[PATCH, x86]: Implement change_bit with immediate operand as "lock xorb"

[Uros Bizjak]

Hello!

Implement change_bit with immediate bit count as "lock xorb". This is
similar to  "lock orb" and "lock andb"  for set_bit and clear_bit
functions.

Uros.
--- bitops.h~	2008-10-22 23:38:01.000000000 +0200
+++ bitops.h	2008-10-24 12:57:14.000000000 +0200
@@ -168,7 +168,15 @@
  */
 static inline void change_bit(int nr, volatile unsigned long *addr)
 {
-	asm volatile(LOCK_PREFIX "btc %1,%0" : ADDR : "Ir" (nr));
+	if (IS_IMMEDIATE(nr)) {
+		asm volatile(LOCK_PREFIX "xorb %1,%0"
+			: CONST_MASK_ADDR(nr, addr)
+			: "iq" ((u8)CONST_MASK(nr)));
+	} else {
+		asm volatile(LOCK_PREFIX "btc %1,%0"
+			: BITOP_ADDR(addr)
+			: "Ir" (nr));
+	}
 }
 
 /**