[Bug tree-optimization/38401] TreeSSA-PRE load after store missed optimization

[sergeid at il dot ibm dot com]

------- Comment #16 from sergeid at il dot ibm dot com  2008-12-21 07:44 -------
(In reply to comment #15)
> Re. comment #14: Yes, I suppose so.  Why do you want to remove gcse-las from
> mainline.  Not that I'm against it -- ideally RTL gcse.c would not work on
> memory at all anymore -- but I wouldn't remove gcse-las until we catch in the
> GIMPLE optimizers as much as possible of the things we still need gcse-las for.

For the time being this is the only case I've found out which is missed by
tree-PRE and caught by GCSE-LAS. As you pointed out, GCSE-LAS doesn't seem to
help much.

> It seems to me, btw, that it might be easier to teach GIMPLE loop invariant
> code motion about this transformation.  Adding this in GIMPLE PRE might be a
> little too expensive...?

That may be; I was just noting that such redundancies should be caught
somewhere at the GIMPLE stage.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38401