[Bug tree-optimization/62173] [5.0 regression] 64bit Arch can't ivopt while 32bit Arch can

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62173

--- Comment #21 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 26 Jan 2015, ramana at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62173
> 
> --- Comment #19 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #18)
> > It's probably not correct to simply transfer range info from *idx to
> > iv->base.
> > Instead SCEV analysis needs to track the range of CHREC_LEFT when it analyzes
> > the SSA use-def chain.  That's of course a much bigger change :/
> > 
> > The patch may still help in some cases - I suppose the original testcase is
> > reduced from sth else?
> 
> Not sure if this is related to comment #c2 where the reference is to a 15%
> regression in bzip2 compress at O3. Sebastian could probably confirm.
> 
> I don't think we can ignore the regression though, can we ?

We should try not to.