[clang-offload-bundler] Add sections and set section flags using one llvm-objcopy invocation

[sdmitriev]

Summary

llvm-objcopy has been changed to support adding a section and updating section flags
in one run (D90438), so we can now change clang-offload-bundler to run llvm-objcopy
tool only once when creating fat object.

[ABataev]

LG

clang/test/Driver/clang-offload-bundler.c

 // section (we are using a PowerPC little-endian host which uses ELF). We
 // have an already bundled file to check the unbundle and do a dry run on the
 // bundling as it cannot be tested in all host platforms that will run these
 // tests.
 //
 
 // RUN: clang-offload-bundler -type=o -targets=host-%itanium_abi_triple,openmp-powerpc64le-ibm-linux-gnu,openmp-x86_64-pc-linux-gnu -inputs=%t.o,%t.tgt1,%t.tgt2 -outputs=%t.bundle3.o -### 2>&1 \
 // RUN: | FileCheck %s -DHOST=%itanium_abi_triple -DINOBJ1=%t.o -DINOBJ2=%t.tgt1 -DINOBJ3=%t.tgt2 -DOUTOBJ=%t.bundle3.o --check-prefix CK-OBJ-CMD
-// CK-OBJ-CMD: llvm-objcopy{{(.exe)?}}" "--add-section=__CLANG_OFFLOAD_BUNDLE__host-[[HOST]]={{.*}}" "--add-section=__CLANG_OFFLOAD_BUNDLE__openmp-powerpc64le-ibm-linux-gnu=[[INOBJ2]]" "--add-section=__CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu=[[INOBJ3]]" "[[INOBJ1]]" "[[TEMPOBJ:.*]]"
-// CK-OBJ-CMD: llvm-objcopy{{(.exe)?}}" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__host-[[HOST]]=readonly,exclude" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__openmp-powerpc64le-ibm-linux-gnu=readonly,exclude" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu=readonly,exclude" "[[TEMPOBJ]]" "[[OUTOBJ]]"
+// CK-OBJ-CMD: llvm-objcopy{{(.exe)?}}" "--add-section=__CLANG_OFFLOAD_BUNDLE__host-[[HOST]]={{.*}}" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__host-[[HOST]]=readonly,exclude" "--add-section=__CLANG_OFFLOAD_BUNDLE__openmp-powerpc64le-ibm-linux-gnu=[[INOBJ2]]" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__openmp-powerpc64le-ibm-linux-gnu=readonly,exclude" "--add-section=__CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu=[[INOBJ3]]" "--set-section-flags=__CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu=readonly,exclude" "[[INOBJ1]]" "[[OUTOBJ]]"
 
 // RUN: clang-offload-bundler -type=o -targets=host-%itanium_abi_triple,openmp-powerpc64le-ibm-linux-gnu,openmp-x86_64-pc-linux-gnu -inputs=%t.o,%t.tgt1,%t.tgt2 -outputs=%t.bundle3.o
 // RUN: clang-offload-bundler -type=o -inputs=%t.bundle3.o -list | FileCheck -check-prefix=CKLST %s
 // RUN: clang-offload-bundler -type=o -targets=host-%itanium_abi_triple,openmp-powerpc64le-ibm-linux-gnu,openmp-x86_64-pc-linux-gnu -outputs=%t.res.o,%t.res.tgt1,%t.res.tgt2 -inputs=%t.bundle3.o -unbundle
 // RUN: diff %t.bundle3.o %t.res.o
 // RUN: diff %t.tgt1 %t.res.tgt1
 // RUN: diff %t.tgt2 %t.res.tgt2
 // RUN: clang-offload-bundler -type=o -targets=openmp-powerpc64le-ibm-linux-gnu,host-%itanium_abi_triple,openmp-x86_64-pc-linux-gnu -outputs=%t.res.tgt1,%t.res.o,%t.res.tgt2 -inputs=%t.bundle3.o -unbundle

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

Error WriteBundleEnd(raw_fd_ostream &OS, StringRef TargetTriple) final {
 
     // If this is not the last output, we don't have to do anything.
     if (NumberOfProcessedInputs != NumberOfInputs)
       return Error::success();
 
     // We will use llvm-objcopy to add target objects sections to the output
     // fat object. These sections should have 'exclude' flag set which tells
     // link editor to remove them from linker inputs when linking executable or
-    // shared library. llvm-objcopy currently does not support adding new
-    // section and changing flags for the added section in one invocation, and
-    // because of that we have to run it two times. First run adds sections and
-    // the second changes flags.
-    // TODO: change it to one run once llvm-objcopy starts supporting that.
+    // shared library.
 
     // Find llvm-objcopy in order to create the bundle binary.
     ErrorOr<std::string> Objcopy = sys::findProgramByName(
         "llvm-objcopy", sys::path::parent_path(BundlerExecutable));
     if (!Objcopy)
       Objcopy = sys::findProgramByName("llvm-objcopy");
     if (!Objcopy)
       return createStringError(Objcopy.getError(),
                                "unable to find 'llvm-objcopy' in path");
 
     // We write to the output file directly. So, we close it and use the name
     // to pass down to llvm-objcopy.
     OS.close();
 
     // Temporary files that need to be removed.
     TempFileHandlerRAII TempFiles;
 
-    // Create an intermediate temporary file to save object after the first
-    // llvm-objcopy run.
-    Expected<StringRef> IntermediateObjOrErr = TempFiles.Create(None);
-    if (!IntermediateObjOrErr)
-      return IntermediateObjOrErr.takeError();
-    StringRef IntermediateObj = *IntermediateObjOrErr;
-
-    // Compose llvm-objcopy command line for add target objects' sections.
+    // Compose llvm-objcopy command line for add target objects' sections with
+    // appropriate flags.
     BumpPtrAllocator Alloc;
     StringSaver SS{Alloc};
     SmallVector<StringRef, 8u> ObjcopyArgs{"llvm-objcopy"};
     for (unsigned I = 0; I < NumberOfInputs; ++I) {
       StringRef InputFile = InputFileNames[I];
       if (I == HostInputIndex) {
         // Special handling for the host bundle. We do not need to add a
         // standard bundle for the host object since we are going to use fat
         // object as a host object. Therefore use dummy contents (one zero byte)
         // when creating section for the host bundle.
         Expected<StringRef> TempFileOrErr = TempFiles.Create(ArrayRef<char>(0));
         if (!TempFileOrErr)
           return TempFileOrErr.takeError();
         InputFile = *TempFileOrErr;
       }
 
       ObjcopyArgs.push_back(SS.save(Twine("--add-section=") +
                                     OFFLOAD_BUNDLER_MAGIC_STR + TargetNames[I] +
                                     "=" + InputFile));
-    }
-    ObjcopyArgs.push_back(InputFileNames[HostInputIndex]);
-    ObjcopyArgs.push_back(IntermediateObj);
-
-    if (Error Err = executeObjcopy(*Objcopy, ObjcopyArgs))
-      return Err;
-
-    // And run llvm-objcopy for the second time to update section flags.
-    ObjcopyArgs.resize(1);
-    for (unsigned I = 0; I < NumberOfInputs; ++I)
       ObjcopyArgs.push_back(SS.save(Twine("--set-section-flags=") +
                                     OFFLOAD_BUNDLER_MAGIC_STR + TargetNames[I] +
                                     "=readonly,exclude"));
-    ObjcopyArgs.push_back(IntermediateObj);
+    }
+    ObjcopyArgs.push_back(InputFileNames[HostInputIndex]);
     ObjcopyArgs.push_back(OutputFileNames.front());
 
     if (Error Err = executeObjcopy(*Objcopy, ObjcopyArgs))
       return Err;
 
     return Error::success();
   }