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

[rsandifo at gcc dot gnu.org]

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

--- Comment #5 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> (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. 

Yeah, started wondering about that later too...

> 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.

Would be great if it works.  Will give it a spin later on SVE,
although I guess in some ways that probably exercises SLP even
less (at least in length-agnostic mode).