Re: [Qemu-devel] [PATCH v4 2/4] target-ppc: Implement bcdctn. instruction

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

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On Tue, Nov 01, 2016 at 01:24:46PM -0200, Jose Ricardo Ziviani wrote:
> bcdctn. converts from BCD to National numeric format. National format
> uses a byte to represent a digit where the most significant nibble is
> always 0x3 and the least sign. nibbles is the digit itself.
> 
> Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
> ---
>  target-ppc/helper.h                 |  1 +
>  target-ppc/int_helper.c             | 48 +++++++++++++++++++++++++++++++++++++
>  target-ppc/translate/vmx-impl.inc.c |  4 ++++
>  3 files changed, 53 insertions(+)
> 
> diff --git a/target-ppc/helper.h b/target-ppc/helper.h
> index 3b23eed..33286c6 100644
> --- a/target-ppc/helper.h
> +++ b/target-ppc/helper.h
> @@ -372,6 +372,7 @@ DEF_HELPER_4(vpermxor, void, avr, avr, avr, avr)
>  DEF_HELPER_4(bcdadd, i32, avr, avr, avr, i32)
>  DEF_HELPER_4(bcdsub, i32, avr, avr, avr, i32)
>  DEF_HELPER_3(bcdcfn, i32, avr, avr, i32)
> +DEF_HELPER_3(bcdctn, 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 605cfc7..3c21173 100644
> --- a/target-ppc/int_helper.c
> +++ b/target-ppc/int_helper.c
> @@ -2515,6 +2515,15 @@ static uint16_t get_national_digit(ppc_avr_t *reg, int n)
>  #endif
>  }
>  
> +static void set_national_digit(ppc_avr_t *reg, uint8_t val, int n)
> +{
> +#if defined(HOST_WORDS_BIGENDIAN)
> +    reg->u16[8 - n] = val;
> +#else
> +    reg->u16[n] = val;
> +#endif
> +}
> +
>  static int bcd_cmp_mag(ppc_avr_t *a, ppc_avr_t *b)
>  {
>      int i;
> @@ -2681,6 +2690,45 @@ uint32_t helper_bcdcfn(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
>      return cr;
>  }
>  
> +uint32_t helper_bcdctn(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
> +{
> +    int i;
> +    int cr = 0;
> +    int sgnb = bcd_get_sgn(b);
> +    int invalid = (sgnb == 0);
> +    ppc_avr_t ret = { .u64 = { 0, 0 } };
> +
> +    int eq_flag = (b->u64[HI_IDX] == 0) && ((b->u64[LO_IDX] >> 4) == 0);

You can simplify this, and several pieces below by using the
bcd_cmp_zero() function you introduced in the previous patch.

> +    int ox_flag = (b->u64[HI_IDX] != 0) || ((b->u64[LO_IDX] >> 32) != 0);
> +
> +    for (i = 1; i < 8; i++) {
> +        set_national_digit(&ret, 0x30 + bcd_get_digit(b, i, &invalid), i);
> +
> +        if (unlikely(invalid)) {
> +            break;
> +        }
> +    }
> +    set_national_digit(&ret, (sgnb == -1) ? NATIONAL_NEG : NATIONAL_PLUS, 0);
> +
> +    if (!eq_flag) {
> +        cr = (sgnb == -1) ? 1 << CRF_LT : 1 << CRF_GT;
> +    } else {
> +        cr = 1 << CRF_EQ;
> +    }
> +
> +    if (ox_flag) {
> +        cr |= 1 << CRF_SO;
> +    }
> +
> +    if (unlikely(invalid)) {
> +        cr = 1 << CRF_SO;
> +    }
> +
> +    *r = ret;
> +
> +    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 50abfaf..d5953a6 100644
> --- a/target-ppc/translate/vmx-impl.inc.c
> +++ b/target-ppc/translate/vmx-impl.inc.c
> @@ -971,10 +971,14 @@ static void gen_##op(DisasContext *ctx)             \
>  GEN_BCD(bcdadd)
>  GEN_BCD(bcdsub)
>  GEN_BCD2(bcdcfn)
> +GEN_BCD2(bcdctn)
>  
>  static void gen_xpnd04_1(DisasContext *ctx)
>  {
>      switch (opc4(ctx->opcode)) {
> +    case 5:
> +        gen_bcdctn(ctx);
> +        break;
>      case 7:
>          gen_bcdcfn(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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