re PR middle-end/58570 (wrong code for bitfields at -O2 and above)

	PR middle-end/58570
	* tree-ssa-alias.c (nonoverlapping_component_refs_of_decl_p): Return
	false if both components are bitfields.

From-SVN: r203315

gcc/ChangeLog

+2013-10-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR middle-end/58570
+	* tree-ssa-alias.c (nonoverlapping_component_refs_of_decl_p): Return
+	false if both components are bitfields.
+
 2013-10-09  Alex Velenko  <Alex.Velenko@arm.com>
 
 	* config/aarch64/arm_neon.h (vclz_s8, vclz_s16, vclz_s32)

gcc/testsuite/ChangeLog

+2013-10-09  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.c-torture/execute/pr58570.c: New test.
+
 2013-10-09  Alex Velenko  <Alex.Velenko@arm.com>
 
 	* gcc.target/aarch64/vclz.c: New testcase.

gcc/testsuite/gcc.c-torture/execute/pr58570.c

+#pragma pack(1)
+struct S
+{
+  int f0:15;
+  int f1:29;
+};
+
+int e = 1, i;
+static struct S d[6];
+
+int
+main (void)
+{
+  if (e)
+    {
+      d[i].f0 = 1;
+      d[i].f1 = 1;
+    }
+  if (d[0].f1 != 1)
+    __builtin_abort ();
+  return 0;
+}

gcc/tree-ssa-alias.c

@@ -803,12 +803,13 @@ nonoverlapping_component_refs_of_decl_p (tree ref1, tree ref2)
       if (type1 != type2 || TREE_CODE (type1) != RECORD_TYPE)
 	 goto may_overlap;
 
-      /* Different fields of the same record type cannot overlap.  */
+      /* Different fields of the same record type cannot overlap.
+	 ??? Bitfields can overlap at RTL level so punt on them.  */
       if (field1 != field2)
 	{
 	  component_refs1.release ();
 	  component_refs2.release ();
-	  return true;
+	  return !(DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2));
 	}
     }