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

["amacleod at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From amacleod at redhat dot com  2005-09-30 14:53 -------
I'm fine with the releasessaname.diff.txt

you aren't doing anything different than we normally do now. I prefer this over
adding a flag to bsi_remove for sure.

I looked into an alternative which follows up on the thread we had going. A
better longer term solution is to have it all taken care of automatically. I got
most of the way through implementing the automatic setting and clearing of
SSA_NAME_DEF_STMT as stmts are processed by build_stmt_operands(). That is the
one place where we know  precisely when a stmt has entered and exited the IL.
Then between passes it is trivial to check if SSA_NAME_DEF_STMT is NULL and free
the ssa-name.  

I had it mostly working, but the changes are pretty invasive as no one ever has
to set or clear SSA_NAME_DEF_STMT any more, its always simply "right".  Its too
invasive for stage 3 thats for sure. I'll revisit it when we get back to stage 1
and test out performance and whether its really what we want to do.

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