[Bug tree-optimization/94261] [10 Regression] ICE in vect_get_vec_def_for_operand_1 for 3-element condition reduction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94261

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> when placing gcc_unreachable () at the swapping place and most testcases
> still pass when removing the IL operand swapping, only vect-cselim-1.c
> runfails (investigating).

Ah, SLP ultimately fails here so the scalar IL is broken by the operation
code adjustment.  In the end we should be able to avoid doing tree code
adjustments as well since we're swapping to make the code the same
as the first stmts code and we only ever look at the first scalar stmt
during SLP code-gen/analysis. 

So, it appears to work to comment _all_ of the code in
vect_get_and_check_slp_defs (including the reduc-idx adjustment).

But again, test coverage is probably bad.