[clang] [Clang] Introduce 'clang-nvlink-wrappaer' to work around 'nvlink' (PR #96561)

via cfe-commits cfe-commits at lists.llvm.org
Mon Jun 24 14:40:07 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-driver

Author: Joseph Huber (jhuber6)

<details>
<summary>Changes</summary>

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.


---

Patch is 37.19 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/96561.diff


8 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Cuda.cpp (+8-53) 
- (modified) clang/lib/Driver/ToolChains/Cuda.h (+3) 
- (modified) clang/test/Driver/cuda-cross-compiling.c (+4-4) 
- (added) clang/test/Driver/nvlink-wrapper.c (+64) 
- (modified) clang/tools/CMakeLists.txt (+1) 
- (added) clang/tools/clang-nvlink-wrapper/CMakeLists.txt (+44) 
- (added) clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp (+671) 
- (added) clang/tools/clang-nvlink-wrapper/NVLinkOpts.td (+68) 


``````````diff
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..f839c36d23e51 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..488bcd062467f
--- /dev/null
+++ b/clang/test/Driver/nvlink-wrapper.c
@@ -0,0 +1,64 @@
+// 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 y;
+extern int __attribute__((weak)) w;
+
+int bar() {
+  return x + y + w;
+}
+#else
+int __attribute__((visibility("hidden"))) x = 999;
+#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/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..d48bf4e37ecfe
--- /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 =
+      creat...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/96561


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