2005-10-05 Steven Bosscher <stevenb@suse.de>

gcc/
	PR tree-optimization/23049
	* tree-ssa-dom.c (thread_across_edge): Make sure that the condition
	of a COND_EXPR is folded before calling fold on the whole rhs of a
	conditional assignment.
	* doc/tree-ssa.texi: Update the GIMPLE grammar for a valid rhs to
	document that a COND_EXPR may appear there.

testsuite/
	* gcc.dg/pr23049.c: New test.

	* gcc.dg/ucnid-4.c: Fix test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@104938 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 26 insertions, 7 deletions

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 1b78b6d5f39..71dcd4ffc6d 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -666,7 +666,7 @@ thread_across_edge (struct dom_walk_data *walk_data, edge e)
      statements.  This does not prevent threading through E->dest.  */
   for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
     {
-      tree cached_lhs;
+      tree cached_lhs = NULL;
 
       stmt = bsi_stmt (bsi);
 
@@ -705,7 +705,7 @@ thread_across_edge (struct dom_walk_data *walk_data, edge e)
       else
 	{
 	  /* Copy the operands.  */
-	  tree *copy;
+	  tree *copy, pre_fold_expr;
 	  ssa_op_iter iter;
 	  use_operand_p use_p;
 	  unsigned int num, i = 0;
@@ -729,12 +729,31 @@ thread_across_edge (struct dom_walk_data *walk_data, edge e)
 
 	  /* Try to fold/lookup the new expression.  Inserting the
 	     expression into the hash table is unlikely to help
-	     simplify anything later, so just query the hashtable.  */
-	  cached_lhs = fold (TREE_OPERAND (stmt, 1));
-	  if (TREE_CODE (cached_lhs) != SSA_NAME
-	      && !is_gimple_min_invariant (cached_lhs))
-	    cached_lhs = lookup_avail_expr (stmt, false);
+	     Sadly, we have to handle conditional assignments specially
+	     here, because fold expects all the operands of an expression
+	     to be folded before the expression itself is folded, but we
+	     can't just substitute the folded condition here.  */
+	  if (TREE_CODE (TREE_OPERAND (stmt, 1)) == COND_EXPR)
+	    {
+	      tree cond = COND_EXPR_COND (TREE_OPERAND (stmt, 1));
+	      cond = fold (cond);
+	      if (cond == boolean_true_node)
+		pre_fold_expr = COND_EXPR_THEN (TREE_OPERAND (stmt, 1));
+	      else if (cond == boolean_false_node)
+		pre_fold_expr = COND_EXPR_ELSE (TREE_OPERAND (stmt, 1));
+	      else
+		pre_fold_expr = TREE_OPERAND (stmt, 1);
+	    }
+	  else
+	    pre_fold_expr = TREE_OPERAND (stmt, 1);
 
+	  if (pre_fold_expr)
+	    {
+	      cached_lhs = fold (pre_fold_expr);
+	      if (TREE_CODE (cached_lhs) != SSA_NAME
+		  && !is_gimple_min_invariant (cached_lhs))
+	        cached_lhs = lookup_avail_expr (stmt, false);
+	    }
 
 	  /* Restore the statement's original uses/defs.  */
 	  i = 0;