llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-spir-v

Author: Arvind Sudarsanam (asudarsa)

<details>
<summary>Changes</summary>

This PR is one of the many PRs in the SYCL upstreaming effort focusing on 
device code linking during the SYCL offload compilation process. RFC: 
https://discourse.llvm.org/t/rfc-offloading-design-for-sycl-offload-kind-and-spir-targets/74088

In this PR, we introduce a new tool that will be used to perform device code 
linking for SYCL offload kind. It accepts SYCL device objects in LLVM IR 
bitcode format and will generate a fully linked device object that can then be 
wrapped and linked into the host object.

A primary use case for this tool is to perform device code linking for objects 
with SYCL offload kind inside the clang-linker-wrapper. It can also be invoked 
via clang driver as follows:

`clang --target=spirv64 --sycl-link input.bc`

Device code linking for SYCL offloading kind has a number of known quirks that 
makes it difficult to use in a unified offloading setting. Two of the primary 
issues are:
1. Several finalization steps are required to be run on the fully-linked LLVM 
IR bitcode to gaurantee conformance to SYCL standards. This step is unique to 
SYCL offloading compilation flow.
2. SPIR-V LLVM Translator tool is an extenal tool and hence SPIR-V IR code 
generation cannot be done as part of LTO. This limitation will be lifted once 
SPIR-V backend is available as a viable LLVM backend.

Hence, we introduce this new tool to provide a clean wrapper to perform SYCL 
device linking.

Thanks

---

Patch is 32.39 KiB, truncated to 20.00 KiB below, full version: 
https://github.com/llvm/llvm-project/pull/112245.diff


14 Files Affected:

- (added) clang/docs/ClangSYCLLinkWrapper.rst (+80) 
- (modified) clang/docs/index.rst (+1) 
- (modified) clang/include/clang/Driver/Options.td (+4-1) 
- (modified) clang/lib/Driver/Driver.cpp (+5) 
- (modified) clang/lib/Driver/ToolChains/SPIRV.cpp (+12) 
- (modified) clang/lib/Driver/ToolChains/SPIRV.h (+3-2) 
- (added) clang/test/Driver/Inputs/libsycl-complex.bc () 
- (added) clang/test/Driver/Inputs/libsycl-crt.bc () 
- (added) clang/test/Driver/clang-sycl-link-wrapper-test.cpp (+9) 
- (added) clang/test/Driver/sycl-link-spirv-target.cpp (+7) 
- (modified) clang/tools/CMakeLists.txt (+1) 
- (added) clang/tools/clang-sycl-link-wrapper/CMakeLists.txt (+28) 
- (added) clang/tools/clang-sycl-link-wrapper/ClangSYCLLinkWrapper.cpp (+530) 
- (added) clang/tools/clang-sycl-link-wrapper/SYCLLinkOpts.td (+47) 


``````````diff
diff --git a/clang/docs/ClangSYCLLinkWrapper.rst 
b/clang/docs/ClangSYCLLinkWrapper.rst
new file mode 100644
index 00000000000000..8ceb17f6af9d86
--- /dev/null
+++ b/clang/docs/ClangSYCLLinkWrapper.rst
@@ -0,0 +1,80 @@
+=======================
+Clang SYCL Link Wrapper
+=======================
+
+.. contents::
+   :local:
+
+.. _clang-sycl-link-wrapper:
+
+Introduction
+============
+
+This tool works as a wrapper around the SYCL device code linking process.
+The purpose of this wrapper is to provide an interface to link SYCL device
+bitcode in LLVM IR format, SYCL device bitcode in SPIR-V IR format, and native
+binary objects, and then use the SPIR-V LLVM Translator tool on fully linked
+device objects to produce the final output.
+After the linking stage, the fully linked device code in LLVM IR format may
+undergo several SYCL-specific finalization steps before the SPIR-V code
+generation step.
+The wrapper will also support the Ahead-Of-Time (AOT) compilation flow. AOT
+compilation is the process of invoking the back-end at compile time to produce
+the final binary, as opposed to just-in-time (JIT) compilation when final code
+generation is deferred until application runtime.
+
+Device code linking for SYCL offloading has several known quirks that
+make it difficult to use in a unified offloading setting. Two of the primary
+issues are:
+1. Several finalization steps are required to be run on the fully linked LLVM
+IR bitcode to guarantee conformance to SYCL standards. This step is unique to
+the SYCL offloading compilation flow.
+2. The SPIR-V LLVM Translator tool is an external tool and hence SPIR-V IR code
+generation cannot be done as part of LTO. This limitation can be lifted once
+the SPIR-V backend is available as a viable LLVM backend.
+
+This tool has been proposed to work around these issues.
+
+Usage
+=====
+
+This tool can be used with the following options. Several of these options will
+be passed down to downstream tools like 'llvm-link', 'llvm-spirv', etc.
+
+.. code-block:: console
+
+  OVERVIEW: A utility that wraps around the SYCL device code linking process.
+  This enables linking and code generation for SPIR-V JIT targets and AOT
+  targets.
+
+  USAGE: clang-sycl-link-wrapper [options]
+
+  OPTIONS:
+    --arch <value>                Specify the name of the target architecture.
+    --dry-run                     Print generated commands without running.
+    -g                            Specify that this was a debug compile.
+    -help-hidden                  Display all available options
+    -help                         Display available options (--help-hidden for 
more)
+    --library-path=<dir>          Set the library path for SYCL device 
libraries
+    -o <path>                     Path to file to write output
+    --save-temps                  Save intermediate results
+    --triple <value>              Specify the target triple.
+    --version                     Display the version number and exit
+    -v                            Print verbose information
+    -spirv-dump-device-code=<dir> Directory to dump SPIR-V IR code into
+    -is-windows-msvc-env          Specify if we are compiling under windows 
environment
+    -llvm-spirv-options=<value>   Pass options to llvm-spirv tool
+
+Example
+=======
+
+This tool is intended to be invoked when targeting any of the target offloading
+toolchains. When the --sycl-link option is passed to the clang driver, the
+driver will invoke the linking job of the target offloading toolchain, which in
+turn will invoke this tool. This tool can be used to create one or more fully
+linked device images that are ready to be wrapped and linked with host code to
+generate the final executable.
+
+.. code-block:: console
+
+  clang-sycl-link-wrapper --triple spirv64 --arch native input.bc
diff --git a/clang/docs/index.rst b/clang/docs/index.rst
index 4a497f4d9bcc3c..ccdc16d3e07699 100644
--- a/clang/docs/index.rst
+++ b/clang/docs/index.rst
@@ -97,6 +97,7 @@ Using Clang Tools
    ClangOffloadBundler
    ClangOffloadPackager
    ClangRepl
+   ClangSYCLLinkWrapper
 
 Design Documents
 ================
diff --git a/clang/include/clang/Driver/Options.td 
b/clang/include/clang/Driver/Options.td
index 3f4d1a328b4c27..245af5a539a4fa 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -6728,7 +6728,10 @@ def fsycl : Flag<["-"], "fsycl">,
 def fno_sycl : Flag<["-"], "fno-sycl">,
   Visibility<[ClangOption, CLOption]>,
   Group<sycl_Group>, HelpText<"Disables SYCL kernels compilation for device">;
-
+def sycl_link : Flag<["--"], "sycl-link">, Flags<[HelpHidden]>,
+  Visibility<[ClangOption, CLOption]>,
+  Group<sycl_Group>, HelpText<"Perform link through clang-sycl-link-wrapper 
via the target "
+  "offloading toolchain.">;
 // OS-specific options
 let Flags = [TargetSpecific] in {
 defm android_pad_segment : BooleanFFlag<"android-pad-segment">, Group<f_Group>;
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index d0c8bdba0ede95..184eafa137b178 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -4780,6 +4780,11 @@ Action *Driver::ConstructPhaseAction(
   if (Phase == phases::Assemble && Input->getType() != types::TY_PP_Asm)
     return Input;
 
+  // Use of --sycl-link will only allow for the link phase to occur. This is
+  // for all input files.
+  if (Args.hasArg(options::OPT_sycl_link) && Phase != phases::Link)
+    return Input;
+
   // Build the appropriate action.
   switch (Phase) {
   case phases::Link:
diff --git a/clang/lib/Driver/ToolChains/SPIRV.cpp 
b/clang/lib/Driver/ToolChains/SPIRV.cpp
index ce900600cbee51..860fd932a58718 100644
--- a/clang/lib/Driver/ToolChains/SPIRV.cpp
+++ b/clang/lib/Driver/ToolChains/SPIRV.cpp
@@ -95,7 +95,19 @@ void SPIRV::Linker::ConstructJob(Compilation &C, const 
JobAction &JA,
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
+  // Use of --sycl-link will call the clang-sycl-link-wrapper instead of
+  // the default linker (spirv-link).
+  if (Args.hasArg(options::OPT_sycl_link))
+    Linker = ToolChain.GetProgramPath("clang-sycl-link-wrapper");
   C.addCommand(std::make_unique<Command>(JA, *this, 
ResponseFileSupport::None(),
                                          Args.MakeArgString(Linker), CmdArgs,
                                          Inputs, Output));
 }
+
+SPIRVToolChain::SPIRVToolChain(const Driver &D, const llvm::Triple &Triple,
+                               const ArgList &Args)
+    : ToolChain(D, Triple, Args) {
+  NativeLLVMSupport = Args.hasArg(options::OPT_sycl_link);
+}
+
+bool SPIRVToolChain::HasNativeLLVMSupport() const { return NativeLLVMSupport; }
diff --git a/clang/lib/Driver/ToolChains/SPIRV.h 
b/clang/lib/Driver/ToolChains/SPIRV.h
index d4247ee0557f4b..d59a8c76ed4737 100644
--- a/clang/lib/Driver/ToolChains/SPIRV.h
+++ b/clang/lib/Driver/ToolChains/SPIRV.h
@@ -57,8 +57,7 @@ class LLVM_LIBRARY_VISIBILITY SPIRVToolChain final : public 
ToolChain {
 
 public:
   SPIRVToolChain(const Driver &D, const llvm::Triple &Triple,
-                 const llvm::opt::ArgList &Args)
-      : ToolChain(D, Triple, Args) {}
+                 const llvm::opt::ArgList &Args);
 
   bool useIntegratedAs() const override { return true; }
 
@@ -72,6 +71,7 @@ class LLVM_LIBRARY_VISIBILITY SPIRVToolChain final : public 
ToolChain {
   }
   bool isPICDefaultForced() const override { return false; }
   bool SupportsProfiling() const override { return false; }
+  bool HasNativeLLVMSupport() const override;
 
   clang::driver::Tool *SelectTool(const JobAction &JA) const override;
 
@@ -81,6 +81,7 @@ class LLVM_LIBRARY_VISIBILITY SPIRVToolChain final : public 
ToolChain {
 
 private:
   clang::driver::Tool *getTranslator() const;
+  bool NativeLLVMSupport;
 };
 
 } // namespace toolchains
diff --git a/clang/test/Driver/Inputs/libsycl-complex.bc 
b/clang/test/Driver/Inputs/libsycl-complex.bc
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/clang/test/Driver/Inputs/libsycl-crt.bc 
b/clang/test/Driver/Inputs/libsycl-crt.bc
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/clang/test/Driver/clang-sycl-link-wrapper-test.cpp 
b/clang/test/Driver/clang-sycl-link-wrapper-test.cpp
new file mode 100644
index 00000000000000..5004725536e98a
--- /dev/null
+++ b/clang/test/Driver/clang-sycl-link-wrapper-test.cpp
@@ -0,0 +1,9 @@
+// Tests the clang-sycl-link-wrapper tool
+//
+// Test a simple case without arguments
+// RUN: %clangxx -fsycl -emit-llvm -c %s -o %t.bc
+// RUN: clang-sycl-link-wrapper --dry-run -triple spirv64 %t.bc 
--library-path=%S/Inputs -o a.spv 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CMDS
+// CMDS: "{{.*}}llvm-link{{.*}}" {{.*}}.bc -o [[FIRSTLLVMLINKOUT:.*]].bc 
--suppress-warnings
+// CMDS-NEXT: "{{.*}}llvm-link{{.*}}" -only-needed [[FIRSTLLVMLINKOUT]].bc 
{{.*}}libsycl-crt.bc {{.*}}libsycl-complex.bc -o [[SECONDLLVMLINKOUT:.*]].bc 
--suppress-warnings
+// CMDS-NEXT: "{{.*}}llvm-spirv{{.*}}" {{.*}}-o a.spv [[SECONDLLVMLINKOUT]].bc
diff --git a/clang/test/Driver/sycl-link-spirv-target.cpp 
b/clang/test/Driver/sycl-link-spirv-target.cpp
new file mode 100644
index 00000000000000..550d40aac5499d
--- /dev/null
+++ b/clang/test/Driver/sycl-link-spirv-target.cpp
@@ -0,0 +1,7 @@
+// Tests the driver when linking LLVM IR bitcode files and targeting SPIR-V
+// architecture.
+//
+// RUN: touch %t.bc
+// RUN: %clangxx --target=spirv64 --sycl-link -### %t.bc 2>&1 \
+// RUN:   | FileCheck %s -check-prefix=LINK
+// LINK: "{{.*}}clang-sycl-link-wrapper{{.*}}" "{{.*}}.bc" "-o" "a.out"
diff --git a/clang/tools/CMakeLists.txt b/clang/tools/CMakeLists.txt
index 88e29412e54350..d704ca5c62c97b 100644
--- a/clang/tools/CMakeLists.txt
+++ b/clang/tools/CMakeLists.txt
@@ -12,6 +12,7 @@ add_clang_subdirectory(clang-nvlink-wrapper)
 add_clang_subdirectory(clang-offload-packager)
 add_clang_subdirectory(clang-offload-bundler)
 add_clang_subdirectory(clang-scan-deps)
+add_clang_subdirectory(clang-sycl-link-wrapper)
 add_clang_subdirectory(clang-installapi)
 if(HAVE_CLANG_REPL_SUPPORT)
   add_clang_subdirectory(clang-repl)
diff --git a/clang/tools/clang-sycl-link-wrapper/CMakeLists.txt 
b/clang/tools/clang-sycl-link-wrapper/CMakeLists.txt
new file mode 100644
index 00000000000000..c51f6f977dddd7
--- /dev/null
+++ b/clang/tools/clang-sycl-link-wrapper/CMakeLists.txt
@@ -0,0 +1,28 @@
+set(LLVM_LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  Option
+  )
+
+set(LLVM_TARGET_DEFINITIONS SYCLLinkOpts.td)
+tablegen(LLVM SYCLLinkOpts.inc -gen-opt-parser-defs)
+add_public_tablegen_target(SYCLLinkWrapperOpts)
+
+if(NOT CLANG_BUILT_STANDALONE)
+  set(tablegen_deps intrinsics_gen SYCLLinkWrapperOpts)
+endif()
+
+add_clang_tool(clang-sycl-link-wrapper
+  ClangSYCLLinkWrapper.cpp
+
+  DEPENDS
+  ${tablegen_deps}
+  )
+
+set(CLANG_SYCL_LINK_WRAPPER_LIB_DEPS
+  clangBasic
+  )
+
+target_link_libraries(clang-sycl-link-wrapper
+  PRIVATE
+  ${CLANG_SYCL_LINK_WRAPPER_LIB_DEPS}
+  )
diff --git a/clang/tools/clang-sycl-link-wrapper/ClangSYCLLinkWrapper.cpp 
b/clang/tools/clang-sycl-link-wrapper/ClangSYCLLinkWrapper.cpp
new file mode 100644
index 00000000000000..31afa26c46518d
--- /dev/null
+++ b/clang/tools/clang-sycl-link-wrapper/ClangSYCLLinkWrapper.cpp
@@ -0,0 +1,530 @@
+//=-- clang-sycl-link-wrapper/ClangSYCLLinkWrapper.cpp - SYCL 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 sequence of steps required to link device code in
+// SYCL fat objects. SYCL device code linking requires a complex sequence of
+// steps that include linking of llvm bitcode files, linking device library
+// files with the fully linked source bitcode file(s), running several SYCL
+// specific post-link steps on the fully linked bitcode file(s), and finally
+// generating target-specific device code. This tool can be removed once SYCL
+// linking is ported to `ld.lld`.
+//
+//===---------------------------------------------------------------------===//
+
+#include "clang/Basic/Version.h"
+
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/CodeGen/CommandFlags.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/IRReader/IRReader.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/Remarks/HotnessThresholdParser.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/TimeProfiler.h"
+#include "llvm/Support/WithColor.h"
+
+using namespace llvm;
+using namespace llvm::opt;
+using namespace llvm::object;
+
+/// Save intermediary results.
+static bool SaveTemps = false;
+
+/// Print arguments without executing.
+static bool DryRun = false;
+
+/// Print verbose output.
+static bool Verbose = false;
+
+/// Filename of the output being created.
+static StringRef OutputFile;
+
+/// Directory to dump SPIR-V IR if requested by user.
+static SmallString<128> SPIRVDumpDir;
+
+static void printVersion(raw_ostream &OS) {
+  OS << clang::getClangToolFullVersion("clang-sycl-link-wrapper") << '\n';
+}
+
+/// The value of `argv[0]` when run.
+static const char *Executable;
+
+/// Temporary files to be cleaned up.
+static SmallVector<SmallString<128>> TempFiles;
+
+namespace {
+// Must not overlap with llvm::opt::DriverFlag.
+enum WrapperFlags { WrapperOnlyOption = (1 << 4) };
+
+enum ID {
+  OPT_INVALID = 0, // This is not an option ID.
+#define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
+#include "SYCLLinkOpts.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 "SYCLLinkOpts.inc"
+#undef PREFIX
+
+static constexpr OptTable::Info InfoTable[] = {
+#define OPTION(...) LLVM_CONSTRUCT_OPT_INFO(__VA_ARGS__),
+#include "SYCLLinkOpts.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);
+}
+
+std::string getMainExecutable(const char *Name) {
+  void *Ptr = (void *)(intptr_t)&getMainExecutable;
+  auto COWPath = sys::fs::getMainExecutable(Name, Ptr);
+  return sys::path::parent_path(COWPath).str();
+}
+
+Expected<StringRef> createTempFile(const ArgList &Args, const Twine &Prefix,
+                                   StringRef Extension) {
+  SmallString<128> OutputFile;
+  if (Args.hasArg(OPT_save_temps)) {
+    // Generate a unique path name without creating a file
+    sys::fs::createUniquePath(Prefix + "-%%%%%%." + Extension, OutputFile,
+                              /*MakeAbsolute=*/false);
+  } 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(const ArgList &Args, StringRef Name,
+                                  ArrayRef<StringRef> Paths) {
+  if (Args.hasArg(OPT_dry_run))
+    return Name.str();
+  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;
+}
+
+void printCommands(ArrayRef<StringRef> CmdArgs) {
+  if (CmdArgs.empty())
+    return;
+
+  llvm::errs() << " \"" << CmdArgs.front() << "\" ";
+  llvm::errs() << llvm::join(std::next(CmdArgs.begin()), CmdArgs.end(), " ")
+               << "\n";
+}
+
+/// Execute the command \p ExecutablePath with the arguments \p Args.
+Error executeCommands(StringRef ExecutablePath, ArrayRef<StringRef> Args) {
+  if (Verbose || DryRun)
+    printCommands(Args);
+
+  if (!DryRun)
+    if (sys::ExecuteAndWait(ExecutablePath, Args))
+      return createStringError(
+          "'%s' failed", sys::path::filename(ExecutablePath).str().c_str());
+  return Error::success();
+}
+
+Expected<SmallVector<std::string>> getInput(const ArgList &Args) {
+  // Collect all input bitcode files to be passed to llvm-link.
+  SmallVector<std::string> BitcodeFiles;
+  for (const opt::Arg *Arg : Args.filtered(OPT_INPUT)) {
+    std::optional<std::string> Filename = std::string(Arg->getValue());
+    if (!Filename || !sys::fs::exists(*Filename) ||
+        sys::fs::is_directory(*Filename))
+      continue;
+    file_magic Magic;
+    if (auto EC = identify_magic(*Filename, Magic))
+      return createStringError("Failed to open file " + *Filename);
+    if (Magic != file_magic::bitcode)
+      return createStringError("Unsupported file type");
+    BitcodeFiles.push_back(*Filename);
+  }
+  return BitcodeFiles;
+}
+
+/// Link all SYCL device input files into one before adding device library
+/// files. Device linking is performed using llvm-link tool.
+/// 'InputFiles' is the list of all LLVM IR device input files.
+/// 'Args' encompasses all arguments required for linking and wrapping device
+/// code and will be parsed to generate options required to be passed into the
+/// llvm-link tool.
+Expected<StringRef> linkDeviceInputFiles(ArrayRef<std::string> InputFiles,
+                                         const ArgList &Args) {
+  llvm::TimeTraceScope TimeScope("SYCL LinkDeviceInputFiles");
+  Expected<std::string> LLVMLinkPath =
+      findProgram(Args, "llvm-link", {getMainExecutable("llvm-link")});
+  if (!LLVMLinkPath)
+    return LLVMLinkPath.takeError();
+
+  SmallVector<StringRef> CmdArgs;
+  CmdArgs.push_back(*LLVMLinkPath);
+  for (auto &File : InputFiles)
+    CmdArgs.push_back(File);
+  // Create a new file to write the linked device file to.
+  auto OutFileOrErr =
+      createTempFile(Args, sys::path::filename(OutputFile), "bc");
+  if (!OutFileOrErr)
+    return OutFileOrErr.takeError();
+  CmdArgs.push_back("-o");
+  CmdArgs.push_back(*OutFileOrErr);
+  CmdArgs.push_back("--suppress-warnings");
+  if (Error Err = executeCommands(*LLVMLinkPath, CmdArgs))
+    return std::move(Err);
+  return *OutFileOrErr;
+}
+
+const SmallVector<std::string> SYCLDeviceLibNames = {
+    "libsycl-crt.bc",
+    "libsycl-complex.bc",
+    "libsycl-complex-fp64.bc",
+    "libsycl-cmath.bc",
+    "libsycl-cmath-fp64.bc",
+    "libsycl-imf.bc",
+    "libsycl-imf-fp64.bc",
+    "libsycl-imf-bf16.bc",
+    "libsycl-fallback-cassert.bc",
+    "libsycl-fallback-cstring.bc",
+    "libsycl-fallback-complex.bc",
+    "libsycl-fallback-complex-fp64.bc",
+    "libsycl-fallback-cmath.bc",
+    "libsycl-fallback-cmath-fp64.bc",
+    "libsycl-fallback-imf.bc",
+    "libsy...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/112245
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