[patch] fold-const.c: Fold (A & ~B) - (A & B) into (A ^ B) - B for any B.

[Kazu Hirata]

Hi,

Attached is a patch to fold (A & ~B) - (A & B) into (A ^ B) - B for
any B.  The existing optimization required that B be a power of 2
minus 1, but this requirement is superfluous.

Tested on h8300 port.  OK to apply?

Kazu Hirata

2003-09-30  Kazu Hirata  <kazu@cs.umass.edu>

	* fold-const.c (fold): Fold (A & ~B) - (A & B) into
	(A ^ B) - B for any B.

Index: fold-const.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fold-const.c,v
retrieving revision 1.308
diff -c -r1.308 fold-const.c
*** fold-const.c	29 Sep 2003 17:41:47 -0000	1.308
--- fold-const.c	30 Sep 2003 16:00:38 -0000
***************
*** 6023,6039 ****
  	  if (TREE_CODE (arg0) == BIT_AND_EXPR
  	      && TREE_CODE (arg1) == BIT_AND_EXPR
  	      && operand_equal_p (TREE_OPERAND (arg0, 0),
! 				  TREE_OPERAND (arg1, 0), 0)
! 	      && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
! 	      && TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST)
  	    {
  	      tree mask0 = TREE_OPERAND (arg0, 1);
  	      tree mask1 = TREE_OPERAND (arg1, 1);
  	      tree tem = fold (build1 (BIT_NOT_EXPR, type, mask0));
  	      
! 	      if (operand_equal_p (tem, mask1, 0)
! 		  && integer_pow2p (fold (build (PLUS_EXPR, type,
! 						 mask1, integer_one_node))))
  		{
  		  tem = fold (build (BIT_XOR_EXPR, type,
  				     TREE_OPERAND (arg0, 0), mask1));
--- 6023,6035 ----
  	  if (TREE_CODE (arg0) == BIT_AND_EXPR
  	      && TREE_CODE (arg1) == BIT_AND_EXPR
  	      && operand_equal_p (TREE_OPERAND (arg0, 0),
! 				  TREE_OPERAND (arg1, 0), 0))
  	    {
  	      tree mask0 = TREE_OPERAND (arg0, 1);
  	      tree mask1 = TREE_OPERAND (arg1, 1);
  	      tree tem = fold (build1 (BIT_NOT_EXPR, type, mask0));
  	      
! 	      if (operand_equal_p (tem, mask1, 0))
  		{
  		  tem = fold (build (BIT_XOR_EXPR, type,
  				     TREE_OPERAND (arg0, 0), mask1));