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[patch] Fix PR middle-end/58570


this is a regression on the mainline introduced by my tree-ssa-alias.c change:

2013-04-17  Eric Botcazou  <>

	* tree-ssa-alias.c (nonoverlapping_component_refs_of_decl_p): New.
	(decl_refs_may_alias_p): Add REF1 and REF2 parameters.
	Use nonoverlapping_component_refs_of_decl_p to disambiguate component
	(refs_may_alias_p_1): Adjust call to decl_refs_may_alias_p.
	* tree-streamer.c (record_common_node): Adjust reference in comment.

Unlike its model nonoverlapping_component_refs_p from alias.c, the predicate 
nonoverlapping_component_refs_of_decl_p considers that different fields in the 
same structure cannot overlap.  While that's true in GIMPLE, that's false in 
RTL for bitfields and tree-ssa-alias.c is also queried from RTL nowadays...

Therefore the attached patch just copies the missing bits from the former to 
the latter.  Tested on x86_64-suse-linux, OK for the mainline?

2013-10-08  Eric Botcazou  <>

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

2013-10-08  Eric Botcazou  <>

	* gcc.c-torture/execute/pr58570.c: New test.

Eric Botcazou
#pragma pack(1)
struct S
  int f0:15;
  int f1:29;

int e = 1, i;
static struct S d[6];

main (void)
  if (e)
      d[i].f0 = 1;
      d[i].f1 = 1;
  if (d[0].f1 != 1)
    __builtin_abort ();
  return 0;
Index: tree-ssa-alias.c
--- tree-ssa-alias.c	(revision 203241)
+++ tree-ssa-alias.c	(working copy)
@@ -803,12 +803,13 @@ nonoverlapping_component_refs_of_decl_p
       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, unless they
+	 are both bitfields and we are at the RTL level.  */
       if (field1 != field2)
 	  component_refs1.release ();
 	  component_refs2.release ();
-	  return true;
+	  return !(DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2));

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