re PR middle-end/58041 (Unaligned access to arrays in packed structure)

2013-08-06  Martin Jambor  <mjambor@suse.cz>

	PR middle-end/58041
	* gimple-ssa-strength-reduction.c (replace_ref): Make sure built
	MEM_REF has proper alignment information.

testsuite/
	* gcc.dg/torture/pr58041.c: New test.
	* gcc.target/arm/pr58041.c: Likewise.

From-SVN: r201523

gcc/ChangeLog

+2013-08-06  Martin Jambor  <mjambor@suse.cz>
+
+	PR middle-end/58041
+	* gimple-ssa-strength-reduction.c (replace_ref): Make sure built
+	MEM_REF has proper alignment information.
+
 2013-08-05  Oleg Endo <olegendo@gcc.gnu.org>
 
 	PR other/12081

gcc/gimple-ssa-strength-reduction.c

@@ -1728,11 +1728,23 @@ dump_incr_vec (void)
 static void
 replace_ref (tree *expr, slsr_cand_t c)
 {
-  tree add_expr = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (c->base_expr),
-			       c->base_expr, c->stride);
-  tree mem_ref = fold_build2 (MEM_REF, TREE_TYPE (*expr), add_expr,
-			      double_int_to_tree (c->cand_type, c->index));
-  
+  tree add_expr, mem_ref, acc_type = TREE_TYPE (*expr);
+  unsigned HOST_WIDE_INT misalign;
+  unsigned align;
+
+  /* Ensure the memory reference carries the minimum alignment
+     requirement for the data type.  See PR58041.  */
+  get_object_alignment_1 (*expr, &align, &misalign);
+  if (misalign != 0)
+    align = (misalign & -misalign);
+  if (align < TYPE_ALIGN (acc_type))
+    acc_type = build_aligned_type (acc_type, align);
+
+  add_expr = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (c->base_expr),
+			  c->base_expr, c->stride);
+  mem_ref = fold_build2 (MEM_REF, acc_type, add_expr,
+			 double_int_to_tree (c->cand_type, c->index));
+
   /* Gimplify the base addressing expression for the new MEM_REF tree.  */
   gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
   TREE_OPERAND (mem_ref, 0)

gcc/testsuite/ChangeLog

+2013-08-06  Martin Jambor  <mjambor@suse.cz>
+
+	PR middle-end/58041
+	* gcc.dg/torture/pr58041.c: New test.
+	* gcc.target/arm/pr58041.c: Likewise.
+
 2013-08-06  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/57306

gcc/testsuite/gcc.dg/torture/pr58041.c

+/* { dg-do run } */
+
+typedef long long V
+  __attribute__ ((vector_size (2 * sizeof (long long)), may_alias));
+
+typedef struct S { V v; } P __attribute__((aligned (1)));
+
+struct s
+{
+  char u;
+  V v[2];
+} __attribute__((packed,aligned(1)));
+
+__attribute__((noinline, noclone))
+long long foo(struct s *x, int y, V z)
+{
+  V a = x->v[y];
+  x->v[y] = z;
+  return a[1];
+}
+
+struct s a = {0,{0,0}};
+int main()
+{
+  V v1 = {0,1};
+  V v2 = {0,2};
+
+  if (foo(&a,0,v1) != 0)
+    __builtin_abort();
+  if (foo(&a,0,v2) != 1)
+    __builtin_abort();
+  if (foo(&a,1,v1) != 0)
+    __builtin_abort();
+  return 0;
+}

gcc/testsuite/gcc.target/arm/pr58041.c

+/* { dg-do compile } */
+/* { dg-options "-Os -mno-unaligned-access" } */
+/* { dg-final { scan-assembler "ldrb" } } */
+/* { dg-final { scan-assembler "strb" } } */
+
+struct s
+{
+  char u;
+  long long v[2];
+} __attribute__((packed,aligned(1)));
+
+__attribute__((noinline, noclone))
+long long foo(struct s *x, int y, long long z)
+{
+  long long a = x->v[y];
+  x->v[y] = z;
+  return a;
+}
+
+struct s a = {0,{0,0}};
+int main()
+{
+  if (foo(&a,0,1) != 0)
+    __builtin_abort();
+  if (foo(&a,0,2) != 1)
+    __builtin_abort();
+  if (foo(&a,1,1) != 0)
+    __builtin_abort();
+  return 0;
+}