diff --git a/gcc/testsuite/gcc.dg/pr123656.c b/gcc/testsuite/gcc.dg/pr123656.c
new file mode 100644
index 00000000000..98439857c49
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr123656.c
@@ -0,0 +1,21 @@
+/* PR tree-optimization/123656 */
+/* { dg-do run } */
+/* { dg-options "-Og -Wno-psabi" } */
+
+#define C 210
+
+typedef __attribute__((__vector_size__ (2))) unsigned char V;
+
+V
+foo (V v)
+{
+  return v * C;
+}
+
+int
+main ()
+{
+  V x = foo ((V) {1, 1});
+  if (x[0] != C || x[1] != C)
+    __builtin_abort ();
+}
diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index d34d2c5fa48..77066bbb2e1 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -643,9 +643,9 @@ expand_vector_mult (gimple_stmt_iterator *gsi, tree type, tree op0,
 				       LSHIFT_EXPR);
 	      break;
 	    case alg_add_t_m2:
-	       tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
+	      tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
 	      accumulator = gimplify_build2 (gsi, PLUS_EXPR, vectype, tmp_var,
-					    accumulator);
+					     accumulator);
 	      break;
 	    case alg_sub_t_m2:
 	      tmp_var = add_shift (gsi, vectype, op0, shifts, LSHIFT_EXPR);
@@ -674,7 +674,7 @@ expand_vector_mult (gimple_stmt_iterator *gsi, tree type, tree op0,
 	      tmp_var = add_shift (gsi, vectype, accumulator, shifts,
 				   LSHIFT_EXPR);
 	      accumulator = gimplify_build2 (gsi, MINUS_EXPR, vectype,
-					     accumulator, tmp_var);
+					     tmp_var, accumulator);
 	      break;
 	    default:
 	      gcc_unreachable ();