Re: [PATCH 0/2] Floating-point OE/UE exception bug

[Daniel Henrique Barboza]

Queued in gitlab.com/danielhb/qemu/tree/ppc-next. Thanks,


Daniel

On 8/5/22 11:15, Lucas Mateus Castro(alqotel) wrote:
> From: "Lucas Mateus Castro (alqotel)" <lucas.araujo@eldorado.org.br>
>
> Changes in v2:
>      - Completely reworked the solution:
>          * Created re_bias in FloatFmt, it is 3/4 of the total exponent
>            range of a FP type
>          * Added rebias bools that dictates if the result should have
>            its exponent add/subtract the re_bias value if an
>            overflow/underflow occurs.
>          * ppc_store_fpscr sets/unsets rebias if OE/UE is set/unset
>
> The PowerISA defines that if an overflow exception happen with FPSCR.OE
> set, the exponent of the intermediate result is subtracted 1536 in
> double precision operations and is added 1536 in an underflow exception,
> currently this behavior is not QEMU's behavior, this patch series fixes
> that.
>
> Currently there's no test in this patch series as there's no way to
> disable MSR.FE0 and MSR.FE1 in linux user, so any overflow/underflow
> exception with OE/UE set causes a trapping exception.
>
> Lucas Mateus Castro (alqotel) (2):
>    fpu: Add rebias bool, value and operation
>    target/ppc: Bugfix FP when OE/UE are set
>
>   fpu/softfloat-parts.c.inc     | 21 +++++++++++++++++++--
>   fpu/softfloat.c               |  2 ++
>   include/fpu/softfloat-types.h |  4 ++++
>   target/ppc/cpu.c              |  2 ++
>   target/ppc/fpu_helper.c       |  2 --
>   5 files changed, 27 insertions(+), 4 deletions(-)