Re: [Qemu-devel] [PATCH 2/4] target-ppc: Implement bcdctsq. instruction

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

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On Wed, Nov 16, 2016 at 06:07:28PM -0200, Jose Ricardo Ziviani wrote:
> bcdctsq.: Decimal convert to signed quadword. It is possible to
> convert packed decimal values to signed quadwords.
> 
> Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
> ---
>  target-ppc/helper.h                 |  1 +
>  target-ppc/int_helper.c             | 39 +++++++++++++++++++++++++++++++++++++
>  target-ppc/translate/vmx-impl.inc.c |  7 +++++++
>  3 files changed, 47 insertions(+)
> 
> diff --git a/target-ppc/helper.h b/target-ppc/helper.h
> index 87f533c..503f257 100644
> --- a/target-ppc/helper.h
> +++ b/target-ppc/helper.h
> @@ -383,6 +383,7 @@ DEF_HELPER_3(bcdctn, i32, avr, avr, i32)
>  DEF_HELPER_3(bcdcfz, i32, avr, avr, i32)
>  DEF_HELPER_3(bcdctz, i32, avr, avr, i32)
>  DEF_HELPER_3(bcdcfsq, i32, avr, avr, i32)
> +DEF_HELPER_3(bcdctsq, i32, avr, avr, i32)
>  
>  DEF_HELPER_2(xsadddp, void, env, i32)
>  DEF_HELPER_2(xssubdp, void, env, i32)
> diff --git a/target-ppc/int_helper.c b/target-ppc/int_helper.c
> index db65a51..1025438 100644
> --- a/target-ppc/int_helper.c
> +++ b/target-ppc/int_helper.c
> @@ -2922,6 +2922,45 @@ uint32_t helper_bcdcfsq(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
>      return cr;
>  }
>  
> +uint32_t helper_bcdctsq(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
> +{
> +    uint8_t i;
> +    int cr = 0;
> +    uint64_t hi = 0;
> +    int sgnb = bcd_get_sgn(b);
> +    int invalid = (sgnb == 0);
> +    ppc_avr_t ret = { .u64 = { 0, 0 } };
> +
> +    ret.u64[LO_IDX] = bcd_get_digit(b, 31, &invalid);
> +    for (i = 30; i > 0; i--) {
> +        mulu64(&ret.u64[LO_IDX], &hi,
> +                ret.u64[LO_IDX], 10ULL);
> +
> +        ret.u64[HI_IDX] = (ret.u64[HI_IDX]) ? ret.u64[HI_IDX] * 10 + hi : hi;
> +        ret.u64[LO_IDX] += bcd_get_digit(b, i, &invalid);

Again, it might be simpler to use the int128 code we already have in qemu.

> +        if (unlikely(invalid)) {
> +            break;
> +        }
> +    }
> +
> +    if (sgnb == -1) {
> +        if (ret.s64[HI_IDX] > 0) {
> +            ret.s64[HI_IDX] = -ret.s64[HI_IDX];
> +        } else {
> +            ret.s64[LO_IDX] = -ret.s64[LO_IDX];
> +        }

As on the other direction, I don't think this looks like a correct
128-bit negate.

> +    }
> +
> +    cr = bcd_cmp_zero(b);
> +
> +    if (unlikely(invalid)) {
> +        cr = 1 << CRF_SO;
> +    }
> +
> +    return cr;
> +}
> +
>  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 36141e5..1579b58 100644
> --- a/target-ppc/translate/vmx-impl.inc.c
> +++ b/target-ppc/translate/vmx-impl.inc.c
> @@ -990,10 +990,14 @@ GEN_BCD2(bcdctn)
>  GEN_BCD2(bcdcfz)
>  GEN_BCD2(bcdctz)
>  GEN_BCD2(bcdcfsq)
> +GEN_BCD2(bcdctsq)
>  
>  static void gen_xpnd04_1(DisasContext *ctx)
>  {
>      switch (opc4(ctx->opcode)) {
> +    case 0:
> +        gen_bcdctsq(ctx);
> +        break;
>      case 2:
>          gen_bcdcfsq(ctx);
>          break;
> @@ -1018,6 +1022,9 @@ static void gen_xpnd04_1(DisasContext *ctx)
>  static void gen_xpnd04_2(DisasContext *ctx)
>  {
>      switch (opc4(ctx->opcode)) {
> +    case 0:
> +        gen_bcdctsq(ctx);
> +        break;
>      case 2:
>          gen_bcdcfsq(ctx);
>          break;

-- 
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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