x86, bitops: make constant-bit set/clear_bit ops faster, gcc workaround

Jeremy Fitzhardinge reported this compiler bug:

Suggestion from Linus: add "r" to the input constraint of the
set_bit()/clear_bit()'s constant 'nr' branch:

Blows up on "gcc version 3.4.4 20050314 (prerelease) (Debian 3.4.3-13)":

 CC      init/main.o
include2/asm/bitops.h: In function `start_kernel':
include2/asm/bitops.h:59: warning: asm operand 1 probably doesn't match constraints
include2/asm/bitops.h:59: warning: asm operand 1 probably doesn't match constraints
include2/asm/bitops.h:59: warning: asm operand 1 probably doesn't match constraints
include2/asm/bitops.h:59: error: impossible constraint in `asm'
include2/asm/bitops.h:59: error: impossible constraint in `asm'
include2/asm/bitops.h:59: error: impossible constraint in `asm'

Reported-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/asm-x86/bitops.h b/include/asm-x86/bitops.h
index 6c5054819719faf448642f93c76e05df3b3b48ca..96b1829cea15aa0fbc00177e394a9bab47a5a5b7 100644 (file)
--- a/include/asm-x86/bitops.h
+++ b/include/asm-x86/bitops.h
@@ -58,7 +58,7 @@ static inline void set_bit(unsigned int nr, volatile unsigned long *addr)
        if (IS_IMMEDIATE(nr)) {
                asm volatile(LOCK_PREFIX "orb %1,%0"
                        : CONST_MASK_ADDR(nr, addr)
-                       : "i" (CONST_MASK(nr))
+                       : "iq" ((u8)CONST_MASK(nr))
                        : "memory");
        } else {
                asm volatile(LOCK_PREFIX "bts %1,%0"
@@ -95,7 +95,7 @@ static inline void clear_bit(int nr, volatile unsigned long *addr)
        if (IS_IMMEDIATE(nr)) {
                asm volatile(LOCK_PREFIX "andb %1,%0"
                        : CONST_MASK_ADDR(nr, addr)
-                       : "i" (~CONST_MASK(nr)));
+                       : "iq" ((u8)~CONST_MASK(nr)));
        } else {
                asm volatile(LOCK_PREFIX "btr %1,%0"
                        : BITOP_ADDR(addr)