[Bug fortran/41212] [4.5 Regression] miscompilation at -O2

[rguenther at suse dot de]

------- Comment #8 from rguenther at suse dot de  2009-09-03 16:50 -------
Subject: Re:  [4.5 Regression] miscompilation  at  -O2

On Thu, 3 Sep 2009, matz at gcc dot gnu dot org wrote:

> ------- Comment #7 from matz at gcc dot gnu dot org  2009-09-03 16:39 -------
> Hmm, in a sense what forward prop is doing is at least fishy.  It forwards
> the casted ADDR_EXPR into some references of y_13, but not into all of them.
> As y_13 is a restrict pointer this is always going to be a problem, because
> suddenly you have accesses to the object via that restrict pointer and via
> something else not based on that pointer.
> 
> Either forward prop needs to forward this into _all_ y_13 uses or into none.

That won't help.  The canonical counter-example would be that the
caller already accesses the plain y and z variables.  That forwprop
"simulates" this is just unfortunate.  I'll nevertheless look into
the forwprop issue - but that will just fix this particular testcase
without addressing the real problem.

Richard.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41212