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[PATCH] Fix PR66272


The following fixes PR66272.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk
sofar.

Richard.

2015-05-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/66272
	Revert parts of
	2014-08-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/62031
	* tree-data-ref.c (dr_analyze_indices): Do not set
	DR_UNCONSTRAINED_BASE.
	(dr_may_alias_p): All indirect accesses have to go the
	formerly DR_UNCONSTRAINED_BASE path.
	* tree-data-ref.h (struct indices): Remove
	unconstrained_base member.
	(DR_UNCONSTRAINED_BASE): Remove.

	* gcc.dg/torture/pr66272.c: New testcase.

Index: gcc/tree-data-ref.c
===================================================================
--- gcc/tree-data-ref.c	(revision 223737)
+++ gcc/tree-data-ref.c	(working copy)
@@ -1036,6 +1036,7 @@ dr_analyze_indices (struct data_referenc
 				 base, memoff);
 	  MR_DEPENDENCE_CLIQUE (ref) = MR_DEPENDENCE_CLIQUE (old);
 	  MR_DEPENDENCE_BASE (ref) = MR_DEPENDENCE_BASE (old);
+	  DR_UNCONSTRAINED_BASE (dr) = true;
 	  access_fns.safe_push (access_fn);
 	}
     }
@@ -1453,7 +1454,8 @@ dr_may_alias_p (const struct data_refere
      offset/overlap based analysis but have to rely on points-to
      information only.  */
   if (TREE_CODE (addr_a) == MEM_REF
-      && TREE_CODE (TREE_OPERAND (addr_a, 0)) == SSA_NAME)
+      && (DR_UNCONSTRAINED_BASE (a)
+	  || TREE_CODE (TREE_OPERAND (addr_a, 0)) == SSA_NAME))
     {
       /* For true dependences we can apply TBAA.  */
       if (flag_strict_aliasing
@@ -1469,7 +1471,8 @@ dr_may_alias_p (const struct data_refere
 				       build_fold_addr_expr (addr_b));
     }
   else if (TREE_CODE (addr_b) == MEM_REF
-	   && TREE_CODE (TREE_OPERAND (addr_b, 0)) == SSA_NAME)
+	   && (DR_UNCONSTRAINED_BASE (b)
+	       || TREE_CODE (TREE_OPERAND (addr_b, 0)) == SSA_NAME))
     {
       /* For true dependences we can apply TBAA.  */
       if (flag_strict_aliasing
Index: gcc/tree-data-ref.h
===================================================================
--- gcc/tree-data-ref.h	(revision 223737)
+++ gcc/tree-data-ref.h	(working copy)
@@ -81,6 +81,10 @@ struct indices
 
   /* A list of chrecs.  Access functions of the indices.  */
   vec<tree> access_fns;
+
+  /* Whether BASE_OBJECT is an access representing the whole object
+     or whether the access could not be constrained.  */
+  bool unconstrained_base;
 };
 
 struct dr_alias
@@ -129,6 +133,7 @@ struct data_reference
 #define DR_STMT(DR)                (DR)->stmt
 #define DR_REF(DR)                 (DR)->ref
 #define DR_BASE_OBJECT(DR)         (DR)->indices.base_object
+#define DR_UNCONSTRAINED_BASE(DR)  (DR)->indices.unconstrained_base
 #define DR_ACCESS_FNS(DR)	   (DR)->indices.access_fns
 #define DR_ACCESS_FN(DR, I)        DR_ACCESS_FNS (DR)[I]
 #define DR_NUM_DIMENSIONS(DR)      DR_ACCESS_FNS (DR).length ()
Index: gcc/testsuite/gcc.dg/torture/pr66272.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr66272.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr66272.c	(working copy)
@@ -0,0 +1,23 @@
+/* { dg-do run } */
+
+struct S
+{
+  int f0;
+  int f1;
+};
+
+int b;
+
+int main ()
+{
+  struct S a[2] = { 0 };
+  struct S d = { 0, 1 };
+  for (b = 0; b < 2; b++)
+    {
+      a[b] = d;
+      d = a[0];
+    }
+  if (d.f1 != 1)
+    __builtin_abort ();
+  return 0;
+}


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