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re:[PATCH] Fix PR34263: Cleaning up latch blocks
- From: Revital1 Eres <ERES at il dot ibm dot com>
- To: Andrew MacLeod <amacleod at redhat dot com>
- Cc: Ayal Zaks <zaks at il dot ibm dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>, Mircea Namolaru <namolaru at il dot ibm dot com>, Andrew Pinski <pinskia at gmail dot com>
- Date: Fri, 14 Dec 2007 13:12:49 +0200
- Subject: re:[PATCH] Fix PR34263: Cleaning up latch blocks
Thanks for your reply!
> Effectively stashing the value of a_2 to load back in the case where we
> exit. Is this right? (except it is actually working on the coalesced
> root variables, not the actual SSA_NAMES)
Yes, that's correct.
> Seems to me there is an older PR that involves a similar situation too ,
> but I dont recall it.
It might be PR19038, which this patch was originally taken from.
> Should there be some kind of limit to the number of copies being
> inserted? Ie, if there are 10 copies being inserted on the edge, I would
> think 10 extra copies in the loop would tend to start adding up and
> offset whatever gain you might get.
That sounds reasonable, I can add a default number to consider only small
latches. (and maybe add a new --param option to tune it?)
> As long as there isn't disagreement on whether the extra copies in and
> out of the loop are a problem, the patch istself is OK.
I will address your comments and re-submit the patch.