This backport contains 2 patchs from gcc main stream tree.
The commit id of these patchs list as following in the order of time.

4bf29d15f2e01348a45a1f4e1a135962f123fdd6
0001-AArch64-PR79262-Adjust-vector-cost.patch

27071013521b015d17a2666448f27a6ff0c55aca
0001-Move-EXTRACT_LAST_REDUCTION-costing-to-vectorizable_.patch

diff -Nurp a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
--- a/gcc/config/aarch64/aarch64.c	2020-11-20 04:36:33.988000000 +0800
+++ b/gcc/config/aarch64/aarch64.c	2020-11-20 04:32:20.984000000 +0800
@@ -448,7 +448,7 @@ static const struct cpu_vector_cost gene
   1, /* vec_int_stmt_cost  */
   1, /* vec_fp_stmt_cost  */
   2, /* vec_permute_cost  */
-  1, /* vec_to_scalar_cost  */
+  2, /* vec_to_scalar_cost  */
   1, /* scalar_to_vec_cost  */
   1, /* vec_align_load_cost  */
   1, /* vec_unalign_load_cost  */
diff -Nurp a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
--- a/gcc/tree-vect-loop.c	2020-11-20 04:36:34.016000000 +0800
+++ b/gcc/tree-vect-loop.c	2020-11-20 04:32:20.984000000 +0800
@@ -3926,8 +3926,11 @@ vect_model_reduction_cost (stmt_vec_info
 
   code = gimple_assign_rhs_code (orig_stmt_info->stmt);
 
-  if (reduction_type == EXTRACT_LAST_REDUCTION
-      || reduction_type == FOLD_LEFT_REDUCTION)
+  if (reduction_type == EXTRACT_LAST_REDUCTION)
+    /* No extra instructions are needed in the prologue.  The loop body
+       operations are costed in vectorizable_condition.  */
+    inside_cost = 0;
+  else if (reduction_type == FOLD_LEFT_REDUCTION)
     {
       /* No extra instructions needed in the prologue.  */
       prologue_cost = 0;
diff -Nurp a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
--- a/gcc/tree-vect-stmts.c	2020-11-20 04:36:33.996000000 +0800
+++ b/gcc/tree-vect-stmts.c	2020-11-20 04:32:20.984000000 +0800
@@ -859,7 +859,8 @@ vect_model_simple_cost (stmt_vec_info st
 			enum vect_def_type *dt,
 			int ndts,
 			slp_tree node,
-			stmt_vector_for_cost *cost_vec)
+			stmt_vector_for_cost *cost_vec,
+			vect_cost_for_stmt kind = vector_stmt)
 {
   int inside_cost = 0, prologue_cost = 0;
 
@@ -906,7 +907,7 @@ vect_model_simple_cost (stmt_vec_info st
     }
 
   /* Pass the inside-of-loop statements to the target-specific cost model.  */
-  inside_cost += record_stmt_cost (cost_vec, ncopies, vector_stmt,
+  inside_cost += record_stmt_cost (cost_vec, ncopies, kind,
 				   stmt_info, 0, vect_body);
 
   if (dump_enabled_p ())
@@ -9194,15 +9195,18 @@ vectorizable_condition (stmt_vec_info st
 			     " EXTRACT_LAST_REDUCTION.\n");
 	  LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo) = false;
 	}
-      if (expand_vec_cond_expr_p (vectype, comp_vectype,
-				     cond_code))
-	{
-	  STMT_VINFO_TYPE (stmt_info) = condition_vec_info_type;
-	  vect_model_simple_cost (stmt_info, ncopies, dts, ndts, slp_node,
-				  cost_vec);
-	  return true;
-	}
-      return false;
+
+      vect_cost_for_stmt kind = vector_stmt;
+      if (reduction_type == EXTRACT_LAST_REDUCTION)
+        /* Count one reduction-like operation per vector.  */
+        kind = vec_to_scalar;
+      else if (!expand_vec_cond_expr_p (vectype, comp_vectype, cond_code))
+        return false;
+
+      STMT_VINFO_TYPE (stmt_info) = condition_vec_info_type;
+      vect_model_simple_cost (stmt_info, ncopies, dts, ndts, slp_node,
+                                                 cost_vec, kind);
+      return true;
     }
 
   /* Transform.  */