Re: [Qemu-devel] [PATCH for-2.5 03/10] tcg/optimize: track const/copy status separately

[Paolo Bonzini <pbonzini@redhat.com>]

On 24/07/2015 18:30, Aurelien Jarno wrote:
> Use two bools to track constants and copies instead of an enum.
> 
> Cc: Richard Henderson <rth@twiddle.net>
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  tcg/optimize.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/tcg/optimize.c b/tcg/optimize.c
> index d2b63a4..f16eb1e 100644
> --- a/tcg/optimize.c
> +++ b/tcg/optimize.c
> @@ -35,14 +35,9 @@
>          glue(glue(case INDEX_op_, x), _i32):    \
>          glue(glue(case INDEX_op_, x), _i64)
>  
> -typedef enum {
> -    TCG_TEMP_UNDEF = 0,
> -    TCG_TEMP_CONST,
> -    TCG_TEMP_COPY,
> -} tcg_temp_state;
> -
>  struct tcg_temp_info {
> -    tcg_temp_state state;
> +    bool is_const;
> +    bool is_copy;

Could temps[arg].is_copy be replaced by temps[arg].next_copy != arg?

For example, this:

    if (temps[temp].prev_copy == temps[temp].next_copy) {
        temps[temps[temp].next_copy].is_copy = false;
    } else {
        temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
        temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
    }

would be replaced simply by

    temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
    temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;

Paolo

>      uint16_t prev_copy;
>      uint16_t next_copy;
>      tcg_target_ulong val;
> @@ -54,12 +49,12 @@ static TCGTempSet temps_used;
>  
>  static inline bool temp_is_const(TCGArg arg)
>  {
> -    return temps[arg].state == TCG_TEMP_CONST;
> +    return temps[arg].is_const;
>  }
>  
>  static inline bool temp_is_copy(TCGArg arg)
>  {
> -    return temps[arg].state == TCG_TEMP_COPY;
> +    return temps[arg].is_copy;
>  }
>  
>  /* Reset TEMP's state to TCG_TEMP_UNDEF.  If TEMP only had one copy, remove
> @@ -68,13 +63,14 @@ static void reset_temp(TCGArg temp)
>  {
>      if (temp_is_copy(temp)) {
>          if (temps[temp].prev_copy == temps[temp].next_copy) {
> -            temps[temps[temp].next_copy].state = TCG_TEMP_UNDEF;
> +            temps[temps[temp].next_copy].is_copy = false;
>          } else {
>              temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
>              temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
>          }
>      }
> -    temps[temp].state = TCG_TEMP_UNDEF;
> +    temps[temp].is_const = false;
> +    temps[temp].is_copy = false;
>      temps[temp].mask = -1;
>  }
>  
> @@ -88,7 +84,8 @@ static void reset_all_temps(int nb_temps)
>  static void init_temp_info(TCGArg temp)
>  {
>      if (!test_bit(temp, temps_used.l)) {
> -        temps[temp].state = TCG_TEMP_UNDEF;
> +        temps[temp].is_const = false;
> +        temps[temp].is_copy = false;
>          temps[temp].mask = -1;
>          set_bit(temp, temps_used.l);
>      }
> @@ -218,7 +215,8 @@ static void tcg_opt_gen_movi(TCGContext *s, TCGOp *op, TCGArg *args,
>      op->opc = new_op;
>  
>      reset_temp(dst);
> -    temps[dst].state = TCG_TEMP_CONST;
> +    temps[dst].is_const = true;
> +    temps[dst].is_copy = false;
>      temps[dst].val = val;
>      mask = val;
>      if (TCG_TARGET_REG_BITS > 32 && new_op == INDEX_op_movi_i32) {
> @@ -261,11 +259,13 @@ static void tcg_opt_gen_mov(TCGContext *s, TCGOp *op, TCGArg *args,
>  
>      if (s->temps[src].type == s->temps[dst].type) {
>          if (!temp_is_copy(src)) {
> -            temps[src].state = TCG_TEMP_COPY;
> +            temps[src].is_const = false;
> +            temps[src].is_copy = true;
>              temps[src].next_copy = src;
>              temps[src].prev_copy = src;
>          }
> -        temps[dst].state = TCG_TEMP_COPY;
> +        temps[dst].is_const = false;
> +        temps[dst].is_copy = true;
>          temps[dst].next_copy = temps[src].next_copy;
>          temps[dst].prev_copy = src;
>          temps[temps[dst].next_copy].prev_copy = dst;
>