https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120941
--- Comment #37 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Richard Biener from comment #35)
> (In reply to H.J. Lu from comment #33)
> > Created attachment 61995 [details]
> > An updated patch
> >
> > Please try this.
>
> Looking at the patch I do wonder about
>
> static void
> ix86_place_single_vector_set (rtx dest, rtx src, bitmap bbs,
> rtx inner_scalar = nullptr)
> {
> basic_block bb = nearest_common_dominator_for_set (CDI_DOMINATORS, bbs);
> while (bb->loop_father->latch
> != EXIT_BLOCK_PTR_FOR_FN (cfun))
> bb = get_immediate_dominator (CDI_DOMINATORS,
> bb->loop_father->header);
>
> when the nearest common dominator is a BB in a loop nest like
>
> loop {
> loop {
> }
>
> loop {
> BB;
> }
> BB';
> }
>
> this will skip an arbitrary number of earlier sibling loops. I think
> if we want to do such additional hoisting at all - for a splat of a
> non-constant we have to ensure the set of the source we splat is still
> dominating the insertion point (where's that done?) - it IMO only
> makes sense (without extra costing) to hoist the set out of a perfect
> nest, thus never across earlier sibling loops. Even for BB' this is
> likely problematic.
Since my patch works, I'd like to keep it as is. Will it work for you?
