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Re: [PATCH] Update bb count and freq when merging two blocks
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: Dehao Chen <dehao at google dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, David Li <davidxl at google dot com>
- Date: Fri, 16 May 2014 23:28:16 +0200
- Subject: Re: [PATCH] Update bb count and freq when merging two blocks
- Authentication-results: sourceware.org; auth=none
- References: <CAO2gOZWsxUcxy4Azjyhbr9qmv4nUzr5zw7hmKqwWK2_Yz4k6JQ at mail dot gmail dot com> <20140516212801 dot GA27869 at kam dot mff dot cuni dot cz>
> > 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.
And patch is OK with that change.
Honza
>
> Honza