Re: [Qemu-devel] [PATCH 10/14] i386: use inverted setcond when computing NS or NZ

[Blue Swirl]

On Sat, Oct 6, 2012 at 12:30 PM, Paolo Bonzini <address@hidden> wrote:
> Make gen_compute_eflags_z and gen_compute_eflags_s able to compute the
> inverted condition, and use this in gen_setcc_slow_T0.  We cannot do it
> yet in gen_compute_eflags_c, but prepare the code for it anyway.  It is
> not worthwhile for PF, as usual.
>
> shr+and+xor could be replaced by and+setcond.  I'm not doing it yet.
>
> Signed-off-by: Paolo Bonzini <address@hidden>

Reviewed-by: Blue Swirl <address@hidden>

> ---
>  target-i386/translate.c | 51 
> +++++++++++++++++++++++++++++--------------------
>  1 file modificato, 30 inserzioni(+), 21 rimozioni(-)
>
> diff --git a/target-i386/translate.c b/target-i386/translate.c
> index daa36c1..abcd944 100644
> --- a/target-i386/translate.c
> +++ b/target-i386/translate.c
> @@ -824,13 +824,16 @@ static void gen_op_update_neg_cc(void)
>  }
>
>  /* compute eflags.C to reg */
> -static void gen_compute_eflags_c(DisasContext *s, TCGv reg)
> +static void gen_compute_eflags_c(DisasContext *s, TCGv reg, bool inv)
>  {
>      if (s->cc_op != CC_OP_DYNAMIC) {
>          gen_op_set_cc_op(s->cc_op);
>      }
>      gen_helper_cc_compute_c(cpu_tmp2_i32, cpu_env, cpu_cc_op);
>      tcg_gen_extu_i32_tl(reg, cpu_tmp2_i32);
> +    if (inv) {
> +        tcg_gen_xori_tl(reg, reg, 1);
> +    }
>  }
>
>  /* compute all eflags to cc_src */
> @@ -857,7 +860,7 @@ static void gen_compute_eflags_p(DisasContext *s, TCGv 
> reg)
>  }
>
>  /* compute eflags.S to reg */
> -static void gen_compute_eflags_s(DisasContext *s, TCGv reg)
> +static void gen_compute_eflags_s(DisasContext *s, TCGv reg, bool inv)
>  {
>      if (s->cc_op == CC_OP_DYNAMIC) {
>          gen_compute_eflags(s);
> @@ -865,10 +868,13 @@ static void gen_compute_eflags_s(DisasContext *s, TCGv 
> reg)
>      if (s->cc_op == CC_OP_EFLAGS) {
>          tcg_gen_shri_tl(reg, cpu_cc_src, 7);
>          tcg_gen_andi_tl(reg, reg, 1);
> +        if (inv) {
> +            tcg_gen_xori_tl(reg, reg, 1);
> +        }
>      } else {
>          int size = (s->cc_op - CC_OP_ADDB) & 3;
>          gen_ext_tl(reg, cpu_cc_dst, size, true);
> -        tcg_gen_setcondi_tl(TCG_COND_LT, reg, reg, 0);
> +        tcg_gen_setcondi_tl(inv ? TCG_COND_GE : TCG_COND_LT, reg, reg, 0);
>      }
>  }
>
> @@ -881,7 +887,7 @@ static void gen_compute_eflags_o(DisasContext *s, TCGv 
> reg)
>  }
>
>  /* compute eflags.Z to reg */
> -static void gen_compute_eflags_z(DisasContext *s, TCGv reg)
> +static void gen_compute_eflags_z(DisasContext *s, TCGv reg, bool inv)
>  {
>      if (s->cc_op == CC_OP_DYNAMIC) {
>          gen_compute_eflags(s);
> @@ -889,25 +895,28 @@ static void gen_compute_eflags_z(DisasContext *s, TCGv 
> reg)
>      if (s->cc_op == CC_OP_EFLAGS) {
>          tcg_gen_shri_tl(reg, cpu_cc_src, 6);
>          tcg_gen_andi_tl(reg, reg, 1);
> +        if (inv) {
> +            tcg_gen_xori_tl(reg, reg, 1);
> +        }
>      } else {
>          int size = (s->cc_op - CC_OP_ADDB) & 3;
>          gen_ext_tl(reg, cpu_cc_dst, size, false);
> -        tcg_gen_setcondi_tl(TCG_COND_EQ, reg, cpu_cc_dst, 0);
> +        tcg_gen_setcondi_tl(inv ? TCG_COND_NE : TCG_COND_EQ, reg, 
> cpu_cc_dst, 0);
>      }
>  }
>
> -static inline void gen_setcc_slow_T0(DisasContext *s, int jcc_op)
> +static inline void gen_setcc_slow_T0(DisasContext *s, int jcc_op, bool inv)
>  {
>      switch(jcc_op) {
>      case JCC_O:
>          gen_compute_eflags_o(s, cpu_T[0]);
>          break;
>      case JCC_B:
> -        gen_compute_eflags_c(s, cpu_T[0]);
> -        break;
> +        gen_compute_eflags_c(s, cpu_T[0], inv);
> +        return;
>      case JCC_Z:
> -        gen_compute_eflags_z(s, cpu_T[0]);
> -        break;
> +        gen_compute_eflags_z(s, cpu_T[0], inv);
> +        return;
>      case JCC_BE:
>          gen_compute_eflags(s);
>          tcg_gen_shri_tl(cpu_T[0], cpu_cc_src, 6);
> @@ -915,8 +924,8 @@ static inline void gen_setcc_slow_T0(DisasContext *s, int 
> jcc_op)
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], 1);
>          break;
>      case JCC_S:
> -        gen_compute_eflags_s(s, cpu_T[0]);
> -        break;
> +        gen_compute_eflags_s(s, cpu_T[0], inv);
> +        return;
>      case JCC_P:
>          gen_compute_eflags_p(s, cpu_T[0]);
>          break;
> @@ -938,6 +947,9 @@ static inline void gen_setcc_slow_T0(DisasContext *s, int 
> jcc_op)
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], 1);
>          break;
>      }
> +    if (inv) {
> +        tcg_gen_xori_tl(cpu_T[0], cpu_T[0], 1);
> +    }
>  }
>
>  /* return true if setcc_slow is not needed (WARNING: must be kept in
> @@ -1103,7 +1115,7 @@ static inline void gen_jcc1(DisasContext *s, int b, int 
> l1)
>          break;
>      default:
>      slow_jcc:
> -        gen_setcc_slow_T0(s, jcc_op);
> +        gen_setcc_slow_T0(s, jcc_op, false);
>          tcg_gen_brcondi_tl(inv ? TCG_COND_EQ : TCG_COND_NE,
>                             cpu_T[0], 0, l1);
>          break;
> @@ -1317,7 +1329,7 @@ static void gen_op(DisasContext *s1, int op, int ot, 
> int d)
>      }
>      switch(op) {
>      case OP_ADCL:
> -        gen_compute_eflags_c(s1, cpu_tmp4);
> +        gen_compute_eflags_c(s1, cpu_tmp4, false);
>          tcg_gen_add_tl(cpu_T[0], cpu_T[0], cpu_T[1]);
>          tcg_gen_add_tl(cpu_T[0], cpu_T[0], cpu_tmp4);
>          if (d != OR_TMP0)
> @@ -1332,7 +1344,7 @@ static void gen_op(DisasContext *s1, int op, int ot, 
> int d)
>          s1->cc_op = CC_OP_DYNAMIC;
>          break;
>      case OP_SBBL:
> -        gen_compute_eflags_c(s1, cpu_tmp4);
> +        gen_compute_eflags_c(s1, cpu_tmp4, false);
>          tcg_gen_sub_tl(cpu_T[0], cpu_T[0], cpu_T[1]);
>          tcg_gen_sub_tl(cpu_T[0], cpu_T[0], cpu_tmp4);
>          if (d != OR_TMP0)
> @@ -1406,7 +1418,7 @@ static void gen_inc(DisasContext *s1, int ot, int d, 
> int c)
>          gen_op_mov_TN_reg(ot, 0, d);
>      else
>          gen_op_ld_T0_A0(ot + s1->mem_index);
> -    gen_compute_eflags_c(s1, cpu_cc_src);
> +    gen_compute_eflags_c(s1, cpu_cc_src, false);
>      if (c > 0) {
>          tcg_gen_addi_tl(cpu_T[0], cpu_T[0], 1);
>          s1->cc_op = CC_OP_INCB + ot;
> @@ -2374,10 +2386,7 @@ static void gen_setcc(DisasContext *s, int b)
>             worth to */
>          inv = b & 1;
>          jcc_op = (b >> 1) & 7;
> -        gen_setcc_slow_T0(s, jcc_op);
> -        if (inv) {
> -            tcg_gen_xori_tl(cpu_T[0], cpu_T[0], 1);
> -        }
> +        gen_setcc_slow_T0(s, jcc_op, inv);
>      }
>  }
>
> @@ -6878,7 +6887,7 @@ static target_ulong disas_insn(DisasContext *s, 
> target_ulong pc_start)
>      case 0xd6: /* salc */
>          if (CODE64(s))
>              goto illegal_op;
> -        gen_compute_eflags_c(s, cpu_T[0]);
> +        gen_compute_eflags_c(s, cpu_T[0], false);
>          tcg_gen_neg_tl(cpu_T[0], cpu_T[0]);
>          gen_op_mov_reg_T0(OT_BYTE, R_EAX);
>          break;
> --
> 1.7.12.1
>
>
>