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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>
hifive-unleashed-5.1
Uros Bizjak 2008-10-24 16:53:33 +02:00 committed by H. Peter Anvin
parent a376f30a95
commit 838e8bb71d
1 changed files with 9 additions and 1 deletions
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10
arch/x86/include/asm/bitops.h
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@ -168,7 +168,15 @@ static inline void __change_bit(int nr, volatile unsigned long *addr)
*/
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));
}
}
/**