[Bug tree-optimization/104112] [12 Regression] ICE with -Ofast -march=armv8.2-a+sve -msve-vector-bits=512 since r12-2292-g1dd3f21095858fbfd3e28a149578d5fb67e75f95

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104112

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
The following adds such verification

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 0fe3529b2d1..6ce33f3cef0 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -4979,9 +4979,20 @@ vect_find_reusable_accumulator (loop_vec_info
loop_vinfo,
   /* Handle the case where we can reduce wider vectors to narrower ones.  */
   tree vectype = STMT_VINFO_VECTYPE (reduc_info);
   tree old_vectype = TREE_TYPE (accumulator->reduc_input);
+  unsigned HOST_WIDE_INT m;
   if (!constant_multiple_p (TYPE_VECTOR_SUBPARTS (old_vectype),
-                           TYPE_VECTOR_SUBPARTS (vectype)))
+                           TYPE_VECTOR_SUBPARTS (vectype), &m))
     return false;
+  /* Check the intermediate vector types are available.  */
+  while (m > 2)
+    {
+      m /= 2;
+      tree intermediate_vectype = get_related_vectype_for_scalar_type
+       (TYPE_MODE (vectype), TREE_TYPE (vectype),
+        exact_div (TYPE_VECTOR_SUBPARTS (old_vectype), m));
+      if (!intermediate_vectype)
+       return false;
+    }

   /* Non-SLP reductions might apply an adjustment after the reduction
      operation, in order to simplify the initialization of the accumulator.