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[LinkerWrapper] Support relocatable linking for offloading #80066

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[LinkerWrapper] Support relocatable linking for offloading
jhuber6 Jan 30, 2024
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8 changes: 8 additions & 0 deletions clang/test/Driver/linker-wrapper-image.c
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Expand Up @@ -9,6 +9,8 @@
// RUN: -fembed-offload-object=%t.out
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-linux-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=OPENMP,OPENMP-ELF
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run -r --host-triple=x86_64-unknown-linux-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=OPENMP-ELF,OPENMP-REL
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-windows-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=OPENMP,OPENMP-COFF

Expand All @@ -19,6 +21,8 @@
// OPENMP-COFF: @__start_omp_offloading_entries = weak_odr hidden constant [0 x %struct.__tgt_offload_entry] zeroinitializer, section "omp_offloading_entries$OA"
// OPENMP-COFF-NEXT: @__stop_omp_offloading_entries = weak_odr hidden constant [0 x %struct.__tgt_offload_entry] zeroinitializer, section "omp_offloading_entries$OZ"

// OPENMP-REL: @.omp_offloading.device_image = internal unnamed_addr constant [[[SIZE:[0-9]+]] x i8] c"\10\FF\10\AD{{.*}}", section ".llvm.offloading.relocatable", align 8

// OPENMP: @.omp_offloading.device_image = internal unnamed_addr constant [[[SIZE:[0-9]+]] x i8] c"\10\FF\10\AD{{.*}}", section ".llvm.offloading", align 8
// OPENMP-NEXT: @.omp_offloading.device_images = internal unnamed_addr constant [1 x %__tgt_device_image] [%__tgt_device_image { ptr getelementptr inbounds ([[[BEGIN:[0-9]+]] x i8], ptr @.omp_offloading.device_image, i64 1, i64 0), ptr getelementptr inbounds ([[[END:[0-9]+]] x i8], ptr @.omp_offloading.device_image, i64 1, i64 0), ptr @__start_omp_offloading_entries, ptr @__stop_omp_offloading_entries }]
// OPENMP-NEXT: @.omp_offloading.descriptor = internal constant %__tgt_bin_desc { i32 1, ptr @.omp_offloading.device_images, ptr @__start_omp_offloading_entries, ptr @__stop_omp_offloading_entries }
Expand All @@ -42,6 +46,8 @@
// RUN: -fembed-offload-object=%t.out
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-linux-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=CUDA,CUDA-ELF
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run -r --host-triple=x86_64-unknown-linux-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=CUDA,CUDA-ELF
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-windows-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=CUDA,CUDA-COFF

Expand Down Expand Up @@ -140,6 +146,8 @@
// RUN: -fembed-offload-object=%t.out
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-linux-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=HIP,HIP-ELF
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-linux-gnu -r \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=HIP,HIP-ELF
// RUN: clang-linker-wrapper --print-wrapped-module --dry-run --host-triple=x86_64-unknown-windows-gnu \
// RUN: --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefixes=HIP,HIP-COFF

Expand Down
32 changes: 29 additions & 3 deletions clang/test/Driver/linker-wrapper.c
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Expand Up @@ -176,10 +176,36 @@ __attribute__((visibility("protected"), used)) int x;
// RUN: --image=file=%t.elf.o,kind=openmp,triple=x86_64-unknown-linux-gnu \
// RUN: --image=file=%t.elf.o,kind=openmp,triple=x86_64-unknown-linux-gnu
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o -fembed-offload-object=%t.out
// RUN: llvm-ar rcs %t.a %t.o
// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run \
// RUN: --linker-path=/usr/bin/ld.lld -- -r --whole-archive %t.a --no-whole-archive \
// RUN: --linker-path=/usr/bin/ld.lld -- -r %t.o \
// RUN: %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=RELOCATABLE-LINK

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need to check device fatbin bundling is done and device wrapper fatbin variable using internal linkage and in postfixed section.

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Added a test for the HIP and CUDA cases as well as an additional check on passing -r to the wrapper image generation.

// RELOCATABLE-LINK-NOT: clang{{.*}} -o {{.*}}.img --target=x86_64-unknown-linux-gnu
// RELOCATABLE-LINK: clang{{.*}} -o {{.*}}.img --target=x86_64-unknown-linux-gnu
// RELOCATABLE-LINK: /usr/bin/ld.lld{{.*}}-r
// RELOCATABLE-LINK: llvm-objcopy{{.*}}a.out --remove-section .llvm.offloading

// RUN: clang-offload-packager -o %t.out \
// RUN: --image=file=%t.elf.o,kind=hip,triple=amdgcn-amd-amdhsa,arch=gfx90a \
// RUN: --image=file=%t.elf.o,kind=hip,triple=amdgcn-amd-amdhsa,arch=gfx90a
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o -fembed-offload-object=%t.out
// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run \
// RUN: --linker-path=/usr/bin/ld.lld -- -r %t.o \
// RUN: %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=RELOCATABLE-LINK-HIP

// RELOCATABLE-LINK-HIP: clang{{.*}} -o {{.*}}.img --target=amdgcn-amd-amdhsa
// RELOCATABLE-LINK-HIP: clang-offload-bundler{{.*}} -type=o -bundle-align=4096 -targets=host-x86_64-unknown-linux,hipv4-amdgcn-amd-amdhsa--gfx90a -input=/dev/null -input={{.*}} -output={{.*}}
// RELOCATABLE-LINK-HIP: /usr/bin/ld.lld{{.*}}-r
// RELOCATABLE-LINK-HIP: llvm-objcopy{{.*}}a.out --remove-section .llvm.offloading

// RUN: clang-offload-packager -o %t.out \
// RUN: --image=file=%t.elf.o,kind=cuda,triple=nvptx64-nvidia-cuda,arch=sm_89 \
// RUN: --image=file=%t.elf.o,kind=cuda,triple=nvptx64-nvidia-cuda,arch=sm_89
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o -fembed-offload-object=%t.out
// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run \
// RUN: --linker-path=/usr/bin/ld.lld -- -r %t.o \
// RUN: %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=RELOCATABLE-LINK-CUDA

// RELOCATABLE-LINK-CUDA: clang{{.*}} -o {{.*}}.img --target=nvptx64-nvidia-cuda
// RELOCATABLE-LINK-CUDA: fatbinary{{.*}} -64 --create {{.*}}.fatbin --image=profile=sm_89,file={{.*}}.img
// RELOCATABLE-LINK-CUDA: /usr/bin/ld.lld{{.*}}-r
// RELOCATABLE-LINK-CUDA: llvm-objcopy{{.*}}a.out --remove-section .llvm.offloading
78 changes: 71 additions & 7 deletions clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
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Expand Up @@ -241,6 +241,70 @@ Expected<std::string> findProgram(StringRef Name, ArrayRef<StringRef> Paths) {
return *Path;
}

/// Returns the hashed value for a constant string.
std::string getHash(StringRef Str) {
llvm::MD5 Hasher;
llvm::MD5::MD5Result Hash;
Hasher.update(Str);
Hasher.final(Hash);
return llvm::utohexstr(Hash.low(), /*LowerCase=*/true);
}

/// Renames offloading entry sections in a relocatable link so they do not
/// conflict with a later link job.
Error relocateOffloadSection(const ArgList &Args, StringRef Output) {
llvm::Triple Triple(
Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));
if (Triple.isOSWindows())
return createStringError(
inconvertibleErrorCode(),
"Relocatable linking is not supported on COFF targets");

Expected<std::string> ObjcopyPath =
findProgram("llvm-objcopy", {getMainExecutable("llvm-objcopy")});
if (!ObjcopyPath)
return ObjcopyPath.takeError();

// Use the linker output file to get a unique hash. This creates a unique
// identifier to rename the sections to that is deterministic to the contents.
auto BufferOrErr = DryRun ? MemoryBuffer::getMemBuffer("")
: MemoryBuffer::getFileOrSTDIN(Output);
if (!BufferOrErr)
return createStringError(inconvertibleErrorCode(), "Failed to open %s",
Output.str().c_str());
std::string Suffix = "_" + getHash((*BufferOrErr)->getBuffer());

SmallVector<StringRef> ObjcopyArgs = {
*ObjcopyPath,
Output,
};

// Remove the old .llvm.offloading section to prevent further linking.
ObjcopyArgs.emplace_back("--remove-section");
ObjcopyArgs.emplace_back(".llvm.offloading");
for (StringRef Prefix : {"omp", "cuda", "hip"}) {
auto Section = (Prefix + "_offloading_entries").str();
// Rename the offloading entires to make them private to this link unit.
ObjcopyArgs.emplace_back("--rename-section");
ObjcopyArgs.emplace_back(
Args.MakeArgString(Section + "=" + Section + Suffix));

// Rename the __start_ / __stop_ symbols appropriately to iterate over the
// newly renamed section containing the offloading entries.
ObjcopyArgs.emplace_back("--redefine-sym");
ObjcopyArgs.emplace_back(Args.MakeArgString("__start_" + Section + "=" +
"__start_" + Section + Suffix));
ObjcopyArgs.emplace_back("--redefine-sym");
ObjcopyArgs.emplace_back(Args.MakeArgString("__stop_" + Section + "=" +
"__stop_" + Section + Suffix));
}

if (Error Err = executeCommands(*ObjcopyPath, ObjcopyArgs))
return Err;

return Error::success();
}

/// Runs the wrapped linker job with the newly created input.
Error runLinker(ArrayRef<StringRef> Files, const ArgList &Args) {
llvm::TimeTraceScope TimeScope("Execute host linker");
Expand All @@ -265,6 +329,11 @@ Error runLinker(ArrayRef<StringRef> Files, const ArgList &Args) {
LinkerArgs.push_back(Arg);
if (Error Err = executeCommands(LinkerPath, LinkerArgs))
return Err;

if (Args.hasArg(OPT_relocatable))
if (Error Err = relocateOffloadSection(Args, ExecutableName))
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We could just return relocateOffloadSection(Args, ExecutableName)

return Err;

return Error::success();
}

Expand Down Expand Up @@ -910,7 +979,8 @@ wrapDeviceImages(ArrayRef<std::unique_ptr<MemoryBuffer>> Buffers,
case OFK_OpenMP:
if (Error Err = offloading::wrapOpenMPBinaries(
M, BuffersToWrap,
offloading::getOffloadEntryArray(M, "omp_offloading_entries")))
offloading::getOffloadEntryArray(M, "omp_offloading_entries"),
/*Suffix=*/"", /*Relocatable=*/Args.hasArg(OPT_relocatable)))
return std::move(Err);
break;
case OFK_Cuda:
Expand Down Expand Up @@ -1356,12 +1426,6 @@ Expected<SmallVector<SmallVector<OffloadFile>>>
getDeviceInput(const ArgList &Args) {
llvm::TimeTraceScope TimeScope("ExtractDeviceCode");

// If the user is requesting a reloctable link we ignore the device code. The
// actual linker will merge the embedded device code sections so they can be
// linked when the executable is finally created.
if (Args.hasArg(OPT_relocatable))
return SmallVector<SmallVector<OffloadFile>>{};

StringRef Root = Args.getLastArgValue(OPT_sysroot_EQ);
SmallVector<StringRef> LibraryPaths;
for (const opt::Arg *Arg : Args.filtered(OPT_library_path, OPT_libpath))
Expand Down
4 changes: 3 additions & 1 deletion llvm/include/llvm/Frontend/Offloading/OffloadWrapper.h
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Expand Up @@ -20,10 +20,12 @@ using EntryArrayTy = std::pair<GlobalVariable *, GlobalVariable *>;
/// \param EntryArray Optional pair pointing to the `__start` and `__stop`
/// symbols holding the `__tgt_offload_entry` array.
/// \param Suffix An optional suffix appended to the emitted symbols.
/// \param Relocatable Indicate if we need to change the offloading section.
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Nit: "Indicate whether the binary is a relocatable object" may work a bit better for describing intent. Current description seems to describe an implementation detail.

llvm::Error wrapOpenMPBinaries(llvm::Module &M,
llvm::ArrayRef<llvm::ArrayRef<char>> Images,
EntryArrayTy EntryArray,
llvm::StringRef Suffix = "");
llvm::StringRef Suffix = "",
bool Relocatable = false);

/// Wraps the input fatbinary image into the module \p M as global symbols and
/// registers the images with the CUDA runtime.
Expand Down
11 changes: 7 additions & 4 deletions llvm/lib/Frontend/Offloading/OffloadWrapper.cpp
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Expand Up @@ -112,7 +112,8 @@ PointerType *getBinDescPtrTy(Module &M) {
///
/// Global variable that represents BinDesc is returned.
GlobalVariable *createBinDesc(Module &M, ArrayRef<ArrayRef<char>> Bufs,
EntryArrayTy EntryArray, StringRef Suffix) {
EntryArrayTy EntryArray, StringRef Suffix,
bool Relocatable) {
LLVMContext &C = M.getContext();
auto [EntriesB, EntriesE] = EntryArray;

Expand All @@ -129,7 +130,8 @@ GlobalVariable *createBinDesc(Module &M, ArrayRef<ArrayRef<char>> Bufs,
GlobalVariable::InternalLinkage, Data,
".omp_offloading.device_image" + Suffix);
Image->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
Image->setSection(".llvm.offloading");
Image->setSection(Relocatable ? ".llvm.offloading.relocatable"
: ".llvm.offloading");
Image->setAlignment(Align(object::OffloadBinary::getAlignment()));

StringRef Binary(Buf.data(), Buf.size());
Expand Down Expand Up @@ -582,8 +584,9 @@ void createRegisterFatbinFunction(Module &M, GlobalVariable *FatbinDesc,

Error offloading::wrapOpenMPBinaries(Module &M, ArrayRef<ArrayRef<char>> Images,
EntryArrayTy EntryArray,
llvm::StringRef Suffix) {
GlobalVariable *Desc = createBinDesc(M, Images, EntryArray, Suffix);
llvm::StringRef Suffix, bool Relocatable) {
GlobalVariable *Desc =
createBinDesc(M, Images, EntryArray, Suffix, Relocatable);
if (!Desc)
return createStringError(inconvertibleErrorCode(),
"No binary descriptors created.");
Expand Down
2 changes: 1 addition & 1 deletion llvm/lib/Object/OffloadBinary.cpp
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Expand Up @@ -83,7 +83,7 @@ Error extractFromObject(const ObjectFile &Obj,
if (!NameOrErr)
return NameOrErr.takeError();

if (!NameOrErr->equals(".llvm.offloading"))
if (!NameOrErr->starts_with(".llvm.offloading"))
continue;
}

Expand Down