[PATCH] Fix PR62031

[Richard Biener <rguenther at suse dot de>]

This fixes wrong answer from data-dependence analysis by realizing
that _all_ (even non-evolving) indirect accesses cannot be constrained
to a full object size.  This also gets rid of that ugly
DR_UNCONSTRAINED_BASE hack (but effectively make it always active).

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2014-08-14  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/pr62031.c: New testcase.

Index: gcc/tree-data-ref.c
===================================================================
--- gcc/tree-data-ref.c	(revision 213958)
+++ gcc/tree-data-ref.c	(working copy)
@@ -982,7 +982,6 @@ dr_analyze_indices (struct data_referenc
 	  ref = fold_build2_loc (EXPR_LOCATION (ref),
 				 MEM_REF, TREE_TYPE (ref),
 				 base, memoff);
-	  DR_UNCONSTRAINED_BASE (dr) = true;
 	  access_fns.safe_push (access_fn);
 	}
     }
@@ -1389,14 +1388,20 @@ dr_may_alias_p (const struct data_refere
 	return false;
     }
 
-  /* If we had an evolution in a MEM_REF BASE_OBJECT we do not know
-     the size of the base-object.  So we cannot do any offset/overlap
-     based analysis but have to rely on points-to information only.  */
+  /* If we had an evolution in a pointer-based MEM_REF BASE_OBJECT we
+     do not know the size of the base-object.  So we cannot do any
+     offset/overlap based analysis but have to rely on points-to
+     information only.  */
   if (TREE_CODE (addr_a) == MEM_REF
-      && DR_UNCONSTRAINED_BASE (a))
+      && TREE_CODE (TREE_OPERAND (addr_a, 0)) == SSA_NAME)
     {
-      if (TREE_CODE (addr_b) == MEM_REF
-	  && DR_UNCONSTRAINED_BASE (b))
+      /* For true dependences we can apply TBAA.  */
+      if (flag_strict_aliasing
+	  && DR_IS_WRITE (a) && DR_IS_READ (b)
+	  && !alias_sets_conflict_p (get_alias_set (DR_REF (a)),
+				     get_alias_set (DR_REF (b))))
+	return false;
+      if (TREE_CODE (addr_b) == MEM_REF)
 	return ptr_derefs_may_alias_p (TREE_OPERAND (addr_a, 0),
 				       TREE_OPERAND (addr_b, 0));
       else
@@ -1404,9 +1409,21 @@ dr_may_alias_p (const struct data_refere
 				       build_fold_addr_expr (addr_b));
     }
   else if (TREE_CODE (addr_b) == MEM_REF
-	   && DR_UNCONSTRAINED_BASE (b))
-    return ptr_derefs_may_alias_p (build_fold_addr_expr (addr_a),
-				   TREE_OPERAND (addr_b, 0));
+	   && TREE_CODE (TREE_OPERAND (addr_b, 0)) == SSA_NAME)
+    {
+      /* For true dependences we can apply TBAA.  */
+      if (flag_strict_aliasing
+	  && DR_IS_WRITE (a) && DR_IS_READ (b)
+	  && !alias_sets_conflict_p (get_alias_set (DR_REF (a)),
+				     get_alias_set (DR_REF (b))))
+	return false;
+      if (TREE_CODE (addr_a) == MEM_REF)
+	return ptr_derefs_may_alias_p (TREE_OPERAND (addr_a, 0),
+				       TREE_OPERAND (addr_b, 0));
+      else
+	return ptr_derefs_may_alias_p (build_fold_addr_expr (addr_a),
+				       TREE_OPERAND (addr_b, 0));
+    }
 
   /* Otherwise DR_BASE_OBJECT is an access that covers the whole object
      that is being subsetted in the loop nest.  */

Index: gcc/tree-data-ref.h
===================================================================
--- gcc/tree-data-ref.h	(revision 213958)
+++ gcc/tree-data-ref.h	(working copy)
@@ -81,10 +81,6 @@ 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
@@ -195,7 +191,6 @@ 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/pr62031.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr62031.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr62031.c	(working copy)
@@ -0,0 +1,52 @@
+/* { dg-do run } */
+
+#include <stdlib.h>
+
+#define NUM_OF_STATES 4
+typedef unsigned int entry_t[2];
+typedef struct entries_item { entry_t metricEntries_[0]; } entries_item_t;
+
+void __attribute__((noinline,noclone))
+test_00(size_t numOfStates, entries_item_t* p_bm,
+	const unsigned int* polyArray,
+	size_t polyArraySize)
+{
+  size_t idx;
+  unsigned int hlp0, hlp1;
+  for (idx = 0; idx < numOfStates; ++idx)
+    {
+      size_t idy;
+
+      hlp0 = (idx << 1) | 0x00;
+      hlp1 = (idx << 1) | 0x01;
+      p_bm->metricEntries_[idx][0] = 0;
+      p_bm->metricEntries_[idx][1] = 0;
+      for (idy = 0; idy < polyArraySize; ++idy)
+	{
+	  p_bm->metricEntries_[idx][0]
+	      |= __builtin_parity(hlp0 & polyArray[idy]) << idy;
+	  p_bm->metricEntries_[idx][1]
+	      |= __builtin_parity(hlp1 & polyArray[idy]) << idy;
+	}
+    }
+}
+
+int main()
+{
+  unsigned int polyArray[] = { 0x07, 0x05 };
+  entries_item_t* pBranchMetrics;
+  pBranchMetrics = malloc(sizeof(entry_t) * NUM_OF_STATES);
+  test_00(NUM_OF_STATES, pBranchMetrics, polyArray,
+	  sizeof(polyArray) / sizeof(polyArray[0]));
+  if (pBranchMetrics->metricEntries_[0][0] != 0
+      || pBranchMetrics->metricEntries_[0][1] != 3
+      || pBranchMetrics->metricEntries_[1][0] != 1
+      || pBranchMetrics->metricEntries_[1][1] != 2
+      || pBranchMetrics->metricEntries_[2][0] != 3
+      || pBranchMetrics->metricEntries_[2][1] != 0
+      || pBranchMetrics->metricEntries_[3][0] != 2
+      || pBranchMetrics->metricEntries_[3][1] != 1)
+    abort ();
+  free(pBranchMetrics);
+  return 0;
+}