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Subject: [Bug regression/46931] [4.6 Regression] Subversion id 167184 breaks building perlbench on power7 with debug
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46931

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aoliva at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
   Target Milestone|---                         |4.6.0
            Summary|Subversion id 167184 breaks |[4.6 Regression] Subversion
                   |building perlbench on       |id 167184 breaks building
                   |power7 with debug           |perlbench on power7 with
                   |                            |debug
           Severity|major                       |normal

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-12-16 14:15:02 UTC ---
(In reply to comment #2)
> I think the actual problem was introduced in PR46172 commit, with the addition
> of remove_dead_stmts_from_loop, as we now DCE what we have created during the
> vectorization.
> This function gsi_removes a stmt and then calls release_defs, which does
> nothing though, because the SSA_NAME is name_registered_for_update_p, so the
> release of it is deferred.  But when delete_update_ssa attempts to release the
> SSANAME afterwards, the bb for the stmt is already NULL and so gsi_for_stmt
> fails.
> 
> Not sure if there is something wrong on the remove_dead_stmts_from_loop side,
> or if just releasing what has been created in the same pass has never been done
> before and we should make insert_debug_temp_for_var_def do nothing if
> gsi is NULL and def_stmt has NULL gimple_bb and the RHS isn't a constant.

Hmm.  We definitely shouldn't insert debug stmts for stmts that are no longer
in the insn stream...