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[LinkerWrapper] Support time tracing in the linker wrapper
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Summary:
This patch adds the new `--wrapper-time-trace=` option to write a time
tracing JSON file indicating where time was spent in the linker wrapper.
We also reformat and group some of the existing code to make
constraining the scope easier for time tracing.  We use the `--wrapper`
prefix to set this apart from the time tracing that lld may use.
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@jhuber6
jhuber6 committed Jul 13, 2022
1 parent 96f16a6 commit c70db40
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Showing 2 changed files with 125 additions and 72 deletions.
194 changes: 122 additions & 72 deletions clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
View file
Expand Up @@ -262,11 +262,29 @@ Expected<std::string> findProgram(StringRef Name, ArrayRef<StringRef> Paths) {
return *Path;
}

Error runLinker(StringRef LinkerPath, ArgStringList LinkerArgs) {
SmallVector<StringRef> Args({LinkerPath});
for (StringRef Arg : LinkerArgs)
Args.push_back(Arg);
if (Error Err = executeCommands(LinkerPath, Args))
/// Runs the wrapped linker job with the newly created input.
Error runLinker(ArrayRef<StringRef> Files, const ArgList &Args) {
llvm::TimeTraceScope TimeScope("Execute host linker");

// Render the linker arguments and add the newly created image. We add it
// after the output file to ensure it is linked with the correct libraries.
StringRef LinkerPath = Args.getLastArgValue(OPT_linker_path_EQ);
ArgStringList NewLinkerArgs;
for (const opt::Arg *Arg : Args) {
// Do not forward arguments only intended for the linker wrapper.
if (Arg->getOption().hasFlag(WrapperOnlyOption))
continue;

Arg->render(Args, NewLinkerArgs);
if (Arg->getOption().matches(OPT_o))
llvm::transform(Files, std::back_inserter(NewLinkerArgs),
[&](StringRef Arg) { return Args.MakeArgString(Arg); });
}

SmallVector<StringRef> LinkerArgs({LinkerPath});
for (StringRef Arg : NewLinkerArgs)
LinkerArgs.push_back(Arg);
if (Error Err = executeCommands(LinkerPath, LinkerArgs))
return Err;
return Error::success();
}
Expand Down Expand Up @@ -422,6 +440,7 @@ Error extractFromBuffer(std::unique_ptr<MemoryBuffer> Buffer,
namespace nvptx {
Expected<StringRef> assemble(StringRef InputFile, const ArgList &Args,
bool RDC = true) {
llvm::TimeTraceScope TimeScope("NVPTX Assembler");
// NVPTX uses the ptxas binary to create device object files.
Expected<std::string> PtxasPath = findProgram("ptxas", {CudaBinaryPath});
if (!PtxasPath)
Expand Down Expand Up @@ -462,6 +481,7 @@ Expected<StringRef> assemble(StringRef InputFile, const ArgList &Args,
}

Expected<StringRef> link(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
llvm::TimeTraceScope TimeScope("NVPTX linker");
// NVPTX uses the nvlink binary to link device object files.
Expected<std::string> NvlinkPath = findProgram("nvlink", {CudaBinaryPath});
if (!NvlinkPath)
Expand Down Expand Up @@ -505,6 +525,7 @@ Expected<StringRef> link(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
Expected<StringRef>
fatbinary(ArrayRef<std::pair<StringRef, StringRef>> InputFiles,
const ArgList &Args) {
llvm::TimeTraceScope TimeScope("NVPTX fatbinary");
// NVPTX uses the fatbinary program to bundle the linked images.
Expected<std::string> FatBinaryPath =
findProgram("fatbinary", {CudaBinaryPath});
Expand Down Expand Up @@ -539,6 +560,7 @@ fatbinary(ArrayRef<std::pair<StringRef, StringRef>> InputFiles,

namespace amdgcn {
Expected<StringRef> link(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
llvm::TimeTraceScope TimeScope("AMDGPU linker");
// AMDGPU uses lld to link device object files.
Expected<std::string> LLDPath =
findProgram("lld", {getMainExecutable("lld")});
Expand Down Expand Up @@ -583,6 +605,8 @@ Expected<StringRef> link(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
Expected<StringRef>
fatbinary(ArrayRef<std::pair<StringRef, StringRef>> InputFiles,
const ArgList &Args) {
llvm::TimeTraceScope TimeScope("AMDGPU Fatbinary");

// AMDGPU uses the clang-offload-bundler to bundle the linked images.
Expected<std::string> OffloadBundlerPath = findProgram(
"clang-offload-bundler", {getMainExecutable("clang-offload-bundler")});
Expand Down Expand Up @@ -654,6 +678,7 @@ const char *getLDMOption(const llvm::Triple &T) {
}

Expected<StringRef> link(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
llvm::TimeTraceScope TimeScope("Generic linker");
const llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
StringRef Arch = Args.getLastArgValue(OPT_arch_EQ);

Expand Down Expand Up @@ -846,6 +871,7 @@ bool isValidCIdentifier(StringRef S) {
Error linkBitcodeFiles(SmallVectorImpl<OffloadFile> &InputFiles,
SmallVectorImpl<StringRef> &OutputFiles,
const ArgList &Args) {
llvm::TimeTraceScope TimeScope("Link bitcode files");
const llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));

SmallVector<OffloadFile, 4> BitcodeInputFiles;
Expand Down Expand Up @@ -1068,6 +1094,7 @@ Expected<StringRef> writeOffloadFile(const OffloadFile &File) {
// Compile the module to an object file using the appropriate target machine for
// the host triple.
Expected<StringRef> compileModule(Module &M) {
llvm::TimeTraceScope TimeScope("Compile module");
std::string Msg;
const Target *T = TargetRegistry::lookupTarget(M.getTargetTriple(), Msg);
if (!T)
Expand Down Expand Up @@ -1110,6 +1137,8 @@ Expected<StringRef> compileModule(Module &M) {
Expected<StringRef>
wrapDeviceImages(ArrayRef<std::unique_ptr<MemoryBuffer>> Buffers,
const ArgList &Args, OffloadKind Kind) {
llvm::TimeTraceScope TimeScope("Wrap bundled images");

SmallVector<ArrayRef<char>, 4> BuffersToWrap;
for (const auto &Buffer : Buffers)
BuffersToWrap.emplace_back(
Expand Down Expand Up @@ -1209,6 +1238,7 @@ bundleHIP(ArrayRef<OffloadingImage> Images, const ArgList &Args) {
Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleLinkedOutput(ArrayRef<OffloadingImage> Images, const ArgList &Args,
OffloadKind Kind) {
llvm::TimeTraceScope TimeScope("Bundle linked output");
switch (Kind) {
case OFK_OpenMP:
return bundleOpenMP(Images);
Expand Down Expand Up @@ -1264,13 +1294,17 @@ DerivedArgList getLinkerArgs(ArrayRef<OffloadFile> Input,
Expected<SmallVector<StringRef>>
linkAndWrapDeviceFiles(SmallVectorImpl<OffloadFile> &LinkerInputFiles,
const InputArgList &Args) {
llvm::TimeTraceScope TimeScope("Handle all device input");

DenseMap<OffloadFile::TargetID, SmallVector<OffloadFile, 4>> InputsForTarget;
for (auto &File : LinkerInputFiles)
InputsForTarget[File].emplace_back(std::move(File));
LinkerInputFiles.clear();

DenseMap<OffloadKind, SmallVector<OffloadingImage, 2>> Images;
for (auto &InputForTarget : InputsForTarget) {
llvm::TimeTraceScope TimeScope("Link device input");

SmallVector<OffloadFile, 4> &Input = InputForTarget.getSecond();
auto LinkerArgs = getLinkerArgs(Input, Args);

Expand Down Expand Up @@ -1378,56 +1412,13 @@ Optional<std::string> searchLibrary(StringRef Input, StringRef Root,
return searchLibraryBaseName(Input, Root, SearchPaths);
}

} // namespace

int main(int Argc, char **Argv) {
InitLLVM X(Argc, Argv);
InitializeAllTargetInfos();
InitializeAllTargets();
InitializeAllTargetMCs();
InitializeAllAsmParsers();
InitializeAllAsmPrinters();

LinkerExecutable = 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-linker-wrapper [options] -- <options to passed to the linker>",
"\nA wrapper utility over the host linker. It scans the input files\n"
"for sections that require additional processing prior to linking.\n"
"The will then transparently pass all arguments and input to the\n"
"specified host linker to create the final binary.\n",
Args.hasArg(OPT_help_hidden), Args.hasArg(OPT_help_hidden));
return EXIT_SUCCESS;
}
if (Args.hasArg(OPT_v)) {
printVersion(outs());
return EXIT_SUCCESS;
}

// This forwards '-pass-remarks=' to the LTO backend if present.
cl::HideUnrelatedOptions(ClangLinkerWrapperCategory);
cl::ParseCommandLineOptions(Argc, Argv);

Verbose = Args.hasArg(OPT_verbose);
DryRun = Args.hasArg(OPT_dry_run);
SaveTemps = Args.hasArg(OPT_save_temps);
ExecutableName = Args.getLastArgValue(OPT_o, "a.out");
CudaBinaryPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
if (!CudaBinaryPath.empty())
CudaBinaryPath = CudaBinaryPath + "/bin";
/// Search the input files and libraries for embedded device offloading code and
/// add it to the list of files to be linked. Files coming from static libraries
/// are only added to the input if they are used by an existing input file.
Expected<SmallVector<OffloadFile>> getDeviceInput(const ArgList &Args) {
llvm::TimeTraceScope TimeScope("ExtractDeviceCode");

StringRef Root = Args.getLastArgValue(OPT_sysroot_EQ);

SmallVector<StringRef> LibraryPaths;
for (const opt::Arg *Arg : Args.filtered(OPT_library_path))
LibraryPaths.push_back(Arg->getValue());
Expand Down Expand Up @@ -1482,29 +1473,88 @@ int main(int Argc, char **Argv) {
for (auto &LazyFile : LazyInputFiles)
if (IsTargetUsed.contains(LazyFile))
InputFiles.emplace_back(std::move(LazyFile));
LazyInputFiles.clear();

// Link and wrap the device images extracted from the linker input.
auto FilesOrErr = linkAndWrapDeviceFiles(InputFiles, Args);
if (!FilesOrErr)
reportError(FilesOrErr.takeError());
return InputFiles;
}

// Render the linker arguments and add the newly created image. We add it
// after the output file to ensure it is linked with the correct libraries.
ArgStringList LinkerArgs;
for (const opt::Arg *Arg : Args) {
if (Arg->getOption().hasFlag(WrapperOnlyOption))
continue;
Arg->render(Args, LinkerArgs);
if (Arg->getOption().matches(OPT_o))
llvm::transform(*FilesOrErr, std::back_inserter(LinkerArgs),
[&](StringRef Arg) { return Args.MakeArgString(Arg); });
} // namespace

int main(int Argc, char **Argv) {
InitLLVM X(Argc, Argv);
InitializeAllTargetInfos();
InitializeAllTargets();
InitializeAllTargetMCs();
InitializeAllAsmParsers();
InitializeAllAsmPrinters();

LinkerExecutable = 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-linker-wrapper [options] -- <options to passed to the linker>",
"\nA wrapper utility over the host linker. It scans the input files\n"
"for sections that require additional processing prior to linking.\n"
"The will then transparently pass all arguments and input to the\n"
"specified host linker to create the final binary.\n",
Args.hasArg(OPT_help_hidden), Args.hasArg(OPT_help_hidden));
return EXIT_SUCCESS;
}
if (Args.hasArg(OPT_v)) {
printVersion(outs());
return EXIT_SUCCESS;
}

// Run the host linking job with the rendered arguments.
StringRef LinkerPath = Args.getLastArgValue(OPT_linker_path_EQ);
if (Error Err = runLinker(LinkerPath, LinkerArgs))
reportError(std::move(Err));
// This forwards '-pass-remarks=' to the LTO backend if present.
cl::HideUnrelatedOptions(ClangLinkerWrapperCategory);
cl::ParseCommandLineOptions(Argc, Argv);

Verbose = Args.hasArg(OPT_verbose);
DryRun = Args.hasArg(OPT_dry_run);
SaveTemps = Args.hasArg(OPT_save_temps);
ExecutableName = Args.getLastArgValue(OPT_o, "a.out");
CudaBinaryPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
if (!CudaBinaryPath.empty())
CudaBinaryPath = CudaBinaryPath + "/bin";

if (Args.hasArg(OPT_wrapper_time_trace_eq)) {
unsigned Granularity;
Args.getLastArgValue(OPT_wrapper_time_trace_granularity, "500")
.getAsInteger(10, Granularity);
timeTraceProfilerInitialize(Granularity, Argv[0]);
}

{
llvm::TimeTraceScope TimeScope("Execute linker wrapper");

// Extract the device input files stored in the host fat binary.
auto DeviceInputFiles = getDeviceInput(Args);
if (!DeviceInputFiles)
reportError(DeviceInputFiles.takeError());

// Link and wrap the device images extracted from the linker input.
auto FilesOrErr = linkAndWrapDeviceFiles(*DeviceInputFiles, Args);
if (!FilesOrErr)
reportError(FilesOrErr.takeError());

// Run the host linking job with the rendered arguments.
if (Error Err = runLinker(*FilesOrErr, Args))
reportError(std::move(Err));
}

if (const opt::Arg *Arg = Args.getLastArg(OPT_wrapper_time_trace_eq)) {
if (Error Err = timeTraceProfilerWrite(Arg->getValue(), ExecutableName))
reportError(std::move(Err));
timeTraceProfilerCleanup();
}

// Remove the temporary files created.
if (!SaveTemps)
Expand Down
3 changes: 3 additions & 0 deletions clang/tools/clang-linker-wrapper/LinkerWrapperOpts.td
View file
Expand Up @@ -55,6 +55,9 @@ def save_temps : Flag<["--"], "save-temps">,
def wrapper_time_trace_eq : Joined<["--"], "wrapper-time-trace=">,
Flags<[WrapperOnlyOption]>, MetaVarName<"<file>">,
HelpText<"Enable time-trace and write the output to <file>">;
def wrapper_time_trace_granularity : Joined<["--"], "wrapper-time-trace-granularity=">,
Flags<[WrapperOnlyOption]>, MetaVarName<"<number>">,
HelpText<"Set the granularity of time-trace updates">;

// Flags passed to the device linker.
def arch_EQ : Joined<["--"], "arch=">,
Expand Down

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