[Bug tree-optimization/91822] [10 Regression] FAIL: gcc.dg/pr88031.c (internal compiler error)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91822

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rsandifo at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So I belive we can fix this with

Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c        (revision 275972)
+++ gcc/tree-vect-loop.c        (working copy)
@@ -6534,9 +6534,10 @@ vectorizable_reduction (stmt_vec_info st
     {
       /* Only call during the analysis stage, otherwise we'll lose
         STMT_VINFO_TYPE.  */
-      gcc_assert (reduc_index > 0);
+      gcc_assert (nested_cycle || reduc_index > 0);
       if (!vec_stmt && !vectorizable_condition (stmt_info, gsi, NULL,
-                                               reduc_index, NULL, cost_vec))
+                                               nested_cycle ? 0 : reduc_index,
+                                               NULL, cost_vec))
         {
           if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,

not sure what in the end exposed it but nested cycle vectorization treats
the stmts as regular stmt, not really caring about reduc_index.  I'll have to
dig (tomorrow) what we've done with the testcase before but it's indeed
the case that relaxing nested cycle things exposes "interesting" paths in
vectorizable_reduction.  One of my goals is to split that out, but I'm doing
baby steps in this code...