re PR tree-optimization/14847 ([tree-ssa] combine "if (a & 1) goto there" and…

re PR tree-optimization/14847 ([tree-ssa] combine "if (a & 1) goto there" and "if (a & 4) goto there")

2008-04-30  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/14847
	* tree-ssa-ifcombine.c (get_name_for_bit_test): New helper function.
	(recognize_bits_test): Use it.
	(recognize_single_bit_test): Likewise.

	* gcc.dg/tree-ssa/ssa-ifcombine-6.c: New testcase.

From-SVN: r134825

gcc/ChangeLog

+2008-04-30  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/14847
+	* tree-ssa-ifcombine.c (get_name_for_bit_test): New helper function.
+	(recognize_bits_test): Use it.
+	(recognize_single_bit_test): Likewise.
+
 2008-04-30  Martin Jambor  <mjambor@suse.cz>
 
 	* ipa-cp.c (ipcp_init_stage): Calls ipa_set_called_with_variable_arg

gcc/testsuite/ChangeLog

+2008-04-30  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/14847
+	* gcc.dg/tree-ssa/ssa-ifcombine-6.c: New testcase.
+
 2008-04-30  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/35986

gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-6.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-ifcombine" } */
+
+void bar (void);
+
+void
+foo1 (unsigned int a)
+{
+  if (a & 1)
+    goto heaven;
+  if (a & 4)
+    goto heaven;
+  return;
+
+ heaven:
+  bar ();
+}
+
+void
+foo2 (unsigned int a)
+{
+  if (a & 1)
+    if (a & 4)
+      goto heaven;
+  return;
+
+ heaven:
+  bar ();
+}
+
+
+/* The special treatment of a & 1 != 0 in fold caused the pattern not
+   to be recognized due to extra conversions inserted.  */
+
+/* { dg-final { scan-tree-dump "optimizing bits or bits test" "ifcombine" } } */
+/* { dg-final { scan-tree-dump "optimizing double bit test" "ifcombine" } } */
+/* { dg-final { cleanup-tree-dump "ifcombine" } } */

gcc/tree-ssa-ifcombine.c

@@ -135,6 +135,32 @@ same_phi_args_p (basic_block bb1, basic_block bb2, basic_block dest)
   return true;
 }
 
+/* Return the best representative SSA name for CANDIDATE which is used
+   in a bit test.  */
+
+static tree
+get_name_for_bit_test (tree candidate)
+{
+  /* Skip single-use names in favor of using the name from a
+     non-widening conversion definition.  */
+  if (TREE_CODE (candidate) == SSA_NAME
+      && has_single_use (candidate))
+    {
+      tree def_stmt = SSA_NAME_DEF_STMT (candidate);
+      if (TREE_CODE (def_stmt) == GIMPLE_MODIFY_STMT
+	  && (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) == NOP_EXPR
+	      || TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) == CONVERT_EXPR))
+	{
+	  tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	  if (TYPE_PRECISION (TREE_TYPE (rhs))
+	      <= TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (rhs, 0))))
+	    return TREE_OPERAND (rhs, 0);
+	}
+    }
+
+  return candidate;
+}
+
 /* Recognize a single bit test pattern in COND_EXPR and its defining
    statements.  Store the name being tested in *NAME and the bit
    in *BIT.  The COND_EXPR computes *NAME & (1 << *BIT).
@@ -192,7 +218,7 @@ recognize_single_bit_test (tree cond_expr, tree *name, tree *bit)
 	{
 	  /* t & 1 */
 	  *bit = integer_zero_node;
-	  *name = orig_name;
+	  *name = get_name_for_bit_test (orig_name);
 	}
 
       return true;
@@ -272,7 +298,7 @@ recognize_bits_test (tree cond_expr, tree *name, tree *bits)
   if (TREE_CODE (t) != BIT_AND_EXPR)
     return false;
 
-  *name = TREE_OPERAND (t, 0);
+  *name = get_name_for_bit_test (TREE_OPERAND (t, 0));
   *bits = TREE_OPERAND (t, 1);
 
   return true;