[Bug middle-end/23181] [4.1 Regression] Slowdown of the bresenham line drawing by roughly 20%

["law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #13 from law at redhat dot com  2005-10-31 23:36 -------
Subject: Re:  [4.1 Regression] Slowdown of the
        bresenham line drawing by roughly 20%

On Mon, 2005-10-31 at 23:25 +0000, hubicka at ucw dot cz wrote:

> See comment #5.  The fact that we ended up with more jumps was just the
> fact that dom transforms it into more dificult to optimize form
And how do you propose to change that without simply removing the
reassociation code from our tree optimizers?


>  (and we
> didn't have code sinking at that moment, there is also mentioned that
> code sinking would help here). 
> It is not CSE nor reassociation.  It is combining of the two increments
> done interesting way so we can't really undo it later.
It is definitely reassociation + simplification (reassociation without
simplification is, err, dumb) -- the code was lifted from cse.c and
transformed to work on trees in SSA form (and stuck into DOM as we
didn't have a better place to put it a couple years ago :(. 



jeff


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23181