re PR tree-optimization/63916 (value-numbering fails to forward variable addresses)

2015-06-03  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63916
	* tree-ssa-sccvn.c (vn_reference_maybe_forwprop_address):
	Forward-propagate non-invariant addresses by splicing their
	reference ops if the result isn't going to be used by PRE.
	(vn_reference_lookup_3): Remove pointless assert.

	* gcc.dg/tree-ssa/ssa-fre-45.c: New testcase.

From-SVN: r224061

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 06dda145fd6243383ca5ff718c36e197f84ad63d..8813ade38d50570eec5ee4d1a5359655ecd5d046 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2015-06-03  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/63916
+       * tree-ssa-sccvn.c (vn_reference_maybe_forwprop_address):
+       Forward-propagate non-invariant addresses by splicing their
+       reference ops if the result isn't going to be used by PRE.
+       (vn_reference_lookup_3): Remove pointless assert.
+
 2015-06-03  Richard Biener  <rguenther@suse.de>
 
        PR tree-optimization/66375

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9fd5941e979772378c35129fc384c532ee7e51cd..026dd538696ce3c846673fca43a2260d53bc34ff 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-06-03  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/63916
+       * gcc.dg/tree-ssa/ssa-fre-45.c: New testcase.
+
 2015-06-03  Richard Biener  <rguenther@suse.de>
 
        PR tree-optimization/66375

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-45.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-45.c
new file mode 100644 (file)
index 0000000..ea8957f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-45.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-fre1" } */
+
+struct S { float a, b; };
+
+float
+foo (int x, float y)
+{
+  struct S z[1024];
+  z[x].a = y;
+  struct S *p = &z[x];
+  float *q = (float *) p;
+  return *q;
+}
+
+/* { dg-final { scan-tree-dump "return y_\\d\+\\(D\\);" "fre1" } } */

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 19fb604b5116dffde5678a51b31277eec2b90f8e..e7838ed4132a9eeb58ce0411cbb2501b877c4160 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -144,6 +144,10 @@ along with GCC; see the file COPYING3.  If not see
 */
 
 
+static tree *last_vuse_ptr;
+static vn_lookup_kind vn_walk_kind;
+static vn_lookup_kind default_vn_walk_kind;
+
 /* vn_nary_op hashtable helpers.  */
 
 struct vn_nary_op_hasher : typed_noop_remove <vn_nary_op_s>
@@ -1259,6 +1263,25 @@ vn_reference_maybe_forwprop_address (vec<vn_reference_op_s> *ops,
       addr = gimple_assign_rhs1 (def_stmt);
       addr_base = get_addr_base_and_unit_offset (TREE_OPERAND (addr, 0),
                                                 &addr_offset);
+      /* If that didn't work because the address isn't invariant propagate
+         the reference tree from the address operation in case the current
+        dereference isn't offsetted.  */
+      if (!addr_base
+         && *i_p == ops->length () - 1
+         && off == 0
+         /* This makes us disable this transform for PRE where the
+            reference ops might be also used for code insertion which
+            is invalid.  */
+         && default_vn_walk_kind == VN_WALKREWRITE)
+       {
+         auto_vec<vn_reference_op_s, 32> tem;
+         copy_reference_ops_from_ref (TREE_OPERAND (addr, 0), &tem);
+         ops->pop ();
+         ops->pop ();
+         ops->safe_splice (tem);
+         --*i_p;
+         return;
+       }
       if (!addr_base
          || TREE_CODE (addr_base) != MEM_REF)
        return;
@@ -1557,10 +1580,6 @@ vn_reference_lookup_1 (vn_reference_t vr, vn_reference_t *vnresult)
   return NULL_TREE;
 }
 
-static tree *last_vuse_ptr;
-static vn_lookup_kind vn_walk_kind;
-static vn_lookup_kind default_vn_walk_kind;
-
 /* Callback for walk_non_aliased_vuses.  Adjusts the vn_reference_t VR_
    with the current VUSE and performs the expression lookup.  */
 
@@ -1649,15 +1668,12 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
   /* First try to disambiguate after value-replacing in the definitions LHS.  */
   if (is_gimple_assign (def_stmt))
     {
-      vec<vn_reference_op_s> tem;
       tree lhs = gimple_assign_lhs (def_stmt);
       bool valueized_anything = false;
       /* Avoid re-allocation overhead.  */
       lhs_ops.truncate (0);
       copy_reference_ops_from_ref (lhs, &lhs_ops);
-      tem = lhs_ops;
       lhs_ops = valueize_refs_1 (lhs_ops, &valueized_anything);
-      gcc_assert (lhs_ops == tem);
       if (valueized_anything)
        {
          lhs_ref_ok = ao_ref_init_from_vn_reference (&lhs_ref,