Re: [Qemu-devel] [PATCH 04/13] tcg: sync output arguments on liveness request

[Richard Henderson <rth@twiddle.net>]

On 09/27/2012 10:15 AM, Aurelien Jarno wrote:
> Synchronize an output argument when requested by the liveness analysis.
> This is needed so that the temp can be declared dead later.
> 
> For that, add a new op_sync_args table in which each bit tells if the
> corresponding output argument needs to be synchronized with the memory.
> Pass it to the tcg_reg_alloc_* functions, and honor this bit. We need to
> synchronize the argument before marking it as dead, and we have to make
> sure all the infos about the temp are correctly filled.
> 
> At the same time change some types from unsigned int to uint16_t when
> passing op_dead_args.
> 
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

If I understand the patch correctly, this patch alone is no change,
since no sync_args bits are ever set.

Which means that

> +        if (NEED_SYNC_ARG(i)) {
> +            tcg_reg_sync(s, reg);
> +        }
> +        if (IS_DEAD_ARG(i)) {
> +            temp_dead(s, args[i]);
> +        }

Might ought to be better written as

  if (IS_DEAD_ARG(i)) {
     ...
  } else if (NEED_SYNC_ARG(i)) {
     ...
  }

as temp_dead implies sync from patches 2 and 3.  This pattern is also
replicated 3-4 times.  Subroutine?


r~