re PR tree-optimization/20913 (copy-prop does not fold conditionals)

gcc/
	PR tree-optimization/20913
	* tree-ssa-copy.c (copy_prop_visit_cond_stmt): Fold COND_EXPR.

testsuite/
	PR tree-optimization/20913
	* gcc.dg/tree-ssa/pr20913.c: New.

From-SVN: r98090

gcc/ChangeLog

+2005-04-13  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/20913
+	* tree-ssa-copy.c (copy_prop_visit_cond_stmt): Fold COND_EXPR.
+
 2005-04-13  Julian Brown  <julian@codesourcery.com>
 
 	* config/elfos.h (MAKE_DECL_ONE_ONLY): Redefined to stop DECL_WEAK from

gcc/testsuite/ChangeLog

+2005-04-13  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/20913
+	* gcc.dg/tree-ssa/pr20913.c: New.
+
 2005-04-13  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
 
 	PR c++/13744

gcc/testsuite/gcc.dg/tree-ssa/pr20913.c

+/* PR tree-optimization/20913
+   COPY-PROP did not fold COND_EXPR, blocking some copy propagation
+   opportunities.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-copyprop1-details" } */
+
+int
+foo (int a, int b, int c, int d)
+{
+  int x, y;
+
+  b = a;
+  if (a == b)
+    x = c;
+  else
+    x = d;
+
+  if (x == c)
+    return a;
+  else
+    return b;
+}
+
+/* { dg-final { scan-tree-dump-times "with if \\(1\\)" 2 "copyprop1"} } */

gcc/tree-ssa-copy.c

@@ -626,9 +626,16 @@ copy_prop_visit_cond_stmt (tree stmt, edge *taken_edge_p)
 	  print_generic_stmt (dump_file, cond, 0);
 	}
 
-      *taken_edge_p = find_taken_edge (bb_for_stmt (stmt), cond);
-      if (*taken_edge_p)
-	retval = SSA_PROP_INTERESTING;
+      /* We can fold COND only and get a useful result only when we
+	 have the same SSA_NAME on both sides of a comparison
+	 operator.  */
+      if (TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
+	  && TREE_OPERAND (cond, 0) == TREE_OPERAND (cond, 1))
+	{
+	  *taken_edge_p = find_taken_edge (bb_for_stmt (stmt), fold (cond));
+	  if (*taken_edge_p)
+	    retval = SSA_PROP_INTERESTING;
+	}
 
       /* Restore the original operands.  */
       for (i = 0; i < NUM_USES (uses); i++)