[Bug middle-end/39157] Code that compiles fine in 1GB of memory with 4.1.2 requires > 20GB in 4.2.* and higher

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #12 from rguenther at suse dot de  2009-02-12 14:23 -------
Subject: Re:  Code that compiles fine in 1GB of memory
 with 4.1.2 requires > 20GB in 4.2.* and higher

On Thu, 12 Feb 2009, jakub at gcc dot gnu dot org wrote:

> ------- Comment #11 from jakub at gcc dot gnu dot org  2009-02-12 14:21 -------
> Created an attachment (id=17288)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17288&action=view)
>  --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17288&action=view)
> gcc44-pr39157.patch
> 
> Quick hack to avoid loop invariant motion from excessively large loops at -O1.
> With this cc1 still tops at 1.2GB, but loop invariants are still moved out of
> reasonably sized loops.  For the huge ones I wonder how much it buys in anyway,
> there it increases register pressure a lot.  10000 is pretty arbitrary, I
> wonder if we want a param or something.

I'd say for -O1 disable it completely, for -O2 and up use the
heuristic and add a param for it.

Richard.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39157