http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54735
--- Comment #12 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-10-02
13:03:07 UTC ---
Actually that just papers over the real issue. The issue is that
cfg-cleanup runs before update-ssa and that removes a basic-block (9)
because we have
<bb 8>:
D.2778 ={v} {CLOBBER};
if (1 == 0)
goto <bb 9>;
else
goto <bb 33>;
<bb 9>:
# .MEM_62 = VDEF <.MEM_60>
D.2632.m_col = 0;
<bb 10>:
# VUSE <.MEM_62>
__assert_fail (0);
but as you can see this removes the definition for .MEM_62!
That is what confuses update-SSA (rightfully so - it re-assigns .MEM_62
to the inserted PHI node).
Which means we need to update virtual SSA form right here, before
calling cfgcleanup.
