re PR middle-end/30951 (Does not fold x + CST == x and x + CST != x)

2007-02-24  Richard Guenther  <rguenther@suse.de>

	PR middle-end/30951
	* fold-const.c (fold_binary): Fold x +- CST op x for
	EQ_EXPR and NE_EXPR.

	* gcc.dg/pr30951.c: New testcase.

From-SVN: r122295

gcc/ChangeLog

+2007-02-24  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30951
+	* fold-const.c (fold_binary): Fold x +- CST op x for
+	EQ_EXPR and NE_EXPR.
+
 2007-02-24  John David Anglin  <dave.anglin@nrc-cnrc.gc.ca>
 
 	* pa.md (muldi3): Force subregs to registers in 64-bit expander.

gcc/fold-const.c

@@ -11203,6 +11203,24 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 					 fold_convert (TREE_TYPE (arg0), arg1),
 					 TREE_OPERAND (arg0, 1)));
 
+      /* Transform comparisons of the form X +- C CMP X.  */
+      if ((TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
+	  && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0)
+	  && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
+	  && (INTEGRAL_TYPE_P (TREE_TYPE (arg0))
+	      || POINTER_TYPE_P (TREE_TYPE (arg0))))
+	{
+	  tree cst = TREE_OPERAND (arg0, 1);
+
+	  if (code == EQ_EXPR
+	      && !integer_zerop (cst))
+	    return omit_two_operands (type, boolean_false_node,
+				      TREE_OPERAND (arg0, 0), arg1);
+	  else
+	    return omit_two_operands (type, boolean_true_node,
+				      TREE_OPERAND (arg0, 0), arg1);
+	}
+
       /* If we have X - Y == 0, we can convert that to X == Y and similarly
 	 for !=.  Don't do this for ordered comparisons due to overflow.  */
       if (TREE_CODE (arg0) == MINUS_EXPR

gcc/testsuite/ChangeLog

+2007-02-24  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30951
+	* gcc.dg/pr30951.c: New testcase.
+
 2007-02-24  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* gcc.dg/torture/builtin-modf-1.c: New test.

gcc/testsuite/gcc.dg/pr30951.c

+/* { dg-do link } */
+
+extern void link_error (void);
+
+void test (int x, unsigned int y)
+{
+  if (x + 5 == x)
+    link_error ();
+  if (x == x + 10)
+    link_error ();
+  if (y + 5 == y)
+    link_error ();
+  if (y == y + 10)
+    link_error ();
+  if (x + 5 != x)
+    ;
+  else
+    link_error ();
+  if (x != x + 10)
+    ;
+  else
+    link_error ();
+  if (y + 5 != y)
+    ;
+  else
+    link_error ();
+  if (y != y + 10)
+    ;
+  else
+    link_error ();
+}
+
+int main()
+{
+  return 0;
+}