[Bug tree-optimization/25737] [4.1/4.2 Regression] ACATS c974001 c974013 hang with struct aliasing

[dberlin at dberlin dot org]

------- Comment #26 from dberlin at gcc dot gnu dot org  2006-05-15 12:42 -------
Subject: Re:  [4.1/4.2 Regression] ACATS c974001
 c974013 hang with struct aliasing

ebotcazou at gcc dot gnu dot org wrote:
> ------- Comment #25 from ebotcazou at gcc dot gnu dot org  2006-05-15 05:36 -------
>> (I've not fully understood the discussion here, but if everything in Ada is 
>> addressable, then it seems to me that everything should have TREE_ADDRESSABLE 
>> set.)
> 
> Grumpf... you read a little too quickly, that is exactly the opposite.  The
> struct aliasing machinery essentially assumes that everything is addressable
> (modulo bit-fields) whereas *nothing* is addressable by default in Ada.
> 

Read comment 20 again.  If nothing was addressable, and we relied on
this, your problem would get worse, *not better*.

It will cause *strictly more* things to be marked unaliased, and your
problem is that this really is aliasable.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25737