[Bug tree-optimization/123343] Loop unrolling before vectorization produces suboptimal RISC-V code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123343

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's in-line with the previous comments - SLP for VLA ISAs is difficult, but we
do not cost single-lane vs. multi-lane SLP but only fall back to single-lane
SLP if analysis of multi-lane SLP failed.  There's "heuristics" with respect to
load/store-lane vs. SLP but indeed currently no heuristics that would apply
this to reductions (but there's SLP loads there?).