Re: [Qemu-devel] [PATCH] softfloat: don't execute ppc64 ISA 3.0B instruction if it is not supported

[Laurent Vivier]

On 01/11/2018 18:49, Peter Maydell wrote:
> On 1 November 2018 at 17:38, Laurent Vivier <address@hidden> wrote:
>> commit 27ae5109a2 has introduced an assembly instruction only supported
>> by ISA 3.0B and it fails to execute on previous versions of the POWER
>> CPU (like PowerPC G5).
>>
>> This patch fixes that by checking the ISA level, and falls back to
>> the default C function if the instruction is not supported.
>>
>> Fixes: 27ae5109a2ba8b6b679cce3e03e16570a34390a0
>>        (softfloat: Specialize udiv_qrnnd for ppc64)
>> Signed-off-by: Laurent Vivier <address@hidden>
>> ---
>>  include/fpu/softfloat-macros.h | 39 ++++++++++++++++++++--------------
>>  1 file changed, 23 insertions(+), 16 deletions(-)
>>
>> diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
>> index c86687fa5e..fe98b33df9 100644
>> --- a/include/fpu/softfloat-macros.h
>> +++ b/include/fpu/softfloat-macros.h
>> @@ -78,6 +78,9 @@ this code that are retained.
>>  /* Portions of this work are licensed under the terms of the GNU GPL,
>>   * version 2 or later. See the COPYING file in the top-level directory.
>>   */
>> +#if defined(_ARCH_PPC64)
>> +extern bool have_isa_3_00;
>> +#endif
> 
> I was wondering where this bool came from. The answer is
> that it's defined in tcg/ppc/tcg-target.inc.c. It's ok to
> use it here because fpu/softfloat.c is only compiled if
> CONFIG_TCG is true, so the tcg code will be present. The
> other user of this include file is target/m68k/softfloat.c,
> which also will only be compiled for a ppc host if CONFIG_TCG.
> 
> It's a little awkward to be borrowing this tcg/ppc internal
> flag into the softfloat code, though.

I agree, I was hopping Richard can advice another way to do that.

Thanks,
Laurent