Re: [Qemu-devel] [PATCH 08/14] i386: do not compute eflags multiple times consecutively

[Blue Swirl]

On Sat, Oct 6, 2012 at 12:30 PM, Paolo Bonzini <address@hidden> wrote:
> After calling gen_compute_eflags, leave the computed value in cc_reg_src
> and set cc_op to CC_OP_EFLAGS.  The next few patches will remove anyway
> most calls to gen_compute_eflags.
>
> As a result of this change it is more natural to remove the register
> argument from gen_compute_eflags and change all the callers.
>
> Signed-off-by: Paolo Bonzini <address@hidden>

Reviewed-by: Blue Swirl <address@hidden>

> ---
>  target-i386/translate.c | 73 
> ++++++++++++++++++++++++-------------------------
>  1 file modificato, 36 inserzioni(+), 37 rimozioni(-)
>
> diff --git a/target-i386/translate.c b/target-i386/translate.c
> index 8f22119..09512c3 100644
> --- a/target-i386/translate.c
> +++ b/target-i386/translate.c
> @@ -834,48 +834,49 @@ static void gen_compute_eflags_c(DisasContext *s, TCGv 
> reg)
>  }
>
>  /* compute all eflags to cc_src */
> -static void gen_compute_eflags(DisasContext *s, TCGv reg)
> +static void gen_compute_eflags(DisasContext *s)
>  {
>      if (s->cc_op != CC_OP_DYNAMIC) {
>          gen_op_set_cc_op(s->cc_op);
>      }
> -    gen_helper_cc_compute_all(cpu_tmp2_i32, cpu_env, cpu_cc_op);
> -    if (reg == cpu_cc_src) {
> -        tcg_gen_discard_tl(cpu_cc_dst);
> -        s->cc_op = CC_OP_EFLAGS;
> +    if (s->cc_op == CC_OP_EFLAGS) {
> +        return;
>      }
> -    tcg_gen_extu_i32_tl(reg, cpu_tmp2_i32);
> +    gen_helper_cc_compute_all(cpu_tmp2_i32, cpu_env, cpu_cc_op);
> +    tcg_gen_discard_tl(cpu_cc_dst);
> +    s->cc_op = CC_OP_EFLAGS;
> +    tcg_gen_extu_i32_tl(cpu_cc_src, cpu_tmp2_i32);
>  }
>
>  /* compute eflags.P to reg */
>  static void gen_compute_eflags_p(DisasContext *s, TCGv reg)
>  {
> -    gen_compute_eflags(s, reg);
> -    tcg_gen_shri_tl(reg, reg, 2);
> +    gen_compute_eflags(s);
> +    tcg_gen_shri_tl(reg, cpu_cc_src, 2);
>      tcg_gen_andi_tl(reg, reg, 1);
>  }
>
>  /* compute eflags.S to reg */
>  static void gen_compute_eflags_s(DisasContext *s, TCGv reg)
>  {
> -    gen_compute_eflags(s, reg);
> -    tcg_gen_shri_tl(reg, reg, 7);
> +    gen_compute_eflags(s);
> +    tcg_gen_shri_tl(reg, cpu_cc_src, 7);
>      tcg_gen_andi_tl(reg, reg, 1);
>  }
>
>  /* compute eflags.O to reg */
>  static void gen_compute_eflags_o(DisasContext *s, TCGv reg)
>  {
> -    gen_compute_eflags(s, reg);
> -    tcg_gen_shri_tl(reg, reg, 11);
> +    gen_compute_eflags(s);
> +    tcg_gen_shri_tl(reg, cpu_cc_src, 11);
>      tcg_gen_andi_tl(reg, reg, 1);
>  }
>
>  /* compute eflags.Z to reg */
>  static void gen_compute_eflags_z(DisasContext *s, TCGv reg)
>  {
> -    gen_compute_eflags(s, reg);
> -    tcg_gen_shri_tl(reg, reg, 6);
> +    gen_compute_eflags(s);
> +    tcg_gen_shri_tl(reg, cpu_cc_src, 6);
>      tcg_gen_andi_tl(reg, reg, 1);
>  }
>
> @@ -892,9 +893,9 @@ static inline void gen_setcc_slow_T0(DisasContext *s, int 
> jcc_op)
>          gen_compute_eflags_z(s, cpu_T[0]);
>          break;
>      case JCC_BE:
> -        gen_compute_eflags(s, cpu_tmp0);
> -        tcg_gen_shri_tl(cpu_T[0], cpu_tmp0, 6);
> -        tcg_gen_or_tl(cpu_T[0], cpu_T[0], cpu_tmp0);
> +        gen_compute_eflags(s);
> +        tcg_gen_shri_tl(cpu_T[0], cpu_cc_src, 6);
> +        tcg_gen_or_tl(cpu_T[0], cpu_T[0], cpu_cc_src);
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], 1);
>          break;
>      case JCC_S:
> @@ -904,18 +905,18 @@ static inline void gen_setcc_slow_T0(DisasContext *s, 
> int jcc_op)
>          gen_compute_eflags_p(s, cpu_T[0]);
>          break;
>      case JCC_L:
> -        gen_compute_eflags(s, cpu_tmp0);
> -        tcg_gen_shri_tl(cpu_T[0], cpu_tmp0, 11); /* CC_O */
> -        tcg_gen_shri_tl(cpu_tmp0, cpu_tmp0, 7); /* CC_S */
> +        gen_compute_eflags(s);
> +        tcg_gen_shri_tl(cpu_T[0], cpu_cc_src, 11); /* CC_O */
> +        tcg_gen_shri_tl(cpu_tmp0, cpu_cc_src, 7); /* CC_S */
>          tcg_gen_xor_tl(cpu_T[0], cpu_T[0], cpu_tmp0);
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], 1);
>          break;
>      default:
>      case JCC_LE:
> -        gen_compute_eflags(s, cpu_tmp0);
> -        tcg_gen_shri_tl(cpu_T[0], cpu_tmp0, 11); /* CC_O */
> -        tcg_gen_shri_tl(cpu_tmp4, cpu_tmp0, 7); /* CC_S */
> -        tcg_gen_shri_tl(cpu_tmp0, cpu_tmp0, 6); /* CC_Z */
> +        gen_compute_eflags(s);
> +        tcg_gen_shri_tl(cpu_T[0], cpu_cc_src, 11); /* CC_O */
> +        tcg_gen_shri_tl(cpu_tmp4, cpu_cc_src, 7); /* CC_S */
> +        tcg_gen_shri_tl(cpu_tmp0, cpu_cc_src, 6); /* CC_Z */
>          tcg_gen_xor_tl(cpu_T[0], cpu_T[0], cpu_tmp4);
>          tcg_gen_or_tl(cpu_T[0], cpu_T[0], cpu_tmp0);
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], 1);
> @@ -1614,7 +1615,7 @@ static void gen_rot_rm_T1(DisasContext *s, int ot, int 
> op1,
>      }
>
>      /* update eflags.  It is needed anyway most of the time, do it always.  
> */
> -    gen_compute_eflags(s, cpu_cc_src);
> +    gen_compute_eflags(s);
>      assert(s->cc_op == CC_OP_EFLAGS);
>
>      label2 = gen_new_label();
> @@ -1691,7 +1692,7 @@ static void gen_rot_rm_im(DisasContext *s, int ot, int 
> op1, int op2,
>
>      if (op2 != 0) {
>          /* update eflags */
> -        gen_compute_eflags(s, cpu_cc_src);
> +        gen_compute_eflags(s);
>          assert(s->cc_op == CC_OP_EFLAGS);
>
>          tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, ~(CC_O | CC_C));
> @@ -1717,9 +1718,7 @@ static void gen_rotc_rm_T1(DisasContext *s, int ot, int 
> op1,
>  {
>      int label1;
>
> -    if (s->cc_op != CC_OP_DYNAMIC)
> -        gen_op_set_cc_op(s->cc_op);
> -    gen_compute_eflags(s, cpu_cc_src);
> +    gen_compute_eflags(s);
>
>      /* load */
>      if (op1 == OR_TMP0)
> @@ -6512,7 +6511,7 @@ static target_ulong disas_insn(DisasContext *s, 
> target_ulong pc_start)
>          if (CODE64(s) && !(s->cpuid_ext3_features & CPUID_EXT3_LAHF_LM))
>              goto illegal_op;
>          gen_op_mov_TN_reg(OT_BYTE, 0, R_AH);
> -        gen_compute_eflags(s, cpu_cc_src);
> +        gen_compute_eflags(s);
>          tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, CC_O);
>          tcg_gen_andi_tl(cpu_T[0], cpu_T[0], CC_S | CC_Z | CC_A | CC_P | 
> CC_C);
>          tcg_gen_or_tl(cpu_cc_src, cpu_cc_src, cpu_T[0]);
> @@ -6520,21 +6519,21 @@ static target_ulong disas_insn(DisasContext *s, 
> target_ulong pc_start)
>      case 0x9f: /* lahf */
>          if (CODE64(s) && !(s->cpuid_ext3_features & CPUID_EXT3_LAHF_LM))
>              goto illegal_op;
> -        gen_compute_eflags(s, cpu_T[0]);
> +        gen_compute_eflags(s);
>          /* Note: gen_compute_eflags() only gives the condition codes */
> -        tcg_gen_ori_tl(cpu_T[0], cpu_T[0], 0x02);
> +        tcg_gen_ori_tl(cpu_T[0], cpu_cc_src, 0x02);
>          gen_op_mov_reg_T0(OT_BYTE, R_AH);
>          break;
>      case 0xf5: /* cmc */
> -        gen_compute_eflags(s, cpu_cc_src);
> +        gen_compute_eflags(s);
>          tcg_gen_xori_tl(cpu_cc_src, cpu_cc_src, CC_C);
>          break;
>      case 0xf8: /* clc */
> -        gen_compute_eflags(s, cpu_cc_src);
> +        gen_compute_eflags(s);
>          tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, ~CC_C);
>          break;
>      case 0xf9: /* stc */
> -        gen_compute_eflags(s, cpu_cc_src);
> +        gen_compute_eflags(s);
>          tcg_gen_ori_tl(cpu_cc_src, cpu_cc_src, CC_C);
>          break;
>      case 0xfc: /* cld */
> @@ -6889,7 +6888,7 @@ static target_ulong disas_insn(DisasContext *s, 
> target_ulong pc_start)
>              case 1: /* loopz */
>                  gen_op_add_reg_im(s->aflag, R_ECX, -1);
>                  gen_op_jz_ecx(s->aflag, l3);
> -                gen_compute_eflags(s, cpu_tmp0);
> +                gen_compute_eflags(s);
>                  tcg_gen_andi_tl(cpu_tmp0, cpu_tmp0, CC_Z);
>                  if (b == 0) {
>                      tcg_gen_brcondi_tl(TCG_COND_EQ, cpu_tmp0, 0, l1);
> @@ -7431,7 +7430,7 @@ static target_ulong disas_insn(DisasContext *s, 
> target_ulong pc_start)
>             } else {
>                  gen_op_mov_reg_v(ot, rm, t0);
>              }
> -            gen_compute_eflags(s, cpu_cc_src);
> +            gen_compute_eflags(s);
>              tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, ~CC_Z);
>              tcg_gen_or_tl(cpu_cc_src, cpu_cc_src, t2);
>              tcg_temp_free(t0);
> --
> 1.7.12.1
>
>
>