re PR tree-optimization/69776 (Wrong optimization with aliasing)

2016-02-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/69776
	* tree-ssa-sccvn.h (vn_reference_lookup): Adjust prototype.
	* tree-ssa-sccvn.c (vn_reference_lookup): Add parameter to
	indicate whether we can use TBAA to disambiguate against stores.
	Use alias-set zero if not.
	(visit_reference_op_store): Do not use TBAA when looking up
	redundant stores.
	* tree-ssa-pre.c (compute_avail): Use TBAA here.
	(eliminate_dom_walker::before_dom_children): But not when looking
	up redundant stores.

	* gcc.dg/torture/pr69776.c: New testcase.

From-SVN: r233418

gcc/ChangeLog

@@ -1,3 +1,16 @@
+2016-02-15  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/69776
+	* tree-ssa-sccvn.h (vn_reference_lookup): Adjust prototype.
+	* tree-ssa-sccvn.c (vn_reference_lookup): Add parameter to
+	indicate whether we can use TBAA to disambiguate against stores.
+	Use alias-set zero if not.
+	(visit_reference_op_store): Do not use TBAA when looking up
+	redundant stores.
+	* tree-ssa-pre.c (compute_avail): Use TBAA here.
+	(eliminate_dom_walker::before_dom_children): But not when looking
+	up redundant stores.
+
 2016-02-14  John David Anglin  <danglin@gcc.gnu.org>
 
 	* config/pa/pa.md (absqi2, absghi2, bswaphi2, bswapsi2, bswapdi2): New.

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-02-15  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/69776
+	* gcc.dg/torture/pr69776.c: New testcase.
+
 2016-02-14  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/60526

gcc/testsuite/gcc.dg/torture/pr69776.c

@@ -0,0 +1,28 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fstrict-aliasing" } */
+
+extern void *malloc (__SIZE_TYPE__);
+extern void abort (void);
+
+void __attribute__((noinline,noclone))
+foo (int *pi)
+{
+  if (*pi != 1)
+    abort ();
+}
+
+int
+main()
+{
+  void *p = malloc(sizeof (double));
+  int *pi = p;
+  double *pd = p;
+
+  *pi = 1;
+  int a = *pi;
+  *pd = 0;
+  *pi = a;
+  foo (pi);
+
+  return 0;
+}

gcc/tree-ssa-pre.c

@@ -3745,7 +3745,7 @@ compute_avail (void)
 		      vn_reference_t ref;
 		      vn_reference_lookup (gimple_assign_rhs1 (stmt),
 					   gimple_vuse (stmt),
-					   VN_WALK, &ref);
+					   VN_WALK, &ref, true);
 		      if (!ref)
 			continue;
 
@@ -4208,7 +4208,7 @@ eliminate_dom_walker::before_dom_children (basic_block b)
           tree val;
 	  tree rhs = gimple_assign_rhs1 (stmt);
           val = vn_reference_lookup (gimple_assign_lhs (stmt),
-                                     gimple_vuse (stmt), VN_WALK, NULL);
+                                     gimple_vuse (stmt), VN_WALK, NULL, false);
           if (TREE_CODE (rhs) == SSA_NAME)
             rhs = VN_INFO (rhs)->valnum;
           if (val

gcc/tree-ssa-sccvn.c

@@ -2230,11 +2230,12 @@ vn_reference_lookup_pieces (tree vuse, alias_set_type set, tree type,
    number if it exists in the hash table.  Return NULL_TREE if it does
    not exist in the hash table or if the result field of the structure
    was NULL..  VNRESULT will be filled in with the vn_reference_t
-   stored in the hashtable if one exists.  */
+   stored in the hashtable if one exists.  When TBAA_P is false assume
+   we are looking up a store and treat it as having alias-set zero.  */
 
 tree
 vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
-		     vn_reference_t *vnresult)
+		     vn_reference_t *vnresult, bool tbaa_p)
 {
   vec<vn_reference_op_s> operands;
   struct vn_reference_s vr1;
@@ -2264,6 +2265,8 @@ vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
 	  || !ao_ref_init_from_vn_reference (&r, vr1.set, vr1.type,
 					     vr1.operands))
 	ao_ref_init (&r, op);
+      if (! tbaa_p)
+	r.ref_alias_set = r.base_alias_set = 0;
       vn_walk_kind = kind;
       wvnresult =
 	(vn_reference_t)walk_non_aliased_vuses (&r, vr1.vuse,
@@ -3350,7 +3353,7 @@ visit_reference_op_load (tree lhs, tree op, gimple *stmt)
   last_vuse = gimple_vuse (stmt);
   last_vuse_ptr = &last_vuse;
   result = vn_reference_lookup (op, gimple_vuse (stmt),
-				default_vn_walk_kind, NULL);
+				default_vn_walk_kind, NULL, true);
   last_vuse_ptr = NULL;
 
   /* We handle type-punning through unions by value-numbering based
@@ -3472,7 +3475,7 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt)
      Otherwise, the vdefs for the store are used when inserting into
      the table, since the store generates a new memory state.  */
 
-  result = vn_reference_lookup (lhs, vuse, VN_NOWALK, NULL);
+  result = vn_reference_lookup (lhs, vuse, VN_NOWALK, NULL, false);
 
   if (result)
     {
@@ -3487,7 +3490,7 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt)
       && default_vn_walk_kind == VN_WALK)
     {
       assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op);
-      vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult);
+      vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult, false);
       if (vnresult)
 	{
 	  VN_INFO (vdef)->use_processed = true;

gcc/tree-ssa-sccvn.h

@@ -216,7 +216,7 @@ bool ao_ref_init_from_vn_reference (ao_ref *, alias_set_type, tree,
 tree vn_reference_lookup_pieces (tree, alias_set_type, tree,
 				 vec<vn_reference_op_s> ,
 				 vn_reference_t *, vn_lookup_kind);
-tree vn_reference_lookup (tree, tree, vn_lookup_kind, vn_reference_t *);
+tree vn_reference_lookup (tree, tree, vn_lookup_kind, vn_reference_t *, bool);
 void vn_reference_lookup_call (gcall *, vn_reference_t *, vn_reference_t);
 vn_reference_t vn_reference_insert_pieces (tree, alias_set_type, tree,
 					   vec<vn_reference_op_s> ,