x86: Implement change_bit with immediate operand as "lock xorb"
Impact: Minor optimization.
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.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 3600103..9fa9dcd 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -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));
+ }
}
/**