Re: [Qemu-devel] [PATCH v5 6/7] ppc: Implement bcdtrunc. instruction

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jan 10, 2017 at 12:10:13AM -0200, Jose Ricardo Ziviani wrote:
> bcdtrunc.: Decimal integer truncate. Given a BCD number in vrb and the
> number of bytes to truncate in vra, the return register will have vrb
> with such bits truncated.
> 
> Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
> ---
>  target/ppc/helper.h                 |  1 +
>  target/ppc/int_helper.c             | 37 +++++++++++++++++++++++++++++++++++++
>  target/ppc/translate/vmx-impl.inc.c |  5 +++++
>  target/ppc/translate/vmx-ops.inc.c  |  4 ++--
>  4 files changed, 45 insertions(+), 2 deletions(-)
> 
> diff --git a/target/ppc/helper.h b/target/ppc/helper.h
> index d1db462..db17917 100644
> --- a/target/ppc/helper.h
> +++ b/target/ppc/helper.h
> @@ -401,6 +401,7 @@ DEF_HELPER_3(bcdsetsgn, i32, avr, avr, i32)
>  DEF_HELPER_4(bcds, i32, avr, avr, avr, i32)
>  DEF_HELPER_4(bcdus, i32, avr, avr, avr, i32)
>  DEF_HELPER_4(bcdsr, i32, avr, avr, avr, i32)
> +DEF_HELPER_4(bcdtrunc, i32, avr, avr, avr, i32)
>  
>  DEF_HELPER_2(xsadddp, void, env, i32)
>  DEF_HELPER_2(xsaddqp, void, env, i32)
> diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
> index b184063..06b14d5 100644
> --- a/target/ppc/int_helper.c
> +++ b/target/ppc/int_helper.c
> @@ -3223,6 +3223,43 @@ uint32_t helper_bcdsr(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
>      return cr;
>  }
>  
> +uint32_t helper_bcdtrunc(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
> +{
> +    uint64_t mask;
> +    uint32_t ox_flag = 0;
> +#if defined(HOST_WORDS_BIGENDIAN)
> +    int i = a->s16[3] + 1;
> +#else
> +    int i = a->s16[4] + 1;
> +#endif
> +    ppc_avr_t ret = *b;
> +
> +    if (bcd_is_valid(b) == false) {
> +        return CRF_SO;
> +    }
> +
> +    if (i > 16 && i < 32) {
> +        if (ret.u64[HI_IDX] >> (i * 4 - 64)) {
> +            ox_flag = CRF_SO;
> +        }

You can simplify this by just checking ret.u64[HI_IDX] & ~mask before
you apply the mast.

> +
> +        mask = (uint64_t)-1 >> (128 - i * 4);
> +        ret.u64[HI_IDX] &= mask;
> +    } else if (i >= 0 && i <= 16) {
> +        if (ret.u64[HI_IDX] || (i < 16 && ret.u64[LO_IDX] >> (i * 4))) {
> +            ox_flag = CRF_SO;
> +        }
> +
> +        mask = (uint64_t)-1 >> (64 - i * 4);

Similarly here.

> +        ret.u64[LO_IDX] &= mask;
> +        ret.u64[HI_IDX] = 0;
> +    }
> +    bcd_put_digit(&ret, bcd_preferred_sgn(bcd_get_sgn(b), ps), 0);
> +    *r = ret;
> +
> +    return bcd_cmp_zero(&ret) | ox_flag;
> +}
> +
>  void helper_vsbox(ppc_avr_t *r, ppc_avr_t *a)
>  {
>      int i;
> diff --git a/target/ppc/translate/vmx-impl.inc.c b/target/ppc/translate/vmx-impl.inc.c
> index 451abb5..1683f42 100644
> --- a/target/ppc/translate/vmx-impl.inc.c
> +++ b/target/ppc/translate/vmx-impl.inc.c
> @@ -1019,6 +1019,7 @@ GEN_BCD(bcdcpsgn);
>  GEN_BCD(bcds);
>  GEN_BCD(bcdus);
>  GEN_BCD(bcdsr);
> +GEN_BCD(bcdtrunc);
>  
>  static void gen_xpnd04_1(DisasContext *ctx)
>  {
> @@ -1097,6 +1098,10 @@ GEN_VXFORM_DUAL(vsubudm, PPC2_ALTIVEC_207, PPC_NONE, \
>                  bcds, PPC_NONE, PPC2_ISA300)
>  GEN_VXFORM_DUAL(vsubuwm, PPC_ALTIVEC, PPC_NONE, \
>                  bcdus, PPC_NONE, PPC2_ISA300)
> +GEN_VXFORM_DUAL(vsubsbs, PPC_ALTIVEC, PPC_NONE, \
> +                bcdtrunc, PPC_NONE, PPC2_ISA300)
> +GEN_VXFORM_DUAL(vsubuqm, PPC2_ALTIVEC_207, PPC_NONE, \
> +                bcdtrunc, PPC_NONE, PPC2_ISA300)
>  
>  static void gen_vsbox(DisasContext *ctx)
>  {
> diff --git a/target/ppc/translate/vmx-ops.inc.c b/target/ppc/translate/vmx-ops.inc.c
> index fa9c996..e6167a4 100644
> --- a/target/ppc/translate/vmx-ops.inc.c
> +++ b/target/ppc/translate/vmx-ops.inc.c
> @@ -143,14 +143,14 @@ GEN_VXFORM(vaddsws, 0, 14),
>  GEN_VXFORM_DUAL(vsububs, bcdadd, 0, 24, PPC_ALTIVEC, PPC_NONE),
>  GEN_VXFORM_DUAL(vsubuhs, bcdsub, 0, 25, PPC_ALTIVEC, PPC_NONE),
>  GEN_VXFORM(vsubuws, 0, 26),
> -GEN_VXFORM(vsubsbs, 0, 28),
> +GEN_VXFORM_DUAL(vsubsbs, bcdtrunc, 0, 28, PPC_NONE, PPC2_ISA300),
>  GEN_VXFORM(vsubshs, 0, 29),
>  GEN_VXFORM_DUAL(vsubsws, xpnd04_2, 0, 30, PPC_ALTIVEC, PPC_NONE),
>  GEN_VXFORM_207(vadduqm, 0, 4),
>  GEN_VXFORM_207(vaddcuq, 0, 5),
>  GEN_VXFORM_DUAL(vaddeuqm, vaddecuq, 30, 0xFF, PPC_NONE, PPC2_ALTIVEC_207),
> -GEN_VXFORM_207(vsubuqm, 0, 20),
>  GEN_VXFORM_207(vsubcuq, 0, 21),
> +GEN_VXFORM_DUAL(vsubuqm, bcdtrunc, 0, 20, PPC2_ALTIVEC_207, PPC2_ISA300),
>  GEN_VXFORM_DUAL(vsubeuqm, vsubecuq, 31, 0xFF, PPC_NONE, PPC2_ALTIVEC_207),
>  GEN_VXFORM(vrlb, 2, 0),
>  GEN_VXFORM(vrlh, 2, 1),

-- 
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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