[Bug tree-optimization/23940] SSA_NAMEs are not released after no longer being used.

["pinskia at physics dot uc dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pinskia at physics dot uc dot edu  2005-09-19 16:44 -------
Subject: Re:  SSA_NAMEs are not released after no longer being used.


On Sep 19, 2005, at 12:33 PM, amacleod at redhat dot com wrote:

> "And that will not work for the SSA_NAMEs used for aliasing and then 
> the
> variable becomes a gimple register."
>
> If we set SSA_NAME_DEF_FOR_STMT during inserts, and clear it during 
> bsi_remove,
> does that resolve the issues you are referring to?

We don't call bsi_remove for those statements so SSA_NAME_DEF_FOR_STMT 
is always
set to that statement even though the SSA_NAME is unused.

The testcase (-O1 -fno-tree-fre) from my orginal email on the subject:
int f(void)
{
int i;
int *j = &i;
i = 1;
return *j;
}

SSA form right before .alias2:
   #   i_4 = V_MUST_DEF <i_3>;
   i = tt_2;
   D.1274_5 = tt_2;
   return tt_2;

After:
   i_1 = tt_2;
   D.1274_5 = tt_2;
   return tt_2;


Note that i_4 is not freed and its SSA_NAME_DEF_FOR_STMT is NULLd.

Thanks,
Andrew Pinski



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23940