--- gcc/expr.c	2013-08-06 00:09:45.000000000 +0200
+++ gcc/expr.c	2013-09-10 08:23:09.570951685 +0200
@@ -4691,8 +4691,6 @@ expand_assignment (tree to, tree from, b
       int unsignedp;
       int volatilep = 0;
       tree tem;
-      bool misalignp;
-      rtx mem = NULL_RTX;
 
       push_temp_slots ();
       tem = get_inner_reference (to, &bitsize, &bitpos, &offset, &mode1,
@@ -4702,40 +4700,7 @@ expand_assignment (tree to, tree from, b
 	  && DECL_BIT_FIELD_TYPE (TREE_OPERAND (to, 1)))
 	get_bit_range (&bitregion_start, &bitregion_end, to, &bitpos, &offset);
 
-      /* If we are going to use store_bit_field and extract_bit_field,
-	 make sure to_rtx will be safe for multiple use.  */
-      mode = TYPE_MODE (TREE_TYPE (tem));
-      if (TREE_CODE (tem) == MEM_REF
-	  && mode != BLKmode
-	  && ((align = get_object_alignment (tem))
-	      < GET_MODE_ALIGNMENT (mode))
-	  && ((icode = optab_handler (movmisalign_optab, mode))
-	      != CODE_FOR_nothing))
-	{
-	  struct expand_operand ops[2];
-
-	  misalignp = true;
-	  to_rtx = gen_reg_rtx (mode);
-	  mem = expand_expr (tem, NULL_RTX, VOIDmode, EXPAND_WRITE);
-
-	  /* If the misaligned store doesn't overwrite all bits, perform
-	     rmw cycle on MEM.  */
-	  if (bitsize != GET_MODE_BITSIZE (mode))
-	    {
-	      create_input_operand (&ops[0], to_rtx, mode);
-	      create_fixed_operand (&ops[1], mem);
-	      /* The movmisalign<mode> pattern cannot fail, else the assignment
-		 would silently be omitted.  */
-	      expand_insn (icode, 2, ops);
-
-	      mem = copy_rtx (mem);
-	    }
-	}
-      else
-	{
-	  misalignp = false;
-	  to_rtx = expand_expr (tem, NULL_RTX, VOIDmode, EXPAND_WRITE);
-	}
+      to_rtx = expand_expr (tem, NULL_RTX, VOIDmode, EXPAND_WRITE);
 
       /* If the bitfield is volatile, we want to access it in the
 	 field's mode, not the computed mode.
@@ -4773,6 +4738,8 @@ expand_assignment (tree to, tree from, b
 	  if (MEM_P (to_rtx)
 	      && GET_MODE (to_rtx) == BLKmode
 	      && GET_MODE (XEXP (to_rtx, 0)) != VOIDmode
+	      && bitregion_start == 0
+	      && bitregion_end == 0
 	      && bitsize > 0
 	      && (bitpos % bitsize) == 0
 	      && (bitsize % GET_MODE_ALIGNMENT (mode1)) == 0
@@ -4874,17 +4841,6 @@ expand_assignment (tree to, tree from, b
 				  get_alias_set (to), nontemporal);
 	}
 
-      if (misalignp)
-	{
-	  struct expand_operand ops[2];
-
-	  create_fixed_operand (&ops[0], mem);
-	  create_input_operand (&ops[1], to_rtx, mode);
-	  /* The movmisalign<mode> pattern cannot fail, else the assignment
-	     would silently be omitted.  */
-	  expand_insn (icode, 2, ops);
-	}
-
       if (result)
 	preserve_temp_slots (result);
       pop_temp_slots ();
@@ -9905,7 +9861,7 @@ expand_expr_real_1 (tree exp, rtx target
 			  && 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.
--- gcc/testsuite/gcc.dg/torture/pr57748-1.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-1.c	2013-09-06 08:38:03.718686940 +0200
@@ -0,0 +1,49 @@
+/* PR middle-end/57748 */
+/* { dg-do run } */
+/* ICE in expand_assignment:
+   misalignp == true, !MEM_P (to_rtx), offset != 0,
+   => gcc_assert (TREE_CODE (offset) == INTEGER_CST) */
+
+#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 (struct T *t)
+{
+  if (t->s.b[0][0] != 3 || t->s.b[0][1] != 4)
+    abort ();
+}
+
+int __attribute__((noinline, noclone))
+get_i (void)
+{
+  return 0;
+}
+
+void __attribute__((noinline, noclone))
+foo (P *p)
+{
+  V a = { 3, 4 };
+  int i = get_i ();
+  p->b[i] = a;
+}
+
+int
+main ()
+{
+  struct T *t = (struct T *) calloc (128, 1);
+
+  foo (&t->s);
+  check (t);
+
+  free (t);
+  return 0;
+}
--- gcc/testsuite/gcc.dg/torture/pr57748-2.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-2.c	2013-09-06 08:38:03.718686940 +0200
@@ -0,0 +1,43 @@
+/* PR middle-end/57748 */
+/* { dg-do run } */
+/* wrong code in expand_assignment:
+   misalignp == true, !MEM_P (to_rtx),
+   offset == 0, bitpos >= GET_MODE_PRECISION,
+   => result = NULL.  */
+
+#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 (struct T *t)
+{
+  if (t->s.b[0][0] != 3 || t->s.b[0][1] != 4)
+    abort ();
+}
+
+void __attribute__((noinline, noclone))
+foo (P *p)
+{
+  V a = { 3, 4 };
+  p->b[0] = a;
+}
+
+int
+main ()
+{
+  struct T *t = (struct T *) calloc (128, 1);
+
+  foo (&t->s);
+  check (t);
+
+  free (t);
+  return 0;
+}
--- gcc/testsuite/gcc.dg/torture/pr57748-3.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-3.c	2013-09-13 12:46:34.456009224 +0200
@@ -0,0 +1,48 @@
+/* PR middle-end/57748 */
+/* { dg-do run } */
+/* data store race in expand_assignment:
+   misalignp == true, !MEM_P (to_rtx),
+   offset == 0, bitsize < GET_MODE_BITSIZE,
+   => rmw cycle on MEM.  */
+
+extern void abort (void);
+
+typedef long long V
+  __attribute__ ((vector_size (2 * sizeof (long long)), may_alias));
+
+union x
+{
+  long long a;
+  float b;
+} __attribute__((aligned (1)));
+
+struct s
+{
+  union x xx[0];
+  V x;
+} __attribute__((packed));
+
+void __attribute__((noinline, noclone))
+check (union x *xx)
+{
+  if (xx[0].b != 3.14F || xx[1].a != 0x123456789ABCDEF)
+    abort ();
+}
+
+void __attribute__((noinline, noclone))
+foo (struct s * x)
+{
+  x->xx[0].a = -1;
+  x->xx[0].b = 3.14F;
+  x->x[1] = 0x123456789ABCDEF;
+}
+
+struct s ss;
+
+int
+main ()
+{
+  foo (&ss);
+  check (ss.xx);
+  return 0;
+}
--- gcc/testsuite/gcc.dg/torture/pr57748-3a.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-3a.c	2013-09-13 12:44:47.140007819 +0200
@@ -0,0 +1,7 @@
+/* PR middle-end/57748 */
+/* { dg-do compile } */
+/* { dg-options "-msse2" } */
+/* { dg-require-effective-target sse2 } */
+/* { dg-final { scan-assembler-not "movdqu" } } */
+/* { dg-final { scan-assembler-not "movdqa" } } */
+#include "pr57748-3.c"
--- gcc/testsuite/gcc.dg/torture/pr57748-4.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-4.c	2013-09-13 12:46:13.412008952 +0200
@@ -0,0 +1,49 @@
+/* PR middle-end/57748 */
+/* { dg-do run } */
+/* wrong code in expand_expr_real_1:
+   read whole structure instead of only one member.  */
+
+extern void abort (void);
+
+typedef long long V
+  __attribute__ ((vector_size (2 * sizeof (long long)), may_alias));
+
+union x
+{
+  long long a;
+  float b;
+} __attribute__((aligned (1)));
+
+struct s
+{
+  union x xx[0];
+  V x;
+} __attribute__((packed));
+
+void __attribute__((noinline, noclone))
+check (struct s *x)
+{
+  if (x->xx[0].b != 3.14F || x->xx[1].a != 0x123456789ABCDEF)
+    abort ();
+  if (x->xx[2].b != 3.14F || x->xx[3].a != 0x123456789ABCDEF)
+    abort ();
+}
+
+void __attribute__((noinline, noclone))
+foo (struct s * x)
+{
+  x->xx[0].a = -1;
+  x->xx[0].b = 3.14F;
+  x->x[1] = 0x123456789ABCDEF;
+}
+
+struct s ss[2];
+
+int
+main ()
+{
+  foo (ss);
+  foo (ss+1);
+  check (ss);
+  return 0;
+}
--- gcc/testsuite/gcc.dg/torture/pr57748-4a.c	1970-01-01 01:00:00.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr57748-4a.c	2013-09-13 12:46:02.812008813 +0200
@@ -0,0 +1,7 @@
+/* PR middle-end/57748 */
+/* { dg-do compile } */
+/* { dg-options "-msse2" } */
+/* { dg-require-effective-target sse2 } */
+/* { dg-final { scan-assembler-not "movdqu" } } */
+/* { dg-final { scan-assembler-not "movdqa" } } */
+#include "pr57748-4.c"