https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82918
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Probably fixed by r255093
2017-11-23 Richard Biener <rguent...@suse.de>
PR tree-optimization/23094
* tree-ssa-sccvn.c (vuse_ssa_val): Handle VN_TOP when we
come here from walking over backedges in the first iteration.
(vn_reference_lookup_3): Skip clobbers that store the same value.
* gcc.dg/tree-ssa/ssa-fre-61.c: New testcase.
because we now see that we at most store the same value to value.data[0].
_1 = value2_6(D)->data[0];
value_5(D)->data[0] = _1;
_2 = value2_6(D)->data[0];
But the handling is quite simplistic so
value.data[0] = value2.data[0]+1;
value.data[1] = value2.data[0]+1;
value.data[2] = value2.data[0]+1;
isn't handled. We also do not walk which is why the swapped case isn't
handled either.
