[Bug tree-optimization/48702] [4.6/4.7 Regression] optimization regression with gcc-4.6 on x86_64-unknown-linux-gnu

[xinliangli at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48702

--- Comment #21 from davidxl <xinliangli at gmail dot com> 2011-05-19 05:02:29 UTC ---
Before a better fix is found, is the proposed patch ok? If yes, I will do more
testing and submit to gcc-patches@

David


(In reply to comment #19)
> On Tue, 17 May 2011, rakdver at kam dot mff.cuni.cz wrote:
> 
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48702
> > 
> > --- Comment #15 from rakdver at kam dot mff.cuni.cz <rakdver at kam dot mff.cuni.cz> 2011-05-17 19:26:18 UTC ---
> > Hi,
> > 
> > > The following patch fixes the problem. Is it ok?
> > 
> > as a heuristic, this probably makes sense.  Still, it does
> > not fix the problem, just masks it and makes it harder to reproduce,
> 
> Looks similar to my original workaround, no?
> 
> We can actually use something like the aliasing non-pointer base
> Zdenek mentioned upthread.  TARGET_MEM_REF has two index operands
> (where usually TMR_INDEX2 is NULL of TMR_BASE is non-constant).
> So we could build a TARGET_MEM_REF based off TMR_BASE 0B and
> move the non-pointer base to TMR_INDEX2.  The oracle then should
> not be able to disambiguate anything (and also no points-to
> info would be available, which probably doesn't make this the
> very very best idea either).
> 
> Richard.