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

[David Gibson]

On Thu, Nov 01, 2018 at 06:54:59PM +0100, Laurent Vivier wrote:
> 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.

We already have ISA version flags in insns_flags & insns_flags2, so
I'm hoping we can use those rather than introduce a new bool.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature