re PR tree-optimization/65917 (XFAIL: gcc.dg/tree-ssa/20030922-2.c scan-tree-dump-times dom1 "if " 2)

	PR tree-optimization/65917
	* tree-ssa-dom.c (record_temporary_equivalences): Record both
	equivalences from if (x == y) style conditionals.
	(loop_depth_of_name): Remove.
	(record_equality): Remove loop depth check.
	* tree-ssa-scopedtables.h (const_and_copies): Refine comments.
	(const_and_copies::record_const_or_copy_raw): New member function.
	* tree-ssa-scopedtables.c
	(const_and_copies::record_const_or_copy_raw): New, factored out of
	(const_and_copies::record_const_or_copy): Call new member function.

        PR tree-optimization/65917
	* gcc.dg/tree-ssa/20030922-2.c: No longer xfailed.

From-SVN: r233207

1 files changed, 10 insertions, 31 deletions

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index b690d92..f44ac13 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -917,6 +917,15 @@ record_temporary_equivalences (edge e,
       tree rhs = edge_info->rhs;
       record_equality (lhs, rhs, const_and_copies);
 
+      /* We already recorded that LHS = RHS, with canonicalization,
+	 value chain following, etc.
+
+	 We also want to return RHS = LHS, but without any canonicalization
+	 or value chain following.  */
+      if (TREE_CODE (rhs) == SSA_NAME)
+	const_and_copies->record_const_or_copy_raw (rhs, lhs,
+						    SSA_NAME_VALUE (rhs));
+
       /* If LHS is an SSA_NAME and RHS is a constant integer and LHS was
 	 set via a widening type conversion, then we may be able to record
 	 additional equivalences.  */
@@ -1161,33 +1170,6 @@ record_cond (cond_equivalence *p,
     delete element;
 }
 
-/* Return the loop depth of the basic block of the defining statement of X.
-   This number should not be treated as absolutely correct because the loop
-   information may not be completely up-to-date when dom runs.  However, it
-   will be relatively correct, and as more passes are taught to keep loop info
-   up to date, the result will become more and more accurate.  */
-
-static int
-loop_depth_of_name (tree x)
-{
-  gimple *defstmt;
-  basic_block defbb;
-
-  /* If it's not an SSA_NAME, we have no clue where the definition is.  */
-  if (TREE_CODE (x) != SSA_NAME)
-    return 0;
-
-  /* Otherwise return the loop depth of the defining statement's bb.
-     Note that there may not actually be a bb for this statement, if the
-     ssa_name is live on entry.  */
-  defstmt = SSA_NAME_DEF_STMT (x);
-  defbb = gimple_bb (defstmt);
-  if (!defbb)
-    return 0;
-
-  return bb_loop_depth (defbb);
-}
-
 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
    This constrains the cases in which we may treat this as assignment.  */
 
@@ -1224,10 +1206,7 @@ record_equality (tree x, tree y, class const_and_copies *const_and_copies)
      long as we canonicalize on one value.  */
   if (is_gimple_min_invariant (y))
     ;
-  else if (is_gimple_min_invariant (x)
-	   /* ???  When threading over backedges the following is important
-	      for correctness.  See PR61757.  */
-	   || (loop_depth_of_name (x) < loop_depth_of_name (y)))
+  else if (is_gimple_min_invariant (x))
     prev_x = x, x = y, y = prev_x, prev_x = prev_y;
   else if (prev_x && is_gimple_min_invariant (prev_x))
     x = y, y = prev_x, prev_x = prev_y;