2013-03-05  Jakub Jelinek  <jakub@redhat.com>

	PR debug/56510
	* cfgexpand.c (avoid_complex_debug_insns): New function.
	(expand_debug_locations): Call it.

	* gcc.dg/pr56510.c: New test.

--- gcc/cfgexpand.c.jj	2013-01-25 21:02:47.000000000 +0100
+++ gcc/cfgexpand.c	2013-03-05 14:32:38.076308346 +0100
@@ -3704,6 +3704,54 @@ expand_debug_source_expr (tree exp)
   return op0;
 }
 
+/* Ensure INSN_VAR_LOCATION_LOC (insn) doesn't have unbound complexity.
+   Allow 4 levels of rtl nesting for most rtl codes, and if we see anything
+   deeper than that, create DEBUG_EXPRs and emit DEBUG_INSNs before INSN.  */
+
+static void
+avoid_complex_debug_insns (rtx insn, rtx *exp_p, int depth)
+{
+  rtx exp = *exp_p;
+  if (exp == NULL_RTX)
+    return;
+  if ((OBJECT_P (exp) && !MEM_P (exp)) || GET_CODE (exp) == CLOBBER)
+    return;
+
+  if (depth == 4)
+    {
+      /* Create DEBUG_EXPR (and DEBUG_EXPR_DECL).  */
+      rtx dval = make_debug_expr_from_rtl (exp);
+
+      /* Emit a debug bind insn before INSN.  */
+      rtx bind = gen_rtx_VAR_LOCATION (GET_MODE (exp),
+				       DEBUG_EXPR_TREE_DECL (dval), exp,
+				       VAR_INIT_STATUS_INITIALIZED);
+
+      emit_debug_insn_before (bind, insn);
+      *exp_p = dval;
+      return;
+    }
+
+  const char *format_ptr = GET_RTX_FORMAT (GET_CODE (exp));
+  int i, j;
+  for (i = 0; i < GET_RTX_LENGTH (GET_CODE (exp)); i++)
+    switch (*format_ptr++)
+      {
+      case 'e':
+	avoid_complex_debug_insns (insn, &XEXP (exp, i), depth + 1);
+	break;
+
+      case 'E':
+      case 'V':
+	for (j = 0; j < XVECLEN (exp, i); j++)
+	  avoid_complex_debug_insns (insn, &XVECEXP (exp, i, j), depth + 1);
+	break;
+
+      default:
+	break;
+      }
+}
+
 /* Expand the _LOCs in debug insns.  We run this after expanding all
    regular insns, so that any variables referenced in the function
    will have their DECL_RTLs set.  */
@@ -3724,7 +3772,7 @@ expand_debug_locations (void)
     if (DEBUG_INSN_P (insn))
       {
 	tree value = (tree)INSN_VAR_LOCATION_LOC (insn);
-	rtx val;
+	rtx val, prev_insn, insn2;
 	enum machine_mode mode;
 
 	if (value == NULL_TREE)
@@ -3753,6 +3801,9 @@ expand_debug_locations (void)
 	  }
 
 	INSN_VAR_LOCATION_LOC (insn) = val;
+	prev_insn = PREV_INSN (insn);
+	for (insn2 = insn; insn2 != prev_insn; insn2 = PREV_INSN (insn2))
+	  avoid_complex_debug_insns (insn2, &INSN_VAR_LOCATION_LOC (insn2), 0);
       }
 
   flag_strict_aliasing = save_strict_alias;
--- gcc/testsuite/gcc.dg/pr56510.c.jj	2013-03-05 14:34:32.600807432 +0100
+++ gcc/testsuite/gcc.dg/pr56510.c	2013-03-05 14:36:01.324412449 +0100
@@ -0,0 +1,37 @@
+/* PR debug/56510 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+
+struct S { unsigned long s1; void **s2[0]; };
+void **a, **b, **c, **d, **e, **f;
+
+static void **
+baz (long x, long y)
+{
+  void **s = f;
+  *f = (void **) (y << 8 | (x & 0xff));
+  f += y + 1;
+  return s;
+}
+
+void bar (void);
+void
+foo (void)
+{
+  void **g = b[4];
+  a = b[2];
+  b = b[1];
+  g[2] = e;
+  void **h
+    = ((void **************************)
+       a)[1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][66];
+  void **i = ((struct S *) h)->s2[4];
+  d = baz (4, 3);
+  d[1] = b;
+  d[2] = a;
+  d[3] = bar;
+  b = d;
+  g[1] = i[2];
+  a = g;
+  ((void (*) (void)) (i[1])) ();
+}