[Bug tree-optimization/30567] [4.2 Regression] -O3 optimizer bug

[dberlin at dberlin dot org]

------- Comment #31 from dberlin at gcc dot gnu dot org  2007-04-25 17:01 -------
Subject: Re:  [4.2 Regression] -O3 optimizer bug

On 25 Apr 2007 15:32:41 -0000, rguenth at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #29 from rguenth at gcc dot gnu dot org  2007-04-25 16:32 -------
> Oh, btw. why the may_aliases bitmap for SMT.11 is empty on entry to the loops
> computing the transitive closure (it tries to, right?) is that SFT.0 is not
> considered stored to in the first nested loop over pointers and addressable
> vars.  Shouldn't we add the vars NMT aliases to ai->written_vars in
> compute_flow_sensitive_aliasing?

This is a better fix.
The other "fix" is just a hack.  Aliasing is not symmetric, so we
shouldn't make the two points-to sets equal.

However, I bet if you look at where we initially add written vars,
you'll discover we are missing it there for some reason, and don't
need to post-add it like you do here.

I think i fixed something like this in 4.3 where we didn't consider
stores to globals or arguments to be written or somesuch when we were
initially generating written vars.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30567