Re: [Qemu-devel] [PATCH v4 28/33] tcg-ppc64: Use ISEL for setcond

[Aurelien Jarno <aurelien@aurel32.net>]

On Thu, Apr 04, 2013 at 05:56:21PM -0500, Richard Henderson wrote:
> There are a few simple special cases that should be handled first.
> Break these out to subroutines to avoid code duplication.
> 
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/ppc64/tcg-target.c | 181 ++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 119 insertions(+), 62 deletions(-)
> 
> diff --git a/tcg/ppc64/tcg-target.c b/tcg/ppc64/tcg-target.c
> index f0ed698..27a7ff2 100644
> --- a/tcg/ppc64/tcg-target.c
> +++ b/tcg/ppc64/tcg-target.c
> @@ -45,6 +45,7 @@ static uint8_t *tb_ret_addr;
>  #endif
>  
>  #define HAVE_ISA_2_06  0
> +#define HAVE_ISEL      0
>  
>  #ifdef CONFIG_USE_GUEST_BASE
>  #define TCG_GUEST_BASE_REG 30
> @@ -390,6 +391,7 @@ static int tcg_target_const_match (tcg_target_long val,
>  #define ORC    XO31(412)
>  #define EQV    XO31(284)
>  #define NAND   XO31(476)
> +#define ISEL   XO31( 15)
>  
>  #define MULLD  XO31(233)
>  #define MULHD  XO31( 73)
> @@ -445,6 +447,7 @@ static int tcg_target_const_match (tcg_target_long val,
>  #define BT(n, c) (((c)+((n)*4))<<21)
>  #define BA(n, c) (((c)+((n)*4))<<16)
>  #define BB(n, c) (((c)+((n)*4))<<11)
> +#define BC_(n, c) (((c)+((n)*4))<<6)
>  
>  #define BO_COND_TRUE  BO (12)
>  #define BO_COND_FALSE BO ( 4)
> @@ -470,6 +473,20 @@ static const uint32_t tcg_to_bc[] = {
>      [TCG_COND_GTU] = BC | BI (7, CR_GT) | BO_COND_TRUE,
>  };
>  
> +/* The low bit here is set if the RA and RB fields must be inverted.  */
> +static const uint32_t tcg_to_isel[] = {
> +    [TCG_COND_EQ]  = ISEL | BC_(7, CR_EQ),
> +    [TCG_COND_NE]  = ISEL | BC_(7, CR_EQ) | 1,
> +    [TCG_COND_LT]  = ISEL | BC_(7, CR_LT),
> +    [TCG_COND_GE]  = ISEL | BC_(7, CR_LT) | 1,
> +    [TCG_COND_LE]  = ISEL | BC_(7, CR_GT) | 1,
> +    [TCG_COND_GT]  = ISEL | BC_(7, CR_GT),
> +    [TCG_COND_LTU] = ISEL | BC_(7, CR_LT),
> +    [TCG_COND_GEU] = ISEL | BC_(7, CR_LT) | 1,
> +    [TCG_COND_LEU] = ISEL | BC_(7, CR_GT) | 1,
> +    [TCG_COND_GTU] = ISEL | BC_(7, CR_GT),
> +};
> +
>  static inline void tcg_out_mov(TCGContext *s, TCGType type,
>                                 TCGReg ret, TCGReg arg)
>  {
> @@ -1131,79 +1148,119 @@ static void tcg_out_cmp(TCGContext *s, int cond, TCGArg arg1, TCGArg arg2,
>      }
>  }
>  
> -static void tcg_out_setcond (TCGContext *s, TCGType type, TCGCond cond,
> -                             TCGArg arg0, TCGArg arg1, TCGArg arg2,
> -                             int const_arg2)
> +static void tcg_out_setcond_eq0(TCGContext *s, TCGType type,
> +                                TCGReg dst, TCGReg src)
>  {
> -    int crop, sh, arg;
> +    tcg_out32(s, (type == TCG_TYPE_I64 ? CNTLZD : CNTLZW) | RS(src) | RA(dst));
> +    tcg_out_shri64(s, dst, dst, type == TCG_TYPE_I64 ? 6 : 5);
> +}
>  
> -    switch (cond) {
> -    case TCG_COND_EQ:
> -        if (const_arg2) {
> -            if (!arg2) {
> -                arg = arg1;
> -            }
> -            else {
> -                arg = 0;
> -                if ((uint16_t) arg2 == arg2) {
> -                    tcg_out32(s, XORI | SAI(arg1, 0, arg2));
> -                }
> -                else {
> -                    tcg_out_movi (s, type, 0, arg2);
> -                    tcg_out32 (s, XOR | SAB (arg1, 0, 0));
> -                }
> -            }
> -        }
> -        else {
> -            arg = 0;
> -            tcg_out32 (s, XOR | SAB (arg1, 0, arg2));
> -        }
> +static void tcg_out_setcond_ne0(TCGContext *s, TCGReg dst, TCGReg src)
> +{
> +    /* X != 0 implies X + -1 generates a carry.  Extra addition
> +       trickery means: R = X-1 + ~X + C = X-1 + (-X+1) + C = C.  */
> +    if (dst != src) {
> +        tcg_out32(s, ADDIC | TAI(dst, src, -1));
> +        tcg_out32(s, SUBFE | TAB(dst, dst, src));
> +    } else {
> +        tcg_out32(s, ADDIC | TAI(0, src, -1));
> +        tcg_out32(s, SUBFE | TAB(dst, 0, src));
> +    }
> +}
>  
> -        if (type == TCG_TYPE_I64) {
> -            tcg_out32 (s, CNTLZD | RS (arg) | RA (0));
> -            tcg_out_rld (s, RLDICL, arg0, 0, 58, 6);
> -        }
> -        else {
> -            tcg_out32 (s, CNTLZW | RS (arg) | RA (0));
> -            tcg_out_rlw(s, RLWINM, arg0, 0, 27, 5, 31);
> +static TCGReg tcg_gen_setcond_xor(TCGContext *s, TCGReg arg1, TCGArg arg2,
> +                                  bool const_arg2)
> +{
> +    if (const_arg2) {
> +        if ((uint32_t)arg2 == arg2) {
> +            tcg_out_xori32(s, TCG_REG_R0, arg1, arg2);
> +        } else {
> +            tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_R0, arg2);
> +            tcg_out32(s, XOR | SAB(arg1, TCG_REG_R0, TCG_REG_R0));
>          }
> -        break;
> +    } else {
> +        tcg_out32(s, XOR | SAB(arg1, TCG_REG_R0, arg2));
> +    }
> +    return TCG_REG_R0;
> +}
>  
> -    case TCG_COND_NE:
> -        if (const_arg2) {
> -            if (!arg2) {
> -                arg = arg1;
> -            }
> -            else {
> -                arg = 0;
> -                if ((uint16_t) arg2 == arg2) {
> -                    tcg_out32(s, XORI | SAI(arg1, 0, arg2));
> -                } else {
> -                    tcg_out_movi (s, type, 0, arg2);
> -                    tcg_out32 (s, XOR | SAB (arg1, 0, 0));
> -                }
> +static void tcg_out_setcond(TCGContext *s, TCGType type, TCGCond cond,
> +                            TCGArg arg0, TCGArg arg1, TCGArg arg2,
> +                            int const_arg2)
> +{
> +    int crop, sh;
> +
> +    /* Ignore high bits of a potential constant arg2.  */
> +    if (type == TCG_TYPE_I32) {
> +        arg2 = (uint32_t)arg2;
> +    }
> +
> +    /* Handle common and trivial cases before handling anything else.  */
> +    if (arg2 == 0) {
> +        switch (cond) {
> +        case TCG_COND_EQ:
> +            tcg_out_setcond_eq0(s, type, arg0, arg1);
> +            return;
> +        case TCG_COND_NE:
> +            if (type == TCG_TYPE_I32) {
> +                tcg_out_ext32u(s, TCG_REG_R0, arg1);
> +                arg1 = TCG_REG_R0;
>              }
> +            tcg_out_setcond_ne0(s, arg0, arg1);
> +            return;
> +        case TCG_COND_GE:
> +            tcg_out32(s, NOR | SAB(arg1, arg0, arg1));
> +            arg1 = arg0;
> +            /* FALLTHRU */
> +        case TCG_COND_LT:
> +            /* Extract the sign bit.  */
> +            tcg_out_rld(s, RLDICL, arg0, arg1,
> +                        type == TCG_TYPE_I64 ? 1 : 33, 63);
> +            return;
> +        default:
> +            break;
>          }
> -        else {
> -            arg = 0;
> -            tcg_out32 (s, XOR | SAB (arg1, 0, arg2));
> -        }
> +    }
>  
> -        /* Make sure and discard the high 32-bits of the input.  */
> -        if (type == TCG_TYPE_I32) {
> -            tcg_out32(s, EXTSW | RA(TCG_REG_R0) | RS(arg));
> -            arg = TCG_REG_R0;
> -        }
> +    /* If we have ISEL, we can implement everything with 3 or 4 insns.
> +       All other cases below are also at least 3 insns, so speed up the
> +       code generator by not considering them and always using ISEL.  */
> +    if (HAVE_ISEL) {
> +        int isel, tab;
> +
> +        tcg_out_cmp(s, cond, arg1, arg2, const_arg2, 7, type);
> +
> +        isel = tcg_to_isel[cond];
>  
> -        if (arg == arg1 && arg1 == arg0) {
> -            tcg_out32(s, ADDIC | TAI(0, arg, -1));
> -            tcg_out32(s, SUBFE | TAB(arg0, 0, arg));
> +        tcg_out_movi(s, type, arg0, 1);
> +        if (isel & 1) {
> +            /* arg0 = (bc ? 0 : 1) */
> +            tab = TAB(arg0, 0, arg0);
> +            isel &= ~1;
> +        } else {
> +            /* arg0 = (bc ? 1 : 0) */
> +            tcg_out_movi(s, type, TCG_REG_R0, 0);
> +            tab = TAB(arg0, arg0, TCG_REG_R0);
>          }
> -        else {
> -            tcg_out32(s, ADDIC | TAI(arg0, arg, -1));
> -            tcg_out32(s, SUBFE | TAB(arg0, arg0, arg));
> +        tcg_out32(s, isel | tab);
> +        return;
> +    }
> +
> +    switch (cond) {
> +    case TCG_COND_EQ:
> +        arg1 = tcg_gen_setcond_xor(s, arg1, arg2, const_arg2);
> +        tcg_out_setcond_eq0(s, type, arg0, arg1);
> +        return;
> +
> +    case TCG_COND_NE:
> +        arg1 = tcg_gen_setcond_xor(s, arg1, arg2, const_arg2);
> +        /* Discard the high bits only once, rather than both inputs.  */
> +        if (type == TCG_TYPE_I32) {
> +            tcg_out_ext32u(s, TCG_REG_R0, arg1);
> +            arg1 = TCG_REG_R0;
>          }
> -        break;
> +        tcg_out_setcond_ne0(s, arg0, arg1);
> +        return;
>  
>      case TCG_COND_GT:
>      case TCG_COND_GTU:

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net