver.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/WithColor.h"
+
+using namespace llvm;
+using namespace llvm::opt;
+using namespace llvm::object;
+
+static void printVersion(raw_ostream &OS) {
+ OS << clang::getClangToolFullVersion("clang-nvlink-wrapper") << '\n';
+}
+
+/// The value of `argv[0]` when run.
+static const char *Executable;
+
+/// Temporary files to be cleaned up.
+static SmallVector<SmallString<128>> TempFiles;
+
+/// Codegen flags for LTO backend.
+static codegen::RegisterCodeGenFlags CodeGenFlags;
+
+namespace {
+/// Must not overlap with llvm::opt::DriverFlag.
+enum WrapperFlags {
+ WrapperOnlyOption = (1 << 4), // Options only used by the linker wrapper.
+ DeviceOnlyOption = (1 << 5), // Options only used for device linking.
+};
+
+enum ID {
+ OPT_INVALID = 0, // This is not an option ID.
+#define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
+#include "NVLinkOpts.inc"
+ LastOption
+#undef OPTION
+};
+
+#define PREFIX(NAME, VALUE)
\
+ static constexpr StringLiteral NAME##_init[] = VALUE;
\
+ static constexpr ArrayRef<StringLiteral> NAME(NAME##_init,
\
+ std::size(NAME##_init) - 1);
+#include "NVLinkOpts.inc"
+#undef PREFIX
+
+static constexpr OptTable::Info InfoTable[] = {
+#define OPTION(...) LLVM_CONSTRUCT_OPT_INFO(__VA_ARGS__),
+#include "NVLinkOpts.inc"
+#undef OPTION
+};
+
+class WrapperOptTable : public opt::GenericOptTable {
+public:
+ WrapperOptTable() : opt::GenericOptTable(InfoTable) {}
+};
+
+const OptTable &getOptTable() {
+ static const WrapperOptTable *Table = []() {
+ auto Result = std::make_unique<WrapperOptTable>();
+ return Result.release();
+ }();
+ return *Table;
+}
+
+[[noreturn]] void reportError(Error E) {
+ outs().flush();
+ logAllUnhandledErrors(std::move(E), WithColor::error(errs(), Executable));
+ exit(EXIT_FAILURE);
+}
+
+void diagnosticHandler(const DiagnosticInfo &DI) {
+ std::string ErrStorage;
+ raw_string_ostream OS(ErrStorage);
+ DiagnosticPrinterRawOStream DP(OS);
+ DI.print(DP);
+
+ switch (DI.getSeverity()) {
+ case DS_Error:
+ WithColor::error(errs(), Executable) << ErrStorage << "\n";
+ break;
+ case DS_Warning:
+ WithColor::warning(errs(), Executable) << ErrStorage << "\n";
+ break;
+ case DS_Note:
+ WithColor::note(errs(), Executable) << ErrStorage << "\n";
+ break;
+ case DS_Remark:
+ WithColor::remark(errs()) << ErrStorage << "\n";
+ break;
+ }
+}
+
+Expected<StringRef> createTempFile(const ArgList &Args, const Twine &Prefix,
+ StringRef Extension) {
+ SmallString<128> OutputFile;
+ if (Args.hasArg(OPT_save_temps)) {
+ (Prefix + "." + Extension).toNullTerminatedStringRef(OutputFile);
+ } else {
+ if (std::error_code EC =
+ sys::fs::createTemporaryFile(Prefix, Extension, OutputFile))
+ return createFileError(OutputFile, EC);
+ }
+
+ TempFiles.emplace_back(std::move(OutputFile));
+ return TempFiles.back();
+}
+
+Expected<std::string> findProgram(StringRef Name, ArrayRef<StringRef> Paths) {
+ ErrorOr<std::string> Path = sys::findProgramByName(Name, Paths);
+ if (!Path)
+ Path = sys::findProgramByName(Name);
+ if (!Path)
+ return createStringError(Path.getError(),
+ "Unable to find '" + Name + "' in path");
+ return *Path;
+}
+
+std::optional<std::string> findFile(StringRef Dir, StringRef Root,
+ const Twine &Name) {
+ SmallString<128> Path;
+ if (Dir.starts_with("="))
+ sys::path::append(Path, Root, Dir.substr(1), Name);
+ else
+ sys::path::append(Path, Dir, Name);
+
+ if (sys::fs::exists(Path))
+ return static_cast<std::string>(Path);
+ return std::nullopt;
+}
+
+std::optional<std::string>
+findFromSearchPaths(StringRef Name, StringRef Root,
+ ArrayRef<StringRef> SearchPaths) {
+ for (StringRef Dir : SearchPaths)
+ if (std::optional<std::string> File = findFile(Dir, Root, Name))
+ return File;
+ return std::nullopt;
+}
+
+std::optional<std::string>
+searchLibraryBaseName(StringRef Name, StringRef Root,
+ ArrayRef<StringRef> SearchPaths) {
+ for (StringRef Dir : SearchPaths)
+ if (std::optional<std::string> File =
+ findFile(Dir, Root, "lib" + Name + ".a"))
+ return File;
+ return std::nullopt;
+}
+
+/// Search for static libraries in the linker's library path given input like
+/// `-lfoo` or `-l:libfoo.a`.
+std::optional<std::string> searchLibrary(StringRef Input, StringRef Root,
+ ArrayRef<StringRef> SearchPaths) {
+ if (Input.starts_with(":") || Input.ends_with(".lib"))
+ return findFromSearchPaths(Input.drop_front(), Root, SearchPaths);
+ return searchLibraryBaseName(Input, Root, SearchPaths);
+}
+
+void printCommands(ArrayRef<StringRef> CmdArgs) {
+ if (CmdArgs.empty())
+ return;
+
+ llvm::errs() << " \"" << CmdArgs.front() << "\" ";
+ for (auto IC = std::next(CmdArgs.begin()), IE = CmdArgs.end(); IC != IE;
++IC)
+ llvm::errs() << *IC << (std::next(IC) != IE ? " " : "\n");
+}
+
+/// A minimum symbol interface that provides the necessary information to
+/// extract archive members and resolve LTO symbols.
+struct Symbol {
+ enum Flags {
+ None = 0,
+ Undefined = 1 << 0,
+ Weak = 1 << 1,
+ };
+
+ Symbol()
+ : File(), Flags(Undefined), Name(), UsedInRegularObj(false), Lazy(false)
{
+ }
+
+ Symbol(MemoryBufferRef File, const irsymtab::Reader::SymbolRef Sym, bool
Lazy)
+ : File(File), Flags(0), UsedInRegularObj(false), Lazy(Lazy) {
+ if (Sym.isUndefined())
+ Flags |= Undefined;
+ if (Sym.isWeak())
+ Flags |= Weak;
+ Name = Sym.getName();
+ }
+
+ Symbol(MemoryBufferRef File, const SymbolRef Sym, bool Lazy)
+ : File(File), Flags(0), UsedInRegularObj(false), Lazy(Lazy) {
+ auto FlagsOrErr = Sym.getFlags();
+ if (!FlagsOrErr)
+ reportError(FlagsOrErr.takeError());
+ if (*FlagsOrErr & SymbolRef::SF_Undefined)
+ Flags |= Undefined;
+ if (*FlagsOrErr & SymbolRef::SF_Weak)
+ Flags |= Weak;
+
+ auto NameOrErr = Sym.getName();
+ if (!NameOrErr)
+ reportError(NameOrErr.takeError());
+ Name = *NameOrErr;
+ }
+
+ Symbol Resolve(Symbol Other) {
+ if (File.getBuffer().empty())
+ return Other.Lazy ? *this : Other;
+ if (Other.isUndefined())
+ return *this;
+ if (isWeak() && isUndefined() && Other.Lazy)
+ return *this;
+ if (isWeak() && !Other.isWeak())
+ return Other;
+ if (isUndefined() && !Other.isUndefined())
+ return Other;
+ return *this;
+ }
+
+ bool isWeak() const { return Flags & Weak; }
+ bool isUndefined() const { return Flags & Undefined; }
+
+ MemoryBufferRef File;
+ uint32_t Flags;
+ StringRef Name;
+ bool UsedInRegularObj;
+ bool Lazy;
+};
+
+Expected<StringRef> runPTXAs(StringRef File, const ArgList &Args) {
+ std::string CudaPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
+ Expected<std::string> PTXAsPath = findProgram("ptxas", {CudaPath + "/bin"});
+ if (!PTXAsPath)
+ return PTXAsPath.takeError();
+
+ auto TempFileOrErr = createTempFile(
+ Args, sys::path::stem(Args.getLastArgValue(OPT_o, "a.out")), "cubin");
+ if (!TempFileOrErr)
+ return TempFileOrErr.takeError();
+
+ SmallVector<StringRef> AssemblerArgs({*PTXAsPath, "-m64", "-c", File});
+ if (Args.hasArg(OPT_g))
+ AssemblerArgs.push_back("-O0");
+ else
+ AssemblerArgs.push_back(
+ Args.MakeArgString("-O" + Args.getLastArgValue(OPT_O, "3")));
+ AssemblerArgs.append({"-arch", Args.getLastArgValue(OPT_arch)});
+ AssemblerArgs.append({"-o", *TempFileOrErr});
+
+ if (Args.hasArg(OPT_dry_run))
+ printCommands(AssemblerArgs);
+ else if (sys::ExecuteAndWait(*PTXAsPath, AssemblerArgs))
+ return createStringError("'" + sys::path::filename(*PTXAsPath) + "'" +
+ " failed");
+ return Args.MakeArgString(*TempFileOrErr);
+}
+
+Expected<std::unique_ptr<lto::LTO>> createLTO(const ArgList &Args) {
+ const llvm::Triple Triple("nvptx64-nvidia-cuda");
+ // We need to remove AMD's target-id from the processor if present.
+ lto::Config Conf;
+ lto::ThinBackend Backend;
+ Backend =
+
lto::createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());
+
+ Conf.CPU = Args.getLastArgValue(OPT_arch);
+ Conf.Options = codegen::InitTargetOptionsFromCodeGenFlags(Triple);
+
+ Conf.MAttrs = {Args.getLastArgValue(OPT_feature, "+ptx60").str()};
+ std::optional<CodeGenOptLevel> CGOptLevelOrNone =
+ CodeGenOpt::parseLevel(Args.getLastArgValue(OPT_O, "2")[0]);
+ assert(CGOptLevelOrNone && "Invalid optimization level");
+ Conf.CGOptLevel = *CGOptLevelOrNone;
+ Conf.OptLevel = Args.getLastArgValue(OPT_O, "2")[0] - '0';
+ Conf.DefaultTriple = Triple.getTriple();
+
+ Conf.DiagHandler = diagnosticHandler;
+ Conf.CGFileType = CodeGenFileType::AssemblyFile;
+
+ if (Args.hasArg(OPT_save_temps))
+ if (Error Err = Conf.addSaveTemps(
+ (Args.getLastArgValue(OPT_o, "a.out") + ".").str()))
+ return Err;
+
+ return std::make_unique<lto::LTO>(std::move(Conf), Backend);
+}
+
+Expected<SmallVector<StringRef>> getInput(const ArgList &Args) {
+ SmallVector<StringRef> LibraryPaths;
+ for (const opt::Arg *Arg : Args.filtered(OPT_library_path))
+ LibraryPaths.push_back(Arg->getValue());
+
+ bool WholeArchive = false;
+ SmallVector<std::pair<std::unique_ptr<MemoryBuffer>, bool>> InputFiles;
+ for (const opt::Arg *Arg : Args.filtered(
+ OPT_INPUT, OPT_library, OPT_whole_archive, OPT_no_whole_archive)) {
+ if (Arg->getOption().matches(OPT_whole_archive) ||
+ Arg->getOption().matches(OPT_no_whole_archive)) {
+ WholeArchive = Arg->getOption().matches(OPT_whole_archive);
+ continue;
+ }
+
+ std::optional<std::string> Filename =
+ Arg->getOption().matches(OPT_library)
+ ? searchLibrary(Arg->getValue(), /*Root=*/"", LibraryPaths)
+ : std::string(Arg->getValue());
+
+ if (!Filename && Arg->getOption().matches(OPT_library))
+ return createStringError("unable to find library -l%s", Arg->getValue());
+
+ if (!Filename || !sys::fs::exists(*Filename) ||
+ sys::fs::is_directory(*Filename))
+ continue;
+
+ ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
+ MemoryBuffer::getFileOrSTDIN(*Filename);
+ if (std::error_code EC = BufferOrErr.getError())
+ return createFileError(*Filename, EC);
+
+ MemoryBufferRef Buffer = **BufferOrErr;
+ switch (identify_magic(Buffer.getBuffer())) {
+ case file_magic::bitcode:
+ case file_magic::elf_relocatable:
+ InputFiles.emplace_back(std::move(*BufferOrErr), /*IsLazy=*/false);
+ break;
+ case file_magic::archive: {
+ Expected<std::unique_ptr<llvm::object::Archive>> LibFile =
+ object::Archive::create(Buffer);
+ if (!LibFile)
+ return LibFile.takeError();
+ Error Err = Error::success();
+ for (auto Child : (*LibFile)->children(Err)) {
+ auto ChildBufferOrErr = Child.getMemoryBufferRef();
+ if (!ChildBufferOrErr)
+ return ChildBufferOrErr.takeError();
+ std::unique_ptr<MemoryBuffer> ChildBuffer =
+ MemoryBuffer::getMemBufferCopy(
+ ChildBufferOrErr->getBuffer(),
+ ChildBufferOrErr->getBufferIdentifier());
+ InputFiles.emplace_back(std::move(ChildBuffer), !WholeArchive);
+ }
+ if (Err)
+ return Err;
+ break;
+ }
+ default:
+ return createStringError("Unsupported file type");
+ }
+ }
+
+ StringMap<Symbol> SymTab;
+ SmallVector<std::unique_ptr<MemoryBuffer>> LinkerInput;
+
+ bool Extracted = true;
+ while (Extracted) {
+ Extracted = false;
+ for (auto &[Buffer, IsLazy] : InputFiles) {
+ if (!Buffer)
+ continue;
+
+ Extracted = !IsLazy;
+ MemoryBufferRef File = *Buffer;
+ switch (identify_magic(File.getBuffer())) {
+ case file_magic::bitcode: {
+ Expected<IRSymtabFile> IRSymtabOrErr = readIRSymtab(File);
+ if (!IRSymtabOrErr)
+ return IRSymtabOrErr.takeError();
+ bool CheckSymbolsAgain;
+ do {
+ CheckSymbolsAgain = false;
+ for (unsigned I = 0; I != IRSymtabOrErr->Mods.size(); ++I) {
+ for (const auto &IRSym :
+ IRSymtabOrErr->TheReader.module_symbols(I)) {
+ if (IRSym.isFormatSpecific() || !IRSym.isGlobal())
+ continue;
+
+ Symbol &Sym = SymTab[IRSym.getName()];
+ Sym = Sym.Resolve(Symbol(File, IRSym, IsLazy));
+ if (Sym.File == File) {
+ Extracted = true;
+ if (IsLazy) {
+ IsLazy = false;
+ CheckSymbolsAgain = true;
+ }
+ }
+ }
+ }
+ } while (CheckSymbolsAgain);
+ break;
+ }
+ case file_magic::elf_relocatable: {
+ Expected<std::unique_ptr<ObjectFile>> ObjFile =
+ ObjectFile::createObjectFile(File);
+ if (!ObjFile)
+ return ObjFile.takeError();
+ bool CheckSymbolsAgaing;
+ do {
+ CheckSymbolsAgaing = false;
+ for (SymbolRef ObjSum : (*ObjFile)->symbols()) {
+ auto NameOrErr = ObjSum.getName();
+ if (!NameOrErr)
+ return NameOrErr.takeError();
+
+ Symbol &Sym = SymTab[*NameOrErr];
+ Sym = Sym.Resolve(Symbol(File, ObjSum, IsLazy));
+ Sym.UsedInRegularObj = true;
+ if (Sym.File == File) {
+ Extracted = true;
+ if (IsLazy) {
+ IsLazy = false;
+ CheckSymbolsAgaing = true;
+ }
+ }
+ }
+ } while (CheckSymbolsAgaing);
+ break;
+ }
+ default:
+ return createStringError("Unsupported file type");
+ }
+
+ // If we extracted any files we need to check all the symbols again.
+ if (Extracted) {
+ LinkerInput.emplace_back(std::move(Buffer));
+ break;
+ }
+ }
+ }
+
+ SmallVector<std::unique_ptr<MemoryBuffer>> BitcodeFiles;
+ for (auto &Input : LinkerInput)
+ if (identify_magic(Input->getBuffer()) == file_magic::bitcode)
+ BitcodeFiles.emplace_back(std::move(Input));
+
+ SmallVector<StringRef> Files;
+ if (!BitcodeFiles.empty()) {
+ auto LTOBackendOrErr = createLTO(Args);
+ if (!LTOBackendOrErr)
+ return LTOBackendOrErr.takeError();
+ lto::LTO <OBackend = **LTOBackendOrErr;
+ for (auto &BitcodeFile : BitcodeFiles) {
+ Expected<std::unique_ptr<lto::InputFile>> BitcodeFileOrErr =
+ llvm::lto::InputFile::create(*BitcodeFile);
+ if (!BitcodeFileOrErr)
+ return BitcodeFileOrErr.takeError();
+
+ const auto Symbols = (*BitcodeFileOrErr)->symbols();
+ SmallVector<lto::SymbolResolution, 16> Resolutions(Symbols.size());
+ size_t Idx = 0;
+ for (auto &Sym : Symbols) {
+ lto::SymbolResolution &Res = Resolutions[Idx++];
+ Symbol ObjSym = SymTab[Sym.getName()];
+
+ // We will use this as the prevailing symbol in LTO if it is not
+ // undefined and it is from the file that contained the canonical
+ // definition.
+ Res.Prevailing = !Sym.isUndefined() && ObjSym.File == *BitcodeFile;
+
+ // We need LTO to preseve the following global symbols:
+ // 1) Symbols used in regular objects.
+ // 2) Prevailing symbols that are needed visible to the gpu runtime.
+ Res.VisibleToRegularObj =
+ ObjSym.UsedInRegularObj ||
+ (Res.Prevailing &&
+ (Sym.getVisibility() != GlobalValue::HiddenVisibility &&
+ !Sym.canBeOmittedFromSymbolTable()));
+
+ // Identify symbols that must be exported dynamically and can be
+ // referenced by other files, (i.e. the runtime).
+ Res.ExportDynamic =
+ Sym.getVisibility() != GlobalValue::HiddenVisibility &&
+ !Sym.canBeOmittedFromSymbolTable();
+
+ // The final definition will reside in this linkage unit if the symbol
+ // is defined and local to the module. This only checks for bitcode
+ // files, full assertion will require complete symbol resolution.
+ Res.FinalDefinitionInLinkageUnit =
+ Sym.getVisibility() != GlobalValue::DefaultVisibility &&
+ (!Sym.isUndefined() && !Sym.isCommon());
+
+ // We do not support linker redefined symbols (e.g. --wrap) for device
+ // image linking, so the symbols will not be changed after LTO.
+ Res.LinkerRedefined = false;
+ }
+
+ // Add the bitcode file with its resolved symbols to the LTO job.
+ if (Error Err = LTOBackend.add(std::move(*BitcodeFileOrErr),
Resolutions))
+ return Err;
+ }
+
+ // Run the LTO job to compile the bitcode.
+ size_t MaxTasks = LTOBackend.getMaxTasks();
+ SmallVector<StringRef> LTOFiles(MaxTasks);
+ auto AddStream =
+ [&](size_t Task,
+ const Twine &ModuleName) -> std::unique_ptr<CachedFileStream> {
+ int FD = -1;
+ auto &TempFile = LTOFiles[Task];
+ auto TempFileOrErr = createTempFile(
+ Args, sys::path::stem(Args.getLastArgValue(OPT_o, "a.out")), "s");
+ if (!TempFileOrErr)
+ reportError(TempFileOrErr.takeError());
+ TempFile = Args.MakeArgString(*TempFileOrErr);
+ if (std::error_code EC = sys::fs::openFileForWrite(TempFile, FD))
+ reportError(errorCodeToError(EC));
+ return std::make_unique<CachedFileStream>(
+ std::make_unique<llvm::raw_fd_ostream>(FD, true));
+ };
+
+ if (Error Err = LTOBackend.run(AddStream))
+ return Err;
+
+ for (StringRef LTOFile : LTOFiles) {
+ auto FileOrErr = runPTXAs(LTOFile, Args);
+ if (!FileOrErr)
+ return FileOrErr.takeError();
+ Files.emplace_back(*FileOrErr);
+ }
+ }
+
+ for (auto &Input : LinkerInput) {
+ if (!Input)
+ continue;
+
+ auto TempFileOrErr = createTempFile(
+ Args, sys::path::stem(Input->getBufferIdentifier()), "cubin");
+ if (!TempFileOrErr)
+ return TempFileOrErr.takeError();
+ Expected<std::unique_ptr<FileOutputBuffer>> OutputOrErr =
+ FileOutputBuffer::create(*TempFileOrErr, Input->getBuffer().size());
+ if (!OutputOrErr)
+ return OutputOrErr.takeError();
+ std::unique_ptr<FileOutputBuffer> Output = std::move(*OutputOrErr);
+ llvm::copy(Input->getBuffer(), Output->getBufferStart());
+ if (Error E = Output->commit())
+ return E;
+ Files.emplace_back(Args.MakeArgString(*TempFileOrErr));
+ }
+
+ return Files;
+}
+
+Error runNVLink(ArrayRef<StringRef> Files, const ArgList &Args) {
+ std::string CudaPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
+ Expected<std::string> NVLinkPath = findProgram("nvlink", {CudaPath +
"/bin"});
+ if (!NVLinkPath)
+ return NVLinkPath.takeError();
+
+ ArgStringList NewLinkerArgs;
+ for (const opt::Arg *Arg : Args) {
+ // Do not forward arguments only intended for the linker wrapper.
+ if (Arg->getOption().hasFlag(WrapperOnlyOption))
+ continue;
+
+ // Do not forward any inputs that we have processed.
+ if (Arg->getOption().matches(OPT_INPUT) ||
+ Arg->getOption().matches(OPT_library))
+ continue;
+
+ Arg->render(Args, NewLinkerArgs);
+ }
+
+ llvm::transform(Files, std::back_inserter(NewLinkerArgs),
+ [&](StringRef Arg) { return Args.MakeArgString(Arg); });
+
+ SmallVector<StringRef> LinkerArgs({*NVLinkPath});
+ if (!Args.hasArg(OPT_o))
+ LinkerArgs.append({"-o", "a.out"});
+ for (StringRef Arg : NewLinkerArgs)
+ LinkerArgs.push_back(Arg);
+
+ if (Args.hasArg(OPT_dry_run))
+ printCommands(LinkerArgs);
+ else if (sys::ExecuteAndWait(*NVLinkPath, LinkerArgs))
+ return createStringError("'" + sys::path::filename(*NVLinkPath) + "'" +
+ " failed");
+ return Error::success();
+}
+
+} // namespace
+
+int main(int argc, char **argv) {
+ InitLLVM X(argc, argv);
+ InitializeAllTargetInfos();
+ InitializeAllTargets();
+ InitializeAllTargetMCs();
+ InitializeAllAsmParsers();
+ InitializeAllAsmPrinters();
+
+ Executable = argv[0];
+ sys::PrintStackTraceOnErrorSignal(argv[0]);
+
+ const OptTable &Tbl = getOptTable();
+ BumpPtrAllocator Alloc;
+ StringSaver Saver(Alloc);
+ auto Args = Tbl.parseArgs(argc, argv, OPT_INVALID, Saver, [&](StringRef Err)
{
+ reportError(createStringError(inconvertibleErrorCode(), Err));
+ });
+
+ if (Args.hasArg(OPT_help) || Args.hasArg(OPT_help_hidden)) {
+ Tbl.printHelp(
+ outs(), "clang-nvlink-wrapper [options] <options to passed to nvlink>",
+ "A utility that wraps around the NVIDIA 'nvlink' linker.\n"
+ "This enables static linking and LTO handling for NVPTX targets.\n",
+ Args.hasArg(OPT_help_hidden), Args.hasArg(OPT_help_hidden));
+ return EXIT_SUCCESS;
+ }
+
+ if (Args.hasArg(OPT_version))
+ printVersion(outs());
+
+ // This forwards '-mllvm' arguments to LLVM if present.
+ SmallVector<const char *> NewArgv = {argv[0]};
+ for (const opt::Arg *Arg : Args.filtered(OPT_mllvm))
+ NewArgv.push_back(Arg->getValue());
+ cl::ParseCommandLineOptions(NewArgv.size(), &NewArgv[0]);
+
+ auto FilesOrErr = getInput(Args);
+ if (!FilesOrErr)
+ reportError(FilesOrErr.takeError());
+
+ if (Error Err = runNVLink(*FilesOrErr, Args))
+ reportError(std::move(Err));
+
+ // Remove the temporary files created.
+ if (!Args.hasArg(OPT_save_temps))
+ for (const auto &TempFile : TempFiles)
+ if (std::error_code EC = sys::fs::remove(TempFile))
+ reportError(createFileError(TempFile, EC));
+
+ return EXIT_SUCCESS;
+}
diff --git a/clang/tools/clang-nvlink-wrapper/NVLinkOpts.td
b/clang/tools/clang-nvlink-wrapper/NVLinkOpts.td
new file mode 100644
index 0000000000000..55e93109ddadc
--- /dev/null
+++ b/clang/tools/clang-nvlink-wrapper/NVLinkOpts.td
@@ -0,0 +1,68 @@
+include "llvm/Option/OptParser.td"
+
+def WrapperOnlyOption : OptionFlag;
+
+def help : Flag<["-", "--"], "help">,
+ HelpText<"Display available options (--help-hidden for more)">;
+
+def help_hidden : Flag<["-", "--"], "help-hidden">,
+ HelpText<"Display all available options">;
+
+def version : Flag<["--"], "version">,
+ HelpText<"Display the version number and exit">;
+
+def cuda_path_EQ : Joined<["--"], "cuda-path=">,
+ MetaVarName<"<dir>">, HelpText<"Set the system CUDA path">;
+
+def o : JoinedOrSeparate<["-"], "o">, MetaVarName<"<path>">,
+ HelpText<"Path to file to write output">;
+def output : Separate<["--"], "output-file">, Alias<o>, Flags<[HelpHidden]>,
+ HelpText<"Alias for -o">;
+
+def library_path : JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
+ HelpText<"Add <dir> to the library search path">;
+def library_path_S : Separate<["--", "-"], "library-path">,
Flags<[HelpHidden]>,
+ Alias<library_path>;
+def library_path_EQ : Joined<["--", "-"], "library-path=">,
Flags<[HelpHidden]>,
+ Alias<library_path>;
+
+def library : JoinedOrSeparate<["-"], "l">, MetaVarName<"<libname>">,
+ HelpText<"Search for library <libname>">;
+def library_S : Separate<["--", "-"], "library">, Flags<[HelpHidden]>,
+ Alias<library_path>;
+def library_EQ : Joined<["--", "-"], "library=">, Flags<[HelpHidden]>,
+ Alias<library_path>;
+
+def arch : Separate<["--", "-"], "arch">,
+ HelpText<"Specify the 'sm_' name of the target architecture.">;
+def : Joined<["--", "-"], "plugin-opt=mcpu=">,
+ Flags<[HelpHidden, WrapperOnlyOption]>, Alias<arch>;
+
+def feature : Separate<["--", "-"], "feature">, Flags<[WrapperOnlyOption]>,
+ HelpText<"Specify the '+ptx' freature to use for LTO.">;
+
+def g : Flag<["-"], "g">, HelpText<"Specify that this was a debug compile.">;
+def debug : Flag<["--"], "debug">, Alias<g>;
+
+def O : Joined<["--", "-"], "plugin-opt=O">,
+ Flags<[WrapperOnlyOption]>, MetaVarName<"<O0, O1, O2, or O3>">,
+ HelpText<"Optimization level for LTO">;
+
+def plugin_opt : Joined<["--", "-"], "plugin-opt">,
+ Flags<[WrapperOnlyOption, HelpHidden]>;
+
+def save_temps : Flag<["--", "-"], "save-temps">,
+ Flags<[WrapperOnlyOption]>, HelpText<"Save intermediate results">;
+
+def whole_archive : Flag<["--", "-"], "whole-archive">,
+ Flags<[WrapperOnlyOption, HelpHidden]>;
+def no_whole_archive : Flag<["--", "-"], "no-whole-archive">,
+ Flags<[WrapperOnlyOption, HelpHidden]>;
+
+def mllvm : Separate<["-"], "mllvm">, Flags<[WrapperOnlyOption]>,
+ MetaVarName<"<arg>">, HelpText<"Arguments passed to the LLVM invocation">;
+def mllvm_EQ : Joined<["-"], "mllvm=">, Flags<[HelpHidden]>,
+ Alias<mllvm>;
+
+def dry_run : Flag<["--", "-"], "dry-run">, Flags<[WrapperOnlyOption]>,
+ HelpText<"Print generated commands without running.">;
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