[PATCH] [powerpc] Fix unrecognized instruction errors with recent binutils

[Paul E Murphy]

On 9/25/21 3:27 PM, Paul A. Clarke via Libc-alpha wrote:
> Recent versions of binutils (with commit
> b25f942e18d6ecd7ec3e2d2e9930eb4f996c258a) stopped preserving "sticky"
> options across a base `.machine` directive, nullifying the use of
> passing "-many" through GCC to the assembler.  As a result, some
> instructions which were recognized even under older, more stringent
> `.machine` directives become unrecognized instructions in that
> context.
> 
> In `sysdeps/powerpc/tst-set_ppr.c`, the use of the `mfppr32` extended
> mnemonic became unrecognized, as the default compilation with GCC for
> 32bit powerpc adds a `.machine ppc` in the resulting assembly, so the
> command line option `-Wa,-many` is essentially ignored, and the ISA 2.06
> instructions and mnemonics, like `mfppr32`, are unrecognized.
> 
> The compilation of `sysdeps/powerpc/tst-set_ppr.c` fails with:
> Error: unrecognized opcode: `mfppr32'
> 
> Add appropriate `.machine` directives in the assembly to bracket the
> `mfppr32` instruction.
> 
> Part of a 2019 fix (commit 9250e6610fdb0f3a6f238d2813e319a41fb7a810) to
> the above test's Makefile to add `-many` to the compilation when GCC
> itself stopped passing `-many` to the assember no longer has any effect,
> so remove that.
> 
> Reported-by: Joseph Myers <joseph@codesourcery.com>
> ---
>   sysdeps/powerpc/Makefile      | 5 -----
>   sysdeps/powerpc/tst-set_ppr.c | 3 ++-
>   2 files changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/sysdeps/powerpc/Makefile b/sysdeps/powerpc/Makefile
> index 09860ffc0155..5e6cb07ce66d 100644
> --- a/sysdeps/powerpc/Makefile
> +++ b/sysdeps/powerpc/Makefile
> @@ -61,11 +61,6 @@ ifeq ($(subdir),misc)
>   sysdep_headers += sys/platform/ppc.h
>   tests += test-gettimebase
>   tests += tst-set_ppr
> -
> -# This test is expected to run and exit with EXIT_UNSUPPORTED on
> -# processors that do not implement the Power ISA 2.06 or greater.
> -# But the test makes use of instructions from Power ISA 2.06 and 2.07.
> -CFLAGS-tst-set_ppr.c += -Wa,-many
>   endif
> 
>   ifeq ($(subdir),wcsmbs)

OK.

> diff --git a/sysdeps/powerpc/tst-set_ppr.c b/sysdeps/powerpc/tst-set_ppr.c
> index 7684f5d6ea90..e80da1532063 100644
> --- a/sysdeps/powerpc/tst-set_ppr.c
> +++ b/sysdeps/powerpc/tst-set_ppr.c
> @@ -44,7 +44,8 @@ get_thread_priority (void)
>   {
>     /* Read the PPR.  */
>     ppr_t ppr;
> -  asm volatile (MFPPR" %0" : "=r"(ppr));
> +  asm volatile (".machine push; .machine power7; "MFPPR" %0; .machine pop"

Does it matter if power7 is quoted? LGTM to me otherwise.