Re: [Qemu-devel] [PATCH 1/7] tcg: Split out swap_commutative as a subroutine

[Aurelien Jarno <aurelien@aurel32.net>]

On Thu, Sep 27, 2012 at 10:19:51AM -0700, Richard Henderson wrote:
> Reduces code duplication and prefers
> 
>   movcond d, c1, c2, const, s
> to
>   movcond d, c1, c2, s, const
> 
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/optimize.c | 54 ++++++++++++++++++++++--------------------------------
>  1 file changed, 22 insertions(+), 32 deletions(-)
> 
> diff --git a/tcg/optimize.c b/tcg/optimize.c
> index 35532a1..55f2a24 100644
> --- a/tcg/optimize.c
> +++ b/tcg/optimize.c
> @@ -382,6 +382,21 @@ static TCGArg do_constant_folding_cond(TCGOpcode op, TCGArg x,
>      tcg_abort();
>  }
>  
> +static bool swap_commutative(TCGArg dest, TCGArg *p1, TCGArg *p2)
> +{
> +    TCGArg a1 = *p1, a2 = *p2;
> +    /* Prefer the constant in second argument, and then the form
> +       op a, a, b, which is better handled on non-RISC hosts. */
> +    if (temps[a1].state == TCG_TEMP_CONST
> +        || (dest != (TCGArg)-1 && dest == a2
> +            && temps[a2].state != TCG_TEMP_CONST)) {
> +        *p1 = a2;
> +        *p2 = a1;
> +        return true;
> +    }
> +    return false;
> +}
> +
>  /* Propagate constants and copies, fold constant expressions. */
>  static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
>                                      TCGArg *args, TCGOpDef *tcg_op_defs)
> @@ -391,7 +406,6 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
>      const TCGOpDef *def;
>      TCGArg *gen_args;
>      TCGArg tmp;
> -    TCGCond cond;
>  
>      /* Array VALS has an element for each temp.
>         If this temp holds a constant then its value is kept in VALS' element.
> @@ -434,52 +448,28 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
>          CASE_OP_32_64(eqv):
>          CASE_OP_32_64(nand):
>          CASE_OP_32_64(nor):
> -            /* Prefer the constant in second argument, and then the form
> -               op a, a, b, which is better handled on non-RISC hosts. */
> -            if (temps[args[1]].state == TCG_TEMP_CONST || (args[0] == args[2]
> -                && temps[args[2]].state != TCG_TEMP_CONST)) {
> -                tmp = args[1];
> -                args[1] = args[2];
> -                args[2] = tmp;
> -            }
> +            swap_commutative(args[0], &args[1], &args[2]);
>              break;
>          CASE_OP_32_64(brcond):
> -            if (temps[args[0]].state == TCG_TEMP_CONST
> -                && temps[args[1]].state != TCG_TEMP_CONST) {
> -                tmp = args[0];
> -                args[0] = args[1];
> -                args[1] = tmp;
> +            if (swap_commutative(-1, &args[0], &args[1])) {
>                  args[2] = tcg_swap_cond(args[2]);
>              }
>              break;
>          CASE_OP_32_64(setcond):
> -            if (temps[args[1]].state == TCG_TEMP_CONST
> -                && temps[args[2]].state != TCG_TEMP_CONST) {
> -                tmp = args[1];
> -                args[1] = args[2];
> -                args[2] = tmp;
> +            if (swap_commutative(args[0], &args[1], &args[2])) {
>                  args[3] = tcg_swap_cond(args[3]);
>              }
>              break;
>          CASE_OP_32_64(movcond):
> -            cond = args[5];
> -            if (temps[args[1]].state == TCG_TEMP_CONST
> -                && temps[args[2]].state != TCG_TEMP_CONST) {
> -                tmp = args[1];
> -                args[1] = args[2];
> -                args[2] = tmp;
> -                cond = tcg_swap_cond(cond);
> +            if (swap_commutative(-1, &args[1], &args[2])) {
> +                args[5] = tcg_swap_cond(args[5]);
>              }
>              /* For movcond, we canonicalize the "false" input reg to match
>                 the destination reg so that the tcg backend can implement
>                 a "move if true" operation.  */
> -            if (args[0] == args[3]) {
> -                tmp = args[3];
> -                args[3] = args[4];
> -                args[4] = tmp;
> -                cond = tcg_invert_cond(cond);
> +            if (swap_commutative(args[0], &args[4], &args[3])) {
> +                args[5] = tcg_invert_cond(args[5]);
>              }
> -            args[5] = cond;
>          default:
>              break;
>          }

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


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