[all-commits] [llvm/llvm-project] 0a23fb: clang: Always pass PowerPC endian information to G...

[Nathan Chancellor via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 0a23fbd28c7509f2f980946091e6055bf27164d2
      https://github.com/llvm/llvm-project/commit/0a23fbd28c7509f2f980946091e6055bf27164d2
  Author: Nathan Chancellor <natechancellor at gmail.com>
  Date:   2021-01-11 (Mon, 11 Jan 2021)

  Changed paths:
    M clang/lib/Driver/ToolChains/Gnu.cpp
    M clang/test/Driver/ppc-features.cpp

  Log Message:
  -----------
  clang: Always pass PowerPC endian information to GNU as

When building a 64-bit big endian PowerPC Linux kernel with a 64-bit
little endian PowerPC target, the 32-bit vDSO errors:

```
$ make ARCH=powerpc CC=clang CROSS_COMPILE=powerpc64le-linux-gnu- \
       pseries_defconfig arch/powerpc/kernel/vdso32/
ld.lld: error: arch/powerpc/kernel/vdso32/sigtramp.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/gettimeofday.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/datapage.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/cacheflush.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/note.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/getcpu.o is incompatible with elf32-powerpc
ld.lld: error: arch/powerpc/kernel/vdso32/vgettimeofday.o is incompatible with elf32-powerpc
...
```

This happens because the endian information is missing from the call to
the assembler, even though it was explicitly passed to clang. See the
below example.

```
$ echo | clang --target=powerpc64le-linux-gnu \
               --prefix=/usr/bin/powerpc64le-linux-gnu- \
               -no-integrated-as -m32 -mbig-endian -### -x c -c -
 ".../clang-12" "-cc1" "-triple" "powerpc-unknown-linux-gnu" ...
...
  "/usr/bin/powerpc64le-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "-.o" "/tmp/--e69e28.s"
```

clang sets the right target with -m32 and -mbig-endian but -mbig-endian
does not make it to the assembler, resulting in a 32-bit little endian
binary. This differs from the little endian targets, which always pass
-mlittle-endian.

```
$ echo | clang --target=powerpc64-linux-gnu \
               --prefix=/usr/bin/powerpc64-linux-gnu- \
               -no-integrated-as -m32 -mlittle-endian -### -x c -c -
 ".../clang-12" "-cc1" "-triple" "powerpcle-unknown-linux-gnu" ...
...
 "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-mlittle-endian" "-many" "-o" "-.o" "/tmp/--405dbd.s"
```

Do the same thing for the big endian targets so that there is no more
error. This matches GCC's behavior, where -mbig and -mlittle are always
passed along to GNU as.

```
$ echo | powerpc64-linux-gcc -### -x c -c -
...
.../powerpc64-linux/bin/as -a64 -mpower4 -many -mbig -o -.o /tmp/ccVn7NAm.s
...

$ echo | powerpc64le-linux-gcc -### -x c -c -
...
.../powerpc64le-linux/bin/as -a64 -mpower8 -many -mlittle -o -.o /tmp/ccPN9ato.s
...
```

Reviewed By: nickdesaulniers, MaskRay

Differential Revision: https://reviews.llvm.org/D94442