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Re: [PATCH] Update bb count and freq when merging two blocks


> This patch makes sure max count is used when merging two basic blocks.
> 
> Bootstrapped and testing on-going.
> 
> OK for trunk if test is ok?
> 
> Thanks,
> Dehao
> 
> gcc/ChangeLog:
> 2014-05-16  Dehao Chen  <dehao@google.com>
> 
>         * tree-cfg.c (gimple_merge_blocks): Updates bb count with max count.
> 
> Index: gcc/tree-cfg.c
> ===================================================================
> --- gcc/tree-cfg.c (revision 210531)
> +++ gcc/tree-cfg.c (working copy)
> @@ -1877,6 +1877,15 @@ gimple_merge_blocks (basic_block a, basic_block b)
>   }
>      }
> 
> +  /* When merging two BBs, if their counts are different, the larger count
> +     is selected as the new bb count. This is to handle inconsistent
> +     profiles.  */
> +  if (a->count != b->count)
> +    {
> +      a->count = MAX (a->count, b->count);
> +      a->frequency = MAX (a->frequency, b->frequency);
> +    }

I would do max of frequency indpendently on count.  I.e. just remove the conditional around
the MAX operation.
This seems to make sense even w/o profile feedback.

Honza


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