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Re: [PATCH] Fix PR42509, wrong-code from the RTL alias oracle


On Tue, 27 Jul 2010, Ulrich Weigand wrote:

> Richard Guenther wrote:
> 
> > 	PR middle-end/42509
> > 	* alias.c (nonoverlapping_memrefs_p): For spill-slot accesses
> > 	require a non-NULL MEM_OFFSET.
> 
> What are your thoughts on backporting this to the 4.4 branch?
> 
> It seems that this problem never existed in 4.3 and earlier because
> it was introduced by IRA and the spill_slot_decl logic; and the bug
> is fixed in 4.5 and later.  However, it exists as latent bug in 4.4.
> 
> Now, I was unable to construct a problem to deliberately trigger
> the issue (you need just the right interaction between reload,
> alias, and cross-jumping ...).  However, it seems to have occured
> in an out-of-tree port:
> http://gcc.gnu.org/ml/gcc/2010-04/msg00243.html
> 
> Since the fix looks to me as if it couldn't really have any adverse
> effects, and it fixes a potentially hard to track down latent wrong
> code generation bug, it might be good to backport ...

If you want to do it and do the testing a backport is fine with me.

Richard.


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