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From: "spop at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/65177] [5 Regression]: extend jump thread for finite state automata causes miscompilation
Date: Wed, 25 Feb 2015 23:05:00 -0000
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X-Bugzilla-Type: changed
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 5.0
X-Bugzilla-Keywords: wrong-code
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X-Bugzilla-Who: spop at gcc dot gnu.org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65177

Sebastian Pop <spop at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |UNCONFIRMED
   Last reconfirmed|2015-02-25 00:00:00         |
     Ever confirmed|1                           |0

--- Comment #6 from Sebastian Pop <spop at gcc dot gnu.org> ---
The SEME region copier does not update the SSA correctly:

bb_53:
      # i_1 = PHI <i_126(13), i_250(52)>
      # sprv_5 = PHI <sprv_137(13), sprv_284(52)>
      # .MEM_7 = PHI <.MEM_331(13), .MEM_337(52)>
      # k_339 = PHI <k_84(13), k_285(52)>
      # sprv_780 = PHI <1(13), 7(52)>

bb_104 is a copy of bb_53:
      # i_672 = PHI <i_126(13)>
      # sprv_437 = PHI <sprv_137(13)>
      # .MEM_715 = PHI <.MEM_331(13)>
      # k_716 = PHI <k_84(13)>
      # sprv_717 = PHI <1(13)>


bb_64:
      # _319 = PHI <0.0(55), 0.0(58), _313(61)>
      # sprv_751 = PHI <sprv_5(55), 5(58), 8(61)>
      # i_769 = PHI <i_1(55), i_766(58), i_767(61)>
      # sprv_784 = PHI <sprv_780(55), sprv_781(58), 8(61)>
      # k_790 = PHI <k_339(55), k_787(58), k_788(61)>
      # .MEM_810 = PHI <.MEM_7(55), .MEM_807(58), .MEM_808(61)>

bb_106 a copy of bb_64:
      # _594 = PHI <0.0(105)>
      # sprv_515 = PHI <sprv_5(105)>
      # i_516 = PHI <i_1(105)>
      # sprv_567 = PHI <sprv_780(105)>
      # k_541 = PHI <k_339(105)>
      # .MEM_619 = PHI <.MEM_7(105)>


In bb_106, a copy of bb_64,
- # sprv_567 = PHI <sprv_780(105)>
  we use the old value sprv_780 instead of the new value sprv_717 set in
bb_105:

- # sprv_515 = PHI <sprv_5(105)>
  we use the old value sprv_5 instead of the new value sprv_437: