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[Bug tree-optimization/71466] [7 Regression] wrong code at -O3 on x86_64-linux-gnu
- From: "hubicka at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sat, 11 Jun 2016 13:50:14 +0000
- Subject: [Bug tree-optimization/71466] [7 Regression] wrong code at -O3 on x86_64-linux-gnu
- Auto-submitted: auto-generated
- References: <bug-71466-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71466
--- Comment #10 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Iterations bounds are computed at early optimization time and maintained
thorough. So the info is computed at thread2 time.
Looking into testcase I noticed that jump threading seems to be doing useless
work on degenerate PHI:
# f_28 = PHI <1(8), 1(2)>
...
if (f_28 == 0)
When the code was part of vrp/dom, perhaps it never seen this oppurtunity
because the constant got propagated first?