[gcc r15-1005] Avoid inserting after a GIMPLE_COND with SLP and early break

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:0592000aeed84d47040946a125154b3c46d7c84f

commit r15-1005-g0592000aeed84d47040946a125154b3c46d7c84f
Author: Richard Biener <rguent...@suse.de>
Date:   Mon May 27 14:40:27 2024 +0200

    Avoid inserting after a GIMPLE_COND with SLP and early break
    
    When vectorizing an early break loop with LENs (do we miss some
    check here to disallow this?) we can end up deciding to insert
    stmts after a GIMPLE_COND when doing SLP scheduling and trying
    to be conservative with placing of stmts only dependent on
    the implicit loop mask/len.  The following avoids this, I guess
    it's not perfect but it does the job fixing some observed
    RISC-V regression.
    
            * tree-vect-slp.cc (vect_schedule_slp_node): For mask/len
            loops make sure to not advance the insertion iterator
            beyond a GIMPLE_COND.

Diff:
---
 gcc/tree-vect-slp.cc | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index bf1f467f53f..11ec82086fc 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -9650,7 +9650,12 @@ vect_schedule_slp_node (vec_info *vinfo,
       else
        {
          si = gsi_for_stmt (last_stmt);
-         gsi_next (&si);
+         /* When we're getting gsi_after_labels from the starting
+            condition of a fully masked/len loop avoid insertion
+            after a GIMPLE_COND that can appear as the only header
+            stmt with early break vectorization.  */
+         if (gimple_code (last_stmt) != GIMPLE_COND)
+           gsi_next (&si);
        }
     }