Re: [Qemu-devel] [PATCH v3 4/9] tcg: Compress liveness data to 16 bits

[Aurelien Jarno]

On 2016-06-23 20:48, Richard Henderson wrote:
> This reduces both memory usage and per-insn cacheline usage
> during code generation.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/tcg.c | 58 ++++++++++++++++++++++------------------------------------
>  tcg/tcg.h | 16 ++++++++++------
>  2 files changed, 32 insertions(+), 42 deletions(-)
> 
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 64060c6..400e69c 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -1329,7 +1329,7 @@ static inline void tcg_la_bb_end(TCGContext *s, uint8_t 
> *dead_temps,
>      }
>  }
>  
> -/* Liveness analysis : update the opc_dead_args array to tell if a
> +/* Liveness analysis : update the opc_arg_life array to tell if a
>     given input arguments is dead. Instructions updating dead
>     temporaries are removed. */
>  static void tcg_liveness_analysis(TCGContext *s)
> @@ -1338,9 +1338,8 @@ static void tcg_liveness_analysis(TCGContext *s)
>      int oi, oi_prev, nb_ops;
>  
>      nb_ops = s->gen_next_op_idx;
> -    s->op_dead_args = tcg_malloc(nb_ops * sizeof(uint16_t));
> -    s->op_sync_args = tcg_malloc(nb_ops * sizeof(uint8_t));
> -    
> +    s->op_arg_life = tcg_malloc(nb_ops * sizeof(TCGLifeData));
> +
>      dead_temps = tcg_malloc(s->nb_temps);
>      mem_temps = tcg_malloc(s->nb_temps);
>      tcg_la_func_end(s, dead_temps, mem_temps);
> @@ -1349,8 +1348,7 @@ static void tcg_liveness_analysis(TCGContext *s)
>          int i, nb_iargs, nb_oargs;
>          TCGOpcode opc_new, opc_new2;
>          bool have_opc_new2;
> -        uint16_t dead_args;
> -        uint8_t sync_args;
> +        TCGLifeData arg_life = 0;

A small improvement, probably for later: we can zero the s->op_arg_life
structure, and then access it directly instead of using the arg_life
temporary variable.

Reviewed-by: Aurelien Jarno <address@hidden>

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
address@hidden                 http://www.aurel32.net