[clang] 080022d - [LinkerWrapper] Embed OffloadBinaries for OpenMP offloading images

[Joseph Huber via cfe-commits]

Author: Joseph Huber
Date: 2022-07-21T13:20:01-04:00
New Revision: 080022d8ed6c1bd9ba5ece33cfea248f9473e775

URL: https://github.com/llvm/llvm-project/commit/080022d8ed6c1bd9ba5ece33cfea248f9473e775
DIFF: https://github.com/llvm/llvm-project/commit/080022d8ed6c1bd9ba5ece33cfea248f9473e775.diff

LOG: [LinkerWrapper] Embed OffloadBinaries for OpenMP offloading images

The OpenMP offloading runtine currently uses an array of linked
offloading images. One downside to this is that we cannot know the
architecture or triple associated with the given image. In this patch,
instead of embedding the image itself, we embed an offloading binary
instead. This binary is simply a binary format that wraps around the
original linked image to provide some additional metadata. This will
allow us to support offloading to multiple architecture, or performing
future JIT compilation inside of the runtime, more clearly.
Additionally, these can be placed at a special section such that the
supported architectures can be identified using objdump with the support
from D126904. This needs to be stored in a new section name
`.llvm.offloading.images` because the `.llvm.offloading` section
implicitly uses the `SHF_EXCLUDE` flag and will always be stripped.

This patch does not contain the necessary code to parse these in
libomptarget.

Depends on D127246

Reviewed By: saiislam

Differential Revision: https://reviews.llvm.org/D127304

Added: 
    

Modified: 
    clang/test/Driver/linker-wrapper-image.c
    clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
    clang/tools/clang-linker-wrapper/OffloadWrapper.cpp

Removed: 
    


################################################################################
diff  --git a/clang/test/Driver/linker-wrapper-image.c b/clang/test/Driver/linker-wrapper-image.c
index c1d29b66209d1..a54ba4d19122f 100644
--- a/clang/test/Driver/linker-wrapper-image.c
+++ b/clang/test/Driver/linker-wrapper-image.c
@@ -11,8 +11,8 @@
 //      OPENMP: @__start_omp_offloading_entries = external hidden constant %__tgt_offload_entry
 // OPENMP-NEXT: @__stop_omp_offloading_entries = external hidden constant %__tgt_offload_entry
 // OPENMP-NEXT: @__dummy.omp_offloading.entry = hidden constant [0 x %__tgt_offload_entry] zeroinitializer, section "omp_offloading_entries"
-// OPENMP-NEXT: @.omp_offloading.device_image = internal unnamed_addr constant [0 x i8] zeroinitializer
-// OPENMP-NEXT: @.omp_offloading.device_images = internal unnamed_addr constant [1 x %__tgt_device_image] [%__tgt_device_image { ptr @.omp_offloading.device_image, ptr @.omp_offloading.device_image, ptr @__start_omp_offloading_entries, ptr @__stop_omp_offloading_entries }]
+// OPENMP-NEXT: @.omp_offloading.device_image = internal unnamed_addr constant [[[SIZE:[0-9]+]] x i8] c"\10\FF\10\AD{{.*}}"
+// OPENMP-NEXT: @.omp_offloading.device_images = internal unnamed_addr constant [1 x %__tgt_device_image] [%__tgt_device_image { ptr @.omp_offloading.device_image, ptr getelementptr inbounds ([[[SIZE]] 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 }
 // OPENMP-NEXT: @llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 1, ptr @.omp_offloading.descriptor_reg, ptr null }]
 // OPENMP-NEXT: @llvm.global_dtors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 1, ptr @.omp_offloading.descriptor_unreg, ptr null }]

diff  --git a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
index 8e69cd93efdfe..44b55c6a45e15 100644
--- a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
+++ b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
@@ -1172,8 +1172,7 @@ Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
 bundleOpenMP(ArrayRef<OffloadingImage> Images) {
   SmallVector<std::unique_ptr<MemoryBuffer>> Buffers;
   for (const OffloadingImage &Image : Images)
-    Buffers.emplace_back(
-        MemoryBuffer::getMemBufferCopy(Image.Image->getBuffer()));
+    Buffers.emplace_back(OffloadBinary::write(Image));
 
   return std::move(Buffers);
 }

diff  --git a/clang/tools/clang-linker-wrapper/OffloadWrapper.cpp b/clang/tools/clang-linker-wrapper/OffloadWrapper.cpp
index a5c4fc981cbdd..dbfd896362c76 100644
--- a/clang/tools/clang-linker-wrapper/OffloadWrapper.cpp
+++ b/clang/tools/clang-linker-wrapper/OffloadWrapper.cpp
@@ -14,6 +14,7 @@
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Object/OffloadBinary.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 
@@ -184,6 +185,8 @@ GlobalVariable *createBinDesc(Module &M, ArrayRef<ArrayRef<char>> Bufs) {
                                      GlobalVariable::InternalLinkage, Data,
                                      ".omp_offloading.device_image");
     Image->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
+    Image->setSection(".llvm.offloading");
+    Image->setAlignment(Align(object::OffloadBinary::getAlignment()));
 
     auto *Size = ConstantInt::get(getSizeTTy(M), Buf.size());
     Constant *ZeroSize[] = {Zero, Size};