From 015c318662801cd61e48698362d3d11151fbfdfa Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@cs.umass.edu>
Date: Thu, 20 Mar 2003 16:10:36 +0000
Subject: [PATCH] * fold-const.c (fold): Fold A - (A & B) into ~B & A.

From-SVN: r64615
---
 gcc/ChangeLog    |  4 ++++
 gcc/fold-const.c | 16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0f58a3f87f4..d20b1758a89 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2003-03-20  Kazu Hirata  <kazu at cs dot umass dot edu>
+
+	* fold-const.c (fold): Fold A - (A & B) into ~B & A.
+
 2003-03-20  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* config/h8300/h8300.md (a peephole2): New.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 48c3683f8c2..4890c173e81 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5560,6 +5560,22 @@ fold (expr)
 					     TREE_OPERAND (arg0, 0),
 					     TREE_OPERAND (arg1, 0))),
 				TREE_OPERAND (arg0, 1)));
+
+	  /* Fold A - (A & B) into ~B & A.  */
+	  if (!TREE_SIDE_EFFECTS (arg0)
+	      && TREE_CODE (arg1) == BIT_AND_EXPR)
+	    {
+	      if (operand_equal_p (arg0, TREE_OPERAND (arg1, 1), 0))
+		return fold (build (BIT_AND_EXPR, type,
+				    fold (build1 (BIT_NOT_EXPR, type,
+						  TREE_OPERAND (arg1, 0))),
+				    arg0));
+	      if (operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
+		return fold (build (BIT_AND_EXPR, type,
+				    fold (build1 (BIT_NOT_EXPR, type,
+						  TREE_OPERAND (arg1, 1))),
+				    arg0));
+	    }
 	}
 
       /* See if ARG1 is zero and X - ARG1 reduces to X.  */