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[Bug middle-end/34743] Testcase gcc.dg/tree-ssa/20070302-1.c is broken



------- Comment #1 from rguenth at gcc dot gnu dot org  2008-01-11 15:57 -------
It's doing the correct thing.  We have

p_1, name memory tag: NMT.14, is dereferenced, points-to vars: { SFT.3 SFT.7 }

(SFT.3 is x.x, SFT.7 is z.x)

Now, NMT.14 is marked call clobbered:

NMT.14, UID D.1582, struct A, is addressable, score: 40, direct reads: 2,
direct writes: 1, indirect reads: 0, indirect writes: 2, call clobbered (passed
to call), may aliases: { SFT.3 SFT.7 }

because one of its pointed-to vars is call clobbered (SFT.7, aka z, which is
passed to the call).  Here:

static void
compute_tag_properties (void)
{
...
          EXECUTE_IF_SET_IN_BITMAP (ma, 0, i, bi)
            {
              entry = referenced_var (i);
              /* Call clobbered entries cause the tag to be marked
                 call clobbered.  */
              if (!tagcc && is_call_clobbered (entry)) 
                {
                  mark_call_clobbered (tag, var_ann (entry)->escape_mask);
                  tagcc = true;
                  changed = true;
                }

I don't know if we can disable this if var_ann (entry)->escape_mask ==
ESCAPE_TO_CALL.

I don't know if we need to propagate tags from NMT aliases to the NMT
this way at all - after all we add all subvars of an escaped var to
call clobbered vars already.

So, confirmed - there's a missing optimization.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |alias, missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2008-01-11 15:57:57
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34743


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