[Bug tree-optimization/91063] [10 Regression] ICE in set_vinfo_for_stmt, at tree-vectorizer.c:676

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91063

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2019-07-03
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Reduced testcase -O2 -fopenmp-simd -mavx512f:
struct S { void *s; };

int
foo (struct S *x)
{
  int r = 0;
  int i;
#pragma omp simd reduction (+ : r)
  for (i = 0; i < 64; ++i)
    r += (int) (x->s != 0);
  return r;
}

I believe this has been introduced with r272623, but haven't verified that yet.

Untested fix below.  vect_init_vector_1 inserts the stmt read from stmts
sequence into other spots, so it is unhealthy if we iterate using iterator that
contains it, it can very well create stmt referencing itself in ->next.
--- gcc/tree-vect-stmts.c.jj    2019-07-03 10:24:33.463768431 +0200
+++ gcc/tree-vect-stmts.c       2019-07-03 12:35:48.998435660 +0200
@@ -1496,15 +1496,19 @@ vect_init_vector (stmt_vec_info stmt_inf
                   promotion of invariant/external defs.  */
                val = gimple_convert (&stmts, TREE_TYPE (type), val);
              for (gimple_stmt_iterator gsi2 = gsi_start (stmts);
-                  !gsi_end_p (gsi2); gsi_next (&gsi2))
-               vect_init_vector_1 (stmt_info, gsi_stmt (gsi2), gsi);
+                  !gsi_end_p (gsi2); )
+               {
+                 init_stmt = gsi_stmt (gsi2);
+                 gsi_remove (&gsi2, false);
+                 vect_init_vector_1 (stmt_info, init_stmt, gsi);
+               }
            }
        }
       val = build_vector_from_val (type, val);
     }

   new_temp = vect_get_new_ssa_name (type, vect_simple_var, "cst_");
-  init_stmt = gimple_build_assign  (new_temp, val);
+  init_stmt = gimple_build_assign (new_temp, val);
   vect_init_vector_1 (stmt_info, init_stmt, gsi);
   return new_temp;
 }