2012-04-13 Tom de Vries <tom@codesourcery.com>

	Backport from mainline r186418.

	2012-04-13  Tom de Vries  <tom@codesourcery.com>

	* tree-ssa-tail-merge.c (gsi_advance_bw_nondebug_nonlocal): Add
	parameters vuse and vuse_escaped.
	(find_duplicate): Init vuse1, vuse2 and vuse_escaped.  Pass to
	gsi_advance_bw_nondebug_nonlocal.  Return if vuse_escaped and
	vuse1 != vuse2.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@186424 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b33f326..3bb08d7 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,15 @@
+2012-04-13  Tom de Vries  <tom@codesourcery.com>
+
+       Backport from mainline r186418.
+
+       2012-04-13  Tom de Vries  <tom@codesourcery.com>
+
+       * tree-ssa-tail-merge.c (gsi_advance_bw_nondebug_nonlocal): Add
+       parameters vuse and vuse_escaped.
+       (find_duplicate): Init vuse1, vuse2 and vuse_escaped.  Pass to
+       gsi_advance_bw_nondebug_nonlocal.  Return if vuse_escaped and
+       vuse1 != vuse2.
+
 2012-04-13  Richard Guenther  <rguenther@suse.de>
 
        PR tree-optimization/52969

diff --git a/gcc/tree-ssa-tail-merge.c b/gcc/tree-ssa-tail-merge.c
index 1f46b10..25ec43e 100644 (file)
--- a/gcc/tree-ssa-tail-merge.c
+++ b/gcc/tree-ssa-tail-merge.c
@@ -1123,18 +1123,31 @@ gimple_equal_p (same_succ same_succ, gimple s1, gimple s2)
     }
 }
 
-/* Let GSI skip backwards over local defs.  */
+/* Let GSI skip backwards over local defs.  Return the earliest vuse in VUSE.
+   Return true in VUSE_ESCAPED if the vuse influenced a SSA_OP_DEF of one of the
+   processed statements.  */
 
 static void
-gsi_advance_bw_nondebug_nonlocal (gimple_stmt_iterator *gsi)
+gsi_advance_bw_nondebug_nonlocal (gimple_stmt_iterator *gsi, tree *vuse,
+                                 bool *vuse_escaped)
 {
   gimple stmt;
+  tree lvuse;
 
   while (true)
     {
       if (gsi_end_p (*gsi))
        return;
       stmt = gsi_stmt (*gsi);
+
+      lvuse = gimple_vuse (stmt);
+      if (lvuse != NULL_TREE)
+       {
+         *vuse = lvuse;
+         if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_DEF))
+           *vuse_escaped = true;
+       }
+
       if (!(is_gimple_assign (stmt) && local_def (gimple_get_lhs (stmt))
            && !gimple_has_side_effects (stmt)))
        return;
@@ -1150,9 +1163,11 @@ find_duplicate (same_succ same_succ, basic_block bb1, basic_block bb2)
 {
   gimple_stmt_iterator gsi1 = gsi_last_nondebug_bb (bb1);
   gimple_stmt_iterator gsi2 = gsi_last_nondebug_bb (bb2);
+  tree vuse1 = NULL_TREE, vuse2 = NULL_TREE;
+  bool vuse_escaped = false;
 
-  gsi_advance_bw_nondebug_nonlocal (&gsi1);
-  gsi_advance_bw_nondebug_nonlocal (&gsi2);
+  gsi_advance_bw_nondebug_nonlocal (&gsi1, &vuse1, &vuse_escaped);
+  gsi_advance_bw_nondebug_nonlocal (&gsi2, &vuse2, &vuse_escaped);
 
   while (!gsi_end_p (gsi1) && !gsi_end_p (gsi2))
     {
@@ -1161,13 +1176,20 @@ find_duplicate (same_succ same_succ, basic_block bb1, basic_block bb2)
 
       gsi_prev_nondebug (&gsi1);
       gsi_prev_nondebug (&gsi2);
-      gsi_advance_bw_nondebug_nonlocal (&gsi1);
-      gsi_advance_bw_nondebug_nonlocal (&gsi2);
+      gsi_advance_bw_nondebug_nonlocal (&gsi1, &vuse1, &vuse_escaped);
+      gsi_advance_bw_nondebug_nonlocal (&gsi2, &vuse2, &vuse_escaped);
     }
 
   if (!(gsi_end_p (gsi1) && gsi_end_p (gsi2)))
     return;
 
+  /* If the incoming vuses are not the same, and the vuse escaped into an
+     SSA_OP_DEF, then merging the 2 blocks will change the value of the def,
+     which potentially means the semantics of one of the blocks will be changed.
+     TODO: make this check more precise.  */
+  if (vuse_escaped && vuse1 != vuse2)
+    return;
+
   if (dump_file)
     fprintf (dump_file, "find_duplicates: <bb %d> duplicate of <bb %d>\n",
             bb1->index, bb2->index);