On Mon, Jul 16, 2018 at 07:03:12PM +0000, Yasmin Beatriz wrote: > When the result of bcdsub is equal to zero, the result sign may be > set to negative in some cases, and this does not follow the Power ISA > specifications as to decimal integer arithmetic instructions. > > Signed-off-by: Yasmin Beatriz <yasm...@linux.ibm.com>
The fix looks correct, but since this has been broken forever and we're in hard freeze I'm going to apply for 3.1, not 3.0. Fwiw, I think the surrounding logic can probably be simplified a little as well - I think this is now the only case with a zero result, so I think the 'zero' local can probably be removed. > --- > target/ppc/int_helper.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c > index 03d37da..fa18e6e 100644 > --- a/target/ppc/int_helper.c > +++ b/target/ppc/int_helper.c > @@ -2747,6 +2747,9 @@ uint32_t helper_bcdadd(ppc_avr_t *r, ppc_avr_t *a, > ppc_avr_t *b, uint32_t ps) > result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgna, ps); > zero = bcd_sub_mag(&result, a, b, &invalid, &overflow); > cr = (sgna > 0) ? CRF_GT : CRF_LT; > + } else if (bcd_cmp_mag(a, b) == 0) { > + result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(0, ps); > + zero = bcd_sub_mag(&result, b, a, &invalid, &overflow); > } else { > result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgnb, ps); > zero = bcd_sub_mag(&result, b, a, &invalid, &overflow); -- 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
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