Index: gcc/expr.c
===================================================================
--- gcc/expr.c	(revision 202778)
+++ gcc/expr.c	(working copy)
@@ -9878,7 +9878,7 @@
 			  && modifier != EXPAND_STACK_PARM
 			  ? target : NULL_RTX),
 			 VOIDmode,
-			 modifier == EXPAND_SUM ? EXPAND_NORMAL : modifier);
+			 EXPAND_MEMORY);
 
 	/* If the bitfield is volatile, we want to access it in the
 	   field's mode, not the computed mode.
Index: gcc/testsuite/gcc.dg/torture/pr57748-3.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr57748-3.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr57748-3.c	(revision 0)
@@ -0,0 +1,40 @@
+/* PR middle-end/57748 */
+/* { dg-do run } */
+/* wrong code in expand_expr_real_1.  */
+
+#include <stdlib.h>
+
+extern void abort (void);
+
+typedef long long V
+  __attribute__ ((vector_size (2 * sizeof (long long)), may_alias));
+
+typedef struct S { V a; V b[0]; } P __attribute__((aligned (1)));
+
+struct __attribute__((packed)) T { char c; P s; };
+
+void __attribute__((noinline, noclone))
+check (P *p)
+{
+  if (p->b[0][0] != 3 || p->b[0][1] != 4)
+    abort ();
+}
+
+void __attribute__((noinline, noclone))
+foo (struct T *t)
+{
+  V a = { 3, 4 };
+  t->s.b[0] = a;
+}
+
+int
+main ()
+{
+  struct T *t = (struct T *) calloc (128, 1);
+
+  foo (t);
+  check (&t->s);
+
+  free (t);
+  return 0;
+}