http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42169
Vladimir Makarov <vmakarov at redhat dot com> changed:
What |Removed |Added
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CC| |vmakarov at redhat dot com
--- Comment #22 from Vladimir Makarov <vmakarov at redhat dot com> 2010-10-20
03:03:53 UTC ---
Function store_can_be_removed_p was written in assumption that the store is on
a loop exit. Apparently it is not true. In this case, it was actually a loop
entry from 4 to 5 in loop tree:
0->1->2->3->4->5
|
-->6->7
There should be some rare combinations of conditions (one is that pseudo is not
changed in whole program) to achieve gcc_unreachable for the loop entry.
Therefore it is hard to reproduce.
There is a very simple solution which is to return false (preventing this
optimization) instead of gcc_unreachable (that is a loop entry case).
I'll send a patch soon.
