https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94043
--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Kewen Lin from comment #12)
> Created attachment 48122 [details]
> ppc64le tested patch
>
> Thanks Richi!
>
> A patch draft attached to ensure on the right track, also
> bootstrapped/regresstested. I tried to reproduce the case that the stmts for
> lane extracting is empty (due to folding) with test cases associated in that
> old commit but failed. I think we don't need to deal with it? The new copy
> assignment instead of the phi could not be caught by the LC-PHI check in
> expand_simple_operations.
+ /* Find all SSA NAMEs in stmts which is defined in current loop, create
+ PHIs for them, and replace them with phi results accordingly. */
+ for (gsi = gsi_start (stmts); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple *stmt = gsi_stmt (gsi);
+ update_stmt (stmt);
+
...
should not be necessary. What's missing in your patch is that when the
current code has computed vec_lhs it needs to create a LC PHI node for it
_before_ computing the lane extraction and instead use vec_lhs' there.
