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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fda12cf1f36b8ed59c2d0f477e1622df2c30def0..565b50598c497958e2a6ec695b95d2390ead4c7a 100644 (file)
--- a/gcc/ChangeLog
+++ b/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.

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9dfdc7694b202aa0ad72fea2f956cad767cbd8d9..4d129d810f69a4c487f65b7bf9b6717719af28d9 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/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

diff --git a/gcc/testsuite/gcc.dg/torture/pr69776.c b/gcc/testsuite/gcc.dg/torture/pr69776.c
new file mode 100644 (file)
index 0000000..f2d971c
--- /dev/null
+++ b/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;
+}

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 3570ee92a2baff95a214076e705a03bacf0a55d9..b2d63acf93039ee8c7ac086814f080c985a4bfa6 100644 (file)
--- a/gcc/tree-ssa-pre.c
+++ b/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

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 726294e2c2c808b799167ee81cdab2a7c77c71ef..5b78ba4a7505c65fc056eadaec3aeeaf9b58df63 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/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;

diff --git a/gcc/tree-ssa-sccvn.h b/gcc/tree-ssa-sccvn.h
index e8e710b0c55612e9057437733328ff6104ee114d..a3f9fa26ad3c450c9cd7c064002711695e43e778 100644 (file)
--- a/gcc/tree-ssa-sccvn.h
+++ b/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> ,