[PATCH] D66485: [Clang][Bundler] Use llvm-objcopy for creating fat object files

[Sergey Dmitriev via Phabricator via cfe-commits]

sdmitriev marked an inline comment as done.
sdmitriev added inline comments.


================
Comment at: clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp:485
+                                    "=" + InputFileNames[I]));
+    ObjcopyArgs.push_back(InputFileNames[HostInputIndex]);
+    ObjcopyArgs.push_back(OutputFileNames.front());
----------------
ABataev wrote:
> As I understand, the resulting object file has the same structure as before? And we still can get an access to the host object file using standard programs, like readelf, objdump, etc.?
Yes, the structure is the same. The only difference is in the section flags that contain device objects - such sections used to have ALLOC attribute, but they do not have it now which I believe is a good think.

That is what we had earlier:

```
bash-4.2$ cat y.c
#pragma omp declare target
void foo() {}
#pragma omp end declare target
bash-4.2$ clang -fopenmp -fopenmp-targets=x86_64-pc-linux-gnu -c y.c
bash-4.2$ objdump -h y.o 

y.o:     file format elf64-x86-64

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         00000008  0000000000000000  0000000000000000  00000040  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text.startup 00000010  0000000000000000  0000000000000000  00000050  2**4
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  2 __CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu 000003f8  0000000000000000  0000000000000000  00000060  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 __CLANG_OFFLOAD_BUNDLE__host-x86_64-unknown-linux-gnu 00000630  0000000000000000  0000000000000000  00000460  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .eh_frame     00000058  0000000000000000  0000000000000000  00000a90  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  5 .init_array.0 00000008  0000000000000000  0000000000000000  00000ae8  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
  6 .comment      0000006a  0000000000000000  0000000000000000  00000af0  2**0
                  CONTENTS, READONLY
  7 .note.GNU-stack 00000000  0000000000000000  0000000000000000  00000b5a  2**0
                  CONTENTS, READONLY
  8 .llvm_addrsig 00000002  0000000000000000  0000000000000000  00000b5a  2**0
                  CONTENTS, READONLY, EXCLUDE
bash-4.2$ 
```

And here is what we have with this patch:

```
bash-4.2$ clang -fopenmp -fopenmp-targets=x86_64-pc-linux-gnu -c y.c
bash-4.2$ objdump -h y.o 

y.o:     file format elf64-x86-64

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         00000006  0000000000000000  0000000000000000  00000040  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text.startup 00000010  0000000000000000  0000000000000000  00000050  2**4
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  2 .init_array.0 00000008  0000000000000000  0000000000000000  00000060  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
  3 .comment      0000006a  0000000000000000  0000000000000000  00000068  2**0
                  CONTENTS, READONLY
  4 .note.GNU-stack 00000000  0000000000000000  0000000000000000  000000d2  2**0
                  CONTENTS, READONLY
  5 .eh_frame     00000058  0000000000000000  0000000000000000  000000d8  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  6 .llvm_addrsig 00000002  0000000000000000  0000000000000000  00000238  2**0
                  CONTENTS, READONLY, EXCLUDE
  7 __CLANG_OFFLOAD_BUNDLE__openmp-x86_64-pc-linux-gnu 000003f8  0000000000000000  0000000000000000  00000353  2**0
                  CONTENTS, READONLY
  8 __CLANG_OFFLOAD_BUNDLE__host-x86_64-unknown-linux-gnu 00000630  0000000000000000  0000000000000000  0000074b  2**0
                  CONTENTS, READONLY
bash-4.2$ 
```



Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D66485/new/

https://reviews.llvm.org/D66485