[PATCH] Fix PR52406

[Richard Guenther <rguenther at suse dot de>]

I am testing the following patch to fix PR52406.  We cannot simply
feed DR_BASE_OBJECT to the alias-oracle as it does not reflect
a real memory access.  Only if we query two 'structurally compatible'
references we may do this.  So the following patch reverts to
using DR_REF instead and improves data-ref index disambiguation
by handling COMPONENT_REFs as extra access dimension (similar to how
we handle REALPART/IMAGPART_EXPR).

Bootstrap / regtest pending on x86_64-unknown-linux-gnu.

Richard.

2012-02-28  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/52406
	* tree-data-ref.c (dr_analyze_indices): For outer COMPONENT_REFs
	add indices to allow their disambiguation.
	(dr_may_alias_p): Use DR_REF for querying the alias oracle.
	(compute_affine_dependence): Make dumps easier to read and
	more verbose.

	* gcc.dg/torture/pr52406.c: New testcase.

Index: gcc/tree-data-ref.c
===================================================================
*** gcc/tree-data-ref.c	(revision 184622)
--- gcc/tree-data-ref.c	(working copy)
*************** dr_analyze_indices (struct data_referenc
*** 886,891 ****
--- 886,908 ----
        VEC_safe_push (tree, heap, access_fns, integer_one_node);
      }
  
+   /* For outermost COMPONENT_REFs of records (but not unions!) use the
+      FIELD_DECL offset as constant access function so we can
+      disambiguate a[i].f1 and a[i].f2.  */
+   while (TREE_CODE (ref) == COMPONENT_REF
+ 	 && TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 0))) == RECORD_TYPE)
+     {
+       tree off = component_ref_field_offset (ref);
+       off = size_binop (PLUS_EXPR,
+ 			size_binop (MULT_EXPR,
+ 				    fold_convert (bitsizetype, off),
+ 				    bitsize_int (BITS_PER_UNIT)),
+ 			DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1)));
+       ref = TREE_OPERAND (ref, 0);
+       VEC_safe_push (tree, heap, access_fns, off);
+       continue;
+     }
+ 
    /* Analyze access functions of dimensions we know to be independent.  */
    aref = &ref;
    while (handled_component_p (*aref))
*************** bool
*** 1325,1332 ****
  dr_may_alias_p (const struct data_reference *a, const struct data_reference *b,
  		bool loop_nest)
  {
!   tree addr_a = DR_BASE_OBJECT (a);
!   tree addr_b = DR_BASE_OBJECT (b);
  
    /* If we are not processing a loop nest but scalar code we
       do not need to care about possible cross-iteration dependences
--- 1342,1349 ----
  dr_may_alias_p (const struct data_reference *a, const struct data_reference *b,
  		bool loop_nest)
  {
!   tree addr_a = DR_REF (a);
!   tree addr_b = DR_REF (b);
  
    /* If we are not processing a loop nest but scalar code we
       do not need to care about possible cross-iteration dependences
*************** compute_affine_dependence (struct data_d
*** 4049,4059 ****
    if (dump_file && (dump_flags & TDF_DETAILS))
      {
        fprintf (dump_file, "(compute_affine_dependence\n");
!       fprintf (dump_file, "  (stmt_a = \n");
!       print_gimple_stmt (dump_file, DR_STMT (dra), 0, 0);
!       fprintf (dump_file, ")\n  (stmt_b = \n");
!       print_gimple_stmt (dump_file, DR_STMT (drb), 0, 0);
!       fprintf (dump_file, ")\n");
      }
  
    /* Analyze only when the dependence relation is not yet known.  */
--- 4066,4075 ----
    if (dump_file && (dump_flags & TDF_DETAILS))
      {
        fprintf (dump_file, "(compute_affine_dependence\n");
!       fprintf (dump_file, "  stmt_a: ");
!       print_gimple_stmt (dump_file, DR_STMT (dra), 0, TDF_SLIM);
!       fprintf (dump_file, "  stmt_b: ");
!       print_gimple_stmt (dump_file, DR_STMT (drb), 0, TDF_SLIM);
      }
  
    /* Analyze only when the dependence relation is not yet known.  */
*************** compute_affine_dependence (struct data_d
*** 4129,4135 ****
      }
  
    if (dump_file && (dump_flags & TDF_DETAILS))
!     fprintf (dump_file, ")\n");
  }
  
  /* Compute in DEPENDENCE_RELATIONS the data dependence graph for all
--- 4145,4158 ----
      }
  
    if (dump_file && (dump_flags & TDF_DETAILS))
!     {
!       if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
! 	fprintf (dump_file, ") -> no dependence\n");
!       else if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
! 	fprintf (dump_file, ") -> dependence analysis failed\n");
!       else
! 	fprintf (dump_file, ")\n");
!     }
  }
  
  /* Compute in DEPENDENCE_RELATIONS the data dependence graph for all
Index: gcc/testsuite/gcc.dg/torture/pr52406.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr52406.c	(revision 0)
--- gcc/testsuite/gcc.dg/torture/pr52406.c	(revision 0)
***************
*** 0 ****
--- 1,29 ----
+ /* { dg-do run } */
+ 
+ extern void abort (void);
+ struct { int f1; } a[2];
+ 
+ int *b, *const k = &a[1].f1;
+ static int **c = &b;
+ 
+ int e, f, d;
+ 
+ int
+ main ()
+ {
+   int **l = &b;
+   *l = k;
+   for (; d <= 0; d++)
+     {
+       int *j = &e;
+       **c = 1;
+       *l = k;
+       *k ^= 0;
+       f = **l;
+       *j = f;
+     }
+   if (e != 1)
+     abort ();
+   return 0;
+ }
+