[Bug tree-optimization/121768] ICE on valid code at -O{2,3} with "-fno-tree-dce -fno-inline" on x86_64-linux-gnu: in vect_build_slp_tree_2, at tree-vect-slp.cc:3217

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121768

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2025-09-03
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
            Version|unknown                     |16.0
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot 
gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
t.c:4:10: note:   Analyze phi: a_lsm.13_9 = PHI <_10(9), a_lsm.13_18(3)>
t.c:4:10: note:   detected double reduction: _10 = PHI <_5(5)>
t.c:4:10: note:   Detected double reduction.
...
t.c:4:10: note:   Analyze phi: a_lsm.13_7 = PHI <_5(10), a_lsm.13_9(4)>
t.c:4:10: note:   Access function of PHI: a_lsm.13_7
t.c:4:10: note:   Analyze phi: ivtmp_34 = PHI <ivtmp_33(10), 2(4)>
t.c:4:10: note:   Access function of PHI: {2, +, 4294967295}_2
t.c:4:10: note:   step: 4294967295,  init: 2
t.c:4:10: note:   Detected induction.
t.c:4:10: note:   Analyze phi: a_lsm.13_7 = PHI <_5(10), a_lsm.13_9(4)>
t.c:4:10: note:   reduction path:
t.c:4:10: note:   reduction: unknown pattern
t.c:4:10: missed:   Unknown def-use cycle pattern.

this keeps the not detected double-reduction active.  I guess it's time to
refactor this a bit...